Vikash, your electrical expertise is needed

Splinter · Post by **Splinter** » Wed Apr 05, 2006 4:28 am

Could you throw together a simple IR repeater circuit design for me?

Basically it takes an IR signal from a remote control, and repeats the exact single from an IR led at the end of a lead

It should run off 11-14v dc

I'll owe ya one

vrg3 · Post by **vrg3** » Wed Apr 05, 2006 5:23 am

Well, there are a couple ways to do this. One is to just build a dumb signal repeater -- have an IR detector, and amplifier, and an IR emitter, and hope the signal makes it through okay. You'd probably have to do some adjusting to make this work, and it probably wouldn't be very robust with respect to variations in ambient light, but it would be easy to build. Perhaps a better way would be to demodulate the signal and then modulate it again; for this you need to know the carrier frequency of the remote; for most remotes it's somewhere around 36 to 40 kilohertz. Which do you want to try?

Also, depending on the situation, you might consider just desoldering the IR receiver modules from whatever device you're trying to control and extending it with a shielded cable. Usually there are three leads. Or even just set up some mirrors.

What device exactly is this for?

vrg3 · Post by **vrg3** » Wed Apr 05, 2006 6:18 am

It's a little more expensive than trying to do it yourself, but maybe you'd just want to buy this:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 9707761587

Splinter · Post by **Splinter** » Wed Apr 05, 2006 6:26 am

Well its for my carPC

Ive got a remote control that works with windows, and have programmed it to work with my frontend software, which is great. However Ive got the receiver in the dash right now. Its fine for when Im sitting in the drivers seat, but if Im outside the car, it only works from a few angles.

I wanted to mount a receiver somewhere in the ceiling, and have it rebroadcast to somewhere visible to the dash receiver.

vrg3 · Post by **vrg3** » Wed Apr 05, 2006 6:29 am

Ah.

Can you just hook up a second receiver?

Splinter · Post by **Splinter** » Wed Apr 05, 2006 6:43 am

No

It runs on USB, and they're more expensive than actually buying a repeater

Plus, Im not sure how the software would handle that. Ghost signals could end up getting doubled.

vrg3 · Post by **vrg3** » Wed Apr 05, 2006 6:55 am

Ah.

So do you want to try a DIY dealie? Or are you just gonna buy a cheap commercial repeater?

Splinter · Post by **Splinter** » Wed Apr 05, 2006 7:57 am

I'd rather do a DIY, for a few reasons

Size (no bulky casing to deal with) and cost, mostly.

vrg3 · Post by **vrg3** » Wed Apr 05, 2006 4:01 pm

'Kay, so which type of repeater (dumb or demodulating/remodulating) do you want to try?

Splinter · Post by **Splinter** » Wed Apr 05, 2006 4:07 pm

I did find a 40khz remodulating repeater online, and it looks tricky and possibly expensive.

http://www.discovercircuits.com/PDF-FILES/40kvcr.pdf

But I can see how a dumb one could end up not working very well or at all.

vrg3 · Post by **vrg3** » Wed Apr 05, 2006 4:14 pm

Huh.

That appears to essentially be a dumb repeater but with a band-pass filter to attenuate frequencies outside the 40KHz band. Interesting. Kind of a compromise.

That's actually a fairly simple circuit. If you don't feel confident about your ability to build something like that, then you probably should bite the bullet and use a commercial repeater.

But let me draw up an actual remodulating repeater for you...

Splinter · Post by **Splinter** » Wed Apr 05, 2006 7:58 pm

The circuit itself doesnt look that complicated, the difficult part for me would be sourcing the parts cost effectively.

vrg3 · Post by **vrg3** » Wed Apr 05, 2006 8:32 pm

Okay, well here's an idea then:

http://www.graphics.cornell.edu/~v/pics/ir_repeat.png

The basic idea is this:

Use an LM7805 to produce a stable 5-volt power supply.

Use an ECS 1.2288 MHz oscillator to produce a clock signal.

Use a 74HC590 to divide that frequency by 32, producing approximately 38 KHz.

Have the output of a SHARP GP1UD261XK0F IR receiver module (which receives and demodulates the signal) toggle the 74HC590's output-enable, thus remodulating the signal.

Have the 74HC590 drive an LNA2903L infrared LED.

You should be able to order these parts from Digi-Key. I don't know how much they charge to ship to Canada, but I know that they do ship to Canada and the parts add up to around 5 US dollars.

I just drew this up right now, so it might or might not work. I've never tried doing this myself. Seems like it might be worth a try though.

Splinter · Post by **Splinter** » Wed Apr 05, 2006 8:37 pm

Awesome, Ill check the prices at a local supplier and see if they're compairable, if not Ill order them and see how it goes

cheers!

Additional:

Could I run additional sensors wired in parallel?

vrg3 · Post by **vrg3** » Wed Apr 05, 2006 9:06 pm

Umm, mmmmmaybe. It would depend on the particular IR receiver module. I do believe this one uses an open collector output with a pull-up resistor, so it should be possible to parallel two or more of them. Most probably do.

If you're looking at other suppliers, keep in mind that almost any IR receiver module meant for this frequency band should work. Even Radio Shack carries a cheap one.

Similarly, almost any IR LED made for remote controls should work.

And 7805s are plentiful, and 74HC590s are almost as plentiful.

The only part here that your supplier might not be able to get is the oscillator.

Tleg93 · Post by **Tleg93** » Thu Apr 06, 2006 2:49 pm

You should probably wire them in the fashion of a wheatstone bridge.

vrg3 · Post by **vrg3** » Thu Apr 06, 2006 2:58 pm

A Wheatstone bridge?

These receiver modules aren't simple transducers; they actually demodulate the signal and output a TTL square wave.

Tleg93 · Post by **Tleg93** » Thu Apr 06, 2006 3:01 pm

I was just cracking a joke, sorry. But seriously, can't you find all kinds of IR sample circuits out there on the net?

vrg3 · Post by **vrg3** » Thu Apr 06, 2006 3:11 pm

Oh, hehe...

Yeah, actually, you can find some, like the one Splinter found...

I do kind of like that my idea uses integrated parts so it seems like there will be very little to worry about when building it. No transistors to bias and no exposed crystals to shield.

Splinter · Post by **Splinter** » Wed Apr 26, 2006 8:56 pm

So the total cost incl. shipping for the parts was 29 CAD

Thats including 4 voltage regulators I ordered for a different project though

vrg3 · Post by **vrg3** » Wed Apr 26, 2006 9:07 pm

For my design?

Good luck building it!

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Vikash, your electrical expertise is needed

Vikash, your electrical expertise is needed