Re: [CAD_CAM_EDM_DRO] RC servo hack for CNC use?

I think that its a great idea - I never thought of a possibility of removing
the pot.
It will require some kind of a driver / controller to convert number of
pulses
into the length of a control signal.
Alex

----- Original Message -----
From: Van Der Sandt Coert <vandersandtc@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, November 15, 2002 3:44 AM
Subject: [CAD_CAM_EDM_DRO] RC servo hack for CNC use?


> Hi
> Has anyone ever hacked an RC servo for use with CNC?
>
> If you take an RC servo and remove the stop block from the output shaft
and
> replace the feedback pot with a resistor network. The servo will always
> think that it is on the mid point. It would then be possible to control
the
> servo direction and speed from a micro controller with PWM.
>
> Add a quad encoder to the servo or lead screw and the same micro
controller
> can count the encoder output and know when the servo has moved a
> predetermined amount. Now feed the micro controller with step / dir
signals
> and it moves the servo (with PWM) in the required direction until the
> encoder counts the predetermined ticks. The servo uses very little power
> when in a 'neutral' state and actively resists external forces.
>
> A standard RC servo has about 5kg/cm torque = 69 ounce/inch (if my math is
> right)
> A standard RC servo moves 0.22 seconds per 60 degree travel = 90.9 RPM
> At 10 TPI that would make for 9.09 IPM - a bit slow?
>
> Please give me your thoughts on where you would mount the encoder and
> whether you think that it would be able to handle higher currents (around
> 2A). Or any other feedback would be great.
>
> Regards
> Coert
>
>
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