Above photo is schematic for wiring electromagnetic brake (from dimensionengineering) for Sabertooth 2x32. Because Im electric stupid, I have some questions, hope someone with great knowledge can explain:
The 2 black wires are the MA1 and MA2 output on Sabertooth. Am I correct?
The 2 diode at end of each MA1 and MA2 are for filtering the negative and only let the positive pass through. Am i correct?
The brake feed by the positive (that pass through the 2 said diode), and the negative from battery. Am i correct?
And what is the purpose of the last diode parallel to the brake?
It’s a bit unfortunate that Dimension Engineering doesn’t provide a wiring diagram as part of their manual, but they do write out what is wired where.
Sabertooth + Brakes
The power outputs can also be used to operate electromagnetic brakes. Systems such as wheelchairs often have brakes to prevent rolling away when power is removed. Brakes are also used in CNC machines and automation to hold alignment when power is removed or reduce power consumption. In brakes mode, the brakes automatically disengage when motion is commanded, and engage when the motor stops. When using Brakes mode, the P1 output is linked to the M1 motor output, and the P2 output is linked to the M2 motor output. With the brake timing changed, brakes mode can also be used to control the field in a shunt wound or separately excited motor. Brakes mode must be selected and configured from the Power Outputs tab using the DEScribe software.
If you are using the power outputs for electromagnetic brakes, the positive side of both brakes connect to the B+ terminal. The negative side of the M1 brake connects to P1, and the negative side of the M2 brake connects to P2. Remember that to use brakes you must set the power outputs to brakes mode using the DEScribe PC software.
Software & Braking
In Brake mode, the power outputs are used to operate electromagnetic brakes. P1 corresponds to motor 1 and P2 corresponds to motor 2. When the motor stops, the brakes activate after the Turn-On Delay. When the motor is commanded to move again, the brakes deactivate immediately, but the motor does not turn until the Turn-Off Delay has elapsed. If an emergency stop is commanded, the brakes will activate after the E-Stop delay has elapsed.
Brakes mode can also be used to drive the field of a shunt or compound wound motor. To do this, connect one side of the field to B+ and the other side of the field to the P1 or P2 power output. Turn all the timings to 0 seconds.
The 2 black wires are the MA1 and MA2 output on Sabertooth. Am I correct?
Note that the Sabertooth 2x32A is a dual motor controller and “MA1” and “MA2” are each channel. Each motor + brake would be wired accordingly. For example the motor connected to the two M1 terminals M1A and M1B:
The 2 diode at end of each MA1 and MA2 are for filtering the negative and only let the positive pass through. Am I correct?
Not quite. You don’t want the motor to push current back to the Sabertooth via the M1A and M1B (or M2A, M2B) terminals. Bad stuff would happen (burnt controller).
The brake feed by the positive (that pass through the 2 said diode), and the negative from battery. Am I correct?
Kind of. The brake needs common ground (GND) with the battery, and the motor provides the positive.
And what is the purpose of the last diode parallel to the brake?
Same issue - don’t want to push current (when braking) where it shouldn’t go.
Rethink your concept of how a diode functions. They are not filters, meaning some energy is blocked and some passes thru. Think of them as dikes or dams. No energy flows into the symbol end that has the bar on it, and current can only flow in the direction of the arrow of the symbol. They are a one-way street that moves in the direction of the arrow. So when you read a schematic, and are following the current paths, and encounter the bar first, then the arrow, you can not follow it into the diode. that bar is the dam. If you are following the flow and encounter the arrow first, then the bar, that is the direction the diode is allowing current to flow.
Since the flow path is being shared, the diodes are there to prevent any feedback that may appear on the negative rail from entering the exit connection of the Break module. It would have internal diodes with it that would be forcing the current flow to go around the module, thru the Break Protection Diode (the bottom diode) and reenter the Break module thru the proper connection. This would be serving also as a brake to any of that feedback current, using it up so that the platform comes to a halt, even with feedback present, from somewhere. Current takes the path of least resistance, so that brake module has diodes and/or resistors in it, in order to redirect the current down into the diode, (the arrow side has little resistance if any) and then since the two protection diodes are present, they are blocking the current from reentering the motor, so the current has no other place to flow to except back into the brake, over and over, until there is no longer any stray feedback current present.
