Article

Battery-Nearly-Empty Indicator

Simple but effective

This circuit gives a signal using an LED when the voltage of a monitored battery drops below an adjustable minimum value. The NEI (Nearly-Empty-Indicator) consists of a voltage reference, a comparator and an LED indicator.

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Materials

120350-PCB

Extra info / Update

Note: Since the original publication of this project/article, some of the components, software elements, webpages and other elements might have been updated or changed.

Component list

COMPONENT LIST
Resistors
R1 = 4.7kOhm
R2 = see text
R3,R4 = see text
R5 = 680kOhm
R6 = 22Ohm
R7 = 15kOhm
R8 = 27kOhm
P1 = 10kOhm trimpot
Capacitors
C1 = 2.2µF 16V
Semiconductors
D1 = LED, green
D2 = LED, red
D3 = LED, high-efficiency, red
T1 = 2N6028
IC1 = LM10
Miscellaneous
Prototyping board e.g. Elektor UPBB (Elex) Type 1

Discussion (0 comments)

Kenneth Cox 3 years ago

The LM10 is obsolete, but still available from some suppliers. A more recent equivalent is the LT1635 (with better specs, but nearly as expensive as the LM10).

DAVID CIAFFA 3 years ago

Old, but not obsolete yet. TI still shows the LM10 as active, and it is readily available from distributors in the US. Agree the LT1635 is a better performing part, but it is around 2X the cost here in the US.