• on Test & Measurement
  • Published in issue 3/2013 on page 56
About the article

Battery-Nearly-Empty Indicator

Simple but effective

Battery-Nearly-Empty Indicator
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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Products
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
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