Infrared Proximity Detector Alarm

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This circuit can be built from readily available low-cost components. The indicated value of 22 Ω for resistor R1 causes an average current of about 65 mA through infrared emitter D1. Because the IRED is pulsed at a duty factor of about 50% through the action of T1 and IC1, a peak current of 128 mA flows during every half cycle. This may seem a lot but in fact is well within the safe specification of the LD274. The LM567 PLL IC is configured to supply a switching frequency of about 20 kHz. When the infrared beam emitted by D1 is reflected by a nearby object, IC1, through receiver diode D2 and transistor T2, receives the recovered 20 kHz signal at its input, pin 3.</div> <div style="text-align: justify;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2Y-daoaTLjcVdRcaf2Yog2skUJGZ0bDI7kmNMBT9VeYZW1uVR1-Scttl5IbPhT-wu2qtpYSZaa9MYdMUbE_QJWTKS_MKFdaRq8hVKBz-7oz9SQy9BYYmHWXfG4ZW3LqvpDZOK2RYC1JP0/s1600/infrared_proximity_detector_alarm_circuit_diagram.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Infrared Proximity Detector Alarm" border="0" height="551" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2Y-daoaTLjcVdRcaf2Yog2skUJGZ0bDI7kmNMBT9VeYZW1uVR1-Scttl5IbPhT-wu2qtpYSZaa9MYdMUbE_QJWTKS_MKFdaRq8hVKBz-7oz9SQy9BYYmHWXfG4ZW3LqvpDZOK2RYC1JP0/s640/infrared_proximity_detector_alarm_circuit_diagram.gif" title="Infrared Proximity Detector Alarm" width="640" /></a></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> Because the ‘567 PLL is then locked, the IC output (pin 8), drops low, triggering the 555 chip in monostable mode (IC2) and so causing acoustic actuator Bz1 to sound. The monostable remains on as long as the reflected signal is being received. Because of the presence of T3, capacitor C5 is allowed to charge only when no signal is being received. In that condition, the 555 is turned off automatically after a time determined by R9-C5. Using the component values shown, this will be about 5 seconds. Obviously D1 and D2 should be mounted such that the latter can only pick up reflected infrared light.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> The choice of the two infrared components used in this circuit will be uncritical but they must be ‘band’ compatible, i.e., generate (D1) and respond to (D2) the same wavelength. The operating point of the receiver input circuit is rather dependent on ambient day-light levels and the value of R4 may need to be adjusted a little to ensure a voltage of between 1.5 V and 4 V on the collector of T1 when no signal is being received. Some dc buzzers cause a lot of back-emf so it may be necessary to insert a diode in series with the output of IC1. If necessary, this diode should preferably be a Schottky type because of the inherent low voltage drop of about 0.4 V as opposed to 0.65 V for a typical small-signal silicon diode.</div> </div>

Infrared Proximity Detector Alarm

This circuit can be built from readily available low-cost components. The indicated value of 22 Ω for resistor R1 causes an average curren...

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Sensor Circuits

<div dir="ltr" style="text-align: left;" trbidi="on"> <div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> <b>Sensor Circuits/Projects/Schematics:</b><br /> <ol> <li><a href="http://www.ecestream.com/2015/05/infrared-proximity-detector-sensor-alarm-circuit.html">Infrared Proximity Detector</a></li> <li><a href="http://www.ecestream.com/2015/04/temperature-sensor-circuit.html">Temperature Sensor</a></li> <li><a href="http://www.ecestream.com/2015/04/heat-sensor-circuit.html">Heat Sensor</a></li> <li><a href="http://www.ecestream.com/2015/03/sound-level-indicator-detector-sensor.html">Sound Level Indicator</a></li> <li><a href="http://www.ecestream.com/2015/03/dark-sensor-using-transistor.html">Dark Sensor</a></li> <li><a href="http://www.ecestream.com/2015/03/automatic-dark-sensor.html">Automatic Dark Sensor</a></li> <li><a href="http://www.ecestream.com/2015/03/color-detector-circuit.html">Color Detector Circuit</a></li> <li><a href="http://www.ecestream.com/2014/12/infrared-detector-circuit.html">Infrared Detector Circuit</a></li> <li><a href="http://www.ecestream.com/2014/12/ir-infrared-detector-circuit.html">IR Infrared Detector Circuit</a></li> <li><a href="http://www.ecestream.com/2014/11/sensitive-optical-burglar-alarm.html">Sensitive Optical Burglar Alarm</a></li> <li><a href="http://www.ecestream.com/2014/11/light-detector-circuit.html">Light Detector Circuit</a></li> <li><a href="http://www.ecestream.com/2014/11/gas-leak-detector-circuit.html">Gas Leak Detector Circuit</a></li> <li><a href="http://www.ecestream.com/2014/11/infrared-ir-sensor-detector-circuit.html">Infrared (IR) Sensor / Detector Circuit</a></li> <li><a href="http://www.ecestream.com/2014/11/motion-detector-circuit.html">Motion Detector Circuit</a></li> <li><a href="http://www.ecestream.com/2014/11/simple-photoelectric-detector-circuit.html">Simple Photoelectric Detector Circuit</a></li> <li><a href="http://www.ecestream.com/2014/10/metal-detector-circuit.html">Metal Detector Circuit</a></li> <li><a href="http://www.ecestream.com/2014/05/sensitive-intruder-alarm-circuit.html">Sensitive Intruder Alarm Circuit</a></li> </ol> </div> </div> <hr style="text-align: justify;" /> <div style="text-align: justify;"> <b>Sensor Tutorials:</b></div> <div style="text-align: justify;"> </div> <ol> <li><a href="http://www.ecestream.com/2014/11/sensor.html">Sensor</a></li> <li><a href="http://www.ecestream.com/2014/11/photoswitchphotoelectric-sensors.html">Photoswitch/Photoelectric Sensors</a></li> <li><a href="http://www.ecestream.com/2014/11/inductive-proximity-sensors_25.html">Inductive Proximity Sensors</a></li> <li><a href="http://www.ecestream.com/2014/11/ultrasonic-proximity-sensor.html">Ultrasonic Proximity Sensor</a></li> <li><a href="http://www.ecestream.com/2014/11/capacitive-proximity-sensors.html">Capacitive Proximity Sensors</a></li> </ol> <hr style="text-align: justify;" /> <div class="separator" style="clear: both; text-align: center;"> <img alt="PIR Motion Sensor" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg1nwc3gELQNl_F74YPbQhBGXGX3IZaDZTQXFtbEHYLDTIRVu3vGJkucbFLVynkmtkpXJvZtODSE6PzGpp8O11rt5p3J-R4kfEDSVBanrP4dX6j8jsRUpe6HF2hxQKzDHtblMxwAIkmpPuk/s1600/PIR_motion_sensor.jpg" title="PIR Motion Sensor" /></div> </div>

Sensor Circuits

Sensor Circuits/Projects/Schematics: Infrared Proximity Detector Temperature Sensor Heat Sensor Sound Level Indicator Dark Sensor ...

