Re: RC servo hack for CNC use? Confidentiality Warning;(

Hi Coert,
Not trying to be mean, but this is a public list, so lose the
warning or dont post. I defer to the list hosts...
-Lee

--->regarding:

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--- In CAD_CAM_EDM_DRO@y..., Van Der Sandt Coert <vandersandtc@a...>
wrote:

> 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
>
>
> Confidentiality Warning
> =======================
> The contents of this e-mail and any accompanying documentation
> are confidential and any use thereof, in what ever form, by anyone
> other than the addressee is strictly prohibited.