Can you use two IR transistors and and IR LED to pan a turret?

You would have two IR transistors pointing not quite straight ahead but a little away from each other. They would pan a servo or motor such that they stop when the reading from each Ir transistor was about even, meaning the turret is pointed at the IR led. How far away would that work, roughly, for a normal LED? Are we talking 10ft or 100ft? Has anyone messed with this? If the range is short, is there a better sensor to use besides a camera?

Edit:

What I'm asking about is essentially the same thing as a sun tracker.

except it will need to follow an IR LED or small cluster of LEDs and be much faster on the response time. I know the servo can move much faster but maybe there is something else limiting the speed like the response time of the phototransistor. Do any of you with experience with this stuff thing that it will be able to work with those modifications?

perhaps you could experiment with a tv IR remote control and draw some conclusions.

THat's the same amount of work as building the whole thing. I'd like to know so that I can skip that and use a camera if the range isn't going to be good.

David82:
THat's the same amount of work as building the whole thing. I'd like to know so that I can skip that and use a camera if the range isn't going to be good.

Use a camera for what? You might give more specific info on what you want to do with a camera, and what a camera has to do with "range".

.... I thought it was already clear.

I'll simplify it: What is the range the an IR photo transistor will detect a standard IR LED?

11.537

Really, there is no answer to your question.

What LED?

What photo transistor?

What transistor amplifier?

What do you mean by "detect"?

What ambient light level?

What nearby reflecting surfaces?

etc..

etc ...

And how do you suppose a camera would be better?

Even if the photo-transistors could respond to light from the LED would there be sufficient difference to allow you to use the difference to control direction?

How accurately do you want the direction to be controlled, +/- how many degrees?

I don't think your project is at all simple and you will probably need a lot of experimentation which may ultimately fail.

...R

By any chance are you reffering to laser targeting? To where to point the laser and the turret follows.

Robin2:
What LED? a standard size IR LED

What photo transistor? an standard IR phototransistor

What transistor amplifier? none

What do you mean by "detect"? have an analog output a value different from it's previous value

What ambient light level? typical office lighting or darker

What nearby reflecting surfaces? none

There you go, it's still simple. I just want a response from someone who has already worked on something similar.

HazardsMind:
By any chance are you reffering to laser targeting? To where to point the laser and the turret follows.

nope. Just Just use the balancing of IR phototransistor values to pan a turret toward an IR LED. Really simple stuff. Someone has to have already done this before..

I just want a response from someone who has already worked with these parts.

Which parts?
You haven't specified any parts.

So the turret will center itself?

OK, here's the answer you want to hear: it will work and it will be effective, and you probably don't need a processor to do it.

Now, what are you going to do about seduction by other environmental sources of IR?

AWOL:

I just want a response from someone who has already worked with these parts.

Which parts?
You haven't specified any parts.

You're being unnecessarily picky. The level of detail you're asking for isn't relevant but just so you can get over this mental block, here are parts for you: RadioShack.com Official Site - America's Technology Store They don't matter though because the difference between these parts and other IR phototransistor and IR Leds of the same size is obviously negligible.

AWOL:
OK, here's the answer you want to hear: it will work and it will be effective, and you probably don't need a processor to do it.

Now, what are you going to do about seduction by other environmental sources of IR?

What are the other environmental sources of IR light in an office environment? If they exist, then where is an IR LEd emitter/detector pair that use a spectrum that is not typically found?

What are the other environmental sources of IR light in an office environment?

Well, it's a 150 million kilometres away, but it's a biggie.

If they exist, then where is an IR LEd emitter/detector pair that use a spectrum that is not typically found?

Illuminators used for IR number plate recognition systems are necessarily heavily filtered to eliminate environmental IR.

AWOL:

What are the other environmental sources of IR light in an office environment?

Well, it's a 150 million kilometres away, but it's a biggie.

If they exist, then where is an IR LEd emitter/detector pair that use a spectrum that is not typically found?

Illuminators used for IR number plate recognition systems are necessarily heavily filtered to eliminate environmental IR.

Come one man. This is indoor only. I know the sun would totally mess it up. The things you're referring to are all outdoor issues. Let me be even more unnecessarily clear; In a gigantic, building sized box, with fluorescent lights, how far away can a slowly blinking IR led be to register a change in value on the IR receiver as it blinks on and off?

unnecessarily clear;

I'm sorry, I don't understand that concept.

unnecessarily picky.

Ditto.

It's taken fifteen replies to get even a quarter decent statement of requirements.

The RadioShack "spec" quoted only spectral sensitivity.

You aren't going to know the answer to the question unless you've experimented with a similar project. Trying to speculate without the necessary experience is a waste of both of our time.

David82:
You aren't going to know the answer to the question unless you've experimented with a similar project. Trying to speculate without the necessary experience is a waste of both of our time.

I agree. Better you waste your time than mine, but that being said, the farthest I can get from my tv line of sight is 33', and my IR remote still works.

You aren't going to know the answer to the question unless you've experimented with a similar project.

I have.
I used some very large area detectors, optical filters and a modulated source.
Mostly analogue electronics (747 op-amps).
The answer? Around 6 metres, to within about 10 degrees, which was good enough, but the slew rate of the servos was the main limiting factor.