Alt-BEAM Archive
Message #11136
To: beam@sgiblab.sgi.com
From: JVernonM@aol.com
Date: Tue, 29 Feb 2000 17:45:11 EST
Subject: [alt-beam] Re: BEAMAnt circuit
In a message dated 2/29/00 5:16:43 PM Eastern Standard Time,
beamtastic@yahoo.com writes:
> This is totally dependant on the resistor values that
> you are using.. My beamant has a left-right waggle
> with about the same timing as a standard bicore with
> .22uF caps and a 1.5 M resistor, and it is
> aggressively phototropic in a wide variety of light
> conditions.
Do you see an acceleration or deceleration of pulses in differing light
conditions, or do you tune that to a minimum?
See ya,
Jim
http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
ICQ# 55657870
11137 Wed, 1 Mar 2000 09:46:21 +1100 (EST) [alt-beam] Re: solaroller throttle??? beam@sgiblab.sgi.com Ben Hitchcock > I have a question... would this work? Here is my
> idea... replace the resistor in a standard solarengine
> with a capacitor... this way when it fired it would
> have a lot of torque as the resistance would be low,
> and as the cap charged and the resistance increased,
> less current would reach the motor, spreading out the
> power... this (if it worked) should make the thing
> blast off the line, and spread out the remaining power
> over a long stretch, where it just has to keep its
> momentum, which doesn't require much power...
There are a couple of problems with this: When the SE initially triggers,
you will waste a LOT of power because there is effectively no AC
resistance between the base of the trigger and a supply rail. Then, the
cap will charge up very quickly once the voltage on the base reaches 0.7
volts, resulting in a very quick and not very efficient 'pop'. Easily
fixed, just put the 2.2k resistor back in so that the cap is in series
with this resistor.
So what you're saying is that there would be a time in the cycle where the
transistor isn't on fully - it only lets a little bit of charge trickle
through to the motor.
Interesting.. I had pursued this train of thought a while ago, and came to
the conclusion that you will be wasting power by heating up the
transistor. If the transistor isn't on fully, then it has a voltage drop
across it. You still want some current to flow through your motor, so
P=VI (power = volts times amps) you will lose some power through your
transistor.
Another train of thought worth pursuing is that the transistor that drives
the motor driver is optimised for switch-on. That is, in normal operation
it is really overdriving the motor driver, wasting power itself. If you
could optimise the SE such that the driver transisto is only ever on as
hard as it needs to be to be saturated, then efficiency will climb a
little bit.
In English? Take your standard SE circuit, and put a capacitor in series
with the 2.2k resistor. Now put another resistor in PARALLEL with the
cap, say about 33k or so. Chances are this will improve efficiency
although it might be kind of hard to measure.
Of course, there is no substitute for experimentation. Kyle showed me
this when he put a cap and LED in parallel with the motor (using my FRED
SE), which made the
motor take off like a rocket. I hadn't even thought of this, and wouldn't
think that it would make that much difference but apparently it does. So
go forth and experiment!
P.S. I think that the cap across the motor increases the switch-on
voltage, and nothing else. Perhaps a comparison needs to be done with two
SEs side by side to see which one goes the furthest in a given period of
time. I would expect the non-capped one to win but then again there's no
substitute for experimentation!
Ben
11138 Tue, 29 Feb 2000 16:56:34 -0600 [alt-beam] Aquabot tutorial found! alt-beam@egroups.com Ben A Micklin Hey, I have found a tute on how to create a solar submarine.
http://members.xoom.com/Star_BEAM/
Go to Star BEAM and look for the BEAM net link.
~ben~
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11139 Tue, 29 Feb 2000 17:01:53 -0600 [alt-beam] Solar cells beam@sgiblab.sgi.com "Bryan Hengels" I noticed some differences in the descriptions of solar cells at Solarbotics and Adaptobotics. The voltage and current outputs were different, is this due to a different light level? As far as I know they are the same cells, right? Any help appreciated.
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11140 Tue, 29 Feb 2000 17:09:12 -0600 [alt-beam] Re: shack caps beam@sgiblab.sgi.com "Bryan Hengels" I've seen these but haven't tried them, I wouldn't think they'd be worth it. They are fairly expensive and don't have a very good output. But hey, we're supposed to experiment, right!
--
On Tue, 29 Feb 2000 17:32:49 BUDSCOTT wrote:
>i've seen some solar panels from the shack, don't put out much voltage, but i
>was thinkin of buyin a couple and puttin in a series, do any of you guys know
>about these, and how good they work, i found them in the very back of a
>shelf, they were kinda hidden away, not a match for a sunceram, but would it
>be wortha try?
>
> -Spencer
>
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11141 Tue, 29 Feb 2000 18:14:19 EST [alt-beam] Radio shack solar panels beam@sgiblab.sgi.com BUDSCOTT@aol.com I was looking around, out of curiosity, (it didn't kill my #$%& cat, wait a
minute i don't have a cat!?) at the radio shack web site, i found some low
voltage high current panels there, well okay one panel, that puts out .45 VDC
(dinky) with 1000 mA (pretty cool) you'd need to boost the voltage with a
second panel of some sort (cheat calculator cell) but that would provide some
awesome ambient light operation. I'll have to check it out for more info!
-Spencer
11142 Wed, 01 Mar 2000 10:42:51 +1100 [alt-beam] Re: mini walker beam@sgiblab.sgi.com Rob
Richard Piotter wrote:
> Nope, I'm not using motors. they are solenoids. Simple coils to attract
> and repel a magnet mounted to the legs. the legs move VERY freely. The
> joint has very little friction. I've proven that the coils from
> solarbotics can move the legs (the whole robot infact! :)
Well done.
I felt sure that would be possible.
Rob
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