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Temperature Sensor

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This project uses IC LM35 as a sensor for detecting accurate centigrade temperature. Linearity defines how well over a range of temperature a sensor’s output consistently changes. Unlike thermistor, Linearity of a precision IC Sensors are very good of 0.5°C accuracy and has wide temperature range. its output voltage is linearly proportional to the Celsius (Centigrade) temperature.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> The LM35 is rated to operate over a -55° to +150°C temperature range.It draws only 60 µA from its supply, it has very low self-heating, less than 0.1°C in still air. LM35 Operates from 4 to 30 volts.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> Output of IC is 10mv/degree centigrade for eg if the output of sensor is 280 mV then temperature is 28 degree C. so by using a Digital multimeter we can easily calculate the degree temperature. For trigger point you should set the voltage of pin 2 of IC 741 by using preset or potentiometer.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> Our aim of this project is not to construct a thermometer but to activate or deactivate a device at a particular margin temperature. For simplicity we have used 2 LED for indication  of both low (Green) and high (Red) temperature.</div> <div class="separator" style="clear: both; text-align: center;"> <img alt="Temperature Sensor" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRUbRXLu5NVNI-dGp8ovGYykEELV-ASLIQ_dqGBcE1QA1X-d7BpFMAe3gLo_P6Ny0tYGCZtX4jEisrxb153GR3j31ZmVihNic7Ln58aIUJSP1ZVhFv8F-Qp2SEa7MIR9sutY84hL5gqHC5/s1600/temperature+sensor.gif" title="Temperature Sensor Circuit" /></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> Working: The output of IC2 increases in proportion to the temperature by 10 mV per degree. This varying voltage is feed to a comparator IC 741 (OP Amplifier). OP Amplifier are among the most widely used electronic devices today.The op-amp is one type of differential amplifier. It has two input inverting (-) and non-inverting (+) and one output pin. We have used IC741 as non-inverting amplifier which means pin 3 is the input and the output is not reversed. This circuit amplifies the difference between its input terminals.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> As a comparator, Bistable output of an op amplifier is as follows:</div> <div style="text-align: justify;"> <br /></div> <div class="separator" style="clear: both; text-align: left;"> <img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyR0gwnF1dl4MKqkUzUTcLnRPJ0fIsZxseDcv46KW6u1tUBXSgEEVFeypZzl6f3cVxE-zYWoH28cNHta9gETVaoyTf84BrteBcAhBdWCOcbfPCljSi7ywPVB67sVFIH_DZpc7GC09NqPEl/s1600/comparator+formula.png" /></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>Part list:</b></div> <div style="text-align: justify;"> </div> <ol> <li>IC LM35, IC LM741</li> <li>Resistance: 10K Ohms, 470 Ohms X 2Pcs</li> <li>Preset or P.O.T of 2K Ohms</li> <li>LED 2pcs (Red and Green)</li> <li>9V Battery with Snap</li> <li>Switch, wire</li> </ol> </div>

Temperature Sensor

This project uses IC LM35 as a sensor for detecting accurate centigrade temperature. Linearity defines how well over a range of temperatur...

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Heat Sensor

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> Here is a simple circuit which can be used as a heat sensor. In the following circuit diagram thermistor and 100 Ohms resistance is connected in series and makes a potential divider circuit . If thermistor is of N.T.C (Negative temperature Coefficient ) type then after heating the thermistor its resistance decreases so more current flows through the thermistor and 100 Ohms resistance and we get more voltage at junction of thermistor and resistance. Suppose after heating 110 ohms thermistor its resistance value become 90 Ohms.then according to potential divider circuit the voltage across one resistor equals the ratio of that resistor’s value and the sum of resistances times the voltage across the series combination. This concept is so pervasive it has a name: voltage divider. The input-output relationship for this system, found in this particular case by voltage divider, takes the form of a ratio of the output voltage to the input voltage.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> This output voltage is applied to a NPN transistor through a resistance. Emitter voltage is maintain at 4.7 volt with a help of Zener diode.This voltage we will use as compare voltage. Transistor conducts when base voltage is greater than emitter voltage. Transistor conducts as it gets more than 4.7 base Voltage and circuit is completed through buzzer and it gives Sound.<br /> <br /> <div class="separator" style="clear: both; text-align: center;"> <img alt="Heat Sensor" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirx_Z55Mlz9YEJ0Z5si_kAXLS_vEA8KBLyHLNLfHgRYpsdYTkKuYfV_jITzfwHFKtkeJDNE7yS1Z_JAIXizBRZPMhA8Q0-HsFkNb3iDS3pKmGt6uf5Q7JzAd3iNyskwegbz-67w729yZF0/s1600/heat_sensor.jpg" title="Heat Sensor Circuit" /></div> <br /> <b>Note:</b> Please use 220 Ohms thermistor if not available you can use 2pcs 110 ohms thermistor in series. Resistance parallel with zener diode is not necessary.</div> </div>

Heat Sensor

Here is a simple circuit which can be used as a heat sensor. In the following circuit diagram thermistor and 100 Ohms resistance is connec...

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Sound Level Indicator

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This circuit uses an LM3915 bar-graph IC driving two sets of ten LEDs for a 30dB range. The circuit is unique because it has an additional range of 20dB provided by an automatic gain control to allow it to be very sensitive to low sound levels but it increases its range 20dB for loud sounds.</div> <div style="text-align: justify;"> </div> <div style="text-align: justify;"> The LEDs are operating at 26mA each with the brightness control at maximum, which is very bright. The circuit has a switch to select the modes of operation: a moving dot of light, or a bar with a changing length.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> My prototype has a little 9V Ni-Cad rechargeable battery in it to be portable and the battery is trickle-charged when the project is powered by a 9V AC-DC adapter.<br /> <br /></div> <div style="text-align: justify;"> </div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6FAuBfJxbqGGSBgsokLAeoG7dB8gVVPZL9vppGA2A7VNqETQp-HlTuimZjhdrFsJWA4nv2nuvDkrVg2IQOVT0YrN-2cAvB35kOPnr2L1tgn2BxxfL8rylwRzl8aXTO4-ebfmZz0ADyv0l/s1600/Sound+Level+Indicator.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Sound Level Indicator Circuit" border="0" height="340" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6FAuBfJxbqGGSBgsokLAeoG7dB8gVVPZL9vppGA2A7VNqETQp-HlTuimZjhdrFsJWA4nv2nuvDkrVg2IQOVT0YrN-2cAvB35kOPnr2L1tgn2BxxfL8rylwRzl8aXTO4-ebfmZz0ADyv0l/s1600/Sound+Level+Indicator.PNG" title="Sound Level Indicator" width="400" /></a></div> <div class="separator" style="clear: both; text-align: center;"> <strong><em>Figure: Sound Level Indicator</em></strong></div> <div style="text-align: justify;"> </div> <div style="text-align: justify;"> </div> <div style="text-align: justify;"> <br /> <strong><span style="color: #3d85c6;">Circuit Description</span></strong></div> <div style="text-align: justify;"> </div> <div style="text-align: justify;"> <br /> <strong>1.</strong> The electret microphone is powered by and has a load of R1 from an LM2931 5V low-dropout regulator.<br /> <br /></div> <div style="text-align: justify;"> </div> <div style="text-align: justify;"> <strong>2.</strong> The 1st opamp stage is an audio preamp with a gain of 101.<br /> <br /></div> <div style="text-align: justify;"> </div> <div style="text-align: justify;"> <strong>3.</strong> The 2nd opamp stage is a single-supply opamp which works fine with its inputs and output at ground and is used as a rectifier driver with a gain of 1.8. It is biased at ground. Since it is inverting, when its input swings negative, its output swings positive.<br /> <br /></div> <div style="text-align: justify;"> </div> <div style="text-align: justify;"> <strong>4.</strong> Three 2N3904 transistors are used as emitter-followers:</div> <ul style="text-align: left;"> <li><div style="text-align: justify;"> Q1 is inside the negative feedback loop of the 2nd opamp as a voltage reference for the other two transistors. Hopefully the transistors match each other.</div> </li> <div style="text-align: justify;"> </div> <li><div style="text-align: justify;"> Q2 emitter-follower transistor quickly charges C8 which discharges slower into R13 and is used as a peak detector.</div> </li> <div style="text-align: justify;"> </div> <li><div style="text-align: justify;"> Q3 transistor is the automatic gain control. It is also a peak detector but has slower charge and discharge times. It drives the comparators’ resistor ladder in the LM3915 to determine how sensitive it is. R15 from +5V is in a voltage divider with the ladder’s total resistance of about 25k and provides the top of the ladder with about +0.51V when there is a very low sound level detected. Loud sounds cause Q3 to drive the top of the ladder to 5.1V for reduced sensitivity.</div> </li> </ul> <div style="text-align: justify;"> <strong>5.</strong> The LM3915 regulates the current for the LEDs so they don’t need current-limiting resistors. In the bar mode with all LEDs lit then the LM3915 gets hot so the 10 ohm/1W resistor R16 shares the heat.<br /> <br /></div> <div style="text-align: justify;"> </div> <div style="text-align: justify;"> <strong><span style="color: #3d85c6;">Options</span></strong></div> <ol style="text-align: left;"> <li><div style="text-align: justify;"> You could use a switch to change the brightness instead of a pot, or leave it bright.</div> </li> <div style="text-align: justify;"> </div> <li><div style="text-align: justify;"> You could use an LM358 dual opamp (I tried it) but its output drops above 4Khz. The MC33172 is flat to 20kHz with this high gain.</div> </li> <div style="text-align: justify;"> </div> <li><div style="text-align: justify;"> You could add a 1uF to 2.2uF capacitor across R5 so the indicator responds only to bass or “the beat” of music. Then an LM358 dual opamp is fine.</div> </li> </ol> <div style="text-align: justify;"> <strong><span style="color: #3d85c6;">Parts List</span></strong> </div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> R1--10k </div> <div style="text-align: justify;"> R2, R3, R5, R7, R8, R10--100k</div> <div style="text-align: justify;"> R4--47k</div> <div style="text-align: justify;"> R6--1k</div> <div style="text-align: justify;"> R9--56k</div> <div style="text-align: justify;"> R11--4.7k</div> <div style="text-align: justify;"> R12, R14--100</div> <div style="text-align: justify;"> R13--330k</div> <div style="text-align: justify;"> R15--220k</div> <div style="text-align: justify;"> R16--10/1W</div> <div style="text-align: justify;"> R17, R19--390</div> <div style="text-align: justify;"> R18--22k</div> <div style="text-align: justify;"> P1--10k audio-taper (log) pot</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> C1, C4, C8--330nF</div> <div style="text-align: justify;"> C2--47uF/10V</div> <div style="text-align: justify;"> C3, C9--100uF/10V</div> <div style="text-align: justify;"> C5--100nF</div> <div style="text-align: justify;"> C6--470uF/16V</div> <div style="text-align: justify;"> C7--10uF/16V </div> <div style="text-align: justify;"> IC1--MC33172P</div> <div style="text-align: justify;"> IC2--LM3915P</div> <div style="text-align: justify;"> 5V reg--LM2931AZ5.0</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> LEDs--MV8191 super-red diffused</div> <div style="text-align: justify;"> Electret microphone--two-wire type Box--Hammond 1591B</div> <div style="text-align: justify;"> Battery--9V Ni-Cad or Ni-MH</div> <div style="text-align: justify;"> SW1--SPST switch</div> <div style="text-align: justify;"> Adapter jack--switched</div> </div>

