Hi everyone i would really apreciate some help with this circuit the problem i am having is that i carn't get the voltage i need from pin three on the 555 it will only go down to 0.52v when the pot is at min if i change the resistors then it goes to high at the other end over 1.24v has anyone any ideas on how to do this the scematic i have attached is the circuit i am using .

 

Why would you have the wiper of the pot connected to the out-put? That's where the 0.52V is coming from. Rewire the pot correctly.

 

D'oh! I didn't see that.

 

Try this:

 

Hi Shortbus and thanks for taking the time to look at my scematic i have the pot connected like this to vary the out put with the pot, the circuit works in part the only problem i am having is that it won't go down beond 0.52 and what i want it to do is go to 0.3v and up to 1.25v by varying the pot

 

That won't happen. You will need a second pot on the out put. The pot you have is just for the timing of the 555.

 

What are you using/needing the variable voltage for?
Normally to provide a variable DC voltage using PWM you have a low-pass filter at the output.
As-is the measurement will depend a bit on the meter you are using.

 

can you please explain how to inclued the second pot to achive what i require

 

Hi tubeguy i need the variable voltage to apply to a led driver control pin for dimming

 

Besides the voltage, what is the current requirement or input resistance of the control pin.
You might need a simpler circuit maybe even just a pot or a pot with a voltage follower - emitter follower transistor.