This clock incorporates LEDs and mirrors behind a glass face. There were 20 or 30 different glass panes to choose from at the hobby store, but I chose this one because of its texture and unique light reflections. In this instructable, you might learn one or more of the following: how to drill a hole in glass, and how to build a simple LED circuit.

I live in a desert climate. It's very dry here. The adhesive methods I use for this clock may not work very well in a humid climate. I didn't have to worry about this so the construction here does not account for humidity.

I was inspired to make this unique variation of a clock because of the simple clock by instructables member Dipanker,
https://www.instructables.com/id/LED-CLOCK-cum-NIGHT-LAMP/
My clock would have been just as simple, I think, if not for the idea to use glass, and then mirrors --- and I decided 12V DC would be safer for my kiddos than 220v :) props to him, though, for making me want to make a clock of my own.

As always, as I undertake a new challenge I am reminded that DIY from scratch is always a challenge, takes way longer than I initially anticipate, (seriously, my wife makes fun of me all the time because my 1 hour projects turn into 2 day ventures), is more fun to build, and if you have to buy every last item, DIY tends to cost more too ;) I had a lot of this stuff already, but here's a list otherwise:

What you will need:
First the electronics:
LED lights, 16 of them ($4 from ebay)
quartz clock mechanism (hobby store, $6)
12 V DC power supply (www.goldmine-elec.com 12v supply, $3)
330 ohm resistors, 8 of them (radioshack, $1-$3)
DC jack (radioshack, $3)
wiring (I used bell wire, $3 for 60+ feet of it)
PCB board (radioshack, $2)

The hardware:
12 x 12 glass pane (hobby store, $5)
5/16" diamond-tipped drill bit (home improvement store had a kit with it, $10)
hardboard (home improvement store, $5)
wood trim, rectangle cube (home improvement store $8)
Duct tape (any desired color, $4)
mirrors (24 pack, $2)
Super Glue, I used E6000 ($3-5)
Blue paper ($1)
Glue stick ($1)
Handitack (?, I had this for years)

Other supplies and tools needed (some optional):
Miter saw
small screws
soldering iron
Hot glue gun
screwdriver
tiny drill bits
plastic numbers ($3)
measuring tape
square
Patience

Estimated cost to build all this from scratch: $50 to $80
My cost to build it after deciding to build it (I own junk): $35

Hopefully this inspires you to make your own variation of a clock. Thanks for looking, I hope you learn something!

Step 1: Making the Cuts

The standoff pieces were 5/8" thick.

Place the glass on the hardboard and trace it. The glass is never a perfect square, so mark the board in some way to know which is the top, and mark the glass with masking tape to tell you the same. When buying the glass try to find the one that is the most square.

Cut the board out. Cut the little standoff pieces, and you're done with the cutting.

Step 2: Drilling Glass and Preparing It

I have never handled glass or drilled a hole in it, so this was fun.

1. Tape it up!! The tape will help the integrity of the glass. I probably used more than was necessary, but since I'd never done it, I taped everywhere. Then get a square of some sort, and find the middle of the glass. My glass wasn't perfectly 12" so it was necessary to measure to the middle of all four sides, and then use the square to draw the center lines.

2. Once the middle is found, mount up the glass cutting kit! It stuck right on there. My awesome wife helped me hold the glass up vertical, so I wouldn't be able to unconsciously press too hard if it were laying flat. It took 2 or 3 minutes to drill the hole. I was starting to wonder if it was working! It says to use a cordless drill, but just make sure you don't get water running down into the drill or its components. I used an electric one.

3. On the hole, the drilling was successful. (Yeah, I went for the one-liner--double meaning (w)hole pun, haha) Take the tape off.

4. I then covered the outside edges (they were kind of sharp) with my white Duct Tape (Duck tape was the name brand). Make sure the front has a bigger lip than the back, or you can see the back through the front.

Step 3: Lots of Little Drilling and LEDs

This part was quite tedious. Measure twice, and hopefully just drill once :)

NOTE: I chose not to put my paper on the board yet. I doubted the pencil marks would erase very well (construction paper doesn't like erasers) so I put it on afterwards, and had to hand drill the holes through the paper from the back (see pictures if that didn't make sense).

1.   I marked the center hole with a pencil by placing the glass on the board, and marking the board through the hole in the glass. Then I drilled a 5/16" hole just like the glass. From there, I measured for the 3, 6, 9, and 12 points. I tried to make sure the LEDs and the mirrors would all still be visible after placing the glass on them as I marked the holes. Use the mirrors and a LED to help with the marking.

