I had a similar issue while decoding ceiling fan remote IR codes last month. It's most likely noise going into the IR receiver power pin causing oscillations at the output. A sensitive preamp I guess, maybe that's why one of the popular Chinese IR receiver part is wrapped in a ground shield. In my case, I was using a TSOP4838 running from Pico's 3V3. Without an RC filter across the power pins, it is prone to oscillations. I bought a bare part, so I mirrored the output level to the Pico LED for visual feedback.
I finally followed the 47R and 47uF recommended circuit in (search for) the "ax-1838hs datasheet". All the signal I wanted were successfully decoded and the timings were nice and clean. I had an another (old) part from 2012 (a PIC project) that was even more prone to oscillations -- non-stop oscillations when I used a Pico GPIO to power it (plugged into a breadboard to a GND and 2 GPIO).
With the power supply RC filter, the received signals are error-free. However, the TSOP4838 can still be made to oscillate -- when I put my smartphone near the IR receiver. IIRC, oscillations happen only when the phone's screen is powered, so it (or the wires) may be picking up EM from the LCD being driven. It's possible the same may be happening in your case. If not a smart phone, perhaps a smart watch. I dunno whether an LCD TV would cause the same thing if it is nearby, but you can try a few of these things and see what gives you a more constant LED light.
I finally followed the 47R and 47uF recommended circuit in (search for) the "ax-1838hs datasheet". All the signal I wanted were successfully decoded and the timings were nice and clean. I had an another (old) part from 2012 (a PIC project) that was even more prone to oscillations -- non-stop oscillations when I used a Pico GPIO to power it (plugged into a breadboard to a GND and 2 GPIO).
With the power supply RC filter, the received signals are error-free. However, the TSOP4838 can still be made to oscillate -- when I put my smartphone near the IR receiver. IIRC, oscillations happen only when the phone's screen is powered, so it (or the wires) may be picking up EM from the LCD being driven. It's possible the same may be happening in your case. If not a smart phone, perhaps a smart watch. I dunno whether an LCD TV would cause the same thing if it is nearby, but you can try a few of these things and see what gives you a more constant LED light.
Statistics: Posted by katak255 — Sat May 11, 2024 2:24 am