Quickie LED Light Hack

This is a very quick and easy hack to convert an LED light that runs off batteries to mains (wall) power.

Standard warning: following these instructions may kill/maim/turn into flowers everyone your know and hold dear. Be smart.

Usually, LED lights run off batteries, because… well, let’s expand the acronym. LED stands for light-emitting diode, a diode being a circuit element that usually only lets current through in one direction. Hence, it stands to reason that trying to put an alternating voltage across it will result in subpar performance, since half the time the current is trying to go “the wrong way”, and it won’t light up very brightly*. Also, making a diode rated for 120V is probably a pain: regular 1N4001’s rate to 50V.

However, batteries are a very poor power source for a stationary light. Since the light has to put out an appreciable amount of light for long period of time (versus, say, a flashlight), the batteries wear out quickly (and I don’t get why regular alkaline batteries are so prevalent. Rechargeable batteries have not been shown to be detrimental to the environment to me, and taking the position of the armchair environmentalist, it seems that even if you could squeeze only 10 charges out of it, it would displace 10 batteries otherwise destined for the landfill, and grabs energy from the wall at at least 80% efficiency (depending on your charger). The only problem I would see with this is running out of Li (unless we’re talking strictly NiMH), but we just need to get working fusion, and we could probably synth our own Li. Of course, this would be incredibly ‘inefficient’ as a process to produce Li). Hence, the motivation for this particular mod.

To get DC from the wall, the easiest solution is grabbing a wall-wart (essentially an AC->DC converter in a plug) and sticking it in place of the batteries. Find yourself a wall-wart that outputs about the same voltage as all the batteries combined; mine used 3 AA batteries, for a total of 4.5V, so I used this 5V wall-wart from BG Micro http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&ProdID=12944 (or something like it).

So, most of these wall-warts output their DC voltage through some obtuse connector: in my case, I got ‘lucky’ and got a barrel type connector, where the outside of the connector was ground (0V) and the inside at 5V. To get at the 5V, I used a mangled paper clip. Note that you could also snip the wire, strip it, and figure out which one is 5V with a meter.

Now for linking the DC power into the light: in this case, I had to snip some more of the paper clip to get it to fit into the battery slot, and add some aluminum foil to connect the negative terminal with ground. If you snipped the wire, you could solder the wire to the battery terminals, or otherwise manhandle the two to stay together.

A modded plug, using electric tape to secure the foil.

If you have multiple battery slots like me, bridge it with wire, again soldering or manhandling it into place. I have not tried this yet, but sticking a resistor in place of a wire might lower the voltage across the LEDs, and make more apparent such things as a “half intensity” mode.

Wires marked in red for visibility.

Put the plug into place:

What it says.

Then, we cover everything up/partition with electrical tape to lessen chances of death by 5V:

Electrical tape is pretty cool.

At this point, if the wart is plugged in, the light should turn on.

Tape should be used to secure the plug.

Tada! If I have time/motivation, I may do a more DIY method for the same result.

Tangent: Future Electronics packs their stuff much more efficiently than Newark.

* There are non-directional LEDs, but they tend to be a bit more expensive than your run-of-the-mill polar LED.

Also, sorry about blurry pics: still learning to shoot well with SLR.