After drilling two tiny holes (I used the smallest drill bit I could find) for all 16 LEDs, I was ready for the next part.

2.   Paste the paper on top. I used a glue stick, and the paper was so thick that it tried to bubble up on the ends if I tried to fold it under, so I just glued it flat as seen in the photo, and then I just cut it flush with the edges with some scissors. Then I drilled the holes through the paper as I had said before in the note above.

3.   Insert the LEDs. I put the positive (long side) lead of every LED on the left side so I could keep track.

Step 4: Building the Circuit

1. Depending on your power supply and the size of your LEDs and the corresponding voltage they use, this circuit's design can change from project to project. The most useful link on the internet for this is using this: http://led.linear1.org/led.wiz
From this link you should be able to know the exact layout of your circuit, which is why I don't have one here.

You just need to know your power source and how much voltage each LED uses. Also, after it tells you the circuit combination make sure the power it uses doesn't exceed your power source's ampere rating. Mine was a 12V, 500 mA power supply, and the circuit I made uses 160mA from the source.

HOWEVER, IMPORTANT NOTE: You need to use a volt meter and check the voltage. Most wall adapters that say 12v DC, when measured are putting out 20V or so. Your resistors will get hot trying to compensate if you only get resistors for 12V. My power supply turned out to be a 9 V, 210 mA supply, but when measured put out 12.8 Volts, which was perfect for my circuit and resistors.

For me, it was connecting the LEDs in series 2 at a time, making 8 parallel branches. Remember when connecting in parallel, if the resistance values aren't the same in each branch (or even if they are), you will only get just less than the least resistive branch running through all the circuit.

To explain, parallel resistance can be found using the reciprocal of the sum of the reciprocals method. Example: I have 3 branches in a parallel circuit. In branch 1 is a resistor of 300 ohms, branch 2 is 400 ohms, and branch 3 has a 500 ohm resistance from its components. In a series circuit I can just add them together, getting a total of 1200 ohms resistance. But in parallel, (get a calculator) it's 300^-1 + 400^-1 + 500^-1= X , and then take that number and reciprocate it again (X^-1) and you get 128 ohms in each branch for the whole circuit. 12V going through an LED that needs 500 ohms and instead has 128 is going to make the LED hot and angry. Anyways, I digress, the link to the LED wizard takes all this into account and tells you what to use right away :)

The photos show how I wired it somewhat and the little PCB board I used and how it was wired.

2. Now for the soldering and hot glue! I admit some laziness here. Normally I would have wrapped the wires and shown a lot more workmanship here. So yes, this is a mess, I admit it :) The hot glue gun I used on every LED lead and every wire loop to contain it all down. For the clock I used hot glue also to keep it in place. Get it right the first time! Hot glue is no fun once it's cold and covering your stuff.

Step 5: Put It All Together

Once the circuit is done, attach the 4 blocks for the corners if you haven't already. Important: If you haven't checked the clock mechanism, make sure it pokes through enough to get the nut on the shaft (see first picture!) You may need to make the blocks thicker or slimmer.

The rest is self explanatory.

1. Take the mirrors, get the handitack ready, and attach them on an angle. Also, make sure each LED is pointed the right way, each may have shifted while doing the soldering job. I used a windex wipe on the mirrors when I was done to get my fingerprints off of them.

2. Take super glue that's made for glass, and apply it to the four blocks. Attach the mirror according to the adhesive instructions. I used E6000 here.

3. Cover all four corners of the mirror with the duct tape once more (see photos). This is to cover the wood from being seen from the side and so you don't have to wait for the glue to completely dry.

4. Put the hands on the clock.

5. Put the numbers onto the clock. This is where my textured glass was annoying. The numbers came with adhesive on them but didn't like sticking to glass. If the glass were smooth I think I would have been okay. So I had to go back and use a tiny bit of super glue for each number.

6. Your choice to hang it or place it against something. I put 2 hanger on the back of mine and then used regular picture hangers to mount it on the wall. Put in a battery for the clock, and plug it in for a great wall decoration (or night light for my 1 year old in this case)!

Thanks.

Update 9/3/11: My wife says it really lights up the room! She tells me our 1 year old had her up like 20 times because it was too bright, lol. Sorry honey! No, I didn't sleep through it, I'm a night shift worker (but then it's always night where I work.) But on the flip side, it only uses 1.44 watts (120 mA) while plugged in. We are putting this one in our living room, and my wife wants me to make one with less LEDs and about a quarter of the size (or maybe 6x6 instead) for his room. Don't misunderstand, it's great ambient lighting, and it's not really bright enough for reading or anything, but it was too bright for my 1 year old to stay asleep! :)