Sound Level Indicator

This circuit uses an LM3915 bar-graph IC driving two sets of ten LEDs for a 30dB range. The circuit is unique because it has an additional...

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Dark Sensor using Transistor, Phototransistor and Photodiode

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This versatile dark sensor is made up of two <a href="http://www.ecestream.com/2014/12/bipolar-junction-transistors-bjts.html" target="_blank">transistors</a>. It is a versatile module, because you can use it for testing several electronic components, such as, relay, reed switch, light dependent <a href="http://www.ecestream.com/2014/11/resistor.html" target="_blank">resistor</a> (LDR), electret microphone, phototransistor, <a href="http://www.ecestream.com/2014/11/photodiodes.html" target="_blank">photodiode</a>, etc. Besides, you can use this module for making simple clap switch, light operated switch, water level indicator, etc.</div> <div style="text-align: justify;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <img alt="Dark-Sensor-using-Transistor-Phototransistor-and-Photodiode-ecestream" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmLdlbHC6PYiienduNkbqCuOuGkeSePmHXhmOnc8Pfl2ztG6rmOU1x2xvC7IW_P8rIbyLG04TlSuhYe0-yhCtDpK7dWkTueesSvHzwtB2-k1jnwEE94lealMsZAu79szGPtPAOfCCZJHUe/s1600/Dark+Sensor+using+Transistor,+Phototransistor+and+Photodiode.jpg" title="Dark Sensor using Transistor, Phototransistor and Photodiode" /></div> <div class="separator" style="clear: both; text-align: center;"> <b><i>Dark Sensor Circuit</i></b></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> When you block the light falling on LDR, the transistor Q1 switches off and transistor Q2 switches on, that drives the <a href="http://www.ecestream.com/2014/11/light-emitting-diodes-leds.html" target="_blank">LED</a> D1. Change the value of R3 to change its sensitivity.</div> </div>

Dark Sensor using Transistor, Phototransistor and Photodiode

This versatile dark sensor is made up of two transistors . It is a versatile module, because you can use it for testing several electronic...

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Automatic Dark Sensor

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This circuit has been configured in <a href="http://www.ecestream.com/2014/12/the-555-as-astable-multivibrator_9.html" target="_blank">Astable mode</a>. The output pulses are determined by the values of <a href="http://www.ecestream.com/2014/11/resistor.html" target="_blank">resistors</a> R1, R2 and the timing <a href="http://www.ecestream.com/2014/11/capacitor.html" target="_blank">capacitor</a> C1.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> Automatic blinker comprises two modules. First is the dark detector circuit and the other is a multivibrator configured in astable mode of operation. When there is enough darkness on LDR, <a href="http://www.ecestream.com/2014/11/the-555-timer.html" target="_blank">555</a> gets power from the emitter of <a href="http://www.ecestream.com/2014/12/bipolar-junction-transistors-bjts.html" target="_blank">transistor</a> Q2 and <a href="http://www.ecestream.com/2014/11/light-emitting-diodes-leds.html" target="_blank">LED</a> D1 starts blinking.</div> <div style="text-align: justify;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9INBkuTjLF0PpQIkovPuKwyFFld9hfAlRAOCT6cHZc2sDQenZQzLhXCJlD5rwa_W9Jd-OJWrbSxDuZxlr88ynnjfWguGAPYS3B0DjuRfGHVfr8bOva50MfYN3zZseFkexsAuqcz0Hdhyphenhyphen-/s1600/Automatic-Blinker1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Automatic-Dark-Sensor-Circuit-ecestream" border="0" height="236" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9INBkuTjLF0PpQIkovPuKwyFFld9hfAlRAOCT6cHZc2sDQenZQzLhXCJlD5rwa_W9Jd-OJWrbSxDuZxlr88ynnjfWguGAPYS3B0DjuRfGHVfr8bOva50MfYN3zZseFkexsAuqcz0Hdhyphenhyphen-/s1600/Automatic-Blinker1.jpg" title="Automatic Dark Sensor Circuit" width="640" /></a></div> <div class="separator" style="clear: both; text-align: center;"> <b><i>Automatic Dark Sensor Circuit</i></b></div> </div>

Automatic Dark Sensor

This circuit has been configured in Astable mode . The output pulses are determined by the values of resistors R1, R2 and the timing capa...

