Adadfruit IR sensor - TSOP38238

Other Hardware Sensors
1

Today came an IR sensor - TSOP38238 - and I installed the IRRemote library 2.2.3 of shiffer.

Worked very well but I noticed the following:

When I put a finger near the sensor (< 1cm) it suddenly spits out codes. I doubt my fingers transmit a 38KHz signal but I can imagine that the sensor picks up heat and just tries to make the best of it.

If the finger moves closer to the sensor there are more "succesfull" reads. A black SD card behaved similar. White and transparent objects gave less responses.

So another explanation is that the sensor has a 38KHz signal internally for reference and if an object is very close it sees the reflection of that signal.

In the end this effect can be used as a very close proximity sensor (to investigate)

Has anyone seen this behavior before? and can explain it?

2

There is a very high gain amplifier and detector inside a 3-pin IR receiver, that is sensitive to hum/hash pickup. Some IR sensors are encapsulated in a metal cage for that reason. Not sure why you see some effect with an SD card. It's not just plastic, there are metal parts inside.
Leo..

3

Thanks, TSOP38238 has no cage so that explains a lot. Thanks.