Circuit design needed

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I need to build an inexpensive circuit to open and close a 3volt DC power source at about 15 minute intervals.
The circuit would need to open, then close again after a short delay say 500 milliseconds to a few seconds.

I had thought about doing this mechanically with a slow rpm motor, gears and a micro switch, but there must be a circuit that can do this.


Re: Circuit design needed says...
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Normally I would suggest a 555 timer if you want to build  
something, however, you equire a rather longer time than
what a 555 is suited for.

  Look up a CD4060B or BC circuit example for a long timer.

 Fairchild has a clean looking PDF file on this.

 This chip comes with its own oscillator that you can  
 configure and it has multiple frequency dividers that
allows you to select a range of times
 This may help you better understand..


Re: Circuit design needed
On 04/07/15 01:57, M Philbrook wrote:
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I agree. In the 80s I made my mum a kitchen timer - 3 cascaded 4017  
decade counters (with the middle one wired to reset on the "6" for 10's  
of minutes. IIRC there was also a divider between the 555 and the first  
(minute) 4017.

It was very stable and repeatable once calibrated. The OP's 15 minute  
period will be no problem.

Re: Circuit design needed
On Fri, 3 Jul 2015 16:58:14 -0700 (PDT), Mark

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1. Must the 3 volt power source be used to run the timer or is there
   another supply available for that?

2. How much current must the 3V power source deliver into the load?

John Fields

Re: Circuit design needed
1.I had planned to provide a dedicated battery power source.

2. the 3v is 2 D batteries powering an igniter and regulator for a propane  
water heater. I bought this heater to circulate water in a relatively small
 swimming pool, but the heater shuts of at regular intervals in which seems
 to be a built-in unit of time. Turning off the power off then on again res
tarts the gas regulator immediately.

Re: Circuit design needed
On Sat, 4 Jul 2015 02:58:24 -0700 (PDT), Mark

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Sorry, but I'm going to bow out of this one.  Just _thinking_ about
overriding auto-shutoff safety circuitry makes me nervous...

John Fields

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