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Color Detector Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This is the color detector / <a href="http://www.ecestream.com/2014/11/sensor.html" target="_blank">sensor</a> circuit diagram. This circuit will sense eight colors that are: green, red and blue (as primary colours); magenta, cyan and yellow (as secondary colours); and black and white. It’s will be very useful for robotics project.</div> <div style="text-align: justify;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkR2OUYNolqB8iUi9_lRiH721bDMjAU2nNaKEWalxtuQhKb20z6JKi3h4b3F8YrVpFHwMDZdctLyd9QUiPxF9lR9_WXYFgajjfT6dHnskd_ICX0tiSI3hPAq6BlV5NA7FWZtp_6wTycVxL/s1600/Color-Detector-Circuit.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Color Detector Circuit-ecestream" border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkR2OUYNolqB8iUi9_lRiH721bDMjAU2nNaKEWalxtuQhKb20z6JKi3h4b3F8YrVpFHwMDZdctLyd9QUiPxF9lR9_WXYFgajjfT6dHnskd_ICX0tiSI3hPAq6BlV5NA7FWZtp_6wTycVxL/s1600/Color-Detector-Circuit.png" title="Color Detector Circuit" width="400" /></a></div> <div class="separator" style="clear: both; text-align: center;"> <b><i>Figure: Color Detector Circuit</i></b></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> The circuit is based on the fundamentals of optics and digital electronics. The object whose colour is required to be detected should be placed in front of the system. The light rays reflected from the object will fall on the three convex lenses which are fixed in front of the three LDRs. The convex lenses are used to converge light rays. This helps to increase the sensitivity of LDRs. Blue, green and red glass plates (filters) are fixed in front of LDR1, LDR2 and LDR3 respectively. When reflected light rays from the object fall on the gadget, the coloured filter glass plates determine which of the LDRs would get triggered.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> The circuit makes use of only ‘AND’ gates and ‘NOT’ <a href="http://www.ecestream.com/2014/11/logic-gates.html" target="_blank">gates</a>. When a primary coloured light ray falls on the system, the glass plate corresponding to that primary colour will allow that specific light to pass through. But the other two glass plates will not allow any light to pass through. Thus only one LDR will get triggered and the gate output corresponding to that LDR will become logic 1 to indicate which colour it is. Similarly, when a secondary coloured light ray falls on the system, the two primary glass plates corresponding to the mixed colour will allow that light to pass through while the remaining one will not allow any light ray to pass through it. As a result two of the LDRs get triggered and the gate output corresponding to these will become logic 1 and indicate which colour it is.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> When all the LDRs get triggered or remain untriggered, you will observe white and black light indications respectively. Following points may be carefully noted :</div> <div style="text-align: justify;"> </div> <ol> <li>Potentiometers VR1, VR2 and VR3 may be used to adjust the sensitivity of the LDRs.</li> <li>Common ends of the LDRs should be connected to positive supply.</li> <li>Use good quality light filters.</li> </ol> <br /> <div style="text-align: justify;"> The LDR is mounted in a tube, behind a lens, and aimed at the object. The coloured glass filter should be fixed in front of the LDR as shown in the figure. Make three of that kind and fix them in a suitable case. Adjustments are critical and the gadget performance would depend upon its proper fabrication and use of correct filters as well as light conditions.</div> </div>

Color Detector Circuit

This is the color detector / sensor circuit diagram. This circuit will sense eight colors that are: green, red and blue (as primary colou...

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Infrared Detector Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This <i><u>infrared detector circuit</u></i> uses a passive IR-detector component PID20. It converts heat radiation into electrical impulses. The output voltage of the PID20 increases when an object comes close to it, this object must be warmer than the surroundings.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> The voltage changes at the output of the IR sensor are sensed by the comparators IC2A and IC2B. Once the sensor detects an object (independent of the object’s actual temperature), one of the comparators will turn on the transistor T1. This transistor then closes the relay connected to it. A separate transistor for each comparator can be used so that the sensor will be able to determine whether the object is warmer or colder than the surroundings. The IR detector circuit consumes around 1 mA and the sensor consumes 0.2 mA.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>IR Detector Circuit</b></div> <div style="text-align: justify;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZb2JN9D3_9kiJMpDyDQmmwFaJqzE_NhC2zdikQmEdu9ode0KG1PTMHW7wCCetuAfOG2SYrlO0Ii-8EqgaLjkirfM-yVPH1kwH1XR2Ne0N2-gai_DXAsnm9QuTAArQAkzAfRXJgqO6TJHI/s1600/infrared-detector-circuit.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZb2JN9D3_9kiJMpDyDQmmwFaJqzE_NhC2zdikQmEdu9ode0KG1PTMHW7wCCetuAfOG2SYrlO0Ii-8EqgaLjkirfM-yVPH1kwH1XR2Ne0N2-gai_DXAsnm9QuTAArQAkzAfRXJgqO6TJHI/s1600/infrared-detector-circuit.jpg" /></a></div> <div style="text-align: justify;"> <br /></div> </div>

Infrared Detector Circuit

This infrared detector circuit uses a passive IR-detector component PID20. It converts heat radiation into electrical impulses. The outpu...

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IR Infrared Detector Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This <u>infrared detector</u> can be used to detect the presence of modulated infrared signals in its vicinity from any electronic source, for instance, an IR handheld remote controller. It can also be used for testing infrared burglar alarm systems. This is not an infrared motion detector.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> The <i>IR detector circuit</i> in principle, converts the IR signal pulse trains into noticeable aural notes. S1 is used to switch on/off mains power and LED1 indicates power-on. Resistor R4 and zener diode ZD2 form a low-current voltage stabiliser for providing steady 5.1 V DC to the small signal preamplifier circuit. IR LED1 is the main sensing element.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> The infrared signal detected by IR LED1 is amplified by npn transistors T1 and T2. The amplified signal is fed to the melody generator via resistor R5. The output of the melody generator UM66 is fed to LM386 low-power audio amplifier (IC2) via variable resistor VR1, which works as the volume control. The loudspeaker sounds to indicate the presence of IR signal near the circuit.</div> <div style="text-align: justify;"> <br /> <b>IR Detector Circuit</b><br /> <b><br /></b> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiULy4_QBNLjAjkKW1UxYLXwyoqq7BBC9Le1hq8jN715gWlJh6hTVQmEsPs2tfnOWYgGSiWu9FQEHucP0QzFVH3PspQqKESI00NEo2Ab3CnvfPAIG1Fwuhu7e1vyvRYlm4cuEXSbtU1fSmt/s1600/IR+Infrared-Detector.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="438" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiULy4_QBNLjAjkKW1UxYLXwyoqq7BBC9Le1hq8jN715gWlJh6hTVQmEsPs2tfnOWYgGSiWu9FQEHucP0QzFVH3PspQqKESI00NEo2Ab3CnvfPAIG1Fwuhu7e1vyvRYlm4cuEXSbtU1fSmt/s1600/IR+Infrared-Detector.png" width="640" /></a></div> <br /></div> <div style="text-align: justify;"> The infrared detector circuit can be easily wired on a small veroboard or any general-purpose printed circuit board.</div> <div style="text-align: justify;"> Pin configurations of IC LM386, transistor BC547 and melody generator UM66.<br /> <br /> <div class="separator" style="clear: both; text-align: center;"> <img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgR9kYpEFVUM02DxT6YA7BE5FqlpQlqmwvbEcTyrsYBI36rJWi0fsWsVnL_TH-KIbBGMjPpIr4-0E7AuDE1iA643V40Sss5_BmhKGgpA9VqjVxVRj3oGqhZKLkg4V_m8PKyImYJXzciEY7L/s1600/um66-pin-configurations.png" /></div> </div> </div>

IR Infrared Detector Circuit

This infrared detector can be used to detect the presence of modulated infrared signals in its vicinity from any electronic source, for i...

