# Setting 555 timer to MAX.

1. Jun 25, 2008

### Beckman44

How would i do this?

2. Jun 25, 2008

### chroot

Staff Emeritus
What does this even mean?

- Warren

3. Jun 25, 2008

### Beckman44

sorry if this was not understandable....here i go again...

how would i program a 555 timer so when i activate it it tells something else that it is doing a certain action many times.

Ex. Holding down a button and Xbox Controller shooting as fast as possible

4. Jun 25, 2008

### Beckman44

a better question would be how do you adjust the rate of a 555 timers pulses?

5. Jun 25, 2008

### chroot

Staff Emeritus
You should consider reading the 555's datasheet.

- Warren

6. Jun 25, 2008

### Beckman44

where could i find this?

7. Jun 25, 2008

### chroot

Staff Emeritus
8. Jun 25, 2008

### Beckman44

what will the data sheet do for me?

9. Jun 25, 2008

### chroot

Staff Emeritus
It'll teach you how to configure the circuit to produce any kind of pulses you want. Look in the Applications section.

- Warren

10. Jun 25, 2008

### Beckman44

11. Jun 25, 2008

### chroot

Staff Emeritus
You've got to be kidding me. I gave you a link to a Google search of the words "555 datasheet." The very first link points you to a datasheet:

http://www.national.com/ds.cgi/LM/LM555.pdf [Broken]

- Warren

Last edited by a moderator: May 3, 2017
12. Jun 25, 2008

### Beckman44

i cant just use a pot?

13. Jun 25, 2008

### chroot

Staff Emeritus
Beckman44, you really need to spend at least a bit of time doing your own reading. The datasheet will tell you everything you need to know to calculate R and C values to get whatever frequency and duty cycle you'd like. The datasheet is the ultimate document from which to learn how to use an electronic device. If you can't understand the datasheet, or if you try to use what you've learned and still can't get it to work as you'd like, then come ask questions. Spend an hour, read the datasheet's Applications section a few times over, and then come back if you still need help.

- Warren

14. Jun 25, 2008

### Beckman44

i dont know if im misunderstanding or u.....but is lm555(used int he guide) the same as cmos 555 timer? i mean do they change the same?....and i see nothing in there telling how to actually change the chip itself....it says how to get a rate but now how YOU change the chip...What materials you neeed.

15. Jun 25, 2008

### chroot

Staff Emeritus
Beckman44,

Every "555" timer, from every manufacturer, is going to operate the same way. They're known as "second source" parts, and are functionally identical.

I don't know what you mean by "changing the chip." To configure a 555 timer, you connect some capacitors and resistors to it. The values of these components determines the frequency of the oscillation, etc.

You need to ask more detailed questions if you want more detailed answers.

- Warren

16. Jun 26, 2008

### the one

Hi Everyone ,
Beckman44 , I Understand That you need to produce pulses as fast as possible , So you need to use an astable circuit like the one in the attachments .
There are Some Equations Control The Properties of the pulses and they are :
( The frequency Equation )

$$$f = \frac{{1.44}}{{C(R_1 + 2R_2 )}}$$$

( The Period Equation )

$$$\tau = \frac{1}{f} = \frac{{C(R_1 + 2R_2 )}}{{1.44}}$$$

( The Duty Cycle Equation )

$$$Duty{\rm }Cycle = \frac{{R_1 + R_2 }}{{R_1 + 2R_2 }}$$$

You See That the Resistors and the Capacitor Control The Time Properties of the pulses , So by the good Choise of them you can get any pulses you want .

#### Attached Files:

• ###### 555Timer.GIF
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17. Jun 26, 2008

### Redbelly98

Staff Emeritus
I agree with chroot that it's good to become familiar with looking at datasheets. In the National datasheet, what you want starts on p. 7 under "ASTABLE OPERATION":

http://www.national.com/ds/LM/LM555.pdf [Broken]

Figs. 4 and 6 are particularly relevant, as is the equation for "f=..." on p. 8.

Last edited by a moderator: May 3, 2017
18. Jun 27, 2008

### fedaykin

Just an FYI, many 555s don't work so well starting at around 500kHz.