Ken

Thanks for response. The fan is a 12v fan with a dedicated powersupply. I used a voltage of 5v peak to peak to get the fan to work. I will try your circuit tomorrow. Thanks for your help. Ken

Thanks for the response. I am hooking up to a High staic pressure fan for a heatsink dissipating 3000 watts. The PWM controls the fan speed. The lead for the Fan speed input is referenced to the ground of the fan. By connecting to ground the fan is off. When you connect the speed control line to a signal generator ( + of signal generator to speed control, - of sig generator to ground) The speed is controlled perfectly at 20khz with speed changing linear with duty cycle. When the fan speed signal is open the fan is at full rpm. Ive tried connecting directly to the input with no results. I then tried connecting through a highspeedfet using the output of the HSO to control the base. I had no luck with this either. I then tried hooking up the HSO to an oscilliscope, The output gave alot of noise when it was enabled. The speed input of the fan is a high impedance input.

Can I also get a diagram of the proper way of hooking up to the output of the PWM. . I am not getting it to output correctly.

Hi , Thanks for the response. I am measuring the frequency with an osciliscope. The square wave comes up just not at the frequency specified. When i try and enter 50000 for frequency it will not let me enter that value. The max it will let me enter is 4 digits not 5. The duty cycle works correctly.

Hi, I am in the process of setting up a plc to output a 20khz with a duty cycle of 20%. I set up the ladder and setup the hardware for pwm. The duty cycle was setup as a MI and I set it to 200 for 20 Percent. My problem is figuring out the proper way to set up the frequency? I tried different MI for the frequency but cant get the signal to output at 20000hz. I am able to turn the pwm on and off but having difficulty acheiving higher frequencys. I have V570 with V200-18-E3xb snap in I/O. I set up the dip switches for NPN. Can I get a diagram or just the proper steps for setting this up. Ive checked the manual and the help topics but none of them show clearly how to set this up. I am new to this software, but fluent in ladderlogic. Thanks, Ken