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Infrared (IR) Sensor / Detector Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> <span style="font-family: inherit;">The circuit shows that the output of IC1 555 IC, which is designed for a duty cycle of 0.8 mSec, with a frequency of 120 Hz and 300 mA peak current, is used to drive the infrared LED, D1. From the connection it is clear that the diodes D1 and D2 are on the same line, just a few centimeters apart, on the breadboard. Thus diode D2 receives the infra-red output from the diode D1. The diode signal, which is given to the inverting terminal of the op-amp IC LM358 gets amplified and its peak is detected by diode D4 and capacitor C4. The forward voltage produced by diode D4 is compensated by diode D3 with R5 and R6. According to the distance between the infra-red transmitter and receiver, a proportional DC voltage is fed to the inverting input of IC2. According to the output of the comparator the LED is turned ON and OFF and this is detected by the transistor Q1. Thus the relay is driven according to the output of Q1. The comparator output is set according to the value of the pot.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;">This circuit is mainly used for liquid level detection or proximity detection. It operates detecting the distance from the target by reflection of an infra-red beam. The biggest advantage of this circuit is that there is no physical contact with the liquid whose level is to be measured. The range is set by adjusting the pot. Range can vary, depending on infra-red transmitting and receiving LEDs used and is mostly affected by the color of the reflecting surface. Black surfaces lower greatly the device’s sensitivity.</span><br /> <span style="font-family: inherit;"><br /></span> <span style="font-family: inherit;"><b>Schematic</b></span><br /> <div class="separator" style="clear: both; text-align: justify;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiHYVuq_iPBd0dDZs9YPWrDHAV96deYJbS3TgrvZifTs-ttDOZQJ8nG39A1g1Rh_YqfeAzHMtkpGciIpVKVhKaqXKk-061NT0jv-SaOlpJCVn459AXJpe-Ewu1CcIqBgZrp97c7hS1ofxxM/s1600/IR-Level-Detector.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="314" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiHYVuq_iPBd0dDZs9YPWrDHAV96deYJbS3TgrvZifTs-ttDOZQJ8nG39A1g1Rh_YqfeAzHMtkpGciIpVKVhKaqXKk-061NT0jv-SaOlpJCVn459AXJpe-Ewu1CcIqBgZrp97c7hS1ofxxM/s1600/IR-Level-Detector.png" width="640" /></a></div> <span style="font-family: inherit;"><b><br /></b></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Notes</b></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;">Use a good quality regulated power supply. The sensor diodes must not be subjected directly to other light sources.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Parts List </b></span></div> <div style="text-align: justify;"> </div> <ul> <li><span style="font-family: inherit;">Resistance R1 = 10K(4W)</span></li> <li><span style="font-family: inherit;">Resistance R2, R5, R6, R9 = 1K(4W)</span></li> <li><span style="font-family: inherit;">Resistance R3 = 33R(4W)</span></li> <li><span style="font-family: inherit;">Resistance R4, R8 = 1M(4W)</span></li> <li><span style="font-family: inherit;">Trimmer Cermet R7 = 10K</span></li> <li><span style="font-family: inherit;">Resistance R10 = 22K(4W)</span></li> <li><span style="font-family: inherit;">Capacitance C1, C4 = 1 uF(63V)</span></li> <li><span style="font-family: inherit;">Capacitance C2 = 47pF(63V)</span></li> <li><span style="font-family: inherit;">Capacitance C3, C5, C6 = 100uF(25V)</span></li> <li><span style="font-family: inherit;">Diode D1 = IR LED</span></li> <li><span style="font-family: inherit;">Diode D2 = IR Photo-Diode</span></li> <li><span style="font-family: inherit;">Diode D3, D4 = 1N4148(75W/150mA)</span></li> <li><span style="font-family: inherit;">Diode D5 = LED</span></li> <li><span style="font-family: inherit;">Diode D6, D7 = 1N4002</span></li> <li><span style="font-family: inherit;">PNP Transistor Q1 = BC558(45V/800mA)</span></li> <li><span style="font-family: inherit;">Timer IC IC1 = NE555</span></li> <li><span style="font-family: inherit;">IC 2 = LM358</span></li> <li><span style="font-family: inherit;">IC 3 = 7812</span></li> <li><span style="font-family: inherit;">Relay = SPDT(2A/220V)</span></li> <li><span style="font-family: inherit;">J1 = Two ways output socket</span></li> </ul> </div>

Infrared (IR) Sensor / Detector Circuit

The circuit shows that the output of IC1 555 IC, which is designed for a duty cycle of 0.8 mSec, with a frequency of 120 Hz and 300 mA pea...

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Sensitive Optical Burglar Alarm

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This optical burglar alarm uses two 555 timer ICs (IC1 and IC2). Both the ICs are wired as astable multivibrators. The first astable multivibrator built around IC1 produces low frequencies, while the second astable multivibrator built around IC2 produces audio frequencies. General-purpose Darlington photo-transistor T1 is used as the light sensor. To increase the sensitivity of the circuit, NPN transistor T2 is used.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> Place phototransistor T1 where light falls on it continuously. Phototransistor T1 receives light to provide base voltage to transistor T2. As a result, transistor T2 conduct to keep reset pin 4 of IC1 at low level. This disables the first multivibrator (IC1) and hence the second multivibrator (IC2) also remains reset so the alarm (LS1) does not sound.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>Circuit Diagram</b></div> <div style="text-align: justify;"> <b><br /></b></div> <div style="text-align: center;"> <img height="352" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXpsTNj7wBRBzK1i3BYR0TfdEJy9bY4kaPleSPVPix1fgrEXMM_T0qnNpGvpbhp1wRBhDQ9gwN5hyphenhyphenBavZX4Mwb5-5aeo1g8y_oxQfCpUPE66ShqXrbhI9CS1mVxaZOxNjlHtQ-G_jIWP4s/s1600/SENSITIVE+OPTICAL+BURGLAR+ALARM.jpg" width="640" /></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> When light falling on Darlington phototransistor T1 is obstructed, transistor T2 stops conducting and reset pin 4 of IC1 goes high. This enables the first multivibrator (IC1) and hence also the second multivibrator (IC2). As a result, a beep tone is heard from speaker LS1. The beep rate can be varied by using preset VR1, while the output frequency of IC2 can be varied by using another preset VR2.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> This circuit works off a simple 6V-12V DC power supply.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>Parts List</b></div> <div style="text-align: justify;"> <ul> <li><b>Resistors (all ¼-watt, ± 5% Carbon unless stated otherwise)</b></li> </ul> </div> <div style="text-align: justify;"> <ol> <li>R1, R5 = 1 KΩ</li> <li>R2 = 100 KΩ</li> <li>R3 = 4.7 KΩ</li> <li>R4 = 10 KΩ</li> <li>VR1 = 1 MΩ</li> <li>VR2 = 100 KΩ</li> </ol> </div> <div style="text-align: justify;"> <ul> <li><b>Capacitors</b></li> </ul> </div> <div style="text-align: justify;"> <ol> <li>C1 = 1 µF/16V</li> <li>C2 = 0.01 µF</li> <li>C3 = 0.047 µF</li> <li>C4 = 0.01 µF</li> <li>C5 = 47 µF/25V</li> </ol> </div> <div style="text-align: justify;"> <ul> <li><b>Semiconductors</b></li> </ul> </div> <div style="text-align: justify;"> <ol> <li>IC1, IC2 = NE555</li> <li>T1 = 2N5777 Photo Transistor</li> <li>T2 = BC547</li> <li>LED1 = RED LED</li> </ol> </div> <div style="text-align: justify;"> <ul> <li><b>Miscellaneous</b></li> </ul> </div> <div style="text-align: justify;"> <ol> <li>LS1 = 8Ω / 0.5W</li> </ol> </div> </div> <!-- Blogger automated replacement: "https://images-blogger-opensocial.googleusercontent.com/gadgets/proxy?url=http%3A%2F%2F2.bp.blogspot.com%2F-rZTa4Hz3d7Q%2FU4xRETYqtoI%2FAAAAAAAAAXY%2FtF-W8pnEe8Y%2Fs1600%2FSENSITIVE%2BOPTICAL%2BBURGLAR%2BALARM.jpg&container=blogger&gadget=a&rewriteMime=image%2F*" with "https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXpsTNj7wBRBzK1i3BYR0TfdEJy9bY4kaPleSPVPix1fgrEXMM_T0qnNpGvpbhp1wRBhDQ9gwN5hyphenhyphenBavZX4Mwb5-5aeo1g8y_oxQfCpUPE66ShqXrbhI9CS1mVxaZOxNjlHtQ-G_jIWP4s/s1600/SENSITIVE+OPTICAL+BURGLAR+ALARM.jpg" -->

Sensitive Optical Burglar Alarm

This optical burglar alarm uses two 555 timer ICs (IC1 and IC2). Both the ICs are wired as astable multivibrators. The first astable multi...

