Fundamentals of Physical Computing: Electronics Lab
A. Measuring Voltage
1. Set up breadboard
- set up breadboard with 5-volt voltage regulator #7805.
- bring ground to blue rails
- bring red from output to power rails
2. Set up power jack (we didn’t use this exact jack in the experiment, a better jack was provided later)
3. Using the breadboard, we attached the red wire from the power jack to the input pin of the voltage regulator. The black ground wire goes to the ground pin of the voltage regulator in the same way.
Checking the voltage:
5.03 volts is equal to 5 volt voltage regulator. Success!
B. Basic Circuit
- Connect a momentary, normally open switch from power to the positive lead of an LED as shown.
- Connect the negative lead of the LED to one lead of a 330 Ohm resistor (or similar) and connect the other lead of that resistor to ground.
- Reconnect power supply, then press the switch. The LED lights up! If the resistor wasn’t there, it would burn out quickly due to the 5 volts flowing through the switch.
Measure the voltage across the switch when it is closed, then across the LED and the resistor. What do you find?
Results:
Across the switch when closed: 0
Across the LED: 2.06
Across the Resistor: 1.80
C. Series
After deconnecting power, and removing the switch and resistor, we connected two LEDs in series from power to ground.
Testing the voltage at different points in the circuit:
Across 1st LED: 2.76
Across 2nd LED: 2.75
Why don’t you need resistors in this circuit?
Because both LEDs offer resistance on the serial path to ground.
D. Parallel
After deconnecting power, we hooked up 3 LEDs in parallel using a 330 Ohm resistor as your connection to ground to prevent the LEDs from overheating. 
Measure the voltage across each LED and confirm that is does not vary between each one:
Each LED measured 1.87 volts.
“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.”
This is part of the lab I didn’t understand. I spoke with Clint and will test the amperage during the next lab.
E. Varying Voltage
- We soldered three wires to the pins of your potentiometer. The two outer pins are connected to power and ground (red and black), while the middle one produces a voltage that varies as the potentiometer is adjusted, so for this we used green.
- 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.
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?
Bright light: less resistance:
Dim light, wiper provides greater resistance:
