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by picture 1536 days ago
> highest we can get away with

Assuming this means highest voltage that's still mostly safe and does not require a whole bunch of insulation, we might be looking at something from 80 to 100 VDC? No idea where I read it from but apparently it takes about that much DC voltage for people to "feel something" when touching conductors with dry skin.

2 comments

The EU safety regs have a cutoff of 50VAC and 75VDC. (Those are only ~5% different in peak voltage.)

Below those levels, you have only general product safety regs to comply with. At/above those and up through all “reasonably household” voltages, you (probably) have to comply with the EU low voltage directive. “Probably” because the LVD itself isn’t law but member states have generally implemented it in their laws.

You break skin at about 50VDC. We could keep ~120V for distribution. There are problems tuning control loops of buck converters dropping more than about 30V (though you can just have multiple buck converters in a row).

Correcting the power factor from 120VAC gives you a boost circuit that gives you 360-400VDC. Some motor control and battery technology standardizes around this voltage. Cars are a big one, but also PFC direct to inverter motor control, which is becoming popular in white goods.

> You break skin at about 50VDC.

What does breaking skin mean in this context? My understanding was that humans largely act like a resistor with some parasitic capacitance and inductance. Wouldn't more voltage equal more current in a mostly linear relation?

You'll feel it shock you. It overcomes the surface resistance of not particularly moist skin and makes your nerves tingle or your muscles twitch.