The subject tells the goal. Here is the rest of the story. There is
no micro available. It is preferred to use a dual comparator such as
393 as one of those is already part of the design and having two of
one device is preferable to one of these and one of those.

I have tried and failed. Others care to give it a crack?

John

On Wed, 13 Feb 2008 13:11:08 -0500, John Bachman
wrote:

The subject tells the goal. Here is the rest of the story. There is
no micro available. It is preferred to use a dual comparator such as
393 as one of those is already part of the design and having two of
one device is preferable to one of these and one of those.

I have tried and failed. Others care to give it a crack?

John

I meant to post this over on sci.electronics.design and miss-clicked.

John

This is normally implemented with a flip-flop (bistable). You should be able
to mimic the behavior with two comparators. See any college textbook on
basic digital design.

On Wed, 13 Feb 2008 10:21:02 -0800, "William Sommerwerck"
wrote:

This is normally implemented with a flip-flop (bistable). You should be able
to mimic the behavior with two comparators. See any college textbook on
basic digital design.

Yes, I am aware of that design. Basically the switch provides a
"clock" signal that flips the flop which operates a pass transistor. I
may end up with that.

I just got the idea in my head that it could be done with one
dual-comparator and am frustrated that I cannot figure out how to do
it.

John

On Wed, 13 Feb 2008 14:47:18 -0500, John Bachman
wrote:

On Wed, 13 Feb 2008 10:21:02 -0800, "William Sommerwerck"
wrote:

This is normally implemented with a flip-flop (bistable). You should be able
to mimic the behavior with two comparators. See any college textbook on
basic digital design.

Yes, I am aware of that design. Basically the switch provides a
"clock" signal that flips the flop which operates a pass transistor. I
may end up with that.

I just got the idea in my head that it could be done with one
dual-comparator and am frustrated that I cannot figure out how to do
it.

John
Also, another component is needed to debounce the switch. One
comparator does that nicely so I was trying to combine two functions.

John

John Bachman wrote:

On Wed, 13 Feb 2008 14:47:18 -0500, John Bachman
wrote:


On Wed, 13 Feb 2008 10:21:02 -0800, "William Sommerwerck"
wrote:


This is normally implemented with a flip-flop (bistable). You should be able
to mimic the behavior with two comparators. See any college textbook on
basic digital design.


Yes, I am aware of that design. Basically the switch provides a
"clock" signal that flips the flop which operates a pass transistor. I
may end up with that.

I just got the idea in my head that it could be done with one
dual-comparator and am frustrated that I cannot figure out how to do
it.

John

Also, another component is needed to debounce the switch. One
comparator does that nicely so I was trying to combine two functions.


Why not wire up the dual comparator with mutual feedback and
hysteresis; then use pulse steering capacitors and diodes (reference
bistable multivibrator circuits from 1960's era computing) to
effect a state change with an input transition on the trigger line?

Michael

"Bill Degener" wrote in message
...
John Bachman wrote:
The subject tells the goal. Here is the rest of the story. There is
no micro available. It is preferred to use a dual comparator such as
393 as one of those is already part of the design and having two of
one device is preferable to one of these and one of those.

I have tried and failed. Others care to give it a crack?

John

My ESR meter works like that. check out this schematic and see if you can
use the circuit. http://www.mainelectronics.com/pdf/k7204inst.pdf


Not quite, it doesn't. The on / off button pulls the base of Q1 via D1 to
get Q1 going and put some power on the circuit. The switch also pulls port
line P26 on the micro, which responds by asserting port line P25 which
drives Q2 which pulls the base of Q1, completing the latched power-on
condition. So power is actually controlled ultimately by the micro.

Arfa

In article ,
John Bachman wrote:
The subject tells the goal. Here is the rest of the story. There is
no micro available. It is preferred to use a dual comparator such as
393 as one of those is already part of the design and having two of
one device is preferable to one of these and one of those.

I have tried and failed. Others care to give it a crack?

I've used the Temic U6046B for this. It's actually a timer designed for
car heated rear windows etc and includes de-bounce and a pretty high drive
capability. Sadly no longer made. I've found a use for it on dozens of
projects.

--
*60-year-old, one owner - needs parts, make offer

Dave Plowman London SW
To e-mail, change noise into sound.

On Wed, 13 Feb 2008 16:22:43 -0600, Bill Degener
wrote:

John Bachman wrote:
The subject tells the goal. Here is the rest of the story. There is
no micro available. It is preferred to use a dual comparator such as
393 as one of those is already part of the design and having two of
one device is preferable to one of these and one of those.

I have tried and failed. Others care to give it a crack?

John

My ESR meter works like that. check out this schematic and see if you
can use the circuit. http://www.mainelectronics.com/pdf/k7204inst.pdf

Yes, I am quite familiar with that design. See
www.anatekcorp.com/blueesr.htm. Bob Parker and I collaborate on these
things and the design I am now adapting is his flyback/LOPT tester
kit.

The ESR meter uses the micro to turn off. I have no micro in this
design.

Thanks anyway.

John