Building the GlowSaber main board

All the logic, sound and light effects of the GlowSaber are performed by a small microprocessor board. In this tutorial I will explain, step by step how to put together the main board of a GlowSaber.

Where do I find the parts?

This is an open source project. In 2014 we ordered enough parts to build 60 GlowSabers, and we still have enough parts to build about 20 more. All the parts and PCB’s are available from this site while they last, but you can also order them from the same manufacturers and distributors that we use. Ordering from us has the only advantage of getting everything in a single place.

At the end of the article you will find the links to all the providers, as well as links to the GitHub code repository.

Bill of Materials

  1. The printed circuit board. 
    dsc_0572
  2. (1) 470Ω 1/4 watt resistor and (1) 220Ω 1/4 watt resistordsc_0627
  3. (4) 22Ω 1 watt resistorsdsc_0588
  4. (2) 100 μ farad capacitorsdsc_0590
  5. (1) LM7805 5 Volt regulatordsc_0591
  6. (1) ULN2003A  7-Darlington Transistordsc_0654
  7. (1) Adafruit Triple-Axis Accelerometer – ±2/4/8g @ 14-bit – MMA8451 PID: 2019dsc_0651-crop
  8. (1) Adafruit Pro Trinket – 3V 12MHz PID: 2010dsc_0649-c
  9. (2) Eight right angle male header connectors.dsc_0636-c

Put everything together

1. Voltage divider resistors

The 470Ω and the 220Ω resistors are a voltage divider that the code uses to monitor the health of the battery. When the battery voltage is too low the program will shut down the RGB LED and the sound. Although monitoring the battery for normal AA disposable batteries is not critical, it could be if you decide to power your GlowSaber with rechargeable nickel metal hydride or lithium ion (Li-Po) batteries.

As these two resistors are positioned to be under the microprocessor board, it is required that they are as close to the PCB as possible.

Resistors do not have polarity and can be connected either way. dsc_0660

2. LED and speaker resistors

The 22Ω resistors control the amount of current that pass through the RGB LED and the speaker.dsc_0664

3. 5 Volt Regulator

The 5 Volt regulator may need to dissipate heat, and for that purpose all the ground copper in the top layer of the PCB is connected to the heat sink of  the regulator. A 1/4 inch 2-26 screw and bolt help to keep a good heat flow.
dsc_0667

4. 100μf Capacitors

These two capacitors help to regulate the initial current demand from the RGB LED. As these are electrolytic capacitors they are polarized and can be damaged if connected backwards. Make sure that the long lead goes to the round soldering pad and the short one goes to the square soldering pad. The capacitors have a silver strip running the length of their body. That is the negative side of the capacitor. When properly connected the silver stripes face each otherdsc_0674 dsc_0676

5. ULN2003 A

This array of transistors drive the current to the RGB LED and the speaker, effectively working as a current amplifier for the signal the microprocessor sends. Notice that the chip has a notch. The PCB outline for the chip is interrupted. The notch must face the outline interruption, as you can see in the picturedsc_0679-c

6. Accelerometer

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7. Processor

Notice that the Pro Trinket 3V3 has two additional headers. They are to connect A6 and A7 two additional analog ports in the Pro Trinket. A7 is used by the GlowSaber to measure the battery voltage.dsc_0689

8. Connector headers

There two sets of connectors. One goes to the switch assembly and the battery, the other to the RGB LED and the speaker. Although they could go either on the top or the bottom of the board, they will fit better in the hilt if they go on the topdsc_0695-2016-09-11_17-41-42-864

9. Clean the board.

Solder rosin residues on the board will show as a white dust on top of the soldering spots. It could be slightly corrosive and is better to clean it up. An old tooth brush with some dish detergent will remove all the residual rosin from the board. Just put a couple of drops of the detergent on the brush, and brush the circuit with it and water. Let it dry thoroughly before making any electrical connections.

Links to parts:

All the parts can be ordered from this site.

OSHPark

OSH Park is a community printed circuit board (PCB) order. They do a great job and have reasonable response times. You can find them here

You will find the PCB for the GlowSaber here: OSHPark – GlowSaber. Notice that the minimum order is three PCB’s

adafruit

The triple axis accelerometer and the Pro Trinket 3V3 can be ordered from adafruit.com

Digi-Key

Digi-Key is an electronic parts provider. The good thing is that you can order items in very small quantities, even only one. Almost all the parts for the GlowSaber were ordered from this site. You can find the order for the GlowSaber parts here

What else?

This article describes how to make the main board for the GlowSaber. In addition you will need:

  • The switch assembly
  • The RGB LED assembly. Found a description here
  • Cables to put all together
  • The handle. Found a description here
  • The code for the GlowSaber is in GitHub: GlowSaber code
  • For a limited time I will offer the parts to build a GlowSaber, including the Handle, light emitter, LED assembly and Switch assembly. I will only charge my cost and after my inventory is exhausted I may not replenish it. If you are interested please send an email to: Carlos.Vadillo@gmail.com. Please put GlowSaber in the subject.

 

 

Building the GlowSaber handle

Design constrains

One premise that I had while designing the GlowSaber was that I should be able to build all of it with tools that I already have. That limited the materials I could choose to those that I could cut, drill and glue with just the basic tools:

  • Miter Saw
  • Drill press
  • Dremel hand held tool
  • Hand drill
  • 4-40 Drill and Tap kit

The choice of materials included several plastic materials, PVC piping, copper piping and aluminum piping. The last two were immediately discarded as they are very expensive and not easy to find in the dimensions the GlowSaber required.

