A potential problem with the resistance approach is that the supplied
voltage is current dependent. Theorize a binding condition or
electrical fault in the motor. The fault itself will reduce trim
response, and the increased current (short of popping the fuse) might
drop the volts to where the motor could stall.
****************
Agree with you that the trim speed is far too high.
I have built in a poti to regulate the speed of the trim motor. (MAC is
supplying this poti). With the reduced speed you can trim the plane with
much higher precision. I
reduced the speed to about twice as slow as original. Works perfectly.
Klaus
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I asked a friend about this (electronics engineer) and his suggestion
(if you are paranoid) is something along the lines of a "pulse width
modulator" - infinitely variable, and doesn't drop the voltage (so full
power regardless of speed) - does it by turning the motor off a greater
or lesser degree per unit of time.
he also sez:
looks like they are just reducing the voltage in the old Joe Lucas way by
putting big power Zeners across the driver supply. Not sure if the drive
circuit would like to see the effective low resistance short that a Zener
presents when the supply voltage exceeds the Zener voltage. It may be safer
and better to use a potentiometer or a power transistor to do this.
Not sure why your man dislikes carbon-track pots - these are the norm these
days except for power devices.
So, as I read it, he reckons there is nothing wrong with simply
dropping the voltage with an appropriate resistor or running it through
a pot... with the trim system switched off/slow/full(bypass)
any comments from Bob....?
Miles
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