Abstract: A control circuit for tracking of a heat radiation source which functions to maintain heat collection structure in optimum alignment with the source thereby to enable maximum efficiency of heat collection; the control circuit includes a threshold circuit for sensing ambient light level to provide enablement control to A-C power circuitry which energizes the heat collector orienting drive system, and the threshold circuit also functions to automatically invert the heat collector to a protected position upon detection of insufficient threshold voltage; and, the circuit further comprises a tracking section energized by a radiation sensor to cause intermittent energization of the drive system to further enable intermittent bi-directional tracking movement of the heat collector, such tracking circuitry being enabled by detection of sufficient threshold voltage.