A quick visit to the Tap Plastics web site showed me that the only adecuate material would be Poly-carbonate. It has excellent strength characteristics and is very easy to cut using a miter saw. However, there are only transparent pipes and that did not see appealing for the GlowSaber handle, although it makes a perfect material for the blade. Is light and impact resistant.

That left PVC as the material of choice. It is available in any hardware store and if you go to Home Depot you can buy two foot segments at a reasonable price. More than that, it has a great variety of connectors that can be used to transition from the diameter of the handle to the diameter of the blade.

When I put the circuit board and the battery pack together I found that the smallest internal diameter pipe that I could use was 1.25 inches. PVC pipes are sold in 1/2″, 3/4″, 1″  1-1/4″, 2″ and so on. The 1 1-4″ nominal internal diameter is actually 1.4″ inches and that gave some extra room to put everything together.

It took several iterations to design the handle, and eventually I arrived to this simple design:

handle

It has three slots. The one in the front will allow the installation of the switch assembly and the two slots in the back allow to secure the speaker with a plastic tie. More on this in the assembly guide.

Bill of Materials

I bought all the PVC at Home Depot:

  1. A 2 ft. length of 1-1/4″ pipe. This is enough to make two handles
  2. A 2 ft. length of 1″ pipe. If you can get a smaller size go for it. You really only need about 4 inches total.
  3. One 1-1/4″ coupling.
  4. One 1-1/4″ to 1″ reduction
  5. One 1-1/4″ end cap.
  6. A small amount of PVC cement.
  7. Two 3/4″ 4-40 bolts
  8. Four 5/8″ 4-40 bolts

The firs few handles that I build were made with plumbing grade PVC. Then I found Formufit, a furniture grade PVC provider. They sell very attractive PVC pipes in various colors. As I was going to make many GlowSabers I did not mind buying 8 foot long pipes, and at that time they did not sell shorter segments. Anyhow, check their site: Formufit

Cutting the pieces

I start cutting the 1-1/4″ pipe. The design calls for a 9-3/4″ long:

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Next cut the 1″ pipe. You need two lengths on of 2″ and another of 1″:

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All the pieces together:

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From the back, left to right: 9 3/4″ long by 1 3/4″ diameter pipe, the 1 1/4 coupling, the 1 1/4″ to 1″ reduction and the end cap. In the front a 2″ long by 1″ diameter pipe and a 1″ long by 1″ diameter pipe.

You may want to sand some of the markings in the couple, reduction and cap. I use a grit #80 sandpaper to remove the markings. Then I use 200 and 400 grit sand paper to make the PVC smooth. Anyhow it will be painted and the paint will cover the small scratches from the sand paper:

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Machining the handle.

Next step is to drill guide hole for the slots. This PDF file has a template to cut and put on the pipe and the couple: Handle and Light emitter templates

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The top design is for the pipe, and the bottom one for the couple. Let’s start with the pipe template. Once it is cut you can tape it to the pipe as follows:

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Drill the three holes with a 1/8″ bit. Then use a Dremel rotary tool to machine the slots from the holes to the top of the pipe. Last drill a 3/8″ hole in the front slot:

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A Dremel rotary tool can be hard to control by hand for this job. I have a small router table for it. Still is a hard job to do. However the slots are not going to be visible and if they are not perfect it really does not matter.

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Assembling the light emitter

The 1-1/4″ couple, the 1-1/4″ to 1″ reduction and the two segments of 1″ pipe will make the container for the RGB LED and the base for the blade.

First we insert the 2″ x 1″ piece into the 1-1/4″ to 1″ reduction.
Use the screw vise to press the pipe into the reduction. The reduction has a small ridge half way. Make sure the you don’t press beyond that or you will add too much stress to the pipe and the reduction and they can break.

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Now use the 1″ x 1″ pipe and glue it on the other side of the reduction. Use PVC cement and make sure the the 1″ hole are perfectly aligned:178

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Let the PVC cement cure for at least 10 minutes before proceeding. Once the pipe is firmly attached we will complete the light emitter by inserting the reduction into the couple:

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Be gentle when you are pressing the reduction. Slow is better.

Once the reduction is in place you can cut a put the screw pattern on the light emitter. Then mount the emitter on top of the handle, making sure to align one set of screws with the front slot:

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The next picture shows the couple on top of the handle. When I after I took the picture I realized that the pattern was upside down. I corrected it and drill the holes. I used a 1/16 drill bit to be able to tap a 4-40 thread on the holes.

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The finished handle with the light emitter bolted in place. The two screws on the front will secure the switch assembly. The top screws secure the blade, and the bottom ones secure the LED assembly.

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The 3/4″ 4-40 bolts go in the front, as they need to hold the switch assembly.

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The only step missing is to screw the cap at the bottom. If you go to Formufit you can get nicer end caps than the plumbing ones:

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This cap does not need screwing. You just press it into the pipe and it will stay in place.

The next picture is a full handle, using Formufit PVC. The light emitter can be painted with Krylon paint. This particular handle has the light emitter cover with PVC film, also by Formufit.228

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