problems getting a PIR to turn a motor.

Thread Starter

Maloney

Joined Jan 7, 2010
8
So i need a PIR sensor to turn on a motor for me, But its not turning it on. I am able to get an led to light, but whenever the led it replaced with the motor, it doesnt turn. Also if i had the led working, and then add the motor in in parallel, the led stops working. I had the setup with the led and servo both working earlier, but had to disconnect it to fix the connection, and now it doesn't work. Can somebody draw me a schematic for how it should be wired for it to work? Ive tried high and low output, 3v and 4.5v and i cant get it to work again. thanks.
 

SgtWookie

Joined Jul 17, 2007
22,201
You probably burned it up.

PIR sensors aren't designed for a heavy load like a motor; just small loads like an LED. If you want to drive heavy loads, you'll need to use something like a Darlington transistor or a power MOSFET. The current sink/source from the PIR must be limited.

It would help quite a bit if you posted the datasheet for the PIR in question.
 

Thread Starter

Maloney

Joined Jan 7, 2010
8
Not sure of what brand it is, i had it sitting around. However it is definitely not burned out. I hooked it up to a transistor to use as a switch, and with the led connected it works perfectly, but when the motor is connected it spins the whole time. This i have absolutely no clue why its doing that, I was thinking about adding a relay to the circuit but am unsure if that would even make it work properly.
 

SgtWookie

Joined Jul 17, 2007
22,201
OK, so post a schematic of how you connected it up to make it work with the LED, and then again how it doesn't work with the motor.

What transistor were you using, what value of base resistance, etc.

It doesn't have to be a work of art. You can draw it on paper and scan it if that's easiest for you.
 

Bernard

Joined Aug 7, 2008
5,228
KC7783 PIR, pops up quite often. 4-12 V operating V, @ 400uA @ 5V, 1/2 sec minimum positive pulse width. Special output pulse width can be requested.TTL compatable.
PIR with driver & motor can self re trigger with poorley regulated V supply.
 

SgtWookie

Joined Jul 17, 2007
22,201
OK, so tell us more about this motor.

What is it's voltage and current rating?

Are you sure that it's a DC or universal motor?

How many wire leads does it have?

Do you have a manufacturer and model number for it? If not, where did you buy it? Link to online supplier's model would be good.
 

gerty

Joined Aug 30, 2007
1,250
since you don't have a base resistor to the transistor, you'll probably need a new transistor.
 
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