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Old 03-07-2013, 09:04   #16
Zil
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Re: Reverse polarity LED

You need two leds. a red connected as you show and a green connected from hot to safety ground. If red lights, = reverse connection. If green lights, = complete safety ground. If no green, don't trust no red. What resistance is to be determined by the smart ones. But leds are available to light at very low current.
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Old 03-07-2013, 09:48   #17
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Re: Reverse polarity LED

I repeat my earlier warning. Any LED driven off the AC voltages must have a second (non LED) diode flowing the reverse direction in parallel with the LED. During the second half of the sine wave it will prevent the reverse voltage on the LED from getting over 1 volt. LEDs have very low reverse voltage breakdown and would not survive without the protection.
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Old 03-07-2013, 20:11   #18
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Re: Reverse polarity LED

Hello,

I have finished the AC main panel (GEN meter and buttons next weekend).

I have the "ready light, as well as a "on-line" light when the main switch is connected to the Shore or the GEN.

The RPI light has the 50K Ohm resistor that does not trip the RCD or the breaker at the pontoon.

Alan
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Old 03-07-2013, 20:29   #19
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Re: Reverse Polarity LED

Hello,

A mate from the USA emailed this to me today... Thought I would share with everyone.

It shows the use of Neon bulbs... Not LED's.

Alan
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Old 04-07-2013, 10:45   #20
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Re: Reverse Polarity LED

Quote:
Originally Posted by Hkalan View Post
Hello,

A mate from the USA emailed this to me today... Thought I would share with everyone.

It shows the use of Neon bulbs... Not LED's.

Alan
Neon indicators were (and still are) quite popular as AC indicators. In some conditions they're not as bright as LEDs, and they often can go funny after a while and start flickering annoyingly.

As I mentioned before, you can get AC indicators (neon or LED), already made up and approved (eg UL, NEC, etc) for use on AC, for like $5 or less, at most appliance-parts stores.

Even Blue Seas has them, for like under $4
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Old 04-07-2013, 18:02   #21
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Neons are actually better in this application. Firstly driving LEDs from mains can require quite high wattage resistors , secondly faults in LEDs result in shorts with quite a nasty destruction of the PN junction.

A neon has two advantages first , under the strike voltage no current flows, and b , the current is very low , resulting in low power resistors.

No circuit should have a hot to protective earth led ( or any other circuit) , this injects current continuously into the earth wire , which is bad practice.

The standard circuit is a neon between neutral and earth . Its has the advantage that in normal operation the neon is off and no current is injected into protective earth.

If you want to test the safety ground , but the hot to earth indicator on a test button

Dave
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Old 05-07-2013, 12:40   #22
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Re: Reverse Polarity LED

every protected, AC multi-circuit strip I own has a green led indicating good ground (earth).
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