1 H-Bridge to control Multiple Actuators

[patpatpat]

I am trying to use 1 H-bridge circuit to control 6 actuators. Is it possible?

I know how H-bridge, BJT, MOSFET, and stuff work. I am a undergraduate EE senior, so I know a bit

Thanks for the help!

Pat

 

[dknguyen]

YOu can if the H-bridge is big enough to handle the combined load of all the motors. THey will also do the exact same thing (no different movements between motors). YOu just wire them all in parallel and wire the whole thing as a single load to the H-bridge.

 

[patpatpat]

I want to control them independently. I know I can make them all move the same way.

It doesnt seem like what I want can be done.

 

[dknguyen]

Then no, if you need to do anything with them independently (either moving them, or even using independent feedback to control them as one) then no, you cannot.

 

[patpatpat]

Let me also add this:

Only one actuator will be moving at a time.

 

[dknguyen]

You could use something like a giant mux (double throw, or single-throw with all the motors having a single common ground connection). BUt this would be a very big, very high power mux that you woudl have to manually build. By the time you finished (especially if it's a solid state mux), then you'd have pretty much built an H-bridge that MUST be cascaded into your original H-bridge. You might as well just build 5 more H-bridges.

And it would not stop the motors that aren't being controlled form drooping and losing position.

If you are thinking about making the H-bridge quickly refresh the position of each motor and then jump to the next one, this would involve 1/6th the holding power the H-bridge is capable of, or 6x the switching speed which would overheat the H-bridge. The switching speed required for this also necessitates a solid-state mux (and not simple relays) which defeats the purpose because the work of building such a solid-state mux would be the exact same work involved in building more H-bridges.

THe onyl situtation where it might be feasible to do anything really is if these were servo motors that were driving worm gears that would hold their position unpowered. You could mux the feedback signals along with the motor power. And you'd have to use relays because the additional work would be minimal and simple. As soon as you build a solid-state mux, you need gate drive and protection circuitry which would be exactly as if you built more H-bridges.

 

[mneary]

If the disadvantages outlined by dknguyen are acceptable, then you could use relays (DPDT) to select which motor that you drive.

But it would be much more practical to use one DPDT relay plus a single transistor for each motor. (Transistor PWM, relay H-bridge.)

 

[KMoffett]

If the disadvantages outlined by dknguyen are acceptable, then you could use relays (DPDT) to select which motor that you drive.

But it would be much more practical to use one DPDT relay plus a single transistor for each motor. (Transistor PWM, relay H-bridge.)

Why a DPDT? Positive lead from all actuators to one terminal of the H-bridge. Negative lead from each actuator to each SPST relay (NO) terminal. (C) terminal from all relays to the other H-bridge terminal. Might save a few bucks if these are high current relays.

Or SPDT relays with (C) also tied directly, or through a low value resistor, to (NC) to provide braking action when the actuator is not in the H-bridge.

And are you thinking of PWM the relay?

Ken

 

[patpatpat]

Thanks everyone. I am going to build 6 H-Bridges instead then.