REFLECTOR: Pitch Trim Mystery

[Jim Agnew]

Many of the "coolie hat" switches are only rated at 100ma per contact and you can get away with connecting the roll trim motor but not the pitch trim.   Personally I used relays for both.  Happy I did since I installed a more powerful trim motor.
 
Jim
 
James F. Agnew
Jim_Agnew_2 at Yahoo.Com
Tampa, FL
Velocity 173 Elite Aircraft Completed & Flying 


----- Original Message ----
From: Al Gietzen <ALVentures at cox.net>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Saturday, March 25, 2006 10:56:05 AM
Subject: RE: REFLECTOR: Pitch Trim Mystery


Subject: RE: REFLECTOR: Pitch Trim Mystery
 
I probably did a stupid thing.  But I connected my control stick switches directly to the trim motor and breaker.  There is no relay in between.  I know it is just a matter of time before the switches say “goodbye”.
 
Not necessarily so.  I measured the current needed to run the trim @ 12v.  My memory (such as it is) is that it was about 2 amps.  Even your small stick grip switches can probably handle that; IF you kill the induction spikes that make arcs on breaking the circuit.  (The motor coil is an induction device)
 
My MAC stick grip switches are rated at 5 A at 28 volts.  I put a TVS across the leads at the connector (see photo).  No relays.
 
You also want the circuit set up to connect the lead to ground when you let off the switch to help “brake” the travel.  The MAC switches are set up to do that.  If your switches aren’t, then you may want to set up relays anyway for that purpose.
 
FWIW,
 
Al
 
 
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