Electronics > Beginners

Photoresistor delay

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kovrob:
Hello!  I have an XH-M131 type photoresistor relay module, which otherwise works well, but I would like to delay the on and off time so that it is not disturbed by possible short-term flashes at night or short periods of darkness during the day.  For now, I have decided to connect a capacitor in parallel in front of the photoresistor for its output.  As far as I know, there should also be a resistor in series with the capacitor.  Does anyone have an idea how to solve this?  I just want a delay of a few seconds

RJSV:
   Your delay time, say 3 seconds, is a loooooong time, in electrical terms.  I looked at a couple of videos it looks like a useful module, including an AC Mains relay.
   Obviously (I hope) you mean a 'delay' right at the sensor end but would be helpful to see or describe in more detail.  But I believe any practical delay wouldn't be more than a fraction of a second...like 400 milli seconds. 
   So in theory you might be able to get it to ignore the really fast stuff going on, the requirement to 'ignore' longer dark periods is likely going to need a processor, with code written to have the long delays.
   But that's part of it, you also need to consider that the (lethal !!!) AC Mains relay output doesn't lend itself to additional delay...circuit would have to operate using AC 240 Volts in and out.
   You might be able to trick up a custom Arduino or other processor to manipulate the LDR input (that's light dependant resistor), and supply an input to the XH-M131 according to your wishes, but by that time that's a lot of
work !  Essentially the processor output would mimic a LDR sensor (resistance) so the XH-M131 thinks it's an LDR.

Zero999:
It's a bit difficult without the schematic. I Googled and found different possible schematics for the XH-M131. Some use the LM393 and others the NE555.

A capacitor across the photoresistor will do, but to ideally, you need to reverse engineer it. What IC does it use?

Jwillis:
I' have not come across any  XH-M131 Modules with 555 timers. The only ones I have are LM393. The only others that are marketed as XH-M131 are actually HCW-417 and they have a LM339 and a CD4541 used for a delay timer. If you have a XH-M131 with the LM393, putting a cap in parallel with the LDR will delay the ON time but not the Off time. The time delay is 47uF per second . 100uF is about 2 seconds. Resistor in series won't  change Off delay, only the On delay. To high of a resistor and the unit won't switch because the LDR becomes ineffective.

kovrob:
Thank you for your answers. I have a unit with LM393, it seems.  Currently, a 2200 uF capacitor is connected in parallel and the switch-on takes place with a delay of about 3 seconds.  I also tried a 470 uF capacitor, but that only got about 1 second. In this video, it also works with a smaller capacitor.  I don't understand why I had to use such a large capacity.

https://youtu.be/B_YgOITXyM8?si=mn9DNoYusKLaPTdM

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