I’m happy to finally announce my new product, the EZ-Expander shield. After several months of hard work of sourcing parts, designing the PCB, and setting up a store, my first product is now available for purchase in the nootropic design store!

For all the technical details, go to the EZ-Expander page.

EZ-Expander shield

EZ-Expander on an Arduino

Difficulty Level = 4 [What’s this?]

This is an amusing project inspired by flashing blue and red lights on police cars, ambulances, etc.  This is a perf board Arduino with 5 blue and 5 red LEDs, and the Arduino code lights them up in a pattern similar to police lights.

First, the Arduino built on a perf board.  It’s not hard to build your own Arduino.  I use a real Arduino board to upload code to the ATMega328 chip, then just move it to the project board.

Perfboard Arduino with blue and red LEDs for police lights mini-project

Now here it is in action — I really think if you don’t know what you’re looking at, it looks realistic in the dark.

Here’s the code that makes it work. Notice that some of the LEDs are controlled using PWM; the second and fourth LED in each of the blue and red groups. I would invite people to build something similar and tweak this to get the most realistic effect possible!

#define NUM_OFF 3
#define DELAY 50
#define PWM_MIN 10
#define PWM_MAX 128

int blue[5];
int red[5];

void setup()
{
  blue[0] = 19;
  blue[1] = 5;
  blue[2] = 18;
  blue[3] = 6;
  blue[4] = 17;
  red[0] = 13;
  red[1] = 11;
  red[2] = 12;
  red[3] = 10;
  red[4] = 9;

  for(int i=0;i<5;i++) {
    pinMode(blue[i], OUTPUT);
    pinMode(red[i], OUTPUT);
  }
  randomSeed(analogRead(0));
}

void loop()
{
  allOn();
  analogWrite(blue[1], random(PWM_MIN, PWM_MAX));
  analogWrite(blue[3], random(PWM_MIN, PWM_MAX));
  analogWrite(red[1], random(PWM_MIN, PWM_MAX));
  analogWrite(red[3], random(PWM_MIN, PWM_MAX));


  for(int i=0;i<NUM_OFF;i++) {
    digitalWrite(blue[random(5)], LOW);
    digitalWrite(red[random(5)], LOW);
  }
  delay(DELAY);
}

void allOn() {
  for(int i=0;i<5;i++) {
    digitalWrite(blue[i], HIGH);
    digitalWrite(red[i], HIGH);
  }
}

Difficulty Level = 6 [What’s this?]

After tearing down an old CD player, I was inspired by the CD laser scanning assembly to build a door lock for my subterranean lab. The assembly has two motors: one for turning the CD (I’m not using this one) and one for slowly moving the laser across the CD’s surface. This second motor provides a nice linear motion that I wanted to use to build an electronically-controlled dead bolt lock for my lab.

Here’s the assembled lock. The circuit board in the middle is an H-bridge circuit I built to allow the motor to move in both directions. There are two position sensing switches so the Arduino senses when the motor has reached its limit in either direction. A 9V power supply powers the Arduino board, and a separate 5V supply drives the motor through the H-bridge. The dead bolt is literally a bolt — connected to the assembly with a piece of scrap circuit board — that travels through the door jamb and into the door.

The lock in the closed (locked) position.

The black CAT5 cable connected to pins 2-8 goes through a small hole in the wall (under a desk) to the keypad on the outside of the lab (I wasn’t sure I wanted to permanently mount the keypad in the wall). The user types in the correct code and presses the # key to open or close the lock. The green LED indicates the door is unlocked. Red indicates locked.

Lock keypad - green indicates that it's unlocked, red indicates locked.

Let’s see the lock in action. (While recording, I gave instructions to my son to lock and unlock using the keypad off camera.)

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