[Controlling a DC Fan with a Photohelic]

How exactly are you going to step the voltage and what are the steps? Have you determined in what voltage range the fan is effective (if you spin it too slowly, it will do nothing).

What you probably need to do is create a crude PWM (pulse width modulation) setup. The M90 does not have this function like the Vision series does, but you could make one. If you don't know what PWM is then do a little research on the Internet. It will give you some insight as to what your program needs to do.

Joe T.

My original thought was to have the PLC start up with a set voltage (let's say 7 volts) and delay 15 seconds to give the fan time to get up to speed and establish some pressure in my chamber. My photohelic will then switch based on it being too low or too high. I would use this switch to tell my program to now add or subtract 1 volt to my current output voltage. Once the fan is between the set point both switches will be open and nothing changes until my pressure drops or gains. I was hoping this could be done with a simple program. Maybe I am wrong.

[Controlling a DC Fan with a Photohelic]

I have a Dwyer Series 3000 Photohelic and would like to control a 24volt fan. I am thinking I can use the high level and low level switches to control my voltage. I need a program that will slowly step up the current voltage if the low level is hit and slowly step down the current voltage if the high level is hit. I am extremely new to PLC programming and I have looked through the sample programs and still have no clue. :-) I have an M90-TA2-CAN controller. Any hits or ideas?