Stepper motor dead?
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It's not common for a stepper to die, but if there are not two connected pairs of coils then it's a dead motor. More importantly, check the duet board stepper driver chip for that motor channel and make sure it doesn't have any visual evidence of a hole or pit on the top casing, or that it doesn't get very hot when powered up. Swap a known good motor onto that channel and test it. It might be a driver chip failure that killed the motor, which is a more expensive problem to rectify. A new motor is not a particularly big problem.
My understanding is that high speed does not necessarily place more demand on motors electrically than when moving slowly. In slow movement they are still using all the energy supplied (its constant current remember) to hold position; when moving fast the current remains the same but the switching from one coil to the next occurs faster. If you greatly increased the current before it failed that could explain it.
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thanks for the information DjDemonD.
stepper driver is working fine.
I want to know what can fry a stepper motor other than current. (current was well below the rated current).
running duet with a 24V supply.
how does a stepper motor run with a 24v and 12v with same rated current? (I have very basic knowledge of motors) -
what should be the rated voltage for stepper motor if I'm using a 24V supply?
documentation says less than 3V. can someone explain this? -
I am not an expert DC is the motor expert around these parts, but my understanding is that the amount of time the current is applied to a coil is less at higher voltage. So at 12v you need a longer pulse of power to move the motor 1 step (or microstep) than at 24v, but the current applied is the same. I am quite sure the real explanation is way more complex than my interpretation.
Th voltages on the motor specs are not directly related to the voltage you drive them with. There is a relationship but have a dig around my understanding is you want to be a good way above the voltage rated on the motor to get good operation if you are close to it or lower than it, it doesn't work well.
In any case what can cause it to fail - badly made motor would be my best guess. It could be there was a slight intermittent connection between the motor and duet, whilst these later duet boards are designed to survive this the motors may not, as this causes high voltage spikes which is why it is never recommended to disconnect a motor when powered up.
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thanks for the help.
there is no logical explanation to say that motor fried because of an increase in speed (from pronterface).
and motor stopped working right after I increased the speed. -
Not that I am aware of, coincidence. The motor is working hard when its holding position, as the coils are energised, making it go faster is just alternating the current to the coils to make it spin rather than hold.
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Some sort of PWM is used to regulate the current through stepper's coils with different supply voltages. TMC2660 has 2 type of PWM not sure which one is used in Duet firmware. Rated voltage is the max voltage that can be applied when driving the stepper in pure voltage mode when current through a coil is limitted by its resistivity (multiply Imax by Rcoil and you get it). BTW how do you check that the driver chip is OK, visually? It is a chance that driver's nMOS switches got short to VIN and/or GND and they fried the coil so it is wise to check driver's chip with a multimeter. PWM in standstill is static for coils in stepper while when fast moving there is constant changing in driving pulse width so many transient events that might provoke the fail (bad electric contacts could give that for example).
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Are you certain that the problem isn't in the crimp connections to the stepper motor wires?
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Are you certain that the problem isn't in the crimp connections to the stepper motor wires?
yes I'm certain. it was working fine before.
i extended the wires using solder and heat shrink. -
@zov:
Some sort of PWM is used to regulate the current through stepper's coils with different supply voltages. TMC2660 has 2 type of PWM not sure which one is used in Duet firmware. Rated voltage is the max voltage that can be applied when driving the stepper in pure voltage mode when current through a coil is limitted by its resistivity (multiply Imax by Rcoil and you get it). BTW how do you check that the driver chip is OK, visually? It is a chance that driver's nMOS switches got short to VIN and/or GND and they fried the coil so it is wise to check driver's chip with a multimeter. PWM in standstill is static for coils in stepper while when fast moving there is constant changing in driving pulse width so many transient events that might provoke the fail (bad electric contacts could give that for example).
i connected another motor to the same driver and it worked. still waiting for my replacement to come.
how do i make sure its not the driver before i fry another motor.
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If another motor worked then it is almost surely not a driver fault. As David said it could be intermittent crimp connections so check them twice before using a new motor. After all it could be just a bad quality motor.
