Help with AC switch

[dunner84]

Hello,

I picked up this 120vac switch with built in led for a small tube preamp I’m building.

The package didn’t indicate the requirement for a dropping resistor,  it it looks like there are tabs to accommodate one.

Any ideas what value/rating of resistor, if any, I should throw in there?

[sluckey]

Hello,

I picked up this 120vac switch with built in led for a small tube preamp I’m building.

The package didn’t indicate the requirement for a dropping resistor,  it it looks like there are tabs to accommodate one.

Any ideas what value/rating of resistor, if any, I should throw in there?

The resistor value depends on how much voltage you intend to feed to the LED.

[Latole]

IMO it for 120 volts use

https://www.evilmadscientist.com/2012/resistors-for-leds/

The next thing we need to know is the I, which is current we want to drive the LED at. LEDs have a maximum continuous current rating (often listed as If, or Imax on datasheets). This is often around 25 or 30 mA. What this really means is that a typical current value to aim for with a standard LED is 20 mA to 25 mA—slightly under the maximum current.
____________________
Using LEDs as mains indicator lights on 120V

[acheld]

BigClive -- that guy is great, and this video is really helpful.

Here is what I would do.   Try to find the company's data sheet for this product.  It should tell you how to wire this up.  There is a very good chance there is a resistor (or more) already present in circuit.

If you can't find the data sheet, then calculate what your led resistor should be using this calculator:  https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-led-series-resistor. 

A simple go-to explanation is here:   https://robrobinette.com/Generic_Tube_Amp_Mods.htm#LED_Pilot_Light

I normally use the heater tap for my indicator lamp, with a resistor and reverse diode protection.   Very robust and have not "yet" had one fail. 

I personally aim for aim for less than max current through the LED, as that prolongs the life of the LED. 

But really, try to find that data sheet.  You never really know what the company is doing until you see it.

[PRR]

> try to find that data sheet.

Easily found from the info in the picture. Yes, it would have been nice to see from the start; but isn't a lot useful.
https://us.misumi-ec.com/pdf/el/DS-060.pdf

It is VERY wasteful to run a 2V-3V lamp from 120V-240V. Even at 10mA it is way over a Watt of heat to lose. And it will flicker. This gets out of hand.

What are you actually powering? Is there some lower-voltage DC you can tap?

And while the sheet says 40mA it will certainly light with far less. Maybe as little as 1mA.

[acheld]

...  but isn't a lot useful.

Isn't that the truth . . .

[Beezerboy]

looks to me like the LED wants a DC power supply that does not come off the switched power... the LED power is a DC system power. I would imagine it is set for either 5 or 12 volt nominal systems. put your meter on a diode scale and read "ohms" on the LED circuit. it should only read continuity when the bias polarity is correct. on my Fluke, a 4-5mm Led reads about 15-1600 ohms. at 12v, you need a current limiting resistor that should add 400 to 1200 ohms. bear in mind that I do not know for sure, but I expect that the LED circuit has a resistor already in it

[mresistor]

Here is what it is..  and the manufacturers documentation.   https://www.tme.com/us/en-us/details/ds-060k-s-lr/rocker-switches/miyama/