Sorry if this isn't the right place (I'm fairly new).
I've heard that there are 'issues' with the stepper drivers letting out their magic smoke if they are disconnected when powered.
Does anyone here know the failure mode that this causes?
I'm _considering_ designing a slightly different stepper driver (although still based on an A49xx or DRV88xx chip) that mounts directly to the back of the stepper motor itself. However, I'll probably be wanting a bit more than the 2A of drive current, so I'm looking at using the 2* internal DMOS full bridges as 'pre-drivers' for secondary (higher current) full bridges (which would still use the sense inputs of the Allegro / TI driver to allow PWM current limiting).
Obviously, I'd be LOSING the internal thermal monitoring ability of the chosen driver chip in order to gain the additional current drive capabilities of the beefier full bridges, but this is something I can accept.
Since the driver will be direct-mounted and hardwired to the motor itself, there's less chance of an inadvertent disconnect of the motor whilst powered up (which might help to keep the smoke in).
I'm leaning more towards TI over Allegro (for the extra 1/32 microstep setting) with something like a pair of DMHC3025LSD as the full bridges.
Ideally, I'd like to use a form factor that enabled use on Nema17, 23 or 34 motors (snap the PCB to the desired size).
1 * power connector (Motor supply)
1 * signal connector (Step/Dir/Gnd being bare minimum - possibly Enable/Fault/Home/MSn too)
1 * Dipswitch or header (to allow local setting of MSn pins)
Not sure what else I've missed yet...
In future, I'm thinking of doing likewise for the thermistor inputs and heater outputs too.
i.e. Simple 'decentralisation' leading to the elimination of the quasi traditional RAMPS type board.
I've heard that there are 'issues' with the stepper drivers letting out their magic smoke if they are disconnected when powered.
Does anyone here know the failure mode that this causes?
I'm _considering_ designing a slightly different stepper driver (although still based on an A49xx or DRV88xx chip) that mounts directly to the back of the stepper motor itself. However, I'll probably be wanting a bit more than the 2A of drive current, so I'm looking at using the 2* internal DMOS full bridges as 'pre-drivers' for secondary (higher current) full bridges (which would still use the sense inputs of the Allegro / TI driver to allow PWM current limiting).
Obviously, I'd be LOSING the internal thermal monitoring ability of the chosen driver chip in order to gain the additional current drive capabilities of the beefier full bridges, but this is something I can accept.
Since the driver will be direct-mounted and hardwired to the motor itself, there's less chance of an inadvertent disconnect of the motor whilst powered up (which might help to keep the smoke in).
I'm leaning more towards TI over Allegro (for the extra 1/32 microstep setting) with something like a pair of DMHC3025LSD as the full bridges.
Ideally, I'd like to use a form factor that enabled use on Nema17, 23 or 34 motors (snap the PCB to the desired size).
1 * power connector (Motor supply)
1 * signal connector (Step/Dir/Gnd being bare minimum - possibly Enable/Fault/Home/MSn too)
1 * Dipswitch or header (to allow local setting of MSn pins)
Not sure what else I've missed yet...
In future, I'm thinking of doing likewise for the thermistor inputs and heater outputs too.
i.e. Simple 'decentralisation' leading to the elimination of the quasi traditional RAMPS type board.