Motor Contoller (Motor Mind B) & H-Bridge

Rusty78

Hi,
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··· Just wondering what the difference is between a motor controller (like the Motor Mind B ) and an H-Bridge. This must be an incredibly basic question so please forgive me. Any help·/ document referrals would be greatly appreciated.
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Cheer mates,
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R.K.
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Bruce Bates

G'Day Rusty -

At the possible risk of starting a symantics or definition war, here goes. These are my own definitions, but they probably follow most industry standards at least in concept.

motor controller - a functional electrical, electronic, or electro-mechanical device which can change the operating profile or dynamic characteristics of a motor, and thus its speed, direction, rotational characteristics, and/or operability. Generally applied to electric motors.

The simplist motor controller I can imagine is two wires which are either touching or not; making or breaking the electrical circuit which supplies voltage and current to a motor. When touching, they complete a circuit, permitting a motor to rotate. Next to that is a mechanical switch which brings some formality and safety to the completion of the circuit. This merely offers ON and OFF control, and no sophistication.

At the next level of motor control sophistication, one adds the ability to change direction. Thus, the two possible states are ON and OFF, and the two posible modes of ON are FWD and REV. This is where a simple H-Bridge or a douple pole double throw switch or relay is found. A slightly more sophisticated H-Bridge will also include dynamic braking. This is accomplished by shorting the power terminals together, when no power is applied to the motor. Some elementary speed control can be realized through the use of PWM of the power to the motor, thus varying the instantaneous voltage applied to the motor.

At the next level up from this, we can control the state (ON, OFF), direction (FWD, REV), dynamic braking (ON, OFF) and control the rotational speed of the motor. This can sometimes be done with multiple switches or relays, through the use of motors with multiple windings. This method usually provides two or three speeds (HIGH, MED, LOW). Without the availability of multiple motor winding, this is generally best accomplished by an electro-mechanical or electronic device designed for this purpose. Such devices offer some sort of finer, infinite speed via a contol lead, or speed control parameter, which the user can change at will. The Motor Mind modules fall into this category. There is a bit more sophistication here, however, as the Motor Mind modules also permit the optional input of a feedback (tachometer) signal for use in loop control of the motor. It also has the ability to accelerate or deaccelerate a motor based on user supplied speed profile commands.

There are even more levels of motor control sophistication, but the H-Bridge, and Motor Mind modules have been simply covered, so I'll stop here. I hope you found this informal bit of information handy and helpful.

Regards,

Bruce Bates

Rusty78

Cheers Bruce,

Thank you kindly for the information, it was clear and concise! This pretty much clears up / confirms my original assumption - that a motor controller like the motor mind B offers is a slightly more sophisticated form of motor control than an H-Bridge. Just out of curiosity, where does the name "H-Bridge" come from?

Thanks agian,

Cheers,

R.K.

Bruce Bates

Rusty -

This should answer your question better than I could:
http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/

Regards,

Bruce Bates

Amaral

Great Tutorial .

Does anyone has one for MOSFET ?

Thanks in advance

Ricardo Amaral

Rusty78

Thanks again Bruce..that clears everything up..yeah, great tutorial indeed!

Cheers,

R.K.