PDA

View Full Version : 555 Timer Configuration?



manumenzella
- 24th November 2007, 14:28
Hi. i am trying to configure a 555 timer to output a 20khz cycle with a 1% duty. I am having trouble because I cant get it to output a lower than 50 % duty cycle with that frequency!
Can you help me calculate the values of r1, r2, and c1?
Thanks a lot.
Manuel

mat janssen
- 24th November 2007, 15:23
When you aks Google to show you some application notes of the NE555 then you will get something to see how it's done.
By using a diode (or 2) you will get the whole range from 1% till 99%.

mister_e
- 24th November 2007, 17:44
look at page 7
http://www.edn.com/contents/images/82202di.pdf

Darrel Taylor
- 24th November 2007, 20:46
Simple,

Dump the 555.

Get a 12F683.

Then use ...
HPWM 1,2,20000
No external parts. No difficult calculations.

If desired, add a serial port to set the output with your computer, save the values in EEPROM, then disconnect the computer.

Can't do that with a 555.
<br>

tenaja
- 24th November 2007, 21:13
Hi. i am trying to configure a 555 timer to output a 20khz cycle with a 1% duty. I am having trouble because I cant get it to output a lower than 50 % duty cycle with that frequency!
Can you help me calculate the values of r1, r2, and c1?
Thanks a lot.
Manuel
google 555 timer calc and you'll get lots of calculators that will do it for you.

mister_e
- 24th November 2007, 21:38
yes, as long as they match the extra Diode(s) circuit.

PIC10F???