Introduction: Box O' Light - Pocket Emergency or Reading Light
A simple LED light circuit contained in (what else) an altoids tin.
The light is switched on when the tin is opened (pics 1,3) and off when the tin is closed (pic 2).
This simple project was the result of my first foray into electronics, and is ideal for those with no experience who may be looking to get started with this brilliant hobby.
I originally made this with the LED's mounted on card, but will be rebuilding it using perfboard.
Step 1: You Will Need:
You will need the following electronic components (Pic 1):
Five white LEDs. Came in Starter Pack, smaller versions (Pic 1) available here.
1 10 ohm resistor. Came in Starter Pack
1 AAA battery holder. Maplin.co.uk
1 push-to-break switch. Ebay.
Insulated wires. Maplin.co.uk
You will also need:
1 piece of perf board or card. (Pic 3) Maplin.co.uk
1 Altoids tin or tobacco tin. (Pic 4) Poundland (Altoids tins no longer sold)
Electrical (insulated) tape. Maplin.co.uk
Wire strippers. Maplin.co.uk
Soldering iron and solder. Maplin.co.uk
All components and tools also available individually from www.bitsbox.co.uk
Pictured are brand new components, but I will be using the parts taken from the first build. Those parts are also pictured. To make things easier during the build process, I have made sure to trim the cathode (negative leg) shorter, just like in nature! (Pic 2)
Step 2: Prepping Parts
There are a couple of parts that need some modifications.
First we're going to trim down the perf board to the size of your tin. (Pic 1) You can either use your wire trimmers - snip along a line of holes, generally a section will fly off with each snip - or grip along a line with your pliers and bend and twist a section off. This second method is faster and easier. Make sure that your board is big enough to comfortably seat your LED's and resistor, but leaves enough room for your switch at one end.
If you're using card, then trim it to the right size and poke holes for the LED's, make the holes a little smaller than the diameter of the LED, so that they hold tight in place. (Pic 2)
Next, you'll need to get the switch ready. The type I used is almost perfect, except that the connectors make it too tall for the tin, so we'll need to bend them to the side - use your pliers for this. (Pics 3, 4)
NOTE: My switch was faulty, such that if pressure wasn't applied, sometimes the LED's wouldn't light. I thought this was due to faulty wiring in the first iteration, but this build had the same problem, so I now know that it was the switch. I believe I may have damaged an internal connection when I bent the terminals. Proceed with care.
Step 3: Laying Out the Circuit (perf Board Version)
Place your LED'S onto the perf board, (the legs need to protrude from the side with the copper). I put mine in a cross pattern, as on the 5 side of a die. Put your resistor on as well. (Pic 2)
Now bend the leads on the other side so that you can turn the board over without things falling out.
On the copper side, draw the circuit diagram on with pencil. (Pic 3) The diagram above was produced on EveryCircuit for Android (full version). (Pic 1)
The LED's are in parallel, so connect all cathodes (short legs) together, and all anodes (long legs) together, but don't connect short to long. The way I achieved this was by putting the top two and middle LED's cathode facing away, and the bottom two with the cathode facing towards me, and drawing connections around the outside and inside (this is easiest to see in the fully soldered image, Pic 4).
Connect the cathode of one LED to one side, doesn't matter which, of the resistor, and draw a connection from the other side of the resistor a short distance to where you will connect it to the battery and switch. Draw a similar connection coming off the anodes to a nearby point.
Now solder along your drawn connections. If you'd prefer you can just connect things up with wires.
NOTE: The spaces between holes will resist the solder, and it will require a bit of teasing and coaxing to lay tracks like those shown. This has led to a dodgy connection to two of the LED'S on my board, but I am a novice at soldering.
Step 4: Laying Out the Circuit (card Version)
Place your LED'S through the holes in the card.
Wire everything up according to the circuit diagram above. (Diagram produced using EveryCircuit (full version) for Android. Pic 1)
All cathodes (short legs) get connect and all anodes (long legs) get connected, but no anodes get connected to cathodes, so the LED's are connected in parallel. (Pic 2)
Solder the resistor to one of the cathodes.
Step 5: Connecting the Battery and Switch.
With a nice long wire (okay, not too long, but you don't want things pulling in each other in the tin), connect the positive terminal of the battery holder to one side of the switch (Pics 1, 2). I used a nice neutral white wire here, as it helps to colour code wires where possible.
Now connect a wire to the other terminal of the battery holder (I used red) and another to the other side of the switch (I used black) (Pic 3).
NOTE: I had some problems with my battery holder. The first was that the negative terminal wasn't actually connected to the spring inside, I don't know when that happened. The second occurred when I resoldered to that same terminal, and accidentally melted the plastic, or maybe expanded the metal too much, and the terminal sprung out! I put it back in place by melting the plastic over it, another problem caused by my soldering skills!
Now it's time to finish the circuit. Solder the positive wire to the resistor and the negative wire to the resistor cathode. (Pic 4)
Putting batteries into the holder now should cause the LED'S to light up. (Pic 5) If so, you can skip the next step.
Step 6: Troubleshooting the Circuit
If you are more competent than me this step probably won't be necessary.
Use a multimeter to check your connections. It was here that I discovered the fault with the battery holder, but not before assuming I had connected the battery the wrong way and de- and resoldering.
Generally a fault here is going to be a poor connection. Having fixed the battery problem, I also discovered the fault in the solder track. Doesn't matter, everyone has to start somewhere.
Step 7: Finishing Off.
Circuit ready, it's nearly time to put it into the tin. First, it's time to insulate the circuit from the metal. First, cover the exposed connections with electrical tape (Pics 1,2). Then put some tape into the tin where the switch is going to go (Pic 3).
Now you can put it into the tin, with the battery holder under the board or card, and attach the switch to the side of the tin. I used electrical tape here, too, but it would probably work best with a spot of glue. (Pic 4) The top of the switch will be just above the lip of the tin. (Pic 5)
Now closing the lid will press the switch, break the circuit and extinguish the light. If it doesn't you can see a little light spilling out onto the table. (Pics 7, 8)
Step 8: Improvements and Final Thoughts
My original box o' light worked brilliantly, although occasionally you had to press the switch down a couple of times to get it to turn on or off, it otherwise worked exactly as planned, and fit perfectly into the tin.
This version had several problems. Because of the thickness of the board compared with card, the LED's on top of the battery holder are thicker than the tin, so the lid can be hard to close. This could have been prevented by putting the LED's closer together and making the board smaller so as not to cover the battery holder, or by using the smaller LED's shown in the components picture in 'You will need:'.
The solder track issue, as mentioned, was due to my inexperience at soldering, and meant that the board needs to be pressed down to reconnect the two LED's.
The switch was damaged, possibly during the bend process, but I will replace it with a new switch and update when I get a chance.
Possible improvements include mounting the LED's at angles - the majority of light from an LED is cast along its length, which in this case is upwards. The original card-mounted version wasn't as secure, and avoided this problem.
Another way to mitigate this problem would be to polish the lid thus allowing the lid to reflect the light to where it is needed. A match stick might also be needed to prop up the lid, in this case.
I hope you enjoyed this instructable and your new box o' light and if you make one, please share your pictures in the comments section.