My goal here is to make an IR sensor detect remote control signals. I wired up a 4.5 V IR sensor (TSOP1556) like this (Leftmost side is the sensor pins, the numbers are Pi pins):

Gnd — 6 (ground)

Vs — 2 (5V)

Out — 1 kOhm — 12 (GPIO 18) — 1.2 kOhm — 6

Voltage between GND and OUT is 0.3 V. Does this mean the sensor is broken?

All tutorials demonstrating how to test a sensor with batteries and a LED had me believe that OUT should only be low when the sensor receives a signal.


So, one proposed solution, if I understood @Milliways correctly:

Gnd — 6 (ground)

Vs — 2 (5V)

Out — 12 (GPIO 18) — 120 kOhm — 6

Which would theoretically give 3 V on OUT when taking into account the 80k internal sensor resistance. Probably safe to try?


  • Why are you running it at 5V? RPi is 3V3 so just run it at 3V3 same as the RPi. The datasheet (not the link you posted.) shows no voltage divider for the OUT line and warns of pulling it low continuously which makes sense looking at the block diagram. And yes, its active low. Jan 31, 2018 at 7:42
  • @ChefFlambe Because as far as I can tell the data sheet (?) says 4.5 V minimum supply voltage. What's wrong with the link?
    – Andreas
    Jan 31, 2018 at 11:21
  • Ah, yeah you're correct about the 4.5V if it is in fact the older tsop1556. I was looking at the latest datasheet from digikey as your link only allowed a 2 page preview then I'd have to download. My bad. However, are you sure its the TSOP 1556? That's an older device (20 yr old?) and its been replaced by the TSOP 31556 which DOES have a supply range of 2.5V to 5.5V. Its the same package and a few other tweaks, and they made the supply range wider, then added a 3 to the beginning of the product code to indicate the difference. Jan 31, 2018 at 17:57
  • @ChefFlambe I'm pretty sure. I pulled it from an old Xbox DVD dongle.
    – Andreas
    Jan 31, 2018 at 20:51
  • @ChefFlambe About the 31556: how did you go about determining the name of the successor to, in this case, the 1556? Is there an easy way to do that? Also, I can't find 31556 on vishay.com/ir-receiver-modules/show-all — does that mean there's an even newer replacement? (I got a 34436 working, and learned the hard way that a 36 kHz receiver can't replace a 56 kHz one)
    – Andreas
    Mar 6, 2018 at 2:02

1 Answer 1


Your question is unclear, but one thing is obvious - connecting a 2.2kΩ resistor to the output is shorting the device and won't work.

It is unclear from the post what the device requires.

  • Thanks. I added the component name that I forgot to mention. What else could I add to make the question more clear? Also, is a voltage divider useless here then? I was hoping to be able to use a sensor that required more than 3.3 V.
    – Andreas
    Jan 30, 2018 at 23:03
  • Made some edits. Not sure if clearer.
    – Andreas
    Jan 30, 2018 at 23:18
  • The device appears to be a high impedance device with limited drive capability. I don't know the device or have the relevant data sheet. You COULD try a 120kΩ resistor to ground, but I would use a level shifter.
    – Milliways
    Jan 30, 2018 at 23:22
  • Certainly for testing I would just use a 50k resistor between OUT and the GPIO. I wouldn't bother with the voltage divider (i.e. the other resistor to ground) as there are probably other resistors to ground on that line internal to the chip (and the maths is beyond me),
    – joan
    Jan 31, 2018 at 8:20
  • @joan Thanks for the suggestion. I tried it but couldn't get it to work. It works fine with 5 V battery and LEDs though. I also have a TSOP1333 that works fine with a LED, but just can't get them to work with the Pi.
    – Andreas
    Jan 31, 2018 at 20:57

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