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12hour timer using two 555 timers.

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dottedquad

New Member
Hello all, I'm currently working on a project that utilizes two 555 timers. The first 555 timer controls the 12 hour(I'm assuming the delay) once the 12hour has been met, trigger the second 555 timer to turn on a relay for approximately 2-3 seconds. Once the 2-3 second is met trigger the first 555 timer. That sounds simple so far except when I run into the RC circuit. I'm not sure what resister and capacitor to use for the 12hour.

I realize I can use a kitchen timer to set the on and off times and hook that up to the 2-3 second 555 timer. I'd rather not use this approach.

-Thanks,
rich
 

creakndale

New Member
You might try to locate these Exar Long Range Timer IC's on eBay for your 12 hour delay:
XR-2240
XR-2242

creakndale
 

davidbear

New Member
Are you fundamentally opposed to using another chip other than the 555? I'm no expert, but I would think that you could set the first 555 to run as a multivibrator at say 0.1Hz, feed that signal into a 14-bit binary counter, and have it set off your second 555 to release a 2-3 second burst and reset the 14-bit counter.
 
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KMoffett

Well-Known Member
Maybe something like this?

**broken link removed**


Ken
 
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dottedquad

New Member
Are you fundamentally opposed to using another chip other than the 555? I'm no expert, but I would think that you could set the first 555 to run as a multivibrator at say 0.1Hz, feed that signal into a 14-bit binary counter, and have it set off your second 555 to release a 2-3 second burst and reset the 14-bit counter.

I'm a beginner at electronics. I'm afraid that's way over my head. I'm not quite sure how that would work. Also, I'm not opposed to using another chip other than the 555. I was checking out the CMOS 4060.

-rich
 

blueroomelectronics

Well-Known Member
The 4060 will require lots of dividers to get 12Hrs. Is it going to be connected to AC (Mains)? If so you could drive the counter with a 50/60Hz signal.
 

Hero999

Banned

notauser

New Member
Another option would be to see if you can find a dollar store digital clock or something you can rip apart and tap into..
 

Arkham00

Member
Why do not use a single PIC12F 8-pin device with internal clock?
With a very simple program you can have precision delays with almost no external components.
 

dottedquad

New Member
Why do not use a single PIC12F 8-pin device with internal clock?
With a very simple program you can have precision delays with almost no external components.

Occasionally I would play with the parallax basic stamp as I'm a programmer and thought by using the basic stamp I could learn electronics. I was wrong. Although it does teach me the fundamentals of resisters and dc motors It doesn't necessarily teach me the very basics of electronics. I thought about using the basic stamp for this project but felt it wasn't necessary, hoping I could build this using basic electronic components.

-rich
 
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MrDEB

Well-Known Member
ultra long times w/ 555

there is a way to get ultra long times using a 555 and several 4017's
12 hours = 720 miniutes so tap off the 4017 for 720 miniutes depending on pulse rate of 555.
for long times use a large capacitor and smaller resistors or so I am told.
yes its the long way around it but one doesn't need to program a pic.
 

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davidbear

New Member
Hero,

In the circuit you posted, why is Q4 connected via a 4K7 resistor and a diode to "-ve"? I don't get it.

davidbear
 

Hero999

Banned
It's an LED but with a 4k7 resistor it'll be very dim.
 
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