On 1/25/2011 10:07 AM, wrote:
On Mon, 24 Jan 2011 21:59:20 -0800, Bill Noble
wrote:

On 1/24/2011 9:07 AM, wrote:
I am fabricating a small box that will house a couple of "muffin" fans
to direct air behind a fireplace insert. I have a 3 position switch
(0, 1 , 2) so that I can run either one or two fans. I need a "check
valve" (diode?) to prevent both of the fans from running when the
switch is set for a single fan. I am having a bit of trouble with
selecting a diode. I did a quick google search that leads me to
believe that the diode needs to be specified based on reverse current
to be blocked and the voltage. The fans draw 20W each. For such a
cheap simple part, I wish to buy it at Radio Shack but looking at
their web page: http://www.radioshack.com/family/ind...goryId=2032269
I am having difficulty trying to pick one - many of the diodes do not
even show a spec sheet. Recommendations please. Once I complete this
task I can get down to forming the sheetmetal. Thanks

is there any reason why you don't use a DPDT switch ? no diodes, works
with AC or DC fans
He would need a dpdt center off switch. And exactly haw are you going
to select ONE motor on one position, and 2 on the other with the
motors in parallell? I can see if you tie the commons together, and
tie both terninals of one side together, then feed the motors from the
2 terminals on one end of the switch - for 1 motor switch to the
position that connects the common to the bridged terminals and the
empty non-bridged terminal. For both to the position that connects the
common to the occupied non-bridged and the bridged terminals. Other
end of both motors tied together to the other (neuatral) line.
Any other way?

first, I don't recall a mention of off, but yes, a center off switch is
the way to go. Wire white to both motors. Wire black to both center
terminals of the switch. Connect motor 1 to pole 1 terminal 1. Connect
motor 2 to pole 2, both terminals.

How hard it this?

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