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LED switch wiring

alex_s

Jul 24, 2014
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Hi, I'm just dipping my toe into the electronics world and still learning a lot.

I recently got this switch that I'm using in an Arduino project to trigger sounds.

I've figured how to use the switch BUT I can't get the internal switch LED to light up.

What would be the correct way to wire this? (5V power is coming from Arduino)

ux_a12091100ux0622_ux_c.jpg
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Presumably you've figures which are the switch contacts. The other two are for the LED.

I recommend you connect a 1k resistor to one lead, then connect the free end of the resistor and the other connection to 5V. If the LED doesn't illuminate, swap the power connections over.

Once you know which way around the LED goes, you can use it just like any other LED.
 

alex_s

Jul 24, 2014
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Presumably I've figured out the three switch contacts (C, NO, NC) which are the three in the center on the same row (pictured above)

I've tried connecting 5v with resistor & GND to the pins top and bottom (of image above) but nothing happens.

Any ideas?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Try a lower value resistor. It's a red LED, so something like 150 to 180 ohms.

Did you try it with anything else before you asked here?
 

alex_s

Jul 24, 2014
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Thanks for your help so far... No luck with lower (or no) resistors. Could it be that a 5V power supply won't work with these?

They're 220v switches but is that related? (excuse my ignorance) I presumed that was the max voltage a switch can take, not a cap on the minimum.

I've not tried it with anything else before this but I have tested other switches that came in the pack.
 

(*steve*)

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Well, there are no specs in the auction. I would suggest you ask the seller.

I hope you haven't left feedback yet?

You could try 12V with a 1k resistor, but beware at 12V a reverse connection could damage the LED.

Have you tried measuring the resistance with a multimeter? What do you get? Is it asymmetric (i.e. is it different the other way around)?
 

KrisBlueNZ

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The specifications on the auction page give the "light voltage" as 220V. So if it's an LED, it will have a large-value resistor in series with it. It might also be an incandescent lamp or a neon, but the auction title does mention "LED".
 

BobK

Jan 5, 2010
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The specifications on the auction page give the "light voltage" as 220V. So if it's an LED, it will have a large-value resistor in series with it. It might also be an incandescent lamp or a neon, but the auction title does mention "LED".
It does say LED, if so, they probably use a capacitor to reduce the voltage, or else the switch would get quite warm. Lets see, 220V at 20mA = 4.4W, so I doubt that it is an LED with a resistor.

Edited: on the other hand, it does not say AC, but maybe they are assuming that.

Bob
 

KrisBlueNZ

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Yes that's possible. Also they could have used a high-efficiency LED. That would be a cheaper option. 1 mA at 220V = 220 mW. I agree AC can be assumed; not many people would be using 220V DC!
 

(*steve*)

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I actually red that but dismissed it as likely nonsense. Perhaps the LED part was wrong, or perhaps it is literally true.

This is a really good reason why product specifications exist.

I expect that the practical outcome is that it will be difficult to drive whatever "LED" turns out to be from an ardueno. Added to that the information in the auction could probably be interpreted correctly once you know what the device actually is, so you were not mislead (kinda)

If you end up stuck with these (and the price suggests it's not worth a real fight) then your best bet may be to see if you can take off the cap and replace whatever is in there with something more useful. If you're really lucky the "lamp" will be designed to be replaceable.
 

alex_s

Jul 24, 2014
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I see, so in summary there's a light in there that has been 'stepped down' to reduce a high voltage input (from 220v)? In other words, a 5V Arduino power supply is just too small?

I did try connecting a 12V power supply (8xAA batteries) but nothing happens. Also tried reading the resistance & continuity with a multimeter but nothing there either.

I've contacted the seller for clarification, but I won't expect much. Maybe I'll just crack one open and see what's happening inside.

Thanks for the input guys :)
 
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