Timing Circuit

[KurtS]

I've been racking my brains on this one. I've looked at many timing calculators but they all seem to work in shorter intervals then what I need.

I need the values for the caps and resistors for a circuit using a 555 timer. I need a half second pulse every 25 seconds.

Thanks in advance to anyone who can help with this.

 

[audioguru]

Maybe you can use a CD4060 oscillator/digital divider.

 

[mneary]

Begin with a fairly large capacitor, like maybe 100uF. RC is about 1/2 second with 100uF and about 5k ohms. RC is about 25 seconds with 100uF and 250k ohms.

Check the 555 data sheet for the exact formulas.

 

[mbarazeen]

make squire wave of 1/2 sec. divide it by 50 using 4060 as audioguru told, every reset will give you 25 sec delay and you can get 1/2 sec by another out put.