push-push on/off switch

[John Larkin]

John,

Despite all the critical comments I simply took it as a "concept" idea
which does basically work, but would need "tidying up" to become fully
functional.

It is very tidy, and fully functional.

We probably all have seen push-on/push-off or touch toggle switches
which have been implemented using CMOS gates etc but the nearest I can
find to your concept circuit is this practical design by Bill Bowden
"High Current MOSFET Toggle Switch with Debounced Push Button" shown
here http://ourworld.compuserve.com/homepages/Bill_Bowden/page9.htm

Sort of brute force. You can add infinite memory to my circuit with
two more parts.

John

 

[Jim Thompson]

It is very tidy, and fully functional.


Sort of brute force. You can add infinite memory to my circuit with
two more parts.

John

Show it ;-)

...Jim Thompson

 

[Jan Panteltje]

I wonder if you could fiddle something similar with a MOSFET with two

several sections of an LM339, plus accurate current mirrors.

OK here is the ONE active component semiconductor version:


U1 U2
+250 +12
|-- |
| | |
P1- R2 -- ------ +12V
| | | |
| |----R4 ----- |_| sync 0V
R1 |
| |
| |---
|-------\| UJT
| |---
|-> o ut |
C1 R3
| |
/// ///

P1 is a potentiometer that sets the frequency, by controlling the charge current in C1.
The generated sawtooth is linear with in few percent, more if U1 is higher.
Sync lowers the UJT voltage a bit via R2 / R4 to cause early trigger (normally it runs at f < normal).

This is an old trick to get a linear ramp, and in fact the tube circuit uses it too I think.
As C1 charges, the current becomes (U1 - UC1) / (P1 + R1).
For a fixed UC1 (about 6 V in this ciruit), much smaller then U1, the charge current IC1 depends mainly
on U1 / (P1 + R1).
QED.

 

[John Larkin]

Show it ;-)

...Jim Thompson

Can't figure it out?

Actually, it might be possible with one more part.

John

 

[John Larkin]

One problem is if someone holds the switch down for any length of time
you will have an oscillator !

You will not.

www.ckp-railways.talktalk.net/pcbcad28.htm

Really, that's about the ugliest schematic in human history. If you
want to sell your software, that's sure not helping.

John

 

[Spehro Pefhany]

Show it ;-)

...Jim Thompson

Add a small-signal MOSFET and a resistor.


Best regards,
Spehro Pefhany

 

[Tom Del Rosso]

No. But a stable-state switch would be more interesting.

Fun, useful, stable-state, and interesting.

(Maybe not so useful as it once was.)