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Light Detector Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> <b><i>Light detectors</i></b> are one of the most popular sensor and they are commonly found in many real-world applications. They are widely used by electronic hobbyists and projects because they are practical and intriguing yet surprising easy to construct. This will guide and show you how easy it is to make your own light activated Light Emitting Diode (LED) with minimal tools and materials. The whole project is simple. This implementation can be used for an educational demo or applied directly to the practical world.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>Parts</b></div> <div style="text-align: justify;"> <ol> <li>Breadboard or PCB Board</li> <li>A few Jumper Wires</li> <li>9 Volts Battery</li> <li>9 Volts Battery Clip</li> <li>Light Dependent Resistor (LDR)</li> <li>Light Emitting Diode (LED) with any color of choice</li> <li>TLC3704 Quad Comparator (only one of its four comparators will be used) (Alternatively, you can use the single LM311N Comparator with 8 pin)</li> <li>3362P-103-ND 10K Ohms Variable Resistor</li> <li>1K Ohms (Brown-Black-Red) Resistor X2</li> <li>330 Ohms (Orange-Orange-Brown) Resistor</li> </ol> </div> <div style="text-align: justify;"> <b>Circuit Diagram</b></div> <div style="text-align: justify;"> <b><br /></b></div> <div style="text-align: center;"> <img height="245" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiMp68o9E16_jfwVdVS57VQ3lIhiMIUIvghjIBWaGztlE9vBDTL7E4XHorjWuLpS1OFhSdj-6O9FPQHpmHJUxAnuKE8_LoUQJLQwY9Gm6FO7ixaNUM4jQwEErL-5HR5t9sbo_rkbOKHG5uT/s1600/light+detector+circuit.png" width="640" /></div> <div style="text-align: center;"> <br /></div> <div style="text-align: justify;"> <b>Working</b></div> <div style="text-align: justify;"> As its name suggests, a comparator compares two given voltages. The pair of 1K ohms resistors create a voltage divider and provide a 4.5 volts reference for the comparator. The variable resistor and LDR both form another pair for a second voltage divider. When light falls on the LDR, its resistance lowers and that voltage divider provides a voltage lower than 4.5 volts. The comparator produces no output (0 volts). When light is absent, the resistance of the LDR and the voltage increases. When the voltage increases over 4.5, the comparator activates its output and supplies 9 volts to power the LED.</div> </div> <!-- Blogger automated replacement: "https://images-blogger-opensocial.googleusercontent.com/gadgets/proxy?url=http%3A%2F%2F4.bp.blogspot.com%2F-m1RYD86-Now%2FU4xlYMRJuLI%2FAAAAAAAAAXo%2FaoPX-HFsky8%2Fs1600%2Flight%2Bdetector%2Bcircuit.png&container=blogger&gadget=a&rewriteMime=image%2F*" with "https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiMp68o9E16_jfwVdVS57VQ3lIhiMIUIvghjIBWaGztlE9vBDTL7E4XHorjWuLpS1OFhSdj-6O9FPQHpmHJUxAnuKE8_LoUQJLQwY9Gm6FO7ixaNUM4jQwEErL-5HR5t9sbo_rkbOKHG5uT/s1600/light+detector+circuit.png" -->

Light Detector Circuit

Light detectors are one of the most popular sensor and they are commonly found in many real-world applications. They are widely used by e...

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Gas Leak Detector Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> This is a <i>gas leak detector circuit</i> that detects the leakage of LPG gas and alerts the user through audio-visual indications. The circuit operates off a 9V PP3 battery. Zener diode ZD1 is used to convert 9V into 5V DC to drive the gas sensor module.The gas leakage circuit uses the <i><b>SEN-1327 gas sensor module</b> from <b>RhydoLABZ</b></i>. Its output goes high when the gas level reaches or exceeds certain point. A preset in the module is used to set the threshold. Interfacing with the sensor module is done through a 4-pin SIP header.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> Pin details of the gas sensor module are shown in Fig. 2. An <b>MQ-6 gas sensor</b> is used in the gas sensor module. The sensor can also be used to detect combustible gases, especially methane.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>Circuit Schematic</b></div> <div style="text-align: justify;"> <b><br /></b></div> <div style="text-align: center;"> <img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6u-9L0MzAvaFiQZ_vbLvQS-XsvQ7VLTLWKCaRoeooqRjzjkytw6jTjBf83YGnAAP_pg9TkNnj8fC4Verjgpw6ss7uhelr99cWpgeaRzyBjHOSaxbN0HAIml6wiKKr5FZHUr3jjPraCWiK/s1600/Gas+detector+circuit.jpg" /></div> <div style="text-align: center;"> <br /></div> <div style="text-align: justify;"> Whenever there is LPG concentration of 1000 ppm (parts per million) in the area, the OUT pin of the sensor module goes high. This signal drives timer IC 555, which is wired as an astable multivibrator. The multivibrator basically works as a tone generator.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> Output pin 3 of <i>IC 555</i> is connected to LED1 and speaker-driver transistor SL100 through current-limiting resistors R5 and R4, respectively. LED1 glows and the alarm sounds to alert the user of gas leakage. The pitch of the tone can be changed by varying preset VR1. Use a suitable heat-sink for <i>transistor SL100</i>.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>SEN1327 gas sensor pin details</b></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3eYxjJkpj_FUqLmis2HXX0f0LMeFImrmmEsXTyyQxo2r2dylM451pcxqrhO6gtWaGMy9VKorEiC9ZPa9UTg-FtNgLYj5dJQz8gjghdUV4oma8pipN51hQsfl60Izi0yW8Du48HPpi_yoW/s1600/sen-1327-pins.jpg" /></div> </div> <!-- Blogger automated replacement: "https://images-blogger-opensocial.googleusercontent.com/gadgets/proxy?url=http%3A%2F%2F3.bp.blogspot.com%2F-kJwawKaUquY%2FU53Nr35FU5I%2FAAAAAAAAAYs%2Fyy06qpTltNQ%2Fs1600%2FGas%2Bdetector%2Bcircuit.jpg&container=blogger&gadget=a&rewriteMime=image%2F*" with "https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6u-9L0MzAvaFiQZ_vbLvQS-XsvQ7VLTLWKCaRoeooqRjzjkytw6jTjBf83YGnAAP_pg9TkNnj8fC4Verjgpw6ss7uhelr99cWpgeaRzyBjHOSaxbN0HAIml6wiKKr5FZHUr3jjPraCWiK/s1600/Gas+detector+circuit.jpg" --><!-- Blogger automated replacement: "https://images-blogger-opensocial.googleusercontent.com/gadgets/proxy?url=http%3A%2F%2F4.bp.blogspot.com%2F-SkJqfWXukDY%2FU53OC40NjLI%2FAAAAAAAAAY0%2Fb3UcK2fdHOw%2Fs1600%2Fsen-1327-pins.jpg&container=blogger&gadget=a&rewriteMime=image%2F*" with "https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3eYxjJkpj_FUqLmis2HXX0f0LMeFImrmmEsXTyyQxo2r2dylM451pcxqrhO6gtWaGMy9VKorEiC9ZPa9UTg-FtNgLYj5dJQz8gjghdUV4oma8pipN51hQsfl60Izi0yW8Du48HPpi_yoW/s1600/sen-1327-pins.jpg" -->

Gas Leak Detector Circuit

This is a gas leak detector circuit that detects the leakage of LPG gas and alerts the user through audio-visual indications. The circuit...

