Just got your LEDI DIY kit, so what’s next? In this page, we are going to show you:

What’s Inside The Bag


You should see the following items in your LEDI DIY kit package:

Name Quantity Description Image
A1 1 32×8 LED matrix pt_ledmtx
A2 1 Connector for LED matrix and PCB pt_conn
B 1 LEDI PCB pt_pcb
C1,C2   Components List  
C3 1 Bluetooth module pt_bt
D 1 AC to 9V DC wall adaptor pt_adaptor

Components List

Name Quantity Description Image
Atmega328p 1 the brain of LEDI, microcontroller with 28 pins pt_mcu
28 pin DIP socket 1 socket for the microcontroller pt_soc
LDO Regulator 1 regulates 9VDC input into 5V or 3.3V pt_ldo
PTC resetable fuse 1 orange ceremic fuse .25A pt_ptc
Crystal Oscillator 1 32.768KHz, silver cylinder shape pt_crystal
Barrel jack 1 connector for AC adaptor pt_barrel
Slide switch 2 on/off, 3.3/5v switch pt_switch
Tactile push button 4 buttons with 4 small legs pt_button
Capacitor 100uF 1 cylinder shape, aluminum, 2 leads pt_cap100
Capacitor 10uF 1 cylinder shape, aluminum, 2 leads pt_cap10
Capacitor 0.1uF 2 blue ceramic capacitor pt_cap01
Zener Diode 3.3v 1 small orange component with black strip pt_zener
Rectifier 1N4001 1 convert AC to DC current pt_1N4001
Resistor 16k Ohms 1 ^strip colors: brown,blue,black,red pt_res16k
Resistor 10k Ohms 3 ^strip colors: brown,black,black,red pt_res10k
Resistor 390 Ohms 1 ^strip colors: orange,white,brown pt_res390
Resistor 330 Ohms 2 ^strip colors: orange,orange,black,black pt_res330
Resistor 300 Ohms 1 ^strip colors: orange,black,brown pt_res300
Resistor 240 Ohms 1 ^strip colors: red,yellow,brown pt_res240
Resistor 15 Ohms 1 ^strip colors: brown,green,black,gold pt_res15
LED Red 1 red LED pt_ledRed
LED Amber 1 oval shape amber LED pt_ledAmber
Piezo Buzzer 1 makes sounds pt_buzz
Header Single row 1 12 pins single row headers for breakout pins pt_header1
Header Dual row 1 2 x 15 header for connecting ribbon cable pt_header2
Jumper Cap 2 Jumper cap to set the jumper pt_jumpcap

Resistors may come in different color and number of stripes depending on manufacturer, the strip color specified above only indicates the resistor value portion. Refer to the Resistor section to understand how to read the stripes value.

If you purchased the acrylic mount, the package should also include:

Name Quantity Description Image
Spacer 1/8" 4 1/8" length nylon spacers pt_spacer2
Spacer 1/4" 4 2/8" length nylon spacers pt_spacer1
Spacer 3/4" 4 6/8" length nylon spacers pt_spacer3
Screw 1-1/2" 4 1-1/2" stainless steel screw pt_screw1
Screw 5/8 4 5/8" stainless steel screw pt_screw2
Nuts 4-40 thread 8 4-40 thread stainless steel hex nuts pt_nuts
Acrylic front plate 1 Transparent acrylic plate for front cover pt_front
Acrylic adaptor plate 2 Transparent acrylic adaptor pt_Aadaptor

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Components Explanation

Before assembly, let’s make sure we have sufficient understanding about the components used in this project.

