REFLECTOR: Emailing: Dynamic breaking circuit 001

[Andrew Ellzey]

Since I haven't purchased the composite design trim relay board or the Infinity yoke yet my wiring diagram is in the preliminary untested stage. I did however take the time this morning to test my adjustable voltage regulator (LM317T) circuit using my bench power supply and driving my standard Velocity pitch trim jack screw. It worked perfect. It appeared that about a 4V output was what I considered slow enough to make small pitch trim changes. The circuit was adjustable from 0 to 12 Volts. The jack-screw would start to move at about 1 volt but could be easily stalled with any pressure applied to the jack-screw. The adjustable 5K ohm rheostat could be located anywhere that is convenient in the cockpit for easy adjustment. My fast slow switch on the yoke wouldn't actually be needed, but I prefer the ability to quickly switch between high and low speed as I have it designed. Once the correct setting for the rheostat R2 is known, it could be removed and
 replaced with a fixed resistor. Again not flying yet so this is all a best guess. I also added about a 15lb load to the jack screw and the highest amps that I could make my jack-screw draw was .75 amp.  I also sent an e-mail to composite design asking for a schematic of their trim relay board and told them that I was going to add a dynamic breaking circuit, and this is the e-mail that I received.

(Hi Andy,
The Trim Relay Board that I supply to Velocity, Aircraft Spruce, Infinity, etc... is based on each axis having two SPST relays. This is referred to as an "H" bridge
circuit with the connections as follows: Both N.C. contacts are connected to GROUND, both N.O. contacts are to +12V & the armatures each go to a motor lead.
In this configuration both of the motor leads are connected together (at GROUND) as soon as the trim switch is released. This effectively applies the brakes to
the motor by design. I have this unit in my Velocity and have installed it in at least 50 other Velocitys not to mention the other 500+ units I have sold. Permanent
magnet motors, as used in most trim systems, generate a voltage when spinning. As you know, if you load the "output" of the coasting motor it will slow down
quickly - that's what the TRB does for you as it is.

Hope this helps, let me know if you need more assistance. May I ask why you are so concerned about using dynamic braking? Please be assured that my TRB
was designed with this circuit effect in mind - it seems to do a good job...


Best Regards,
Wayne Lanza
Composite Design)

So the grounding circuit for the jack screw is already in the design. Updated print is attached.
 
Andy Ellzey





________________________________
From: Laurence Coen <lwcoen at hotmail.com>
To: reflector16 <reflector at tvbf.org>
Sent: Friday, September 11, 2009 11:24:04 AM
Subject: REFLECTOR: Emailing: Dynamic breaking circuit 001


Andy,
 
Now your talking. That should work slicker than snot on a brass door knob. The attachment is the circuit I use for dynamic breaking.  When you release the hat switch the relays short the motor leads, stopping the motor quickly.
 
Larry Coen
N136LC
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