Let the fun begin !!! ???

**PAULRO** · 20-02-2015

Cheers Eddy, i'll update that . the older i get the more cautious i'm becoming just as well i put it up for a critique.

**Neale** · 21-02-2015

I'm not sure if I would bother with the relay switching if you are using a reasonably large value of R. Use something like 4K7, 3W, wired directly to the capacitors, and save a relay contact and associated wiring? Probably about the same current draw as three quiescent drivers, so maybe not worth the effort, but it would drain down the caps even if everything else were disconnected during testing. I must stick a meter across my power supply some time and see what happens - I don't have any bleed resistor in place.

**JAZZCNC** · 21-02-2015

Originally Posted by Neale

I must stick a meter across my power supply some time and see what happens - I don't have any bleed resistor in place.

Probably not a lot.! Depends how you wired the control box.?
If the Drives are kept in the circuit and not removed say thru a relay then they will drain the Caps resonably quickly to within 5V last time I checked.

Not a fan of leaving resistor in all the time as it's creating heat and we want to remove it not make it.!

**EddyCurrent** · 21-02-2015

Originally Posted by JAZZCNC

Not a fan of leaving resistor in all the time as it's creating heat and we want to remove it not make it.!

I agree with this, I tried it and it's amazing how much heat 3 watts can produce, especially in a control panel size box.

**Neale** · 21-02-2015

Personally, I wouldn't bother with the resistor at all. Seems like unnecessary complication, given three or four drivers draining the caps on power-off. Main use would be draining the caps during testing with nothing else connected, but that's a bit artificial anyway. Heating was why I suggested the value I did, which would only be dissipating a watt or so, but why bother?

**JAZZCNC** · 22-02-2015

Originally Posted by Neale

Heating was why I suggested the value I did, which would only be dissipating a watt or so, but why bother?

Depends on how the control is wired.!
One reason to bother is that when a drive faults or E-stop occurs the motors will continue to rotate for fraction of second until power is drained. No big deal you'd think.!! . . BUT. . it is a big deal with Slaved motors if one drive faults and other doesn't because the one that doesn't fault remains under power until power is drained. The faulted drive removes power and stops rotating so the gantry gets racked every time.

**EddyCurrent** · 22-02-2015

Originally Posted by JAZZCNC

Depends on how the control is wired.!
One reason to bother is that when a drive faults or E-stop occurs the motors will continue to rotate for fraction of second until power is drained. No big deal you'd think.!! . . BUT. . it is a big deal with Slaved motors if one drive faults and other doesn't because the one that doesn't fault remains under power until power is drained. The faulted drive removes power and stops rotating so the gantry gets racked every time.

Unless you have the driver fault relays and enable signals integrated into the design, then they all stop together or as close together as possible.