A couple notes before beginning:
1. The knowledge and items in this instructable are fairly basic. This is a limit of my current skills and tools/equipment on hand. On the upside, this means that anyone with basic skills and equipment can make the pendant.
2. I don't work on jewelry either by trade or hobby so my skills with the decorative wirework is poor at best. Hopefully, anyone making use of this tutorial will have better skills than me in this regard.
Step 1: Parts and Equipment
Here's what you'll need for the circuit:
2x - 1K Resistor (1/4W)
1x - 1µF Electrolytic Capacitor (63V)
1x - 470K Resistor (1/4W)
4x - LED (Red)
1x - NE555 Bipolar Timer
Power source (not shown)
Switch (not shown)
Hacksaw (not shown)
Note that a 1µF 50V capacitor also works. However, at the electronics store I purchased parts from, the 50V capacitor was black and the 63V one was blue. The resistors were also blue so I went with the 63V capacitor for aesthetic reasons. The colour of the LEDs should also be chosen according to your aesthetic tastes. I didn't list a specific power source or switch here. These parts can be worked into the design or hidden so the exact parts used can be varied according to your needs. I've tested the circuit and confirmed that it works with a 6V battery (one designed for headlamps), a standard 9V battery, and a 12V combo (four 3V batteries).
For creating the pendant, you'll need the following:
1x - Casting mold(s)
1x - Resin (polyester resin is shown but epoxy resin is probably a better choice)
1x - Catalyst
1x - Mixing cup
- Resin colouring (Optional)
1x - Mixing stick (not shown - I used a disposable wooden chopstick)
For decorative touches, I used the following:
18 gauge aluminum jewelry wire
Bent nose pliers
Scotch tape (not shown)
Heat shrink tubing, 16mm diameter (not shown)
Heat gun (not shown)
Step 2: Prepare the Circuit Board
After cutting the board, sand the edges and corners to remove anything that might result in injury.
Step 3: Add the Circuit Components
Important note: Do not trim (or leave a fair bit after trimming) after soldering the components in place - we'll need to attach wires to the protruding metal.
Also note the layout in the first image is the back of the board (i.e. what you'll be seeing when soldering).
Step 4: Add the Wiring
The main annoyances at this stage were: 1. The time it took to create wires of the correct size and 2. when soldering the wires, the other end often heated up enough to melt the solder and loosen up. There are that might have helped draw the heat before it traveled further down the wire but I didn't have any on hand.
Step 5: Embed in Resin
Then I added the catalyst and mixed it in. Pour the mixture into the mold and add the circuit. When hardened, the resin will shrink so make sure the mold is as full as it can be. You may want to use a syringe (the ones you find at art shops, not medical syringes) to top off the mixture. If you do, make sure it's disposable, as it'll probably be clogged with resin afterwards. You'll probably need to add a weight on top to keep the circuit in place (the wires hanging off the side tended to drag that end down, lifting the other end. A 9V battery works well for this.
Put the mold in a well ventilated place and let it cure. The curing time is dependent on the resin you use, ambient temperature, the thickness of the cast, and the amount of catalyst that was added. Typically, you should let it sit for a few days before removing it from the mold.
IMPORTANT: Polyester resin produces harmful fumes. If possible, let it cure outdoors so you are not exposed to the fumes. Failing that, place it in a room with a ventilation fan that pumps the air outside. Epoxy resin is supposed to be much less toxic in terms of fumes so it is probably a much better choice. The only reason I used polyester resin was I had some on hand. If you don't have either, look into epoxy resin.
Step 6: Add the Backing
Step 7: Add a Wire Frame
I then attached the chain and looped the power wires through the chain (every 5th link). This configuration assumes that the power source will be attached at the back, where it's out of sight. To attach the chain, I first detached a couple links. To do this, I closed the bent nose pliers and inserted the end into the final link in the chain. I pressed my fingertip to the end of the pliers, essentially pressing the link down onto the pliers. Then, I slowly opened the pliers. This pushed the chain link open. Repeat and you'll have two open links. Attach the chain to the loops on the pendant with the open links and use pliers to close the links.
Step 8: Add a Power Source
Step 9: Attach the Power Source
Step 10: Additional Thoughts
Heat shrink tubing comes in different colours. I recall seeing black, white, green, red, and yellow. I'm sure there were other colours as well. I'm not sure how receptive it is to paint.
One thing I pondered was cutting a hole in the heat shrink to expose the center of the battery top (which was one reason to use a wire loop) but I didn't have anything that would give me a clean circle so that idea was abandoned.
I have all the components flush against the board. However, they can be pushed higher if you want them closer to the front of the pendant.
Some additional ideas:
- Add the LEDs after the resin step. The LEDs can be soldered onto the board after the resin has cured. This will allow the LEDs to protrude from edge of the pendant.
- Break up the circuit into several different components, embedding each in its own resin mold, connected via wires. This is useful for larger circuits or if you want multiple small pieces.
Edited to add schematics. These schematics are assuming you're creating a 2 layer board. These are based on the wiring in step 4 (photo 2). I've added a couple spots for attaching wires for power (labeled with "+" and "-"). If these are used, the wires will be visible in the resin. If you don't use these holes, just attach the power wires to the back of the board using the leads of the components as done in the instructable.
NOTE: These schematics are untested. I have not created boards using these schematics so I can't guarantee they'll work.