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 !

 

[marconi]

I have ordered some 940nm ir LEDs and photodiodes to make some longer wavelength arrays. So far they have been 850nm ones.

I found this scientific paper to learn more about how human skin reflects and absorbs ir rays. Do not worry about the mathematics just read the words if you are interested.

https://www.osapublishing.org/Direc...4-35-10559.pdf?da=1&id=333549&seq=0&mobile=no

 

[_q12x_]

I have ordered some 940nm ir LEDs and photodiodes to make some longer wavelength arrays. So far they have been 850nm ones.

I found this scientific paper to learn more about how human skin reflects and absorbs ir rays. Do not worry about the mathematics just read the words if you are interested.

https://www.osapublishing.org/Direc...4-35-10559.pdf?da=1&id=333549&seq=0&mobile=no

your link is giving me an error:

Always check the links you send ,if they first work in your side.

 

[marconi]

These are the items my links should have shown you.

My ir sensor has the predictable problem of variable ambient ir radiation pick up. Worse of course during the day. One of the reasons for trying 950nm ir is it less reflective off skin which may reduce pick up of ambient ir reflected off it and thereby emphasise the ir from the led illuminators. We will see.

I also thought I could pulse the illuminators which would create pulsed reflections I can build a circuit to distinguish from the ambient ones. As ever work in progress and most interesting.

I bought a sounder too to tick.

 

[_q12x_]

I was waiting for you to send me back that link that didn't work. When you send the link, make a test if its working in your side, immediately after you send the message. Then you can press the "edit" to change the link if is still not working.
Officially they are called buzzers and not sounders. Is a keyword that works in google and on ebay or any other online market. I am using the correct one because I learned to respect these keywords over the years and they just work. So get in habit to use them correctly as well. Its how I do things and it helped me.
I already find the solution for IR problem. You need much more bigger wattage IR leds to be able to reflect from your skin or any other opaque material. Just try it my way and we (both) will see if is true or not. I didnt test it but I think it might work. THese little 5mm are good if the receiver and emiter leds are pointing at each other, and not reflected like you are trying there.

 

[_q12x_]

I made a "quick" (10min) movie describing and showing the problem with Rx Data pin (its output).

 

[marconi]

I will take a look later but more likely tomorrow morning when I get up.

Could you clarify something for me please? Have you actually done a 1W IR led shining on your hand and then reflected back to a photodiode? I know you did a beam interrupter system using visible light LED and PD. If you did how did you arrange the IR led and photodiode at one place? Also please tell me what wavelength you used. Such experience would save me some effort and time.

Regards M

 

[_q12x_]

I will take a look later but more likely tomorrow morning when I get up.

Could you clarify something for me please? Have you actually done a 1W IR led shining on your hand and then reflected back to a photodiode? I know you did a beam interrupter system using visible light LED and PD. If you did how did you arrange the IR led and photodiode at one place? Also please tell me what wavelength use used. Such experience would save me some effort and time.

Regards M

It was a theory I had some couple of reply ago. But you didnt read all I wrote before. I did not made any attempt before. It just crossed my mind (while discussing it with you here in forum) to use 1W IR led and also there are 100W IR leds as well and it is a good idea to try it.

 

[marconi]

It was a theory I had some couple of reply ago. But you didnt read all I wrote before. I did not made any attempt before. It just crossed my mind (while discussing it with you here in forum) to use 1W IR led and also there are 100W IR leds as well and it is a good idea to try it.

How do you know I did not? In your #244 you wrote 'I already find the solution for IR problem.' You have not then found the solution: you have an idea on what the solution might be.

 

[marconi]

[Remote Control Transmitter and Batteries Built in one day]
Here is 1 day of very hard work and very good results.
I apologize for a very long movie 21min.
But you will see in it how it behaves on the breadboard and how is in my hand. Also some photos of how was built, and also my "3d printing" method I used. I hope I keep you interested in it to actually watch it.

