Do you still have the diodes installed on the Relay 2?

 

I left only 1 diode on relay2, because it was too much voltage drain from both diodes.
Maybe that is the problem?

 

I would remove it.

 

Also the 100uf cap if it's still there

 

I just removed the diode and made a series of tests. It is better now. Boy, you know this circuit better than me now.
Excellent sense you had. Bravo. For the moment is behaving exactly as on the table.
I plan to elongate the antenna to make it sensitive from a bit more distance than it is sensing right now. That alone will bring back some problems I might guess. We will see at that time.

 

@sghioto I brake it again.
I made the test on my workbench. It worked exactly until I changed the antena wire.
I started to change the antena with a larger wire, and I started to get weird behavior. 9'th led is staying lit, no sensing activity whatsoever. Also SCM led is staying lit as well. I took out the 2n7000 and test it with my DMM on diode, and I was getting readings all over it G-S G-D S-D, everywhere. I change it with a new 2N7000, test this new one as well and got readings only from S-D but not on the rest. I solder it and the same weird behavior as before. Im starting to think maybe is the IC gone? Or parts of it gone? It is just impossible to keep it alive too long.
I also replace the 2n3904 from SCM but no difference at all.
Ive checked every connection in SCM and resoldered eveything, again, no difference. An the SCM led is staying lit as well
Everything on the working bench.

 

Did you check the 1N4148 diode in the SCM?
You can check the LM3914 anytime by reconnecting the pot.

 

Did you check the 1N4148 diode in the SCM?
You can check the LM3914 anytime by reconnecting the pot.

Yes, its exactly what I did for LM3914 and it looks fine. And also verified and compared the diode with others the same as it, and it also looks fine. For some very weird reason, the sensing circuit just stopped working. Just because. I suspect the cardboard might be the problem. I have to rethink this specific board, it's too sensitive and I've always know it, not just now. I am thinking some strange humidity might get impregnated in the cardboard due to the snow outside. It's the only reasonable explanation I can think.
I've resoldered every track from it, not that many, every component, again not that many, checked even the resistors if they somehow burned, but all are fine. It just fall dead. Fantastic ! Just to f*ck with my happiness.
Im thinking instead of cardboard, to use some plastic. But is very tricky to heat.
I'll see what I can do and I 'll announce you when is working.

 

I put my DMM (digital multi meter) on 20VAC and the red probe on the grounded wire. Actually, while the probes are in air, not touching anything, DMM reads like 0.1-0.3V by itself. Its an old DMM and I dont trust it completely. Is having some leaks, and I know it has. Is not perfect. Now, when I link the grounded wire with red probe, it jumps to 6.4V while the black probe is in air, in my other hand. When I circle with my black probe directly on the wall, and around the 220 switch hole, it jumps to 7.8 and the closer I get to the hole it reaches 8V.
I noticed that the hole is not cement but an iron tube inserted in the wall, with some holes in it for the wires to pass through it. When I touch this rusty metal case, I get an instant 19.7VAC.
That explains it then.
A friend from another forum put me to take this test, not my idea and I would not had do it myself alone. So my thanks to him.
I might power my entire circuit to this electric field alone, with no transformer at all. hahaha
Who knows, maybe its like that by design... some countermeasure of some kind. Very weird. I know this block is a special one, because is central in the city.

 

I get an instant 19.7VAC.

Put a 10K resistor across the meter leads and see what the reading is.
That 19.7 volts should be zero. The metal pipe or conduit is normally grounded but because it's rusty is probably loosing it's connection.
The ground conductor in the wiring should be connected to the conduit in the wall receptacle.

 

I built another SCM. And now is working fine again.
It might be that the older one was "worked" too much and it started to leak is my beast guess. Especially the cardboard being most probably soaked from my fingers. It is a possibility I think why it got wild by burning 2 transistors and then complete death. RIP old SCM. We will forever remember you.
I made a movie, a bit too long [11min] and really not that important, you can skip it if you like. Basically I talked about these transistors how they got burned, and the new module that I made, Im making this movie, as a proof that is working now when the 0V wire is not connected to the shield. I'ts a possible cause that those sensible transistors got burned. Not completely sure, but is an idea.

 

Newsflash !
I burned another 2 transistors only by switching the antena ! WOW.
SO I have 4 burned 2N7004 now. It is a confirmation that is from the antena.
I think the length of the antena is just overwhelming it's gate.
I think that pot in the circuit might help with this problem. Im thinking to add 2 x 5k on the pads where the diode is; where the pot should be.
Unbelievable. Why now? Why not before when I was switching the antena length like 100 times. It is weirder and weirder. And I did not connected the 0V to the shield this time. So that has no influence.
Maybe some other components failed and is dragging down this module, hyper sensitizing it.
Is the most strangest project and circuit I ever encountered and built.
Im starting to think is a good idea to make a theremin circuit - seriously. Im too tired from this braking all the time. Its too fragile.

 

It just occur to me:
Do you know how can I intimately read this 2N7000? Because as you know already, the osciloscope or DMM are not usable, they interfere and keep the transistor High. A PIC microcontroller ! That will intimately read all this weird behavior. But I dont have prepared for this step, it's too deep for me, I know how but everything is not in order at this time to do it like that. But is probably the best thing. Also range calibration from the pic as well. It's an idea.

 

A challenge:
Draw over my sketch, or make another new sketch, completely from 0, and show me how you would do it.
You have my experience with what is good and bad. Make me your version. Completely different from mine, or similar, I dont care, just make it more stronger and solid and serious than what I did so far.
But make it clear and understandable not enigmatic and romantic that nobody will understand it's functionality.
In other words, if you plan to make it, how would you make it?

 

Most likely cause for damaging the transistor is static electricity when touching the antenna especially this time of year.
The maximum gate voltage on 2N7000 series is only 20 volts.

 

Thank you mister @sghioto !
How can I avoid static electricity ? Grounding myself? Put a conductive wire from my hand wrist to the ground? It is my first thought I have in mind. Or there are other factors, beside me?
I used 2 types of wire and with both got damaged. 1type is the copper enameling thin wire and that is certainly more susceptible to static electricity, because very thin isolation on it; and 2type is solid cable wire used in telephony some years ago, not copper but nickeled steel but it has a good plastic isolation over it. It is in fact the same dark-blue wire that is showing up in my little antenna in my movies. SO I took another a bit longer type2 wire, and the transistor got burned even with that.
I know I used type1 wire, and very long one, like 30cm (11.8 inch) or so and it worked fine, when I was testing the range, a couple of months ago.
All this wiring changing was done on my table, not on the wall.
Is it the pure length of the wire that is gathering static electricity or me touching the metal that is helping it gather static electricity?

 

Touching the metal most likely.
Grounding yourself as you described above with a wrist strap is common procedure.

 

How can I continue this project now?

 

How can I continue this project now?

Do you mean as far as using a different type of sensor?
If so I would research ultrasonic positioning circuits especially if you want to get any decent range.

 

Do you mean as far as using a different type of sensor?
If so I would research ultrasonic positioning circuits especially if you want to get any decent range.

I am staying away from any type of sound, inaudible or audible , in my sleeping and working room. I am a bit paranoic about sounds. I understand all your arguments but, no sound.
I say yes to light, magnetic or electric fields, capacitive and what else is there?