# Power Supply 40v 2a

#### SgtWookie

Joined Jul 17, 2007
22,230
You're trying to control two motors using the same four I/O pins. That's not going to work very well.

You need independent control of both motors.

#### xmen33

Joined Aug 27, 2011
20
i just put the two way in one simulation, just to show u the 3 way

so what about the best way to drive the motor , 1 or 2 or 3 or other way ?

#### SgtWookie

Joined Jul 17, 2007
22,230
None of the methods you've shown have any means of limiting the current through the stepper motors, save for turning the switches off.

You are going to need some method of sensing the current, and controlling it.

#### xmen33

Joined Aug 27, 2011
20
sorry but i don't understand what you mean , is there problem in the design ?

#### SgtWookie

Joined Jul 17, 2007
22,230
Yes.

You apparently are planning on using a power supply that is somewhere in the vicinity of 40v on motors that are rated for 3A; I've already calculated that 6.9v is the maximum voltage to apply if you are not going to use any form of current limiting. If you try to use several times the 6.9v with no current control, you will burn the motors up very quickly, or damage the power supply.

#### xmen33

Joined Aug 27, 2011
20
is 6.9v the max volt the motor can handle ? " who u calculate it ? " , when i buy this motor , the Seller say to me that this motor can handle 3A max and 40V max .
so i suggest use 40v.
Now if i used 6.9V 9A power supply so i don't need current limiting controller ?

#### SgtWookie

Joined Jul 17, 2007
22,230
You can operate the motors on 6.9v without using a chopper circuit. However, you will not get the speed nor torque that you want.

#### xmen33

Joined Aug 27, 2011
20
so what the best volt that will get me a good speed and torch ?

#### SgtWookie

Joined Jul 17, 2007
22,230
As high as you can go without exceeding the 40v limit. However, this means that you have to use a chopper driver. I don't think that you understand how a chopper driver works.

#### xmen33

Joined Aug 27, 2011
20
i found some resource about chopper circuit: "Current limiting is used when a stepping motor is driven
at a voltage that is higher than the motor’s rated
voltage. There are several advantages to driving a
motor at high voltage, namely, the torque and speed
characteristics of the motor are improved. These
parameters are improved because the current in the
motor windings is more responsive to changes made
by the controller."

and the circuit complicated , so if i used the first way " l298 "
http://dl.dropbox.com/u/2193931/p1.JPG
i can avoid using chopper circuit?

Last edited:

#### xmen33

Joined Aug 27, 2011
20
i found some resource about chopper circuit: "Current limiting is used when a stepping motor is driven
at a voltage that is higher than the motor’s rated
voltage. There are several advantages to driving a
motor at high voltage, namely, the torque and speed
characteristics of the motor are improved. These
parameters are improved because the current in the
motor windings is more responsive to changes made
by the controller."

and the circuit complicated , so if i used the first way " l298 "
http://dl.dropbox.com/u/2193931/p1.JPG
i can avoid using chopper circuit?

#### SgtWookie

Joined Jul 17, 2007
22,230
If you want to operate those motors with a supply voltage above 6.9v, you will have to use a current limiting circuit, and a chopper driver is the best way to do that.

If you don't mind losing torque and speed, you can go with the simple schematics of just the MOSFETs - but you'll need separate inputs for each motor.

The L298 by itself does not have any chopper driver controls in it; it needs the L297 to provide that function.

I'm sorry, but it's late and time for me to retire for the evening.