Final Project

For the final project in this lab, I was told to improve my AM radio. In order to improve the radio, I considered several options, like moving it to a PCB or adding volume control. In the end, I decided to improve the radio by improving it's operation by trimming up leads and powering it with an alternate voltage source. The first part of the project was easy, after trimming the leads of my capacitors, resistors, and wires, the radio had a clean and loud output down to four volts as opposed to the normal nine volts we used in lab. My final radio design is included in the picture below.

After improving the operation of my AM radio, I considered my options for alternate power sources. Eventually I settled on fruit power, creating a battery made with lemons to power the radio. Lemons are the most ideal fruit for power applications because they have a high concentration of citric acid, providing plenty of electrolytes for the chemical reaction that produces voltage. In order to construct the battery, I inserted a copper tack in one side of the lemon, and a galvanized nail in the other. The copper and zinc in the nails start a chemical reaction inside the lemon which induces a voltage. I measured the voltage for a single lemon to be somewhere between 0.8 and 0.9 volts, meaning that my radio needed 5 or 6 lemons to produce the 4 to 5 volts it needed to operate. The end result was that I created a battery, with each lemon acting as a single cell. The fully constructed battery is included in the picture below.

Unfortunately, this battery was ineffective as a power source for the radio, as I would learn that the lemons have a massive internal resistance, in excess of 20 Megaohms. This means that while the lemons produce the necessary voltage, they provide little to no current.

This lab has been very helpful to my understanding of radio operation and audio processing. I've also learned a lot about the performance of analog electronics such as amplifiers and capacitors. Before this lab, I did not understand the importance of trimming wires and leads, and the impact that has on producing a more efficient and useful radio. During this project I have learned about the chemistry that makes batteries operate and how important it is to consider the internal resistance of a power source in real-world circuits.