1. 1N5408 Diodes (~21 for 18 volts)
2. Soldering Kit (soldering iron + solder)
3. Insulated copper wire (~3ft)
4. Wire stripper or cutter
5. Thin walled copper tubing (~3/8″ OD, 1/4″ or larger ID)
6. Hand held tubing bender (optional)
7. Magnesium Oxide powder (50-100g)
8. Cement powder (portland, 5-10g)
9. Water (100-200g)
10. Mixing container
12. Vibrating toothbrush (optional)
13. JB weld or any food-safe epoxy (melting temperature over 300C)
14. Voltmeter (optional – for testing 5 volt node)
1. Solder a string of diodes closely in series (1/2″ of spacing between or less) as shown in “Solution” figure above. At the 5 volt node, solder a copper wire long enough to reach the end of the tube. This node can be found using a voltmeter, or you can estimate it to be 6 diodes away from ground. This wire will be used to charge a phone. At each end of the diode chain, solder copper wires to serve as leads to the power source. All copper wiring should be insulated anywhere they are not electrically connected in order to prevent shorting.
2. Place the diode string inside the copper tubing such that there is the same length of copper lead inside of each end of the tube as shown in “Solution” figure above.
3. Bend to fit into a Hydroflask (opening = 2.1″ diameter) using a hand held tubing bender, or by hand. Try not to make any kinks in the tube as this could cause shorting.
4. Create composite by adding 10 grams of MgO to every 1 gram of cement, and mixing dry. Next, add water little by little and mix as you go until your composite is the consistency of whole milk.
4. Fill the tubing with composite. A funnel can aid pouring and touching the tube with a vibrating toothbrush helps air bubbles escape.
5. After 4 days, seal the ends of the tube with JBquick or any food safe epoxy. You are ready to cook with solar!
By: Matthew Walker, Amanda Stahler, Michaela Board and Jessica Wei