Week 13

Input Devices

The objective :

Measure something: add a sensor to a microcontroller board that you have designed and read it. I decided to make the microcontroller board with a switch that I may use it for my final project.

What is the Switch?

Its is an electrical component that can "make" or "break" an electrical circuit, interrupting the current or diverting it from one conductor to another. wikipedia

Some information about the input devices that I may use in my final project :

1.Electrical temperature sensors :wikipedia

Thermistor- Thermistors are thermally sensitive resistors whose prime function is to exhibit a large, predictable and precise change in electrical resistance when subjected to a corresponding change in body temperature. Negative Temperature Coefficient (NTC) thermistors exhibit a decrease in electrical resistance when subjected to an increase in body temperature and Positive Temperature Coefficient (PTC) thermistors exhibit an increase in electrical resistance when subjected to an increase in body temperature

2.Light sensors :

A Light Sensor generates an output signal indicating the intensity of light by measuring the radiant energy that exists in a very narrow range of frequencies basically called “light”, and which ranges in frequency from “Infra-red” to “Visible” up to “Ultraviolet” light spectrum (source)

Tools :

A.Designing :

As I followed the same procedure that did in weeks 6 in designing the my board in Eagle.

Components used in redesigned:

1.Attiny45

2.10K resistor 

3.1uF capacitor 

4.6mm Switch 

5.AVR ISP  

6.FTDI SMD header 

I used label method in connection

Here is my final design before I sent it to the milling machine

Download (.brd , .sch, .cmp)

B.Milling & soldering :

As I mentioned above this process has been done many times in previous weeks. Before starting milling the board I did the calibration process exactly as I did in week6 and then tested the connectivity of my PCB by using Multimeter to ensure that the board is ready for soldering after that only I did the soldering.

Ready for testing

B.Programin & testing :

                        /*

  DigitalReadSerial

 Reads a digital input on pin 2, prints the result to the serial monitor

 This example code is in the public domain.

 */

// digital pin 2 has a pushbutton attached to it. Give it a name:

int pushButton = 2;

#include<SoftwareSerial.h>

SoftwareSerial mySerial (2,5);

// the setup routine runs once when you press reset:

void setup() {

  // initialize serial communication at 9600 bits per second:

  mySerial.begin(9600);

  // make the pushbutton's pin an input:

  pinMode(pushButton, INPUT);

}

// the loop routine runs over and over again forever:

void loop() {

  // read the input pin:

  int buttonState = digitalRead(pushButton);

  // print out the state of the button:

  mySerial.println(buttonState);

  delay(1);        // delay in between reads for stability

}