I have been playing around with a simple PWM circuit using a 555. In stead of using a 100K pot to vary the duty cycle, I want to control with a sp on-off-on rocker switch.

I have looked at several digital pots, but I was not sure how to really use one and I have not found any in a DIP type package.

Any suggestions would be appreciated.

 

There are other ways. Something like a class D will convert a DC voltage to a PWM, the DC voltage can be created using a DAC, a simple one at that. Figure qty 3 op amps and a 555.

 

The DS1869 from Dallas is available in a DIP package. That may be more complicated than you want.

National Semiconductor datasheet for the LM317 shows another way to do it:

Finally, you could replace the switching transistors in the above circuit with SPST switches to give a few selected PWMs.

John