Looking for something with a bit more shimmer and blink than a diamond and a whole lot more personal? Here's how I made an LED engagement ring cast in resin.

You will have to solder copper wire to a battery and to surface mount LEDs, pour and pigment polyurethane resin, and make a mold of the ring you want. I had done none of this before I tried it, so it can't be THAT hard, right?

Total making time is at least 8 hours, though it took me several weeks start to finish.

NOTE: In this design, the batteries are not replaceable and last roughly one week. If you improve the design to make them replaceable, please get in touch.

Supplies needed:

Three small LEDs of your choice (I used two blue surface mount LEDs and one white 3mm LED)
Copper wire
Solder & soldering iron
Two small coin cell batteries like for a hearing aid (I used SR512SWs)
Silicon mold (I used Smooth-On Mold Star 15 SLOW)
Resin (I used Smooth-On Smooth-Cast 325)
Resin pigment for color (I used red and yellow from the SO-Strong color system sample pack)
Something to join the batteries in series (I used Keystone Electronics coin cell battery holder 112 but you could just use more copper wire)
Normal ring, sized properly, to use for molding the LED ring

Step 1: Build the Blinky Ring Skeleton

Take two strands of copper wire (enough for each to go around your finger easily) and lay them out side by side.

Then take the three LEDs and solder them to the wires.

Be sure to solder all the positive leads to the same copper wire and all the negative to the other. The easiest way to be sure you are doing it right is to solder on the center LED first, test it, then test the next LED, solder that on, and so forth.

Step 2: Check Your Blink

So far here's how it should be looking when powered up.

I just used alligator clips and a 3V battery to check the circuit.

Step 3: Clip Off Excess Wire

Clip off the excess wire. The less wire you have the easier it will be to manage when you have to fit it into the mold.

I chose to have just one wire on either side, but you could keep both if you wanted. Doesn't really matter. Eventually I trimmed them much closer.

Step 4: Battery Pack

The battery pack was the hardest part, and the sloppiest in my design.

The LEDs need 2.8V to light up. 3V batteries are too big to fit in a ring. So I used two 1.55V batteries in series, which = 3.1V. They will NOT work if wired in parallel. So here's how I solved the problem:

I took a coin cell battery holder and used it like a wire connecting two batteries, soldering it directly to the battery. Crude, but effective enough.

Connect the positive end of one battery to the negative of the other. I had the battery holder on hand because I was originally trying to make a replaceable battery pack with it but it didn't fit two batteries in series at all. You could use anything that you can solder to the battery for this.

This is not easy, and you have to be careful not to heat the battery too much. The more you do, the shorter the battery life will be.

I found it easiest to do this step by putting one battery face up and one face down and connecting the two batteries in that position, as shown in the photo. My suggestion is to put a dab of solder on the battery itself first -- this is the hardest part -- then try to be quick about heating it back up while connecting the battery holder.

NOTE: Some LEDs, namely red ones, will take a bit more power and may not light up with 3.1V, so I suggest avoiding red as a color.

Step 5: Connect the Battery to the Blinky Ring Skeleton

Measure out the right length wire to roughly fit the size of the final ring you want.

Then take the positive end of the battery pack and solder it to the copper wire that connects to the positive end of the LEDs. Do the same for the negative wire and negative end of the battery pack.

Try to solder at points that make the size of the ring roughly right.

Best to test the connections and make sure the LEDs light up before soldering.

Again, this will be tough to solder directly to the battery.

Step 6: Mold Your Ring (You Can Also Do This Step First)

Now that you have your light up wire ring, we need something to put it in.

We can't use metal because that would short the circuit, so I chose resin.

You can buy a silicon mold online and use that, or you can make your own mold. The directions are fairly straight forward on the packaging of the Smooth-On mold, but here's how I did it. (The photos are a bit out of order and skip steps because I couldn't easily take pictures while also handling the mold.)

For the ring to use as a mold, I bought a $5 wooden ring that was the shape and size I wanted. If you use another resin ring it might float in the silicon mold. Better to use something heavier. Remember to pick something that is at least a wide as the battery pack. I placed the model ring in a plastic Tupperware container then mixed the mold and poured it in.

The mold I used takes about 4 hours to dry.

When it is done, you should have a ring shaped hole in your mold ready for resin.

NOTE: If you haven't used resin before it is probably best to do this step and the next ones before connecting the battery pack. Get your resin skills up to your standards before you test it on the blinky ring.

Step 7: Pour the Resin Ring

I suggest testing this step with just resin before doing it with the light up ring in the mold, particularly if you haven't poured resin before. Follow the instructions on the resin packaging.

You'll have to pour the two liquids in careful proportions into different containers then mix them. I chose this resin because it didn't require me to measure out exact weight ratios, just a one-to-one volume ratio. I measured the resin by marking a line on the side of two cups at exactly the same height. I marked a popsicle stick with a pen then put it in the transparent cup and drew a line on the cup at the height of the mark, then did it on another cup so I had two equally marked cups.

Coloration is something best sorted out by experimentation. I chose to color the ring a light orange. I was shooting for an amber look. A very tiny bit of resin pigment goes a very long way. So instead of buying a single color pigment I went with the sample pack and played with the color combinations a bit to get what I wanted.

I wasn't so careful about how much I was pouring in actual volume, just that they were equal. So, I can't guide you very well on how much pigment to use for the same color as me other than to say, look at the photo and that's about how much I was pouring.

In the end, I used two pin pricks of red pigment and one of yellow. I took a needle and dabbed it in red then rubbed it on the side of the cup and did the same with the yellow and then stirred the color into the clear liquid until well mixed, then combined the two liquids as instructed on the resin packaging and poured it into the mold.

I tested a few rings without any LEDs or wiring to see if I liked the color. It took about four tries.

Once you have your colors where you like them, place the light up skeleton into the ring mold. I made space for the 3MM LED by cutting a small X shape indent into one end of the mold where I wanted it to go so it could fit and extend "out" of the ring.

Then ... pour the resin.

It dries in minutes so you have to move fast. It also gets hot, which diminishes the life of the battery.

Step 8: Give Ring to Special Someone

Follow the instructions on the resin for how long to wait before removing the ring.

When you do take it out of the mold it will probably be a little soft, this is the time to take a sharp pair of scissors or an X-Acto knife and cut off any stray bumps or lumps you don't want on your ring. You won't be able to do it later once the resin hardens.

Then let it sit for a few hours to fully harden and you have your ring.

All that's left after that is to go through with the proposal and offer it up to someone special.

Hopefully it goes as well for you as it did for me.

I'd love to hear from any of you if you do use this instructable to make a ring like this or something similar. I'm @alexgoldmark on Twitter.

Huge thanks to @Liza_Stark (she said yes!) for being the inspiration for all of this and @Jkeefe for tons of guidance start to finish. Together we are Team Blinky.

And big thanks for the patient guidance from the folks at The Compleat Sculptor in NYC who helped me choose my materials and figure out how to use them, albeit poorly.