Which is the +Positive wire?

[Elderberry]

I bought an AC to DC converter to hook up to a bilge pump for our shower. The instructions on the pump give specific instructions on which wire needs to be attached to the positive and which to the negative wires. But I can't tell which is the positive or negative wire on the converter. They are both black.

The converter wires came connected to what I can only explain as a cigarette lighter socket. Looking at how the wires are attached, one is attached to the exact center bottom of the socket, the other to the side of the socket. Might the one in the center be the positive?

Does it really even matter?

Thanks.

[Captain Goddammit]

In a DC application, other than incandescent lights polarity almost always matters.
The wire going to the center terminal traditionally should be positive.
You probably won't hurt your pump if you get it backwards the first time you try it.
When you get it figured out, put some red electric tape on the positive wire. Or at least a bit of masking tape with a "+" written on it.

[Meat Hunter]

Many years ago I was up against the same problem when I was ready to install a new 12v electric bilge pump in my sailboat.

An old salt suggested that I momentarily touch the wires together. If the pump ran backwards, then all that I would need to do would be to reverse the wires. I was luck the first try.

Mind you, that this was way-way before the digital age and there were no little sensitive techi-things to worry about blowing out. It might be different today.

Would using a mult-meter on the power-hot side tell you which is the hot wire? How to correctly use a multi-meter is above my pay grade.

Good luck.

[Captain Goddammit]

Or of course put a meter on it, but I'm assuming you haven't got one lying around or you wouldn't ask.

[Elderberry]

I don't have a meter, but I wouldn't be adverse to buying one. But I don't understand how I would use the meter to differentiate the + from the - wire.

[Ratty]

Multi meters are those things you get for free at harbor fright with a coupon. (Regular price a million bucks of course). they couldn't cost much to buy but I never figured out a use. I do have a friend that loves some of the parts out of them.

[Captain Goddammit]

Elderberry, in your instance you don't really need to buy a meter. Just assume the center terminal is positive. If for some reason it isn't, the pump will try to run backwards, just reverse the wires.

If you do buy one, the test leads will be marked + and -.
If it's a digital meter, when you measure the voltage it will show as a negative voltage if the wires are backwards (there will be a - on the readout ahead of the number).
If it's an old-school analog meter, the needle will move backwards if the wires are hooked up backwards.

[FIGJAM]

Look closely at the black wires.

Does one of them have a tiny ridge running the length of the wire?

That one is positive.

[Elderberry]

Thanks guys. Great info.

Figjam, one of the wires does have a slight ridge going the entire length of the wire. Of course, it's the one attached to the outside of the plug--the one we were guessing would be the negative wire.

I'm just going to have to experiment. I was afraid I might burn the pump out, but I've been reassured by the responses here that won't happen for a quick test.

[FIGJAM]

Fuck I'm Good Just Not Perfect!!!

[Token]

You put each wire on the oposite sides of your tongue.

The + side will hurt less.

Or just get a multimeter. Good investment.

[BBadger]

Usually black is ground, and the other wire is +V, but don't rely on that. Someone may have rigged it up wrong, using a different standard, have no black wires (orange and blue?!), or you may not even have the right wires (sensors?). Though different than DC, on AC wiring, black is often "hot" and white is neutral -- but even those may have been wired wrong by someone who didn't follow standards.

Multi-meters are cheap and always handy. Buy one and throw it in the toolbox. Even the cheap-ass ones at Harbor Freight will be decent for voltage measurement. Having one with an audible continuity checker is handy too, if you want to see what might be accidentally connected.

For your pump, being a motor I'm guessing that the worst that will happen with reverse-polarity is that the pump motor will spin backwards. That's probably not a good thing if you're pumping bilge water.

[graidawg]

This is what happens when eplayans get together, we ask embarrassing questions without shame.for my party have no idea what a bi,ge pump. Oops like

[Elderberry]

I know the proper polarity on the pump side as the wires are clearly marked. It's the converter that has two black wires.

[BBadger]

Just your luck. I've got a cigarette lighter attachment right here. Does it look like this?





If so, the center is the red (+) tap; black is the (-) tap. Maybe you can get a cigarette lighter connector (like this) for your pump so that you can quickly connect it to your converter.

[Elderberry]

It looks almost exactly like that, except both wires are black. We were guessing center wire was +. Never thought of ordering the male end, was just going to splice them together. Just ordered it. Another good idea!!!

