[TowerTalk] Ramp up summary

[Denis Coolican]

  Hi to all.  My original question  was, 'I was wondering if anyone  had
any circuits or devices for controlling a DC Motor
driving a prop pitch rotator.

Thank you all for your input.  Below is a summary  of the replies I did
receive.
I used a motorcontrol box that came from a factory conveyor belt system.

Instead of a on/off switch, use a variac (with a physical limit at 90 v
out) and there's your "ramup". Crude but simple

 My  M2  OR-2800   controller  can  be  used  for  prop pitch motors. It
is programmable  for  any  rpm  motor/  gear reduction.  Comes with  9
speed  ramp  up  and  9  down.

     Operated on 28V DC they will out live you.

     It just occurred to me that you may not have a motor problem but a
gear box problem of perhaps rusty bearings.

     If you want to homebrew your own ... you might look at pulse-width
modulating power MOS-Fet semiconductors set up in an "H" bridge
configuration. Model railroaders have been using PWM to give a more
realistic motion to their scale   locomotives.

     To deal with the voltage drop problem the 28vdc power supply is
located at the prop pitch and 120vac is run up the tower. Two relays are
required to energize the power supply and control direction of rotation.

     I have a 30V, 15 amp power supply. I have added a Mosfet in series
with the pos. lead and can change the current rather than the voltage as
variac's do. By varying the gate voltage between 0 and 10 volts no
current draw/required] the     current can be varied from 0 to 15 Amps.
Thus a simple pot and voltage supply can be used or you can devise a
pulse sytem to vary the open gate voltage at different duty cycles to
change speed.

     I'd sure check out the gear box

     That Prop pitch  should run fast and coast some.

Regards,

Denis VE6AQ



--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com