Relation between STEP Input Frequency and Current Chopping in various modes of Stepper Motor Operation

siva2 · ‎2015-07-23

Posted on July 23, 2015 at 13:32

I am a newbie to Stepper Motors. I am working on L9942. The different modes that it can chop the current are Full mode, 1/2, 1/4 and 1/8. When 1/4, 1/8 modes are used with lower STEP Frequency or when Full and 1/2 modes are used with Higher STEP Frequency , there is no current chopping at the output for coils. What is the reason behind it?

My aplication is to control position of the Stepper Motor with a stipulated time. The time is large and the steps to be taken is less in requirement. So I need to drive at very low frequency which I am not able to.

Also is there any other way to control using the same L9942?

Please help me out.

#step-input-frequency #l9942

Nickname5642_O · ‎2015-07-30

Posted on July 30, 2015 at 17:04

Hello Siva,

you have to check two things :

- DAC SCALE in SPI Register 1 (for reference see also Table 12 and Figure 7 on the Datasheet) the value you choose depends on the motor.

- Current profile in the SPI Register from 2 to 6. As it depends on the choosed step mode, for reference see Figure 3 on the Datasheet in order to understand which currrent profile have to be setted .

siva2 · ‎2015-09-01

Posted on September 01, 2015 at 12:14

Hello Guida,

Finally solved the problem a week ago.

My direction input to the register was updating the phase counter value to 0 in every program loop. The problem was solved when the update function was made out of the loop on direction change request basis.