High Power Servomotor control

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High Power Servomotor control

Postby fc747 » Fri Jul 14, 2006 12:16 am


I'm using an 747 200 throttle quadrant in my project, with the original autothrottle chain in place - I was hoping to use the 4servomotor card (using one channel) to control the movement - with my setup, there's just a single motor that drives the throttle shaft.

As the load here is much more than the hitec/etc motors can handle, I wanted to know if it is possible to use the 4servo card to drive a heavier motor (thru an amplifyer?) - I would really like to use the fs2Phidget software package here -

Please let me know if this is at all possible?


Farrokh Chothia.


Postby dymojim » Mon Jan 01, 2007 5:22 am


One possible solution is to use a stepper-motor servo. This is a circuit that
takes in 0-5V and drives a stepper motor to a proportional position.
Positional feedback to the circuit is achieved with the usual potentiometer
feeding back the mechanical position of the driven device as a 0-5V
return signal. The positional pot can be used at the end of a geartrain
or whatever your mechanics require. The stepper motor can be any size
and power up to the limit of your coil drivers.
You can then still use your servo-phidget to drive a pot that provides 0-5V
position-required input to the circuit.



Better late than never...

Postby raysot » Thu Nov 13, 2008 12:07 am

It's been a long time since your original post and I'm sure you've already arrived at a solution. My solution was to use high-power R/C sail servos.

http://www.servocity.com/html/hs-815bb_ ... l_arm.html

The 4-channel Phidgets Servo card can't sink enough current to drive these big guys effectively, so I added an external power supply and just use the PWM signal from the card with a common ground throughout the entire circuit.

The card is interfaced to an applet I wrote as a proof-of-concept to control the servos when FS(X) is running and the sim is under Autothrottle control. To ensure that the throttles really disconnect when not under A/T control I added a power relay which is driven by the A/T FSUIPC offset.

My source code (and an executable in the BIN dir) can be downloaded for free here:

It's released "As-Is"... meaning that you might want to know a little about C# if you want to take it further.

If you have any questions, drop me a line..

Kind regards,

Posts: 7
Joined: Sun Apr 11, 2010 2:36 am

Re: High Power Servomotor control

Postby farrokh747 » Sun Apr 11, 2010 12:07 pm

Hi Ray -

I've managed to get the AT going using a hacked Hitec servo and an H bridge amplifier from robotpower...

http://www.mycockpit.org/forums/showthr ... #post74779

It works great, and this system lets me use DC motors up to 28VDC...


I'm going to add a servo to the aileron system as well for CW movement in autopilot...




Re: High Power Servomotor control

Postby didier.bravo » Thu Apr 14, 2011 5:36 pm

so, using a simple H amplifier is the only way to send more than 5V to the servos with the PhidgetAdvanceServo???

Posts: 7
Joined: Sun Apr 11, 2010 2:36 am

Re: High Power Servomotor control

Postby farrokh747 » Thu Apr 14, 2011 10:37 pm

Hi -

I'm sure there must be other ways, this is the one I use (being a non coding type simpleton, I depend heavily on FS2Phidgets) ...... I couldn't find any other solution within the sim community forums -

Here's a schematic of my system:

http://farrokhchothia.com/simplehservo/ ... hmatic.jpg

works well enough, and easy enough to set up


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