Simple NiCd charger

simple NiCd charger 1701 Dry batteries have one major disad- vantage: they go flat. Rechargeable types, such as NiCd cells, also suffer from this drawback, but they can at least be recharged. Sometimes even a fifteen minute charge is sufficient to give enough life to, say, an electronic flash battery. A NiCd charger is, in essence, nothing but a sophisticated current source. The present design contains four such sources with a common control switch, but each with a separate LED that lights as soon as a battery is connected to it. In position 1, the sources each pro- vide a current of about 90 mA; in pos- itions 2 and 3 values of between 100 and 300 mA as required. Note, how- ever, that with charging currents above about 200 mA the transistors must be fitted on suitable heat sinks. On stability considerations, it is advisable to mount diodes Di to D4 incl. in good thermal contact with the relevant transistors. Terminals +B and -B enable the cir- cuit to operate from a 12 V DC sou...