Need thoughts on IR remote control

[Ratch]

Hey all,

I need to light some leds when a remote circuit is switched on. The leds will be indicators in some "headgear", so I'm striving for maximum space savings.

The indicators I need to light will always be about 3 feet away from the circuit they're responding to, and will only be necessary then, so IR line of sight and obstruction shouldn't be a problem.

So basically, I need the equivelant of a wireless relay. I think I want to avoid RF because of the complicated receiver circuitry needed. But to be honest, I don't know a whole lot about IR modulation and receivers yet, so I don't know if IR would be as complicated. I'm guessing it wouldn't, by a couple simple mod/demod schematics I've seen.

So here's what I'm wondering about:

- Will the transmitted IR signal need to be modulated to avoid false triggers by sunlight or TV remotes or other IR sources?
- Will an IR demod or receiver circuit take up more space than an IC or two, or more than an rf receiver circuit?
- Can the circuit be effective with a simple IR led and IR phototransistor, IR led just turning on as the tx, and the phototransistor seeing the IR as the rx? This is where I'm worried about false triggering.


Also... The IR transmitter (or led) is going to get it's power from a brake light circuit in a vehicle. How can I tap the brake light circuit to get enough power for the IR tx/led without creating a short for the brake light circuit? The brake light is 12v, but I'm not sure what the IR led is rated, probably 2v. Is a series resistor enough for a voltage drop and a current limiter? I'm sure there's going to be math involved...


I'm in the process of learning electronics, although with no real "teacher" and a full time job and family, it's slowwwww going... I've run across this site a few times in the past year, so figured I'd join and ask a question now and then... Some of AudioGuru's comments have stopped me from attempting certain circuits I've found posted here, too...

I appreciate any response!

 

[napalm]

IR is simpler than RF? It depends. If you do IR properly, you'll have to deal with micro controllers, and what not. It could end up being more complicated than RF.

"Can the circuit be effective with a simple IR led and IR phototransistor"
Sure, but there can(read:will) be false triggering.

You say you want this to act as a "wireless relay." In which case, you do realize that the device your activating will only be activated while the IR led is turned on. If you want to flash the led once and have it turn on, than flash in again and have it turn off; you'll have to make a flip-flop switch (very simple).

It would be helpful to know what kind of range you need.
It would be interesting to know what your final product is suppose to be.

My other suggestion (if you want to take the easy way out). Buy a 5$ RC car from walmart. Make sure its controller only has one button (this makes it go forward) Essentially, pressing the one button turns the car on and off. While it's pressed, the car is turned on, aka it moves forward. I'm sure you can figure out how to gut the car and implement it into your project.

 

[Ratch]

The range will be about 3-4 feet.

It's going to be mounted in a helmet, with 3 or 4 other circuits and a battery, so space saving is key. I'm trying to build everything else with SMD and a soldering iron, which is saving lots of space so far (I'm sure more if I soldered them properly).
I have done the remote control car hack, but the receiver is pretty big, and that's what I need to avoid. I originally decided on IR because I was just going to use the IR phototransistor as the receiver and on/off, then started thinking about interference.

This *may* end up being a night time and dusk use only situation, so sunlight IR may not be that much of a problem.

You say you want this to act as a "wireless relay." In which case, you do realize that the device your activating will only be activated while the IR led is turned on.

Yes, no flip flop necessary, I only want the helmet led indicators on when the brake light circuit is energized.