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.
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!
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.
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).
Voltage Regulator 7805
Wiring Power Jack
Voltage Regulator Setup
Measuring Voltage
Basic Circuit
Disconnect your power supply and you’re ready to make your first basic electronic 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 33o Ohm resistor (or similar) and connect the other lead of that resistor to ground.
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.
Measure the voltage from ground at the switch when it is closed, then across the LED and the resistor. What do you find?
If your circuit doesn’t work right away, try to figure out why. You’ll learn more from the things that don’t work at first than the things that do, so be sure to celebrate when they don’t work almost as much as when you figure out your error and fix it.
Basic Circuit
Basic Lit
Series
Disconnect the power supply again, remove the switch and resistor, then connect two LEDs in series from power to ground.
Reconnect the power supply, and use your multimeter to test the voltage at different points in the circuit. What you you find?
Why don’t you need resistors in this circuit?
Series Circuit
Series Lights
Parallel
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 is does not vary between each one.
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.
Switch the multimeter into DC amperage mode. You’ll be measuring not greater than 1 amp, so choose the correct range.
Interrupt the circuit so that current flows through the multimeter as part of the circuit. What is the current flow, in milliamps?
In the process of getting to know electronics, you will probably have occasion to damage some components. Naturally this is not normally our goal, but it is the almost-certain by-product of discovery and learning. As long as you figure out what went wrong, your errors are productive and should not dissuade you from continued experimentation.
Parallel Circuit
Varying Voltage
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.
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?
Lab-Electronics
Parts
Measuring Voltage
Basic Circuit
If your circuit doesn’t work right away, try to figure out why. You’ll learn more from the things that don’t work at first than the things that do, so be sure to celebrate when they don’t work almost as much as when you figure out your error and fix it.
Series
Parallel
In the process of getting to know electronics, you will probably have occasion to damage some components. Naturally this is not normally our goal, but it is the almost-certain by-product of discovery and learning. As long as you figure out what went wrong, your errors are productive and should not dissuade you from continued experimentation.
Varying Voltage