Rechargers or battery testers are used in every durable product, from laptops, cameras to iPhones, and are quite a common phenomenon. Companies are constantly on the lookout for newer and improved versions of these items.
One way to look at the project is to build an improvement in terms of innovation. For example, you could try a faster battery tester or a more cost effective one. Another alternative is to try a smaller sized battery tester. People are constantly running out of space. If companies can decrease the size of their rechargers and battery testers, they will not only reduce cost of goods sold, but they will also be able to package the product in a smaller pack.
Many musicians will salute you if you can come up with a cheaper or a more effective amplifier system. It would be even better if you can make an amplifier system to suit custom requirements of musicians. One of the most widely used type of transistor amplifiers is quite easy to assemble. It is one of the simplest electronics projects as well, as it only takes a single transistor, two resistors and a couple of batteries.
AC DC adapters, also called voltage rectifiers, can be made with four diodes. Take these diodes and connect them in the shape of a diamond. The voltage rectifier can turn alternating current into direct current.
To make a lie detector you need an electrical current meter, some resistors, batteries and a capacitor. Once all these are connected, the detector will be able to pick up the changes in skin conductivity of people when they are lying.