Electronic question.

Hello all, I am trying to switch on 80mW red that I have in a display unit using the remote control (infra red).

Here is what I am dealing with:

Input that is controlled by the remote =3V

Permant live to the LD = 6V.

So, I am trying to find a relay type of situation, where the 3V causes the relay or transistor to switch on the 6V feed (or allow the ground connection to work and thus allow power to flow through the LD).

I cannot find a relay with a 3V coil in it, tried to use a 2n3904 transistor (also tried to make a darlington pair...), but it soaked too much power away from the circuit and the circuit failed to move motors and the LD was very very dim

Any ideas?

Thanks in advance guys, Fariniac.

opto isolator? (no research done, just throwing it out there)

Regards rog8811

ah yeah, thought about that. Not exactly sure how they work though tbh.

The input side is an led the output side is an opto transistor, all you need to check is that 3v is enough to drive the input.

Regards rog8811

just done a Wiki search on them, I think it might just work.

Cheers Rog, I am learning little by little. I'll build some big beastie laser system one day

Cheers, Fariniac .

Check your transistor circuit. Here's a schematic I drew awhile back for a transistor switch. It does exactly what you need. Where it says 10V in, you'd put 3V. Replace the solenoid with your motor, and where it says 24V in, you'd put 6V.. You can ignore the 3.3k resistor since it's actually built in to the darlington. For your needs I recommend using a 2N6388 darlington instead of the TIP122. It will easily handle your power requirements.

I'd say going with the opto-isolator method too, that's the simplest and most effective. You break the circuit of the opto-isolator's LED with a phototransistor or photoresistor sensitive to your IR, and use the phototransistor of the isolator to break the circuit of the LD and motor.
The problem here is that you need to be shining the IR at it all the time to work.

To remedy that, you can use the opto-isolator to toggle a small thyristor, which acts as a bistable switch: the isolator connects the thyristor's gate to VCC, which will then allow current forward to the LD and motor as long as you keep it powered. Once you disconnect VCC momentarily, there's a delay, and after that you can use your remote again.

Just my two cents though...

I assumed that the IR receiving portion of the circuit was already complete since it was stated that he is toggling 3V with the remote and made my suggestion based purely on sending the named voltages where they need to go. I would agree that the opto-isolator would be simpler, especially if you don't already have some sort of IR receiver put together.

wow!! it's easier even than that....I totally forgot to meter the gnd side of the board. The 3V circuit is switched on the gnd side.....the 6V gnd is connected directly to the gnd where as the 3V goes through a controller IC on the board. So, I connect the gnd connection from the LD to the gnd next to the 3V and boom...perfect....

Unreal, can't believe I was such an ass......

thanks for your help guys, I actually learned a lot about transistors whilst looking up the information and anytime I learn something, i class as a plus

Fariniac.