Basically a high-efficiency dimmer, but can also be used as a flasher. In dimmer mode, the LM358 (dual op-amp) is wired to send pulses at a constant frequency. By adjusting the width of these pulses, brightness of the bulb is controlled. In flasher mode, the same potentiometer is used to control the frequency - from about 1 to 20 flashes per second.
By lowering the brightness power consumption drops considerably, thus extending battery life. Flasher mode is even more efficient. This nice little circuit will work with any DC power supply/battery from 4.5 to 15V. A heat sink on the TIP32 power transistor should not be necessary.
Build this flasher in one of those big 6V flashlights to select only as much light as you need it and at the same time lengthen the battery life. It served me well this summer!