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 Robotics / 10621
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Subject: 
RE: Drive R/C Servos with the RCX and pbForth (long)
Newsgroups: 
lugnet.robotics, lugnet.robotics.rcx.pbforth, lugnet.robotics.rcx
Date: 
Sat, 12 Feb 2000 12:57:13 GMT
Viewed: 
1570 times
  
In lugnet.robotics, Ralph Hempel writes:
Well, after a few hours of crunching away at the problem, I
now have pbForth code to allow you to control and hold a servo
in up to 100 positions.

If you're using a custom motor driver in pbForth, why use the inverter circuit
at all?  Why not just generate the desired waveform directly?  Is there not
enough current to drive the servo that way?

No, the servo needs power to the + and ground terminals to drive
the motor to the setpoint indicated by the signal wire. If I don't
invert the signal there is no power for about 30msec and only
1 or 2 msec ov voltage on the motor port.

By using the inverter, I can simply power the servo all the
time, and use the cap to hold things up while I'm sending the
(inverted) 0V signal to the servo.

The motor driver itself is in H8 assembler and compiled into
the new (unreleased) pbForth kernel. It still allows you to use
the regular motors on any ports you are not using servos on.

Cheers,

Ralph Hempel - P.Eng

--------------------------------------------------------
Check out pbFORTH for LEGO Mindstorms at:
<http://www.hempeldesigngroup.com/lego/pbFORTH>
--------------------------------------------------------
Reply to:      rhempel at bmts dot com
--------------------------------------------------------



Message has 1 Reply:
  RE: Drive R/C Servos with the RCX and pbForth (long)
 
(...) I should add here that no external power source is necessary to drive the servo. This is important since a micro or miniservo and an SMT version of the driver can be made to fit INSIDE a space similar to a worm gear box (6588 in LDraw). I'm (...) (25 years ago, 12-Feb-00, to lugnet.robotics, lugnet.robotics.rcx.pbforth, lugnet.robotics.rcx)

Message is in Reply To:
  Re: Drive R/C Servos with the RCX and pbForth (long)
 
(...) If you're using a custom motor driver in pbForth, why use the inverter circuit at all? Why not just generate the desired waveform directly? Is there not enough current to drive the servo that way? --Ben (25 years ago, 12-Feb-00, to lugnet.robotics, lugnet.robotics.rcx.pbforth, lugnet.robotics.rcx)

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