Have a dark spooky pathway? Do you want to scare those meddling kids off of your lawn? Or, do you just want an automated, and customizeable pumpkin lighting system? This tutorial shows how to make one pumpkin that senses the motion of an unsuspecting passer by, and sends a signal to a nearby pumpkin, which then lights up. If this is timed right, it can make for the perfect scare.

Step 1: Parts

1. An ultrasonic sensor (which was stolen) i.e. secure your pumpkin, otherwise keep it hidden, or even indoors.

2. 2 Arduinos, I used the uno, but the specific type only matters when considering the compactness necessary to fit in your pumpkin.

3. 2 HC-05 Bluetooth Modules, I strongly recommend the zs-040 model.

4. A breadboard.

5. Batteries 9v works, but again, the setup doesn't really matter.

6. A bundle of male to male wires.

7. 3 sets of 4 female to female, or male to female wires.

8. 2 LED's (you may need a set of resistors, depending on the LED you use).

Step 2: (Jack) Ultrasonic Sensor Wiring

Before wiring the bluetooth module for this specific build, go my more in depth project on configuring HC-05 modules to function as master, and slave: https://www.instructables.com/id/Arduino-Bluetooth-...

Then, just follow the wiring diagram above.


1. You are going to want the ultrasonic sensor to face the other way, switch the wiring accordingly.

2. Make sure your bluetooth module is wired in accordance my other tutorial.

3. Start by using resistors on your LED, and if they are dim, just go directly to the pin.

4. If you don't know which pins to go to, go to the code linked at the bottom of this page.

Step 3: (Lantern) Bluetooth Activated LED Wiring

Follow the wiring diagram above.


1. Again, make sure you have gone to my other tutorial, outlining the correct bluetooth module wiring.

2. It is important that you cover up the LEDs on the arduino board, and bluetooth module with electrical tape, for optimal lighting effect.

3. Make sure you use the correct sized resistors for the LEDs you are using.

4. Reference the code below if there are any further questions on the wiring.

Step 4: Finalizing Wiring/Testing

Once you are able to get a working connection between the master, and slave modules, test this setup with the ultrasonic sensor. If it doesn't work, check the indicator LED, then check your wiring, listen for your ultrasonic sensor clicking, and finally, leave a comment.

Once this setup works, switch to female to female wiring. This will clean up the wiring, and allow for re-positioning of bluetooth modules, and the extension of the ultrasonic sensor.

Step 5: Carving Notes

Now, for the fun part! Make sure to do this in a clean area (I chose a Tupperware container). You will also need your chosen carving tools (I used a knife, and a large spoon). You will also need a bowl, and a separate container if you wish to save the seeds.

I will not explain how I carved both of my pumpkins because this is where you can get creative, but keep a few things in mind. First, you are going to need to fit all of the components into the pumpkin, so keep the top opening large enough. The most important things, however, are keeping an opening because the bluetooth modules don't do well enclosed in a pumpkin, and finding a way to place the ultrasonic sensor.

If you come up with a unique way of doing this, please post pictures below.

Step 6: My Method/Results


Above is a picture of both of my pumpkins... as the one on the left senses that I am in front of it, the other lights up. The video at the beginning of this instructable is of my sister walking by Jack, and witnessing Lantern light up. My method for mounting the ultrasonic sensor was giving my pumpkin an eye patch made of duct tape, and drilling out holes which I put the ultrasonic senor through. I mounted my bluetooth module near the right eye hole. The other bluetooth module is mounted near the mouth opening of the other pumpkin. Notice the larger pumpkin is carved to look scary. There are many ways of doing this, but my favorite is a large serrated mouth.


In the picture, the two pumpkins are placed closely together. For the actual setup, I placed Jack outside of a bush, facing toward the path through my yard, and placed Lantern facing towards Jack further along the path in the darkness, about 3 feet away. It is important to have Jack away from noise, and out of the path of falling leaves. Lantern just needs to be in range. Finally, the effect is better in nearly complete darkness, where jack is nary detected. That is all, have fun!

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