Arduino Mini-Shields

When all was said and done, I built 7 of these mini-shields. I just kept digging through my spare parts and finding things I could make another board out of. These are the current mini-shields and the main parts that go into them:

Headers
I made all of these mini-shields with parts I had on hand but I hadn’t gotten a chance to use. I always keep a lot of male and female headers on hand. More and more, I like to use these right angle headers which only come as male headers, but I have found you can also bend the pins on the female headers to make them lay down along the board as well. I like the 10 packs of straight and right angle headers that they sell at Schmartboard. Most other places only sell the header strips in singles. Unfortunately, they don’t sell the female headers there.

Perf and Proto Boards
I bought a couple of 2 sided, through-hole plated proto boards that I never found a use for. This project gave me a good chance to use them, but once I used the 2 I had, I started cutting pieces off a large perf board that I got at Radio Shack.

Resistors, Capacitors and Components
At some point I stopped buying one type of resistors and I started buying the assorted packs. It’s a much better deal and it’s more convenient to use something you have on hand than to run to the store and hope you remember all of the things you needed. If you have a bunch to choose from, you can usually mix and match something to work for you.

Buttons
I have been using a lot of buttons lately, and I ran out of new ones but I had a bunch that I salvaged out of an old DVD player so I was able to reuse those as well. When I junk old electronics, I open them up to see what could be useful. If I find anything good, I cut the parts out with a pair of tin snips and put them away. If I need them later, I will use some desoldering braid to remove the solder and free the part from the circuit board. I used the same process for the buttons, the IR LEDs and the IR sensor that I used in this project.

My Method
The wire I use in my projects is just solid core UTP network wire. I have a big spool of wire, so every so often I cut a few feet off and strip off the outer sheath. The wires inside use the standard CAT5 standard, so I don’t have red and black wires like I would prefer. Instead I use Orange for Red and Green for Black. I use Blue for switches and other digital pin leads. I use White Blue or White Green for data and analog pin leads.

Header Markings
I used some paint pens to mark the header pins with colors so you can easily tell what pins are necessary and how they should be hooked up to an Arduino from a breadboard. I marked the 5v pins with Red and the GND pins with Green. I marked digital pins with Blue and I marked analog pins with Yellow. I marked the PWM (digital) pins with White, but I put a dot of color in the middle. For the Full-Color LED, I matched the dot to the color that the pin relates to on the LED. I mark the female header pins with white masking tape and fine tip permanent markers using the same color scheme as above.

Step 2: IR Mini-Shield Construction

I had another of these 9×9 through-hole plated proto boards so I figured I would make another module that I could use in the same port. I have a section of one of my breadboards devoted to a hardware debounced switch. This way I can hook the switch up to the hardware interrupt on Arduino and begin a new instruction in the middle of a loop. The interrupt pins need to be debounced with hardware because there is no way to use the wait delay to debounce on the interrupt.

There is a really good explanation of hardware debouncing and interrupts on these websites…
http://www.jeremyblum.com/2011/03/07/arduino-tutorial-10-interrupts-and-hardware-debouncing/
http://arduino.cc/en/Reference/attachInterrupt#.UyXvl4XLIyz

Since the original idea was to add some new inputs for my Time & Temp shield project, I thought a directional pad would be nice. I remembered this post on the Arduino site that only uses 1 analog pin for all of the buttons. Because the resistances are mapped out so nicely, it even allows for the Arduino to recognize combinations of any 2 keys pressed at the same time.

I was trying to use parts I had on hand and I was running out of buttons, so I had to salvage 4 of these buttons from the A/C unit’s control panel. I have a set of standard resistors from Radioshack that is getting a little picked over, but I was still able to make something work by combining a few resistors to get the desired resistance.

I had to use 4 resistors for buttons 2 and 3 to make the 390 and 680 values described in this example, and as a result my actual resistance was slightly different, so I had to run the following test code to see what the analog reading would be for each button, and update the button array to allow for these values (usually 1 number above/below the example on the Arduino site).

Test Code:

int analogpin = 3; // analog pin to read the buttons

void setup()
{
Serial.begin(9600);
}

void loop()
{
Serial.println( analogRead(analogpin));
}