[ph2t]

ahhhh ejaf, I used to have that book! Also the one for TTL logic circuits. They were great books.

What you're doing is exactly what I set out to do initially. After experimenting for a while I found that I could never achieve a duty cycle greater than %50.

No matter what value combination you use for R1 / R2, when the pot is turned to zero ohms you'll get %50 duty. As the pot resistance increases (10K, 100K, 1M, etc...) the duty approaches zero.

The duty cycle equation is as follows..

R2
D = -------------
R1 + 2*R2

when the pot is a max resistance (eg, R1=10K)

1
D = ------------ (assuming R1 value of 1K)
10 + 2

D = 0.0833 = 8.33% (pretty much zero)

when the pot is at zero resistance (eg, R1=0)

1
D = -----------
0 + 2

D= 0.5 = %50 duty.


Bugger!