Can any one explain this way to drive a stepper??

[wini]

Hi there

I want to ask about driving stepper motor.
If i consider the following scheme to drive the stepper motor [ Attached ]:

i use two limit resistor to limit the current at 1 A for each coil .
If i want to run the motor in FALL STEP mode, each coil can take 1A by the resistors, no problem.

But if i want to run the motor in HALF STEP mode, there are two cases which the current must be 2A a flows through each resistor ( that when sequences active the coils 1 and 2 OR 3 and 4 ) to be divided to 1A in each coil.
That means the value of the limit resistor must be decreased .

Then, in the other two cases in the sequences that the current must be 1A through each resistor ( that when sequences active the coils 2 and 3 OR 1 and 4 )[ like running in fall step mode] .
That means the value of the limit resistor must be increased .

my question is
How can i use 2 limit resistors and keep the current at 1A in each coil in all sequences when running in HALF STEP mode?

Are there any mistakes in my scheme ??


thank you.

[AlainB]

The motor will not run in the 1 2 3 4 sequence but more in the 1 3 2 4 sequence.

1 & 2, and 3 & 4 will never be energized at the same time.

http://www.usna.edu/EE/ee461/Homewor...AllPhases1.gif

Your schematic is Ok if you want to run the stepper in half or full step mode (even wave mode) using some ballast resistors.

[wini]

OOH yes your link is very evident, i must be careful in chose the arrange of coils. i am sorry for late and thank you for your replay.