adjustable l-10 minute timer on an hourly basis

[spindown]

I need a timer that will go on hourly with an adjustable time on
interval from one to ten minutes. Local hardware store timers will go
on hourly but fifteen minutes is the shortest interval. I'm looking for a circuit that will close
a relay to power a small 120 volt water purmp. Any ideas? Thanks Paul

[Robert Reed]

The first thing that comes to mind are cascaded 555's or 14 bit dividers. How accurate does it have to be? Is it a repetitive or single shot operation. What kind of resolution do you want?Above all, is this something you want to build yourself?

[fripster]

hi,

Just follow the KISS principle:
- Buy a simple timer with 15min intervals as mentioned
- Buy a second timer module for 120V that is settable in minutes (standard switchgear stuff)
- Feed second timer module each hour for 15 minutes with first timer
- Second timer will steer the pump
- Ready.
- No sweat

fripster

[haklesup]

Have you tried a water sprinkler timer. I'm not too sure they can come on hourly though but they can be programmed in minutes from 1 to 15 no problem. You would just need to isolate the 120V with a relay to connect it. Perhaps by OR-ing several channels of the timers daily schedule you can get hourly or at least 4 hour intervals. There are lots to choose from but you'll want to review the instructions online to see if they are appropriate.

By OR-ing the outputs I mean basically tying them together so the relay activates if timer1 OR timer2 OR timer 3 ... are active. Sprinkler outputs are usually just low power relays with a common hot or ground node.

[spindown]

Thanks for the suggestions. This timer does not have to be precise just go on once every
hour and be able to vary the time on from 1-10 minutes. Will have to look for the timer
module mentioned above. I looked into the sprinkler timer but could not find an unit
because "out of season" at this time.
I would be interested in building a circuit using the 555's but my electronic training ended with
the Korean War. I can build it but will need help with a schematic. Thanks again Paul

[Einar M]

I designed a simple circuit that does this a while back. I have posted it at Photobucket/Einarscircuits. Look in the timers album. ( Other interesting circuits there too. )

[CeaSaR]

Einar,

Would it be possible to post a direct link to your folder? I had a hard time even finding an "Einar" over there.

To the great minds out there,

Isn't it possible to chain 555's together to produce a long time "space"? I say space because I envision several
1-shots strung together (maybe 556's) to create the 1 hour (+-) time between triggers. The resultant last pulse
would trigger a secondary line of 555(s) to create the 10 (+-) minute timer. When this timer goes back low, it
could reset the entire chain to start the whole thing over again.

I know that 1 555 can control another 555, but I have never really played with them other than to make noise.

CeaSaR

[Michael Kaudze]

http://s1214.photobucket.com/home/Einarscircuits

[Einar M]

Thank you Michael for posting the link. I didn't have time last night to figure out how. Or more importantly recover from botching it. Are there instructions somewhere?

[CeaSaR]

There are instructions on how to place links at the top of this particular forum (General)
under the topic "Finally beat the the board at the underlining of links" thread. Just
follow the steps and you'll be good to go.

Also, you can go back and edit your post to fix things if need be. No need for a new post.

Thanks Michael for posting the link.

CeaSaR