Gather the materials below and get ready to set up the PCB for the Thimble MIDI Piano
|Multiplexer 16DIP Package||3|
|LED 3mm Green||1|
|1x10 Female Socket Stackable Header||1|
|1x8 Female Socket Stackable Header||2|
|1x8 Female Socket Header||3|
|1x6 Female Socket Stackable Header||1|
|Small Tactile Button||1|
You can set two of the multiplexers aside as we won't be using them in this tutorial until we go over expanding your device
Tools you'll need
Start with the first multiplexer area on the PCB, **MUX0**. Take one of the multiplexer chips and inspect it with the pins facing downwards. This is the top-down view. Two defining features are a small "U" shaped indent on the short end of the package, as well as the lettering on the top. The indent marks the top orientation of the package and pin 1 is located to the left of the U shape when looking at the package from the top-down view.
When inserting the chip into the printed circuit board (PCB), the "U" shape should be on the side closest to the label MUX0 with it's Pin 1 being closest to this silk screen indent. Press the chip into the PCB.
For the purposes of this tutorial, we will only solder the first multiplexer. If you wish to extend the midi device later, the two other multiplexers can be added.
Once the Multiplexer 16DIP package is fitted into the correct holes, remember to press against the top of the DIP package while you solder a single pin to make sure the chip is all the way in. Check the top of the board to confirm the chip is flat. Then solder the rest of the pins.
The next component that can be soldered are the resistors, there are three 10k resistors and one 200 Ohm resistor. Make sure to verify the correct resistor value goes in the correct place.
If you are unfamiliar with how to read a resistor's color-coding, see this page. The 10k-ohm resistors are Brown-Black-Orange-Gold. The 200-ohm resistor is Red-Black-Brown-Gold. There are a number of online calculators for decoding the color codes.
It may help to bend the leads of these components into a U shape before putting them in the PCB. Place the three 10k resistors through the top right corner of the PCB and bend the leads back to hold them in place. Then place the remaining singular 200Ohm resistor in the label marked R2 at the bottom of the PCB. Resistors have no polarity; you can put them in either direction. Solder and trim the resistors leads.
Place the small tactile button through the holes on the area labeled SW1. Push the button through the holes until it sits flat. Turn the PCB over and solder the leads on the other side, but there is no need to clip them.
This LED is used during calibration of the piano, and will be your indication of the steps. The calibration process of the piano will be explained in software section when it becomes necessary. The LED (Light Emitting Diode) is a polarized component, meaning that there is a particular way to connect it. unlike resistors that can be soldered in either way. Examine the LED, there is normally two indicators for which side negative on a LED: the length of the leads and the shape of the plastic dome on the LED. With the leads, the shorter lead is the negative side; By chance a LED's leads are the same length, a flat side on the base of the plastic dome indicates the negative side. On this small 3mm LED the flattened side may be hard to see. Place the LED in the area marked D1, orienting the short lead into the square hole labeled negative. The Solder and trim the leads.
Take the headers and organize them by pin number, setting aside the three 1x8 Headers with the short leads. The headers with the short leads fit into the center of the PCB, with rows of holes labeled MUXP0, MUXP1, and MUXP2. All other headers fit into the rows on the top and bottom.
If you look closely at the row of holes along the bottom of the PCB and you will notice they don't line up perfectly. This feature was added to help hold the header pins when soldering by applying slight pressure to both sides.
Place a header leads down into the PCB, and solder one pin first to confirm the header is set correctly. You want to be careful to solder the header straight so the leads aren't bent or not fully in. When you are sure it is set properly, solder the rest of the pins. Do not trim any of the leads. Complete the rest of the headers in the same way as the first one. Small lead headers not included, once you are done you will be left with half of headers that will go into the uno to extend the pinouts. Set these aside for later.
At this point only one mux is soldered on, this is ok, the others can be added in the future for expansion. Leave these unsoldered for now, expansions can be bread boarded first to test them out.
Completed shield with only 1 mux
The Shield is complete we can get to work on assembling the sensors.