I'm a beginner at electronics. I'm trying to use this Infrared phototransistor and my Arduino together: http://www.maplin.co.uk/infrared-transmitter-and-receiver-10379

I'm using the popular library here: https://github.com/shirriff/Arduino-IRremote

I've wired up the phototransistor best I could with my limited knowledge and by searching Google.

I have done the following although some of the terminology I'm using may be wrong:

  1. Anode of the phototransistor to +5v through a 56K resistor
  2. Anode also to Arduino pin 11
  3. Cathode of the phototransistor to ground

I've used one of the example sketches from the Arduino library to print to the serial monitor whatever is received from my Logik TV remote.

This only receives information when I'm really up close and the bytes it receives are different every time with the same remote control button. However if I get super up close the bytes start to look more similar. When I'm within a few mm, the library actually recognises the protocol as NEC.

What is wrong with my circuit that I need to be up so close? Am I not putting enough volts through the IR PT? Or is it something else? My TV works fine so I know it's not the remote. I've tried following this schematic as closely as I could:

enter image description here

And this is how I have physically connected the breadboard:

enter image description here

  • \$\begingroup\$ Transistors don't have anodes and cathodes! Schematic is required! \$\endgroup\$ Oct 26, 2013 at 10:05
  • \$\begingroup\$ Sorry, I didn't know that. I did mention I am a beginner so I've tried to use the terminology I know to convey my meaning. I've used this as closely as I could: pages.drexel.edu/~pyc23/IR_proximity_sensor.jpg \$\endgroup\$ Oct 26, 2013 at 10:08
  • \$\begingroup\$ @MattHarrison, you'd need a datasheet for a good answer, but guessing from the Maplin page I'd say a 1K would be worth a try instead. Maybe even try 10K as an interim step to see if it improves things. \$\endgroup\$
    – PeterJ
    Oct 26, 2013 at 10:14
  • \$\begingroup\$ @PeterJ Thanks, unfortunately I cannot find a datasheet. Which part of the info on the page indicates that I should use a lower ohmage resistor? I'm trying to understand how to interpret these things! \$\endgroup\$ Oct 26, 2013 at 10:59
  • \$\begingroup\$ The linked description for Arduino-IRremote library says "These receivers provide a filtered and demodulated inverted logic level output; you can't just use a photodiode or phototransistor." I've used this library, and I've had success with these receivers too, and not with a phototransistor alone. Nice to hear it can work, inverted, albeit at short distance. \$\endgroup\$ Oct 26, 2013 at 11:05

2 Answers 2


The IR Receiver you have is a simple phototransistor. The IR Receiver the library uses is a (typically) 38khz IR decoder, with logic on it to remove the remote's carrier wave. They are not interchangeable.

Below is a typical one. Sometimes they have metal shields around them.

enter image description here

You can find them in any radioshack, or any cable box that has been thrown out. Heck, sometimes new cable boxes come with a little receiver cable that lets you hide the box but still use your remote.

enter image description here

  • 1
    \$\begingroup\$ Thank you so much, I stripped one out of an old DVD player and now it works an absolute treat! \$\endgroup\$ Oct 27, 2013 at 9:35

Checkout my article below (with images), since some phototransistors use different pinout and are not interchangeable: http://zoomicon.wordpress.com/2010/02/05/pin-out-for-tsop1736-and-tsop2138-ir-receiver-ics/ Had looked up that info for our air-conditioning unit repair guy, since he couldn't find the same phototransistor type to replace (stock shortage)

Also see the schematic at the end of the Linux IR receiver page: http://www.lirc.org/receivers.html it could help since it shows how to make a receiver for connection to RS-232C port of PC


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.