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Motion Detector Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> <span style="font-family: inherit;">This is a circuit which can detect any motion or movement. It's most common use is to detect a person moving through an area where the motion detector can sense. </span><span style="font-family: inherit;">For example, the motion detector may be placed near a door, so that if any person passes through this doorway, the motion detector will be triggered.</span></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <span style="font-family: inherit;">The main electronic component we will use that allows us to pick up this detection is the PIR motion sensor. The PIR motion sensor is a sensor which detects movement through picking up infrared waves. Being that a person emits infrared waves, the detector is able to detect these waves and react, according to the how the circuit is designed to react. The sensor can also pick up the movement of inanimate objects as well, such a rolling ball, because as those objects move, friction acts on them, generating heat. This heat emits infrared radiation, which the PIR sensors may be able to detect if great enough.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;">In our basic circuit, when the motion detector circuit picks up movement, a red LED will flicker on. </span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Parts</b></span></div> <div style="text-align: justify;"> <ul> <li><span style="font-family: inherit;">PIR motion sensor</span></li> <li><span style="font-family: inherit;">LED</span></li> <li><span style="font-family: inherit;">470Ω Resistor</span></li> <li><span style="font-family: inherit;">6V of DC power</span></li> </ul> </div> <div style="text-align: justify;"> <span style="font-family: inherit;">The PIR motion sensor is, again, a sensor which can detect movement through picking up infrared radiation. Being that people naturally give off radiation, because of our generated body heat, the motion can easily detect people walking and moving through a vicinity within the sensor's range.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;">The motion sensor has a sensitivity range up to 20 feet (6 meters) and a 110° x 70° detection range, making it a wide lens detection sensor. This means it can measure 110° vertically (from top to bottom) and 70° horizontally (from left to right). The best way to check its sensitivity is when the circuit is built, try moving around through all of its angles. See at which angles it can detect your movement and at which angles it is not able to detect your movement, meaning your out of its angle scope. A lot of it is trial and error and experimenting. Once you know where it can and cannot detect, you can place it in an optimal place where it can detect in areas where you want it to.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>The PIR motion sensor is a 3-pin device</b></span></div> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody> <tr><td style="text-align: center;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpDupv6EcdfIEP4H1JrZCv7ZV8yEy6JkzR27CshMNx4Or9ArNwj86yYNgVUrN6XrvsnGWmmk6EqAgwd9IXtX8EONx3vIVdBLKVmb9oTpUrqKrLf_34E-5XtLGvyRyKVsZsDWdOUJJ7wnFD/s1600/PIR-motion-sensor-pinout.png" style="margin-left: auto; margin-right: auto;" width="163" /></td></tr> <tr><td class="tr-caption" style="text-align: center;"><b><i>Fig.  PIR Module</i></b></td></tr> </tbody></table> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Pin 1</b> is the pin which receives the positive DC voltage. The PIR motion sensor needs between 5V-9VDC of power for operation. In our case, we will use about 6V of power. This can be obtained from switching a DC power supply to 6V or using 4 'AA' batteries connected in series. We will then feed this voltage into pin 1 of the PIR module.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Pin 3</b> is the negative DC voltage or ground pin of the device. We connect the negative terminal of the power source to this pin, for a return path.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Pin 2</b> is the Output pin of the PIR module. This is where the output of the PIR will leave from. When motion is detected by the PIR, its output will go high to 3V. When no motion is detected, its output low and it gives off practically no voltage. When high you can see then how it can power a load, such as an LED to light. This way we can know when it has detected motion or not.</span></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <span style="font-family: inherit;">In our circuit, we will connect a 470Ω resistor in series with an LED to the output pin of the PIR sensor. When motion is detected, the output of the PIR sensor will swing high and power and light the LED.</span></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Circuit Diagram</b></span></div> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><img border="0" height="302" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijx4MfcRqUJM1RxcHgD0Q-8jkeD-ZF9QwdRydKZXrtsN-xtZ9Brca-Q820d3oWxd1a1Ycqnp74hR1VY42EJraN3qKCDrkuJSAbrHk4dfw3ZYGRYyfXwrEFCTjAUrf_omaF0A68P80wyBD7/s1600/PIR+Motion+Sensor.jpg" style="margin-left: auto; margin-right: auto;" width="400" /></td></tr> <tr><td class="tr-caption" style="text-align: center;"><b><i>Fig.  Motion Detector Circuit</i></b></td></tr> </tbody></table> <div style="text-align: justify;"> <span style="font-family: inherit;">Here you can see anywhere from 5V-9V is fed into the power pins.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;">Connected to the output pin is an LED. We place a 470Ω resistor in series to limit current so that the LED doesn't receive excess current.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;">In this circuit, when motion is detected, the output voltage swings high and powers the LED. After about 1 second or 2, the output swings back low and the LED turns off until motion is detected again. Without any motion, the LED just stays off.</span></div> </div> <!-- Blogger automated replacement: "https://images-blogger-opensocial.googleusercontent.com/gadgets/proxy?url=http%3A%2F%2F2.bp.blogspot.com%2F-icrU6Vvlbd8%2FU-32C85_5CI%2FAAAAAAAAAdQ%2FMtha21Pv8qw%2Fs1600%2FPIR-motion-sensor-pinout.png&container=blogger&gadget=a&rewriteMime=image%2F*" with "https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpDupv6EcdfIEP4H1JrZCv7ZV8yEy6JkzR27CshMNx4Or9ArNwj86yYNgVUrN6XrvsnGWmmk6EqAgwd9IXtX8EONx3vIVdBLKVmb9oTpUrqKrLf_34E-5XtLGvyRyKVsZsDWdOUJJ7wnFD/s1600/PIR-motion-sensor-pinout.png" -->

Motion Detector Circuit

This is a circuit which can detect any motion or movement. It's most common use is to detect a person moving through an area where the...

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Simple Photoelectric Detector Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> <span style="font-family: inherit;">A proximity detector is gadget that detects when an object is nearby. There are 2 ways to build a proximity detector. One is mount the IR LED and the </span>photo-transistor<span style="font-family: inherit;"> so that they face each other. Then the infrared light is detected by the photo transistor. If an object comes between the IR LED and the photo-transistor, the light is blocked, and the photo-transistor turns off.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;">The other way is to build a proximity detector is to mount the <b>IR LED</b> and the <b>IR photo-diode</b> next to each other facing the same direction. When an object comes near the <b>IR LED</b>, some infrared light will bounce off the object and be detected by the <b>photo-transistor</b>.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>How to Build a Common-Emitter Proximity Detector</b></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Parts</b></span></div> <div style="text-align: justify;"> </div> <ol> <li><span style="font-family: inherit;">Photo-transistor</span></li> <li><span style="font-family: inherit;">33KΩ Resistor</span></li> <li><span style="font-family: inherit;">330Ω Resistor</span></li> <li><span style="font-family: inherit;">IR LED</span></li> <li><span style="font-family: inherit;">9-volt Battery or DC Power Supply</span></li> <li><span style="font-family: inherit;">Red LED</span></li> </ol> <br /> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Schematic Diagram</b></span></div> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4rXfG7oxuIkJlUiGbAIF5hq-iIzmvlZxckCwzOVUNZycgYJuCzmaTAX1QlAdWxNkyjScyIV2i-rdDk7u1T_Lxl5Wb5T7c44oj2Zr417iI3zAKRuyRGciXw5XwvvEAXIfOVYNTgBpbjO85/s1600/Photoelectric+Sensor.jpg" style="margin-left: auto; margin-right: auto;" width="245" /></td></tr> <tr><td class="tr-caption" style="text-align: center;"><b><i>Fig.  Photoelectric Sensor</i></b></td></tr> </tbody></table> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> </div>

Simple Photoelectric Detector Circuit

A proximity detector is gadget that detects when an object is nearby. There are 2 ways to build a proximity detector. One is mount the IR ...

