Subject:
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Re: IR Ball (was Soccer-Playing Robots)
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 1 Sep 2000 20:31:21 GMT
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Original-From:
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Russell Nelson <nelson@!nospam!crynwr.com>
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Viewed:
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488 times
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Wilcox, Doug writes:
> I need a schematic (or--in reality--at least a resistor value, whether the
> LEDs are parallel or in series, and the battery voltage used) to wire the
> LEDs without burning them out, but my biggest challenge will be finding a
> clear plastic ball of the right size. :)
LEDs vary greatly in their light output relative to their current draw
at any one voltage. You can't get good results by connecting them in
serial OR parallel. You have to give each one its own resistor.
Resistor and LED go in serial, and each of those goes in parallel with
all the rest.
You can size the resistor with a VOM pretty easily. Hook up a 1K
resistor to a 9V battery in series with the LED. Measure the forward
drop on the LED. Now look at the specs to see what current they
suggest. Look at the typical rating, not the absolute max. Then
subtract the forward drop from your desired power supply. Divide that
voltage by the desired current and that gives you the resistor you
need. If you're lucky the value is close enough to a resistor pack;
otherwise you have to use discretes.
--
-russ nelson <sig@russnelson.com> http://russnelson.com |
Crynwr sells support for free software | PGPok | Damn the firewalls!
521 Pleasant Valley Rd. | +1 315 268 1925 voice | Full connectivity ahead!
Potsdam, NY 13676-3213 | +1 315 268 9201 FAX |
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Message is in Reply To:
 | | IR Ball (was Soccer-Playing Robots)
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| The Lego light sensors are particularly sensitive to infra-red (one of those gems of information that I've picked up from the robotic mailing list), so the standard Lego light sensors can be used to "see" a ball that's throwing off lots of IR, like (...) (24 years ago, 1-Sep-00, to lugnet.robotics)
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