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.