How to shield a live wire at 240V ?

[_q12x_]

I have a electronic board with leds (made by me) that is driving a relay. When that relay is closing it’s contacts, is actually switching the 240V for the light bulb switch in my room. This board is quite long, like 50cm (half a meter). The relay is in the left corner, and the live wires from it goes in behind the board to the hole in the wall for the mains switch. I also have a mild steel sheet behind my board that is grounded. It is shielding the interference of the 50Hz from the live wires from the wall to my sensitive circuit. But even If I have this grounded metal shield behind my board, the live wires from the relay are still affecting my entire circuit board, keeping it ON all the time. If I am disconecting the live wires from the relay, the board is functioning very well. Another IF, is if I disconnect the ground from the metal shield, the circuit board goes nuts. So the shield is doing it's job fine, but only for the live wires inside the wall !!! But not for the wires from the relay to the live switch.
- I want a way to shield these wires !
Thank you !

 

[telectrix]

could you fit the relay in the switch box so it's behind the sheet metal shield?

 

[SparkyChick]

What is the boards function? Can you post a picture?

 

[Wilko]

Hi - pic and circuit diagram .

 

[Lucien Nunes]

There seems to be a problem with your electronic design that is making the circuit too sensitive to interference. Let's see the circuit.

Also, you give your location as New York but speak of 240V 50Hz lighting. Where are you?

 

[_q12x_]

could you fit the relay in the switch box so it's behind the sheet metal shield?

@telectrix - Thank you for your good answer!
Yes, that is my plan as well. But until I will make this operation, I was thinking maybe I can shield those wires, with all the components on my board as they are now, without any other modification. I will modify it in the end, exactly as you say, but... I wanted a more convenient way.

There seems to be a problem with your electronic design that is making the circuit too sensitive to interference. Let's see the circuit.

Also, you give your location as New York but speak of 240V 50Hz lighting. Where are you?

- Thank you. Yes, you guessed right. The board contains a presence sensing module, meaning, when my hand is in vicinity to that module, it will output high +5V to the next module. It is very sensitive module indeed. And without the metal shield behind it, the entire board will just stay ON all the time, having erroneous behavior. Exactly because of this sensibility of it. And my guess is that 50Hz from the wall wires are not interfering with only the sensing module, but with the entire circuit board, which is quite large and spread. And yes, I like New York but im in Europe.

So tell me straight. Those wires can not be shielded at all ? I am discussing this problem on other forum but for electronics and not electrical like this one here and they got silent about this part. So I figure out to ask more around.
Thank you so much for the direct answers so far !

 

[Lucien Nunes]

Tel has the right answer. Put the relay in a box, separate it from the main PCB and just run the DC coil circuit to the box. Ensure that the 230V AC and ELV DC circuits are properly insulated from one another, so that in the event of accidental damage, the DC circuit is not likely to become live. If you are making this part of your electrical installation, there are constructional standards that you should adhere to, in order not to invalidate the electrical installation certificate on your house.

But, as I said earlier, an electronic device that doesn't work correctly near ordinary domestic power cables is not a practical device because that's a very severe limitation on its usage envelope, like a phone that doesn't work in the dark or an electric toothbrush that must not be used in the bathroom. A significant amount of R&D is often needed to overcome issues of this kind, over and above what is needed to make it carry out its basic functions.

 

[pc1966]

So tell me straight. Those wires can not be shielded at all ? I am discussing this problem on other forum but for electronics and not electrical like this one here and they got silent about this part.

You can get shielded power cables, examples include SWA (steel wired armour) and Flexishield or similar cables to BS 8436 (UK standard) or IS 273 (Republic of Ireland standard). But they are not commonly used for indoor wiring.

As Lucian explained above, you have to design something to work in the typical environment it will be used. Working is a restricted environment is fine for laboratory and other specialised cases when you can arrange it, but not as a general product for home use.

 

[_q12x_]

You can get shielded power cables, examples include SWA (steel wired armour) and Flexishield or similar cables to BS 8436 (UK standard) or IS 273 (Republic of Ireland standard). But they are not commonly used for indoor wiring.

Then... can you explain why the metal shield is shielding the live wires in the wall and not the ones outside the wall? By the way, the wall wires are thick and my outside wires are thin in diameter. Probably it will be the same intensity of the field on both. I imagine. I really don't know.

As Lucian explained above, you have to design something to work in the typical environment it will be used. Working is a restricted environment is fine for laboratory and other specialised cases when you can arrange it, but not as a general product for home use.

Oh, this is just a personal project. Not a public or commercial one. Don't worry. It's destination is only to my room use. And is very experimental as well, with exposed circuits and components. I would not trust to mount it on other places than mine. Haha. But is a good point you bring and and a fear for "some" out there doing too weird things.Interesting indeed.

