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Let’s invent something. Right. So that was the assignment. I decided to fix a quite trivial problem; my disorganized mornings, and more specifically create a device that would make sure that my purse contains everything it should contain when I go out the door. Like my keys:

By adding RFID-tags to my keys, phone, wallet etcetera, and have sensors by the door opening, I could get information about whether the items are in my purse or not. My very simple presentation, Call My Keys, might explain the rest. How this idea could be realized is not the important thing in this assignment. But if you’re eager to get one of these gadgets – it actually already exists if you’re willing to spend $160. So much for my creativity and innovation. Still, I feel my idea is a bit different then the Loc8tor I linked to… My device has its place on the wall by the door, but the Loc8tor could just as easily get misplaced as any of the items it’s programmed to locate. I can imagine the frustration people would have when they would need to locate the Loc8tor without having another Loc8tor to locate it!

Parts we used: power jack, voltage regulator, LEDs, potentiometer, 330 Ohm resistors (or similar). In addition we used some already familiar tools like: breadboard, hook up wire, switch, power supply, solder, soldering iron, helping hands, needle-nose pliers, wire stripper, multimeter

MEASURING VOLTAGE

Instructions:
1. Wire up a breadboard with a 5-volt voltage regulator (7805) as shown. The regulator has three legs, typically, input, ground and output, when viewed from the front (where the writing is). Sometimes these legs are in a different order, so find and check the data sheet if you’re not sure! Input is where a high voltage is applied to the regulator. Output is where you will get the regulated 5 volts. Ground is the common ground for your entire circuit, including input, output and all the other components. Bring ground out to both blue ground rails that run along the sides of your breadboard. Bring 5 volt output power to both of the red power rails.

2. Solder a red wire (about 10 cm) to the short center pin of your power jack, and solder a similar black wire to the longer, outer pin. Test the connections with your multimeter to ensure they are good. Don’t allow the two connections to touch each other since that will create a short circuit when you power it up!

3. Attach the red wire from the power jack, using the breadboard to connect it to the input pin of the voltage regulator. Attach the black ground wire to the ground pin of the voltage regulator in the same way.

4. You are now ready to use your multimeter to check the voltages. Plug your power supply into the power jack. Switch your multimeter to the range for reading 0-20 volts, DC. Measure the voltage by touching the red probe to any bare wire on the power rail, and the black probe to any bare wire on the ground rail. You should read just about 5 volts. (4.97 or 5.03 is just fine).

Our setup:

My experience: Used about 2 hours to find a functioning power supply, and figure out how the power jack would work. Considering that our power jack had 3 pins, it was hard to find the right ones to solder wires to. We ended up using another power jack we found in the magical physical computing drawer at the studio that had only two pins. Then we were all set! We heard the BEEEP from the multimeter, and we could measure the voltage in the circuit. 5.01 volts. Success.

BASIC CIRCUIT

Instructions:
1. Disconnect your power supply and you’re ready to make your first basic electronic circuit.

2. Connect a momentary, normally open switch from power to the positive lead of an LED as shown.

3. Connect the negative lead of the LED to one lead of a 33o Ohm resistor (or similar) and connect the other lead of that resistor to ground.

4. Reconnect your power supply, then press the switch. Your LED should light up. The resistor reduces the amount of power flowing to the LED. If you didn’t use the resistor, your LED would light up but probably burn out very quickly.

5. Measure the voltage across the switch when it is closed, then across the LED and the resistor. What do you find?

Our setup:

My experience: Some questions came up:
- Why do we need the resistor?
- Which way does current flow through the circuits?
We didn’t exactly find the answers. BUT the LED was lighting up when button was pushed and the circuit was closed. That’s a good thing.

• Measures when pressing button:
• Voltage across switch: 0V
• Voltage across LED and resistor: 3.44V
• Measures when not pressing button:
• Voltage across switch: 3.44V
• Voltage across LED and resistor: 0V

Did not know why this was happening. Why would there be no voltage when button was pressed down and the circuit was whole??? But we moved on to the next task after scratching our head for a while :/

SERIES

Instructions:
1. Disconnect the power supply again, remove the switch and resistor, then connect two LEDs in series from power to ground.

