Blinking LED Concrete Garden Stepping Stone

This is a concrete stepping stone with embedded clear glass jars with changing multicolor LED's inside of them.

I might modify this in the future by wiring the LED's to a solar charger from a standard garden light and if I do I will post the mod. But it really is simple to make the LED blinky's and it's also pretty simple to open the jars and put them in. CR2032 batteries are inexpensive enough (69 cents each) to just leave them in until they discharge but you can of course detach the LED if you want them to last. I have not yet found out how long they last because they have so far just kept going! UPDATE - These continue to light up now on Thursday night, a full four days. When the battery dies I plan to use two AAA cells in series and my guess is that will last a month.

Step 1: Tools and Materials

Materials
- Quikcrete cement (3.75 for a 60 pound bag, which is enough for two stones)
- water
- 2X4 or other wood for frame. (Cut to desired size. Mine are 14 inches on each side)
- 14X14X1/4 inch board for the bottom of the mold
- 2 1/2 inch screws and 1" screws
- Jars - babyfood, spice or similar jar. Mine were from flan that I bought at Costco. It would be interesting to use different colored jars. If you plan to use a stopper as I did, make sure that the diameter of the jar is narrow enough. You could also cut bottles down to size using a jig). My jars were about 2 1/2 inches tall and the opening was about 1 7/8 inch.
- rubber sink stoppers for the jar tops. You can use cork, other stoppers like spice jar stoppers if you use a rubber gasket). You want to keep the inside dry for the electronics.
- multicolor changing LED's - I got mine on Amazon but you can find them at RadioShack and all over the place. I used LED's that require 3V because then I don't need resistors for the CR2032 batteries. Any voltage from 2.75 to 3.5 will work but vary in brightness.
- CR2032 Lithium button battery or similar 3V battery. You can use 9V batteries or two AAA batteries wired in series. If you use a 9V you will need to use the appropriate resistors to limit the voltage.
- Duct tape for the batteries and to make a collar around the bottles when you pour cement.
Tools
- Saw to cut the mold and bottom to size
- Drill/Driver to assemble and disassemble the mold
- bucket for water and a quart bucket to add water
- trowel
- eye protection for the cement dust and when cutting the wood
- dust mask for the cement
- latex or nitrile gloves for the cement

Step 2: Make the Frame

Put on your eye protection
Cut the 2X4 pieces to 14 inches
Cut the bottom 1/4 inch board to 14 by 14 inches
Assemble using two 3 inch screws. I pre-drilled each hole and then drove the screws in. To keep the sides even I butt jointed each piece on the long side.
The bottom is attached with 1 inch screws.

Step 3: Assemble the Jars and Place Them in the Molds

Put the stoppers in the jars
Put duct tape around the top of the jar. This will create a dam when you pour the cement.
Put the jars with the bottom of the jar against the 1/4 inch board (bottom of the mold)

Step 4: Mix and Pour the Cement

Wear eye protection, latex gloves and a dust mask for this step.
Mix the cement according to the directions.
Pour to the top of the mold.
Let set for a day.

Step 5: Light the Electronics

Make blinkies by wrapping duct tape around the battery once you have correctly oriented the LED wires.
Put the blinkies in the jars and put the stopper on.

Note that the pictures above were made prior to the jars being placed in the mold. In the last step you can see the LED's in place.