Best way for feedback with RC ESC spindle?

I like the idea of having a closed loop spindle controller, and see all the software is available in LinuxCNC. What is the cheapest way to get feedback from the motor back into LinuxCNC?

Some folks build an encoder using opto sensors and a disk with slots on it.

Something like this
www.linuxcnc.org/index.php/english/compo...imit=6&start=6#14832

with an opto switch circuit like this
www.linuxcnc.org/index.php/english/compo...id=26&id=17960#18093

regards

With a brushless motor, shouldn't you be able to get rpm from sensing pulses on a motor line?

With a brushless motor, shouldn't you be able to get rpm from sensing pulses on a motor line?

Yes, if you know how to build a circuit to do that and can eliminate other interference.

You just need to be able to sense the 'blip' as each pole rotates and then divide by number of poles to get RPM.
Afraid I don't know how practically you do it though.

regards

I found this : www.hobbyking.com/hobbyking/store/uh_vie....asp?idProduct=17552 that someone (diydrones.com/forum/topics/brushless-mot...6002&page=2#comments) has connected the output to an arduino, and was able to get 1 pulse per rpm. The only problem was the arduino was only able to capture to 14000 rpm. Can this output be instead connected to an input port in linuxcnc, and capture the full rpm?

So long as it outputs a clean pulse once per rev, you should be able to use it as the basis for a signal for encoder.nn.phase-Z.

The testing bit will be whether your pulses exceed the capacity of the encoder to register them.
Some of that will be dependent upon the speed of the thread.

We don't generally have spindles which exceed say 3,000 rpm on CNC machines, let alone over 14,000!

What speed are you expecting to run it at?

Hopefully one of the electronics boffins is monitoring this and can definitively advise

regards

Because of the PWM modulation of the commutation signals from the ESC and therefore need for a multipole low pass filter and also possible isolation/groundbounce issues, I would probably dump the direct ESC tap and just use an opto interrupter, reflective sensor, or Hall pickup (a 50% duty cycle interrupter could be read up to ~300,000 RPM (5000 Hz) with a a decent (10 KHz) base thread

Here. Someone has already done all the heavy lifting for you.

logicnc.com/rcnc.html

EDIT: NVM. I thought that controller was closed loop. I think it is only for open loop control.