 

[_q12x_]

Tel has the right answer.

It's an answer. Its a good one indeed, but I wait maybe more ideas will come.

 

[_q12x_]

You can get shielded power cables, examples include SWA (steel wired armour) and Flexishield or similar cables to BS 8436 (UK standard) or IS 273 (Republic of Ireland standard). But they are not commonly used for indoor wiring.

Excellent answer ! I mean I know the general term of coaxial, triaxial, and another 2. But that is just theory that I happen to read about in my research. And actually plan to shield my cable in a very short time, just as a test. Just to see if it will affect in any way. It will be awesome to tell me now, before doing anything if its worth to try or not.

 

[Lucien Nunes]

You can use a shielded cable for the power but that is not dealing with the root cause of the problem. It's a kludge like attaching a light to the phone that won't work in the dark.

If you show the circuit, we might be able to suggest some tweaks.

 

[pc1966]

Excellent answer ! I mean I know the general term of coaxial, triaxial, and another 2. But that is just theory that I happen to read about in my research. And actually plan to shield my cable in a very short time, just as a test. Just to see if it will affect in any way. It will be awesome to tell me now, before doing anything if its worth to try or not.

I see you are down as NY in the USA, their electrical codes are very different to ours (UK) so I have no idea if they permit the equivalent of Flexishield for power.

Here it is used for indoor wiring where you can't have RCD protection for any reason, but it might get damaged (e.g. DIY person putting a nail through it). It has aluminium foil and a drain wire for earth designed to open a typical MCB safely on fault current. It also gets used a lot on farms as rats seem not to like chewing it and safer for livestock. They also make a cat-urine flavoured version to further deter rodent damage:

Flexishield R How It Works

Flexishield R How It Works

www.flexcables.co.uk

@Megawatt might have ideas on what it allowable for shielded style wiring in the USA. I think the USA goes in for a lot more conduit systems (EMT) and that provide similar benefits to Flexishield as well as higher fire protection, but with a much higher installation skill/cost.

 

[_q12x_]

I really tried my best to keep it simple.
But if you insist, yes I can show you the circuit, no problem, but im afraid it will add more unnecessary problems to you to resolve (that are already tested and solved).
This circuit is on my deviantart account.
Click on the image to zoom in. It is at full rezolution so you will be able to see the tiniest text on it.
Link here: Q20201219 Led Wings Projekt Circuit by q12a on DeviantArt - https://www.deviantart.com/q12a/art/Q20201219-Led-Wings-Projekt-Circuit-864540519

 

[_q12x_]

You can get shielded power cables, examples include SWA (steel wired armour) and Flexishield or similar cables to BS 8436 (UK standard) or IS 273 (Republic of Ireland standard). But they are not commonly used for indoor wiring.

Give me more examples or names like these. I dont know them.
My suggestion is to also give me the names for the most powerful Electric field shielded cables there are. I probably dont have the money to buy them but is a good introduction for me, and a bit of practice to you. In time is fine, if you cant right now. I am very patient.
Thank you for the formidable answers so far. I really like them.

 

[pc1966]

It seems you are relying on that unscreend supply noise to trigger it when you move close to the antenna!

Also that input MOSFET has little protection so a bit too much charge and you can blow the gate insulator. Having a 10V zener to 0V might be enough to protect it.

Why not have adjustable sensitivity. You could replace the lower 10K off the MOSFET (and some arrangement for driving the LM3914) with a potentiometer so you can set what it needs to trigger?

 

[_q12x_]

It seems you are relying on that unscreend supply noise to trigger it when you move close to the antenna!

Also that input MOSFET has little protection so a bit too much charge and you can blow the gate insulator. Having a 10V zener to 0V might be enough to protect it.

Why not have adjustable sensitivity. You could replace the lower 10K off the MOSFET (and some arrangement for driving the LM3914) with a potentiometer so you can set what it needs to trigger?

Where to put the zenner more precisely? (A zener must have a resistor in series for its protection as well). Can you be kind and make a screenshot on the area of the circuit and draw over it for me, please? Thank you. I really like the protection idea.
I can change little things, but not much. I will try the best I can to change anything I can.
But you see how quickly you defocused from the main issue ? I get that you are refering to the circuit sensitivity... but right now it is a very strong interference I have to keep it out. Not sensitivity. It is working excelent on my table, now I manage it to make it work on my wall as well, but now this problem with wires.
I plan to shield the wires.
Can you give me some advice on properly shield them? Thank you ! I also have an idea, using grounded aluminium foil and a grounded wire inside. Also twisting the the wires I see it is more efficient for shielding. But this is all I got so far.

 

[Lucien Nunes]

it is a very strong interference I have to keep it out.

