With this instructable, you will be able to make your own replica of the PAL Comm unit seen in many scenes of the show Firefly. This instructable includes a instructions of how to install a simple circuit to have the LED light up when the talk button is depressed.
Here's what you will need:
- 3D model files (included in Step 1)
- 3D printer or access to a 3D printing service such as 3D Hubs or Shapeways.
- Exacto Knife
- Hot Glue
- 3 V or greater Battery
- 47 OHM resistor
- Push Button Switch
- 5 mm Red LED
- Heat Shrink
- 9/32" x 2" Compression Utility Spring
- 2 x "6 x 1/4" screws
- 2 x "4 x 3/8" screws
- Crazy Glue
Step 1: 3D Design and Printing
I have designed a replica shell of the PAL unit with assembly pieces close to the way the original was put together.
The push button has a rest/guide to keep it straight. All parts were designed with a 0.2 mm tolerance which is very tight.
- Download the STL files included in this step
- Print out the parts using your 3D printer or upload the files to 3D Hubs to find someone locally who can print it in Black PLA or PETG.
Step 2: Clean Up Printed Parts & Test Fit
Now that the parts are printed, time to clean them up:
- Using pliers and an exacto knife, remove all the support material taking care not to break any pieces you want to keep. An unbent paper clip is a great way to clear out the various small holes in the Top piece.
- Sand any imperfections you want to remove. Especially sand the mating surfaces on the back of the top piece.
Time for a test assembly.
- Starting with the top piece facing downward, place the button into place with the flat edge facing up.
- Then place the back plate on the upper space.
- Then place the back plate 2 on the lower space on top of the button.
- Then the clip will sit on the back plate.
Now you will know how it will assemble and can sand it additionally where it needs more room to fit nice and snugly.
Step 3: Hardware Testing
Time to test the hardware:
- Cut a 9/32" x 2" Compression Utility Spring to 1" length, and test fit it on the button. (Place it on the shaft, and hold the spring back while positioning the button, then let the spring go gently) The button should move in and out freely.
- Screw in 2 x "6 x 1/4" screws at the top of the clip into the back plate
- Screw in 2 x "4 x 3/8" screws at the sides of the back plate, they should grip into the holes in the top piece.
- Loosen the small outside screws in the back plate and remove the plate with the clip.
Step 4: Building Your LED Circuit
Time to build a simple circuit:
- If using a 5 mm LED, you will need to drill out the LED hole in the top piece to 5 mm.
- See the diagram above for the simple circuit which will have a pushbutton switch.
- Cut a small piece of plexiglass the width of the interior of the top piece, and height just smaller than the inside space with the back plate 2 in place. Then drill a hole in the center for the push button to sit.
- Solder wires to the pushbutton switch, apply and melt heatshrink.
- Solder wires to the resistor making sure to place some heatshrink loosely on the wire from the switch. Apply heat shrink to the other wire and melt them both around the fresh solders.
- Solder wires to the LED making sure to place some heatshrink loosely on the wire from the resistor. Apply heat shrink to the other wire and melt them both around the fresh solders.
- Test your circuit with a battery or power supply set to 3 V.
- Place the components in the Top piece with the led in the proper hole and the push button lined up with the printed button, and test the circuit again, this is shown in the video.
Step 5: Affix the Pushbutton Support and Circuit
Time to finish up the internals:
- Wrap up any excess wires with an elastic band.
- Place the push button piece into the top piece, and hot glue it in place as shown in the photos.
- Now all the internals except for the battery will be in place.
Step 6: Final Assembly
Time to finish this thing up.
- Crazy Glue the Back plate 2 into place only applying glue to the outer edge/slot in the top piece. Do not glue the button at all. Let cure. Make sure that the power leads are in the top compartment.
- Attach a small 3V battery to the power leads, and hold them in place with electrical tape.
- Screw the black plate into place on the back of the top piece.
All done! Now you have a replica of the PAL comm unit used extensively throughout the TV show Firefly. And the LED lights up as well, enjoy :)