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

On Mon, 10 Sep 2007 02:30:56 +0000, Bill wrote:

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.

For how much current? Is it permissable to draw some primary current in
the 'off' state? A nineteenth-century solution is a 3-pole 4-position
rotary switch with no stop and a one-way ratchet. Position 0 is off, 1 is
top-post-positive, 2 is off, 3 is bottom-post-positive.

If you can draw some standby current, you could build the equivalent with
two flipflops and a 2 - 4 decoder, with a debounced pushbutton as the
clock. That would actually cost less than a rotary switch, but you will
still need a relay or an H-bridge if you need substantial output current.

Boy these engineering challenges are getting earlier in the semester every
year...


"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

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

"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

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
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

"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
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

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

"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

James had the right, easy answer.

"Warren Weber" wrote in message
. ..

"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

James had the right, easy answer.

I agree Warren, if I could do it manually, but I need a circuit to do it
automatically every time I remove power. How about like a 555 chip or some
flip/flop that gives you a high output when triggered when you first apply
power? After you shut the system off and turn it back on the output is low.
Next time power off then when back on, the output of the chip is high.
IOW alternate highs & lows each time the system is turn on.

Bill

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


--
JF

On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.

---
Oops...

Fixed the list of crossposted groups.



--
JF

"John Fields" wrote in message
...
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something like a
divide by 2 triggering a 555? Can this give alternate highs and lows on pin
3, the output? I can figure what to do after pin 3. I also wonder if I'm
explaining the problem adequately.

Bill
--
JF

"Bill"


** Hey ****wit.

Your Q requires the device to have a ** memory ** .

Simple enough with a mechanical switch or similar.

But ONLY a permanently powered electronic device or one fitted with
special non-volatile memory can do that pony trick.

Get real - you PITA ******.





....... Phil

On Tue, 11 Sep 2007 14:41:16 GMT, "Bill" wrote:


John ... This is all low current operations. How about something like a
divide by 2 triggering a 555? Can this give alternate highs and lows on pin
3, the output?

No.

The 555 is a timer with an output that goes high for a
predetermined time when its input is triggered, and then goes and
stays low until it's triggered again.

I can figure what to do after pin 3.
I also wonder if I'm
explaining the problem adequately.

---
You may not be.

If you could get into a little more detail about your application it
would help.


--
JF

"Bill" wrote in message
news:gOxFi.6585$d01.6442@trnddc08...
"John Fields" wrote in message
...
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something like a
divide by 2 triggering a 555? Can this give alternate highs and lows on
pin
3, the output? I can figure what to do after pin 3. I also wonder if I'm
explaining the problem adequately.

Bill
--
JF



A good old fashioned 2 transistor bistable with input coupling capacitors
and steering diodes and a small NiCd battery charged when the PSU is on to
retain the bistable state when its off, a driver transistor to power a relay
double pole changeover when the PSU is on.

On Tue, 11 Sep 2007 21:10:20 GMT, "ian field"
wrote:


"Bill" wrote in message
news:gOxFi.6585$d01.6442@trnddc08...
"John Fields" wrote in message
...
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something like a
divide by 2 triggering a 555? Can this give alternate highs and lows on
pin
3, the output? I can figure what to do after pin 3. I also wonder if I'm
explaining the problem adequately.

Bill
--
JF



A good old fashioned 2 transistor bistable with input coupling capacitors
and steering diodes and a small NiCd battery charged when the PSU is on to
retain the bistable state when its off, a driver transistor to power a relay
double pole changeover when the PSU is on.

---


--
JF

"ian field" wrote in message
...

"Bill" wrote in message
news:gOxFi.6585$d01.6442@trnddc08...
"John Fields" wrote in message
...
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something like a
divide by 2 triggering a 555? Can this give alternate highs and lows on
pin
3, the output? I can figure what to do after pin 3. I also wonder if
I'm
explaining the problem adequately.

Bill
--
JF



A good old fashioned 2 transistor bistable with input coupling capacitors
and steering diodes and a small NiCd battery charged when the PSU is on to
retain the bistable state when its off, a driver transistor to power a
relay
double pole changeover when the PSU is on.

