I've created/adapted this for those who need a timer that can be programmed to cycle at periods other than 24 hrs.. Good for things like fans/pumps/heaters/lights..
This version has no second resolution.. Its extremely easy to whip up a short period timer as opposed to something that can handle hours/days, but this circuit could be adapted for a high precision short period timer (By adjusting the counter(s) in ICs 1/2) that isn't susceptable to heat fluctuations like 555/RC timers since it uses a crystal oscillator..
Most specialty timers are very expensive for no good reason.. Parts for this should run $10-20 I imagine.. Eventually I'll build a parts list, but its pretty obvious expept for exact numbers of trivial components..

Circuit Operation:
Its actually a really simple circuit for its size.. Each area of the schematic does a stage..
ICs 1&2 and the components near them create the one minute clock, IC's 4&5 count these minutes and each trigger the relay once per day cycle.. (IC4 turns on the relay, IC5 turns it off).. ICs 6&7 just control when the relay gets triggered by counting up to their set delays, then resetting the counters in ICs 4&5 respectively (on the first cycle only).. Basically when the relay is supposed to come one, IC4 gets reset to 0.. It then counts as many minutes as are in a day cycle and then turns it on again.. Same thing with the off switch, IC7 waits until the relay is supposed to go off, then resets IC5 so that its sync'd to keep turning off at the same time each day.. In the original circuit, ICs 6&7 did not exist.. It was set up with normally closed push switches that manually got pressed the first day at the proper on/off times, then IC's 4&5 just repeated that process every day cycle.. (Again a day cycle is as many minutes as ICs 4&5 are set to count before resetting)..
The 9V battery is just there so the counters don't lose their counts if the power goes out..
7 segment display(s) for time readout could easily be added, but I don't want to clutter up the schematic before ppl get a chance to discuss the guts of the logic..

Its critical that the load is solidly connected to the relay with suitably guaged wire!

I haven't built/tested this, but its based off a proven circuit.. Still though it would be better to proof/discuss it before declaring it finalized..

Attached Images

timer_adapted4.jpg (59.3 KB, 119 views)

I redrew the schematic.. Curved lines don't connect obviously.. It doesn't necessarily need to be this complicated (not to mention that its not nearly as bad as all those tracks make it look).. Each of those diode/switch banks could be reduced specifically/permanently to the time settings you require.. As its drawn, any number of minutes (0-4096) days/on-off periods are settable with those jumper switches under the diodes.. Any output bits you don't need to make up your binary minutes can be left absent if you don't care about reprogrammability..
I guess I still need to do up a parts list..
Also, as yet another option I'm going to look into adapting a cheap, easy to find digital clock/timer to eliminate as much track laying as possible.. Most digital clocks work on the same counting principle as mine, so it shouldn't be tough to find something that can easily be tapped into the circuit, and eliminate the need for most of the chips in this design..

Attached Images

Timer5.jpg (88.2 KB, 55 views)

I'm not even gonna try that. I'd rather pay 20$ for a time than save 15$ and try that...

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Actually for a 24hr timer I agree totally, but more programmable timers that can be made to function on non-24hr periods are usually ALOT more expensive.. It was the $300 price tag I saw recently that compelled me to do this..
And I don't know how to explain how much simpler this is than it looks.. Somebody comfortable with a soldering iron could put this together in 30 minutes..

love the schematic, now i have a circuit to build on my time off, i should have most of those parts too. =)
kudos
thanks overpriced university!...not

Cool, sounds like you know what you're doing.. If you have much experience with cmos do you see any issues? I completed the labelling, and made up a component list.. Ready to transfer it to an etching layout I suppose..

Attached Images

Timer6.jpg (77.6 KB, 30 views)

Put this on eBay!

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If I was gonna do that, I'd improve it.. Most ppl are used to readouts and decimal.. The binary jumpering won't sell I doubt..