Alt-BEAM Archive
Message #08891
To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@telus.net
Date: Fri, 07 Jan 2000 08:19:01 -0800
Subject: [alt-beam] Re: Pressure Sensors
Jonathan D Rogers wrote:
>
> OK, this is probably way too complicated, but I had to say it:
> Couldn't you rig up a bend sensor somehow to detect pressure?
Sure. It would work no problem. Price from Jameco = $10.95 each.
Bruce
8892 Fri, 7 Jan 2000 08:21:50 -0800 (PST) [alt-beam] Re: Servo Control Circuit beam@sgiblab.sgi.com Richard Piotter <-- My ACTUAL e-mail address is richfile@rconnect.com -->
<-- I'm away from home and can recieve pop3 mail, but -->
<-- I can not send SMTP. I am using my online mail to -->
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Not completly so complicated. You can use an operational amplifier and a
variable resistor to do the same thing, skipping the Pulse Width
Modulation (PWM) all together. You also get to easily adjust the motor
by variable resistors. you simply send it a varying voltage or current
based input, depending on Op-Amp configuration, and the motor does the
same thing, but all in analog. You can use a fixed voltage input as well
for predetermined positions. potentiometers would calibrate where each
input would go. If you have 4 lines, and each potentiometer 2x the
previous one, you have a binary position generator. make that 8 lines
and you have an 8 bit one! that's 256 positions, though you can probably
get away with less. Or, if you have a BEAM circuit, two fully extended
postions and maybe if the bot features a stop fiunction, a center leg input.
I'm thinking of trying that with my Quadrapod if I can't get the servos
and have to do a smaller, cheaper version with BG Micro Motors. I'll
have to try with the external gear boxes if I do, cause I need it to
carry a large enough batttery for a color video camera and transmitter,
plus the robot itself!
David Perry wrote:
>
> not really, the good thing about servos (if you are using them in R/C) is
> that they have feedback and if you tell them to stay in a position they'll
> use all their strength to stay there. Servos are DC motors with an encoder
> to tell it how much the shaft has rotated and how fast it is going. So
> you'll need an encoder attached to the motor, and a circuit to tell it how
> far to turn to get to that position and stay their. Not a very easy task,
> but possible if you really want to. Also you'll have to decode the PWM
> signals.
>
> regards,
>
> David Perry
>
> -----Original Message-----
> From: SG
> To: beam@sgiblab.sgi.com
> Date: Thursday, 30 December 1999 3:21
> Subject: Servo Control Circuit
>
> >does anyone out there know if there is a circuit available for turning a
> >regular geared DC motor into a servo? Maybe an IC chip that does this?
> >I'm wanting to control some of my motors (already in my possesion) with a
> >servo controller, without having to go out and buy the little buggers.
> >
> >-Sparkeeeeeeee
> >
--
Richard Piotter The Richfiles Robotics & TI web page:
richfile@rconnect.com http://richfiles.calc.org
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