Ultrasonic distance measurement

Playing with the LV-MaxSonar-EZ1 together with Arduino. Wonderful self-contained module only requiring +5V and GND connections.

LV-MaxSonar-EZ1, PWM output connected

PWM output, 9.8ms @ 2 meters

Data captured varying distance between 2 meters and 10cm

soundTrigger rising

Playing with an electret microphone and a simple circuit.
A Mega328 samples the noise generated by the circuit and triggers a camera on the output via an opto-isolator.

Schematic in Eagle

Bread boarded Prototype

Measuring I/O performance

Performance looks promising. Measuring a triggering delay of 35uS (microseconds).
Arduino sketch to follow...

New light detector circuit

Prototyping the new light circuit on breadboard. Everything is working well so far.

Circuit detail (Transistor is wrong type but the correct footprint for the PCB)

Output in dim light is about 0.13V going up to just over 1V with an inspection lamp close to the transistor.

Photo Transistor

Low Power Op-Amp

This circuit will form the second PCB in a two stack design. Interconnects will be via pin headers (0.1") and power will be from a CR2032 3V coin cell battery.

The prototype PCB will be mostly SMD tech with the photo transistor and pin headers being through-hole.

Bit of code that just works...

/*
StormTrigger V3 30-07-2013
 */
#define FASTADC 1
// defines for setting and clearing register bits
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif

#define LIGHT 0
#define OUT_FOCUS 2
#define OUT_SHUTTER 3
#define LED 13
int trigVal = 0;

void setup() {

#if FASTADC
  // set prescale to 16
  sbi(ADCSRA,ADPS2) ;
  cbi(ADCSRA,ADPS1) ;
  sbi(ADCSRA,ADPS0) ;
#endif
  pinMode(OUT_FOCUS, OUTPUT);
  pinMode(OUT_SHUTTER, OUTPUT);
  pinMode(LED, OUTPUT);
  PORTD = B01010000;
  // calibrate sensor to just above ambient reading
  int ambVal = analogRead(LIGHT);
  trigVal = ambVal + 40;
}
void loop() {
  //read light level
  int lightVal = analogRead(LIGHT);
  //compare light reading to trigger value
  if (lightVal >= trigVal)
  {
    //trigger camera
    PORTD = B00101100;
    delay(15);
    PORTD = B01010000;
    digitalWrite(LED, HIGH);
    delay(30);
    digitalWrite(LED, LOW);
  }

}

Program TQFP32 MEGA328P (Arduino)

A quick look on the web reveals a lack of ways to get a bootloader onto an MEGA328P AU in TQFP32 SMD package.

Atmel have a board available for their STK600 development kit (Atmel.com). With some modification the board can fit to an Arduino on the standard headers, and have bootloaders burned easily.

A good alternative is available on ebay (here). However you will need to add a PCB to adapt to Arduino headers.

Oscillator circuit (crystal, capacitors and resistor) connected to xtal1, xtal2 and GND.

Birdsnest of interconnecting cables from the Arduino headers.

Closeup of MEGA328P in place for programming

Remove the MEGA328P from the Arduino

Mount the AVR board to the Arduino

Hook up the set via USB to your PC then use the following to program the TQFP32 MEGA328P

That gets the bootloader onto the chip.

You will need to include a header on your PCB to access TX, RX, RESET, 5V and GND to program the MEGA328P from the Arduino environment, using an Uno to pass-through the signals, or a standard ICSP header for programming via Atmel Studio and an AVRISPII.

Playing with Bluetooth

Baby steps in development of bluetooth limit switches for CNC.

Materials used:
Arduino Uno
BlueSMiRF Gold
Breadboard & 4 connection wires
Android phone with Android Bluetooth Terminal installed

Code:
// basic Arduino sketch to demonstrate output based on serial data received from bluetooth
// the Arduino does not know this is Bluetooth, only that it is serial comms
// connect bluesmirf to VCC, GND, TX and RX

void setup(){
  //configure serial at 115200 baudrate
  Serial.begin(115200);
  //set arduino led on pin 13
  pinMode(13, OUTPUT);
}
void loop(){
  if(Serial.available()){
    //if serial comms are established, read characer received
    unsigned char charreceived = Serial.read();
    
    //determine operation based on character received
    switch(charreceived){
      case 'a':
        digitalWrite(13, HIGH);
        Serial.println("Pin 13 Led On");
        break;
      case 'b':
        digitalWrite(13, LOW);
        Serial.println("Pin 13 LED Off");
        break;
      case 'c':
        digitalWrite(13, HIGH);
        delay(1000);
        digitalWrite(13, LOW);
        Serial.println("Pin 13 LED Blink 1 second");
        break;
      default:
        break;
    }
    //we only want first character so flush remaining characters
    Serial.flush();
  }
  delay(10);
}

After pairing the phone with the bluesmirf, entering either text "a", "b" or "c" will affect the LED on Pin 13 of the Arduino, and will provide feedback to the phone.

Version 3 - New Design

Hotshoe mounted
Built-in sensor
Coincell battery operation
Single LED feedback
Automatic setting & operation

35mm x 25mm x 15mm volume to work within.

Shown is the enclosure mounted on 7D.

Stacked PCBs. One uC PCB and one I/O PCB with a board interconnect.