| 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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