NiMH trickle charger with status indication:
In spite of the considerable media attention to the concept of recyclable power sources, usage of rechargeable Nickel-Metal Hydride (NiMH) cells has been limited. The combined charger and cell cost have been a mitigating factor in favour of primary cells. The high internal impedances of primary cells are not suitable for the surge currents needed for digital cameras, DC motors and walkie-talkies. NiMH cells exhibit low internal impedances and, as such, are particularly viable in these applications.
The above schematic (“FIGURE 3”) is NOT the charger circuit. The app note describes figure 3 as, “the basic concept of a trickle charger”. The actual circuit uses a PIC10F222 microcontroller.