Let the fun begin !!! ???

**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.

**PAULRO** · 22-02-2015

Initially i was not going to use a resistor because of the drivers draining as pointed out. i've read a lot of posts that discuss this and i know a lot of the experienced`builders don't bother because of the reasons stated. but i will be using a relay in the e/stop circuit anyway and it will have an empty N/C contact available so it's an extra terminal for the resistor and an extra piece of cable to hook it in. i think that's all that's required anyway? if i don't use it i will definitely integrate the fault relays and enable signals as Eddy suggested. on another note my toroidal coil arrived friday. i should have the cap and bridge this week, hopefully. the coil has 3 windings http://www.airlinktransformers.com/c...nge/CM0625225/ the colours are as follows: coil 1 BROWN / BLUE 1.6 ohms
coil 2 BLACK / RED 0.5 ohms
coil 3 YELLOW / ORANGE 0.5 ohms
so i assume from this that the following
Coil 1 = mains supply 230 vac
coil 2 = 25vac
coil 3 = 25vac
and if i join BLACK and YELLOW together power up and meter across RED and ORANGE i should get 50 vac OR 0 vac . a change of the secondary coil arrangement if i read 0 volts. i will try it tomorrow to see.

**JAZZCNC** · 22-02-2015

Originally Posted by EddyCurrent

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.

Yes and exactly why I said depends on how control is wired.!! . . . Several why's to do same thing. Fact still remains that it's NOT ok if control NOT wired in correct Manner.!