Indicator lights on an appliance - I don't get it

[Discharged]

When I switch the kettle on, there's a pretty little blue light that comes on in the handle. It goes off when the kettle has boiled. That's fine, but...

What sort of light is it in there? It has to be 240v, and I guess it's very low wattage. But what I don't understand is what would it be called if I were to go hunting for one?

It's not like a 60w pearl bulb sitting on a shop shelf somewhere. What are these little indicator bulbs called? What sort of wattage are they? You get them all over the place - microwaves, DVDs, everywhere!

Cheers.

 

[Marvo]

There's different ones, some are neon some are led. They also come in different shapes and sizes.

 

[Discharged]

ok, thanks. So are these 'lights' rated at mains voltage, or does it not work like that?

 

[Marvo]

They often operate over a very wide range of voltages. I've seen neon indicator lamps with a working range of 60v to 250v.

Here's a few general purpose neons.

Link

 

[Discharged]

oh right, that looks pretty simple - but wiring, if I wanted it to show that the power to an appliance was on, would it be wired with one of the pins to live and the other to neutral? Or can't they be used like that?

 

[Specialist]

If you use the 250v one then just wire it across L/N on the load side of the on / off switch to show that the appliance is turned on, or on the input side if you just want to show that there's power going to the appliance. You can buy them ready made complete with a coloured holder.

 

[Marvo]

Yes they're just wired across the live and neutral. In a kettle it would be wired with one leg on neutral and the other on the switched live that also supplies the element. They're usually bi-polar so they'll work either which way around as well.

 

[Discharged]

Excellent stuff, many thanks both. My next project is...

 

[Knobhead]

It's to be hoped they will work both ways around. Unless you’ve got a DC kettle ? ? ? ? Now that would be interesting!

 

[Rockingit]

It's to be hoped they will work both ways around. Unless you’ve got a DC kettle ? ? ? ? Now that would be interesting!

Can't you get those as mini ones for cars and caravans?

 

[SPARTYKUS]

Yes you can. Boils a cup full in about 15 minutes!

 

[Discharged]

I've been searching here and there... seems like the neon indicators are about 6.5mm diameter, and I need it to be more like 3 or 4mm - which I think excludes neons. Now, as for leds, I understand that they need a resistor to work with 240v, but I don't know how to calculate which resistor to buy for whichever led.

 

[Deleted member 9648]

LED's work on DC at low voltages....to connect to 230v ac you need something like this....
FREE CIRCUIT DIAGRAMS 4U: 230V LED Indicator circuit

 

[Marvo]

As Wirepuller says LED's need a driver circuit with a DC output. Neons can be connected directly across live and neutral if their voltage operating range allows it.
Assuming you're not an electrician it can be very dangerous to fiddle around with this stuff. It would be better if you were playing with low voltage LED's rather than neons at 230volts.

 

[Discharged]

I just got some suitable neons from Maplins to try out. DOn't worry, I don't take chances with electricity - everything's shielded/covered before powering up - nothing is left bare. If there's any doubt about anything, the device is unplugged before investigation. I might even post you a pic of the result later (and it won't be of me lying in a heap on the floor with smoke coming out of the top of my head!)