LED table lamp - 230v to 12V conversion which runs off mains power supply from socket

Right-o, hello everyone.

I have come a bit unstuck in the planning phase of a lamp project and hope that one of you clever sparks on here can give me a bit of advice.

I came across some quite large glass jars and though “wouldn’t it look good if I filled these full of water and put a light bulb inside”.  I searched for suitable underwater lights but the only ones that appear to be widespread are LED.  That’s fine I thought: long life and eco-friendly!
Now – it appears as if LED lights come in two voltage flavours.  The first seems to be able to run direct from mains supply as they appear to have in built transformers.  The second type comes in 12v and requires a separate transformer.  All the underwater lights I found fell into the latter category.

Further research confirmed that the transformer has to be of a particular type - capable of delivering a constant un-fluctuating voltage supply, otherwise the LED bulb will burn out very quickly.  Now there are loads of transformers on sale for converting mains to 12v – however these transformers all appear to have been manufactured for placement behind walls or in roof spaces.  There also seems to be some suggestion that you have to purchase the “right type” of transformer to “match” the LED driver used in a given light. 

I am now a little confused and I am uncertain whether I should proceed as the project I have in mind is to create a table lamp with a cable that plugs into the wall and that can be switched on and off with a switch installed on the cable.  All the LED transforms I have found appear to be for installation within roof spaces – and I am not certain they could be used with the particular bulb I have sourced anyway:

Here is a link to the bulb I would like to use: http://www.amazon.co.uk/Aircraft-Aluminum-Waterproof-underwater-light/dp/B00E8B2F7S/ref=sr_1_31?ie=UTF8&qid=1377529793&sr=8-31&keywords=underwater+bulb (my apologies If I am not supposed to post links to amazon – I couldn’t find a manufacturer’s website for this item)

My questions are:
(1) Will I have to buy a specific transformer to match the chipset of this LED lamp or will any transformer designed for use with LEDs be suitable (assuming that they convert 230v to 12v).

(2) The lamp is rated at 10 watts.  Do I have to buy a transformer also rated at 10 watts or can I purchase one which is rated at say 30 watts.  What I’m trying to ascertain is: Do I have to match the wattage exactly or can I just use a transformer rated at 10 watts or above?

(3) Can you get LED transformers that are designed for use in the home (i.e. not one that is intended to be installed in the roof space or behind a wall) e.g. is there such a thing as an LED transformer which you can plug directly into a mains socket?

(4) Is there anything else I have failed to consider that I should take into account.

Many thanks for any assistance.

All you need is a 12V transformer, at least 10 W. You can use a higher wattage, you can't use a lower one.

There are tons of transformers suitable for this, your profile doesn't say where you are in the world to advise further, although you may well have somethng suitable in the big box of old powersupplies we all keep on the offchance they are ever useful...Look for "Wall-warts".

If you are US based, try Radio Shack
If you are Uk based try Maplin
rcgraham (author)  steveastrouk3 years ago
Hi steveastrouk,

Thanks for the info - guess I made it a bit more complicated than necessary.