Simple toggle circuit?

A lockout mechanism for your existing TFF: Please view in a fixed-width font such as Courier.

. . TFFDebounce . COM . | . [1M] . | . COM-|>|--+---||----- . 1N4148| 100n | . | | . --------- [1K] . | S | | . | | | . ----|D Q|----+---> . | | | . >-------------|>CLK | . | | _| . | | Q|----+--- . | | R | | | . | ---------- | | . | | [1K] | . | 1N4148| 100n | | . |COM-|>|--+---||----- | . | | | . | [1M] | . | | | . | COM | . | | . | | . | | . ------------------------ . . .

The S and R inputs override the CLK circuit. I don't like it, but it does buy you about 50ms margin of protection against spurious CLK inputs. The main thing is to tame that ill-behaved Schmitt.

to find or redraw its schematic. It's a circuit I've used several times, pr obably starting around 1985.

e difficult than I expected. I finally had it working OK on the bench, on V eroboard, using my bench power supply. Then added its own independent suppl y (12V as before) and to my surprise the touch section now produced no sign al. Eventually fixed that by swapping the 2-core mains cable for 3-core and connecting the earth wire to 0V of my circuit. But puzzled why this proved necessary.

metal lamp base (which serves as the touch area) the darned thing became e rratic, with the touch section frequently oscillating when not touched. The proximity of the components to each other and to the metal base, miniature transformer and relay is an issue I'd been apprehensive about, and apparen tly that was justified!

strations to "Let's just buy another lamp"). Such as adding a smoothing fil ter and then maybe following that with a monostable rather than my 4001 Sch mitt. 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 main s hum when I touch the base.

That looks like a RF receiver...

That's a good reminder of why schematic nomenclature was changed from "1.2k" to "1k2". Its dots are really hard to see.

I can imagine the countless man hours spent debugging circuits that had the wrong magnitude resistors. "Oh ... that's one _point_ two k!"

Bob

Get rid of your Schmitt and place my 555 circuit there. I's NOT a "mono", it should be considered an inverter with huge hysteresis. ...Jim Thompson

Looks like fixing your Schmitt is as simple as reducing the feedback. Replace the 1M on the input with 10K, get rid of all those capacitors. See how that works.

Fred, Jim: As mentioned this morning, I've now removed the Schmitt and use d the other half of the 4013 to make a mono. It failed, and I strongly susp ect I've damaged the three separate 4013s I tried. Both on the Veroboard an d in an identical breadboard circuit. Spotted an almost invisible trace of solder between pins 1 and 2 (Q and Q' shorted). Ordered more chips and mean while will experiment with your suggestions. The RH half still seems OK, an d I have an empty 14 pin IC socket from the now redundant 4001, so there ar e several options.

Terry, East Grinstead, UK

It was? Not here!

Have never had that problem. Maybe we buy better printers or maybe when all else fails we can tell the difference between 1 2K and 12K.

Hi Win,

(great to see you back here!)

I spent (wasted...) most of a day looking at ways to do this, including researching ready-made solutions in the form of "on-off controller" chips.

It needed to run off ~10V and be zero-power since it lives strung accross a battery.

In the end I re-invented that exact circuit! (And was quite proud of myself).

On Tuesday, January 5, 2016 at 7:40:35 AM UTC-8, snipped-for-privacy@gmail.com wrote: ...

It's an oscillator that stops oscillating with the extra capacitance of somebody touching the sense plate (antenna).

kevin

That makes much more sense.

Pleased to report the project is now finished and working reliably as a hal l touch lamp.

As I intended, I used the existing 4013 to add the mono, as In some half do zen similar circuits between 1981 and 2005.

My worry that I'd ruined my small stock of 4013s by shorting Q and Q' with an unnoticed solder trace happily proved mistaken. The cause of the earlier failure of the mono turned out instead to be a faulty timing capacitor. Th at lost me a full day! Given its great age, I should have tested it before soldering up. (I'd also not noticed it'd 63V rating; would that have contri buted?)

Once again, on cramming the parts into the smal enclosure it became unstabl e (cycling on/off at the mono period while untouched), but I was able to fi x it by careful adjustment of the preset that controls sensitivity.

Terry, East Grinstead, UK