This article describes the automatic charger can be nickel-cadmium or nickel metal hydride batteries , battery charging voltage as long as the setting , the lower limit , the charger can charge the battery automatically . Circuit Automatic battery charger circuit as shown , mainly by the RS flip-flop charger , charging voltage , the lower limit circuit and power circuit RS flip-flop by a 555 A circuit composed of two internal comparator reference voltage from 5 feet to provide an external regulator VS , so reset the circuit level of regulation for the VS value of the 3V. Set the upper limit of charge voltage circuit by the potentiometer resistor R3 RP2 and composition ; charging voltage to the lower limit set by the potentiometer RP3 circuit and resistor R4 form . T by the step-down transformer power supply circuit , diode VD1 ~ VD4 bridge rectifier and filtering capacitor C1 supply . Rechargeable batteries should be charged under Section G, number and type of battery , adjust the lower limit of RP3 to set the charge voltage , adjust the maximum charging voltage RP2 set . Thus, when the battery voltage is low G , RP3 -based real-time sliding side circuit level is less than 2 feet V5 / 2 ( V5 here refers to the time base circuit 5 foot level , that is, the value of VS 's regulator 3V) , the time base A circuit set, 3 -pin output high after RP1, VD5 charge to G , while VL light directions . When the G power is sufficient , RP3 -based real-time sliding side circuit level greater than 6 feet V5, time-base circuit operation, and 3 -pin output low , the charge to stop , while VL out . Adjustment can be adjusted RP1 battery charge current size of G , should be the basis of the nature of the rechargeable batteries , such as nickel-cadmium rechargeable batteries , 5 general , the charge current is about 50mA generally adjustable in . Diode VD5 role is to prevent the cessation of charging , the battery anti- G to the sink current time-base circuit . This circuit can be used for 2 ~ 8 5 nickel-cadmium or nickel metal hydride batteries. Component Selection VD1 ~ VD5 use IN4001 and other silicon rectifier diodes . VS selected 3V, 1/2W Zener diode , such as UZ-3.0B, IN5226 type and so on . VL use an ordinary red LED . RP chosen 2W wirewound potentiometers ; RP2, RP3 use an ordinary small-scale synthesis of carbon film potentiometer , such as WH5 type , etc. ; R1 ~ R4 are selected 1/8W carbon film resistors . C1 selected CD11-25V -type aluminum electrolytic capacitors . T use 220V/15V, 5VA small, high quality power transformer . 4 5 nickel-cadmium batteries This article describes the automatic charger can be one of the four nickel-cadmium battery 5 , the battery is fully charged , the circuit can automatically stop charging . Circuit Automatic nickel-cadmium battery charger circuit as shown , mainly by the power charger circuit, voltage comparator and indicating circuit and other components. T by the step-down transformer power supply circuit , rectifier diode VD1 ~ VD4 , three-terminal regulator integrated block A1 regulators and capacitors C1, C2 filtered supply , the circuit is powered output DC 9V stable voltage for the charger to use . Voltage comparator A2 by the time base circuit composed of the control side at 5 feet it has a Zener diode connected VS ( voltage 5.6V), it will reset the circuit -level positioning in 5.6V. VL for the charge indicator LEDs . 1 5, nickel-cadmium battery the normal operating voltage 1.2V, charge termination voltage of 1.4V or so . G for the four to be the nickel-cadmium rechargeable batteries, so charging termination voltage is 4 × 1.4V = 5.6V. After charging into the battery bracket , close the power switch S, will start charging . Circuit process: As the voltage across the capacitor C3 can not mutation , when just power , A2 of 2 feet for the low , A2 is triggered set, 3 -pin output high , this high level by potentiometer RP, diode VD5 G to the battery charge can be adjusted to change the RP value of charge current size. At this point A2 of 7 feet was vacant , VL LED indicating circuit in the charge . With the continuous charging , G gradually increases the voltage across , the time when the rise 5.6V , A2 reset , 3 -pin output low , automatic charge termination , and A2 internal discharge tube turns on, the 7 -pin output low , VL off the end of that charge . Component Selection A1 select the LM7809 -type three-terminal regulator blocks, should be installed for aluminum heat sinks. VD1 ~ VD5 use IN4001 type silicon rectifier diode . VS use 5.6V, 1/2W Zener diode , such as UZ-5.6B, IN5232 type and so on . VL use an ordinary red LED . RP chosen 2W wirewound potentiometers , R1 ~ R4 are selected 1/8W carbon film resistors . C1 selected CD11-25V -type aluminum electrolytic capacitor , C2, C3 for the CD11-16V -type aluminum electrolytic capacitors . S use an ordinary small 1 × 1 power switch . T use 220V/12V, 5VA small, high quality power transformer .