How to Connect an IR Photodiode Sensor

In this post we learn how to correctly connect an IR photodiode in circuits such as a proximity sensor circuit. The explanation is presented in the form a discussion between one of the dedicated readers of this blog NVD, and me.


Here's the discussion which explains how to connect a photodiode in an electronic circuit


sir,
can you please tell me whether following circuit work or not. i think output of ic is 5v.i I want the output to be connected to a 12v relay instead of buzzer..can you tell what alterations should i make in the circuit..






IR proximity detector circuit
photodiode IR image with polarity anode cathode
(+) is the Anode, and (-) is the Cathode




  • NvD, if it's set correctly then it should work..
  • you can use a BC547/relay stage at the output of the opamp, the base resistor cold be 10K
thank you sir
can u give me circuit of bc547 relay driver circuit

  • NvD, you can refer to the following article
  • http://www.homemade-circuits.com/2012/01/how-to-make-relay-driver-stage-in.html
ok sir
sir is there any positive and negative terminal for ir reciever and transmitter like led.Im new to to this,thats why asking

  • NvD, just like any other diode, IR photo-diodes also have polarity and must be connected accordingly.
sir,
in the circuit, photodiode is connected forward bias.is it wrong? Please check sir

  • NVD, the transmitter IR photodiode polarity is correct...receiver polarity is wrong, needs to be inverted for the receiver as shown below.


sir,firstly i forgot to connect ic pin 3 to transmiter resistor then i have given a supply of 12v.led lits only.after that i connected pin 3 to resistor and given 9v.Now led lits when i turn the variable resister to one side.led doesnt lit when obstacle is brought in front.pls help me sir

  • did you invert the LED polarity which is connected with the pin#3?? first do this. then adjust the preset until the output LED just shuts off.
  • after this you can switch ON the transmitter photoLED, keep it parallel to the pin3 photoLED and bring an obstacle in front of the two sensors and check the response
  • cathode of the pin#3 photo LED must connect with the positive line....This is how any IR photodiode needs to be connected in a given electronic circuit

sir, i connected everything properly.still it doesnt work.i there any chance of ic or photodiode burn off when i connected 12v supply.do you have any circuit diagram for ir proximity senser

  • NVD, the photodiode will never burn as long as its connected in series with a resistor.
  • bring the transmitter close to the Rx diode manually and check whether it responds or not, also while doing this check the voltage at pin3...remember pin3 preset should be set in such a way that without the Tx signal its potential should be just below the pin2 value....you must fix this first.      

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