Simple toggle circuit?

Are you saying the pulse looks "noisy and slow" _after_ the Schmitt?

Post a schematic.

...Jim Thompson

One typically would want a LONG pulse to be required for the touch recognition, and a fast rise/fall pulse to clock the flipflop. It makes sense to use a monostable, AND'ed with the touch output, and only to clock when the full monostable period (tenth of a second?) coincides with touch-always-present. A hex Schmitt inverter (74HC14 or 4584), with diodes, resistors, capacitors, can do the gate/Schmitt/monostable parts.

I'd consider, too, the all-in-one chips like

Hi Jim. Please see earlier screenshot and subsequent schematic in my other thread, 'Why cap needed at Schmitt output?', which is focusing on my current circuit problem.

In THIS thread I'm hoping to get recommendations for alternative toggle circuits, for future consideration.

I think you'd probably be better off just buying a touch chip, say that Microchip MTCH101 that someone else referenced. ...Jim Thompson

Thanks. Will pursue that. In fact I *think* that chip may have been the one used in the touch lamp I'm trying to replace. Bulb blew and apparently fried the chip.

Please see earlier screenshot and subsequent schematic in my other thread, 'Why cap needed at Schmitt output?', which is focusing on my current circuit problem.

In THIS thread I'm hoping to get recommendations for alternative toggle circuits, for future consideration. Not just touch switch activated but versatile toggle circuits for general use.

that's why most of us use a switch

NT

See ABSE.

The one I posted in ABSE uses 4066 switches for some reason (I guess he had some left over) but they are just used as inverters and you could make the same thing with ordinary NOT gates.

Haven't seen it appear on ABSE :-( ...Jim Thompson

I can download it so it's on the Eternal September server.

This was the original name on your SED page:

Bistable_ala_Spehro_Inverters_Back_to_Switches.pdf

Aha! THAT one ;-) ...Jim Thompson

I remember a thread from 15 years ago where Spehro and others posted various examples, but there is no searchable usenet archive any more.

I specifically remember Spehro coming up with one he called his new favorite. It was just a D flip flop and a few passives.

Of course there is the ORIGINAL toggle circuit. I tried this with 12 volt relays and it needed 15 volts, so I added the resistor and it worked down to 10.5V.

RELAY TOGGLE

Press S1 - K1 energizes Release S1 - K2 energizes Press S1 - K1 de-energizes Release S1 - K2 de-energizes

POWER _____ | | +-----------------------------------------+ | | | | K2 | C | . . . . . . .C | . C | . | | . | | S1 . +-----+ +------- | | . | | | +----X \ | . X----+ X X L \ --+-- . \ / O .\O-----X X-----O\. \. . . . . . ./ A . \ \ . / D +----X . .\ X----+ O . O | . . | | . | | . . +-----+ . +------- | . . . . . . . . . . . | . | | . | +-----+ . | | | . | | | K1 . | R ~ 1/2 to 3/4 / C . | coil resistance \ C . . . | / C | | | | | | +-----------------------------------+-----+ | | ----- --- -

Tom, I can't see anything relevant in sci.electronics.basics. Is that what you mean by 'ABSE'?

Can you post a link or a subject name?

I've just about finished construction of the touch activated lamp (but with a last minute additional puzzle over 'earthing', about which I'll post sep arately) but I've incorporated easy access to +V, 0V and the touch switch s ection output. So I can experiment later with alternative toggle circuits f or slow rise time inputs.

Jim, Re your problem over seeing my messages. I'm posting in three ways:

1. From my PC newsreader program, Forte's Agent, to the sci.electronics.des ign newsgroup.
2. From my PC browser, Firefox, to the Google 'group' sci.electronics.desig n, which I assume to be effectively a web version of the newsgroup, identic al in content but perhaps not in timing.
3. Ditto from my iPad.

Terry, East Grinstead, UK

What does the "capacitive" touch switch part of the circuit look like?

alt.binaries.science.electronics ?

joe

}snip{

alt.binaries.schematics.electronic

It's a PDF from JT but not on his site any more. I had saved it. It seems to be something he simulated for Spehro.

The original used 4066 analog switches like open drain NOT gates. I can draw it here with NOT symbols.

I used to be able to make a link from the message ID but this isn't working and I have no idea why.

The message ID is given as:

news:n6c474$dgp$ snipped-for-privacy@dont-email.me

And substituting the actual server name doesn't work either.

news:n6c474$dgp$ snipped-for-privacy@news.eternal-september.org

news:n6c474$dgp$ snipped-for-privacy@mx02.eternal-september.org

Here it is, reposted to the S.E.D/Schematics Page of my website...