No, it's just normal house wiring. My electronics lab has unshielded power cables all around it, there is a 3-phase electrical panel with unshielded cables at the end of my workbench and transformers underneath it, there are variable-speed inverter drives in the next room, but everything here works perfectly including studio-grade analogue audio equipment with its covers off.

Personally I would redesign the detector to work a different way, there are lots of options. But at least do something about that floating gate. The diode rectifies stray capacitively coupled noise and charges the gate. But then what? How does the gate discharge? Just leakage? That will vary with temperature and humidity. The Fostex G24S was a 24-track 1" tape deck that had some JFET gates connected directly to diodes, in the monitoring signal switching. These were still showing up as a fault some 30 years after the unit was launched.

Also twisting the the wires I see it is more efficient for shielding.

It's helpful against against electromagnetic coupling, won't make much difference to electrostatic coupling on a screened cable.

 

[_q12x_]

A video update. Nothing is said there that we didnt discussed already. It's a test that failed.
Watch it if you wish.

 

[Megawatt]

I have a electronic board with leds (made by me) that is driving a relay. When that relay is closing it’s contacts, is actually switching the 240V for the light bulb switch in my room. This board is quite long, like 50cm (half a meter). The relay is in the left corner, and the live wires from it goes in behind the board to the hole in the wall for the mains switch. I also have a mild steel sheet behind my board that is grounded. It is shielding the interference of the 50Hz from the live wires from the wall to my sensitive circuit. But even If I have this grounded metal shield behind my board, the live wires from the relay are still affecting my entire circuit board, keeping it ON all the time. If I am disconecting the live wires from the relay, the board is functioning very well. Another IF, is if I disconnect the ground from the metal shield, the circuit board goes nuts. So the shield is doing it's job fine, but only for the live wires inside the wall !!! But not for the wires from the relay to the live switch.
- I want a way to shield these wires !
Thank you !

Have you tried plenum rated cables

 

[_q12x_]

Have you tried plenum rated cables

No and this is the first time I am hearing about them. I just look over some explanations about this plenum cable and from what i understand, the only difference between plenum and non-plenum is the fire hazard non-plenum are. So plenum is the same cable but with a self-extinguishing plastic/isolation cover. Its more about safety with them. But nothing about shielding. So it is not really helping me in my case here. Thank you for mentioning them, I learned something new.

 

[_q12x_]

Personally I would redesign the detector to work a different way, there are lots of options.

Give me all the options you can think of. As many as possible; all of them.
(i also have a backup plan for the sensing circuit as well, but I leave it as the very last alternative, in case everything else fails).
Thank you !

 

[Lucien Nunes]

I don't have time to list all the options. I don't mind giving a few suggestions.

Idea #1. Reflective optical proximity detector with built-in synchronous demodulation e.g. Sharp IS471. Package contains an IR photodiode that is aimed at the detection area. A separate IR LED is also aimed at the detection area and connected to the LED output pin on the IS471. When an IR-reflective object enters the area it reflects pulses from the LED back to the photodiode, which enables the output. The key is in the synchronous demodulation, which rejects even strong IR interference e.g. from room lighting and hot objects, only responding when its own LED pulses are reflected. Obviously you can set the sensitivity by the LED current, beam angle etc.

Advantages - immune to electrical interference. Small and cheap. Easy to fine-tune response.
Disadvantages - Sensitivity depends on IR reflectivity of target. Might not work in direct sunlight.

 

[_q12x_]

Please help !
Another update, this time i made a very short video (2min) where I present the problem.
I inserted the 3'd relay inside the switch socket and I command it with 5V from the 2'd relay.
But the 2'd relay is vibrating like crazy when I power the board.

After that,
I tested it on my working bench and is doing the same. So, no mains interference at all. It is not influenced by the live wires this time.
If I disconnect the 3'd relay from circuit, everything works fine.
If I put 5V on the 3'd relay, is working fine.
My PSU is showing me 1A , sign that something is in short. But Nothing is in short. It behaves as is in short. Only when I connect that 3'd relay. It is weird as hell. I checked for short with my multimeter and nothing is in short. But once I power it up, it goes to 1A straight.
Actually I tested again and is not rising to 1A but to 1.44A ! Way over my custom limit that I set on my PSU . Very-very strange.

 

[_q12x_]

It was a logical error. Im too tired of it probably.
I solved the problem. It was a short after all, but a logical one. Eh... stuff happens.

 

[marconi]

-q12x- : good afternoon. What a nice little project. If you’d like I will try to help you produce a working design. What knowledge do you have of semiconductor electronic circuitry using bjts and fets? Or are you copying designs ( no shame in that) available on the internet?

To help me and you answer this question tell me what kind of transistor is the 2N7002? google and study its data sheet.

is it an enhancement or a depletion mosfet? What do these mean?

is it a p channel or an n channel?

which way around are it’s drain and source connected to the positive and negative rails of the dc supply?

is the way you have drawn the transistor connected for the sensing circuit correct?

