Difference between revisions of "Motor driver"
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A DC motor controller that is "reversing" generally uses an "H bridge". | A DC motor controller that is "reversing" generally uses an "H bridge". | ||
| − | + | A single phase AC motor is generally driven in the same way as a DC motor, however instead of operating the motor drive as a constant DC voltage (in either the 'forward' or 'reverse' direction) the AC motor is driven by an approximation to a sinewave. This approximation is created using the H bridge and driving it with a PWM input such that both the positive and negative voltage periods are the same. This is normally acheived either using a sawtooth waveform compared against a sine wave reference, or is done using a lookup table in a microcontroller. | |
| + | A similar method is used to drive multiphase (3-phase) AC motors, however instead of just using an H bridge, only a half H bridge is used per phase. Each phases half bridge is then driven in the same manner as for the single phase motor, with a phase difference between the phases as appropriate. | ||
((fill in more details here...)) | ((fill in more details here...)) | ||
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| − | Some motor controller circuits are such that, if the software accidentally sets the "wrong" pins hi or lo, you get a short circuit | + | Some motor controller circuits are such that, if the software accidentally sets the "wrong" pins hi or lo, you get a short circuit through the output drivers. This will generally cause a high current to flow, due to the low on state resistance of the output drivers, which may damage other electronic components before finally blowing the supply fuse. |
| − | Other motor controller circuits are such that, if the software accidentally sets the "wrong" pins hi or lo, the worst that could happen is the motor spins the wrong way. | + | Other motor controller circuits are such that, if the software accidentally sets the "wrong" pins hi or lo, the worst that could happen is the motor spins the wrong way. These circuits ensure that both branch drivers aren't on at the same time, preventing a short circuit through the drivers. This is done through the use of a blanking time. This blanking time is the time taken to switch from one driver on to the other driver on, which is accomplished by turning off the previously on driver, before waiting a set time before turning the other driver on. This ensures that both drivers aren't simultaneously on causing the short circuit condition. |
Guess which type of design I prefer? | Guess which type of design I prefer? | ||
Revision as of 21:39, 26 June 2006
What are you looking for here?
- servo motor controller
- stepper motor controller
- DC motor controller ("brushed")
- AC motor controller ("brushless")
... or what?
A DC motor controller that is "reversing" generally uses an "H bridge". A single phase AC motor is generally driven in the same way as a DC motor, however instead of operating the motor drive as a constant DC voltage (in either the 'forward' or 'reverse' direction) the AC motor is driven by an approximation to a sinewave. This approximation is created using the H bridge and driving it with a PWM input such that both the positive and negative voltage periods are the same. This is normally acheived either using a sawtooth waveform compared against a sine wave reference, or is done using a lookup table in a microcontroller. A similar method is used to drive multiphase (3-phase) AC motors, however instead of just using an H bridge, only a half H bridge is used per phase. Each phases half bridge is then driven in the same manner as for the single phase motor, with a phase difference between the phases as appropriate.
((fill in more details here...))
Some motor controller circuits are such that, if the software accidentally sets the "wrong" pins hi or lo, you get a short circuit through the output drivers. This will generally cause a high current to flow, due to the low on state resistance of the output drivers, which may damage other electronic components before finally blowing the supply fuse.
Other motor controller circuits are such that, if the software accidentally sets the "wrong" pins hi or lo, the worst that could happen is the motor spins the wrong way. These circuits ensure that both branch drivers aren't on at the same time, preventing a short circuit through the drivers. This is done through the use of a blanking time. This blanking time is the time taken to switch from one driver on to the other driver on, which is accomplished by turning off the previously on driver, before waiting a set time before turning the other driver on. This ensures that both drivers aren't simultaneously on causing the short circuit condition.
Guess which type of design I prefer?
A random collection of semi-related links (please prune out the irrelevant ones):
