REFLECTOR: elevator trim

[Laurence Coen]

Andy,

You are correct in that it is a voltage divider but when you connect it to the trim motor the resistance of the motor appears in parallel with the resistor connected to ground.  The voltage will at the motor will be approximately 0.0012 volts.  The motor will not run.

Larry Coen
N136LC


From: Andrew Ellzey 
Sent: Thursday, September 10, 2009 9:02 PM
To: Velocity Aircraft Owners and Builders list 
Subject: Re: REFLECTOR: evlvator trim


Larry,

This is a voltage divider circuit. The formula is: Vout= V1*[R2/(R1+R2)]. The V1 is the 12Vdc input at SP030 and the Vout is seen at pin 10 of connector P4. The circuit as drawn works perfect. I just tested it again with my bench power supply and voltage meter. 12 VDC input gave 6.18VDC output.

Andy Ellzey




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From: Laurence Coen <lwcoen at hotmail.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Thursday, September 10, 2009 7:20:27 PM
Subject: Re: REFLECTOR: evlvator trim


Andy,

Ohms law says E=IxR
E=voltage drop
I=current (Amps)
R=resistance (ohms)

Therefore it would take 10,000 volts to get 1A to flow in a 10K resistor.  A 6 volt drop at 1 A would require a 6 ohm resistor.  6 volts at 1 A is 6 watts or a hocking big resistor.  The trim motor is a 24 volt motor so it is already running at half speed on 12 volts.  It will coast after power is removed making adjustment difficult.  A circuit that offers dynamic braking has been posted in the past and if someone has a copy please post it again.

Larry Coen
N136LC


From: Andrew Ellzey 
Sent: Thursday, September 10, 2009 5:53 PM
To: Velocity Aircraft Owners and Builders list 
Subject: Re: REFLECTOR: evlvator trim


Lou,

I'm not flying yet, but I have added a fast/slow switch in my wiring diagram for this very reason. The plan is that I will switch it to fast mode for takeoff and landing and slow speed for level flight small trim changes as needed during level flight. The two 10K resistors will reduce the voltage to the trim motors to 6VDC for slow speed operation and 12VDC for normal or fast speed operation. Again I am not flying and may have to increase or reduce to resistance to find the actual trim speed that works best.

My switch will be on the Yoke yours can be anywhere you like. I haven't researched how many amps our trim motors pull yet, but 2 ea. 1/2 to 1 amp 10K resistors should handle the load just fine.

See attached sheet.

Andy Ellzey




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From: Lou Stedman <stedmanlou at roadrunner.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Friday, September 11, 2009 8:04:28 AM
Subject: REFLECTOR: evlvator trim


I find my elevator trim to be too sensitive. The slightest touch of the trim switch takes me up too much or down too much. Is there any way to make it less sensitive? Don't know if a rheostat would be the answer.
Lou Stedman
Velocity SEFG
N7044Q
Olean, NY


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