Subject:
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Re: Polaroid trouble again
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 3 Aug 1998 22:27:31 GMT
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Original-From:
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Rick Moll <[rickmoll@mvp]spamcake[.net]>
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Viewed:
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652 times
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Alf Kuchenbuch wrote:
> Hi!
> I am having trouble with my Polaroid sonar:
> When I keep my HB hooked up
> to external power, I will only get correct readings up to 20 inches. As
> soon as I use battery power without hooking it up to external power, the
> readings are correct up to 6 feet, not more! This sound like EMI, I
> guess. I tried all the capacitor tricks from HB mailing list, but in
> vain. Do you know a fix that works?
I haven't used the Polaroid module with my HB, but I have used them a lot
with 68332 micro-processors. I does sound like you may have an electrical
noise problem (not EMI, but noise conducted through the power bus).
The only way I've got the Polaroid modules to reliably measure long
distances was to either use a separate power supply regulator for the sonar
module, or to filter the micro-processor's power bus feed to the sonar
through an L-C filter:
(power bus +5V) >--(RF Choke)--*--> (+5V sonar power)
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(cap)
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(gnd)
The RF Coke was 100uH with a 2A rating, and the cap was 2200uF with a 16V
rating. DigiKey carries Panasonic caps which are low ESR, and much better
than the ones you'll find at Radio Shack. You can find the RF Choke at
Radio Shack, or at Mouser.
Later,
Rick
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Message is in Reply To:
 | | Polaroid trouble again
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| Hi! I am having trouble with my Polaroid sonar: When I keep my HB hooked up to external power, I will only get correct readings up to 20 inches. As soon as I use battery power without hooking it up to external power, the readings are correct up to 6 (...) (26 years ago, 3-Aug-98, to lugnet.robotics.handyboard)
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