Introduction: Solar Powered Battle Symet - BEAM Style

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BEAM Solar Symets (a contraction from "Symmetrical Robots") were first built by Mark Tilden many years ago as a way to provide mobile plant-life to the other creatures in his Robot Jurassic Park. Being quite simple by only using one solar-engine circuit, they're quick and easy to build.

These versions use high-power Miller Solar Engine circuits, that make them spin much more madly than their pokey ancestors! If you are new to BEAM, it's a design philosophy that incorporates minimalist electronics, and often, solar power. Want more info? Check out and!

The Battle Symet borrows heavily from the original family of Symets, but these are designed to spin in a circle at much higher speeds.

Step 1: Parts You'll Need

We've made a convenient parts bundle of almost everything you'll need to build this project (not including the tools). You'll have all the mechanical and electrical components needed to start making this fun lil' robot!

Mechanical Parts

1 - High-efficiency Coreless Motor (Solarbotics part #: RPM2)
1 - Motor Mounting Clip (Solarbotics part #: MMFC)
3 - Rubber Wheels on Nylon Hubs (Solarbotics part #: RW)
2 - Paper clips

Electronic Parts
1 - 37 x 33mm Solarbotics Solar Cell (Solarbotics part #: SCC3733)
1 - 0.35F 2.5V Gold Capacitor (Solarbotics part #: CP.35F)
1 - 6.8uF Electrolytic Capacitor (Solarbotics part #: CP6.8uF)
1 - 3904 Transistor (Solarbotics part #: TR3904)
1 - 1381 Voltage Trigger (Solarbotics part #:1381C)
1 - Signal Diode 1N914 (Solarbotics part #: D1)

1 - Short length of twisted red/black wire

Tools Required
- Soldering equipment (soldering iron / solder / cleaning sponge) (HVW tech soldering tools)
- A pair of Needle-nose pliers (HVWTech part #: 43060 or 43061)
- A pair of Flush Cutters (HVWTech part #: 43040)
- Safety Glasses - VERY important when clipping and snipping! (Solarbotics part #: 5330)

Get the parts bundle here!

Step 2: Making the Frame

Let's start with the wire ring that surrounds the Battle Symet.

Unfold one leg of a paperclip, and snip off approximately 1cm. Finish unfolding the rest of the paperclip, and work it into a circle that touches the corners of the solar cell.

Step 3: Soldering the Ring to the Solarcell

The wire ring we just made will short out the solar cell if we just solder it on. We have to use some tape to cover the corner pads, preventing a short circuit from occurring.

Snip off a few squares, and cover up the power pads on the corner of the solar cell.

Solder the circle to the two corner pads that are connected by the fat green stripe, so it sits centered on the solar cell.

Step 4: Assemble the Circuit

Now it's time to solder all the electronic parts to the solar cell. Our MSE solar cells have the circuit for building a MSE right on the back, and it makes robot assembly really easy and fast!

Look on the solar cell's back, where you'll find a printed circuit board (PCB). You can see part numbers that label where to install the various components on the solar cell. Make sure the are installed exactly as shown, with the parts in the right location, and facing the right way!

Step 5: Installing the Motor Mount

Here's a clever way to mount a motor to your robot fuse clips. Pager motors are small and they fit perfectly in fuse holder.

We'll use a fuse holder (part # MMFC, included in the parts bundle) to mount our motor.

Use pliers to "squeeze" the legs of the fuse holder around the paperclip frame, so that it stays in place while you solder.

Note: Don't solder directly to the motor - this is difficult, and you can ruin the part!

Step 6: Inserting the Wheel to the Motor

This is a cool way to insert the wheel to motor shaft.

You've probably noticed that the inside hole of the rubber wheel is too large compared to the motor shaft. Take a piece of wire insulation sleeve and insert it onto the shaft, which creates a snug fit with the rubber wheel.

Step 7: Making the Wheel Holder

This is simply a rubber wheel holder, but it's only a bit more complex part to build than the paperclip ring from the beginning.

The image for this process shows each step, from top to bottom.

1. Unbend the large curve of he paper clip.
2. Cut off the smaller curve.
3. Bend in a foot at each end - this is simply two right-angles. Make sure the tip is long enough you can stick the rubber wheel on (~1cm or 0.4")
4. Mentally divide the long, straight length into quarters. Bend the two outside segments out by about 45degrees (should be ~ 1cm or 0.4" at the bend). Think three dimensionally!

Step 8: Solder the Wheel Holder to the Frame

Take your new body axle,  and solder it to the frame as shown. We're trying to make a nice triangular rolling base for your Battle Symet.

If the axle doesn't look quite right, get another and try again - paperclips are cheap!

Step 9: Making a Protective Shield

Find another paperclip, and unfold it so you can make a matching arc to cap off and protect the wheels.

We'll be using this to also retain the wheels on the axle.

Step 10: Your Robot Is Finish

You're ready to test. Put your bot under some light (sunlight works best, or a bright incandescent lamp works well too), and watch it spin!

Don't forget to make another one to battle with!

Have fun!

Note: If you start adding more weight, the motor may have trouble making the entire robot spin.