Subject:
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Re: expansion board
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Fri, 14 Feb 1997 18:59:30 GMT
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Original-From:
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Bill Richman <bill_r@inetnebr*NoMoreSpam*.com>
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Reply-To:
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bill_r@inetnebrSPAMCAKE.com
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Viewed:
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1400 times
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I used the one available IR LED driver on the HB to drive a Radio
Shack high-output IR LED. This, along with a Radio Shack IR decoder
module (a little silver box about the size of a sugar cube that takes
+5vdc and ground, and outputs a TTL level signal whenever it sees IR
modulated at 40Khz) on my robot that I'm working on, works
great. It can detect my hand at about 10-12", and even dark-colored
cloth objects at several inches. I went out and bought several more
LEDs and detectors recently, and found that the new detectors (which
are a slightly different style) can only see the LED output if
they're directly facing each other from a few inches away. I checked
the output frequency of the HB IR driver, and found it to be around
53Khz. The old IR detector modules seemed to have a center frequency
around 40Khz, with a fairly wide margin for error on either side of
that. The new modules seem to be a lot less forgiving in the
frequency they will accept, so I may have to either tune the values
of the components in the IR transmitter driver on the HB, or build my
own using a crystal or resonator to keep the frequency more precise.
I was planning on putting a detector at each corner, in front and
back, and a transmitter in the middle of each end. I wrote a little
routine that turns the IR transmitter on and off in a semi-random
pattern, checking each time to make sure what the receiver is
detecting matches the on/off state of the transmitter. If it makes
it through 5 or 6 of these random on/off cycles, I count it as a
valid reflection detected. I thought I would have to play with it a
lot to make it reliably detect its own transmissions and ignore
outside IR interference, but it works flawlessly so far. It *always*
sees its own reflection, and has *never* falsely triggered. I've
tried pointing it at various types of lights, pointing several
different TV remote controls in its face and pounding buttons, etc,
and it just keeps on working. I'll post the code I'm using if anyone
is interested. One thing that has been priceless in the process of
getting this set up is a little card that Radio Shack sells which
glows when exposed to IR light. Without it, it's awfully hard to
tell if your transmitter is really putting out anything (unless of
course you have one of the newer home video cameras that uses a CCD
imaging chip, in which case an IR LED will generally show up like a
spotlight in the viewfinder).
> Fred,
>
> It seems to me that the first thing most people want to add to their
> robots that is not supported on the handyboard itself, is IR
> collission detection.
>
> How about including a modulator and driver for IR LED's, and a
> detector and demodulator circuit for IR phototransistors /
> photodiodes?
>
> What do other people think?
>
>
> Richard
>
>
-Bill Richman
bill_r@inetnebr.com
-Bill Richman
bill_r@inetnebr.com
http://incolor.inetnebr.com/bill_r
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Message has 2 Replies:
 | | Re: expansion board
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| (...) I can vouch for this technique, this is basically what I do in my PIC program (except the randomness which is a nice touch BTW) and get rock solid detections. When the frequency is spot on to the center frequency (38Khz for the 1ISU60's) and (...) (27 years ago, 15-Feb-97, to lugnet.robotics.handyboard)
| | | Re: expansion board
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| I too have used a similar technique. I used a 555 timer and a 567 tone decoder instead of a PIC. Using an IR can from Rat Shack, and five ir-LED's I get a sensor that sees straight ahead, 30 degrees and 60 degrees to each side. Set the 555 for about (...) (27 years ago, 15-Feb-97, to lugnet.robotics.handyboard)
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Message is in Reply To:
| | expansion board
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| Fred, It seems to me that the first thing most people want to add to their robots that is not supported on the handyboard itself, is IR collission detection. How about including a modulator and driver for IR LED's, and a detector and demodulator (...) (27 years ago, 14-Feb-97, to lugnet.robotics.handyboard)
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