1kw DC Lathe Spindle - ELMCHAN Servo drive

[krazatchu]

Hi ppl...

As the subject states, I'm working on a design for a Servo drive for my soon to be purchased lathe...

I have already built the X and Y drivers based on the ELM CHAN software...
I have also built an optically isolated break out board and so far everything is working well...

The lathe comes with a 550 watt AC motor, I will replace it with 1kw DC motor, I have found a few used ones in the local market for about $100...
I will have to add an encoder, prolly I will salvage one from a used photocopier servo....

Anyhow... I'm not exactly clear on how I should configure the E-stop for braking... looking for some insight/advice

The Elmchan drive has a software current limit...
While testing the X & Y drives with a ~100w servo, I found this will trigger if I clamp on the visecrimps and twist and hold for a bit....
Once triggered the PWM stops, the error light goes on, also triggers estop on pc, and motor will free wheel...


So, I'm thinking I have a couple of options...

1) I could set the current limit (in software) really high to disable it and then rely on an external limit system (like that of the HP UHU designed by Kreutz)...

2) Or I could modify the source code to extend the time on the current limit...
So that the spindle comes to a stop before the limit kicks in...

3) Or I could just let it free wheel after an E-stop, using either the software current limit or the SD pin on the ir2184 fet drivers...

4) Or I could just have it trigger a relay to disconnect the motor and short the motor thru a resistor...


Preferably and for safety reasons, I would like it to stop as quick as possible, it would also be nice if it didn't loose position on Estop (while threading?)....
So that leaves me leaning towards options 1 or 2.... Or some combination thereof ... Or something I haven't though of yet...

And of course, I will be using Henrik's regenerative power dump circuit up stream of the driver...

Any suggestions?

Thanks!
Michael

[bogus105]

Hi,
but how ELmChan servo software knows how much current h-bridge drive to motor? there is no sensor at the schematic:/
you wrote "software current limitter" - does maximum pwm value variable involved in it?
i can you tell me how to compile Chans software?
I'm using AVR Studiio but this is foc C only so can't compile original Chans firmware and put it to my avr Pls help!
I'm not familiar with asm as i played with it 10 years ago... now C only.