"Peter Bennett" wrote in message
news.com...
On Tue, 11 Sep 2007 00:27:00 GMT, "Bill" wrote:


"James" wrote in message
...
DPDT switch with center off. Easy
"Bill" wrote in message
news:A%1Fi.420$1n1.105@trnddc02...
Anyone know of a way to reverse polarity (9 to 12V DC) each time the
power
is removed? In this gadget I have there is a small 12V supply. When I
turn
the gadget off and then turn it back on, I wish to have the 12V
reverse
polarities. For another example, I have a black box with 2 posts, the
top
post is +12v and the bottom post is 0v. I turn the power off and the
next
time I turn the power on, I would like the top post to be 0v & the
bottom
post to be +12v. Is there like a simple flip flop chip or ?? than can
accomplish this task? All comments most appreciated. Thanks in
advance.

Bill

I don't think I explained myself that well. Let me try again.

You have a simple 12V supply. The red post is +12V and the black post is
0v
(isolated ground). When I turn the power supply off and after I turn it
back
on ... I want the red post to be 0V and the black to be +12V.
Bill


You want an alternate action DPDT relay - if the contacts are wire
correctly, it will reverse polarity each time power is applied.



--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
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Really, just a relay with no external components? I'll have to try and
figure out how to wire it. I know how to wire a relay to latch but not
reverse. I thought it can be done with a 555 chip with a triggered flip
flop. I feel so close but no cigar yet. Thanks for the suggestion Pete.
Bill