Alt-BEAM Archive
Message #00764
To: beam@corp.sgi.com
From: Justin jaf60@student.canterbury.ac.nz
Date: Tue, 23 Feb 1999 03:07:15 +1300
Subject: [alt-beam] reverse switch for photovore
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As some might have noticed (and helped :), I'm working on a bicore-based
photovore. Being the annoying guy that I am, I decided I wasn't happy
with the reverse switch only acting for as long as it was contacting,
and decided to make a reverse switch with a time-delay before it resets.
Normally, a resistor-capacitor arrangement is used, but there didn't
seem any obvious way of applying that directly to bicore sensors, so I
did it indirectly . Below is the diagram for the most successful
method I found. If you can think of a better way, I'd love to hear from
you :-)
I tried implementing it without a transistor, with some success, but
there way a very noticeable influence on the bicore from the presence of
the circuit, whereas with the transistor, there is no apparent
difference to operation, except for the addition of the timer on the
touch sensor.
Obviously, a timed switch acting the other way can also be added across
the other photo-diode.
Comments? Does this look like a sensible way to do it?
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765 Mon, 22 Feb 1999 15:51:30 +0100 (CET) [alt-beam] Re: It works, but I don't know how... new diagram Wilf Rigter Steven Bolt On Mon, 22 Feb 1999, Wilf Rigter wrote:
> Not expecting it on the BEAM list?
>
> The designer's own explanation always helps! Ofcourse the pulse generator
> itself consumes power since it also operates in the linear region part of
> the time.
But very briefly, about 1ms every 200ms or so. A considerable
improvement over the situation where an SE voltage trigger slowly
moves into the linear region and remains there for 20 minutes while
the solar panel tries to convert bad light into the final small
fraction of a volt.
> Anyway I tried the sensor latch with the 3 diodes to the V+ and it
> seems to work quite well.
That's what I started with, about a year ago, and I didn't like the
current consumption in the linear region. Adding the pulse
generator made it *much* better.
Justin's design is based on SunEater_II, as described on:
Linkname: BEAM Robotics Tek - The SunEater Series
URL: http://people.ne.mediaone.net/bushbo/beam/suneater/suneater.html#suneater2
SunEater_II combines easily adjustable switch-on/off levels with a
current consumption between 10 uA and 20 uA, no matter where it is on
the charge curve. SunEater_III (also on the page mentioned above)
demo's a photovore based this design. It wastes very little light
and is capable of full reverse from an obstacle - without even
reversing its motors.
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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