This project shows how to convert a $1 Solar Powered Flower into a pulse motor. The video shows the motor in action while operating under a desk lamp. It works even better in sunlight. This conversion is reversible, so the motor can be removed and the sun flower parts reassembled and restored.
Theory of Operation
Light energy from the solar panel is stored in a capacitor. A timer circuit dumps electrical charge from the capacitor to a coil mounted on the base. When pulsed, the coil is an electromagnet that pushes a permanent magnet mounted on the end of the rotor. When timed just right, each magnet is given a little push every time it swings by the coil. It's similar to pushing someone on a swing. Just at the right moment, a little push keeps it going.
Step 1: Disassemble the Sun Flower
The first step is to disassemble the sun flower. No tools are needed. All of the parts simply snap together.
1) Pull the base apart
2) Remove top two pieces
3) Remove Sun Flower and Leaves
4) Move solar panel to the side
5) Lift base top straight up to remove
6) Save the parts in case you want to reassemble your sun flower
7) The Sun Flower Base with coil, circuit board and solar panel are used to build a motor.
Step 2: Required Tools
A few tools are needed:
1) A hot glue gun is handy but not absolutely necessary. You may use white glue or wood glue.
2) A ruler is needed to accurately measure parts.
3) A pocket knife or utility knife for carving wood.
4) Transparent tape for attaching magnets
5) Scissors for cutting tape into strips.
6) A small piece of sand paper for smoothing wood cuts (optional, not shown)
7) A very small drill bit (#65 is about the size of a sewing needle. (Optional, not shown)
Step 3: Materials
A few scraps for materials are used to build the motor
1) Two or four small 5 mm diameter magnets. Thickness does not matter.
2) A plastic drinking straw for a rotor. There are several different diameter straws. This one is large enough 5 mm magnets to fit inside.
3) A 1/4 inch dowel rod is used for support post. A total of about 6 to 8 inches is needed. An old chop stick should work, too.
4) A sewing needle is used for an axle. Other materials would work as an axle, including: hat pin, piano wire, straightened paper clip, etc.
5) A small piece of insulated wire. The wire shown is about 3 inches long, 22 AWG. The diameter of the wire is not critical.
6) A 2 inch piece of 3/8 inch wide balsa or popsicle stick.
Step 4: Build Support Structure
1) Measure and three dowel rods approximately 2 inches long.
2) Trim 1/4 inch of each dowel rod to fit inside the sun flower base supports
3) Mark one of the three dowel rods 1 1/2 inch above the trim mark and drill a small hole for the axle (sewing needle). For softer wood, you may be able to make a hole without a drill bit. A piece of wire may be used to hand drill a hole. A No. 65 bit is used for drilling circuit board holes.
4) Cut 3/8" wide balsa wood, 1 1/2 inches long. It's better to cut this piece a little longer than too short.
Step 5: Build Rotor
The next step involves building a balanced rotor:
1) Carefully measure distance from axle to coil. Subtract a little to allow for coil clearance. The rotor length will be twice this measurement. The idea is to get as close to the coil as practical without hitting it.
2) In this example, the rotor length is 2 - 5/8 inches. Your exact length may need to be adjusted, depending on your build. Use scissors to cut the length,
3) Stick the needle through the center of the drinking straw. Make sure it goes straight through. Spin it with your fingers and check for any wobble. Make it as balanced and true as possible. One trick is to draw a line to the desired half-length on a piece of paper. Stick the needle with rotor on one end of the line. Mark one end of the straw at the line. Rotate, and mark the other end at the line. Cut the straw to each mark with scissors. Do the best you can, but don't worry if it's not absolutely perfect.
4) Carefully strip two, 1/4 inch pieces of insulation from a 22 AWG wire. Smooth the edges with a knife or sandpaper. These are axle retainers to keep the rotor in position. Slide these on the needle on either side of the rotor.
5) With scissors, cut a piece of tape, approximately 1/4 inch wide and 1 inch long. Stick a 5 mm magnet to the center and tape the magnet to the inside of the straw rotor. Tape another magnet to the other end of the straw. These magnets provide rotor propulsion and also doubles as flywheel weights. NOTE: the direction of the magnets are critical. Be sure to position the magnets to repel when the coil fires. If one or both magnets are backwards, the rotor will not turn.
6) Optionally, stick a second 5 mm magnet on top of the ones already installed with tape. This adds more mass and also a higher magnetic field. My magnets are very thin and came four in a package.
Your rotor is complete! Spin a few times with your fingers and check for trueness and balance.
Step 6: Mount Rotor to Base
1) Mount the rotor to the base. With the left post not inserted into the base, insert rotor needle into hole of the 3/8 inch wide support side (right). Then, pressure fit the left post into the base support. Move post up or down and twist left or right to optimize positioning. The rotor axle (needle) should turn freely in the wood holes. The rotor (straw) does not turn on the needle. Spin by hand. Make sure there is minimal wobble side to side and be careful that magnets don't make contact with the coil. For easy removal, don't glue support posts to the base.
2) For mechanical support, Use a dab of hot glue to attach solar panel wires to support posts. Optionally, use super glue or sewing thread to attach.
3) Place your motor in sunlight or under a lamp to see it work. If the motor doesn't spin, check your magnet directions. If mounted backwards, the rotor magnets will pull towards the coil. When mounted properly, the magnets push away from the coil when pulsed. Also, be sure the rotor turns very freely and is balanced. When the rotor is stopped, one side should be slightly heavier and face down toward the coil. This will allow the motor to self-start.