  • Electrolytic Capacitor (wiki capacitor)


    • Look like aluminum cylinders wrapped in black plastic with one short and one long leg.
    • ORIENTATION MATTERS while you are placing this component on the PCB.
    • The short leg, the side with strip, is the negative (-) terminal.
    • In our PCB, negative terminal connects to GROUND and have a negative sign bar on the PCB. tut_neg
  • Ceramic Capacitor (wiki ceramic capacitor)


    • Unlike electrolytic capacitor introduced above, there is no polarity for ceramic capacitor.
    • Therefore orientation DOES NOT matter.
  • Reverse Voltage Protection Diode (wiki diode) (wiki rectifier)


    • This part looks like a small black cynlinder.
    • It allows current to flow in one direction and not in the other.
    • We are using the popular 1.0A general purpose silion rectifier diode – 1N4001, which serves as converter from AC to DC current.
    • ORIENTATION MATTERS for all diodes. Small white strip on one end indicates the negative side.
    • Aligned with the indicated strip on the PCB silkscreen (white labels on PCB).
  • Zener Diode 3.3v (wiki zener diode)


    • This part also looks like a cylinder, but in orange.
    • Like diode, but allows current to flow in the reverse direction when the voltage is above a certain value.
    • Therefore ORIENTATION MATTERS for this component too.
    • Black strip on one end indicates the "blocking" side. Match carefully this strip with the PCB silkscreen.
  • LED (light-emitting diode)


    • One of the most common parts you can find in electronic kits or even at your local RadioShack.
    • Emits light when current pass through.
    • This part has two legs – one short, one long. Short leg is the (-) terminal.
    • Make sure the shorter leg connects to GROUND.
  • Resistor (wiki resistor)


    • Make sure you are getting the resistor values right by understanding the color scheme.
    • A multimeter would be handy to measure the exact resistance value.
    • Unlike other components discussed, the orientation does NOT matter.
    • You can stick in the resistor in either direction onto the PCB.
    • Refer to the following resistor color code to determine their value:


    For example, on a 5-Band color code resistor, if you see red – yellow – black – orange:

    red   yellow  black      orange
      2        4      0    *     1k   ==  240k

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Tools Required

Now that you understanding the major components going into LEDI, let’s talk about tools that you would need:

Tool The Look
  1. soldering iron
  1. solder (Lead free preferable)
  1. flux (good to have)
  1. digital multimeter (optional)
  1. wire cutter
  1. solder wick (optional)
  1. solder sucker (optional)

The flux, solder wick, and solder sucker are optional. However, they are good tools to help ammend mistakes. If you are soldering for the first time, we highly recommend getting those as well.

Here are the steps we will take

  1. Organize the parts
  2. Solder
  3. Test the circuit
  4. Install the app
  5. Play with it!

If you’ve never soldered before, watch some online tutorials and practice before you go into touching the components. It’s easy to solder but hard to take out sometime. Here are few good online videos:

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Soldering the Parts

Work in a well ventilated room. When we are done with the assembly, your LEDI board will look like this:


Organize and label parts beforehand, here’s how I organized mine before soldering.


As good practice, complete section by section before move to next instead of jumping around the circuit.

LEDI circuit can be roughly divided into 4 sections.


In this circuit, the hardest part is to solder is the SMT (Surface mount) Bluetooth module. It is better to start with it first before the board get overcrowded by other components.

For soldering beginners, it is easier to start soldering with the flattest component first and tallest last. In that case you can rest the board on the desk while soldering without too much wobbling.

Bluetooth module

Flux helps the solder to flow onto the pads easily. You can use it to "tin" the pads by:

  1. Applying little bit of flux onto the PCB pads
  2. Put some solder on the soldering iron, and gently pass it over the pads, at this point, solder flows to the pads and settle.
  3. Once the pads are tinned with solder, set the bluetooth module on top
  4. Touch the pad to reflow the solder onto the bluetooth connection grooves.
  5. Solder just one pad on each side first to hold it in place.
  6. In this circuit, only 11 joints need to be soldered. tut_bt2

Once the bluetooth module is soldered, solder the indicator LED and resistors around the bluetooth module. The headers are optional, if you plan to hack around with LEDI later on.

