Flatbot

Flatbot was inspired by Simon Fraser's Fred Flatbot. I always liked the form factor of this bot, and I didn't want all my photovores to look the same. Flatbot is a miller photopopper with some modifications.

He is powered by a massive 37 x 66mm Solarbotics solar cell that puts out 6.7V at 30mA! When designing Flatbot, I knew that the motors had pretty lousy torque, and putting any kind of wheel on them parallel to the ground would result in wasted energy. Luckily i had two 1381-U's sitting around to put that voltage to work.

The next challenge was keeping the flat aesthetic. I managed to find 4 small 1000uF capacitors that I wired in parallel to give it 4000uF. I also boosted his .22uF timing caps to 1uF. This would hopefully increase the engines 'on' time enough to provide more power to the wheels, which was my main concern with this bot. At the back you can see a bead on a bent paperclip to provide minimal drag on the back of the bot, although this was later removed as it actually hampered the robot's movement.

You can also see here that I built the solar engine with the heads of the transistors/1381s together to provide more ground clearance. If I were to re-build this bot I would have rotated one side facing upward so the sides would mirror each other, which would have made the build much easier!

Overall this robot moves as well as could have hoped. A lot of power is wasted in the pager motors while attempting to turn over. Despite all the power to the motors, this bot only manages 1cm steps. This is due not only to the flat nature, but also to its length. Like Simon's Flatbot, mine is not very phototropic either.

After building this bot, I came across a post about motor start capacitors; a cap connected across the motor terminals that could help build torque by ramping up power to the motor slower rather than in one big burst, avoiding burning through current in a stalled motor.

Carbot

Carbot (creative name, I know) was designed to be a simple miller engine that sticks to the inside of your car's windshield. With its outward facing solar panel, it will build up charge on its three 5600uF capacitors and release that energy in one big burst on the bulky DC motor in the center. The load on its shaft is a bit heavy (the LEDs on the propeller are non-functional), so the solar engine needs a decent amount of charge to build any momentum. The inspiration for this bot was taken from the now defunct Jim's BEAM Page. Jim made an impact with his special attention to the Aesthetics part of BEAM. What remains of his designs can be viewed in very poor resolution at beam-online.com

Betabot Photopopper

Betabot was my first attempt at the Miller Photpopper circuit. Up until this point I had only build Fled photopoppers, but I was intrigued by the improved efficiency of this circuit, and I thought I would give it a go. Betabot is powered by a Solarbotics 37 x 33mm solar cell, connected to a 4700uF capacitor. This time around, I chose my components more carefully. Capacitors increase in size with voltage rating, and if I wanted to keep this robot small, I was going to chose a power capacitor with an appropriate voltage rating. This cap is rated at 6.3 volts. Since my miller engines would be firing at approximately 3.4v, I wouldn't have to worry about exceeding the capacitor's voltage rating.

I couldn't be happier with Betabot's performance. He quickly scoots across the desk under lamp light. The miller photpopper circuit is my favorite circuit to build, and Betabot would not be the last. Changing values for C2 and C3 will increase or decrease the step size of the bot. If you're building a bot that needs longer steps, increase C2 and C3 appropriately. Keep in mind that you may have to increase C1 as well. You can't pull more power per step if the main power source is empty!

This brings up another good topic that was originally written by Wilf Rigter regarding the capacitance of C1 in this circuit (or the Miller solar engine as well).

With a small storage cap that is nearly discharged at every trigger event, the avarage storage cap voltage and therefore average solar cell voltage is well below the peak power point voltage. By adding a much larger storage cap across solar cell that discharges only a small fraction of its stored energy at every trigger, the capacitor voltage will only fluctuate a few 100 mV allowing the solar cell to operate continuously very near the peak power point. The trigger of the SE must be set to correspond to this optimum operating voltage and the SE on time should be limited to avoid deep discharging the storage cap.

This larger cap must have low resistance to delive a high current pulse and is usually one 1F - 2.5V gold cap or two 1F - 2.5V gold caps connected in series running at 5V. The current pulses will cause a small drop in voltage across the internal resistance. This large cap can also can be a 1F - 5V high internal resistance "memory" cap in parallel with the 3000uF electrolytics.

The drawback is that the large cap requires an initial long charging time after which the SE will pop much faster. 
https://groups.yahoo.com/neo/groups/beam/conversations/messages/53514 

Alphos

After a 14 year hiatus from BEAM robot building, I dug out my parts after moving into a new apartment, fired up the Weller soldering iron, and Alphos was born. He is yet another Fred Photopopper built using Ray's guide. He is built with two motors salvaged from an old VCR, and two 4700uF caps wired in parallel to provide 9400uF! This kind of power gives Alphos interesting behavior with extremely long jumps that cause him to navigate in alternating 180 degree turns! Functionally he could benefit from removing one of the 4700uF capacitors, but I enjoy having some variety in the robot farm. You can see the newer Solarbotics solar cells on this bot versus the older, lighter panasonic sunceram models.

Syko

Syko is a Bicore based light tracking head based on Wilf Rigter's Solar Powered Smart Head circuit V1. Sadly, I could never get him to function properly. He was relegated to the parts bin and scrapped for a separate project years later. His motor is a Copal 60 RPM gear motor. Connected to the shaft you will see a motor clamp repurposed from a screw terminal block. They are 3mm in diameter, made of brass, and have two screws to keep the motor shafts secure and in place. Connecting things to motor shafts is tricky, and these little clamps are a godsend. I haven't used the ones from Solarbotics, but the ones I purchaed on amazon here worked just fine for me.

ITP Fab - Motor Mounts from Jeff Feddersen on Vimeo.

HipHopper

My first experience with the 1381 voltage detector. This circuit used in HipHopper is the 1381-based solar engine. He is powered by a 24 x 33mm Panasonic cell connected to a 1.5F PowerStor super capacitor. His body is built on a paperclip chassis, and when firing, this robot will bounce all over the robot farm. Some robot builders call this style a Vibrobot.

1381's are increasingly hard to find nowadays as they have been discontinued. Luckily the folks at Solarbotics tracked down a direct drop-in replacement for the 1381 named the MCP112.

Twitch

Twitch is another Fred Photpopper. Similar to Bit, but with double the solar panels and a beefy 4700 uF capacitor. This bot was the tougher of the two, with active pops of 2cm every second or two in full sunlight. I followed the same free-form tutorial from Ray's website. He was built along with Bit in the year 2002.

Bit: Fred Photopopper

Bit is the first BEAM robot I ever built. He is a Fred Photopopper. I used Ray's Tutorial to free-form it. Free form means to omit the use of circuit boards or PCBs. I used pencil erasers as wheels, which the motors barely had enough torque to turn. This bot may have benefit from a smaller wheel diameter, pearhaps heat shrink wheels. I have always lagged behind in the Mechanics part of BEAM robotics. Bit is powered by a Panasonic sunceram solar panel. These cells were discontinued about 8 years ago and replaced by Solarbotics with their own brand of panels; slightly more efficient but heavier due to the epoxy coating.

Welcome to Bold City Beam Robotics

Welcome to my new beam robotics blog. I will be showcasing the robots I have built and ones that I build in the future. BEAM Robotics certainly has fallen into obscurity as a hobby in the last ten years, but I find it fun, and it keeps my mind occupied.

I am currently doing my work at my computer desk, which feels very cramped at times. Although I find the ability to look up circuit diagrams or reference data sheets very helpful. Eventually I will find a better work station where I can conveniently store all my components. But this will have to do for now.