View Full Version : [HELP] 6 Axis B.O.B with spindle control
30-09-2014, 10:46 PM
Just wondering if anyone has tried this B.O.B. which has built-in spindle control? It is 6 axis, opto-isolated and has control for a VFD. Seems to have a lot of features for not much money (approx £15). Too good to be true??http://www.ebay.co.uk/itm/151085224178
01-10-2014, 12:12 PM
There's no mention of a 'charge pump' feature if that's important to you otherwise what's to loose at that price even if you just use it for extra I/O in an existing system ?
01-10-2014, 03:48 PM
I had a BOB with a charge pump and the only way I could get the board to work was by disabling the thing. Most of the opinions I have seen are of the order that it is difficult to get the signals sync'd to make the charge pump function. I for one, wouldn't be bothered about having one. I suppose it is the ultimate safety feature if the spindles and steppers remain lifeless :highly_amused: How about this BOB, http://www.ebay.co.uk/itm/251652222037?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT you can get it cheaper from China, but this one boasts UK stock (but the one they would send you comes from China :hysterical:).
01-10-2014, 05:05 PM
Problem with these cheap Bob's is they often have cheap and slow Optoisolators which can cause problems with missed steps etc but I'm in the same Camp as Eddy for £15 it's worth a punt.! . . . . Ok for extra I/O so long as timing isn't critical.
Charge Pump take it or leave it, better to have but not end of world if not.!
01-10-2014, 09:44 PM
OK, so someone has to ask- What is a charge pump? what does it do? Why is it or isn't it neccessary? I know that this does not affect me as my two routers are servo propriety machines with servos and dedicated controllers and do not use MAC etc., but I still wonder about what a charge pump does!!! Thanks, G.
01-10-2014, 09:59 PM
Here's an extract from my breakout board manual
"The charge pump uses the 12 kHz signal from the parallel port generated by the CNC software to operate a logic circuit that gives an active low output. Any piece of machinery that uses powerful motors can be dangerous if controlled by a computer that can be in an unknown state while being powered up or in a software crash condition. Using the charge pump circuit to disable power to motors is a safety device in that it only operates when the software is running correctly and under user control. The charge pump circuit is also used to disable the output signals so even if your stepper boards do not have an enable pin they will be disabled automatically when the charge pump signal is not present."
01-10-2014, 10:09 PM
My simplistic brain understands it thus :- Mach3 or other control software puts out a signal that says it is operating. That signal 'pumps up' a capacitor on the BOB. when that capacitor reaches a certain voltage it enables the circuits, so motors will move, relays will click and spindles will spin. Others may offer a more technical explanation, but my mind can't cope with too much. :stupid:.
I never got it working on the BOB, probably because it was never set up properly on the output pinout in Mach3. The company in Devon that I got the machine from sent me an xml file (Mach3 parameters) and I just used that, when the charge pump didn't work, in retrospect it appears they didn't have a clue why. So it was disabled on the BOB and left at that. At the moment I have not got the machine computer connected up, so I can't look into how it was set up (or not, as the case may be) in Mach3. I will bet that it wasn't enabled !!!
02-10-2014, 12:15 AM
I currently have a PCPPS breakout board from http://www.diycnc.co.uk which has a charge pump (works OK with LinuxCNC) but it is NOT opto-isolated and doesn't have a spindle control. The above website can supply a separate spindle control board at a cost of £25 - £30, so total cost is around £45 for a B.O.B. and spindle controller.So http://www.ebay.co.uk/itm/251652222037 (as suggested above) seems like a good alternative. At half the price, I can afford to buy 2 and keep one as a backup for replacement or another project.Anyone using the above board in their project? Reliable?
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