Re: [CAD_CAM_EDM_DRO] correct encoder setup

sparkness2001 wrote:

>simple question, im putting servos on my BP type mill
>I have .2 lead and I plan on using a 2:1 pulley reduction to the
>motors with geckos. I want to make sure Im using the right encoder
>which the math tells me a 1000 cpr will work giving me .0001"
>movement per pulse. Is this the only encoder combo to use for this
>setup?
>
>

No, you should be able to do anything you want. There are some limits
due to max motor speed, motor torque and the rate the computer can
spit out encoder pulses. If the computer is limited to about 20,000
pulses per second, than you should be able to get 2 IPS or 120 IPM
with the arrangement you mention.

But, 1000 CPR is not a very clear definition. Is that COUNTS per rev
or CYCLES per rev? The number of black lines in the encoder wheel
is called cycles/rev. Most modern encoder counters count every
quadrature transition, so you get 4 counts out of every cycle. SO,
a 1000 cycle/rev encoder will give 4000 count/rev.
If your encoders are 250 cycle/rev, then your above calculations are
correct. If it is 1000 cycle/rev, the resolution will be 4 X as high,
or .000025" (40,000 counts/inch).

Jon