Tkinter/Wiring Pi PWM

[muhteeus]

I have written a python script to control a 12VDC fan through wiringpi and hardware PWM. The PWM uses a MOSFET buffer. There is a slider that adjusts the fan speed between 0-1023 for a range of 1024.

The script works flawlessly, but when I am above roughly 40% of full speed, the fans will speed up (audibly) to 90ish%. If I move the slider down, the fans stay at the same speed. However if I adjust to full, speed and then back down... the fans will slow. If I stay under 40% speed.... this does not happen. Also, moving the slider slowly between 0-1023 produces good results and accurate control.

Am I missing anything obvious? How can I find out what is changing my value?

Code: Select all

from Tkinter import *       
import wiringpi2 as wiringpi
import opc, time

# Set up wiringpi
wiringpi.wiringPiSetupGpio()
wiringpi.pinMode(18,2)
wiringpi.pwmSetClock(6)
wiringpi.pwmSetRange(1024)

    def __init__(self, master):
        frame = Frame(master)
        frame.pack()
        Label(frame, text='Fan').grid(row=0, column=1)
        scaleFan = Scale(frame, from_=307, to=1023,
              orient=HORIZONTAL, command=self.updateFan,
              length=400, width=50)
        scaleFan.grid(row=1, column=1)

    def updateFan(self, duty):
        wiringpi.pwmWrite(18, int(duty))

root = Tk()
root.wm_title('Drank Fan Control')
app = App(root)
root.geometry("800x480+0+0")
root.mainloop()

[davef21370]

I'd start by printing the value of duty in the updateFan function, then at least you'll know if you're getting the correct info from the slider.

Dave.

[muhteeus]

Let me try that.