ABSTRACT

Technology on batteries has advanced over the years as a result of the need to power portable devices that have risen in numbers in the last decade. Just like primary cells, rechargeable batteries work in the same way, only their chemical reactions are reversible. This project aimed at building a system that would indicate the capacity level of a Nickel Metal Hydride battery upon charging and discharging. The Nickel Metal Hydride battery was selected in this project due to its preference among consumers. However, since the principle behind the rechargeable battery technology is similar, the system can be used to test other types of batteries. System implementation involved designing and building a battery charger circuit and a discharge circuit. Software design then followed, after which testing was performed. The project uses a LM3914 driver IC use to drive 10 leds by passing through it sufficient amount of current. Brightness of leds are controlled by reference adjustable pin and reference out pin. The project goal was achieved and results were presented through numeric figures, charts and indicators. The system is expected to help in planning with batteries to avoid halt of devices during operation. The results gathered during testing point to possible reduced battery wastage. A better way to handle batteries to conserve capacity has also been highlighted.

CHAPTER 1

INTRODUCTION

1.1 PROJECT OVERVIEW

Battery level indicator is a circuit that is used to check the battery life. We can easily recognize the battery level with the help of LED’s. It uses a LM3914 driver IC use to drive 10 leds by passing through it sufficient amount of current. Brightness of leds are controlled by reference adjustable pin and reference out pin. A variable resistor is also deployed in the circuit to have variable input voltage at pin 5 of the driver IC. Since the driver IC has two modes of operation which is bar graph mode and dot mode, it enables us to have indication of the battery life either in bar form or in dot form. We can have colouredlods to indicate state of the batteries like first three leds will indicate low battery. Green leds will indicate full battery. Thus by using various colouredleds representation of battery life will be made easy to understand. Cascading the driver ICs we can increase the range of battery input in terms of voltage. In the below given block diagram we have 4 blocks. One is the power supply. other is the driver IC itself. We will have a led block and an input block. A reference input for comparison purpose. Leds will glow according to the input given and the reference Input present.

Power supply is ranging around 12 to 18V. Reference voltage is pre decided which is 1.25mV. Any dc signal lying in the range of the power supply is judged and the level is indicated by the leds. The current through the leds is controlled by the internal adjustment.