I would like to build a circiut, that would eg. put out a signal (turn on a device) with a 24 hour delay, and repeat it every 24 hour. (from when it was powered on)

Is this something the 555 IC will be able of? if yes, have any suggestions for a circuit?
If no - how could it be done?

Thanks

 

How accurate does this timing need to be? I think 24 hours is very close to, or beyond the limit of that a 555 timer will allow (due to capacitor leakage and tolerances and things like that).

You could make a simple PIC circuit with a very slow oscillator and store the counts in a massive register to count to 24 hours. THat would be very, very accurate. At 26MHz frequency, a 39-bit counter is enough to track 24 hours. You'd basically have to link together a giant series of integer variables together in memory since 8-bit MCUs don't have large enough counter registers that periodically get updated by a timer (a dsPIC timer counter can do this though if you use the 32-bit timer and a 256:1 prescaler, it can actually go up to 48 hours like this on a clock of 6.5MHZ x4 PLL).

Do you need the signal to go HI for 24 hours and then go LO for 24 hours? Or to pulse HI momentarily and then go LO, and then do so again 24 hours later?

You could also hack an alarm clock or stopwatch or something.

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If I were doing it I'd use a small PIC like the 12F629.
32,768Hz watch crystal on TMR1 (low power and wake up from sleep every 8 sec to update the time), latching relay (zero power once latched) and a battery. Should run for ages.
If you've got AC available then just tap into the 50/60 Hz signal for the timebase, use a PWM channel for the relay (assuming it's not latching) and there you go.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

I think Harris had a better timer chip back in the day (do not recall but maybe google for it). The lm555 I would not count on for a long delay.

If you go with a PIC or AVR you will need to get a programmer, write a program, etc.

 

Either I'm not fathoming the original description or ....

What's the matter with a simple $9.95 plug-in, synchronous-clock-driven timer?

Dean

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Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

 

Actually very accurate.


It should go "lo" for 24 hours, then give a signal (hi) on a variable time (eg. 30sec) and then go "lo" again.

 

It's not half as fun.. And then it should be build in to a cabinet.

 

Yeah, go for a PIC. Use a 32.768 quartz oscillator as the clock (probably the slowest oscillator you can get and definately the most accurate as that frequency and kind are used in RTCs). You'll probably need to use the secondary oscillator pins on the PIC rather than the regular (higher speed) oscillator pins. You don't need that fast oscillator anyways.

And then yeah, really easy code after that. Set up the clock and a timer interrupt.

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hi TCDK,
Use a PIC, timer1, an opto detector for the mains half cycle [50 or 60Hz], using the low side of the mains transformer to drive the opto-detector in order to give the mains frequency output pulse to drive the PIC timer input.

Also look at the HEF4060 i/c

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

I will start buying this PIC programmer:
http://www.talkingelectronics.com/pr...-01-Intro.html


This is my very first PIC project - wonder if any of you knows a site or something, where I can see other 12F629 projects.

 

If this is a one time thing you could use a PICAXE and safe yourself the cost of development tools.

http://www.rev-ed.co.uk/picaxe/

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Loads of 'em

Here's a link that links other µ controllers.
http://www.tinaja.com/pic500.html

 

Hmm most of the links at that page, dosen't work.

 

Found this one.

Looks simple for me.

Instead of the relay, I will put in a 555 timer, that will allow me to adjust the "HI" time.

 

link would do it much easyer ´

http://uk.geocities.com/ronj_1217/c4060.html