How Can I Ensure Each IR LED Activates Only Its Corresponding Phototransistor?

[univeruser]

RC stands for remote control, but where in the situation I have no radio transmitter, it was only reasonable that I had better used IR LEDs and phototransistors for the receivers.

I'm only 12, have a restricted budget of no more than $30, and less time on hand. In fact, school resumes on the 17^th of January, 2009, and I won't be working on all this stuff. So if anyone replies, please study this question carefully.

So now I have a remote control, IR, of course. I know how to complete a circuit with a switch, using an IR phototransistor, a 330 Ω resistor, and of course the cell.

So now say I have made a small car using cardboard wheels and a cardboard base. In fact, I'd probably use wood for the same. Here is the question: I need two motors to activate different sets of wheels. I have taken two IR LEDs for their respective two phototransistors on the receiver end. How do I make sure that one IR LED only activates its respective transistor? Should I buy the diodes in sets, from different shops?

And if this bungling should happen, and I prefer to use one IR and another UV LED, I have my second problem here. The problem is that I find only UV photodiodes and not phototransistors. Please help me with this, either by posting a schematic diagram explaining how I make a switch with a UV photodiode and the place where you get them with the UV LEDs as pairs, or by routing me to a site where you find pairs of UV phototransistors and LEDs.

 

[Bob S]

Just use two phototransistors activating two motors on separate wheels on a "bug". My "bug" is powered by two AA cells in series. When I shine a flashlight at it, the "bug" turns toward the flashlight and follows it around the room. What current and voltage do your motors need? Why do you want to use UV photodiodes?
Bob S

 

[BenchTop]

If the question is how to get the motors on separate channels -
and if you intend to use an ordinary IR remote controller, like for TV's and such-

the way those work is that each button causes a serial code to be sent (in the ones I've used) on a 32KHz 'tone' (the IR LEDs are modulated at 32KHz and send pulses of that).
One of the commercial integrated circuits for decoding that is available from digi-key or jameco or mouser, usually. It may be found by looking for 'garage door opener IC'.

Cheap 'tricks' for simpler control are done with an 'escapement' which is essentially a rotary switch that has each individual control in sequence and you just click through very fast on anything you don't want it to pause on.

If you like the idea of 'homing on a target' that was described by the previous poster, that is the simplest route of all - and totally fun and rewarding.

 

[univeruser]

For receiving different pulses of IR radiation, I may require a microchip, and since I am not experiences with these devices, I know less on how to work upon them.

I instead think that I shall get one pair of an IR LED and phototransistor modulated to about 65KHz, and another pair of a 40KHz IR LED and a corresponding phototransistor. Please let me know where I can find them online.

And if this wouldn't work, or may interfere with each other's signals, alternately you can let me know where I may find UV LEDs and a corresponding phototransistor. To be precise, in fact, using UV controls opens up distance control from about 10 metres or so, and opens up whole new possibilities, like remotely controlled toy airplanes, and so on.

I have also been wondering, why shouldn't there be any phototransistor that picks up only visible light? And similarly, only respond to its respectively coloured LED, say, green?

 

[SystemTheory]

You might be best off trying to hack an existing IR tx/rx from an inexpensive toy:

http://dealspl.us/product/new-super-wall-climber-remote-control-mini-car-w-infrared-controller