Pwm On Fx1n

[Guest Scott]

This is the first time I've tried using this function, and so far it's giving me grief. The pulse width part is great, but the pulse rate is way too slow. I need at least 2Khz for my drive to be happy and so far the fastest I can get is 1Khz with S2 set to K1. Is there a way to speed this up?

[Guest Guest]

Scott, As the minium time base is 1mSec, your stuck with 1K max. I'm not aware of any method of increasing this. Have you looked at the PLSY (FNC 57) instruction as an alternative as the frequency rate would more suit your requirement. Regards, Gene

[Guest Scott]

Rats I was playing with the PLSR at first as the drive has a position control input, but I never got it working right. The problem is that I don't really want position control, I need velocity control. This is going to run a brushless motor in one direction with an adjustable target RPM and ramp time with little or no hold time. It just ramps up then ramps back down within a specific time. I may have to look into a DAC addon... Thanks

[Guest Gene]

Scott, One alternative is using Fx-1PG / Fx2N-1PG, these I've used in conjunction with a servo controller and servo motor. As they were also Mitsubishi it was quite a straight forward task, in that the PLC used To and From instructions to control all the parameters. I'm not sure how you would look to interface your motor, what is the application and how accurate a loop are you after. Have a look at the spec sheet or download the manual from:- http://www.industrial.meuk.co.uk/html/home.asp The Manual is JY992D65301 Regards, Gene

[Sergei Troizky 26]

Still unclear why do you need so high frequency for PWM. The idea of PWM is its averaging in the destination device, typically into voltage, which works OK at tens of Hz. On the other hand, in FX-series too short period setting decreases the PWM resolution. For instance, with 4ms PWM period, the PWM duty may be only 0, 25%, 50%, 75%, 100%, that is only 4 increments. At full possible 1kHz, the only possible PWM duties are 0 or 100%. Edited 19 May 2010 by Sergei Troizky