Alt-BEAM Archive

Message #10661



To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@telus.net
Date: Tue, 22 Feb 2000 12:38:44 -0800
Subject: [alt-beam] Re: Walker problems


Bernard Nazari wrote:

> ... Now when I stick on the servo's, they just either don't
> work, or they go into fully saturation and then they don't work.

Hey, Bernie. Are those out-of-the box servos, or have you stripped out
the electronics?

And, did you try just powering the servos off a battery to see how they
behave?

> The servo's drink about 150 mA's , which should mean I could
> stack 3 or 4 of the 245's and be in the clear by far.

This has been done many times, and successfully too. However, I came
across an intereting note in a Motorola handbook. Putting logic gates in
parallel is OK if they are on the same chip, but is NOT recommended if
the gates on are separate chips (e.g. stacked). The reason is that if
they trigger at different voltages, you could cause a brief short
circuit each time they fire. Since so many people have pulled this off,
my suggestion is to only parallel up chips of the same type from the
same manufacturer (and note: Rat Shack is NOT a manufacturer).

> I am going to try to get some of the 74HC245's, (which I think
> have a wider range of input voltages.)

Two volts up to 6 volts. Absolute maximum rating is 7 volts. People have
pushed them higher with no problems. If you do run these chips at higher
than 7 volts, you are definitely not going to get the full rated
lifespan of 120 years out of them :)

> Is the H-bridge something I should be looking at?

That's the route Sparky took with his Lotus. The common configuration is
good for 100 mA (200 if you push it), and by substituting some
transistors you can push it up to 800 mA easily (cost you about 25 cents
more per bridge).

Regards,
Bruce



10662 Tue, 22 Feb 2000 12:38:50 PST [alt-beam] Re: BEAM: Tendency toward miniaturization beam@sgiblab.sgi.com "Timothy Flytch" > >Personality doesn't causally arise with complexity. Our skills as humans
>is
> >not a product of our brains - it is the result of not only a lifetime of
> >being-in-the-world, but also a of many generations passing of "tacit"
> >knowledge through genetic material.
>
>No, I don't think so. You can't honestly believe that genetic material
>makes one act a certain way.

I do...
I think we discount this too much... Instincts are real...
Timothy...
______________________________________________________



10663 Tue, 22 Feb 2000 21:50:31 +0100 [alt-beam] Re: Robotic philosophy (Tendency toward miniaturization) "Thomas Pilgaard" In light of the discussion one may think to ask the question: what is the
definition of a robot?

Should we take Asimov's defintion or is it something to eventually replace
mankind? Something other?

Regards,

Thomas

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