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Motion detector lamp for my dog, which transistor config is suitable?
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FBMinis:
Here is an illustration of what I've tried so far:

https://ibb.co/mXHY0q

Generally understanding how mosfets, PNP  and NPN transistors may work as switches (and using google images for examples), I've tried using IRF520, BS170, PN2222, 2N3904, BC547, etc, but I can get the LED's to be at full power.

I must be doing something fundamentally wrong and I'd like to ask for some advice.

I'm trying to make the LEDs turn ON as my dog passes by to use the tray at night. She's got congestive heart failure and takes diuretics daily, therefore her peeing frequency has increased, including during the night. Gladly she was thought to use the tray since she was  pup..

Thank you in advance  :)
alsetalokin4017:
The PIR module isn't intended to work alone as a switch or transistor driver. It is intended to be used with a microcontroller or other digital interface, before you can switch an external circuit with it.

So you need a little more hardware. The easiest path to your goal is probably going to be using a 3.3 volt Arduino to receive the signal from the PIR module and provide an output signal to switch a mosfet which will switch on your LEDs. The Arduino will allow you to control how long the light stays on, whether it simply comes on at full brightness or fades on and then off, how to ignore false triggering (require PIR signal to be HI for at least x seconds before turning light on) and so on.

This video may help:



So you would basically do this, except the output of the Arduino would drive a logic level mosfet gate through a 10 ohm resistor. The mosfet switches the power to the LEDs.

alsetalokin4017:
You might be able to get it to work in your original simple circuit idea if you use a logic level mosfet, but my confidence level isn't very high. If I could find my PIR module I'd check this out for you... if only.  I know it's around here somewhere....

 |O

alsetalokin4017:
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HB9EVI:
wouldn't it be easier to get a mini led beam with built in motion detector?

PIRs are nice gadgets but to start up programming mcus for this simple project, seems to me quite an overkill - unless, of course it's maybe your dedicated wish to do so
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