2. Reconnect the power supply, and use your multimeter to test the voltage at different points in the circuit. What you you find?

3. Why don’t you need resistors in this circuit?

Our setup:

My experience:
When measuring the voltage of the LED lights in series, each LED light was 2.3V, and both of them was 4.6V. You won’t need resistors in this circuit because the LED lights eh… share the voltage (?).

PARALLEL

1. With the power supply disconnected, hook up three LEDs in parallel. (You may need to use a 330 Ohm resistor as your connection to ground to prevent the LEDs from overheating.) Measure the voltage across each LED and confirm that it is does not vary between each one.

2. Voltage is measured in parallel, so you do not need to interrupt the circuit in order to get a reading. To measure amperage (or current), you’ll need to put the multimeter in series with the circuit.

3. Switch the multimeter into DC amperage mode. You’ll be measuring not greater than 1 amp, so choose the correct range.

4. Interrupt the circuit so that current flows through the multimeter as part of the circuit. What is the current flow, in milliamps?

Our setup:

My experience: Setting up 3 LEDs in parallel was easy – and the voltage was the same on each of the LEDs (1.8V). The resistor was 1.6V, and the LEDs and the resistor combined added up to 3.4V. We then tried to measure the amperage of the circuit – but considering that the amperage measured was 0, we might not have done it the right way…

VARYING VOLTAGE

1. Solder three wires to the pins of your potentiometer. It’s helpful to have the two outer ones be red and black (it doesn’t matter which is which) with the middle one being another color like blue. Typically, the two outer pins are connected to power and ground, while the middle one produces a voltage that varies as the potentiometer is adjusted.

2. Create a circuit that varies the voltage flowing to an LED. First connect the potentiometer’s outer red and black wires to power and ground respectively. Then connect the middle wire from the potentiometer to a 330 Ohm resistor, and that 330 Ohm resistor to the positive leg of an LED. Connect the negative leg of the LED to ground.

3. Turn the knob on the potentiometer and measure the voltage coming off the middle wire. What readings do you get and how do they change? How does the LED’s output change?

Our setup:

My experience: When it came to the soldering, we simply skipped it because we were on the 4th hour of the lab – and coiling the wires around the hooks on the potentiometer worked just fine. We were ecstatic over the potentiometer’s ability to dim the light. We played around with it, and measured the voltage of the middle wire. The voltage was different according to how much we dimmed the light.

I’m playing with the Arduino board now. It’s fancy, it’s Italian, and it has a nice little map of Italy on the back with regions and everything. Forgot to photograph the back, but the front is where the action is anyway:

This is a board that you can connect to your computer and then program it to do fun stuff. Like make LED lights blink in interesting patterns. You probably wonder how one would make a LED light be on for 1 second, and then off for one second in an eternal loop. This is how:

// Example 01 : Blinking LED

#define LED 13 // LED connected to digital pin 13

void setup()
{
pinMode(LED, OUTPUT); // sets the digital pin as output
}

void loop()
{
digitalWrite(LED, HIGH); // turns the LED on
delay(1000); // waits for a second
digitalWrite(LED, LOW); // turns the LED off
delay(1000); // waits for a second
}

In addition to actually hook up the Arduino board to the computer running the program, of course. And put a LED light in spot 13. However, by adding a breadboard, some wires, a resistor and a momentary switch to the equation, I can make the LED light turn on whenever I want – as long as I press down the switch button. This is how I set it all up:

Stupid me taking the photo when the LED light was off. But I can assure you, it was definitely on too.

