Sharp GP2D120 ir sensor range

Discussions around autonomous, semi-automatic and intelligent robots and systems.

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BeligerAnt
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Post by BeligerAnt »

You can use a photo-transistor as a crude light-sensitive switch. It would really benefit from going into a Scmitt-trigger input to ensure clean switching.

A standard 5mm IR LED should be fine for the source, you can adjust the power by changing the value of the series resistor. You can also adjust the sensitivity by playing around with the value of the collector resistor on the photo-transistor.

One important point is to shield the photo-transistors from the LEDs. You will need a solid barrier between them because both have significant sideways sensitivity/output. Heatshrink tubing over the LEDs works well, but you might need a couple of layers.

I have used sensors like this for edge and opponent detection on my mini-sumo robot and they work quite well. I will dig the circuits out and post them, but it may not be until the weekend.

BTW a good source of cheap/free matched LEDs and photo-transistors is old/dead mice - the old ball type have 2 pairs of LEDs and transistors.
Gary, Team BeligerAnt

Andrew_Hibberd
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Post by Andrew_Hibberd »

Going a little backwards, alasdiar are you going to Richmond tomorrow? I have a sharp 10-80cm range sensor we can play around with.

If you set up an LED with a variable resistor in parallel to adjust the brightness, then use a photo resistor into one of the analogue inputs that would give a fairly simple sensor.

http://www.acroname.com/howto/photoresi ... istor.html
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alasdair
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Post by alasdair »

Thanks Guys.
The switch was meant to be simple, so that work great. I will put heatshrink over it to stop direct light. a potentiometer is a good idea, that would help me fine tune it.

I am going to richmond tommorow, so that would be great.

:D I am now tryiing to find the right range IR LED and IR phototransistor. Why do you think a transistor would work better thtan a photdiode, becaue i only need to turn it on and off?

alasdair
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Post by alasdair »

I have 2 of these (the transmitters):

http://www.maplin.co.uk/Module.aspx?ModuleNo=10379

I think they will work, if i add in the right resistors to change the amps. I do not know the range: Does anyone know? (i dont have much experience with infrared, so i do not know all the mathematical stuff). I think if they are the right range that they will do the job.

Andrew_Hibberd
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Post by Andrew_Hibberd »

Ah I read gary's post very quickly this morning. A photo-transistor would be better to use than a photo-resistor and would directly replace the micro switch, as it gives a digital output.

There is alot of information out there, google brings up these:

http://www.optekinc.com/pdf/App%20Bulle ... mblies.pdf
http://www.discovercircuits.com/DJ-Circ ... otonpn.htm

Most electrical suppliers should sell what you need:

Maplin
http://www.maplin.co.uk/Module.aspx?ModuleNo=17936
and an IR LED http://www.maplin.co.uk/Module.aspx?ModuleNo=2262#spec
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alasdair
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Post by alasdair »

Thanks andy.

I have found that the range of the infrared emiter i have is approx. 5 meters! A bit long! I need something like 4cm!

slurp
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Post by slurp »

I found this quite some time ago (it's helpful to Minisumo too):-

http://www.micromouseonline.com/files/m ... arratt.pdf

It's one approch to IR wall detction.

Best regards,
colin

alasdair
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Post by alasdair »

slurp wrote:I found this quite some time ago (it's helpful to Minisumo too):-

http://www.micromouseonline.com/files/m ... arratt.pdf

It's one approch to IR wall detction.

Best regards,
colin
Cheers Colin. That was an interesting approach which i may look into with another mouse, but i think that this one will be simple, as i already have boards.

This question is aimed at peter: Where do you get those boards which you use as edge sensors on your sumo? If i can find the specs then i may use them as wall sensors on my mouse.

The new mouse is going to be called:
Hellbound 2- To hell and back again. :evil:

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peterwaller
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Post by peterwaller »

When you say board if you mean the PCB I etch them myself the component I use is
http://www.maplin.co.uk/Module.aspx?ModuleNo=12709

alasdair
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Post by alasdair »

peterwaller wrote:When you say board if you mean the PCB I etch them myself the component I use is
http://www.maplin.co.uk/Module.aspx?ModuleNo=12709
For some reason the maplin site is down. :cry:

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