I'd be inclined to hang the pump off a variac to see how little AC amplitude 
you could get away with.  Also, the pump's coil might not be too thrilled 
with square waves, so you might have to do what the cheaper commercial 
12V-to-120VAC inverters do and simulate a sine wave with a two-step 
staircase.  Just some thoughts.

RR


----- Original Message ----- 
From: "Harold Hallikainen" <harold@hallikainen.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Thursday, September 29, 2005 4:10 PM
Subject: Re: [EE] DC drive to aquarium diaphragm pump ideas?


>
>> ....
>>
>>> Any ideas?
>>
>> a small DC motor that you run at 60*60 RPM that moves a piston rod back
>> and
>> forth that physically toggles a switch between positive and negative
>> voltage.
>>
>> - Marcel
>
>
> Pretty elegant! Actually, if I had the DC motor, a crank on it could run
> the diaphragm directly. Turns out this pump is incredibly cheap (cheaper
> than a motor), so I'm trying to figure out a cleaver way to drive it..
>
> Thanks for the ideas... Any more?
>
> THANKS!
>
> Harold
>
>
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