Automatic charger circuit for 9V Nicd Battery

Automatic Ni-Cd battery charger circuit

Although this circuit looks quite impressive, and perhaps a little “difficult, it is not difficult to understand. The circuit must be connected to a DC voltage between 16.5 and 17.5 volts max, otherwise the CMOS IC will be defective. Because I do not want to design a separate power supply for this circuit I connected my full Power Supply adjustable bench top.
   
   
   
First connect one “is cost-”-9-volt nickel-cadmium batteries for proper connections. Then connect it to power. At the 1nF capacitor starts the two RS flip-flop formed by IC1a, IC1b, IC1c, IC1d, and pulls pins 3 and 10 ‘high’ and pins 4 and 11 ‘low’. The clock pulses generated by the freewheeling MULTIVIBRATOR IC4. IC4 frequency determined by 10UF capacitors, resistors CAP 220K and 100K.

The clock runs continuesly, but behind the counter, IC5 not count yet because pin 11 (master reset) is kept high. When the button “START” button is pressed, output pin 4 from IC1a goes up and prejudices tr4 rendered visible by the red LED (D9), who is still on. The NiCad is now discharged via this transistor and the resistance of 100 ohms.
The CAP 10K (right graph) is adjusted so that when the battery voltage drops below 7 volts, the production of IC3 goes low and the output pin 11 of IC1a HIGH. HTE while output pin 10 of IC1d goes low and the red LED turns off.