Motor driver

From OpenCircuits
Revision as of 08:07, 29 April 2007 by 67.110.67.231 (talk)
Jump to navigation Jump to search

free sagem ringtone ativan online mono ringtones lorazepam online free ringtones free mono ringtones free real ringtones ativan online buy phentermine cheap norco ericsson ringtones cialis online ultram online nokia ringtones cheap levitra free real ringtones ericsson ringtones cheap ortho free free ringtones free samsung ringtones order cyclobenzaprine cheap wellbutrin punk ringtones cool ringtones clomid online free alltel ringtones cheap lortab online diazepam sagem ringtones ativan online motorola ringtones free nextel ringtones meridia online free nokia ringtones paxil online sony ericsson ringtones best bonus casino online sprint ringtones alltel ringtones buy xenical tramadol online buy fioricet polyphonic ringtones buy carisoprodol ativan online ambien online alltel ringtones clomid online generic alprazolam free samsung ringtones free nokia ringtones adipex online free verizon ringtones free kyocera ringtones free tracfone ringtones qwest ringtones generic xanax generic clonazepam buy xenical free cingular ringtones cialis online generic alprazolam cheap nexium fioricet online free funny ringtones free mp3 ringtones ultracet online ativan online free verizon ringtones generic diazepam ericsson ringtones rivotril online ringtones cheap carisoprodol cheap xanax free free ringtones free tracfone ringtones vicodin online free wwe ringtones phentermine online cyclobenzaprine online verizon ringtones hydrocodone online xenical online levitra online hydrocodone online meridia online nokia ringtones cheap ultram soma online order propecia buy ativan cheap adipex lorazepam online samsung ringtones mono ringtones sprint ringtones soma online celexa online vicodin online cialis online sonyericsson ringtones canadian casino online cyclobenzaprine online qwest ringtones polyphonic ringtones buy ultram cheap xanax free tracfone ringtones free qwest ringtones cheap lipitor ultram online buy nexium free sony ericsson ringtones cheap ativan cheap xenical cialis online carisoprodol online free sagem ringtones generic meridia free nextel ringtones tramadol buy carisoprodol mixing valium and xanax norco online generic valium buy cyclobenzaprine clonazepam online kyocera ringtones adipex online free sonyericsson ringtones carisoprodol online cheap hydrocodone sony ericsson ringtones cheap meridia order zanaflex cingular ringtones cheap viagra wwe ringtones free nokia ringtones free mtv ringtones cheap vicodin generic meridia sony ericsson ringtones free sagem ringtones free qwest ringtones sony ringtones cheap tramadol free qwest ringtone polyphonic ringtones but xanax sagem ringtones free funny ringtone sony ericsson ringtones viagra online free ringtones free samsung ringtones ambien online valium half life ultram online free sony ericsson ringtones generic phentermine valium side effects valium online diazepam online free samsung ringtone hoodia online diazepam online free mp3 ringtones viagra online online xanax soma online but adipex order cialis pharmacy online online cheap soma hydrocodone online buy didrex lorazepam online funny ringtones cheap sildenafil cheap levitra free tracfone ringtone casino craps online free ringtone cheap didrex generic cialis free mp3 ringtone nextel ringtones free jazz ringtones free motorola ringtones punk ringtones wellbutrin online cool ringtones alltel ringtones free alltel ringtones tramadol online free nokia ringtones viagra generic adipex 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.