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3V battery circuit / back lit rocker switches

David Roberts

Dec 22, 2017
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Hi Guys,

Hope you're all well and Merry Christmas to you!

I'm a product designer and total electronic circuit building novice so please be kind!
I have a requirement for a simple lighting circuit powered by battery (2x AA) 3V. The problem is I wish to use a red illuminated rocker switch which is 20A and rated for 250V - is there anyway to make this work on my little economic 3V circuit?

Thanks for reading
Dave
 

Bluejets

Oct 5, 2014
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You can use the switch no problem but the illumination will almost certainly be a neon indicator. These are used with a resistor for 250vac operation. Neon striking voltage is around 90v. Perhaps look for an led illuminated switch instead. Probably more common in the 12v dc range though. For your application perhaps just use a standard low voltage switch and mount a led and resistor in a bezel beside the switch.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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The problem is I wish to use a red illuminated rocker switch which is 20A and rated for 250V - is there anyway to make this work on my little economic 3V circuit?
Can you provide a wee bit more information about the rocker switch... like who makes it, what the model number or part number is, where you procured it, maybe a picture of what it looks like and a wiring diagram of the terminal arrangement? The contact current and voltage specifications have absolutely NOTHING to do with how the switch is illuminated. Common methods of illumination use a neon lamp, an incandescent lamp, or a light-emitting diode (LED). If it is truly a "red illuminated rocker switch" it probably uses an LED with two separate terminal connections that are independent of the switched terminal connections, because of the voltage rating of the switch contacts. If this is so, there should be no problem lighting the LED from a 3V battery power source.

Please provide more information on your switch.
 

Audioguru

Sep 24, 2016
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The datasheet for the switch has no details:
1) Is the illumination done with a light bulb or with an LED? What color?
2) Is the switch illuminated all the time, or only when it is off, or only when it is on?
3) Are the switch contacts rated for only 12V or is the light bulb 12V?
4) What is the maximum allowed current for the switch contacts?
5) Why doesn't the sketch of the switch show the location of the light bulb?
 

Bluejets

Oct 5, 2014
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Post a link to where you found this sw as farnell(elements14) do not recognise the number and abccomponents comes up as some type of aviation supply mob.
 

dave9

Mar 5, 2017
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You are unlikely to find a rocker switch set up to illuminate at a range that coincides with your variable battery level, 3V down to 2V drained, but do look around if you wish.

The alternative then is find a different rocker switch, one with a clear indication it can be non-destructively disassembled so that you can put a typical 1.8Vf red LED in series with a 100 ohm 1/8W resistor, wired to the closed circuit and ground contacts. This will give you more light than you need at 3V (but a still manageable 12mA LED current) but also 2mA (just enough to see) once the battery drains to 2.0V at which point it has little capacity remaining.

If you already have the switch you linked, go ahead and try to pry it open. It's useless in its current form, has no hope of illuminating acceptably at 2V to 3V. Otherwise just use a panel mount LED holder to panel mount it instead of it being in the rocker switch.
 

BobK

Jan 5, 2010
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Where did you get the 250VAC 20 A specs? These are not listed in the doc you linked.

Bob
 
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