LED switches

Charles Holder · 6 Mar 2021

Hi. I would like an under-unit light in the kitchen. Nothing I have seen is what I want so I have purchased a neon flex rope light. It is 1m long with 120 LED's. If I am right, I have calculated that it is about 28 watts and requires a 12v 2.5 amp power supply. So I have a 12v 3 amp power supply and I am looking for a Push switch. All the switches I have seen are up to 2 amps. Can anyone point me in the right direction for a suitable switch bearing in mind I want to hide it behind a 55mm deep skirt. If I have my calculation wrong Can someone please help with that as well?

chivers67 · 6 Mar 2021

Would something like the Quinetic Fob switch be of any use to you? Or a Grid switch

https://www.tlc-direct.co.uk/Main_Index/Wiring_Accessories_Menu_Index/Quinetic/index.html?ad_position=&source=adwords&ad_id=188640074535&placement=&kw=kinetic switch&network=g&matchtype=b&ad_type=&product_id=&product_partition_id=&campaign=ROAS_Wiring_Accessories&version=finalurl_v3

Charles Holder · 6 Mar 2021

Hi. Interesting. After I got to grips with the concept it looks like a good idea. Almost £50 instead of under £5 is a challenge but it definitely looks as though it might be the better option. Thank you for that. I would consider the fob option definitely.

chivers67 · 6 Mar 2021

What switches have you looked at? An Architrave switch might suit too?

Charles Holder · 6 Mar 2021

Hi. Another great idea that I had not thought of and a lot cheaper. But you have given me something to think about with your curveball first suggestion. Just goes to show how much help is out there.

333rocky333 · 6 Mar 2021

Surely you will be switching the supply to the transformer, rather than the output, so the input current is a great deal less than the 3 amp rated output and even lower than the 2 amp switch rating

Charles Holder · 6 Mar 2021

Hi. This is where I am confused. I have never really worked with LEDs and am trying to get all the information I can. As I see it / from what I can find out.LEDs need a 12v power supply, which I have. According to several websites I have been on where there are all sorts of charts and calculators. 120 LEDs will draw Approximately 28w. watts to amps came to 2.5 amps. Now, this is where whatever my talent I may have had, runs out and leads me here.
Assuming the draw is 2.5 amps, I don't want to be using something that only takes 1 or 2 amps. If I am wrong, this is where I need help.
However, an Idea put forward earlier regarding some form of wireless switch is looking interesting and it would be rated far higher than the assumed 2-3 amps.

bernardgreen · 6 Mar 2021

Charles Holder said:
watts to amps came to 2.5 amps.

Watts = Amp x Voltage or Amps = Watts / Volts

The Amps for 28 Watts with a 12 Volts supply will be 28 / 12 = 2.333
The Amps for 28 Watts with a 240 Volts supply will be 28 / 240 = 0.117

333rocky333 · 6 Mar 2021

I believe where your going wrong is with the amps

A 12 V 2.5A transformer is 30 watts OUTPUT
Therefore as your supply voltage is 230V, then 30 Watts Divided by 230 Volts gives an input current of only 0.13 AMPS.

You would normally have a switch in the mains input to the transformer.
Switching the output could affect the transformer, as it will be still operating but with zero load when switched off

Charles Holder · 6 Mar 2021

This is where I don't get it.
I have a 230 AC socket. I plug in a 12v 3a power adaptor. So, assuming the 120 LEDs I am powering require a 12v supply and 28 watts, the supply needs to be 12v and 2.333 amps minimum. ?
I have the LEDs working with this power adaptor and want to fit an on-off switch. So a switch to pass the power through needs to be rated at over 2 amps. ??
Or not?
I am trying to get it right but the train has left me at the station. Perhaps I should go back to just replacing blown fuses. I'm much too old to go to night school ( Just the mention of night makes me tired )but would like to learn. However, safety is most important.

Swwils · 6 Mar 2021

It's the terminology that has got you confused.

In general; switches are listed with the maximum amp rating at a particular voltage. i.e. the switch is rated to carry that current continuously. If you lower the voltage the maximum amp rating is higher.

E.g. maximum amp rating for a switch at 250 volts AC (VAC) is 10 amps; the maximum amp rating at 125 volts AC for the same switch is 15 amps.

There are some exceptions to this, depending on the switch manufacturers recommendations and testing etc.

You must also not confuse AC rating with DC rating.

Some info here; from switch company;
https://www.carlingtech.com/amp-hp-volts

Charles Holder · 6 Mar 2021

OK. Yes, it is AC in DC out. If I could wind the clock back 50 ish years. I would have trained in electronics instead of Pub crawling. Mind you I don't remember much about the 60's. I have bookmarked your link to trawl through after I have had a lie down in a dark room.

flameport · 6 Mar 2021

Charles Holder said:
It is 1m long with 120 LED's. If I am right, I have calculated that it is about 28 watts

It's exceptionally doubtful that 1m length of LED strip/rope is 28 watts.
It would be ridiculously bright and require mounting on a substantial metal heatsink to avoid it overheating.

Charles Holder · 7 Mar 2021

OK. it is a 1M length of "Neon 12V low voltage silicone LED strip lights rope" It is advertised as having 120 LEDs. What is your best guess?

Charles Holder · 7 Mar 2021

I am getting a reading of 23 c

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