Thank you for your help so far.

I refer you back to my #231, 232, 238 and 240.

The data input to the Tx and the data output of the Rx chips are two state signals - logic signals. Being logic signals they have a specification for what voltage range represents a 0 and what voltage range represents a 1. To help you further - the data input and output can be connected to TTL or CMOS logic gates. The currents which flow during a 0 or a 1 between gates are small - mA or lower. This makes them vulnerable to pick up unless care is taken.

Logic gates have rules on how they are to be used. For example inputs should not be left floating and outputs can only sink or source so much current before the voltage goes outside the range for a 0 or 1.

If you connect one electronic circuit to a point in an another electronic circuit operating with small currents you will inevitably have some impact on the operation of either or both circuits - sometimes it will not be noticeable and other times it will to the point of changing one, the other or both circuit's operation. When this happens the signal passing across the interface between the two circuits will not be what you thought it would be. To prevent one circuit disturbing another interfaces have to be carefully studied and often a buffer circuit designed and introduced between them. I mentioned this earlier.

When a mechanical switch or finger as you are using is used to generate a voltage change to represent a 0 or 1 its output is often unsuitable to be directly connected to a logic gate input because of contact bounce.

Finally - for now - data circuitry can be as vulnerable to interference and noise as analogue unless care is taken to have robust voltage levels representing logic states and transitions between states are very quick and without any bouncing between states. The voltages representing a 0 or 1 should not be near the upper threshold for 0 or lower threshold for 1 to avoid interference and noise 'pushing them into the separation band voltage ranges when a 0 or a 1 is undecidable by the logic electronics a situation which will produce random 0s or 1s.

I suggest you use your oscilloscope and examine the nature of the signals you are creating eg: at the data input to the Tx and at the ouput of the Rx. You will then have an image in your mind of their waveform and suitability and what is required to clean them up and make them robust and thence reliable for data transfer without error.

 

[_q12x_]

I refer you back to my #231, 232, 238 and 240.

The data input to the Tx and the data output of the Rx chips are two state signals - logic signals. Being logic signals they have a specification for what voltage range represents a 0 and what voltage range represents a 1. To help you further - the data input and output can be connected to TTL or CMOS logic gates. The currents which flow during a 0 or a 1 between gates are small - mA or lower. This makes them vulnerable to pick up unless care is taken.

Logic gates have rules on how they are to be used. For example inputs should not be left floating and outputs can only sink or source so much current before the voltage goes outside the range for a 0 or 1.

If you connect one electronic circuit to a point in an another electronic circuit operating with small currents you will inevitably have some impact on the operation of either or both circuits - sometimes it will not be noticeable and other times it will to the point of changing one, the other or both circuit's operation. When this happens the signal passing across the interface between the two circuits will not be what you thought it would be. To prevent one circuit disturbing another interfaces have to be carefully studied and often a buffer circuit designed and introduced between them. I mentioned this earlier.

When a mechanical switch or finger as you are using is used to generate a voltage change to represent a 0 or 1 its output is often unsuitable to be directly connected to a logic gate input because of contact bounce.

Finally - for now - data circuitry can be as vulnerable to interference and noise as analogue unless care is taken to have robust voltage levels representing logic states and transitions between states are very quick and without any bouncing between states. The voltages representing a 0 or 1 should not be near the upper threshold for 0 or lower threshold for 1 to avoid interference and noise 'pushing them into the separation band voltage ranges when a 0 or a 1 is undecidable by the logic electronics a situation which will produce random 0s or 1s.

I suggest you use your oscilloscope and examine the nature of the signals you are creating eg: at the data input to the Tx and at the ouput of the Rx. You will then have an image in your mind of their waveform and suitability and what is required to clean them up and make them robust and thence reliable for data transfer without error

Very good explanation and solution making ! I am exactly at this stage right now, modifying the output Rx with a new circuit (like a buffer) to drive normally the wing leds. Big problems so far, but I will take care of them, 1by1. Hopefully. Thank you for your very nice discussion here. Much appreciated.

