First test by hand looks very good.
- 0V ~ 0.8V converts to ~ 5.0V (Vcc = 5.06V)
- 3V ~3.3V converts to ~ 0.05V
First test by hand looks very good.
I input DS3231 32KHz signal to HC14 2A input, and found 2Y output OK. Next step is use Rpi GPIO pin17 to input to HC14 pin 1A, and use pint 1Y output to control relay.
32KHz is too quick for the relay. So now I used DS3231's programmed 1Hz signal for the HC14 to control the relay. Everything goes well.
1Hz is too slow to display on the scope nicely. So I programmed DS3231 to 1kHz, then use CD4040 to count down to 8Hz, 125mS period. I can now remove Rpi, and used DS3231 + CD4040 + HC14 to simulate converted Rpi GPIO signal for testing relays.
Now I came back to test Rpi. I used GPIO pin 17 to toggle relay at the same frequency of about 8Hz, and used the same HC14 1A/1Y to convert the GPIO signal and apply it to the relay IN. The relay also toggle happily. However, the scope displays a very noisy signal.
Now I am tidying up the messy wiring, hoping that noise might reduce a bit.
I am a bit surprised to find that the Rpi signal is not so dirty now (Yellow waveform is DS3231, blue is Rpi).
Now that I have a reliable standalone relay signal generator, I will take a break on this relay part and come back to study the 200VAC mains control.
The usual instructions these days in the UK are that you should test the RCD (Residual Current Device, AKA Earth Leakage Breaker) every 3 months. Stop all computers that run on the supply, make sure you have light independent of the mains, and push the test button. If it doesn't trip it needs replacing. If it does trip (which will switch everything off), reset and reboot your computers.tlfong01 wrote: One thing I don't understand is the following instruction.
Push the test button before driving appliance?
Does it mean to push the test button (to make sure it works) before using a new appliance? Or after a black out?
Another thing I need to check out is the following.
What is the life of the MCB (10, 20, 30 years, or longer?)
Any MTBF (Mean Time Between Failure)?
1. > ... you should test the RCD every 3 months.
The first version of the schematic is a bit messy. So I did some refactoring, as list below.
Anyway, I started the soldering work of my relay box. It was only when I found it awkward to reach the inner places squeezed with components, then I realized that the box's front and back panel can be easily removed and let your screwdriver and soldering iron comfortably reach the innermost places.
Anodizing can get scratched. You may have unanodized metal bolts or other components penetrating the anodisation.tlfong01 wrote: The answer is that anodized aluminum is like plastic. It is stupid to do any earthing to the box!
Many thanks for your advice and detailed instruction. So it is stupid NOT to earth anodized chassis!.davidcoton wrote: ↑Thu Jun 28, 2018 9:21 amAnodizing can get scratched. You may have unanodized metal bolts or other components penetrating the anodisation.tlfong01 wrote: The answer is that anodized aluminum is like plastic. It is stupid to do any earthing to the box!
It is important that a metal case is earthed, even if anodized.
Without knowing your particular case, I would use self-tapping screws or nuts and bolts to make earth studs.
If the panels and frame are not in good electrical contact, you will need to earth each part.
I guess I have watched too many TV ads on scratch proof things like watches, glasses etc and thought anodization should be a very advanced technology and so make the surface as hard as diamond. I should have mixed up with the graphite thing.tlfong01 wrote: ↑Thu Jun 28, 2018 1:18 pmAnodizing can get scratched. You may have unanodized metal bolts or other components penetrating the anodisation.
Without knowing your particular case, I would use self-tapping screws or nuts and bolts to make earth studs.
If the panels and frame are not in good electrical contact, you will need to earth each part.
Now I have also earthed the main chassis body. The green wire stripped off from a mains cable is a bit too thick and stiff to handle. Next time I might use 22AWG wire instead.
The wire used for earthing must be at least as thick as the line and neutral supply wires.
> 1. The wire used for earthing must be at least as thick as the line and neutral supply wires.davidcoton wrote: ↑Fri Jun 29, 2018 10:15 pmThe wire used for earthing must be at least as thick as the line and neutral supply wires.
Nice wiring, btw.
Now I have earthed main body, front and back panel. The earth wiring squeezed inside the small box is tedious and boring [next time I will use a bigger box.], so I don't feel like doing the remaining top cover. I will now go back to do the more interesting relay related wiring.tlfong01 wrote: ↑Sat Jun 30, 2018 6:45 amdavidcoton wrote: ↑Fri Jun 29, 2018 10:15 pmThe wire used for earthing must be at least as thick as the line and neutral supply wires.
I still have not wired the relays and the mains and transformer output part. But the wiring is getting quite messy, and I forgot which wire goes to where. I have no confidence that no smoke comes out from the Rpi when I flip the 220VAC mains switch.
Thanks a lot for your detailed explanation and advice on earth stud. I only heard of the term "stud" a day ago. I googled and learnt that it is a metal rod with screw thread on both ends (Of course I have seen such thing before, but I did not know its name is "stud"). I guess one stud end is screwed to a heavy metal block buried 6 feet undergound, and the other end to the earthing wires.Mortimer wrote: ↑Sun Jul 01, 2018 11:40 am... required to create a single main earth stud, typically a larger diameter than ...
... tied the incoming mains earth, or ... a separate earth strap to an earth bar ...
... All other panels of the chassis individually connected to this main stud.
... One "No! No!" is to daisy chain the individual metal parts.
... smaller earth stud ...single cable coming from it, going to the main earth stud.
... no daisy chain ... individual panels ... remove ... integrity earthing rest of the chassis
... not permitted to use he chassis as a conductive path for earthing.