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ESP8266 and HC-SR501 false positives 
Trying to install a motion detector in my living room to trigger lights I decided that constructing one myself using a ESP8266 module and a cheap HC-SR501 module was an interesting challenge.
Some soldering and an Arduino sketch later it was operational.
During the day my setup works fine but for some reason during the night it kept triggering.
After much searching it seems that the gain stage of the HC-SR501 suffers from interference from the wifi. To eliminate this I placed a 220nF capacitor across pin12 and pin13 of the chip (verify that it actually is a BISS0001).
Unfortunately the package isn't exactly geared to receive any capacitors so some improvising was in order.
After that no more false positives.
Some soldering and an Arduino sketch later it was operational.
During the day my setup works fine but for some reason during the night it kept triggering.
After much searching it seems that the gain stage of the HC-SR501 suffers from interference from the wifi. To eliminate this I placed a 220nF capacitor across pin12 and pin13 of the chip (verify that it actually is a BISS0001).
Unfortunately the package isn't exactly geared to receive any capacitors so some improvising was in order.
After that no more false positives.
09-'16 VPN and VLAN with Ubiquity EdgeRouterX
Comments
By
peterrus_,
donderdag 8 november 2018 00:29
Heel obscuur, maar er gaat vast ooit iemand wat aan hebben 
keep it up
keep it up
By
redfox314,
donderdag 8 november 2018 07:01
Da's precies waar het om gaat, hier heb ik maanden op gezocht en toen ik in de trein iemand tegen kwam die exact hetzelfde probleem ook niet opgelost kreeg ben ik maar in mijn pen gekropen.peterrus_ wrote on Thursday 8 November 2018 @ 00:29:
Heel obscuur, maar er gaat vast ooit iemand wat aan hebben
Heb je een pull down resistor gebruikt op de output van de bewegingssensor? Ik denk dat dat je probleem kan oplossen
By
elleP,
vrijdag 9 november 2018 11:41
When dealing with power fluctuations it can also help to add a small (1 ohm-ish) resistor in the power line before any buffer caps. This will make sure your buffer cap is used for the sensor, and doesn't flow back into the processor board.
By
redfox314,
vrijdag 9 november 2018 11:43
I indeed have a pulldown resistor on the output of the motion sensor but in the end it was the capacitor that did the trick.Robin wrote on Friday 9 November 2018 @ 10:13:
Heb je een pull down resistor gebruikt op de output van de bewegingssensor? Ik denk dat dat je probleem kan oplossen
By
-36-,
vrijdag 9 november 2018 19:22
Heel herkenbaar dit, en handig om te weten. Is er een nog reden dat je een foliecap ipv elec. hebt gebruikt?
[Comment edited on vrijdag 9 november 2018 19:26]
By
redfox314,
vrijdag 9 november 2018 19:37
Die had ik in huis, meer niet.-36- wrote on Friday 9 November 2018 @ 19:22:
Heel herkenbaar dit, en handig om te weten. Is er een nog reden dat je een foliecap ipv elec. hebt gebruikt?
Comments are closed