H bridge motor shield


I was thinking about making a motor shield that has a number " x " of H half bridges being controled by 2x pwm pins.Having a mega lets say the 7 full bridges. Is it posible for that shield to be general purpose,meaning that it will be able to control even stepper motors with or without hall sensors?What kind of issues may I encounter?

Yes, a half-H-bridge is a useful subcomponent of several kinds of driver.

In fact its just a power amplifier with tri-state output - each Arduino pin
is a half-H-bridge since you can make it drive high, drive low or be open.

Half-H-bridges can be combined in pairs to make DC motor drivers or
class-D audio amplifiers (just add output filtering).

With 3 half-H-bridges you have a 3-phase bridge for driving BLDCs.

With 4 you can drive a bipolar stepper (but for chopper drive you also
need current sensing feedback, perhaps a DAC channel and a comparator
per H-bridge.

Some exotic stepper motors have 5 windings and either 5 or 10 wires, these
5-phase motors need 5 half-H-bridges to drive.

So a most general component is a pair of PWM outputs (from the same timer),
a half-H-bridge. For each full H-bridge a differential current monitoring
circuit (+ associated shunts), a DAC output channel and a comparator with
adjustable hysteresis, and an input pin to sense the comparator state. Or something
like that. Yes I have thought about this.

Half-H-bridge driver chips for n-channel MOSFETs are readily avaliable and
you can get 3 in one package for 3-phase bridges (FAN7388 for example).

I was thinking about the half bridges be configured depending the need,for example if I want to drive a 5-phase drive like you said,just tweak the code so the pwm was timed for the given number.

5 phase needs tweaking of the stepper class to support the drive line phasing for 5 phase vs the current 2 phase topology. Motor driver controller ICs modulate the pwm typically on an overall load current, where specialized ones do it on a per phase basis. 5 cascaded D-Type flipflops configured as a synchronous counter will generate the required phases for a 5 phase motor. An XOR gate will be needed between each Q output and the D input of the next stage, the last stage will use the Q' output instead of the Q as did the preceding stages. One input from each XOR is tied to a common direction control pin, a low will result in a forward count and a high will cause a reverse count without invoking any state change on the outputs of the flipflops at the time of the direction reversal.

These days no-one would ever use discrete logic like that except to be retro(!), microcontrollers are much easier and cheaper (once you factor in PCB board cost).

i dont plan on using 5 phase,i was just giving an example,i want to use at most 3 phase,all I wanted to know it its possible and efficient.

Possible yes, efficiency depends on the details, bridges can be highly efficient.

Having one bridge design to match many different sized of motor with full efficiency
across the board is more challenging, things get interesting as the voltage goes up
(more circuit protection is needed). A universal current sensor doesn't exist, each
has a range over which it is reliable (noise affects the low end, power losses affect
the high end).

can someone recoment a half bridge design that can be used?i have a few pcb bits and i was thinking about bulding a 2 axis pcb mill.i have aroung 15 tri phase motors from cd rom and i think that the are up for the task of moving the milling head on the 2 axis.

Well MarkT I guess then that makes me old…too, because I am retro all the way. I view a micro as a commanding officer, not the infantry battalion.