Electronics > Beginners
TSOP4138 false triggering ???
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andybarrett1:
Hi and thanks for reading
I have interfaced a Vishay TSOP4138 IR receiver with a Microchip PIC 16f648 all is good and works well.
But all I am interested in is the first falling edge on the output of the 4138 when it sees the presence of a 38Khz source.
*** I suspect I am getting false noise and this is triggering my Pic ***
*Circuit is a per datasheet*
Looking at the datasheet the TSOP4138 does have a pullup (25k) but what I am wondering is if I put a harder pull up (22k maybe) in parallel then a 0.1uf cap to ground from the OP pin to the PIC.
Would that act as a hardware filter.....???
Advice and help welcome thank you again for reading
BR
Andy
Buriedcode:
These devices are very sensitive to noise on the power supply, as well as EMI. I recently used a similar device and ended up with 100 ohm resistor with a 47uF cap as a LPF for the Vsupply. I believe the application circuit in the datasheet also has this filter (but with no part values). A good start would be a 47ohm resistor with a 10uF cap.
With that said, it will still probably get false triggers on the output, and your software should be able to cope with these. When a remote is sending a signal the AGC kicks in and reduces the gain, so you won't get false spikes in the middle of a transmission, only when its idle. Your software should be able to distinguish between a valid signal (NEC, sony, RC-5) and false triggers.
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