Spurious triggering of 4013 flip-flop

Thanks. You're in Germany, yes? Is your domestic mains wiring similar to UK? I'm interested whether the different USA approach (apparently a physical stake at the main external wiring box?) is a significant factor in the answer to my question. It would be convenient to be able to treat UK mains earth like the metal chassis of a car!

Terry, East Grinstead, UK

Reply to
Terry Pinnell
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I'll check that this evening.

Terry, East Grinstead, UK

Reply to
Terry Pinnell

I think just the input transistor might be workable solution. Why not jury rig something first? That would reverse signal polarity... The immediate gain is you aren't inputting to a device that works on microamps or less. (specified at Point One microamp maximum at 25 degrees C)

The 4013 should have it's unused inputs tied to ground assuming the other half isn't used for anything. If you didn't already know that...

Check out:

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Notice the .1 microfarad and 100K series input and placement of the

10K....

Like someone has already noted, contact bounce is a problem inherent in any dry contact closure, so you may encounter that with a relay save something like a mercury-wetted reed relay. With contact bounce at the input to the flip flop it would change states very fast and several times, the last state it settled on would be random.

Reply to
default

As the poster "default" noted the clock cleanup doesn't have to be a monostable. Leads to further simplification:

The CP and D inputs can be tied to Vdd instead of Vss if that makes your layout easier.

piglet

Reply to
Piglet

Twice as many relays as necessary. See my post. It's a 19th century circuit I found online, with a small improvement.

At the time I didn't realize the signal comes from his wireless remote.

Reply to
Tom Del Rosso

True, but yours requires a ground free switch contact as trigger instead of a ground referenced voltage, needs both to be multi-pole relays, and needs a resistor to tweak the pull-in/release voltages.

OP says he hasn't room in the box for more relays so I guess neither circuit will get used. As a hobby project it is all fun so who cares :)

piglet

Reply to
Piglet

Thanks for those. As mentioned in the last of my posts to Tom (10:55 today) I did originally try a mono. maybe I didn't filter it hard enough.

I reckon the favourite will be as in that discussion with Tom, namely to use the flip-flop already available at the lounge end. But first I'll see what improvements can be made with some of the other suggestions, starting with reconsidering my earthing. It's all a great learning exercise ;-)

Terry, East Grinstead, UK

Reply to
Terry Pinnell

Yes, I wonder if those monostables you didn't have luck with were edge triggered (triggers the clock input of a F/F) so you were essentially getting the same spike sensitivity you have been seeing that prompted the original question. Using a level sensitive input like Set or Reset preceded by heavy RC filtering ought to be much better.

piglet

Reply to
Piglet

This NG tends to have 19th century politics so why not 19th century circuits? Hiyoooooooo

Reply to
bitrex

If anyone actually builds these though they have to sign a contract to wear a stove pipe hat during construction and say "Zounds! Forsooth whatever is the matter" if it doesn't work properly

Reply to
bitrex

Pin 11 was at 10mV with no signal.

Reply to
Terry Pinnell

Investigating possible ground loop(s) is further handicapped because my scope probes are themselves earthed.

Reply to
Terry Pinnell

Yeah, we all know that Karl Marx was a 19th century economist but his theories had been well debunked by the end of the 20th, by anyone with an ounce of sanity. Unfortunately, Democrats don't have an ounce of sanity.

Reply to
krw

A rather neat way of solving mechanical switch contact bounce is to use a single pole break before make changeover switch (or even a centre off biassed c/o switch) with a non inverting buffer (a pair of not gates cascaded will do the job, nor nand or schmit triggered inverters or whatever is handy for the task).

You need to wire the side contacts to the Vss and Vdd supply level voltages and connect the common pole contact to both the input and output of your non inverting buffer which drives the relay switching transistor.

The short circuit on the buffer's output won't cause any harm during the brief 10 to 20 ns transition to the input logic state as it latches itself to match the switch state (or the last state if using a centre off biassed switch), neatly eliminating the effect of switch contact bounce.

If you're using seperate PSUs at each end, make sure to use the lower voltage one for the switch connections and definitely only have a single point of connection to your local ground reference.

If you're relying on a remote receiver to send a toggling pulse, you can relocate the existing 4013 bistable to the remote Rx unit, add a 74HC14 with all six inverters paralleled up as a stand in for the switch and use two of the inverters in another 74HC14 now taking the place of the bistable latch to debounce and self latch the on/off signal now being issued from the remote controller end of your circuit.

However, I suspect all you really need in this case is simply to relocate the the bistable to the remote controller Rx and forget the debounce self latching non inverter buffer idea altogether. The low output impedance of the bistable chip will provide considerably more immunity against interference on that 60 feet of control line (but only if there's just a single connection point to ground in your circuit).

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Johnny B Good
Reply to
Johnny B Good

due to

or

Has anyone yet mentioned putting loading resistors on the input lines to re duce junk pickup? It might be all you need.

NT

Reply to
tabbypurr

Why not just put everything except the relay and diode at the source of the signal?

Reply to
Mike

add 100K between Q and S for extra crispness.

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

I almost overlooked that fact in my previous reply. It seems to me to be a case of a 'self inflicted problem'. The mistakes being the use of two separated earth connections and bad placement of the flip-flop which should have been co-located to the remote controller Rx unit.

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Johnny B Good
Reply to
Johnny B Good

The main benefit of such hobby projects lies in the 'learning from your mistakes' aspect. Provided the mistakes aren't expensive or fatal, it can be a fun way to learn.

Generally speaking with such projects, you don't learn anything without making a mistake or two. At best, if it works perfectly first time round you're either simply proving your understanding or else just benefiting from 'pure dumb luck'.

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Johnny B Good
Reply to
Johnny B Good

A 'real engineer' won't need to sign such a contract since such utterances are an innate response regardless of the wearing of a stove pipe hat (which is entirely optional headgear anyway). :-)

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Johnny B Good
Reply to
Johnny B Good

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