PIR question

[elioacm]

where do i connect properly these 3 pins..

a
b
c

and where the led goes?
can you show me the way to put it on a breadboard?

 

[davenn]

what LED ??

you better explain what you are trying to do
have you googles searched for a datasheet for the PIR ??

Dave

 

[(*steve*)]

A PIR device is non-trivial to use. The voltages are tiny, and since they are used differentially, they also normally require the IR to be focused on them (that is the purpose of those white domes you see in PIR devices.

Oh, hang on, let me fix your post before I do on...

 

[(*steve*)]

Here is an explanation of how they work. I'll be back later with how you use them (I'm sure I had it somewhere...)

 

[(*steve*)]

This page has a simple circuit.

It has a number of problems.

First (and unrelated to the PIR sensor) is the LED in the emitter of the transistor. Remove it if you intend copying this circuit.

Secondly, the output is the differential signal between the two sensors. This circuit only detects a rise in the output, a better circuit would also detect it falling.

The sensor is normally coupled with an IC that handles it much better than this circuit and a dome that does the focussing. The combination is often almost the same price as the bare sensor.

 

[elioacm]

dave, im trying to do a simple obstacle detector that lightens a typical LED when an obstacle is in the way... ive already got the pir sensor.. problem is i dont know how to put it, cause there are three pins (a,b,c) and dont know which one is - + or to proper connect it to a breadboard for it to function with the LED




as what steve showed thanks, i think i needed a transistor and an IC for it to work..
and im only doing 1 sensor. like an obstacle sensor.

 

[(*steve*)]

im only doing 1 sensor. like an obstacle sensor.

A PIR is probably not what you need then.