pmdc motor circuit

[Ranger80]

I'm currently trying to design a circuit that will regulate the current/voltage go to and leavin an PMDC motor. A 24V PMDC motor turns a rotating cylinder and at certain points the motor then acts as a generator because the cylinder makes the motor run faster. So im trying to design a circuit that has some sort of a braking system. I only want to brake so keep the motor at a steady speed. Reverse current and voltage has burnt out many motors and power supplies and this circuit will hopefully fix the problem. i know i can use a controller but i just need a simple circuit with a zener and some other simple components......a simple voltage/current regulator......Thanks for all your help.....

 

[OperaHouse]

I would hope that the current entering the motor is the same as the current leaving!

The simplest method would be to have a power op amp that can absorb current as well as supply it to maintain a constant voltage. Theoretically that will maintain a constant speed except for resistance losses. Things burning up is a component selection issue.

 

[benta]

It would be nice to know current, power, if you are actively regulating the 24 V voltage etc.
With the given information you're not going to get a lot of meaningful responses.

Benta.

 

[Comcokid]

There are many ICs, application notes, and articles for regulating the speed of a DC motor. These circuits frequently do a PWM and sample the back EMF of the motor when the PWM is off to regulate the speed. I know Jim Williams of Linear Technology has published circuits for such applications going back 20 years. A quick search at

http://www.linear.com

found some articles.

Overcoming the angular momentum in the mass of the cylinder of your application makes your application just a little different. Maybe you could implement a standard unidirectional control but have a H-bridge such that when the PWM is off it connects the motor to a resistor to brake it.

 

[nbucska]

r80:


Plesae read FAQ240-1032
WEB: <

http://geocities.com/nbucska/>

 

[coconutalley]

I will state the options in order of difficulty and lenght of time required:
1. You are better off with a DC servo amplifier. [Advanced Motion, Copley, etc.]. All you do is call them, get a model#, order it, and hook up [there are setpoint settings].
Many of these have built-in "regeneration" circuits that will handle your "generating" problem and also protect the motor from too much current.

2. If you must built your own, you might try looking at motor driver chips. Companies include: TI [Unitrode}, Allegromicrosystems, ST Thompson, International Rectifier, Hitachi, etc.
The thing to remember is that many of the motor driver
chips do only two quadrant driving which does not handle
regeneration very well. You want 4 quadrant capable operation. Using these drivers chips with MOSFETs can save you time and you don't need to write firmware.

3. Use a DSP or microcontroller, write your own firmware, use gate drivers, MOSFETs, current sensors. This is not trivial and requires knowledge and time. A lot of the companies that sell these ICs have pretty good application notes.