IR Phototransistor wiring help needed

Hello, well i am making a small remote control car that will only go forward. Pretty basic, and no arduino code, just hardware. So on the car end, i will have 2 AA batteries driving a 3watt motor with a infrared phototranistor wired into the circuit as well. on the remote control end i will have 2 AA batteries hooked up to a push button, 24ohm, 1/2 resistor and a high output infrared led.
here are the two components:

my question is, on the car end, how should i wire it so that enough power gets to the motor to run the car, yet the phototranistor doesn't get damaged (can it?) and it allows the motor to get enough power to move the car.

I would like it to be a simple circuit, no coding or arduino involved, just simple circuit components preferably found at radioshack.

Cheers, Ryan

sorry, it's a 22ohm, 1/2 watt resistor with a 5% tolerance

here is what i tried and it doesn’t work if someone needed a visual


A phototransistor cannot pass current sufficient for a motor - well, not for very long.

could you please tell me how i could improve my circuit so it would then?


You need to get the photo transistor to turn on a power transistor to switch on the motor.



You'll need a lot of stuff, resistors being the least of it.
That phototransistor will turn on in the presence of IR and likely most visible light unless you have a decent IR filter for it.
That's why you see this 38kHz IR detector stuff - it's more immune to ambient light; it responds to an modulated infrared signal not mere infrared stimulus (it's possible to "swamp it" with the equivalent of an infrared flashlight or something, but that's a side issue.)

Look here -- Arduino Forum
for some practical information on how to get a handle on your phototransistor.


I was wondering if this curcuit will work

What circuit?

hahaha, dumb me..... i forgot to upload the picture.
Well here it is, sorry!



I was wondering if this curcuit will work/ what to do to make it work.
The purpose is for the motor to turn on when the IRPT senses IR light and turn off when it doesn’t sense the light.
Also i would like to know where to connect the emitter, base and collector ends of the npn transistor on the circuit.


Try something with a relay. The relay is activated/de-activated by the phototransistor, but the motor goes through the relay contacts.


It helps if you use the same electronic symbols as the rest of the world, if you want your circuit understood by the rest of the world.
Your transistor has no means of identifying the terminals, there is a line with an arrow not going through the resistor symbol close to it and there is a triangle which I assume is your photo sensor but only from the fact you are asking about one and that is the only symbol left it could be.

I think the whole idea is flawed because the range you will get with that sort of circuit is only in the order of a foot if you are lucky. Will that be good enough?

To avoid anyone else wasting time answering the same question in two places, I've merged these two threads.

@OP, do not crosspost