On January 21, 2019 at 12:24, Ernie Gilman said...
Re my comment that doubling a wire gives you about the same resistance as a wire three numbers smaller (wire diameter larger, numbers smaller).
I was remembering a similar discussion from some time ago. No, I didn't look and haven't looked for more than a year. But here's what I found upon looking:
My chart says the resistances of these wires are this:
24 gauge, 25.67 ohms per thousand feet
21 gauge, 12.8
18 gauge, 6.385
I claimed that two 24s in parallel have a resistance almost exactly the same as a 21 gauge wire. From the numbers above, two 24s in parallel have a resistance of 25.67/2 = 12.835 ohms per thousand feet.
I said that two of these paralleled pairs of 24s would have a resistance nearly the same as an 18 gauge wire. Two wires of 12.835 ohms in parallel have a resistance of 12.835/2 = 6.4175 ohms per thousand feet.
Those numbers are very very very close, close. Aren't they?
I think you understood me to mean something else. What did you think I was saying?
That's well known- why go into such detail when it's shown in the chart?
Because red herrings swim sideways. What does this have to do with the discussion? I assume you mean connecting two power amps to one load; this will cause interaction between the output stages that would likely damage the amplifiers, so it's not worth thinking about.
You assume too much and here, you assume incorrectly.
Yes, I saw that comment, and I wrote this. Perhaps we should both read everything:
I missed one point -- if one supply is underrated for the job, then yes, a power supply that can do the job will work better. That has nothing to do with robustness. A robust supply might be one that can survive a short circuit, after all, which is not an issue here.
Robust would also mean it can handle high demand without failure, but it doesn't need to be a dead short.
However, Highfig's suggestion of putting a battery there is BY FAR the better idea:
*Trickle charging, even on one 24 GA wire, (I said one wire instead of one pair because all the circuit grounds would be tied together) would be 24 hours per day with no large currents
*the battery would easily always be able to supply several amperes for several minutes, way beyond what's required to pop a solenoid.
Years ago in car audio we experienced the benefits of adding huge capacitors, in that if large enough, they almost behave like batteries. Batteries would be even better here.
The demo I saw in about 1982, around the time stiffening caps began to be used widely for car audio had a cap connected to a light bulb and a battery connected to another, with a voltmeter and ammeter connected to each. The current needed for the bulbs was fairly high and it was a decent demo of peak power demand and how each would supply what was needed in order to maintain output and supply voltage. The battery won, easily. IIRC, three paralleled half Farad caps were needed to match the ability of the battery.
