Category Archives: Indicator Circuits

Simple Battery Monitor Circuit Diagram Using NPN Transistor BC547 | Car Battery Monitor Circuit

Parts Used:Transistor : BC547 (Q1)Resistor (All are 1/4Watts)R1 – 10KR2 – 1KR3 – 1K Diode:D1 – 6V, 500mW ZenerD2 – LED (any color)Circuit Description:This circuit indicates a warning whenever the battery voltage falls below the level set by 10K pot. It can indicate that the battery is defective or needs charging if cranking drops battery voltage below preset “safe” […]

Low Battery Level Monitor Using Op-Amp 741

Parts Used: Resistors: (All are 1/4 Watts) R1 – 1M R2 – 470K R3 – 8.2K R4 – 680E Diodes: D1 – 5.1 Zener (500mW) D2 – IN4148 L1 – LED (any color) IC: U1 – Op-Amp 741 Battery: BT1 – 12V Switch – On/Off Circuit Description: A 741 op-amp is employed as a voltage […]

12V Battery Charge/Discharge Indicator Using The Dual Op-Amp LM358 | 12v battery level indicator

Parts Used: Resistors: (1/4 Watts) R1 – 10K R2 – 10K R3 – 10K (preset) R4 – 10K (preset) R5 – 1.5K R6 – 1.5K R7 – 1K R8 – 1.5K R9 – 1.5K IC: U1 Dual Op-AmpĀ LM358 LEDs: Red Green Yellow Fuse:100mA 12V Battery General purpose PCB Circuit Description:This circuit monitors the 12V battery […]


Parts Used: IC: U1 – 555 Timer Resistors (All 1/4 Watts): R1 – 22K R2 – 8.2K R3 – 470E Capacitor: C1 – 0.001(ceramic disc) Diode: D1 – 6v, 500mW (Zener) LED – Any color 12V Battery Circuit Description: The average current drain is 1mA or less due to the low duty cycle of the […]

Water Level Indicator Circuit Project Using IC 555 With Motor Dry Run Protection Alarm

Components Required:Resistors (All 1/4W)R1 – R6 – 1MR7 – R12 – 220KR13 – R17 – 1KR18 – 3.3KR19 – 1MR20 – 100K (Preset)R21 – 1KR22 – 1.5K Capacitors:104(0.1uF) – Ceramic Disc – 1 no.100uF,25V – 1 no.470uF,40V – 1 no. IC:U1- CD4049 (with Base)U2-555(with Base) Diodes:D1 – LEDD2 & D3- IN4148DB1- W04 (Bridge Rectifier) Transistor:S8550 PNP Relimate Connector:Sensor – […]