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USB NIMH NICD BATTERY CHARGE SCHEMATIC CIRCUIT DIAGRAM

The circuit is designed to charge two AA NiMH or NiCd batteries using the 5-volt power supply from a computer’s USB port. This circuit incorporates the LM393 Op-amp and provides a charging current of 470mA. Detailed information, including the circuit’s PCB layout, is available.

USB NIMH NICD BATTERY CHARGE SCHEMATIC CIRCUIT DIAGRAM 1

During the charging process, a three-way voltage divider consisting of R1, R2, and R4 is established, resulting in a voltage of 1.26V at the non-inverting input of Z1a (pin 3, Vref). TR1, which is a thermistor, exhibits a resistance of 10k at 25°C (77°F), translating to an approximate 3.7% change for every 1°C (1.8°F) variation in temperature. R3 and TR1, in tandem, create another voltage divider contributing to the value at pin 2, Vtmp. At a temperature of 20°C (68°F), TR1’s resistance is approximately 12k, resulting in a Vtmp of approximately 1.76V.

This charger is a pioneering solution for AA NiMH or NiCD batteries, boasting impressive charging times of around 1.5 hours for 700mAh NiCDs, roughly 3.5 hours for 1500mAh NiMHs, and approximately 5.5 hours for 2500mAh NiMHs. The charger features an automatic charging mechanism.

USB NIMH NICD BATTERY CHARGE SCHEMATIC CIRCUIT DIAGRAM 2

USB NIMH NICD BATTERY CHARGE SCHEMATIC CIRCUIT DIAGRAM 3

USB NIMH NICD BATTERY CHARGE SCHEMATIC CIRCUIT DIAGRAM 3

Size: 3.8 1.5 L x 1.2 cm W x 0.7 ″ H (9.7cm x 3.0cm x 1.5cm).
Cells: Two AA NiMH or NiCd
Charging Current: 470 on
Charge Termination Method: Battery Temperature (33 ° C)
Trickle Current: 10mA
Power Source: Desktop, Laptop, or Hub USB port
Operating Conditions: 15 ° C to 25 ° C (59 ° F to 77 ° F)
Battery Current        Charging Time
700mAh NiCd                1.5saat
1100mAh NiCd              2.5hrs
1600mAh NiMH            3.5saat
2000mAh NiMH          4.5hrs
2500mAh NiMH          5.5saat

The LM393 IC is a dual, differential comparator known for its low power consumption, single-supply operation, and minimal offset voltage. In essence, a typical comparator IC can be thought of as a compact voltmeter that incorporates switches. Its primary function is to measure and compare the voltage levels at two distinct terminals, highlighting the difference in voltage magnitude.

The main features of this IC mainly include the following.

  • Single voltage supply ranges from 2.0 Vdc toward 36 Vdc
  • The split supply range will be from +1.0 Vdc or -1.0 Vdc to +18 Vdc or -18 Vdc
  • The little Supply Voltage of the Current Drain Independent is 0.4 mA
  • The input bias current is low that is 25nA
  • Input offset current is low that is 5nA
  • Both the range of differential input as well as Power Supply Voltage are equivalent
  • The output voltage is well-suited by ECL, MOS, DTL, TTL, & CMOS Logic Levels
  • Electrostatic discharge bolts on the inputs enhance the device’s roughness without troubling its performance
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