I think you got it! Sounds like a viable plan. I will study it. Thanks so
much Ian. This is in the realm of what I need gents, so if there are any
other ideas along this line, please tell me.

Bill

On Tue, 11 Sep 2007 22:51:12 GMT, "Bill" wrote:


"ian field" wrote in message
...

"Bill" wrote in message
news:gOxFi.6585$d01.6442@trnddc08...
"John Fields" wrote in message
...
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something like a
divide by 2 triggering a 555? Can this give alternate highs and lows on
pin
3, the output? I can figure what to do after pin 3. I also wonder if
I'm
explaining the problem adequately.

Bill
--
JF



A good old fashioned 2 transistor bistable with input coupling capacitors
and steering diodes and a small NiCd battery charged when the PSU is on to
retain the bistable state when its off, a driver transistor to power a
relay
double pole changeover when the PSU is on.

I think you got it! Sounds like a viable plan. I will study it. Thanks so
much Ian. This is in the realm of what I need gents, so if there are any
other ideas along this line, please tell me.

---
While seeming attractive at first blush, the down side of Ian's
scheme is that you'll need to build the whole thing using discretes,
you'll need a charging circuit for the battery, and you'll need to
replace the battery when it fails.


--
JF

On Tue, 11 Sep 2007 19:06:23 -0500, flipper wrote:

On Tue, 11 Sep 2007 14:41:16 GMT, "Bill" wrote:

"John Fields" wrote in message
. ..
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something like a
divide by 2 triggering a 555? Can this give alternate highs and lows on pin
3, the output? I can figure what to do after pin 3. I also wonder if I'm
explaining the problem adequately.

Your description is murky and incomplete with the biggie being just
what you mean by turning what on and off..

There has to be a retained 'memory' of what the previous state was so
if one assumes you mean that all power is removed from 'everything'
then the 'memory' device must retain it's 'memory' without power. So
you get suggestions like a magnetic latching relay.

If the power supply itself can remain on, disconnecting the 'red and
black posts' for 'off', or if there can be 'standby power', like what
keeps your PC clock alive when the PC is 'off', then a whole world of
powered solid state devices opens up.

But none of your NE555 and flip flop ideas are going to work if all
power is removed because then there's nothing to 'remember' the
previous state. They go 'brain dead' with no power and will power back
up the same way each time.


Bill
--
JF


A small microcontroller with EEPROM or similar would be a simple solution,
but only if the OP has some experience with them.

Jim

Spehro Pefhany wrote:
On Wed, 12 Sep 2007 08:19:04 GMT, the renowned JimW52

A small microcontroller with EEPROM or similar would be a simple solution,
but only if the OP has some experience with them.

Jim

How do you think people should get experience in the first place? This
is a perfect project to learn on. Less than a page of code on an 8-pin
micro supported by a $50 kit.



Best regards,
Spehro Pefhany

The only issue is the EEPROM cells have a fairly short lifetime, so
there would be a destructive limit to how many cycles the device could
handle... much like with a relay. A clever programmer will use a scheme
where the "toggle" cell is actually a counter that counts with a redundant
code that can be checked for accuracy. If the "toggle" cell shows a failure,
the program marks it as bad, and uses a fresh cell in the EEPROM.

-Chuck

On Wed, 12 Sep 2007 08:19:04 GMT, the renowned JimW52
wrote:

On Tue, 11 Sep 2007 19:06:23 -0500, flipper wrote:

On Tue, 11 Sep 2007 14:41:16 GMT, "Bill" wrote:

"John Fields" wrote in message
...
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something like a
divide by 2 triggering a 555? Can this give alternate highs and lows on pin
3, the output? I can figure what to do after pin 3. I also wonder if I'm
explaining the problem adequately.

Your description is murky and incomplete with the biggie being just
what you mean by turning what on and off..

There has to be a retained 'memory' of what the previous state was so
if one assumes you mean that all power is removed from 'everything'
then the 'memory' device must retain it's 'memory' without power. So
you get suggestions like a magnetic latching relay.

If the power supply itself can remain on, disconnecting the 'red and
black posts' for 'off', or if there can be 'standby power', like what
keeps your PC clock alive when the PC is 'off', then a whole world of
powered solid state devices opens up.