Is this the way you have actually connected this mosfet?

There are some clues in my questions.

 

[_q12x_]

- Thank you that you liked my project.

 

[_q12x_]

New update:
The movie is very short (3m40s)
Please watch it, I explain in it what I did and how it works.

 

[marconi]

I have studied your circuitry and am clear on how it is meant to work in theory. There are some aspects of the design which we need to correct to account for contact bounce - the contacts connected to the 555 chip for example and there is no common ground/) 0Volt point for the LM3914. There are far too many long exposed interconnecting leads carrying low currents which are vulnerable to noise pick-up. The way the MOSFET is being used - common drain/source follower - is not suitable nor the lack of any fixed albeit variable bias on the gate of the MOSFET.

A clearly apparent problem is that this MOSFET is permanently 'on'. Not surprising since it is an enhancement mode FET and you have a resistor diode combination connecting its gate to the +5V rail. it takes very little current to charge up the MOSFET's internal gate source capacitance to such a voltage that the so-called gate thresheold voltage Vgs is exceeded which will change the state of the n channel between the drain and source from insulating to conducting. There is no resistor to the ground/0V rail to discharge this voltage. And there is no way to adjust the sensitivity/threshold to change when the MOSFET turns on and off.

The LM3914 is expecting a voltage at its pin 5 which as it rises from 0V to 5V switches its eight outputs on in sequence as the voltage crosses eight voltage values/references. Once can also adjust these voltage values/references by suitable circuitry at pin 8. To achieve the effect of the gradual LED illumination of the wings your sensing circuit is required to produce an output voltage which increases with the proximity of the hand to the antenna. Your sensing circuit is acting as the 0-5V signal source in Figure 1 of the attached datasheet.. but as currently wired your sensing circuit is more likely to just ramp up pin 5 between 0 and 5V and then stick at 5V - so all the LEDS stay on. (Did you check the 2N7002 was actually wired in correctly?)

https://www.ti.com/lit/ds/symlink/lm3914.pdf

Anyway....let us proceed in steps. I do like the way you have constructed the circuit out of sub-systems - very intelligent and shows an engineer's approach to design - well done.

But first things first. We need to have a suitable and reliable power supply. I want you to estimate how much current this supply must deliver at 5V dc when all LEDs are off and then when all LEDs are on. Please show me your working. Also tell me about the power supply - what are you using?


THERE IS AN IMPORTANT CONDITION TO ME WORKING WITH YOU WHICH YOU MUST AGREE TO - YOU ONLY EVER WORK ON THE CIRCUITRY WHEN IT IS DISCONNECTED FROM THE 230v AC BY WHICH I MEAN THE WIRES BETWEEN YOUR CIRCUIT AND THE ORIGINAL SWITCH ARE COMPLETELY REMOVED - AGREED?

And which country or town are you in?

PS: For my own amusement I have ordered some components to attempt what you are doing in a different way in case we are unable to make your circuitry perform as desired.

So - 5Volts dc nice and safe. 230V ac DEADLY!!!!!!

Oh, if you don't already have one please buy a cheap digital voltmeter something like this one I use:

https://www.amazon.co.uk/Compact-Digital-Multitester-Diode-Test/dp/B000L0RINQ

 

[_q12x_]

