This is a very simple and fun project for kids as well as adults. Using a small pumpkin as a circuit board I created an LED face powered by a 9v battery. This can be a neat little Halloween decoration for work or home. Now, on to the instructable.
Step 1: Materials
The main materials for this project is a little pumpkin (bought for about 70cents), a couple resistors and 7 LEDs.
5 LEDs were used for the pumpkin face and 2 for the eyes. Two current limiting resistors will double as eyebrows for the face.
Step 2: Circuit Design
- The voltage drop across these blue and red LEDs are 4.5V and 2.2V respectively.
- The voltage across the resistor with a 9v source and the blue LED in series is 4.5V
- The voltage across each resistor with a 9v source and the red LED in series is 6.8V
- The power dissipated by both resistors is ~90mW
If you are going to try different LED and resistor configurations here are some guidelines.
- Connecting your resistors in parallel rather than in series is a lot easier since you have to do the soldering inside the pumpkin.
- If you use blue LEDs you will not be able to hook them in series with a 9v source since there is typically a 4.5v drop across the high intensity type.
- If you are hooking the LEDs up in parallel like we are here and you use a lower valued resistor (<100ohms) you will probably need one with a higher power rating
Step 3: Cutting Open the Pumpkin
Use a knife cut a hole in the bottom, remove the inside pumpkin seeds with a spoon.
Once most of the seeds are removed you can use a paper towel to clean it out.
Step 4: Adding the Components
Push the the LEDs and resistors into it to the pumpkin to make a face.
Here we use 5 blue LEDs for the mouth and 2 red LEDs for the eyes with the resistors as eyebrows.
Step 5: Wire It Up
Twist and solder the leads of the LEDs togther.
To keep everything in place you can use hot glue or electrical tape.
Attach the 9v and GND connections to the 9v connector.
Step 6: Let It Glow
Connect the battery, turn it over and you have a pumpkin with an LED face