 

[_q12x_]

today i build the oscilator for the Transmitter Tx.

 

[marconi]

I will be interested to hear about your progress.


I have had a break from my version. Here in the UK we have the 6 Nations Rugby competition this weekend ( - a deserved victory to Wales against England yesterday) the weather has been so good I have spent time outside instead of in my shed.

I have been thinking (mulling) over whether to experiment with a 940nm array next or to pulse at 10kHz (say) my current 850nm arrays four leds and filter the IR photodiodes output of ambient background and active illumination. So, I have been doodling with circuitry for the pulsed approach next.

I hope you are well and happy.

Best wishes

Marconi

 

[_q12x_]

Another failure but it teaches me something important! Dont mess with the interferences because they will mess you up !!! I got messed up by interferences so I quit it, this was the conclusion after all the experimentation with the RF boards.
All this experimentation I did with a very good friend from america , and very patient, whom we were talking live through an audio live conference and he guided my --- to do all the experimentation needed, but it failed because I have too much interference in my area where I live. ANd i trust him very much because i can't find any other explanations for the weirdness I got, especially after mounting a long wire antena.
I am back to the alternative, or plan B of the remote, using IR, and now for good.
We will try to make a Tx and Rx for the IR remote. It will involve an opamp (uA741) that I only have.
My request from you, is simple. Do you know how to make such a Tx and Rx?
I never in my life built such things. THis is my first time. And is having its up's and down's but this is experience and I like it.
I will start thinking to something myself.
My friend will come back to me after 2 days from now. Because he is having some stuff to make as well.
I am summoning you , mister @marconi to make it in these 2 days.
So only the schematic you have to make.
THe hard part is for me, to actually test it. I'll search on the internet for free circuits for IR remotes and see what I can built by my own.
What an experience with the RF. Phhh.

These are the IR leds and receivers I have, it it helps : https://www.ebay.com/itm/100pcs-3mm-850nm-LEDs-infrared-emitter-and-IR-receiver-diode-50pairs-diodes/323206187341?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

 

[marconi]

I have just watched your latest video. I gather that you have achieved a Tx which will send short pulses of RF to the Rx. The data signal into the Tx pin looks satisfactory. Could you produce a short video for me showing the signal on your 'scope at the Rx data pin and at pin 3 of the Rx's 555 chip please?

I think you may be giving up on RF too soon. If you wish I will spend some time with you trying to iron out the problems. But first I would like to see the signals at the Rx end.

Please let me know if you wish me to help with the RF remote control. If you do could you also draw the circuitry for me at the Tx and Rx?

 

[marconi]

I have studied your last video carefully and if my eye-sight does not deceive me you are using the 555 as a 'sawtooth' voltage waveform generator at pin 2 - the purple one in my attached diagram. There is too a square wave output of the same period from pin 3 - the yellow waveform.

The 555 is kept in the reset state - outputs pin 2 and pin 3 - at 0V when the reset pin 4 is kept at 0V. Upon receipt of a series of data pulses 0-5-0-5-0....V from the Rx data pin, the diode-capacitor network will charge up until pin 4 crosses the threshold to become active high. Then the 555 is no longer ins reset state and oscillations at pin 3 and 2 begin. When the data pulses stop, the capacitor discharges until pin 4 becomes active low and the 555 is once again in the reset state and oscillations stop.

Pressing the button on the remote will then produce a repetitive pulsed output with almost 99% mark to 1% space ratio and a sawtooth waveform of the same period until the remote button is released.

The circuit is not quite correct for interface to your LM3915 pin 5. What you want to happen is a voltage to be input to its pin 5 which is 0V when the remote is not in use. When the button is pressed the pin 5 voltage must grow from 0 to 5V and remain at 5V until the button is released. Upon release of the button the voltage reduces to zero again. See my second diagram.

We can fix this.