P Comp Week 1 Labs

Setting Up A Breadboard

Setting up the breadboard – using a 7805 regulator, and connecting the ground and voltage buses throughout the board and to the proper pins of the regulator.

Soldered a DC power jack to two header pins and covered the connections in hot glue to prevent any shorts. Connected the jack to the breadboard correlating to the correct ground and voltage in pins of the regulator.

Will it light?

Test 1

Yes. The wiring is correct with the resistor in series between the voltage and LED.

Test 2

No. The LED is connected to the ground bus but has no voltage going to the anode. The resistor has one leg in the voltage bus and nothing on the other leg. Although the resistor and LED are in the same row, the center divider breaks up the connection so we are left with an incomplete circuit.

Test 3

Yes. It is essentially the same schematic as the first circuit, aside from the physical placements of the components on the breadboard. The components are in the same locations on the breadboard as test 2, however this circuit works due to the hookup wire bridging the two sides and connecting the resistor to the LED.

Test 4

No. The resistor and the LED are all connected in the same row, with the wire jumping to the ground bus. This is causing a short circuit.

Test 5

Yes. The LED is bridging the gap to have a connection to both the ground bus and the resistor.


Measuring the voltage drop across the LED.

Switched LED Circuit with a Pushbutton

Measuring the voltage across the pushbutton

On the left, the multimeter reads around 5V because the voltage is stopping here, and not going through the circuit to power the LED.

However, on the right, the multimeter reads 0V, and this is because when the button is pushed, the voltage is traveling through to power the LED.

Components in Series

Adding up voltage, and adding a third LED

After adding the third LED, none of the LEDs will light up because each one draws about 2V, and the 5V powering the circuit is insufficient.

Components in parallel

Generating a Variable Voltage with a Potentiometer

Using a Breadboard with a Microcontroller

With the Arduino Nano, I patched a wire from the pin 2 of the microcontroller to the voltage bus which provides 3.3V to the breadboard, along with a wire connecting pin 14 of the microcontroller to the ground bus.

Powering a Breadboard with a Microcontroller via DC Power Supply

In order to power the breadboard via the microcontroller without a USB, I connected a DC power jack to pins 14 and 15 of the Arduino (ground and voltage in) and add a 9V battery in line.

In this next test, I added a 5V regulator connected to pin 15 (voltage in) of the microcontroller, in order to provide 5V to components who may require it, while the Arduino is still powering 3.3V throughout the breadboard’s voltage bus. I did a test adding a switch and a lightbulb off of the 5V regulator.

Switches and Pushbuttons

Project 1: Three Switches in Parallel

With the three switches in parallel, any one of the buttons will light up the LED

Project 2: Three Switches in Series

With three switches in series, all three must be pressed in order for the LED to light up.

Project 3: Switching a Motor

A motor attached to a switch.

At first I had some issues with this portion of the lab because I just could not get the motor to run. For a moment, the first motor I was using moved but then immediately stopped and I was unable to get it working again. After fussing with it some more, I decided to borrow another motor from the shop, and immediately I was able to get it to work. So I just came to the conclusion it may have been a bad motor.

A motor and LED both operated by a dual pole switch.

Creative Switch

The Record Stand Light

For my creative switch, I took inspiration from this piece of wood I have that is shaped to hold and display a record sleeve while the record spins on my turntable. I want to recreate this stand so that when a record is placed in its slot, a light will turn on.

As pictured above, I started off by playing around with other materials to make a switch sensitive to touch. Here I stuck two wires to a folded piece of paper with some copper tape to make a switch that would activate the light when I sandwiched the two sides together. In this circuit, I had three white LEDs in parallel to all be turned on simultaneously by the switch.

Below I started shaping out a prototype enclosure with cardboard and tape. I started to play around with cutouts for the LEDs and the DC power supply port.

Next, I recreated the switch from above into a smaller shape with some cardboard so that I can place it in the slot where the record sleeve would sit.

Once I had the connection, I arranged the switch into the prototype and tested it by actually placing a record. Here it is a bit finicky as the record needs to be placed in a specific position in order for the switch to stay closed.

Once I had my prototype enclosure, I cut out pieces for my final enclosure using what I believe is compressed cardboard …? I’m not sure, I took it from the free shelf on the floor 🙂

I just used hot glue to bind a few of the sides.

I then played around with some different circuits to ultimately incorporate three separate switches.

In the figure on the left, I used the press switch along with a potentiometer. In this circuit the press switch would light up the green LED, and when the potentiometer was turned on, it would also light up the white LED.

In the circuit on the right, a switch is in line with the potentiometer so that the switch must be flipped to the on position, and the potentiometer turned up in order for the LED to light up.

Next, and my final circuit that I decided to use for my creative switch, is a series that consists of a toggle switch, press switch, and a potentiometer. In order for the light to turn on everything must be pressed/switched/turned.

The last bits I needed to do were to finish the enclosure, and all the wiring. I decided to have three LEDs in parallel, and in order for the LED prongs to reach the breadboard, I soldered hookup wires to the cathode and anode, and used heat-shrink over the connections to prevent any shorts.

Before putting all the actual panels together and completing the enclosure, I partially used bits of my cardboard prototype to make wiring adjustments before finalizing.

One issue I ran into was activating the press switch. It’s a bit touchy with the record placement and sometimes the record would have to be in a specific position in order for the press switch to make the connection. Trying to fix this issue, I lengthened the press switch, and added a layer to one side, hoping to increase the surface area that could make the connection between the two wires.

I continued to work on finishing the wiring and adding the rest of the panels to the enclosure.

Below is the final look of the record stand light. A last minute add — something I almost forgot to do — was to make sure I had a way to get the breadboard back out without ripping apart the panels, and so I made the front panel removable.

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