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Old Jul 07, 2002, 03:36 PM
Registered User
UK
Joined Jan 2001
466 Posts
Looking for a (modulated) IR beam break kit for school project...

I'm looking for an IR beam break kit ... I need one for a school project. I need an IR tx/rx with a logic output ... I can accomodate either a beam break = logic 1 or break = logic 0.

I know there are relay kits available, which could be made give a logic output, but relay current draw would be unnecessaryily high. Plus, I was looking at finding a modulated IR beam for ambient light rejection. I don't think the Maplin kits have this.

Range must be door width minimum ... ideally 1.5-2m.

I've found a circuit on the web here:

http://www.ee.washington.edu/consele...l/proposal.htm
http://www.ee.washington.edu/consele...inal/final.htm

but I would like to avoid a 741 if possible (negative power supply needed and I was gonna use a receiver pack). Plus for some reason it doesn't work on the simulator (crocodile technology).


ANY help appreciated,

Ben
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Old Jul 09, 2002, 08:37 PM
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Shirley, New York, United States
Joined Apr 2002
250 Posts
radio shack

Does england have an equivilent for radio shack? here in the states, Radio Shack has a sharp IR detector, which is a small silver box with three pins. The ir detector will filter out all but 40khz modulated signals. That plus a lens would be a fine detector stage. You could build an emitter stage with a 555, and an infra-red led.

Lots of info on IR detection can be found on Robot news groups and robotics info sites. Many homebuilt robots use IR for obsticle (sp) detection.

-Adam
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Old Jul 11, 2002, 03:26 PM
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UK
Joined Jan 2001
466 Posts
Which Sharp IR module would you recommend?

There are quite a few and I do not know the difference between them.

I need output like this:

- modulated IR beam = 1
- non modulated, always on IR = 0
- broken beam = 0

The reverse would be fine, too, so long as all the above were reversed.


Thanks a lot,

Ben
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Old Jul 12, 2002, 08:06 AM
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London UK
Joined Sep 2001
105 Posts
Modulated IR beam

Have you considered modifying an infra red remote control system. These use a modulated beam. Maplin do a pair of kits number K6708 and K6709 which may be suitable.

Neil
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Old Jul 12, 2002, 05:18 PM
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UK
Joined Jan 2001
466 Posts
Although I still do not fully know the difference between the sharp modules, I think that they are what I want.

But does anyone know where they can be found in the UK? Or an equivalent product made by another company?


Thanks

Ben
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Old Jul 12, 2002, 05:43 PM
Registered User
Shirley, New York, United States
Joined Apr 2002
250 Posts
Ready to go setup

Here's a pre-made board with a sharp sensor on it. This particular sharp sensor is not a break beam, but a object sensor. it's $30.00
All the data is on the page. I'll try to get you some more info on the original sharp sensor I mentioned.

Another option is an industrial break beam sensor. These can be had from banner, or sick optic. Prices are high as these are industrial devices. $100.00 usd is common. However, I've had luck asking for samples when I was young and doing my own school projects.

-Adam
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Old Jul 13, 2002, 12:49 PM
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UK
Joined Jan 2001
466 Posts
I found the IS471F (in the UK!) on www.rswww.com . It turns out to be exactly what I need, a modem with four pins: modulated diode sink, logic out, vcc and ground. The same IC modulates and demodulates the signal - no messy discrete timing circuit, and perfect syncronisation!

Price (ex. diode) 2.90!

[Datasheet]

OK, final question. I'll probably need an IR reflector (either that or have a diode on VERY long wires). Obviously a mirror is no good as it sends light away from the source. What I need is one that uses total internal reflection - just like a bike reflector, in fact.

Would a simple bike reflector work? I assume the red one would be better for infrared (?). Or would I need a special (read: expensive) reflector to get at all decent performance?


Thanks guys,

Ben
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