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IR Robot Control Answered

The cheapest way of wirelessly controlling a robot is IR, right? I'm in need of help for a schematic for an emitter and a reciever (this will be my first IR project). Please don't tell me to google it because I've been looking around and all I've found were vague schematics. I'd probably want to use a 555 timer for the emitter, but the schematics were vague again. For the reciever would I have to use 4, along with 4 emitters to drive 2 motors independently? As in Motor1 front and back, Motor2 front and back?

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zachninme (author)2007-12-20

You do realize, you have to encode it using serial? You can't have 4 different IR recievers, they'll all have the same value :P

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guyfrom7up (author)zachninme2007-12-20

my plan was that all of the IR emitters and recievers work at different frequencies

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gmoon (author)guyfrom7up2007-12-21

Sounds like a pretty challenging project...

From what I see, you're trying to build 4 independent discrete IR transmitter and receiver pairs. And they will function without any digital encoding/decoding?

Questions:

1) different frequencies -- light frequencies or pulse frequencies?

Comments:

--How do you intend to detect the IR signal? Simple for one IR LED and photo transistor pair, since it's a continuous on/off.

More complicated for several 'channels.' Easy to find differing wavelength LEDs; tougher to find a receiver that can filter out the others... Optical filtering is an option, I guess.

But that doesn't deal with ambient light very well (OK for night use.) So a standard 38KHz Infrared Detector Module works better (you need to modulate the LED at that rate, too.) These are really intended to send/receive digital serial data, and they work pretty well (line-of-sight, of course.)

There may be other modules with different receiving frequencies, but not many I've heard of (and they might be much more expensive, as this is the standard.) And there are inherent limiting factors at play--brightness of the pulse, the wavelength itself, etc.

The upshot is it's pretty hard to do this in a purely analog way. If you could go the digital route, it would make the transmitter/receiver simpler, at least (if not the encoding / decoding / motor-driving.)

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guyfrom7up (author)gmoon2007-12-21

well, if I can get your guys approvale that this might work, heres the plan: taking a quad 555 timer (i forget what they're called), have a circuit so that it pulses 4 IREDs at different frequencies, which could be fine tuned using 4 different potentiometers. The recievers would be 4 different recievers that only conduct at the certain frequencies.

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gmoon (author)guyfrom7up2007-12-21

One problem will be crosstalk from pulse overlap. You'll get errors, as pulses from two (or more) LEDs will combine to create longer pulses (that match neither of the transmitting LED freq...) The more channels, the more summing....

The recievers would be 4 different recievers that only conduct at the certain frequencies.

Which is harder than it sounds, with an analog approach....You still haven't explained how you plan to detect the pulses.

If memory serves, I built a ring-modulator years ago using a 565 phase-locked loop. But an even simpler PLL device is the 567 tone decoder. I bet one of those could be used like a 555 in reverse....In fact, you might use one as an ultrasonic decoder--probably more reliable than IR, and not so much a line-of-sight device...

Regardless, it would probably work with a phototransistor, too (but you might need to feed the signal into an opamp, first...)

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guyfrom7up (author)gmoon2007-12-21

I think my best solution is this 25 dollar device this guy sells on ebay that is basically 4 remotley controlled switches that works over 600 feet away. I could make it so I could use it with a lot of projects. The only problem is that it takes 12 volts, which means more batteries.

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gmoon (author)guyfrom7up2007-12-21

At that price, it sounds like a winner

I've used the Liapac RC modules, but for those you still need a encoder / decoder pair (buy, or make your own w / microcontrollers.)

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Goodhart (author)guyfrom7up2007-12-21

LM558 is the quad 555 timer.

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zachninme (author)guyfrom7up2007-12-21

Good luck with that -- although you *do* know that they'll be some "pulses" where they'll all match up... right?

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guyfrom7up (author)2007-12-20

actually i'll just buy this 25 dollar thing on ebay that works hundereds of feet away and has 4 switches.

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guyfrom7up (author)2007-12-20

also, would IR be the best solution? Is there a better, easy, or cheaper solution?

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guyfrom7up (author)2007-12-20

actually, do you think that I could use my psp running IR shell to control it? All I would need to build is the reciever then. For those who don't know, a feature of IRshell is that it can make your psp a remote control for a tv. using a simple program I could make it put out different frequencies when I press different buttons.

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Goodhart (author)guyfrom7up2007-12-20

I am unfamiliar with that. It looks possible.

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Goodhart (author)2007-12-20

I can't promise a schematic, but a PWM would serve better as creating the Pulse frequency

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guyfrom7up (author)Goodhart2007-12-20

I just found this
http://robotroom.com/Infrared555.html
think it's good?

Still don't know what to do about the reciever, because all the ones I've seed just drive an LED, I need a motor.

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