Torque from a stepper motor is also a function of speed, at least on the
ones I have worked with. I had to take over a failed project that used
steppers, and found two problems-
#1 was an RF level oscillation in the position sensor amplifier (fixed by
taking the Amp out, because it was not needed)
#2 was a lack of repeatability in position, because the steppers were being
run too fast- the problem was that at higher speed, the torque dropped down
to about the friction level on the device being driven, and the drive
pulses were not causing motion. The fix was to slow it down
In this case, QRP and QRQ were the answers.
Bill-W4BSG
At 07:53 AM 8/26/01 -0600, you wrote:
>
>>> Anybody out there successfully used stepper motors to power variable
>>> caps in remote tuners? The ability to have good
>>> precision/repeatability seems idea. Chief problem seems to be
>>> obtaining one with enough torque.
>Torque can be generated through gearing. I imagine this would work quite
>well.
>I have some significant experience with both steppers and DC servo motors
>(though
>not in this application) and either would work fine. Servos are harder to
>work with.
>The control software is interesting and the external circuitry (amplifiers)
>required are expensive
>and/or non-trivial to build.
>
>
>73,
>George K. Watson
>
>
>List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
>Trylon Titan towers, coax, hardline and more. Also check out our self
>supporting towers up to 96 feet for under $1500!! http://www.anwireless.com
>
>-----
>FAQ on WWW: http://www.contesting.com/FAQ/towertalk
>Submissions: towertalk@contesting.com
>Administrative requests: towertalk-REQUEST@contesting.com
>Problems: owner-towertalk@contesting.com
>
>
-
Bill Aycock --- Persimmon Hill
Woodville, Alabama, US 35776
(in the N.E. corner of the State)
W4BSG -- Grid EM64vr
baycock@HiWAAY.net
w4bsg@arrl.net
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 96 feet for under $1500!! http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|