Erikcnc wrote:
andypugh wrote:
Erikcnc wrote: Im thinking of using this encoder and connect it through a small timing belt to the spindle and not using the encoder of the motor anymore.
Should work. It has an index (not all do)
Though as Blazini showed, motor encoder + separate index can work well.
How do i realize this? I got a bunch o NPN NO sensors to test it.
I have to make sure that the spindle rotates the right rpm.
For that you'll have to use a known good device to either calculate the spindle speed or measure it. Assuming you have no optical tach or anything to measure the spindle directly......If you spin your motor exactly 1 rotation (just the motor), the number of counts from the encoder count pin should match it x4, so a 1000ppr encoder should show 4000 counts, in that case your "scale" in the .ini is 4000, and your velocity feedpack pin will represent
rotations per second exactly
at the motor, but this is not what you want unless your belt ratio is exactly 1:1.
Excuse any math mistakes, I'm writing this off the top of my head, I'll use the 1000ppr as an example....
Since you are not using a timing belt you should spin your spindle by hand and let it drive your motor then you can estimate the difference, how accurate you get is all in how thorough you are. Spin the spindle exactly 1 time and look at how many counts feed back from the motor, if you get 2500 counts, then divide 2500 into 4000 and you get 0.625. Now if LinuxCNC is driving your motor based on the encoder feedback then you want to leave your hm2.7i76e.......encoder.scale pin at 4000. Use the scale hal component with the gain pin set at 0.625 to feed back into motion.spindle−speed−in pin. You also need to use another scale component to scale the position pin the exact same amount into the motion.spindle−revs pin. Now your spindle speed/position requirements are satisfied for LinuxCNC.
To make the index work when your motor is not 1:1 with the spindle exactly, disconnect the index pin in hal and physically, you don't need it. Use the NPN prox switch with the signal wire tied into the 7i76e's encoder index input. then connect the motion.spindle−index−enable pin to the 7i76e......encoder.index-enable hal pin. This works because the spindle index prox is still resetting the position pin on the 7i76e at a rate that will roughly equal "1" to motion since it is scaled to do so. in order to use a Prox in the 7i76e's encoder index it has to either be NPN or 5v PNP, do not use a higher voltage prox with the encoder index unless it is NPN and shares common with the 7i76e's logic side..
