BATTERY TESTER

For my GCSE Electronics practical I decided to manufacture a battery tester. The idea to build this came after struggling to find functioning batteries at school.

After deciding what product I would manufacture, I started by brainstorming ideas (shown in Figure 1). This was based on the following criteria; purpose, cost, size, target market (client), aesthetics, safety, materials, and environmental impact.

Then I proceeded to consider what was currently available on the market to evaluate how other designers/ manufacturers have tackled the design challenge.

Finally, I also sent out a questionnaire to a sample population of 30 students to gather feedback on factors such as the desired features and cost.

Figure 1: Initial brainstorming

Following the initial brainstorming and market research phase I proceeded to make concept designs. I first considered what components I would need as well as the optional components that I could use to improve the functionality of my product. Through this research, I decided to use an LM3914 for indicating the battery charge as a visual signal. I choose this specific microchip as it is a low-cost method of taking the analogue input from the battery (i.e. the battery voltage) and discretizing it into steps and finally converting it into a visual signal. As an optional addition, I also considered using a programmable PIC microcontroller unit in conjunction with a piezo buzzer to generate an audio signal.

Implementing these components I then started to make concept designs as shown below. After evaluating all these designs I choose "Concept 6" for manufacture as it combined the desirable features from all the other concepts whilst remaining intuitive to use and relatively cost-effective.

The next step to consider was the circuit design. After going through a similar iterative process to the product casing itself I decided to proceed with the following circuit design..

Figure 2: Circuit diagram

Figure 3: Circuit operation

Using Circuit Wizard I then designed the circuit for manufacture. Due to the complexity of the connections I decided to separate the circuit into two sections to facilitate the manufacture and later assembly. The resulting circuits and their assembly within the casing are shown below.

Figure 4: Final circuit design

Figure 5: Overview of finalised product design

Having completed the design process I proceeded to manufacture the battery tester. I started by manufacturing the circuit boards. Then I proceeded to solder all components onto the circuit board. After testing the electronics I proceeded to manufacture the casing. I started by making wooden moulds. Then using vacuum forming I created the casing shell. Then using the laser cut components I made the stands. Finally assembly everything I was able to complete the battery tester.

Finally, I tested the product with different batteries of known charge. This allowed me to evaluate the functionality of the battery tester and evaluate its accuracy.