Positive polarity indicator

[sprocker]

Our P40 has a polarity indicator (Polarity correct when lit) on the main switch panel, which has a burnt out bulb. I want to replace this unit.

Am I correct in assuming this is 240v polarity?

 

[penberth3]

AC doesn't have "polarity".

 

[VicS]

Our P40 has a polarity indicator (Polarity correct when lit) on the main switch panel, which has a burnt out bulb. I want to replace this unit.

Am I correct in assuming this is 240v polarity?

ITYWF that it is a 240volt neon ( a neon indicator plus resistor)

You should find something similar from RS component,s or your usual electronic components supplier, for under a quid.

AC or not everybody knows it as a polarity indicator !

 

[halcyon]

AC doesn't have "polarity".

Supply live and neutral crossed, normally neon connected neutral to earth, illuminating if crossed giving a live neutral and light on.

OP's problem looks like a standard neon indicator, as said go to local RS with it.

Brian

 

[JerryC]

@halcyon, on the Princess 40 the indicator is connected the other way round from your description. The neon lights only when the polarity is correct. Read the label next to the neon on the OP's photo. This is also the case on my P40.

@sprocker, as others have said and as I can see in the photo, it's a neon bulb with a resistor soldered in series in the tail leads. Neon bulbs tend to flicker for a long time before they eventually fail. If this one failed suddenly it might be worth checking the resistor and connections.

 

[sprocker]

@halcyon, on the Princess 40 the indicator is connected the other way round from your description. The neon lights only when the polarity is correct. Read the label next to the neon on the OP's photo. This is also the case on my P40.

@sprocker, as others have said and as I can see in the photo, it's a neon bulb with a resistor soldered in series in the tail leads. Neon bulbs tend to flicker for a long time before they eventually fail. If this one failed suddenly it might be worth checking the resistor and connections.

Thankyou all for your replies. I've ordered one from RS.

@JerryC - The light has been very dim from when we first got the boat, so I suspect/hope that it was on it's way out all along. I will check the connections anyway as you suggest when I install the replacement.

 

[Greenheart]

April 5th 2019

Gentlemen, I'm asking here because my question doesn't justify a new thread.

I've been given a trickle-charging solar panel which still works...but the identical wires had snapped, so I can't tell which coloured crocodile clip to attach to which wire from the panel.

Is there a cheap reliable way to test polarity - like, which way a motor will turn - which doesn't require me to buy a multimeter?

Thanks.

 

[BruceK]

LED?

 

[Greenheart]

Thank you Bruce...that is definitely the quickest fix I ever had here.

Even more amazing, I Googled whether LEDs work with reversed polarity, found an old bike light and answered my own question, before I'd read your reply! :biggrin-new:

Incredible...I spent 50 minutes on Youtube looking for a way to detect polarity, and there's not one instance of this simple solution.

 

[Lon nan Gruagach]

LED?

Thank you Bruce...that is definitely the quickest fix I ever had here.

Even more amazing, I Googled whether LEDs work with reversed polarity, found an old bike light and answered my own question, before I'd read your reply! :biggrin-new:

Incredible...I spent 50 minutes on Youtube looking for a way to detect polarity, and there's not one instance of this simple solution.

If you dont have a handy LED or only one that works both ways....
Wire the unknown supply in series with a battery. The right way round will light a lamp (brightly), the wrong way round wont (much).

 

[jrudge]

Bear in mind a multimeter can be had for £5 or less on eBay and is a useful thing to have

 

[Greenheart]

Thank you, it's on my list with 'soldering iron' as inexpensive things I've been meaning to get round to buy, for the last twenty years.

 

[petem]

Bear in mind a multimeter can be had for £5 or less on eBay and is a useful thing to have

+1, even if you only use it for voltage detection it will soon pay for itself by preventing you from buying replacement bulbs unnecessarily. I have one of these - https://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=Sealey+Pocket+Multimeter&_sop=15.

 

[Hurricane]

Is this any good?
That part of the wiring for a Princess 67
Note that there are two circuits - main shore power and A/C.
Two Green and one Orange Neon(s) for each of the supplies.
The Green Neons light up when the "live" shore line has 240v above ground/earth or above Neutral thus indicating correct polarity.
If the supply is reversed, the Neutral has 240v on it so the Orange neon (connected between Neutral and ground/earth) will light thus indicating wrong polarity.

Actually, when testing a new supply, I prefer to use separate testers.
I use a Kewtech mains tester that I use in a lead that I plug into the shore supply tower to test it BEFORE plugging the boat in.
A Kewtech 103 like this:-

I then test the usual stuff like:-
Live to Earth = 240v (ish)
Live to Neutral = 240v (ish)
Neutral to earth = 0v (ish)
In the past, I was given a supply with 380v between Live and Neutral !!!
This is a handy device that I use to test the supply.

 

[Greenheart]

If you dont have a handy LED or only one that works both ways....
Wire the unknown supply in series with a battery. The right way round will light a lamp (brightly), the wrong way round wont (much).

That's also worth remembering, thanks.

Yesterday I bought a multimeter.

I had no idea I knew so little about electrics.

In spite of working out which was +/- with the LED on Friday, I connected the solar panel's negative croc-clip to the battery's positive, and vice versa. :hopeless: But after 48 hours, the multimeter shows that neither the battery nor the panel are impaired in their output.

Is a solar panel less effective, set up behind glass?

Hurricane, if you were responding to my post, I'm sorry I didn't understand. But before I hijacked it, this thread was from last year.