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

dsc_0683

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.