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Mini TS100 soldering iron and current leakage

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MosherIV:

--- Quote ---But inductive AC ripple wouldn't create 115VDC potential to earth, would it?
--- End quote ---

--- Quote ---Also, since it runs off DC, perhaps the designers assume that the DC ground will be grounded to earth
--- End quote ---
The problem here is that the SMPS designers have not grounded the 0V/common so if floats.
The 0V can be pushed up to anything between Earth/0V to the full mains voltage by capacitive coupling.

Yes, grounding the tip will work but do not do it while the SMPS is on.

KL27x:
^Ok, I get that. But does the tip/earth connection of the T12 tip have to be connected to anything?

 I have read that the heater and thermocouple are in series. Is it like a JBC where there is a center tap between the heater and the sensor, making 3 connectors in total? And the tip is in continuity with one of them at all times?  I only count 3 connectors on the T12 tip, and it runs off AC in the Hakko FX950/1, so it means DC control circuit and earth have to be the same, and in direct continuity with the tip? Or is there a fourth connector hidden in the very end of the tip?

I have some T12 tips coming, and I was planning on the tip to be
1. tip/earth
2. heater
3.cathode of thermocouple

And you run the power between 2 and 3. Turn it off and read the voltage between 2 and 3. The resistance of the heater doesn't matter, it just adds a little variable impedance which you are going to prolly swamp anyway with the opamp circuit resistors.

*Also, you are wrong and I am right about the other example of wrapping the tape around the iron and wrapping that in foil?

KL27x:
Ok, I'm betting there is a fourth connector in the base of the tip. It doesn't make any sense for the tip to be in continuity with any of the heating/sensing elements.

If this is the case, all you have to do is disconnect the sheath from DC ground. Problem solved.

bodger:

--- Quote from: KL27x on June 28, 2017, 10:34:00 am ---^But inductive AC ripple wouldn't create 115VDC potential to earth, would it?
--- End quote ---

It's 115Vrms AC that I was measuring on the tip, as I understand it the y-cap causes a small current to float at half mains voltage.

3db:
I just did a quick measurement of the resistance between the earth screw and the tip. It's approx 0.9 - 1 ohms.
I used a Fluke 101,so nothing fancy.

3DB.

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