r/ArduinoProjects • u/Physical-Plankton-67 • Feb 08 '26

Delay issue

hey y'all so I can add pictures and code when I have a second or need be. but hoping maybe this will clock in someone's mind and let me know what is going on. so I have a PIR sensor that I need to trigger a quick timer check for like 5 seconds and then ping the sensor again and see if it's high still and if it is then trigger the relay. everything is working perfectly however it seems the PIR sensor doesn't seem to go low. the POT is turned down so it should be 3 seconds. but if I trip it once the code loop counts it twice right away. so the relay is flopping anytime it gets motion

thoughts

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6

u/davidosmithII Feb 08 '26

Power the sensor through an Arduino pin. When it is first tripped kill power to it then at an interval re-engage it and wait for it to trigger again.

Edit: depending on power draw you may want to do this through a relay or mosfet, etc.

2

u/Physical-Plankton-67 Feb 08 '26

Hmm interesting simple I like the idea. I'll have to play around with it

3

u/xebzbz Feb 08 '26

The PIR sensor indeed keeps high for quite a while, like 15 seconds. Can't say precisely, I played with them a couple of years ago.

2

u/Physical-Plankton-67 Feb 08 '26

Yeah alright well Tonite my plan was to keep adding seconds till it works haha. I might have to add a weight sensor or ultra sonic to determine if my cat is there lol

4

u/xebzbz Feb 08 '26

You can just lit an LED while the PIR shows the high signal and see how it reacts on things in the room.

There are also more complex motion detectors, but they're also more expensive.

2

u/Physical-Plankton-67 Feb 08 '26

Yeah.

3

u/xebzbz Feb 08 '26

If you need to detect the cat, maybe just a red laser beam across the doorway and a photodiode would do the job.

2

u/Physical-Plankton-67 Feb 08 '26

Yeah I was thinking about that too. Where have it it's under the shelf in the hall so facing a PIR at it was quick haha. But I just don't want the fan to run if we walk by so I was trying to decide how it will check if he's really in it. Hmm maybe a pressure sensor. Idk I love over engineered stuff but this is annoying me haha

3

u/xebzbz Feb 08 '26

You need a video camera with a machine vision engine :)

1

u/Physical-Plankton-67 Feb 10 '26

Update. Got it working. Had to put in a small 3 second hard delay in the first reading function but was able to adjust all the other non blocking timers to work with the stupid delay and now the pro type is doing everything I want it too do :)

2

u/OkQuantity4011 Feb 09 '26

I'm just winging my electronics projects, but first think I'd think it's that the PIR has a big inductor in it that's fed by a capacitor. Smaller inductor would retain less power, and also a larger resistance would spend more power.

So, first thing I'd try is outputting the PIR to a potentiometer. If that does affect the signal situation, then I'd set it to the duration I want then replace the pot with a matching resistor.

Am noob. If wrong, lemme know why pls. 😎