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GeneralRe: USB for Power? Pin
James Curran11-Feb-21 23:28
James Curran11-Feb-21 23:28 
GeneralRe: USB for Power? Pin
glennPattonWork312-Feb-21 0:00
professionalglennPattonWork312-Feb-21 0:00 
GeneralRe: USB for Power? Pin
James Curran12-Feb-21 5:37
James Curran12-Feb-21 5:37 
GeneralRe: USB for Power? Pin
trønderen12-Feb-21 7:23
trønderen12-Feb-21 7:23 
GeneralRe: USB for Power? Pin
ElectronProgrammer12-Feb-21 7:53
ElectronProgrammer12-Feb-21 7:53 
GeneralRe: USB for Power? Pin
trønderen12-Feb-21 9:34
trønderen12-Feb-21 9:34 
GeneralRe: USB for Power? Pin
ElectronProgrammer13-Feb-21 7:59
ElectronProgrammer13-Feb-21 7:59 
GeneralRe: USB for Power? Pin
trønderen13-Feb-21 12:54
trønderen13-Feb-21 12:54 
Sorry for bringing some realism into the panic ... Smile | :)

Voltage loss (hence power dissipation) through a cable is given as dU = (2 * I * l * rho) / A, where I is the current, l is the cable length, rho is a material constant which for copper is 0,0175 Ohm * A/m. A is the cross section of the conductor.

Filling in for I = 2 Amp, l = 4 meter, and A = 4 sqmm gives a voltage loss of (2 * 2A * 4meters * 0.0175 ohm*sqmm/m/) / 4sqmm = 0.07 V, through the maximum spine length in my house.

If, at the very end of a spine, I make ma maximum length rim, using 2.5 sqmm cables, the voltage loss is (2 * 2A * 4meters * 0.0175 ohm*sqmm/m/) / 2.5sqmm, or an additional 0.112 V, for at total voltage loss of 0.182 V. So with a 2A load, I will experience approximately 1.5% voltage loss along the cable. Given the 2A current - about 24 W - more than a third of a watt may be dissipated from my eight meters of cables. Alarm! Look out - Danger! Fire hazard imminent!

Most consumer points do not run from the very end of the spine, and do not have four meter ribs running from the spine. This 4 + 4 meters is an extreme worst case. For most situations, both cable lengths and currents will be (way) lower.

I can understand that there may be people who do not understand the need for power cables to dissipate a third of a watt over eight meters, thereby causing fires. Yet, others may prepare for it, and lay the cables to provide the necessary cooling for effects at this level.

BTW: Norwegian mountain cabins, far away from any 230VAC supply, have for decades had solar panels with battery banks providing 12VDC for light, small fridges, ventilation and other purposes, without converting the 12VDC battery power to 230VAC, but using the 12VDC directly. It would make no sense converting it to 2230VAC only to plug in a 230VAC-to-12VDC to get it back to the power required to drive the light and the cabin style cool box.

(Note to the OP, James Curran: Here you see the kind of arguments you must be prepared for if you decide to go for a low-voltage installation in your house!)
GeneralRe: USB for Power? Pin
ElectronProgrammer15-Feb-21 2:41
ElectronProgrammer15-Feb-21 2:41 
GeneralRe: USB for Power? Pin
trønderen15-Feb-21 4:20
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GeneralRe: USB for Power? Pin
glennPattonWork312-Feb-21 8:08
professionalglennPattonWork312-Feb-21 8:08 
GeneralY'know Pin
Chris Maunder11-Feb-21 6:15
cofounderChris Maunder11-Feb-21 6:15 
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Gary R. Wheeler11-Feb-21 15:31
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