AB1500 PWM or PTO

Hello All,

I'm new here so pls bear with me.

I have an AB1500 PLC and I am trying to use the PWM or PTO function to control the speed of a small 12V dc motor. I have the Instruction set manual, but cannot get the hand of how to program these functions effectively.

I would appreciate any help, ideally a ladder program using any or both of these instructions so that I can use them to learn how to program these functions.

Tks in advance!

What means "small motor"?
Will you use any kind of motor drive, or you want to connect the motor directly to the PLC output? The latter is not a good idea.
PTO generates specified number of pulses with specified frequency, and cannot be used for your purposes.
You must go PWM. Before programming the PWM pulsetrain, ensure that with the output activated, the motor rotates at full speed.
Be aware, that voltage applied to DC motor does not strictly define its speed, as it is load-dependent.
Reversing the motor is an additional challenge, but you never mentioned it.

try this

@ Segei: The small motor is a 1V, 1Amp motor (as used in small kits). I am using it for demo purposes to students. Yes, ideally i use PWM but can manage to simulate PWM using PTO by varying frequency and pulse train width. The plc output will drive a high freq FET to operate the motor so it will be connected directly. Motor is alfready run in this way on the kit in 12V dc mode.Load is minimal.

@ widelto: Many thanks. Had a look at at right now, will use the principle to operate the motor. much appreciated. i will post the results here later

@ widelto: Many thanks. Had a look at at right now, will use the principle to operate the motor. much appreciated. i will post the results here later

granc64 said:

@ Segei: The small motor is a 1V, 1Amp motor (as used in small kits). I am using it for demo purposes to students. Yes, ideally i use PWM but can manage to simulate PWM using PTO by varying frequency and pulse train width. The plc output will drive a high freq FET to operate the motor so it will be connected directly. Motor is alfready run in this way on the kit in 12V dc mode.Load is minimal.

Click to expand...

Well, if there is a FET between PLC output and the motor, it is not connected directly.
Use PWM. It is impossible to emulate PWM with PTO without extra hardware, and there is no such need when you already have PWM function available.

To use the PWM, assign the output and the PWM frequency in PWM function file. This has to be done offline and downloaded to the PLC.
Then just run the PWM in the program and control its duty in 0.1% units.

I see. Tks for the info Sergei. At least now I have something to refer to. I will try it out and let you know the outcome.

Yes, you are right that using PWM is better. At least from the theory and manuals I read it should be neater and smoother.

Pls do not hesitate to post any other examples that you might come across. They give me a valuable insight on how to use the function, which unfortunately are not so clear in the manuals.

Thanks again!

Sergei Troizky said:

Well, if there is a FET between PLC output and the motor, it is not connected directly.
Use PWM. It is impossible to emulate PWM with PTO without extra hardware, and there is no such need when you already have PWM function available.

To use the PWM, assign the output and the PWM frequency in PWM function file. This has to be done offline and downloaded to the PLC.
Then just run the PWM in the program and control its duty in 0.1% units.

Click to expand...

Hello again Sergei. Many thanks for the attached pics. I tested them out and the motor worked as intended. I will do some variants to test out, but your help has been fundamental.

Cheers!