[Captain Goddammit]

You can also just drop by your local auto parts store, they will probably have that plug. WakMart might even have it.

[MikeGyver]

Seems like its been figured out but I am also a advocate of buying a multimeter, they are daunting at first but extremely useful once you figure out what it can do.

[Canoe]

Multi-meter for sure.

• You never know if they're going by 'ridge' is positive or 'ridge' is ground.
• Then for VDC there's black is ground or white is ground.
  At least when it's intentional. Usually.
• If they're using up whatever is in stock in the shop, or a spool they got on special, or they think they're being tricky/propitiatory - all colour bets are off.
• Or VAC with black is live and white is neutral, or black & red are live with white still neutral, or it's just black and red and red should be live but sometimes red is wired as ground to let you know this is something special... when can be rather special if you're relying upon red meaning live.
• And red with a narrow or thick black line can be ground too, sometimes, maybe.
• Or for either VDC or VAC someone decides that since electrons are negative the actual flow is backwards so they wire it with reversed colours.
• Or a board is from China and they've made the board with a positive-ground circuit/components but with a negative ground interface.
  Or maybe it's not a negative ground interface.
  Maybe there's multiple interfaces: positive-ground interface to connect to sister-boards and a negative-ground interface for connecting with the world.
  Try tracing your first one of those. There's a definite wtf moment.

So, Multi-Meter.

And for line mains VAC, get a non-contact live detector.
You don't know if they're switching the live or the neutral, so if you're relying upon the switch instead of the fuse/breaker box/panel...

[Elderberry]

Muti-Meter should be here tomorrow!

[some seeing eye]

有线向后!

The multimeter does open a world of possibilities! Just double check it is on the right scale before connecting.

[Canoe]

Many are auto-ranging now.
Except mine doesn't auto-range current. uA, mA and 10A

[Molotov]

I purchased a China made 12 volt color changing LED spotlight. The power leads were blue and brown. Logic might tell you the blue (sky) is positive and the brown (earth) is negative. But ignore logic. It will get you hurt and your electronics fried. I was finally able to contact the seller and it was the complete opposite of my concept.

Brown was positive and blue was negative.

The metal light housing is not grounded-no big deal in 12 volt, and in a way it's good-prevents accidental short circuits if it contacts a vehicle or other grounded metal object.

[Canoe]

I purchased a China made ... The power leads were blue and brown. Logic might tell you the blue (sky) is positive and the brown (earth) is negative. Brown was positive and blue was negative...

And the next batch will have _____

[some seeing eye]

There is an electronics YouTube which sometimes does teardowns. They found a Chinese LED lamp where the exposed front metal housing/heat sink was the return path for all the individual LEDs and directly connected to one of the 110v socket electrodes. Do not touch!! (That brown and blue story is pretty funny!)

[rmc50]

The wire that connects to the center of the socket will be the positive. Mark that wire before you cut it free.

What is the current rating for the converter? For the pump?

I would not be surprised if your setup fails to work for you, however. Motors in general, and pumps especially can require a LOT of current to get the motor to start turning. The amperage rating on the pump/motor would be for continuous use, ignoring the initial surge current.

The 110AC to 12VDC converter will have a hard limit on how much current it can supply. When the pump draws more than that, what will happen will depend on the design of the converter. It might continue to put out its maximum current (Current Limiting), allowing the voltage to drop. If this is enough to get the pump started it might be okay.

The converter might sense the overload and simply shut down. This will protect the converter from damage, but the pump won't work.

The converted might not have any protection, and the overload will cause circuits to overheat. The pump might start and it will be okay, or the converter might burn up and be dead. It might work a few times and then fail in the heat of the playa.


Rod

[Elderberry]

Well, that's encouraging.

Actually, it's a bilge pump made to work with that voltage, and the parts have been bought together on Amazon so it's been tried and tested by others. I tested it as soon as I figured out which was the hot wire and all works as expected.

We also have another 110V marine pump that has powered our hot water shower for the last 5 burns. The purpose of this new pump is to pull the water from the shower pan. Originally, we had the shower floor raised and the water drained out onto the evap pond via gravity.

Now, everything is on the ground, easier to get into and out of, and we can pump the water up into a large barrel that United Site Services can suck away every couple of days.

The yurt is air conditioned, so I don't see heat being any factor.