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Author Topic: Range finding Sensor  (Read 1981 times)

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Offline elixierTopic starter

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Range finding Sensor
« on: August 16, 2007, 11:26:13 AM »
Can anyone plez suggest me how to build a range finding sensors with the help of a 555 timer and a TSOP1738.
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Offline Soeren

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Re: Range finding Sensor
« Reply #1 on: August 16, 2007, 10:27:42 PM »
Hi,

Can anyone plez suggest me how to build a range finding sensors with the help of a 555 timer and a TSOP1738.
Quite a tall order. You could make an in range/out of range sensor that way, but not a real range finding sensor to reliable report distance.

A thing to note about some IR-receiver modules, among them the TSOP17xx, is, that you cannot use a continuous wave, as this will be filtered out as an error signal (makes sense when you think of what they're designed for).

From the data sheet:
After each burst which is between 10 cycles and 70 cycles a gap time of at least 14 cycles is necessary.
For each burst which is longer than 1.8ms a corresponding gap time is necessary at some time in the data stream. This gap time should have at least same length as the burst.

So, to use a TSOP1738 for your purpose, the best strategy is to use eg. 1ms bursts with 1ms pauses.

Some IR-receivers takes this error suppression a bit farther and won't even allow such a repeated signal with no variance, but I don't recall if that's the case with the TSOP17-series.

For best result, you need a 950nm IR LED, if using eg. an 850nm wavelength, the sensitivity will be down to approx. a third.


All that said, you'd only get a go/no go reading, but if that's all you need, it's fairly easy - although a 555 alone won't be able to make the burst/pause signal.
Regards,
Søren

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Offline Admin

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Re: Range finding Sensor
« Reply #2 on: August 21, 2007, 03:05:22 PM »
Just out of curiousity, why not buy one for $15?

Offline TrickyNekro

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Re: Range finding Sensor
« Reply #3 on: August 22, 2007, 03:55:08 PM »
If you had a Basic Stamp you could use zone detection!!!
Try to oscilate your IR led from 37kHz5 to 42kHz.... to get zone detection and possible follow capabilities!!!

Also google for: IR range finder vs Sonar... Someone about a year ago has done this test and possibly includes schematics!!!

Have fun
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Greece
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P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

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