Sentinel

I took what was left of Fleet Beacon and added it to a Miller Solar Engine to create this bot. It is essentially two separate circuits on one frame. The first is a classic Miller Solar engine that charges up in the sun and manages to spin the entire robot for a few rotations. I used two 45x25mm solar panels in series for the spinner circuit, which equates to 10v at 30mA. Normally this would be total overkill for the circuit, as the voltage trigger fires at around 4.9v, but I wanted the robot to spin even in less than ideal conditions.

The second circuit is the leftover parts of Fleet Beacon, repaired and attached to the underside of the side solar panels. It is a dark activated pummer that blinks red LEDs for a few hours when the light is low enough.

I used some 1/8" channeled square brass tubing that I picked up from Ace Hardware for the frame of this robot, and I couldn't be happier with how it turned out. I love the look, and the strength is great too. For making angled turns, I clipped out a section of the tubing, bent it to the appropriate angle, then re soldered the edges together for extra strength. It also allowed me to tuck the winged solar panel wires into it to hide them quite effectively.

Overall I am very happy with this bot. It spins during the day, and blinks at night. Leaving for work in the morning he happily spins away, and coming home in the evening he will blink away until bed time.

Fleet Beacon

Fleet Beacon was my first attempt to utilize the 74**240 Bicore chip after my last failure with Syko. He is a pummer that builds charge during the day, and when the light level gets dark enough, switches on an LED blinking circuit. I used a 1.5F Powerstor supercap and a 74HCT240 chip to do the thinking.

With a 1.5F cap, this bot blinks away for about an hour after sunset before draining it's power. The efficiency on this bot could be improved by implementing Wilf Rigter's PowerSaver Flasher circuit, using a storage capacitor that has a higher voltage rating. Currently this one is rated for 2.7V. From what I know about the HCT flavor of bicore chips, they seem to work better when normalized to 5V supply voltage. I could be losing power there. I also did not have any schottky diodes on hand, so I had to use a standard silicon 1N914 version. Other builders seem to get much more efficiency out of their nocturnal pummers. I must have a power leak somewhere!

I do not like how I designed the LED antenna. It doesn't match the style of the base of the robot. I may re-design it later when I get some inspiration.

I used this Makezine PDF as a guide, but altered it a bit by removing the 'pumming' feature and opted for a simple alternating blinking set of LEDs

UPDATE:
In case you were wondering what a blown out capacitor looks like, here it is.

This is what happens when you try to store more charge at a higher voltage than the capacitor is rated for. The Solar Cell on Fleet Beacon can put out 4.7V, while this capacitor is only rated for 2.7V! Since the capacitor remains charged while it is sunny out, this voltage is held on the cap all day. After less than a year the cap called it quits and blew out. I have replaced it with two 10F 2.7V capacitors in series equaling 5F rated at 5.4V, which will do just fine in this circuit. Fleet Beacon will be repurposed soon in another project!