But none of your NE555 and flip flop ideas are going to work if all
power is removed because then there's nothing to 'remember' the
previous state. They go 'brain dead' with no power and will power back
up the same way each time.


Bill
--
JF


A small microcontroller with EEPROM or similar would be a simple solution,
but only if the OP has some experience with them.

Jim

How do you think people should get experience in the first place? This
is a perfect project to learn on. Less than a page of code on an 8-pin
micro supported by a $50 kit.



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

"John Fields" wrote in message
...
On Tue, 11 Sep 2007 22:51:12 GMT, "Bill" wrote:


"ian field" wrote in message
...

"Bill" wrote in message
news:gOxFi.6585$d01.6442@trnddc08...
"John Fields" wrote in message
...
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is that
the pulse to the latching relay has to be short enough so that it'll
be gone before the armature gets to the other contact or both relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something like
a
divide by 2 triggering a 555? Can this give alternate highs and lows
on
pin
3, the output? I can figure what to do after pin 3. I also wonder if
I'm
explaining the problem adequately.

Bill
--
JF



A good old fashioned 2 transistor bistable with input coupling
capacitors
and steering diodes and a small NiCd battery charged when the PSU is on
to
retain the bistable state when its off, a driver transistor to power a
relay
double pole changeover when the PSU is on.

I think you got it! Sounds like a viable plan. I will study it. Thanks so
much Ian. This is in the realm of what I need gents, so if there are any
other ideas along this line, please tell me.

---
While seeming attractive at first blush, the down side of Ian's
scheme is that you'll need to build the whole thing using discretes,
you'll need a charging circuit for the battery, and you'll need to
replace the battery when it fails.


--
JF

The same basic configuration could be assembled with a CMOS quad 2 I/P nand,
it might even be possible to retain the state with a supercapacitor.

On Wed, 12 Sep 2007 13:43:27 GMT, "ian field"
wrote:


"John Fields" wrote in message
.. .

While seeming attractive at first blush, the down side of Ian's
scheme is that you'll need to build the whole thing using discretes,
you'll need a charging circuit for the battery, and you'll need to
replace the battery when it fails.


--
JF

The same basic configuration could be assembled with a CMOS quad 2 I/P nand,
it might even be possible to retain the state with a supercapacitor.

---
It might...


--
JF

"ian field" wrote in message
...

"John Fields" wrote in message
...
On Tue, 11 Sep 2007 22:51:12 GMT, "Bill" wrote:


"ian field" wrote in message
...

"Bill" wrote in message
news:gOxFi.6585$d01.6442@trnddc08...
"John Fields" wrote in message
...
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT dual-coil
magnetic latching relay by using one set of the relay's contacts
to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is
that
the pulse to the latching relay has to be short enough so that
it'll
be gone before the armature gets to the other contact or both
relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something
like
a
divide by 2 triggering a 555? Can this give alternate highs and lows
on
pin
3, the output? I can figure what to do after pin 3. I also wonder
if
I'm
explaining the problem adequately.

Bill
--
JF



A good old fashioned 2 transistor bistable with input coupling
capacitors
and steering diodes and a small NiCd battery charged when the PSU is
on
to
retain the bistable state when its off, a driver transistor to power a
relay
double pole changeover when the PSU is on.

I think you got it! Sounds like a viable plan. I will study it. Thanks
so
much Ian. This is in the realm of what I need gents, so if there are any
other ideas along this line, please tell me.

---
While seeming attractive at first blush, the down side of Ian's
scheme is that you'll need to build the whole thing using discretes,
you'll need a charging circuit for the battery, and you'll need to
replace the battery when it fails.


--
JF

The same basic configuration could be assembled with a CMOS quad 2 I/P
nand,
it might even be possible to retain the state with a supercapacitor.

I know what you mean by a cap retaining the charge but I never heard the
term super cap. What size and type cap would I need and how long would the
charge last? All ears, er, eyes..

Bill

On Thu, 13 Sep 2007 01:11:32 GMT, "Bill" wrote:


"ian field" wrote in message
...

"John Fields" wrote in message
...

While seeming attractive at first blush, the down side of Ian's
scheme is that you'll need to build the whole thing using discretes,
you'll need a charging circuit for the battery, and you'll need to
replace the battery when it fails.


