At 09:03 PM 10/17/2005 -0700, you wrote:
>Hi All,
>
>I need a timer to turn on/off a small aquarium air pump, but cost is very 
>sensitive while accuracy is not a problem, could anyone suggest me a cheap 
>solution? it could be a circuit, an off-the-shelf product, or whatever 
>method, as long as it is cheap! I need only one on/off interval - once 
>every hour (just roughly will do), each time turn on for about 5 minutes. 
>It would be perfect if the on/off interval can be swtichable to once every 
>ten hours (again on for around 5 minutes) as well. If it is not possible 
>to have such a long or switchable delay, just once on/off interval every 
>hour will be ok.
>
>Thanks in advance!
>
>John

Sounds like an ideal project for a small PIC, run from a wall-wart + 7805
power supply, and a small relay. You probably have most of the parts in
your junk box. Maybe 10-15 parts total including power supply, relay driver,
ceramic resonator, etc.

The software would easily fit into the smallest PIC, so anything that's
lying around would do.

Of course, the wiring to the relay contacts and power switching connections
needs to be done with appropriate care for safety.

BTW, what's the purpose of this device?

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


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