A Low Power Indicator can be defined as an indicator that is having a very low electrical supply or current situated in an electrical instrument which indicates the amount of power present in the instrument by their colour indication be it red, yellow or green.
1.1 TYPES OF A LOW POWER INDICATOR
A. LIGHT – EMITTED DIODE (LED): - This is a junction diode made from the semiconductor gallium arsenide phosphide which has large band gap and hence a larger forward drop than silicon. Typical flooded panel – type LED indicators look good at 10MA forward current on a board inside an instrument one can usually get away with 2.5MA, particularly if one use a narrow-angle LED. When forward biased it emits red, yellow or green light depending on its exact composition. No conductor or light emission occurs for reverse bias which if it exceeds 5V, may damage the LED.
B. LIQUID CRYSTAL DISPLAY (LCO): - This is a display that is usually is a driven by an a.c wave form otherwise their liquid guts (contents) are ruined. However, it driver chips have some way to generate a square – wave segment drive, synchronized to the LED backplane wave form. An example is the HC4543, the LED cousin of the HC4511 LED latch/decoded driver. LCD come in rather large panels that can display a line or two or text i.e they have ability to store several message and communicate via serial ports.
C. LOW – BATTERY INDICATOR USES FLEA POWER: - This is a low indicator that consumes as little power as possible for a 9V, 450-MAhr alkaline battery, a 50 – PA low battery indication can by itself run the battery down in a little more than a year battery – powered devices that need to run continuously for a long time require battery indicators that consume minimal power.