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How to wire Bulgin switch LED

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jack0987

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I have several Bulgin switches but am not sure how to wire the internal led.

Their part number starts with MP0045/Id2.
I have the 12 volt versions.

Their data sheet does not show switch internal wiring.

Do these leds require a limiting resistor?
Can you just connect the led to any voltage between 5 and 12 volts?

Also the led terminals appear to be marked plus and minus but I did a quick test with 5 volts and they light up with either polarity.

In general, how do I work with these? Thanks.
 
If you have a few might be worth pulling one apart and see whats inside.
I suspect that there is a bridge rectifier inside as they light up both ways, that or its a special led that has 2 diodes in anti parallel.
Do your5v test again but this time use a meter to measure the current, if its around 10ma then chances are there is a current limiting resistor, the fact they lit up without popping means there probably is a resistor as 5v across an ordinary led would zap it.
 
When I did the test, I just briefly tapped it with the 5 volts so as not to blow it and am afraid to put a sustained voltage on them to do a measurement.

I really do not want to take one apart as they are about 16 bucks each.
 
OK then another idea, put a 10k resistor in series with the led, connect it to 5v or better 10 or 12v and measure the voltage across the led's connection terminals, f its around 1.8v for red or 2v for green then chances are there is no built in resistor, if the voltage is much higher and the led doesnt light or isvery dim then theres a built in resistor.
Not definate but a bit closer.
5v across a red led might well blow it in a mS.

Edit looking at the datasheet I'd say the resistor was built in as they quote 12v and 220v dc.
Might be worth a phonecall or email to bulgin, they are a well known company so probably will be helpfull.
 
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Thanks. I did email Bulgin but have not heard back from them yet.

Using a 10K resistor in series powering at 5 volts, I measure 4.88 volts with a green one.

I suspect from what they are saying it does have a built in resistor.

Since they quote 12 volts and I am going to power at five volts, what should I do? Do I need a seperate 12 volt supply to use it properly?
 
Nope if its bright enough for you at 5v go right ahead and use it at that, leds come to no harm underun.
 
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