Introduction: Time Measure (Tape Measure Clock)
For this project, we (Alex Fiel & Anna Lynton) took an everyday measuring tool and turned it into a clock! The original plan was to motorized an existing tape measure. In making that, we decided it'd be easier to create our own shell to go with the electronics. We motorized a tape measure and programmed it to move over the course of the day to show the time in hours (inches).
To keep the whole project looking as best it could, the largest challenge became minifying the electronics and keeping the overall footprint of the device to roughly the size of the real object.
Supplies
Electronics
Stepper Motor H-Bridge Chip x1
12v 1A Adaptor x1
Tiny Limit Switch x1
6mm (diameter) x 3 mm Magnetsx6
6mm Ball Bearings x(3-10)
A couple loose Male / Female Headers
Wire
Soldering Iron
Finishing / Case
3D-Printer (or access to one)
Bondo Auto Body Filler
Silver Spraypaint
Black Spraypaint
Yellow Spraypaint
Vinyl Cutter (Or access to one)
Autodesk Fusion 360 (if you want to make tweaks to the model)
Step 1: Circuit & Code
The circuit is fairly simple. The attached wiring diagram lays out how the RTC Chip, H-bridge, Motor and limit switch all integrate into the circuit. The complicated part is ensuring it all fits inside the spool and surrounds the stepper motor. See the close-up picture of the spool to get a better idea of the space we're working with. For this, it was easiest to use solid core wire bent and cut to the exact length it needed to be, then hot glue it down after it was soldered together. Solder male headers to the power and ground for the board and the motor.
Upload the code to the board. The code is fully commented, explaining how the homing function works and how functions are called. Code can be found on Github gists:
Step 2: Power Supply
Next, you will need to make the power supply. We found that we could not supply consistent power by from the 12V supply split between the stepper motor and the board.
We ended up solving it by taking apart a 12V power supply and a buck converter to have a constant voltage for the Arduino and still have 12v for the stepper (Not sure it's the best way... but it worked!). Then, we ran four long wires (Vin for the stepper, Vin for the board, and ground for each to the measuring tape. Add female headers to these wire and heat shrink them together for a nicer finish!
Step 3: 3D Printing
For the Measuring Tape:
All the files are over on Thingiverse; printed in the correct orientation, the outer case and stepper wheel should require support material. For our prints, knowing we were going to have to do post-processing either way, we printed the cases with the outsides down touching the support.
We assembled the spool by using a soldering iron to melt the component parts together. Then the ball bearings can be put in the channel of the right side body and to check how the spool rotates.
For the power supply:
Then, you can 3D print a new case for your updated power supply with the Power Supply files. We hot glued the prongs in place on the inside and then glued the two halves together.
Step 4: Finishing & Painting
Glue the magnets into the holes on the inside of the case.
After gluing in the magnets to the holes in the case, and checking the fit, it's time to do the finishing.
When creating / finishing the case, you can really do as much or as little as you want to. For this project, we were trying to make the tape measure look as realistic as possible. To that end we spent a lot of time applying Bondo, sanding, and then repeating that process before applying the silver spraypaint. We used painters tape to mask areas we didn't want to paint and added yellow accents. You can paint the case however you want!
Using a vinyl cutter, we cut out a circular logo for the outward-facing side. Again, design the outside as you choose!
Step 5: Putting It All Together
Put the ball bearings in the tracks on the inside of the case and insert the stepper motor with the components soldered around it. Plugin the female headers from the power supply to the male headers coming from the stepper and board.
Take the measuring tape and wrap it around the center spool. We added a piece of tape to hold on the start of it to prevent slipping. Attach the spool to the stepper motor inside of the tape measure.
Snap the two halves together and plug it in and you're good to go! As shown in the video, the tape will home and then extend to display the current time.
Second Prize in the
Clocks Contest