Mister @marconi , thank you for your kind answer and involvement.
I like your perseverance and I think you like this project as much as I do. Or at least is intriguing to you.
A little introduction first. I am an artist. I am from romania the awesome country where nothing is possible. But I believe things can be done, even if they look impossible. All we need is a bit of ambition. I am not an electronist or electrical guy. I made what I made because I want to make it and because I can. If I could not believe i can, I would not start it. You must understand something. Even if I am not a professional electronist, that doesnt mean I am automatically a rookie. I do electronics for about 30 years, but sporadically (not continuously). So I know something, and for sure I have some gaps, Im not afraid to say it.
You seem to know very good what you are saying. Is my impression. You seem to know more in depth the electronics in general. Probably because (i want to believe) you are doing it all the time. I like it very much and I would love to learn something from you.
There are so many things to cover... I am afraid you will get tired of it very quickly.
First of all, I work alone and simply by that, it is taking a lot of time to accomplish something. I work on this project for 7 months now, and also with any help I could find on internet. People in my country they only say they know, and I believe them, but nobody moved a finger. And is fine by me. People from america, on the other hand, they did got involved very nicely and I have a great deal of respect for them. Im talking about forums, like this one.
I will answer to your questions, indirectly, by giving you some links to my project.
I made a playlist in my youtube channel, where I put all my progress with this project.
How I started, the breadboard tests, failures, problems, finally some achievements, etc. Scroll fast through the movies to not get bored about their long --- content. I am not a good youtuber and I talk unnecessarily too much sometimes. It's also hard for me to translate it live, so that makes me look like an idiot. See the playlist here:
https://www.youtube.com/playlist?list=PL6NJF1kQFOAImsLpNil3wNCb8POZQLYM0
Also, a text to read about this project. I have a description on the page how to download it. It is in a zip form.
q20210117 Led Wings Projekt by q12a on DeviantArt - https://www.deviantart.com/q12a/art/q20210117-Led-Wings-Projekt-867429226
You are welcomed and I also encourage you to browse in my account there, to see my glorious art. If you please.
Here is the online version of the same text to read. You dont have to download anything, but you have to scroll down ... a lot. There are currently 25 artpages.
https://www.artstation.com/artwork/zOBaED
You are welcomed and I also encourage you to browse in my account there, to see my glorious art. If you please. On deviantart I have everything, while on artstation I put only the good and important art.
If you are bored and start to hate my guts, don't tell me. I know. Hahaha.
I am also sorry to not respond to everything you asked me to. Usually I respond, but only to people that are close to me. I am very curious about your response now, after dealing with my mountain of information. Or maybe I am perceiving it as a mountain, because it took so long to make it all... who knows, it's all relative.
Another very important aspect. This project is nearly done. Very close to finish. I only have to discover the source of the interference in my circuit. I mean, I believe everything you said so far and I agree with your diagnostic. But you must understand, that this thing is tested and over-tested, and you come now, ta-da, ta-da, "change the circuit !". It's not easy for me to cut everything I done so far. I can not make any in depth operations for every suggestion I get. So I am patient and cut what I think is absolutly necesary to get as closer as I can to the result I want. If you argument it clear enough to make me believe it is absolutly necesary and it will indeed make it work, then I will listen to your advice. But until then, you are the new guy for me. I will try to make some of your rectifications, but only those that are not very damaging. And also because I work slowly, and Im afraid not to damage it as fragile as it is, it will take time anyway to make all the modifications you are suggesting. In the lack of better ideas, I will try everything I have on my plate, including your advices as well, but it will take time, so please understand. Insist on something that you are 100% it will work and I will give it priority if I believe you enough.
On a final note, All I needed from you here, is a way to stop that interference, to shield it, or to completely avoid it. Its my number one problem to resolve now.
Thank you very much for the support so far ! I will try what I can.

 

[marconi]

Thank you for your reply which I will read carefully tomorrow morning when I get up. Two of the nurses who attend my wife are Romanian. They are very professional and have kind happy personalities which are essential since they are in our home for 6 hours each day. So, helping you and your country will be some payback for that. They will be amused to know I am in contact with you.

I am cooking at the moment so I have to sign off for today. I will write again tomorrow.

 

[marconi]

I have now read your note to me twice and I understand what you have said very clearly. Yes - I have come along as a 'clever dick' 'know-all' and you are nervous about making changes to your design and its construction because you have spent 7 months working on it. I suggest - so tell me if you agree - we do some simple tests on your circuitry first. They will involve disconnecting some wires but not dismantling any of the components. Depending on what we find you can then decide to make some changes or not. It would be really helpful to know if you have a digital or analogue multimeter so that we can take some voltage measurements.

To save time and assuming you agree to the approach I just mentioned please measure these voltages for me with respect to the 0V rail:

1. With all circuitry disconnected from 5V power supply the output voltage of this supply;
2a Now reconnect the circuitry. What is the supply voltage when all the LEDs and relays are off?
2b. What is the supply voltage when all the LEDs and relays are on?

Now disconnect the wire at pin 5 of the LM3914 which comes from the sensing circuit.

3. Using a short piece of wire - a jumper - connect pin 5 to 0V - all the LEDs should turn off - make solid connection do not just hold the wire;
4. Now move the jumper to connect pin 5 to the 5V rail - all the LEDs should turn on;
5. Make a potential divider from two resistors R1 and R2 say 10K and 10K and wire this across the 0 and 5V rails. If you have a small value capacitor - a few uF - please wire it across the resistor R2 which connects to the 0V rail. Connect pin 5 to the point the two resistors join together - approximately half the LEDS should light;
6. Now remove the resistor R1 which connects to the 5V rail so that there is only one resistor which connects pin 5 to 0V - all the LEDs should be off. Take a jumper wire and connect one end to the 5V rail. If your circuit (apart from the sensing circuit) is working as you want it to, if you repeatedly connect pin 5 to the 5V rail the LEDs should all turn on when raise pin 5 to 5V. If you repeatedly touch and then untouch pin 5 and touch and then untouch the LEDS should turn on and off and the relays should be turning on and off - toggling - as you want them to do - to eventually turn your room light on and off everytime the wings are illuminated. Everytime you touch pin 5 to 5V the capacitor will charge up - when you untouch 5V rail the capacitor will discharge through R2 - allow a little time for this to happen.

