555 ic timer

how can i maximize the amount of duty cycle from 50% up to 95%? what component should i vary in order for me to get that value, e.g. 95% duty cycle?

Posted by ledor07 on 27/09/2003, at 14:01 GMT

555 astable duty cycle

The duty cycle is determined by R1 and R2.

The duty cycle = Tmark / Tmark + Tspace
so Duty cycle = (R1+R2)/(R1+2R2)

This gives the duty cycle as a simple number, multiply by 100% to convert it to a percentage which is how duty cycle is often quoted.

You need 95% = 0.95, so with a bit of algebra:

R1 = 18 x R2, for example choose R1 = 10k, R2 = 180k.

Posted by John Hewes on 29/09/2003, at 14:16 GMT

Correction!

Sorry for the silly mistake in the previous reply, the last line should read:

R1 = 18 x R2, for example choose R1 = 180k and R2 = 10k.

[Why are errors like this always more obvious AFTER pressing Post message?!]

Posted by John Hewes on 29/09/2003, at 14:22 GMT

Thank you!

thank you for the reply regarding my question. i appreciate it much! thanks!

Posted by ledor07 on 08/10/2003, at 15:27 GMT