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Metal Detector Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div class="separator" style="clear: both; text-align: center;"> </div> <span style="text-align: justify;">The device we then build will function as a metal detector that can scout out metal objects, such as coins, nails, keys such as car keys you may not be able to find, and even gold if you're looking for in a beach (though this one may not have industrial strength). This metal detector can detect certain kinds of metal- especially iron-containing metals, which are called ferrous metals, even if under a half-inch of drywall or sand.</span><br /> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> How this metal detector works is that it uses an IC that generates an AC signal that goes through a coil. Metal objects are objects which conduct electricity, so a current can be induced in these metal objects. When the coil in the metal detector comes near a metal object, the electromagnetic field in the coil induces currents in the metal object. The electromagnetic field generated by the metal changes the current in the coil. When the signal changes, the IC turns on an LED i.e. alerting the user to the presence of a metal.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>Circuit Diagram</b><br /> <b><br /></b></div> <div style="text-align: justify;"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcCLtLYqXNwJKbVq6rBDxSHL3Z6htTTMaaqOLs3L0A-rJbcPlBf9oGaVLg_N42we2pLx7vCVRkFtFqqOeYxLYxOFeifAXhI27o4TqTwInCHUNvHxiQ_0qButYnDspsWWbwP8MW28udgIPF/s1600/Metal-detector-circuit.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="371" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcCLtLYqXNwJKbVq6rBDxSHL3Z6htTTMaaqOLs3L0A-rJbcPlBf9oGaVLg_N42we2pLx7vCVRkFtFqqOeYxLYxOFeifAXhI27o4TqTwInCHUNvHxiQ_0qButYnDspsWWbwP8MW28udgIPF/s1600/Metal-detector-circuit.png" width="640" /></a></div> <br /></div> <div style="text-align: justify;"> <b>Parts Needed</b></div> <div style="text-align: justify;"> <ol> <li>TDA0161 Proximity Detector (IC1) </li> <li>2 1KΩ Resistors (R1, R4) </li> <li>10KΩ Potentiometer (R2) </li> <li>330Ω Resistor (R3) </li> <li>120Ω Resistor (R5) </li> <li>2N3904 Transistor (Q1) </li> <li>2 4.7nF ceramic capacitors (C1, C2) </li> <li>680 picohenry bobbin-type Inductor </li> <li>Battery Holder for 4 AA batteries (6V) </li> <li>LED </li> <li>SPST Switch </li> </ol> </div> <div style="text-align: justify;"> <b>Explanation of Circuit</b></div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>Inductor L1 :</b> The inductor L1 forms a parallel circuit with the capacitor C1 to form an LC parallel circuit. When a signal that oscillates at several KHz passes through this circuit, the signal creates an electric field around the coil. When you bring the coil near a metallic object, that electric field induces an oscillating signal in the object. So when the oscillating signal has been induced in the metallic object, the signal in the object creates an electric field that induces current in the coil. This current changes the oscillating signal running through the LC parallel circuit.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>TDA0161 Proximity Detector IC :</b> This IC is a proximity detector. This IC suplies the oscillating signal that is sent through the LC parallel circuit. The IC also responds to any changes in the signal. The IC has an output of 1 milliamperes (mA) or less if the coil is far from a metallic object and an output of 0mA or higher if the coil is near a metallic object. </div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> Thus, this IC is at the heart of this circuit. When the object is far from a metallic object, the current which the IC produces is insufficient to drive the LED. Thus, the LED does not turn on. When the coil is near a metallic object, the IC produces sufficient power to drive the LED and it turns on. </div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>Resistor R1 and Potentiometer R2 : </b>These resistors are used to calibrate the TDA0161 IC to the LC circuit. You calibrate it by adjusting the potentiometer to change the current output it creates in accordance with the proximity of metal to the coil. You can adjust so that it can detect metals at the distances which you want it to. By increasing the potentiometer resistance, the IC will create less current output. Therefore, a metal must be placed closer to the coil in order for the LED to light. By decreasing the potentiometer resistance, the IC produces less current output, so the metal doesn't have to be placed as close to the coil. It's up to you to set the adjustment.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>2N3904 Transistor (Q1) :</b> The 2N3904 transistor provides amplification, so that there is sufficient current to power the LED. Without this transistor, there would not be enough power to turn on the LED. </div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>LED :</b> The LED in the circuit serves as an indicator to when there is a presence of a metal. When a metal is in close proximity to our electronic circuitry, the LED turns on. This shows we have found metal. When the LED is off (not lit), then our metal detector has not detected metal and indicates no metal is in close proximity.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>6 volts :</b> The 6 volts is the supply power to the entire circuit. This 6 volts is supplied through 4 AA batteries in series. Being that each battery supplies 1.5 volts, 4 AA batteries (1.5 volts * 4) provides 6 volts. This 6 volts gives power to every component in the circuit.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> <b>SPST Switch :</b> The SPST switch allows us to shut off power to the circuit, if we want the metal detector power shut off, just like any electronic device would have. This just serves asn an on/off switch.</div> <div style="text-align: justify;"> <br /></div> <div style="text-align: justify;"> This circuit detects metal through the coil, L1. Once metal is placed near the inductor L1, it will trigger current production from the proximity detector IC, which in turn lights the LED. So to test this circuit, just place a metallic object near this inductor. When done, the LED should turn on. When the metallic object is moved away, the LED should shut off.</div> <div style="text-align: justify;"> </div> </div> <!-- Blogger automated replacement: "https://images-blogger-opensocial.googleusercontent.com/gadgets/proxy?url=http%3A%2F%2F2.bp.blogspot.com%2F-_yOXwdpl0DI%2FU-3zCM13QWI%2FAAAAAAAAAdI%2F3GWektla34Y%2Fs1600%2FMetal-detector-circuit.png&container=blogger&gadget=a&rewriteMime=image%2F*" with "https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcCLtLYqXNwJKbVq6rBDxSHL3Z6htTTMaaqOLs3L0A-rJbcPlBf9oGaVLg_N42we2pLx7vCVRkFtFqqOeYxLYxOFeifAXhI27o4TqTwInCHUNvHxiQ_0qButYnDspsWWbwP8MW28udgIPF/s1600/Metal-detector-circuit.png" -->

Metal Detector Circuit

The device we then build will function as a metal detector that can scout out metal objects, such as coins, nails, keys such as car keys ...

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Sensitive Intruder Alarm Circuit

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> <span style="font-family: inherit;">This circuit diagram of an ultra sensitive intruder alarm. The shadow of an intruder passing few meters nearby the circuit is enough to trigger the alarm. Here IC2 uA 741 is wired as a sensitive comparator ,whose set point is set by R6 &R7. The voltage divide by LDR and R9 is given at non inverting pin of IC2. At standby mode these two voltages are set equal by adjusting R9. Now the output (pin6) of comparator will be high.Transistor Q1 will be off. The voltage at trigger pin of IC1 will be positive and there will be no alarm. When there is an intruder near the LDR the shadow causes its resistance to increase. Now the voltages at the inputs of comparator will be different and the out put of IC2 will be low. This makes Q1 on. This makes a negative going pulse to trigger the IC1 which is wired as a monostable multivibrator.The out put of IC1 will be amplified by Q2 (SL 100) to produce alarm.</span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> </div> <div style="text-align: left;"> <span style="font-family: inherit;"><b>Intruder Alarm Circuit Diagram with Parts List</b></span></div> <span style="font-family: inherit;"><br /></span> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmZe1wniPji8zfvC9vqtjleE9LCJBaBYGj9ayQ48Ublvxg_U8EztgOujXnKwdS7DNjsSZmiqTx-UiejMPV4wXGZpZJsTVHs2H_55fl4BF3Uy2wbK-rIhOuP2IRuDtnomk-ANSmwE3WH36w/s1600/Sensitive+Intruder+Alarm+Circuit.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-family: inherit;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmZe1wniPji8zfvC9vqtjleE9LCJBaBYGj9ayQ48Ublvxg_U8EztgOujXnKwdS7DNjsSZmiqTx-UiejMPV4wXGZpZJsTVHs2H_55fl4BF3Uy2wbK-rIhOuP2IRuDtnomk-ANSmwE3WH36w/s1600/Sensitive+Intruder+Alarm+Circuit.jpg" /></span></a></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><br /></span></div> <div style="text-align: justify;"> <span style="font-family: inherit;"><b>Notes</b></span></div> <div style="text-align: justify;"> </div> <ul> <li><span style="font-family: inherit;">To setup the alarm ,power up the circuit and adjust R9 so that LED  D1 goes off.</span></li> <li><span style="font-family: inherit;">The LDR can be housed in a dark tube to increase sensitivity.</span></li> <li><span style="font-family: inherit;">The sensitivity is very important here. If you cannot adjust the required sensitivity properly, use one LOW resistance (~1K ) POT in series with  R9 for fine adjustment.</span></li> </ul> </div>

Sensitive Intruder Alarm Circuit

This circuit diagram of an ultra sensitive intruder alarm. The shadow of an intruder passing few meters nearby the circuit is enough to tr...

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