This is probably enough for now. Please let me know how what happens.

Regards

Marconi

 

[marconi]

So far I have watched Led Wings Projekt 1, 2 3 and 4.

 

[stevethesparks]

Fair play to you Marconi. You have gone way beyond the standard reply, and continue to do so. Interesting as well. ?

 

[_q12x_]

So far I have watched Led Wings Projekt 1, 2 3 and 4.

Thank you... as i mentioned, it's a lot of talking, it's probably better to move forward faster by scrolling.
I am just starting your experiments right now.
But pay attention to 1 very important thing. The circuit does work excellent when is on the workbench !
It only gets wierd on the wall, in the very close vecinity of the 50Hz. So your experiments are on a working circuit ! Ok?
I should probably mention this little detail as well, on the breadboard it worked in a way, after I assembled it on my modules boards, it worked totally different (it was my iron table that was ungrounded at that time) but still a big difference. Its because the breadboard have in it a lot of wires as well. So those were sensitizing the circuit. I was not aware at that time, I figure it out in time, after. Right now on the table I am working I have live wires but is a respectable distance, like 40cm to them from my circuit. But on the wall... is close as 5cm to working live wires, not standby ones.
Your experiments I presume, are to be taken on my workbench and not on the wall. The thing is on the wall, I have to keep everything in equilibrium, and is not optimal to work there, but is more advisable to do it there, I am aware.
After I will make your experiments, I plan to take out the sensing circuit module and mount the board on the wall, and make direct simple contact, without the sensing circuit involved. If everything goes to hell, then Im screwed. If everything works fine, then I will proceed to make another sensing circuit, with diferent technology (no field effect transistors). I am thinking on something capacitive like theremin circuit, I was suggested in another forum, not entirely my idea, but I love it. I already looked over those types of circuits and they are a bit complicated, but I put in my mind to try one, even if is a bit too complicated from my original plan.
But first, the experiments.
About multimeters, I have probably 6. One I use it exclusivly as ampmeter. I even managed in my youth to find an osciloscope but is so old and shitty... its a "transistorized osciloscope", is written on it. I dont use it though, i admit.

 

[_q12x_]

@marconi I made a part of your tests.
For 2a and 2b, the voltage is 5V everywhere. Im not sure what voltage are you reffering to measure. Instead, I measured circuit current, that is shown in my PSU (PowerSupplyUnit). When all is Off, is measuring 20mA. When all is On, is 60mA. But when I keep my hand over the sensing circuit to really keep everything ON including relay1, it goes to 100mA, and after I raise my hand, it goes back to 60mA.
2C- disconnect pin5. At this stage, pin1 and pin10 are ON. It should not stay on. Sign that the IC is damaged. Then I thought maybe is interfering with the other modules, so I disconected signal amplifier module, that also automatically disconected S (signal) track to the relays. So I have powered only the IC and the leds.
With pin5 in air, led1 and led10 is on.
But... If I keep with my hand a piece of metal wire on pin 5, unconected to anything, like an antena, all the leds are turned on but very dimmed.
If I connect pin5 to 0v, everything goes off - that is good.
If I connect pin5 to 5V,only pin1 is ON.
I remember in my breadboard experiments, it got me the same results (pin 1 was not litting back then), but pin5 was behaving as right now. I also tested back then with another IC and the same result. I can test it on the breadboard with a new IC and see how it will work, if is the same as now with this one here.
I also observed a slight current through all the leds, with pin5 in air, when I move my hand and body around. It is still interfering with the sensing circuit I guess. Very very strange.

 

[marconi]

I have now watched 5 and 6. Only when I have watched all your video clips will I reply.

I have some 2N7002 making there way to me in the post for me to replicate your sensing circuit ?.

What a wonderful experimenter you are!

 

[_q12x_]

I have now watched 5 and 6. Only when I have watched all your video clips will I reply.

I have some 2N7002 making there way to me in the post for me to replicate your sensing circuit ?.

What a wonderful experimenter you are!

I am very pleased you like it, really, but im a bit... sick of it. So many failures, one after another, literally. Please read my last reply, I put some modifications in it. My biggest problem is that I used the cardboard, and that is gathering some elecrostatic charge on it, i am aware, but i trade it for the maneuvrability and manufacturing ease I can achieve with it. Also very fast experimentation as you already are fascinated by it. Heh. It works for a large majority of circuits, but with this kind of sensing circuits, i suppose I push the limits with it. Eh well, I tried, right?

