Spurious triggering of 4013 flip-flop

For something used at such a low rate hard to beat a bullet-proof relay logic toggle flip flop - look Mom no transistors :)

piglet

Reply to
Piglet
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Something like You'll need to invert the output etc, etc.

Cheers

Reply to
Martin Riddle

similar to the generalized concept I had further down the thread, the Schmitt output optocoupler probably a good idea, would eliminate some transistors etc.

Reply to
bitrex

due to

or

You need to replace that line with double balanced twisted pair. You don't need anything special, just differential driver at the keypad and different ial receiver at the FF:

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Reply to
bloggs.fredbloggs.fred

I'm seeing "VDD+0.5" for all inputs there and you just confirmed that VDD is 13.3 (you can have 20.5 if you connect VDD to 20V)

You've exceeded abs max Vin, the chip may be kaput. It's probalbly fine: it seems to work, and CMOS chips are fairly forgiving.

That'd do it! only connect to mains earth at one point. or use isolation between connections. (eg: an opto-isolator in the shed)

--
  When I tried casting out nines I made a hash of it.
Reply to
Jasen Betts

This would probably have more noise immunity than any of the other proposals.

With two 12v relays it needed over 15v because the coils are in series, so I added the resistor (it's never too late to improve a 19th century circuit) and then it worked down to 10.5v because it lowers the holding voltage on K1 and raises the pull-in voltage for K2. I didn't even try to find the optimum value so it could have gone lower.

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 | | | | | | +-----------------------------------+-----+ | | ----- --- -

Reply to
Tom Del Rosso

Duh, of course, you're right, I misread the table! So it's a max of

13.8V for the shed circuit, with a signal of 14.5V from the lounge (15.2 less 0.7 for diode drop). What are the typical consequences of a signal to CMOS exceeding spec by a volt or two?

Ah, that looks like a significant gap in my (hobbyist) know-how. Have never really properly understood 'earthing', but I've been assuming the opposite. I thought that you couldn't overdo it. IOW the more connections you make, the more robust the circuit.

What about actually *using* mains earth wiring as a 0V return wire? Between two well spaced circuits, powered from supplies using different sections of mains wiring, so that only the one long length of wire, carrying the signal, is needed?

Terry, East Grinstead, UK

Reply to
Terry Pinnell

So, pin 11 gets 15V minus diode-drop, but pin 14 gets 4V? That seems rather outside the maximum ratings. Apparently it hasn't killed the 4013 outright, but who knows what it might have done.

Sylvia.

Reply to
Sylvia Else

4V? It's 13.3V.

See also my conversation with Jason.

Terry, East Grinstead, UK

Reply to
Terry Pinnell

Thanks, I'll consider that. May be too great a change for the current circuit but I'll certainly b/b it some time and may use it for future toggle circuits.

Terry, East Grinstead, UK

Reply to
Terry Pinnell

current flows though the ESD protection diodes, until the signal voltage dips or VDD rises enough to stem it... in your circuit it's hard to predict how much current.

You might find 10V AC between the two ends, depending on what's going on, fault current, electromagetic pick up from the loop formed by the signal wire and the ground wire, spikes from electric storms,... with a slow enough low pass filter you can probably filter all those spurious signals out.

but you'd still need to square it up with a schmitt trigger to keep the

4013 happy.

A optocoupler with say 2000V isolation is a bit of a sledgehammer to crack a nut, but it's hard to guess if it's going to be a peanut or a coconut, and optocouplers are cheap, and can be salvaged from old switch-mode powersupplies if you have none on hand and don't want to order more parts.

--
  When I tried casting out nines I made a hash of it.
Reply to
Jasen Betts

Or what it might have to the diodes. It might be worth measuring the voltage on the pin 11 to check that it's really dropping to zero. If it were pulled up somewhat because of leakage through a damaged diode it would be reducing the noise immunity.

Sylvia.

Reply to
Sylvia Else

A kinda philosophical comment...

Running a wide open line any length at all, into a CMOS gate seems like taking careful aim at your foot; and blowing it away.

Use relays, big clunky electro-mechanical things, that are slow to respond and take a few hundred milliamps to work. Nothing less than a nearby lightening strike will phase them.

