I'm having trouble getting the 555 circuit to work. I only get from about 50% to about 60% duty cycle. The only pot I have is a 500k ohm. Any ideas?

 

I got a bit more by reducing r1 to 100 ohms, but it heats up and reducing it more gives me nothing.

 

OK I used this circuit and got almost the full range between on and off. I can't get it below ~3% duty cycle. Any ideas? I need the motor fully off at idle to avoid draining the batteries.

 

Not real sure, but don't think it is possible with just the 555 alone. You need to add another IC, a LM393 to get to that point. One of our mods here has a good circuit that will do it, here's the link - http://forum.allaboutcircuits.com/showpost.php?p=117641&postcount=6 Figure #5.3

 

At what frequency is your 555 running?

Edit:
You can get the 555 circuit in post #43 to stop oscillating at one or other limit position of the pot wiper by connecting one end of the 500k pot (pin 1 or 3) via a 1meg resistor to either ground or V+ as appropriate. That should give you the control you're after.

 

OK, I'll give it a shot. How about driving the 555 with a microcontroller? I'm in the mood to program today.

 

At what frequency is your 555 running?

Edit:
You can get the 555 circuit in post #43 to stop oscillating at one or other limit position of the pot wiper by connecting one end of the 500k pot (pin 1 or 3) via a 1meg resistor to either ground or V+ as appropriate. That should give you the control you're after.

Forgot to ask, if I change the pot to a 5k one (the scooter throttle) will this resistor need to be different?

 

I ended up hooking the 555 to a microcontroller and am beginning the code now.