The phototrophic head is the basis for nearly any phototrophic robot. As these are the simplest devices that move to seek light. Heads come in a variety of shapes and sizes and can either lock on to a light source or continually search. 

Build Date: Jan 30, 2003

A head build using a VPM (Vibrating pager motor) The circuit that I used to make this can be found here. Also a video of this in action can be seen here. The video was taken earlier today,  the quarter in the video is for size reference and the shadow of the coin gives an indication of the direction of the sun. This circuit will not lock but will continue to scan back and forth.

Build Date: April 26, 2002

My SAIT Final Project: "Very different than a power supply".
The basic idea behind this is that the large solar panel array is
used to trickle charge a 12V 12AH sealed lead acid battery, the battery then powers a 300W power inverter. That way the solar array is always being aligned towards the brightest source of light (usually being the sun). This will effectively double the power output of the solar array. The two smaller cells to the side are what power the circuitry and motors. Once the light source is centered the motor driver is powered down and a pair of ultra bright LEDs start to flash (one for the X axis and one for the Y axis).

For demonstration purposes it can also be battery powered with the flip of a switch.

Inverter box with battery: 7.623Kg (16.8 lb)

Head without inverter box: 8.862Kg (19.537 lb)

Combined weight: 16.485Kg (36.34 lb)

Head measures 2 feet tall by 21 inches long at 19.5 inches wide

The last pic here is of the bottom side of the PCB, I tried to put all sorts of hidden things like that.

 

Build Date: I can't remember exactly and I didn't scribe it in, damn.

A head built from one of the first generation bio bug motors (notice the yellow motor). These motors are not nearly as good as the more recent ones (white plastic motors) The slip clutches were too weak, the gears were more sloppy and the output shaft was 2mm smaller. One of the first heads to use the solar shok circuit derived from Mark's shok walkers.

Build Date: March, 1999

This is the very first light seeking head that I constructed. Originally it was just battery powered but a few years later I decided to solarize it and change the brains a bit using the BEP boards. To my recollection this is the first application at home that I used the BEP boards for.

Uses two servos for a combined up/down and left/right ability aka. a 2DOF head. The head is powered by a Miller solar engine but also has the switched option of a battery, this works well for demonstrations.

The circuit seeks the brightest source of light and when found powers down the motor driver and flashes a pair of LED's one for X axis one for Y axis, they will independently lock as well.

Still faithfully watches the sun, nearly four years and running.