Intro: Homemade Lightbulb
Ever looked at a lightbulb and thought that doesn't look too complicated, I bet I could make one? With this Instructable you can!
This lightbulb is made entirely out of simple, mostly household materials requiring very little in special equipment. The basic construction includes a glass jar filled with CO2 and a graphite filament(Pencil Lead). This makes it a carbon filament bulb analogous to those made by Edison before tungsten became the norm.
Step 1: Supplies
- Jar and Lid
- Pencil Lead
- Maleable Wire
- Heat-Shrink Tubing
- 4 Machine Screws(I used 10-32 1/2")
- 4 Nuts
- 2 Acorn Nuts
- JB Weld
- CO2 Canister
- Short Length of Piano Wire
- Drill and Bits
- Wire Cutters
- Needle-Nose Pliers
- Screw Driver
- Air Nozzle(Only Unusual Tool Needed)
- Voltage Source
- Wire Leads
Step 2: Hollow-Out the Screws
Drill a 3/32" hole through the center of each screw.
Two of these will become vents for filling the jar with CO2 and two will be for holding the wire hangers.
This is much easier if you first drill a hole in a piece of scrap wood to hold the screw in place. You may want to purchase extra screws because keeping the drill straight and centered is difficult and you will mess up at least once.
Step 3: Prepare the Lid
Drill 4 holes in the lid arranged with equal spacing as in the photo.
Use a penknife to score the area around each hole on both sides of the lid. This will allow the epoxy to adhere better.
Step 4: The Hangers
Cut two lengths of wire approximately 10" long.
Clamp the wire in the vise grips with about 1.5" sticking out on one side.
Hold the length of piano wire against the vise grips such that it is perpendicular to the wire.
Use the needle-nose pliers to twist the wire around the piano wire.
Repeat for the second hanger.
Note: For my malleable wire I used 19 gauge stainless steel, though any solid core wire of similar gauge should work.
Step 5: The Hangers Cont.
Release the vise-grips and remove the piano wire, there should now be a nice coil to hold the filament.
Take a piece of pencil lead and place it in the coil. It will be quite loose.
Using the needle-nose pliers, gently adjust the coil so that it tightly holds the pencil lead. Only make small adjustments at a time.
Cut any extra length off the end of the coil.
Repeat for the second wire.
Bend the two wires such that they will hold the pencil lead vertically in the center and so the long leads align with the holes in the lid.
Step 6: Insulate the Hangers
Cut a 1" length of heat-shrink tubing.
Place it on the wire hanger at the area where it will go through the lid, about 4.5" from the bottom of the longer lead.
Apply heat to shrink and adhere the tubing to the hanger. A candle is the easiest way to apply heat though a lighter or even matches will work as well.
Repeat for the second hanger.
Step 7: Attaching Screws
Mix a small amount of JB Weld and apply to the outside of the heat-shrink tubing.
With the head facing down, carefully place the screw over the tubing and JB Weld. The epoxy needs to fill the hole in the screw as this needs to be an airtight seal. Also be sure that the screw is straight on the wire hanger.
Repeat for the second hanger.
Step 8: Mounting on the Lid
Mix a small amount of JB Weld and apply to the underside of the screw head.
Push the screw through the hole in the lid with the head facing down(inside the jar).
Tighten the nut on the opposite side of the lid.
Again be sure the epoxy fills any gap as this needs to be airtight.
Repeat for both vent-screws and hanger-screws.
Let the epoxy fully harden for at least a few hours.
Check for a good seal by tightening the lid on the jar and blowing into one of the vents while holding your finger over the other.
Step 9: Final Adjustments
After the JB Weld has hardened place a piece of pencil lead in the hangers to test fit and make any final adjustments to the hangers' positions.
Remove the pencil lead and thoroughly wash(with detergent) and dry the hangers, underside of the lid, and inside of the jar. The interior of the bulb needs to be free of any contaminants that will burn and cause discoloration.
If you have some latex gloves you should use them for the final assembly, otherwise thoroughly wash your hands as well.
Place a new, fresh piece of lead in the hangers being careful not to handle it too much.
Tightly screw the lid onto the jar.
Note: I used 0.7mm lead, though 0.5mm, and even 0.3mm should work as well. In fact the thinner lead will have a higher resistance and should make a brighter bulb.
Step 10: Prepare to Charge
Place your assembled jar in the oven at 180 degrees. It will only need a few minutes to heat up.
While your jar is heating, apply a small amount of silicone to the inside of each acorn nut.
Step 11: Gas Charging
This step should be completed quickly so it may be worthwhile to practice.
Remove the jar from the oven and place on the table.
Use your air nozzle to blow CO2 into the jar via one of the vents. Do this for close to a minute. The cold CO2 should fill the jar while the hot oxygen-containing air will be forced out of the second vent.
While continuing to blow CO2 into the jar, screw an acorn nut onto the open vent.
Remove the air nozzle from the vent and quickly screw an acorn nut onto it.
Tighten both acorn nuts to ensure a good seal.
Note: This is the only step that requires an unusual tool, the air nozzle. I got mine a few years ago at Office Depot. It is meant to be an air duster, however regular canister air dusters will not work. They are often filled with flammable gases such as propane and if you use one you will be creating a bomb, not a light bulb.
EDIT: As suggested by many in the comments, dry ice could be used as an alternative to a CO2 canister. Without heating first, place a small piece of dry ice in the jar and let it sublime into CO2 which will displace the air. After the dry ice has completely sublimed close and seal the vents. Do not seal the jar with dry ice still inside because it will continue to sublime and creative positive pressure which may become a safety hazard. I have not tried this yet, but plan to soon.
Step 12: First Test
Connect your bulb to a voltage source.
When the bulb is first turned on it will smoke a little as it burns the small amount of oxygen left in the jar. Run it for about 30 seconds and then let it cool and the smoke settle.
12 - 24V should be perfect so long as it can provide a high amount of current. I used two 6V NiMH batteries connecting in series.
Optionally, use a multimeter to measure the resistance of the bulb and with V=IR find out how much current your bulb will pull.
However, as graphite heats up its resistance decreases so the resistance you measure before turning on the bulb will be higher than it will be when on. This is one of the reasons we now use tungsten filaments because tungsten's resistance increases with temperature.
Step 13: Completion
The bulb is now completed!
If you are running it from batteries be vigilant that you do not overheat your batteries.
Unfortunately it is not very bright so don't count on replacing your household lighting with it. You can try increasing the voltage to increase brightness, though be careful as the higher voltage you use the higher the current will be.