Battery Indicator Common Cathode Bi-Color LED

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STD Battery Indicator Common Cathode Bi-Color LED

License: Public Domain

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Update time： 2021-06-10 02:10:35

Creation time： 2018-01-02 18:16:31

Description

This is a battery capacity indicator for 3.7V lithium ion batteries, using a bi-color LED (red-green) common cathode. When the battery is from 100% to 50%, the LED stays green. When the capacity is from 50% to 20%, both LEDs turn on so it shows as yellow. When battery drops below 20% the green LED turns off leaving the red LED turned on. It uses a schmitt trigger for both LEDs to prevent bouncing on the threshold. I accomplish this with a dual op-amp. I design this to work with 5V, not only to power everything, but also to have a reference voltage to measure the battery voltage.

Design Drawing

schematic diagram

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Common Cathode
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PCB

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Common Cathode
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BOM

BOM download Purchase Parts

ID	Name	Designator	Footprint	Quantity
1	6k2	R1	AXIAL-0.3	1
2	2k2	R2	AXIAL-0.3	1
3	NE5532P	U1	DIP8	1
4	+5V	+5V	1X01-CLEANBIG	1
5	GND	GND	1X01-CLEANBIG	1
6	+BAT	+BAT	1X01-CLEANBIG	1
7	51k	R3	AXIAL-0.3	1
8	2k	R4,R10	AXIAL-0.3	2
9	6k8	R5	AXIAL-0.3	1
10	2k7	R6	AXIAL-0.3	1
11	S8050	Q1	TO-92(TO-92-3)	1
12	100k	R7	AXIAL-0.3	1
13	100	R8	AXIAL-0.3	1
14	5k1	R9	AXIAL-0.3	1
15	BI_LED	D1	LED2X3.0MM	1