--
JF

The same basic configuration could be assembled with a CMOS quad 2 I/P
nand,
it might even be possible to retain the state with a supercapacitor.

I know what you mean by a cap retaining the charge but I never heard the
term super cap. What size and type cap would I need and how long would the
charge last? All ears, er, eyes..

---

http://www.google.com/search?hl=en&q=supercapacitor

The charge would last for:

(Vp - Vih) C
t = ---------------
I

Where t is the time in seconds,
Vp is the peak voltage the cap is charged to,
Vth is the logic's Vih(min),
C is the capacitance in farads, and
I is the current drawn by the circuit



--
JF

"Bill" wrote in message
news:870Gi.13845$bf1.9609@trnddc04...

"ian field" wrote in message
...

"John Fields" wrote in message
...
On Tue, 11 Sep 2007 22:51:12 GMT, "Bill" wrote:


"ian field" wrote in message
...

"Bill" wrote in message
news:gOxFi.6585$d01.6442@trnddc08...
"John Fields" wrote in message
...
On Tue, 11 Sep 2007 08:31:49 -0500, John Fields
wrote:

On Mon, 10 Sep 2007 02:30:56 GMT, "Bill" wrote:

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.

---
Please crosspost instead of multi-posting.

I've crossposted this to seb and sed.

You could use a 555 pulsing on power-up to toggle a DPDT
dual-coil
magnetic latching relay by using one set of the relay's contacts
to
steer the pulse and the other to switch a DPDT single-side-stable
relay on and off to get your polarity reversal. The caveat is
that
the pulse to the latching relay has to be short enough so that
it'll
be gone before the armature gets to the other contact or both
relays
will buzz or, at least, switch back.

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.


John ... This is all low current operations. How about something
like
a
divide by 2 triggering a 555? Can this give alternate highs and
lows
on
pin
3, the output? I can figure what to do after pin 3. I also wonder
if
I'm
explaining the problem adequately.

Bill
--
JF



A good old fashioned 2 transistor bistable with input coupling
capacitors
and steering diodes and a small NiCd battery charged when the PSU is
on
to
retain the bistable state when its off, a driver transistor to power
a
relay
double pole changeover when the PSU is on.

I think you got it! Sounds like a viable plan. I will study it. Thanks
so
much Ian. This is in the realm of what I need gents, so if there are
any
other ideas along this line, please tell me.

---
While seeming attractive at first blush, the down side of Ian's
scheme is that you'll need to build the whole thing using discretes,
you'll need a charging circuit for the battery, and you'll need to
replace the battery when it fails.


--
JF

The same basic configuration could be assembled with a CMOS quad 2 I/P
nand,
it might even be possible to retain the state with a supercapacitor.

I know what you mean by a cap retaining the charge but I never heard the
term super cap. What size and type cap would I need and how long would the
charge last? All ears, er, eyes..

Bill

Super caps range from about 0.22F to several F, some smaller values are
available with voltage rating of 5.5V but many of the very large values only
2.5V. They are typically used for settings memory in things like cash
registers and VCRs etc.

Another possibility is a lithium coin cell like the 2032, these last for
many years in PC RTC+NVR including the older PCs which often used a 74C04 as
the RTC crystal oscillator.

On Tue, 11 Sep 2007 14:41:16 +0000, Bill wrote:
"John Fields" wrote in message

You could also use a 555 to drive a solenoid which would toggle a
DPDT alternate-action pushbutton switch.

John ... This is all low current operations. How about something like a
divide by 2 triggering a 555? Can this give alternate highs and lows on pin
3, the output? I can figure what to do after pin 3. I also wonder if I'm
explaining the problem adequately.

http://www.digikey.com/scripts/DkSearch/dksus.dll

Cheers!
Rich

"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





As doctor Phil would say, see if this works for you. Attached schematic.

"Herman" wrote in message
. ..
"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





As doctor Phil would say, see if this works for you. Attached schematic.

Sorry, my computer does not open up attachments from email or newsgroups.
Can you send it direct or perhaps reference it on a link?

west

"Herman" wrote in message
. ..
"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





As doctor Phil would say, see if this works for you. Attached schematic.



I can't believe there are no comments. I must be in invisible mode.