Laser cut gear clock with ChronoDot using Arduino

This summer, my hackerspace LVL1 (in Louisville, Ky) got an awesome laser cutter  LVL1 is an awesome community of creative folks that like to build stuff.  You can always check out what we are up to at  If you like instructables and making stuff, you should see if there is a hackerspace in your area.  Anyway…
Arduino Laser cut gear clock
I decided to build a gear clock after seeing something like what I made in a friends office and after playing with the gear renderer in Inkscape.  This instructable hopefully will show you how to make what I made and also teach you a little about the design process involved when working with a laser cutter.

Step 1: Gather your materials.

For this instructable I needed…

You will also need a computer to program your Arduino and also for designing in Inkscape.

Step 2: 1st prototype

For the first prototype, I just wanted to see if I could get the stepper gear thing working at all.  I cut a spur gear for the stepper, a small stand with a hole in it to press fit the stepper motor and a larger gear that would be the clock mechanism.

After assembly and a quick program, I decided that the clock needed to have two gears (and thus two stepper motors) – one for hours and one for minutes.  I also discovered that the numbers needed to always be right side up as the gear traveled around.  Thus, the 6 needed to be upside down in the drawing as well as the 3 and nine needed to face outwards.

Another cool thing I discovered during my first prototype is that the Arduino has enough power to step these motors without having a driver circuit.  This makes the clock considerably easier to make!  Here are a couple of links to tell you about how to hook up the Arduino to the stepper I used…

I also began to think about my gears.   In my prototype, I used a 10 tooth gear for the gear connected to the stepper and a 100 tooth gear for the ring.  100 really does not translate well into hours or seconds so what else could I use?

My stepper gear has 10 teeth and this actually works well because the stepper I am using has 20 steps per revolution.  Thus I can step the stepper 2 times to move exactly 1 tooth.

Therefore, for my minute hand, if I use 60 teeth, then each 2 steps = 1 minute = 1 tooth of movement.

Similarly, my hour hand has 144 teeth because if we divide it by 12, each hour has 12 teeth and therefore each tooth is equal to 5 minutes!  Really, the clock does not have to have a minute ring at all.  The hour ring can tell you what time it is.

Step 3: Using Inkscape to draw gears.

Inkscape is a wonderful program!  It can be downloaded for free at  Inkscape is a program that is used for vector drawing.  You can think of vectors as ‘drawing lines’ as opposed to bitmapped images such as digital photos.  Just like any new program, Inkscape can be difficult at first, but becomes very easy the more you work with it.

Start by opening Inkscape and creating a new document.  I like to use letter landscape as the document size.  That size fits in our laser cutter well.  File->New->Letter_landscape

From there I find it helpful to turn on a grid.  File->Document Properties Grids tab.  Set your grid to what you feel comfortable using, I like to work in inches, but others work in mm’s.  It really does not matter.

Now the fun part… To put a gear on your drawing, use Extensions->Render->Gear.  When I did this clock I used a circular pitch of 10 and a pressure angle of 10.  Then I varied the number of teeth to set the gear size.  As long as I used 10 and 10 for circular pitch and pressure angle, the gears fit!  Please go ahead and try it!

Once you have drawn a gear, you will most likely need a center hole.  To get a hole centered on a gear, draw the gear and draw the circle for the hole.  Then select both the circle for the hole and the gear and go to Object->Align and distribute.  Then click the icons that say ‘Center on the Horizontal Axis’  and ‘Center Horizontally’.
Schematic Arduino Laser cut gear clock
I have attached my file for cutting the gears.  It is called ClockGear3.svg and you can download it below.   The green lines in the file are lines that I use for guides.  I do not cut anything in green.

The stand is the tall trapazoid and the two triangles.  I hot-melt glued the triangles to the back of the stand.

*** UPDATE 2/29/12 ***
If you try to download the inkscape file, it will download as something.tmp.  Just rename it to clock.svg and then you can open it in inkscape.

[box color=”#985D00″ bg=”#FFF8CB” font=”verdana” fontsize=”14 ” radius=”20 ” border=”#985D12″ float=”right” head=”Major Components in Project” headbg=”#FFEB70″ headcolor=”#985D00″]Arduino

2 small stepper motors

Laser Cutter[/box]

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