Plug in chargers - which wire is positive.

[stockers]

I found a neat little trick on the internet that I though might be useful to someone else.
I am using a phone type plug in charger to power an accessory on a layout I am building and i need to know which is positive. It is usually the 'marked' wire - the one with a stripe or design on it - BUT, I want to be sure.
My meter is 'on site' away from home.
All my LEDs are with the meter (LEDs only work one way round so could be used here).

The trick
Take a glass of water, add a teaspoon of salt. Plug in your charger and put the (LOW VOLTAGE ONLY) wires in the glass. The negative will bubble far more than the positive.
Quick, cheap and easy.

 

[PhilP]

But don't do this with the connector of a supply you still want to use! - It will muck-up the connector!

Oh, and don't do it for any length of time..
The 'bubbles' are chlorine gas!!

 

[David1226]

Or leave out the salt and the bubbles will be oxygen from one wire and hydrogen from the other. As a kid I used to put wires from my Tri-ang 12v controller into water and collect the hydrogen in a test tube, to which the application of a lighted taper had a rewarding schoolboyish result. (Grown-up Health & Safety advice now applies to our younger readers, do not try this at home)

David

 

[Walts-Playmobil]

Have you done it with a sliced potato?

 

[Ralphmp]

Or leave out the salt and the bubbles will be oxygen from one wire and hydrogen from the other. As a kid I used to put wires from my Tri-ang 12v controller into water and collect the hydrogen in a test tube, to which the application of a lighted taper had a rewarding schoolboyish result. (Grown-up Health & Safety advice now applies to our younger readers, do not try this at home)

David

Ahh, collecting gas over water - brings back happy memories of chemistry labs and baths .

Time was your ingenuity with your Triang controller would have got you a chuckle and a pat on the back from the teacher, but that was a long time ago.

 

[stockers]

But don't do this with the connector of a supply you still want to use! - It will muck-up the connector!

One just has to ask - how do you know?

 

[PhilP]

One just has to ask - how do you know?

Interpolation. - Legal in most states..

You would get salty water in it, and you know what state battery terminals get in, with a mixture of damp, current, and salts..

 

[stockers]

Now that's just boring. I was expecting some great story of a massive cock up!

 

[PhilP]

Now that's just boring. I was expecting some great story of a massive cock up!

I will tell of large batteries, and someone else's mess later..
Got to vacuum the cats, feed the carpet, and collect SW from the hospital..

 

[pugwash]

Or leave out the salt and the bubbles will be oxygen from one wire and hydrogen from the other. As a kid I used to put wires from my Tri-ang 12v controller into water and collect the hydrogen in a test tube, to which the application of a lighted taper had a rewarding schoolboyish result. (Grown-up Health & Safety advice now applies to our younger readers, do not try this at home)

David

There is a version of this where the hydrogen is collected in a receptacle with a hole in the top immersed in a bubble bath solution. The gas builds up, forms a bubble which rises up and out of the solution, then you ignite the bubble with a taper.

 

[David1226]

There is a version of this where the hydrogen is collected in a receptacle with a hole in the top immersed in a bubble bath solution. The gas builds up, forms a bubble which rises up and out of the solution, then you ignite the bubble with a taper.

There is a variation on this that sometimes happens when I'm in the bath.........

David

 

[Zerogee]

There is a variation on this that sometimes happens when I'm in the bath.........

David

I hope you don't try to ignite it, David....?

Jon.

 

[stockers]

That would be methane then!

 

[pugwash]

If I remember rightly there was an old Jasper Carrot sketch about setting light to certain methane emissions

 

[KeithT]

To find the polarity you could just look at the diagram on the charger. If you can read it without an electron microscope that is! The +&- pare usually marked.

 

[PhilP]

To find the polarity you could just look at the diagram on the charger. If you can read it without an electron microscope that is! The +&- pare usually marked.

Ah, but we are 'little-lads', and much prefer a more empirical method.. Especially if it fizzes and bangs!

 

[p.williams]

Or leave out the salt and the bubbles will be oxygen from one wire and hydrogen from the other. As a kid I used to put wires from my Tri-ang 12v controller into water and collect the hydrogen in a test tube, to which the application of a lighted taper had a rewarding schoolboyish result. (Grown-up Health & Safety advice now applies to our younger readers, do not try this at home)

David

If only a way to do this, cheaply and fast enough- you could power a car -
Damn the laws of physics !