 

[_q12x_]

I am not allowed to edit my previous posts? What an imbecility.
I just tested on the breadboard the same circuit for LM3914. And I got the exact same results as with my mounted IC, except the led1 and 10 are staying off when pin5 is in air. That is the only fault I have on my board, and I bet it is some sort of interference for those leds/pins.
Pin5 on 0V, nothing happens, all leds are off.
Pin5 on 5V, again, nothing happens, all leds are off.
But, when pin5 is in air, and touch it with my hand, some leds are on, but barely, very dim.

 

[marconi]

I cannot spend much more time tonight because I am starting to cook. I would appreciate it very much if you did what I asked in my post from first thing this morning in order to establish which sub-systems do indeed function as desired. I suggested we first checked that everything from pin 5 to of LM3914 to the relay which switched the room lamp was operating as you wanted it to. If it does then we concentrate on the sensing circuit.

But it may well be that the sub-systems I have asked you to check are also subject to interference or disturbances which disrupts their reliable function.

To give you some idea of one of my lines of investigation you have 50 leds each of which consumes between 10 and 20mA say or in total between 0.5 and 1 Amp. The PURE power supply you showed in one of your YouTube clips outputs 5.5V and its rated output current is 1A. What current is required to operate the two relays which is extra to that for the leds? How well regulated or stable is the pure ‘s voltage output as the current supplied approaches its rated value - at the moment neither you or I know. Why does the voltage output of the pure matter? Because it may be affecting the operation of the sensing circuit.............

 

[_q12x_]

I've updated the original sketch circuit. I discovered a little error there so I redrawn it all, I had it in plan to do it, so now I did it. The error was those 2 resistors how they linked to the pins. Now is corrected and is exactly as in my real circuit. If you want to make it like mine.

You can check it here: Q20201219 Led Wings Projekt Circuit by q12a on DeviantArt - https://www.deviantart.com/q12a/art/Q20201219-Led-Wings-Projekt-Circuit-864540519 Is the same link as before but I changed the image with this updated version.

 

[_q12x_]

another update:
I made a test for the LM3914, then I made a new test on the workbench and on the wall.
I made a manual switching module with a pot and is working fine.
I was afraid of further interference on the wall, but is normal now with the pot.
I am curious what other sensing modules you can think I should try.
Please enumerate all that you have in mind. I have already mentioned myself a few, in the movie. I don't care for originality but I care for quantity this time. So, go nuts.
Warning, this is a lengthy movie, 23m.

 

[marconi]

Buna dimineata. Greetings from London. Your youTube clip was very clear and confirms all is well when the sensing circuit is disconnected - but I await confirmation that it continues to work 'perfectly' when you remove the metal back-plate - an important check.

You have also confirmed your circuit only draws about 60mA. Does this figure include the current for the two relays? Perhaps you could just tell me the resistance of the coils of these relays and I will work out how much current they draw?

When pin 5 of the LM3914 is not connected to anything it will be at an indeterminate or floating potential with respect to ground - or in other words a random voltage - because there are leakage currents to pin 5 from within the integrated circuit. In electronic circuits one must ensure that input pins are never left floating because such an electrical input is random and will affect how the circuit works. We connect them to 0V or 5V.(VDD/VCC).

LED1 is so bright compared to LEDs 2 to 10 because the LED current is set by resistor R1 and R2 at pin 7 - see figure 1 of the datasheet which says the LED current is 12.5/R1. Pin 1 only has one LED connected to it whereas the others have three LEDs; thus LEDs 2-10 have a third of the current flowing through them of LED1. We can adjust the brightness of LED1 to match that to LEDs 2-10 by adding a suitable resistor in series with it - you can work out what resistance value is required or I can help you with that.

https://www.ti.com/lit/ds/symlink/lm3914.pdf

I must express some mild irritation with you. I have asked several times if you would check that the leads of the MOSFET 2N7002 are actually connected correctly in the sensing circuit. It should be connected as in my attached diagram. If it is wired in wrongly that could explain why in one of your youtube clips the potentiometer had no effect on the performance of the sensor circuit.

I will construct your sensing circuit to see how it performs. We can work together to see if we can make it work reliably. If we cannot I have a sensor idea which uses infra red reflection of the hand. My components for your sensor and mine were ordered last Saturday so they should arrive soon.

Regards

Marconi

 

[_q12x_]

Buna dimineata de asemeni. Your romanian is perfect. Good morning from Romania as well. I didn't slept all night, and now im a bit tired.
I am happy you watched that last video and seen the updates so far.
I already explained the relay part:
"When all is Off, is measuring 20mA. When all is On, is 60mA. But when I keep my hand over the sensing circuit to really keep everything ON including relay1, it goes to 100mA, and after I raise my hand, it goes back to 60mA."
I also have the data about the relays, no need for calculations. Works at 5V, draws 30-40mA, and coil resistance is 128R. But in my wings circuit they draw around 30mA. Im not sure why... probably they are limited by the transistors in the relay driver circuit(the little ones with orange and blue leds on them). Is my best guess.

