PIR LED increase on-time

[g3kk0]

Hi,

I have a small LED light with a PIR sensor that I use at night in the bathroom. It was a cheap purchase off AliExpress and I'm really pleased with it except for one thing. The light only comes on for roughly 20 seconds before going off and this doesn't appear to be adjustable. Ideally I'd like it to stay on for a couple of minutes so decided to take it apart to see what I could do. After some searching online I came across a post that mentioned the on/off mechanism might be driven via a capacitor being charged and discharged. When I looked on the board I could see what looked like a single capacitor so I was convinced this was what was happening. I then attempting to use a few different sized electrolytic capacitors (50V 1uF, 25V 10uF, 16V 220uF) to bridge the existing capacitor (which remained in place) thinking they would hold more charge and the led would stay on for longer but it didn't seem to make any difference. Now I'm thinking either I'm using the wrong capacitors or maybe it's a little more complicated and one of the other chips on the circuit is providing the timer mechanism. I've attached some pictures of the board in question. Any assistance would be greatly appreciated.

Thanks in advance

[bookaboo]

See if you can get the PN off the 8-pin component. Then google the datasheet and share it here. Bonus points for matching the pinout to the other PCB components.

[g3kk0]

I did think about doing that but unfortunately the 8-pin chip has no markings (unless they are underneath the chip?). I'm guessing if I'm not able to identify that chip there's probably not much I can do.

[liaifat85]

Changing just the capacitor might not be sufficient if there are other components involved in the timing mechanism. Experimenting with resistor values in conjunction with capacitors might yield better results.

[Terry Bites]

www.szhaiwang.com/pir_ic/HR008_87.html I've seen this ic a few times.
I imagine others are prety similar. Hunt down the pin with a cap to ground it and try sticking another one in ll.
It'll be the timer or the power pin. Buzzzit out.

[Kleinstein]

The chip seems to be s a different one, as the capacitor is at pin 8 as it looks like.

If changing the capacitor did not change the time, there may be no easy way and the time could be more or less fixed from inside the chip. The is a chance the capacitor is just for decoupling.

[g3kk0]

The chip appears to be different to the one in the datasheet and @Kleinstein is correct with regards to the capacitor being on pin 8.

I've tried adding different sized caps but it doesn't seem to change the behavior so I'm starting to think it's the actual chip controlling the timer.

I will try adding a few different sized resisters as suggested and report back.

[Zero999]

What's on the other side of the board?

Have you tried reverse engineering it?

Is' possible that 8 pin IC is a microcontroller. To increase the on time, you'll either need to put a delayed off circuit between the microcontroller and switching transistor, or replace the microcontroller with one programmed with your own code.