AVR-Chat

On Jan 13, 2005, at 3:23 PM, Jim Wagner wrote:

> You will need some sort of "driver" between the micro and
> the valve. What that driver is depends on how the valve is
> "actuated". It might be AC or DC - it will depend on the
> valve and you have to know that, first.

Don't forget he probably needs electrically actuated valves too. 
Depending on how big his pipes are I'd suggest the local home appliance 
repair/parts center. Else that or go "sidewalk shopping" for discarded 
clothes washers and dishwashers. The water valves and pumps in those 
are tough, cheap and available.

Probably switch with 110VAC. Probably won't find any low voltage relays 
in the washer carcasses. Big selection at DigiKey and Mouser. I suggest 
a ULN2003A for driving the relay coils with DC. The ULN2003A is an 
inexpensive array of 7 darlington pairs complete with series resistor 
in the base and diode across each output.

Good for 70 mA of drive per output with all 7 conducting. Is fair to 
parallel outputs (and inputs) for more drive. If you know all 7 are not 
driving at the same time then one can get more out of a single output 
(read the data sheet). If you are running off a 12V supply then get 12V 
relays to drive with the 2003 and less current will be needed.

--
David Kelly N4HHE, dkelly@HiWAAY.net
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Whom computers would destroy, they must first drive mad.