LED on mains voltage?

[AndrewT]

Hi all,
thanks for all your replies.
I took a bit of time to review Peranders & Cpemma replies and I understand what I need to do.
Q, what is a tranzil?
regards Andrew T.

[peranders]

I would have made a schematic for but I was lazy...

A tranzil of transorb is a special zener made for transient protection.

[gmphadte]

remember those rechargeable torches without transformers.

They had .33µF/400VAC cap, and a 1M R in parallel. Next was a bridge made from signal diodes, and battery of two big NiCd button cells connected across + and - and the bridge returns back to mains with a 330 Ohm series resistor.

In this connection, long back, I happened to read that 1µF will give a charging current of 40mA.

From this, I had made a simple mains indicator
A 0.1µF cap 250Vac(x2 type) with 470K resiator in parallel, Two anti-parallel LEDs (A to K, K to A), and a series resistor of 470 ohms returns to mains.

the 470K R discharges the C
two LEDs in parallel as connected takes care of reverse voltages
the 470 ohms R acts as a protection(in case something fails)

all of the above was assembled in a three pin plug.

0.1 µF cap is just because I had one. U can put a bigger value. A little higher current will not affect the LEDs since it's AC half wave per LED.

There was an instance when all the three phase indicating Zero bulbs were lighting, and a three phase motor was not running. Gone to check and found out out that there were only two phases and the third was not wired.

So I suggest for foolproof indication, incase of 3 lines (not phases) wire the indicators across the lines. Values as per line voltage i.e. 415V.

Gajanan Phadte

[hkoetz]

Neon light?

[AndrewT]

Hi Hkoetz,
can you have lateral thinking and hitting it on the head at the same time?
Thanks for that veeery simple solution.
regards to all
Andrew T.

[gmphadte]

Newbies DO NOT ATTMPT THIS.

Sometimes it becomes necessary to have auto phase changeover, especially for the bedroom for having the airconditioner, a fan or whatever running through whichever phase alive. U are not going to get up in the/after midnight and be satisfied looking at the 2 out of three monitor lights glowing.

For this u need two contactors with minimum 1 changeover contact on each.

Phase 1 - Ph(live) is wired to the coil and N/O contact of the same contactor(No.1)
Phase 2 - Ph(live) is wired to the coil and N/O contact of the same contactor(No.2)
Common contact on No.1 is shorted to N/C contact on No.2
Phase 3 Live/Ph is connected to N/C contact on No.1 and the output is taken from the Common contact of No.2.

The contactors SHOULD...
1. have proper mains voltage rating for the coil and contacts
2. have BREAK BEFORE MAKE contacts.
3. have contacts of sufficient current rating and should be overrated for motor starting currents.

If u do not know what happens to the neutral, DO NOT ATTEMPT THIS.
If u have the slightest doubt, U SHOULD NOT ASSEMBLE THIS.

ASSEMBLE AT YOUR OWN RISK


Reminder
Newbies DO NOT ATTEMPT.

Gajanan Phadte

[AndrewT]

Hi gmphadte,
Wow that reply has got me thinking about another project.
But I think it might be safer to leave it to a professional electrician.
I just want to know which parts of the house have lost power. Each time I report a fault the power co. do not believe me & ask me to test in case it is an internal fault. Last time they did not issue a work permit until after a second customer reported the fault some 9 hours after the failure.
regards Andrew T.

[peranders]

I have drawn a schematic of the LED driver but as pointed out: Lethal voltage!!!

I have made a pcb but I have no plans to manufacture any. I drew this schematic because this question pops up now and then. Notice that you can make it simplier but it will be more sensistive against transients and will brake easier.

Forget about the describing text, I have copied the whole section from an another project. I will add more describing text.

http://home.swipnet.se/~w-50719/hifi/mld01

[diyer]

Four important rules for connecting anything to the mains.

use a very well insulated enclosure. Plastic cases are fine if they are sufficiently IP rated. Ordinary cheap plastic boxes will not do.

make your connections as physically strong as possible (soldering won't do), twist and wrap everything first. Insulate every possible connection so that no possible contact can be made (by humans or the cat) with the wiring even if the box were exposed.

Ensure that you will never wire your other phases together even by accident.

A few words about the LED mounting....

If you're using a Chrome metal LED mount, a plastic enclosure will NOT do. You will have to then use a metal box, and provide an unmovable connection to earth for safety. If the LED fails, there is possibility that the metal holder could become live at mains, and you will not enjoy touching this whilst standing in your pyjamas on a stone floor at 2am.

Using a plastic mount invites the possibility of the LED being pushed inside the box, rendering any wiring exposed. Again ensure all connections are as short as possible, and well insulated.

I would never advocate that any novice builder should connect or make circuits that directly connect to mains potentials. I pray that you're lucky, have a change of heart, or use an isolation transformer/step-down or a better arrangement than the 'capacitance dropper' which is no better than DJ Sound to light TRIAC controllers - cheap, cheezy, and one touch is fatal!

Switch to safety, MAINS KILLS

[paulb]

For that kind of complexity, I'd prefer 3 little transformers, myself. Surplus wallwarts would be cheap.