555 timer help

[stuee]

i have attached a what i think is a 120off / 1 sec on
Can someone check it over and tell me if its ok.
Also is it possible to make it 10 mins off 2sec on, and i need to put a reed switch on it somewhere to turn it on when switches are on.
Also with the 120off/1on will it reset back to 120 after the on state.
Thanks

View attachment 36096

 

[ante1]

Sorry but 24Volts will kill the 555 I one second!

 

[stuee]

my mistake, ment to be 12v

 

[audioguru2]

Where is the timing capacitor for the 555? You are using a piece of wire instead.

 

[surajbarkale]

You can not get delay in terms of 10mins from a 555. Well not without very large capacitor & similar tolerance. Better use a dedicated timer IC for long delays

 

[audioguru2]

Hi Suraj,
The 555 is a dedicated timer IC. The problem that it has with long time periods is that the timing capacitor must have a high accurate value. Electrolytic caps are not accurate and they have a fairly high leakage current.
If you are rich and have lotsa space, you could use 100 or more 1uF 5% tolerance caps in parallel!

For years I have been using the CD4060 oscillator/counter IC for long time delays, using a cheap low-value accurate timing cap. I have recently discovered the CD4541 that is much better than the CD4060 because it has a longer divider, built-in powerup reset and a choice of output polarity. It is smaller too (14 pins),
http://www.microcontrolador.com.br/datasheets/CD4541.pdf

 

[audioguru2]

Hi Stuee,
Never mind the Instant Messaging, let's let everyone see how easy it is to make a long duration timer with the CD4541.
Here is a 5 minute timer where the output goes low after the time period (it can be made to go high if you want). Change the cap for a different time period. Add an RC network and a Schmitt trigger, or another timer to get a 2 second pulse. I got this one from the 1st page of about 77 pages about it on a google search:

View attachment 36107

 

[surajbarkale]

i meant to say "dedicated digital timer" time for mental checkup ;D