In electronic circuits one must ensure that input pins are never left floating because such an electrical input is random and will affect how the circuit works. We connect them to 0V or 5V.(VDD/VCC).

That is a very interesting piece of information. It is true for PIC's as well? where you have many inputs/outputs pins? The effect is only visible when I touch pin5 on lm3914, and not when is free "in the air' as I call it. But I get your point, to avoid stupid contacts of any kinds, you link it to a rail. Im not sure is a general truth, but it might be fine for many IC's.

Led 1 and 10 are the least of my concerns at this point. They will be dealt with in the very end. As you probably feel me and observed me, I dont like to do simple things, but the complex ones that I am attracted. So, in my mind, I must clear the general fog and then smell the flowers.

Yes 2n7002 is mounted correctly. I pay special attention and double check when I mount my transistors. Im also very careful for a very simple reason: I don't like to make the circuit again from scratch. So im careful from the start.

I must also share this old sketch of mine:

It means the area of effect of the sensor, how I imagine it should work. That is a crude representation, but it tells the idea well. Of course I want gradual opening of the leds, and also a considerable distance. Ideally the distance to be customized. That is done from the antena alone, from my discoveries so far, with this sensing circuit in particular.
As I said in the movie, I will use IR for a remote control. So I will not interfere it with my sensor. Or should I? If I am making an IR sensing sensor? But as how much -------- I got from this sensing circuit, the IR one should be easy in comparison. I already have a very interesting module I will most probably use. At least I will test it first then I will consider to use. We'll see. I'll wait for your ideas first.
Thank you for your reply. Have a nice day, today.

 

[marconi]

The reason why you have an increasingly small distance between illumination of the LEDs as the hand approaches the sensor is that the sensor has a variation in voltage output (V5) with d as I have shown in my first diagram. However, the LM3914 has a linear relationship between V5 and LED illumination interval because all the voltage steps along the resistor ladder (the 3 resistors R across the 3Volts Zener diode) to the comparators (second image) are the same - 1V in my example.

I could not buy LM3914 ics so I have bought discrete comparator chips which means I can adjust the voltages to each of them to correct for the Voltage/distance output of the sensor circuit to achieve the 'customisation' of wing illumination you mentioned in one of your earlier youtube clips.

 

[_q12x_]

What opamp are you using for your comparator? I have myself a bunch of uA741 in my stock. Unfortunatly I dont have the newest models with rail to rail options. I may try to get in sinc with your tests, using my opamp, if you also have uA741. i'm also curious how you will use it with only +5v and 0V. Usually an opamp uses +5V,0V and -5V.

 

[marconi]

https://www.ti.com/lit/ds/symlink/lm339.pdf?ts=1611642239603&ref_url=https%3A%2F%2Fwww.google.com%2F

I will look in my drawers to see if I have some 741s too so we can use the same opamps.

 

[marconi]

Buna seara la un sicriu roman! Just a quick message - because as usual I am cooking and sitting down with my wife for an evening in front of the television - my electronic components have arrived! I will start to construct your sensing circuit tomorrow morning.

I think we should add a peak detector and low pass filter between the sensing circuit and pin 5 of the LM3914. Something like the circuit I have sketched in the attachment. Most of the 'reliable' pick up by the antenna of of signals from the hand will be due to the mains wiring since it is energised all the time, so a low pass filter which reduces other signals which are picked up beyond 50/60Hz (what is Romanian mains frequency?) will make a difference. No sums done yet by me on component values. You could make a start if you wish. Assume the frequencies beyond 1/2piCR.....

https://www.electronics-tutorials.ws/filter/filter_2.html

 

[marconi]

We will reverse the order of the two circuits I mentioned ie low pass filter and then peak detector.....so that we only find the peak of the 50/60Hz signal. You understand why I have reversed the two circuits?

 

[_q12x_]

Buna seara la un sicriu roman!

Did I offend you in any way so far? Then don't do it to me either. If you dont think im at your level and im just a joke, please dont speak to me and I will also stop writing here. Your intentions are many from what I can see. Why do you call me a romanian coffin ? It is not funny and you deserve plenty of my negative response right now. I will abstain though. Your "familiarity" is starting to become insulting. Please think before you write anything to me. Im not here to dick around. If your romanians friends there are not respecting their compatriots, then that should not be a lesson for you to follow. Usually ignorance is a good remedy for that. I'll give you one more chance to be normal. If you will still continue to "be funny", then I will have to say goodby to individuals like you.
Now... to respond to your question, I am not that familiar with low pass filters or peak detectors. I never use them or feel the use of them.