For the last 10 years. I haven’t paid for any car repair other than parts. Because the mechanic shop would have me work on the electrical issues on cars and on the building. So that was a win win for the both of us.

KOT

It's interesting how one's point of view can change one's understanding of a situation. buzz takes the point of view that the wire and its size is in place and must be dealt with. I think the actual point of view is that the loads and the cost of copper determine the fuse ratings and the sizes of the wires.


Well, yes, but it also protects the source of the power. You want to keep a power amp from blowing at current levels much below those that will cause a fire.


I don't think so. Thicker wire costs more than thinner wire. Since wire costs money, the wire is sized according to the amount of current it should be carrying -- it's not that the wires are some random size and the fuse is there to protect them. The fuse is rated to allow more than enough current for the load.


The wire is sized such that it can always provide the current needed by the load while not getting hot. This issue is way below burning level.


No, the wire is sized to deliver the current needed by the load, and the fuse is chosen to blow before the load will blow (though we know the jokes about transistors etc being devices that blow in order to protect fuses!).


Exactly.

Every car I've ever seen has two wires coming off the positive. One is very thick and goes directly to the starter solenoid. The other is what I'd call the primary wire, and it goes to a block of fuses. Yes, it's not fused at the battery, but each branch of it is fused.

I own a forklift, but it's 12V battery and Propane engine.

I guess it's time to cater to your car's needs, rather than your own.

Thank you guys for all the input!

Here's another easy one for you electrical guys. Obviously 120VAC is standard for an outlet. I don't know how much damage having more than that could do to various equipment, though. I get 122 at the outlets in my house normally, fine no big deal. But....

Would constant exposure to 125 VAC for a transformer (or wall wart, or power supply, whatever you want to call it) potentially be too much for one that was supposed to be outputting 5VDC? Just something I ran into today, (on the second transformer, I decided to measure the outlet and it was 125 VAC +)and wondering if it was a power surge that may have killed them, or if it was long term exposure to voltage that may have been a little too high.

Thanks!

“120” is the “nominal” voltage. The actual voltage will vary quite a lot. Although it makes me a little nervous, 10% variation is not earth shattering. If you watch closely, you’ll notice that voltage varies throughout the day and possibly from season to season. While I was in college I lived in an area with old wiring that was maxed out with respect to load. In the summertime they would jack the voltage up to almost 130V in an effort to accommodate the air conditioning. (Many motors want to run at a constant speed and they’ll draw more current when the voltage is low — current heats wires and the electric company can’t bill for heated wires in the street)

An annoying aspect of this high voltage was that incandescent lights are usually rated for 120V and the over voltage has a very significant impact on bulb life. I went out of my way to purchase 130V bulbs.

Another interesting lesson for you is to measure the voltage on a outlet shared with a heavy load, such as a heater or vacuum cleaner. Measure with the appliance ON and OFF. Now imagine what can happen if your house is at the other end of the block from the local transformer. As all the other houses turn ON lights and appliances, your voltage will sag.

With respect to regulated power supplies, such as your 5V units. If you look closely, you’ll probably notice that they are rated from 120-240V and some might be rated as low as 100V. These units will run slightly warmer at higher voltages. 122 or 125V for these units is not a big deal.

My college job was at a sound company that shared facilities with a Nagra repair company (look them up -- fascinating stuff). The accidentally found that when they used a strobe light to check speed, a perfectly set tape recorder would indicate that its speed was high in the morning and low at night. They finally rationalized* that the generating stations must run slightly slowly in the morning as civilization ramps up for the day, and the generators must run slightly fast in the evening so that, at the end of the day, all the synchronous motors of all the electric clocks would show the correct time.


Once we talked ourselves out of needing perfect color rendition in our audio stores where almost all the product was silver or black, we saved a bunch of money on bulbs and a little money on power by exclusively using 130V bulbs.


Go one step further: your house has voltage coming in from the pole on three wires. We call the center voltage zero as it's our reference wire, so the voltage is called 120-0-120. The vacuum cleaner pulls power from the zero and one of the 120 wires. But when one side of the line sags, there's nothing to make the other part sag; even worse, when one side sags, the transformer continues to supply 240 volts from outer wire to outer wire, so the other "120" volt half goes UP in voltage! ALWAYS be aware that if power is sagging where it should be 120 Volts, you should expect concomitant overvoltage on the other phase of the power.


buzz is talking about switching supplies, which are great at not caring what the voltage is. They adjust their outputs so the output is the same, no matter what the input.

A block-type plug-in wall wart is more than likely a transformer and simple conversion to DC. These will likely put up with 125 volts, even 130 volts, for a long time, but as they're given more voltage, they heat more, so less current draw (which also heats them) can be expected.


*by rationalized, I mean they convinced themselves that they had found the answer, even though they didn't ask anyone who might know, nor had done any tests to prove anything.

Yes, power line frequency varies. see: [Link: en.wikipedia.org]

Some quickie data on incandescent bulb life: [Link: en.wikipedia.org]

And a more complete discussion: [Link: en.wikipedia.org]