1593Views4Replies

Author Options:

How to set up a repeating 5 minute off 10 second on circuit? Answered

The title just about says it all.  I'm wondering how to do this with a 555 timer.  Thanks in advance!

6 Replies

user
iceng (author)2011-06-22

These are values calculated by a program, but even a CMOS 555 probably cannot give you 5min because a 100uF capacitor leaks faster then a 4.2M
resistor can charge.

I'm pretty sure you will need more ICs ( counters or a uP )
to do a 300 sec to 10 sec timer.        A

Select as Best AnswerUndo Best Answer

user
iceng (author)iceng2011-06-22

The calculator accepted 4200K = R1, 150K = R2, 100uF = C
and resulted with a value for T1 = 301 sec and T2 = 10.4 sec

A

Select as Best AnswerUndo Best Answer

user
LamN20 (author)iceng2016-04-20

Actually, R1 is about 2200k, t1 is about 270 seconds.

Select as Best AnswerUndo Best Answer

user
iceng (author)LamN202016-04-20

Could be a different calculator or 555.

Anyway 5 min x 60 sec/min => 300 seconds

BTW 270 sec is 4 1/2 minutes

Select as Best AnswerUndo Best Answer

user
andy70707 (author)2011-06-22

This. I have seen circuits for accurate 10-minute timers using 555s, but they use a lot of external components, and I don't think you can really adjust the mark/space ratio as much as that. You can get a 556 (or 7556 for the CMOS version) timer which is two 555s in a 14-pin dil package.

Select as Best AnswerUndo Best Answer