Introduction:
The following projects were created for the first lab assignment for the 2018 Object class at the Atlas institute of university of Colorado.
Prompt:
Build two types of circuits using LEDs, the first with LEDs in series, the second with LEDs in parallel. Calculate the appropriate resistor values for each circuit. Then design a custom switch out of conductive materials. Finally create a creative housing unit for the breadboard and circuit.
Part 1: Series and Parallel Circuits
Materials:
Calculations:
LED Specifications:
Red 1.8 - 2.2 V20, mA
Yellow 2.0 - 2.4V, 20mA
Blue/Green 5V, 30mA
For the series circuit I calculated this would work using the Ohm formula V=I x R where V was 9 volts - .7 volts for the load of the LEDs and I = 20mA.
Dividing 8.3 V by .02 makes 415. I ended up using a 430 ohm resistor for both circuits which worked but maybe wasn't optimized for LED brightness.
Series Circuit:
Here is the first mini breadboard circuit with LEDs wired in series. I used a momentary switch to turn the LEDs on and off. Bellow is the schematic for the circuit.
Parallel Circuit:
Here is the second simple circuit i made for this Lab. I used a button switch to power two LEDs in Parallel.
Part 2: DIY Origami Switch
For my switch I made a paper cicada with green LEDs for eyes, which light up when its wings are held against its underbelly.
For this simple paper circuit, the two LEDs are in parallel with their switch being the connection to ground. Here's a schematic:
Materials:
Origami Paper
Two Green LEDs
110 ohm resistor
Electrical tape
Solder
Flux Pen for rework
Procedure:
First a paper cicada, I just followed this diagram:
Poke two holes for each eye, all the way through the head of the paper creature. Bend the LED connectors so the were 90 degrees from the head of the LED. Insert two LEDs through these holes with positive anodes facing inwards toward the center line of the cicadas belly.
Place a cross of copper tape on the underside of the cicada, just in the center of where the two wings meet. Place an other strip of copper tape about 5mm under the top of the head of the cicada. Make sure it reaches to about the inner holes you just punctured. Place two more strips of copper tape reaching from the tips of the wings to the inner crease of the wing, reaching to the outer cathodes of the LEDs.
Use a 110 ohmn resistor to connect he cross of tape to the strip under the head of the cicada. Insert your LEDs to meet the contacts you just placed. I painted all my connections with a Flux pen then added solder at every intersection to be sure the electrical connection was being made. I found this was the only way to make the circuit reliable.
Finally tape your battery in place over the cross of copper tape and pinch the wings to the belly to light up the LEDs. Voila!
Part 3: Toy Camera Circuit Housing
For my creative enclosure, I decided to use a vintage toy camera. This camera uses obsolete 127mm film, so I felt it appropriate to sacrifice the shooting ability of the film to create this project. The circuit is a single LED attached in the flash of the camera. Here's the schematic:
Materials:
9 Volt Battery Connector with bare leads
Procedure:
Begin by removing the film holder from the camera. Detach any screws holding the film cartridge in place. I forgot to document the camera before taking it apart, but here's a walk through video of the history and construction of the Brownie Starflash. Walk through
After removing the inside film holder from the bottom plate, remove the flash cover from the back using a flat head screw driver.
Pop out the circular red window on the back that leads into the film chamber. Bend open the flash bulb holder and hot glue the RGB LED from the front so the leads poke out through to the flash bulb bracket.
Wrap the negative side of the LED around the gold flash connector and the positive around the silver connector. Clip a alligator clip on each and string the leads through the back circular window into the film chamber. Be sure to remember which wire is power/ground. Gently reattach the flash cover, being sure that the wires are not pinched too tightly when tightening the screw.
Attach the LED power wire to your breadboard. Also attach your power source, a 430 ohm resistor, and a momentary switch connecting power to your LED so the circuit can be turned on and off. Attach the battery ground and the LED ground to the breadboard and test to make sure the circuit works. I used some Velcro to attach the battery and breadboard into the film chamber. I have yet to figure out how to keep the base plate attached to the Camera, so please comment your suggestions bellow.