IR Phototransistor distance sensor/proximity

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#1
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Hi everyone,

I have a project using an atmega168pa, and I want to be able to use a gpio pin with some sort of phototransistor/photodiode sensor to detect proximity. I was thinking of using a TCRT1000 http://za.rs-online.com/web/p/ph...
My idea so far is to somehow convert the analog signal from the phototransistor to a pulse train that I can then drive the gpio with. what I would like is for like a 1khz signal at far away and 10khz or so at hard up close and naturally everything in between. I dont just want an on/off sensing ability but want to be able to detect how far away the the sensor is from something, ideally up to a 4cm range minimum. I was thinking of perhaps driving a 555 timer and then interfacing the output of that to the atmel ?
What are your thoughts on this, do you have any suggestions ? I have not been able to find any ready made schematic ideas for this, so if you guys can suggest anything, it would really help.

Thanks in Advance,

Steed.

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Steed,

Your description fits this ...

http://www.maxbotix.com/Ultrason...

Ross McKenzie ValuSoft Melbourne Australia

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How close is "close" and how far away is "far away"?

Is close mm, cm, m, km?

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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valusoft wrote:
Steed,

Your description fits this ...

http://www.maxbotix.com/Ultrason...

Yes, I was also thinking of something like that, but the price is prohibitive. I need to have about 8 channels like this. In theory the ir solution could be less than $2

Last Edited: Tue. Oct 9, 2012 - 04:57 PM
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valusoft wrote:
Steed,

Your description fits this ...

http://www.maxbotix.com/Ultrason...

Yes, I was also thinking of something like that, but the price is prohibitive. I need to have about 8 channels like this. In theory the ir solution could be less than $2

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ka7ehk wrote:
How close is "close" and how far away is "far away"?

Is close mm, cm, m, km?

Jim

As I said above, I am looking at about a 4cm distance max

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4cm is too close for ultrasonic, anyway.

IR tends to be "is something present or not" kind of sensor. It does not determine distance, easily.

Does it have to be passive? That is, can you have something on the object to be detected? Like a reflector?

How rapidly does distance change? Does the object always approach the sensor from the same direction? What is the direction of motion - radial or laterally past the sensor (from one side passing to the other side, as if on a conveyor belt)?

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Hi everyone.

Thanks for your help. I have decided to experiment with qtouch rather, as this was supposed to detect fingers. The capactive touch has the added advantage that the material the sensor is behind does not need to be transparent.

Thanks,

Steed

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Quote:
this was supposed to detect fingers
Still attached to the hand or not? :wink:

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

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