4 ms·

> But then there is the tradeoff of the popularity and availability of 12VDC devices due to RV/Boating. Which is exactly why we need to get away from those 12V

by dhdc 5y ago

> But then there is the tradeoff of the popularity and availability of 12VDC devices due to RV/Boating. Which is exactly why we need to get away from those 12V old garbages asap. 12V is so bloody wasteful, in terms of both wasted power and wasted conductor material. The only reason why its still around is people got used to it and don't wanna change.

zw123456 5y ago
what is the optimal voltage based on empirical data ?
- picture 5y 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.
  - sokoloff 5y ago
    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.
  - R0b0t1 5y ago
    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.
    - picture 5y ago
      > 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?
      - R0b0t1 4y ago
        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.
- The_Double 5y ago
  A lot of industry like datacenters and vehicles are moving to 48V. 48V is right on the limit of what is considered low-voltage and therefor doesn't have special safety requirements. And because it's a multiple of 12V, it can work well with old equipment by putting exiting supplies or batteries in series, and using very efficient constant-ratio down-converters. see for instance: https://www.vicorpower.com/documents/whitepapers/wp-boosting-pdn-performance-simpler-bus-converter.pdf https://www.vicorpower.com/documents/whitepapers/wp-boosting...

by dhdc 5y ago

zw123456 5y ago

what is the optimal voltage based on empirical data ?

picture 5y 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.
- sokoloff 5y ago
  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.
- R0b0t1 5y ago
  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.
  - picture 5y ago
    > 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?
    - R0b0t1 4y ago
      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.
The_Double 5y ago
A lot of industry like datacenters and vehicles are moving to 48V. 48V is right on the limit of what is considered low-voltage and therefor doesn't have special safety requirements. And because it's a multiple of 12V, it can work well with old equipment by putting exiting supplies or batteries in series, and using very efficient constant-ratio down-converters. see for instance: https://www.vicorpower.com/documents/whitepapers/wp-boosting-pdn-performance-simpler-bus-converter.pdf https://www.vicorpower.com/documents/whitepapers/wp-boosting...