Power supply circuit

tut_pwr1 – Be careful about the polarity of the electrolyte capacitors, diodes and LED. – The shorter leg is the negative side and should connect to ground which is denoted with a minus "-" sign on PCB. tut_neg

Here’s how I placed the parts before soldering. Notice the legs are bent on the other side of the PCB so that they are held stationary as I solder them permanently in place. tut_bendwire

For the LDO regulator, the flat part should align with the white line at the silk screen. tut_pwr2

Zener diode voltage regulator circuit

It’s crucial to get the right components in this section. We need a 15 Ohm (not 15k!!!) resistor, a zener diode, and a 0.1uF capacitor. As a reminder, resistor strip colors are:

  1     5    0     x0.1   ==  15 ohm
brown green black  gold

Make sure you align the black strip on zener diode with the white line on the PCB as indicated here:


  • The push button allows you to reset the bluetooth module.
  • Optionally, add the headers for access to the bluetooth module’s UART ports.
  • Test the circuit by powering it on with the AC-9VDC adaptor plugged in.
  • If the indicator LED near the bluetooth module blinking, that mean you are on your way to getting it successfully built!
  • If not, check your components and make sure you soldered the parts correctly.

Atmega328p microcontroller and headers

This is the easiest part of the circuit. You have one pull up resistor (10k ohm), 3 buttons, watch crystal (32.768kHz) and IC socket. Insert the microcontroller into the IC socket once everything is soldered in place.


  • The 2×3 header on the bottom right corner is a must if you plan on flashing the firmware.
  • By default, LEDI come preloaded with the most recent firmware.
  • If you plan on doing firmware development and modify functionality, solder the 2×3 header there.
  • The 1×8 header gives you access to unused I/O pins on the microcontroller.
  • Solder the 1×8 header if you want to make LEDI interface with other electronics.

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Testing the Circuit

  1. Connect the board with the wall adaptor. Switch the power to on. The power LED (yellow) should be ON indicating the circuit board is powered. The red LED should be blinking indicating the Bluetooth module is ready to be paired.
  2. If this step is good, then we are ready to connect it to the LED matrix. Switch the LEDI off, unplug the adaptor first to be safe.
  3. The ribbon cable has a red strip on one end. It denotes the first pin. Align this with the CS1 pin labelled on the board.
  4. Add the jumper cap to complete the Bluetooth module and the microcontroller circuit.
  5. All the LEDI chips are pre-flashed with updated firmware, but if you want to do it yourself or flash the firmware later on, you need to use a programmer like (little wire).

The PCB side of the ribbon cable connection looks like this:


Connect the other side of the ribbon cable to the LED matrix. Make sure your DIP switch on the LED matrix board is set to have 1 (on) and 2,3,4 (off). It looks like this: tut_ledmtxBack

Once connected, time to power it on again. Did you see the sign "LEDI" on the LED matrix board? If so, congratulations! You have successfully assembled LEDI.

If you are not using the acrylic mount, then you can go directly to the `next step<http://techversat.com/projects/ledi/operating-ledi/>`_, to install the LEDI app on your android phone to start playing around with it.

Assemblying the Acrylic Mount

Now that the PCB and LED matrix work well, time to put a little cosmetic on it. Depending on your personl preference, you can

  1. Just leave the parts on your desk.
  2. Put the parts together with our customed made acrylic mount.
  3. Use bricks to make the LEDI into a piece of artwork.
  4. Or even print your own mount or enclosure if you have a 3D printer.

If you opt to use our customed made acrylic mount, below is the detail instruction for the assembly.

List of parts:

Index Name Quantity Description Image
A Spacer 1/8" 4 1/8" length nylon spacers pt_spacer2
B Spacer 1/4" 4 2/8" length nylon spacers pt_spacer1
C Spacer 3/4" 4 6/8" length nylon spacers pt_spacer3
D Screw 1-1/2" 4 1-1/2" stainless steel screw pt_screw1
E Screw 5/8 4 5/8" stainless steel screw pt_screw2
F Nuts 4-40 thread 8 4-40 thread stainless steel hex nuts pt_nuts
G Acrylic front plate 1 Transparent acrylic plate for front cover pt_front
H Acrylic adaptor plate 2 Transparent acrylic adaptor pt_Aadaptor


  1. Assemble the PCB with the two adaptors, keep antenna end on top and leave more space at bottom for the cable. (Click to enlarge image) tut_mount1
  2. Assemble the rest according to the sequence below :tut_mount2
  3. Plug in the serial cable from LED matrix to PCB.

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Docutils System Messages

System Message: ERROR/3 (<string>, line 348); backlink

Unknown target name: "next step<http://techversat.com/projects/ledi/operating-ledi/>".