It apparently got dropped during a housecleaning where I deemed it without enough explanation to stand on its own.

What it is, but in switch format, is how CMOS master-slave flip-flops work... blazingly faster than gate-derived versions.

I also found my inverter version, maybe I'll write it up as a set. ...Jim Thompson

Hi Terry. Surely you remember the lengthy thread we had on s.e.d. in 2002, on single pushbutton toggle circuits. I enhanced one of the better ones for our book, see Figure 3.99 page 196. It features zero-power when in the off state.

Bill Bowden's 2001 web page helped start us off:

There were 164 posts on s.e.d. in 2002, with the subject "zero-power toggle circuit".

Win's 2016 comment: In all of the circuits below the output power switch is a weak point. It's preferable to use a protected high-side power-switch IC, see Table 12.5, page 826. Many of these ICs have low quiescent current draws, and some that use p-channel switches, are zero.

OK, let's take a quick look through these 164 posts, and a few others as well.

Rf 33k ,----------------+----(O) ,---------/\/\/\------- | --, | | Rf> SW BOUNCE gnd

. ,---- 1M --- gnd . | 1uF + . ,--||--+--||--- gnd . | V+ V+ SW BOUNCE

. ,---------------------+---+-----(O) +13 . | | | . 1.0M 100k_|_ . | | /_\ . +-------, ,--330k---+ | . ,------+ any \ / +---+-----(O) SW . | Q1 | npn / | . | 2n c / \ |--' Q2 . | 4401 b --+-' '--+--|| IRF540 . R1 | e | | |--,S . 4.7M | 10k 1k | . | gnd | | +---------(O) COM . | | +13 | | . C1 +-------o o--' | | gnd . 0.22uF | ,-| === 25V | |/V Q1 __|__ | |

Certainly the part values are not optimum. For example, currents could be scaled down 10x, increasing all R's by 10 and C1 = 0.1uF ceramic. Q2 can be almost any n-channel MOSFET, small to large.

: ,--------+----(O) V+ : | | : R4 | : 10k | : | | : +----||--+ Q2 : | ||>-' : ,-----------------------+ |--, : | R2 | | : R1 ,-- 220k --- | -------+--+---(o) : 1M5 S1 | | | | : | _|_ | |--' _|_ | : +---o o----+ ||-' BSS110 : \ R5 |--, : / 10k | : \ | : | | : ,-----------------------x | : | | | : | ,----------- | -------x : | | | | : | \ R2 | --- D1 : \ R1 / 220k | \ / : / 1M5 \ |--' Q1 --- : \ | ||+ | | +-+ | | +-+ | | | | +-| |N / +-| |N | |e | |--+ | +-+ \ +-+ | / | | | 1.5M | +-----|pnp | | -+- | \ | | \ L +--o o-- | ---| | | | O | sw | ---0.1u | | | A | | --- | | | D | | | | | | | | +----+---------+---------+ Vss GND | 15K | +-----------------/\/\-----+

From: Tony Williams There's a spare inverter in that 4007A Fred. Might as well make it earn its keep. Strap it's input in parallel with the input of the right-hand inverter in the above circuit. Then two choices of what to do with the new o/p.

a) Strap it in parallel with the present o/p, for increased output drive.

b) Dedicate it to driving the 15k, so that the feedback is totally independant of the load.

Might be >

From: Winfield Hill Or use a 4069 and have four spare inverters. :)

Rf +---------/\/\/\ ----------------+ | | | RfO--o---| >O-' | |/ | |/ | .-. | | |220K | | | | T '-' | --- | || '--o o---o-----||--. || | .1uF | === GND

Hi Fred. When I get back to my PC (I'm sending this from iPad) I'll try to find or redraw its schematic. It's a circuit I've used several times, proba bly starting around 1985.

But, despite my earlier optimism, this particular project is proving more d ifficult than I expected. I finally had it working OK on the bench, on Vero board, using my bench power supply. Then added its own independent supply (

Anyway, on heat-shrinking the bits and stuffing them carefully into the me tal lamp base (which serves as the touch area) the darned thing became erra tic, with the touch section frequently oscillating when not touched. The pr oximity of the components to each other and to the metal base, miniature tr ansformer and relay is an issue I'd been apprehensive about, and apparently that was justified!

I'm considering various options, (as well as yielding to my wife's remonstr ations to "Let's just buy another lamp"). Such as adding a smoothing filter and then maybe following that with a monostable rather than my 4001 Schmit t. But it looks like I'll have to abandon this capacitive type and look for an entirely different touch circuit. Perhaps one that will pick up mains h um when I touch the base.

Terry, East Grinstead, UK