pwm schematic help required please?

[Tel 27]

No. In fact it's exactly as I'd expect from the information that you've supplied to date. If you was to set the speed to 10% of max (assuming you've calibrated it) then I'd expect the spindle to be OFF. And above about 25% I'd expect it to be full-on. This is simply the (wrong) application of the analogue output from the BOB to the opto-isolator input to the speed controller, which instead expects a PWM input.

Simply. Connect the BOB output pin P1 to ribbon Pin 3. Connect the Ground used for the BOB to ribbon Pin 4. There is no need for any of the resistors.

Rough-arsed sketch - the PC output pin-1 is a digital PWM output. The BOB routes this to two different outputs - the BOB "P1", which is a facsimile of the PC output - and is the signal you need. There's also an on-board (the BOB) integrator that converts the PWM to the analogue output, that you don't need. Your speed controller takes a digital PWM input and uses this either to generate the analogue drive to the onboard speed controller, or simply uses this to drive the onboard MOSFET to drive the spindle. Regardless, the important bit is that the speed controller around the pin 3/4 terminals is designed around having a Digital PWM input, and NOT an analogue input (which, confusingly, is derived from a PWM source)

confused really is the term that springs to mind!

how exactly would I calibrate the speed?

[Doddy]

Just do this:-
Connect the BOB output pin P1 to ribbon Pin 3. Connect the Ground used for the BOB to ribbon Pin 4. There is no need for any of the resistors.


To answer your question:-
Google Mach3 Spindle Settings to find out how to setup. What I meant by "calibrate" was perhaps misleading, my fault.

My intent, when you issue lets say a speed of S1000, that the actual speed would be a ratio of the commanded speed vs the maximum spindle speed - so if the max spindle speed was set within Mach to 2000rpm, then a S1000 command would set the PWM output at 50% Mark/Space. If the max spindle speed was set within Mach at 4000rpm, then the same S1000 command would set the PWM output at 25% Mark/Space ratio. My comment was to ensure that the commands that you issue to test the speed control would respond with a sensible response from the PC/machine.

[Tel 27]

Just do this:-
Connect the BOB output pin P1 to ribbon Pin 3. Connect the Ground used for the BOB to ribbon Pin 4. There is no need for any of the resistors.


To answer your question:-
Google Mach3 Spindle Settings to find out how to setup. What I meant by "calibrate" was perhaps misleading, my fault.

My intent, when you issue lets say a speed of S1000, that the actual speed would be a ratio of the commanded speed vs the maximum spindle speed - so if the max spindle speed was set within Mach to 2000rpm, then a S1000 command would set the PWM output at 50% Mark/Space. If the max spindle speed was set within Mach at 4000rpm, then the same S1000 command would set the PWM output at 25% Mark/Space ratio. My comment was to ensure that the commands that you issue to test the speed control would respond with a sensible response from the PC/machine.

Well, that didnt work either, I'm getting to the end of my tether with it now, got a few things I'd like to do with it looming large (been calling in favours elsewhere too long now)
Is there anyone in the UK I could take it to?, (preferably in the North East but it's easily transportable in my van)
Happy to pay someone for their time....

[Voicecoil]

If you can't find anyone over in the NE, I'm not too far away ont' t'other side of the Pennines - not exactly on your doorstep but at least the roads are good. Shame, I was over your way for a guitar show back at the end of March, could have dropped round and sorted it.