IC LM3914 Battery Tester Project

The schematic shows the simple connections where the reference voltage at pin 8 of U1 can be adjusted by adjusting the variable resistor VR1.

• The voltage at pin 8 will set the maximum scale of the LED.
• In testing dry cell battery of 1.5V, set the voltage at pin 8 to 2.0V.
• Each of the LED will thus represent 200mV when lighted up.
• If testing of rechargable battery such as NiCd or NiMH is required, set the reference voltage to a lower value such as 1.5Vas the typical voltage of a rechargable battery is approximately 1.2V.
• When testing the battery, take note of the polarity of the probe to the terminals of the battery.
• T1 is to be placed on the positive terminal and T2 the negative terminal of the battery.

• U1 = LM3914
• L1, L2, L3, L4, L5, L6, L7 = 5 mm Red LED
• L8, L9, L10 = 5 mm Green LED
• S1 = SPST Toogle Switch
• R1 = 1 k ohm 1/4W, 1% Resistor
• R2 = 100 ohm 1/4W, 1% Resistor
• VR1 = 1 K Variable Resistor
• C1 = o,1uF/25V Ceramic Capacitor
• T1, T2 = Probes

S:electronicsuite.com