This past week in Physical Computing, Graham Widmann and I worked on completing our auxiliary power supply, and setting up simple circuits. These exercises were introductions into the very basics of electronics. Such as, using a breadboard, how to look at a circuit diagram, how to measure voltages, currents, and resistance, and as well as soldering.
The first thing we worked on was assembling the auxiliary power supply. Once we had all of our materials we started stripping the wire and warming up the soldering iron. I haven’t done very much soldering outside of HackBerry so it was great to relearn it, and have Graham help me along the way. The directions were straight forward, and constructing the power supply wasn’t difficult. Laughably, stripping the wire took the longest. I learned that when you solder you should heat up both the solder, and what the solder is going to be making a connection with. I also learned from the videos in the lab prep, that you can wrap wires together using a drill, which I thought was very clever and time efficient. Oh, and make sure you don’t touch the hot tip of the soldering iron. Our’s wasn’t slotted into the helping hands and as I was reaching for something else and I burned my finger on the tip. Ouch!
Here are some pictures from our process.
First Picture: Graham and I stripping the wire, and getting ready to solder the wires onto the power plugs.
Second Picture: The male end of our power plug assembled. A 9-Volt battery slots into the black bracket.
Third Picture: The pins that were soldered onto the female side of the battery cord. These were very delicate, which required controlled and precise hand movements as to make sure the two pins didn’t get soldered together.
Fourth Picture: Both ends are now attached. Graham and I used the multi-meter to test for continuity, and heard a reassuring beep confirming we had made good connections with our soldering.
The second part of the lab, was getting familiar with constructing circuits, by following circuit diagrams and schematics. We made simple circuits involving an Arduino, a breadboard, jumper wires, resistors, L.E.D.s, a button, and a multi-meter. Graham and I used my new Arduino in this lab, which served as our power supply. Since the Arduino already has a voltage regulator present we did not use an external voltage regulator on our breadboard.
Below: The first completed circuit. From the Arduino, a power (5V) and ground, go to the positive and negative strips on the board (respectively). From there a jumper wire goes to the On/Off button. The button allows the L.E.D. and resistor to be included in the circuit when pushed. The resistor is on the same path as the button and the L.E.D. because the L.E.D. cannot receive more than a few volts before it burns out. A jumper wire connects the L.E.D. back to ground.
Below: A second L.E.D. is added into the circuit. There is still only one resistor and a white jumper wire connects the two bright L.E.D.s in series with each other. We spaced the lights out for easier modifications to be made. We remembered to unplug the Arduino from the computer any time we modified the circuit.
Below: At first our third circuit wasn’t working, or was it? All we did was add a third L.E.D. and plug the Arduino in but that didn’t result in any of them lighting up. We checked our connections and tested for continuity but still no light. We consulted Zane Cochran since we were in the HackBerry Lab. After telling us he knew exactly what was wrong and then proceeding not to tell us, we went online.
Below: When all the L.E.D.’s are in series like above, each L.E.D. isn’t receiving the same amount of voltage, and all the current is being hogged by one L.E.D. restricting flow to the others. Once the L.E.D.’s were rewired in parallel, each L.E.D. got their own resistor, and the total current of the circuit was divided equally among the L.E.D. s on the breadboard, and the voltage across each L.E.D. is the same.