And I also needed some more lines of code to make this work – like defining in the code that there’s now also a nice black button involved:

// Example 02: Turn on LED while the button is pressed

#define LED 13 // the pin for the LED
#define BUTTON 7 // the input pin where the pushbutton is connected

int val = 0; // val will be used to store the state of the input pin

void setup() {
pinMode(LED, OUTPUT); // tell Arduino LED is an output
pinMode(BUTTON, INPUT); // and BUTTON is an input
}

void loop(){
val = digitalRead(BUTTON); // read input value and store it

// check whether the input is HIGH (button pressed)
if (val == HIGH) {
digitalWrite(LED, HIGH); // turn LED ON
} else {
digitalWrite(LED, LOW);
}
}

But wouldn’t it be just perfect if I didn’t have to keep pressing the button down all the time when I want light? Oh yes:

// Example 03: Turn on LED when the button is pressed

#define LED 13 // the pin for the LED
#define BUTTON 7 // the input pin where the pushbutton is connected
int val = 0; // val will be used to store the state of the input pin
int old_val = 0; // this variabke stores the previous value of “val”
int state = 0; // 0 = LED off while 1 = LED on

void setup() {
pinMode(LED, OUTPUT); // tell Arduino LED is an output
pinMode(BUTTON, INPUT); // and BUTTON is an input
}

void loop(){
val = digitalRead(BUTTON); // read input value and store it

// check if the input is HIGH (button pressed) and change the state
if ((val == HIGH) && (old_val == LOW)) {
state = 1 – state;
delay(10);
}

old_val = val; //val is now old, let’s store it

if (state == 1) {
digitalWrite(LED, HIGH); // turn LED ON
}

else {
digitalWrite(LED, LOW);
}
}

This way the switch works as I want it to – lighting up when I press one time, and then it’s turned off the next time I press the switch. By substituting the switch with other objects, I can make my very own switch. I made my switch by connecting one wire to the needle-nose pliers, and another to my key chain. When I let the pliers touch a key in my key chain, there was light. Arduino rules.

In the physical computing class, we will need to master the art of soldering so that we one day can make a fancy ROBOT. So today I will show you my very first soldering experience. I will solder for no good reason. Or for practice. I’m supposed to solder about 100 times until I actual master the art, according to my teacher, Rob Faludi. Fear not – I will not bore you with reports about each time I solder in this blog. I might bore you with other physical computing stuff in the near future, though. Documentation is everything. And documenting the very first time using an soldering iron is essential. Here it goes:

Parts we used: Switch, hook-up wire, solder, soldering iron, helping hands, needle-nose pliers, wire stripper, multimeter

Step 1: Cut hook-up wire

Step 2: Strip small amount of insulation off the ends of the wire with the wire stripper. Try not to cut the wire too, though.

Step 3: Make a hook in the end of the wire to pass through the hole in the switch tab. And clip the wire and switch to the helping hands.

Step 4: Soldering. Warm up the soldering iron to about 600º F. Wet the cleaning sponge lightly. Tin the tip of the soldering iron by touching some solder to the tip of the hot iron. The solder will melt and you’ll see a bit of smoke as the flux inside the solder burns off, cleaning the tip. Wipe the iron quickly on the damp sponge. The tip should be nice and shiny.

Step 5: Hold the side of the tip against both components that need to be soldered together. You want to heat them up so that when the solder is applied, it melts, flows and makes a chemical bond with both components. In a few seconds the components should be hot enough for you to touch the solder to the metal of the components and have it melt and flow nicely. Keep your iron against the components the whole time, taking the solder away first, then removing the iron last.

Step 6: Let the wire, switch and solder cool before taking them off the helping hands. Inspect the join. Is there not enough solder to hold things in place? Is there a huge unsightly blob of solder that prevents you from seeing that it flowed properly? Try to avoid either of these situations. Wiggle the join to see if it’s solid.

Step 7: The only way to learn this is by doing it yourself. Let your lab partner try too!

Step 8: Test the joins by using a multimeter and it’s continuity function. If you hear a beep, then the components are electrically connected.

Conclusion: No doubt about it, Christopher and I have created a fantastic robot with the ability to BEEEEP. Lab = success.