For our engineering class, we were challenged to make something that would solve a problem in our world. Immediately we thought about the increasing amount of air pollution on our planet and brainstormed about how we could reduce this. A big contribution to air pollution is the fumes generated from gasoline powered vehicles, so we decided to make a car powered purely by solar energy. The final product was a small, lightweight car, with a main body consisting of a two millimeter thick solar panel wired directly to two rear motors recycled from DVD drives, as well as a single unpowered front wheel. To make the car a bit more stylish, we’ve also mounted a secondary solar panel at the rear of the car in a spoiler configuration which supplies power to two red flashing LEDs.
Hot glue gun, Wire strippers, X-acto knife, Cut Resistant Mat, Steel cork back ruler, Pliers, Soldering iron, Soldering iron scrub/cleaner, Hobby Saw
Materials: One 6 Volt 200mA Solar Panel, One 4 Volt 50mA Solar Panel, Large Popsicle Stick, Balsa Wood, 2 5mm Blue LEDs, Foam Board, Rechargeable AA 1.5v Battery, Electrical Tape, Electrical Wire, 4.7 Ohm Resistor, One 3 Prong Slide Switch, One 6 Prong Slide Switch, 3 Plastic LEGO Wheels, 2 1.5 Volt 2.56 Amp DC Motors, 1 Straw, 1 Skewer, Lead based solder, Hot glue sticks
Step 1: Gathering Materials
We spent day 2 gathering up some of the materials we would need for the solar car.
This included a small foam board, lego wheels, 2 1.5 volt DC Brush Motors, wiring, and our solar panels.
We also tested each solar panel using alligator clips and a multi-meter to ensure they were working at their advertised outputs.
Step 2: Starting Assembly
Next we cut our foam board using an exacto knife and glued it on the front underside of the main solar panel.
In order to stay clear of the solar panel’s positive terminal, we made a small cutout at the front of the bumper that allowed the foam board to remain effective whilst not interfering with any electronics.
We also used a razor blade to cut two pieces of popsicle stick about an inch long to be used as mounting points for the spoiler.
Step 3: Mounting Spoiler and Attaching Wheels
The next step was to mount the spoiler. We hot glued the two inch long popsicle stick pieces on the rear underside of the main solar panel. A little less that half an inch of each mounting point was sticking out from the solar panel. This would provide a platform for us to hot glue the next part of the spoiler onto.
For the part of the mount that raised the actual spoiler, we used two quarter inch sticks of balsa wood, each about two and a half inches in length. One end of each balsa wood stick was about 95 degrees, and the other end was about 100 degrees. We achieved these angles simply by using sandpaper on the balsa wood. Lastly, the 95 degree ends were hot glued to the mounting points, and the secondary solar panel/ spoiler was hot glued onto the 100 degree ends.
We also secured the wheels on the motors by pushing the motors spindles through the holes in the center of the lego wheels and using a touch of hot glue to keep it in place.
In preparation for mounting the motors, we cut another small rectangle of foam board and glued it under the spoiler mounting points. This will provide an extra surface to glue the motors onto other than just the primary solar panel.
Step 4: Attaching the Front Wheel
For the front wheel, we hot glued two 3 inch skewers to the bottom of the main solar panel at an angle so that the car would run in circles rather than straight into walls/ obstacles.
Then we took the front wheel and fed a 2 inch skewer through it. Using two 1 inch straws, we fed the skewer from each side of the wheel through.
Lastly, we hot glued the ends of the straws to the ends of the skewers already attached to the car.
Step 5: Completing the LED Curcuit
After attaching the front wheel, you should have your wires, motors, LEDs and soldering tools ready.
Before soldering things, always make sure you don’t touch the soldered part right after soldering, it might be hot and it could burn your hands, and always wash your hands after soldering to prevent lead poisoning. Also make sure that any soldered parts are covered with electrical tape to prevent shock or shorting of the circuit if two metal parts accidentally touch.
For the LED circuit we started off by wiring the circuit for our 2 5mm blue LEDs one the breadboard. We found that using a 4.7 ohm resistor provided just enough resistance for the current to reliably power 2 LEDs. While creating the circuit we discovered that red, orange, and yellow LEDs actually used up less voltage than blue LEDs. Since voltage wasn't a problem for our secondary solar panel and the blue LEDs we have seems more obvious than the others, we decided to go with blue LEDs anyway. We would recommend using one of the 3 colored LEDs we suggested if your panel happens to be short on voltage.
We make a parallel circuit to make sure both LEDs light up at the same time, then we solder the wires with a 4.7 ohm resistor and solder another wire from the other side of resistor on the smaller solar panel’s positive contact, the wire that left from the LED’s side should be solder on to the smaller solar panel’s negative contact.
Step 6: Completing Motors Circuit
For the motor circuit, we soldered one wire from each motor to the 6 pins slide switch, to ensure the motors spins the same way while they were attached to different side, we make sure that one wire is positive and the other is negative.
Then, we soldered another wire from the switch and tape the other end of the wire to the positive side of battery, the two wires that left by two motors one is positive and other is negative, taped it both to the negative side of the battery.
To secure it all together we added more electrical tape around the battery and the wires so the wires won’t come off from it while the motors are running. We also tape the LED’s circuit separately so the wires won’t touches and burnt the LEDs.
Step 7: Putting All the Circuit on to the Solar Panels
Now we have finished all the circuit and are ready to put it on the solar panels to test it out. First, we hot glue a piece of cardboard on the bigger solar panel right next to the foam board.
Then we hot glue two motors on to the cardboard and the foam board. To ensure the motors won’t fall off, we use electrical tape to secure the motors tightly on the solar panel.
Next are the battery. We tape the battery on the solar panel using the electrical tape. When you tape the battery, try to get it as close to the center of the solar panel as possible. That way, the center of mass stays in the middle of the car.
To mount the switch for the circuit, glue the side of the switch right on the side of the solar panel.
Step 8: Making Finishing Touches to the Car
First, make sure that tape is added to all exposed circuit wires in order to make sure that if two wires touch the circuit doesn’t become a short circuit.
Then, use a steel cork back ruler to measure the dimensions of the top solar panel.
After doing so, cut out cardboard pieces (with an X-acto knife, steel ruler, and self-healing mat) to create a cover around circuit of the top most solar panel.
When doing so, make sure that the user is able to access the switch that controls the circuit for the two blue LED’s.
Then, hot glue the cover together and attach the cover to the bottom of the top solar panel.
Finally, use a marker to label the off and on sides of the switch to the LED circuit as well as the off and on sides of the switch to the motors.
Step 9: Testing and Optional Additions to the Car
Place the car on the ground where light can directly reach the unobstructed solar panels.
Make sure that there are no nearby objects that the car can crash into, before turning on the switch to the motors.
The car should begin moving in a circular direction.
If the car doesn’t move, turn off the switch to the motors and try to troubleshoot (make sure that the circuit is properly wired).
If the car moves in a circular motion, then proceed to testing that the two LED’s on the top solar panel work.
If this doesn’t work, then try to troubleshoot (make sure that the circuit for the LED’s is properly wired).
If everything works, then congratulations! You have successfully built a solar-car.
At this point, you may want to add additional personalizations. For instance, a front, side, and back wheel bumper could be added to make sure that the solar panels are protected in case the car does run into an object when running.
The bumpers could be made out of styrofoam or cardboard cutouts attached to the side of the solar panels. We hope that you had fun during this project!