Hi,
as a very early beginner I am setting up a 3D printer using an old CNC machine. I bought the RUMBA-Board and bulldog XL. The motors are the original ones. At the moment I use the repetier host software and Marlin firmware. I tried repetier-firmware, but had big problems with the homing of all axis (they moved in the wrong direction and switching the direction in the software did not help, but that's not the topic here).

The z-Axis is quite heavy, that means it sometimes moves down, if there is no current applied to the motors.
There is a premounted brake on the z-axis, which I had removed for the first moving tests.
It is a spring with a magnet. Datasheet says "24 VDC 10W" for switching. I found out, that 9 V are enogh to switch the brake. So 12 V should be definetly enough. I would than have < 3W powerconsumption / a curent of 0.2 A.

What is the best way to make the brake release as long as the motors are powered? It would be fine to leave the brake "open", so under power, as long as the motors are not in idle mode.
At the moment I set

#define DEFAULT_STEPPER_DEACTIVE_TIME 0

to not have problems when testing. I want to use the brake for safety reasons.

Does anyone know a simple solution? Maybe my google-experience was to bad to find a already accomplished solution.
Which pin (maybe from Exp3) can be used?
How do I integrate it to the software?

kind regards,
kar.ranseier

Ok, a friend got this idea:

- connect a transistor to the "enable" pin of the used motor.
- the enable-pin is 5 V when the motor is off, 0 when it is on.

So no change in the firmware is needed: perfect!
I will write if the solution worked. By the way: is there anyone reading this? Maybe in the future... ;-)