Looking for a (modulated) IR beam break kit for school project... - RC Groups
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Jul 07, 2002, 03:36 PM
Registered User

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:


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,

Jul 09, 2002, 08:37 PM
Registered User

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.

Jul 11, 2002, 03:26 PM
Registered User

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,

Jul 12, 2002, 08:06 AM
Registered User

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.

Jul 12, 2002, 05:18 PM
Registered User
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?


Jul 12, 2002, 05:43 PM
Registered User

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.

Jul 13, 2002, 12:49 PM
Registered User
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!


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,