This Design Idea describes a 9V battery-voltage monitor whose total parts cost less than 34 cents (Figure 1). You configure transistor Q1 as a 10-mA current sink. LED1, a Kingbright WP7104IT, is on when the battery voltage is good. When the battery voltage nears the threshold voltage, the LED gradually dims.
It goes out once it reaches the threshold voltage. The threshold voltage for this design is 7.2V, which the values of D3, LED1, and R1 determine. If your application requires a different threshold voltage, you can change these three components’ values. You can reduce the PCB (printed-circuit-board) space this circuit requires by using equivalent surface-mount components.
For more detail: Configure a low-cost, 9V battery-voltage monitor
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Ibrar Ayyub
I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.
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