Introduction: LED Resin Cube

About: I've always liked pulling things apart - it's the putting back together again that I have some issues with!
Hello Again,
I've been wanting to use clear casting resin ever since I saw it used in this brilliant Instructable by Koogar.  Before I took on something as big as Koogar’s project, I wanted to start small so I came-up with “LED Resin Cubes”.

The idea behind the LED Resin Cube was inspired by a mercury switch that I found at my local electronic store.  I love the simplicity and look of this switch and wanted to incorporate it a project so you could see the switch in motion.  As the switch is made of glass and fragile, it’s pretty important to encase it in something strong – hence the clear resin.   

Check out the video below to see the LED Resin Cube in action.

This is a really easy project to do and the end result looks pretty cool.

Step 1: Things to Gather


1. LED lights.
I used these lights from eBay but it is up to you what type of LED light you want encased.  The LED's I used change colour everytime you push the swich, and for the last change the lights flash!

2. Batteries. 
I used these batteries from eBay.   They are small button batteries that can re-charge and throw out 3.7v which is plenty to power an LED/s

3. Charger.
I used this charger from eBay. 

4. Mercury Switch

5. Female 3.5mm power jack

6. Male 3.5mm plug

7. Copper wire.
(To make the frame)

8. Clear casting resin. 
This can be purchased from your local hardware store or eBay.  I used "Diggers Casting Resin" which I purchased from my local hardware store.

9. Solder

10. Casting mould. 
I used a small, square, plastic container which held chicken stock cubes - see below


1. Soldering iron

2. Pliers

3. Wire cutters

Step 2: Creating the Frame

The first thing you need to do is bend the copper wire to make frame.  One end is added to the battery terminals, and the other to the female jack which is how you will charge the batteries.


1. Bend and shape the wire as the below images show

2. Solder each wire onto the battery terminals.  Make sure that once they are soldered onto the terminals, the battery sits flush and the wires are reasonably straight.

Circuit Board - Make sure you mark-out or memorize where the wires are connected the circuit board and switch - you're going to need to make sure that you solder everything in the right place and on the right polarities!

3. Cut a small piece of copper and bend as shown.  Attach to one of the battery solder points on the back of the circuit board as shown.  This will be where you attach the circuit board to the frame/battery

Step 3: Adding the LED’s and Mercury Switch

Next thing is to add the circuit board which has the LED's attached, and switch.  Be careful – you don’t want to break the mercury switch!


1.  First you need to solder the circuit board onto the battery terminal via the small arm attached to the circuit board as shown.  This is a fiddly job and may take a couple of tries to get straight.

2.  Next bend another small piece of copper and solder to one of the solder points where the switch is attached.  This copper arm should be sticking-up as shown below.

3. Solder on the mercury switch.  As you can see in the images below, I have slightly angled the switch which will allow the mercury to move significantly enough to turn off the LED’s if they are turned on their sides.

4. Solder on the other switch wire to the end of the mercury switch.

5.  Solder the last wire to the other battery terminal.

6.  Add the female power jack to the ends of the copper, making sure the polarity is correct.  This is your chance to shorten the copper if necessary.

6.   Test.

Note – I’m sure that everyone is aware that mercury is very poisonous.  Please be careful when handling it and use the usual precautions.

Step 4: Testing the Resin

I decided to do a test first as I didn't want to mess up the LED's and have to start again!.  Instead of the LED's I added a battery to the resin (first thing I found lying around).  When mixing the resin I found that it starts out with a slightly yellowish tinge but once it sets turned clear.

I left the resin to cure for 24 hours and then removed from the mould.  I had to break the mould to get it out and then leave for another 24 hours until everything was completely dry.  The finish on the hardened resin was rough but clear.

I used some 600 and 1200 wet / dry sandpaper to get some of the roughness out of the casting and used some brasso to give it a really smooth finish.

I initially tried to create a hard, resin base and let that set but I couldn't wait so I just poured the whole of the resin into the mould.  If you look at the images, you can see a faint line where the 2 different set resins meet-up.

The steps on the following page show how to achieve a clear finish using wet sandpaper

Step 5: Adding the Resin

Now that you have finished your LED light and switch, you now need to put it in clear resin.


1.  First you need to decide on what container (mould) you want to use.  I found the below container at the supermarket which worked perfectly.

2.  I decided to use the lid as the base as it was smooth and would also help to get my cast out easier.  Cut the top off the container so you can pour the mould in.  I then hot glued the up-side-down lid to the opening.

3. Add the LED’s and battery to the container, making sure that the socket it at the top! (obviously) and add some blue-tack to the hole.  This way you won't get any resin in the jack.

4. Mix the resin as indicated.

5. Pour in the resin to the top of the jack.

5. Set to dry for 24 hours and remove from the mould once finished.

Step 6: Smoothing and Finishing

Once you take out the cast out of the mound (I had to break the mould to get it out!) you’ll have to polish the cast to get a clear, smooth finish.
I must admit I didn't what wet sandpaper is and how it worked.  After some research I discovered how to use it correctly.  I have put together some points below for these like me!


Wet sanding is a sanding technique that uses water to lubricate both the sandpaper and the surface to be sanded so the grit will last longer, and so you can attain a smooth-as-glass appearance. Using water while sanding will also keep the dust down.

1. Soak sheets of sandpaper in a bucket of water for 20 to 30 minutes before using them. Start sanding with a low-grit paper (300 grit) to remove large imperfections quickly.

2. Take the sandpaper out of the bucket and cut it to fit around a rubber sanding block. Wrap the sandpaper around the sanding block. Avoid wet sanding without a sanding block because your fingers will press onto the sanded material unevenly, wear the sandpaper out faster in those areas, and it may take longer to obtain an even sanding.

3. Spray the surface to be sanded with water, coating it evenly. The water will hide the scratch, so you will think it is gone when it isn't. Clean the water away from the area to see if it is really gone before moving on to other areas.

4. Sand the surface with progressively higher grits. Sandpaper is available in grits up to 4000, but it is OK to stop sanding after using 1200 to 2000- grit sandpaper.   Clean the surface in between grits to remove debris so the finer sandpaper is not contaminated with larger debris. Spray water onto the surface as needed.

5. Add a buffing compound such as Brasso to the sanded area when sanding has been completed and buff the area with a cloth.

Step 7: Finished


You now should have a pretty solid looking clear resin cube with an LED embedded inside.  Try it out and make sure that everything works ok.  If it doesn’t I’m afraid there isn’t much you can do but start again!

I found using resin pretty easy - as long as you follow the instructions you can't go wrong really.  It’s a great product and I can't wait to use it again.


The next one I make I don't think I'll use the female power jack.  Solar would work better and everyting would be contained inside the resin.  You would need to find a small (and I mean small!) , 4.5v solar panel but it would be pretty cool.
You could also have 2 peices of the copper sticking out of the top and when you need to charge you could connect a 4.5 solar panel to the ends.  This would be a good way to simplyfy the insides. 

Happy casting.

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