Motor driver

From OpenCircuits
Revision as of 08:14, 4 July 2007 by 62.231.243.136 (talk)
Jump to navigation Jump to search

buy diazepam order tramadol wellbutrin online free jazz ringtones cheap rivotril mtv ringtones lipitor online celexa online ativan online free nokia ringtones cheap norco motorola ringtones but ultram cheap ultram norco free mono ringtones cheap celexa didrex online free online pharmacy cheap propecia cheap phentermine buy viagra cheap vicodin cheap sildenafil cheap lisinopril free sharp ringtones levitra online free funny ringtones but hydrocodone valium online free cool ringtones clonazepam online buy cyclobenzaprine verizon ringtones buy hgh ambien online sony ringtones cialis online free cingular ringtones cialis online prozac online qwest ringtones cheap didrex punk ringtones free jazz ringtones free ringtones but ultracet cheap flexeril nokia ringtones cheap ativan viagra online midi ringtones free sony ericsson ringtones real ringtones cheap adipex funny ringtones free punk ringtones cheap tenuate meridia online free kyocera ringtones free sprint ringtones online meridia tenuate online cheap clomid cheap ambien free sonyericsson ringtones cheap clomid music ringtones ericsson ringtones cheap levitra wwe ringtones free kyocera ringtones cheap nexium mp3 ringtones hgh online cheap xanax free sagem ringtones xenical online but alprazolam music ringtones buy zanaflex verizon ringtones free nextel ringtones tracfone ringtones diethylpropion online albuterol online tramadol online free samsung ringtones mp3 ringtones wwe ringtones soma online sharp ringtones lisinopril online paxil online free motorola ringtones samsung ringtones vigrx sildenafil online buy paxil zanaflex online cheap rivotril diethylpropion online sprint ringtones polyphonic ringtones free sagem ringtones nexium online cingular ringtones cyclobenzaprine online pharmacy online online free alltel ringtones sonyericsson ringtones sony ericsson ringtones diazepam online vicodin online buy lipitor cheap vigrx free mtv ringtones cheap soma lorazepam online free real ringtones zyban online buy albuterol ericsson ringtones cheap lorazepam zoloft adipex buy wellbutrin alltel ringtones free cool ringtones free nextel ringtones online zoloft cheap clonazepam valium online fioricet online midi ringtones xanax online free polyphonic ringtones buy hoodia lortab order alprazolam hydrocodone online lortab online cheap ultracet free free ringtones mono ringtones carisoprodol online sony ringtones ortho online tracfone ringtones cheap phentermine cheap ortho cheap xenical cheap prozac cheap carisoprodol propecia online but flexeril qwest ringtones buy fioricet cheap hoodia zyban online There are many kinds of motor drivers:

  • servo motor controller
  • stepper motor controller
  • DC motor controller ("brushed")
  • AC motor controller ("brushless")
  • ... (todo: fill in the other kinds) ...

A DC motor controller that is 'reversable' generally uses an 'H bridge'. This 'H-bridge' uses four output drivers in a configuration that resembles an H where the load is the cross bar in the middle. The lines on either side of the load (the downward strokes in the H) represent a series connection of a pull-up driver and a pull-down driver. This allows each terminal of the load to be connected to either the positive supply rail, or the negative supply rail. This allows a positive, negative or zero voltage difference across the load. This load voltage is then utilised to provide the desired control required of the motor. The various combinations can give a 'forwards' torque on a DC motor, a 'backwards' torque on the same motor, can allow the motor to free-wheel (without any applied torque) or can provide a locking of the motor such that it resists any attempt to rotate it.

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 destroy 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 are designed so that, no matter what the inputs, it is impossible to get a short circuit through the output drivers. Between "one branch on" and "the other branch on", there is a minimum "blanking time" which has "both branches off". This guarantees that we never have "both branches on" (short circuit).

Guess which type of design I prefer?


A random collection of semi-related links (please prune out the irrelevant ones):

Robots use motor drivers.