Alt-BEAM Archive

Message #11884



To: beam@sgiblab.sgi.com
From: "Sathe Dilip" sathe_dilip@bah.com
Date: Wed, 15 Mar 2000 10:44:51 -0500
Subject: [alt-beam] Re: Strange Caps??


What you have are probably memory backup capacitors. These have higher
internal resistance. Connect a standard electrolytic capacitor (470 uF
or more) in parallel to one of these in the circuit. That way the 470
uF will provide the initial burst required to start the motor on
trigger. Once the motor is rotating, the memory backup capacitor can
keep it going (hopefully your motor has a low enough current
requirement). If 470uF doesn't do it, try a higher value.

Hope this helps.

Dilip
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Ian Bushong wrote:
>
> I had breadborded solarengine and some strange things happened. I just
> ordered some .022F and .047F caps rated at 5.5V from The Electronics
> Goldmine. http://www.goldmine-elec.com. The 0.022's are made by NEC and
> are labeled FYD and have 264 and F8 running along the side (this probably
> isn't useful but....) and the 0.047's are made by Tokin, and have FYL and
> 118 and I0 or J0 (its hard to read). Anyways, when I charged up the cap,
> it would get about to the 1381 trigger voltage, and then the motor would
> make a soft humming sound. Depending on how close I put my 100W light, the
> humming would get higher pitched, or lower. About twice, I could get the
SNIP
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The early bird may get the worm, but the second mouse gets the cheese.
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11885 Thu, 16 Mar 2000 05:33:56 +1300 [alt-beam] Re: Once more, a reminder for the Lego MotorsMini beam@corp.sgi.com Justin >After doing a fair amount of experimentation myself, I would warn you about
>the Lego Motors. They are indeed nice motors, but only if you really think
>you know what you are doing. They aren't your typical gearmotor, and in
>addition, to get the torque you need out of them you really have to drive
>them with lots of current.

Ah - someone who's played with them. Can you elaborate? I'm assuming
they're worm gears, is this part of the problem? Why would I need to
know what I'm doing? Is it because the torque a bit low for walkers? Are
the RPM's a little high? Is it that the current they need means
modifying the normal walker circuits?

While I was thinking of using them for a walker, my immediate use would
be a photovore. Say I attached a 2cm diameter wheel to the shaft, and
stuck it in a photovore with a total weight about the same a 9 volt
battery. Problems? Lots of current needed?

Thanks for the warning, but since money is a bit tight ATM, even getting
two is going out on a limb to some extent, so I thought I'd try to
prompt more info :-)



11886 Wed, 15 Mar 2000 17:57:49 +0100 [alt-beam] Re: Yet another SE question , "Thomas Pilgaard" Thanks for replying Justin,

So in order to be absolutely sure not to overcharge the cap one would in
theory have to go for a 1381E (2.2v) to account for the possible 0.2v
tolerance - or a 1381G (2.4v) if one is daring.

Since i do not have a powersupply yet I'd like to ask how low one can go in
powering the beam-ant cirquit - this means a 74hct240, two namiki's with no
motordrivers. Would 2.2 volts be enough to drive this cirquit?

I'll give the batteries a try.

Thanks again,

Thomas

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