Ditto transformers. I had to run a data line to a remote location (1+ miles or so along cable runs, running mains power) I used some pulse transformers, laid out the circuit board so there was no way the grounds could talk to each other, big spaces on the circuit board and ground traces between. so a lightening strike wouldn't arc across and fry an input. Separate power supplies, of course... (But that was in a laboratory and money was no object, and in the 70's computers cost big bucks - a mainframe from HP - you-break--it-you-buy-it)

Think opto isolators... they are amazing for getting rid of ground loops and noise and correctly applied are very fast (if you need data rates in the MHZ range)

I have a driveway loop sensor some 200 feet from my house. It has power run to it from the house and gives me a relay contact closure when it senses a car and that operates another relay in the house. No false alarms whatsoever. For people detection there's a microwave field disturbance sensor logically anded with a passive IR sensor. I get about one false positive a year out of that.

The remote location has an earth ground with gas ionization-type circuit protectors to shunt lightning to ground.

If you enjoy a challenge, or are dead-set to use what you have for some less than rational reason, by all means run a line along the ground and dirt into a CMOS input.

I don't know what you have, but my first guess would be to eliminate any possibility of ground loops. Ground at the input side only.

Then I'd isolate the signal from the input to the CMOS gate. If you have unlimited power (a watt or so) at the signal source and aren't running data lines, use relays.

Like folks suggesting Schmitt trigger IC's? Relays have built in hysterisis and are damn near bullet-proof. And they are slow, takes them thousandths of a second to work! Relays have evolved too and some special purpose ones do some pretty amazing things.

Choice two would be opto-isolators.

I donno if lightening is a concern, but that changes the whole ball game. Then you are designing for nothing less than bullet-proof, and lines into CMOS IC's is verboten right from the get-go..

Reply to
default

Interesting that it needs no debouncing. We only need that to interface mechanical switches and solid state. So it occurs to me that if we ever have molecule-sized transistors that switch with one electron, we'll need to "debounce" conventional outputs to drive them.

For your purpose, why don't you put the FF inside with a short wire from the button, and use the long wires to drive the relay?

Reply to
Tom Del Rosso

Also, on 1/4/16 Win Hill posted a compendium of toggle circuits, some of which were discreet, with 2 transistors and much better noise immunity than a 4013. Also tolerance for slow rise time and spikes. You were in that thread so I don't understand why you used this circuit.

Reply to
Tom Del Rosso

Although having some negative practical downsides (like discarding the case for a larger one) I might try that. I assume you simply mean taking the noise-prone input to an NPN transistor driving a relay which then switches +V (or a fraction of it) to the original relay driver? A sort of mechanical, slower echo of the original?

-------------------- More trouble-shooting info: This morning, when I switched on the shed workshop's mixture of incandescent and fluorescent lights, the circuit toggled two or more times. (I had added an LED so that I could see the status, and it came on and stayed on, so an even number of spurious pulses.)

Terry, East Grinstead, UK

Reply to
Terry Pinnell

Don't use a relay to directly clock the 4013 because the relay contacts will have bounce and cause multiple triggers so you'd be no better off as you'd need to clean up the relay contact bounce.

I think the suggestion was to use relays throughout, as in:

piglet

Reply to
Piglet

If rebuilding from scratch is too painful an idea then you might be able to press the other half of the 4013 into making a crude level triggered monostable to clean up the trigger for the existing toggle. Here is a sketch:

piglet

Reply to
Piglet

Duh, I missed that opportunity! As you see here, I designed my late 90's RC Unit with half of its 12 outputs 'Direct and half 'Flip-Flop'.

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For years Key #7 has been unused. (I no longer toggle the pond waterfall pump but use a daily on/off timer.) So I could use that instead of Key #2.

Before I do I'd like to satisfy my curiosity about some of the other solutions offered. And also to identify and remove all but one of the places I've connected UK mains earth to my circuit's 0V line, as I gather that's desirable. (For UK mains too? I understand the US handles grounding differently.) But that will have to be at the RC end in the house. The rest of my buttons are doing their job fairly sweetly and I don't want to risk that state.

Terry, East Grinstead, UK

Reply to
Terry Pinnell

Off out in a minute but look forward to re-reading that 51-post thread soon.

In mitigation it was some 16-17 years after I made the RC unit and probably 14 years after I added the 'Dining Lamp' circuit using key #2. My notes from 2004 include this: "Originally included a mono made from 4013 LH, as input is not noisy; in fact, it added to risk of spurious triggering."

Apparently 15 years ago the glitches were less serious, so I've plainly made some changes since to make them worse.

Terry, East Grinstead, UK

Reply to
Terry Pinnell

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