Snap-O-Lantern Kit Assembly Instructions

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This page is part of the documentation for the Snap-O-Lantern kit.

What's included with the kit?[edit]


See the Snap-O-Lantern kit Bill of Materials for a complete list and quantities.

Tools required for assembly[edit]

Supplies required for assembly[edit]

  • A mini pumpkin! Typical mini-pumpkins are 3-4 inches in diameter. Larger pumpkins can be much heavier, and likely will not work with the kit.
  • Three AA cells

Assembly procedure[edit]

We'll go one by one through the kit components. This guide assumes that you have had some soldering experience. If not, or if it has been a while, you may also want to look at pages 2 and 5-7 of the Bulbdial clock assembly instructions, which go over basic tools and technique. And, if you really are a beginner, there are plenty of good tutorials on line, like this one.

Wire up the eyes[edit]


You have two pairs of wires, and two orange LEDs. Solder the long lead of the LED to the lighter wire, and the short lead to the darker one. Your wire pair colors may vary, but here, the yellow wire goes to the long lead and the blue one to the short lead. You can trim both the leads (as shown), or leave one long to stick into the top of the pumpkin.

First component on the PCB: Socket[edit]


The IC socket goes in the big rectangle in the middle of the circuit board, marked "'tiny2313". One end of that rectangle has a little "half-moon" notch (indentation) at one end. The socket has a matching notch, as does the microcontroller. Insert the socket into the circuit board, making sure that all 20 pins go through the holes, and matching the notched end of the socket to the drawing on the circuit board. Solder all 20 pins of the socket in place.


Next, we'll follow along with the circuit diagram as we populate the ATtiny2313 board. The board provides some of the necessary connections, such as pin 20 to power and pin 10 to ground. It also provides prototyping areas for us to hook up the remaining parts to.

Hooking up the resistors and LEDs[edit]


Using the first 1K resistor, connect pin 8 (labeled T0/PD4) to the top row of prototyping holes directly below, in the second hole from the chip. Use the second 1K resistor to connect pin 9 (labeled OC0B/T1/PD5) to the second prototyping row below, using the hole closest to the chip.

Connect the lighter wire of your first LED to the upper prototyping row, and the darker wire to ground (pin 10 is conveniently nearby and connected to ground).

Connect the second LED similarly, with the light wire to the second prototyping row and the dark wire to the remaining accessible ground location.

Servo port[edit]


Using a zero-ohm jumper, connect the closest hole at pin 12 (labeled PB0/AIN0/PCINT0) to the second prototyping row directly below. Use the next zero-ohm jumper to connect the second hole away from pin 13 (labeled PB1/AIN1/PCINT1) to the top prototyping row below. (These will connect the two range options for the servo motor.)

The third zero-ohm jumper connects the left-most prototyping column to VCC_3 directly to the right. Connect the final jumper from the middle prototyping column to GND_3, also directly to the right.

Finally, install the 6-pin DIL header with one pin in each of the top two prototyping rows and across the first two columns. The tall pins should go up so that you can fit the servo connector to them. The short ends go down through the board for soldering.

Battery box and microcontroller[edit]


Connect the red wire from the battery box to VCC_IN+. Connect the black wire to GND_IN. You can use the holes that would have been for a jack to provide strain relief for the battery box wires.

The final step for assembly of the electronics is to insert the microcontroller into its socket. Note that it may be either an ATtiny2313 or ATtiny4313. Orientation is critical: Make sure that the half-moon indentation at one end of the chip matches that on the socket and PCB. Insert it firmly, as far down into the socket as it will go.

Servo motor setup and testing[edit]


Take the servo horn, and push it onto the servo motor shaft. (Do not screw it in place; its position is not final yet.)

Gently turn the motor by the servo horn until it reaches its stops, first one way, then the other way. The total range is about half of a turn. Locate the center position for your particular servo, which will be halfway between its two ends of travel. Once you know where center is, point the servo horn in that direction. This orients the output shaft in the correct direction. Then, remove the servo horn, taking care to move the motor shaft as little as possible in the process.


Now that the servo shaft is centered, we need to place the servo horn at the correct angle. Orient the servo horn as shown: the horn points slightly above and away from the cable. Press the servo horn onto the shaft.


Use the small screw from the servo bag to fix the servo horn in place.


The servo extender has a few holes for varying the length when attached to the horn. The two small screws (that were not included in the servo bag) will self tap into the pilot holes in the servo horn. However, if you use the hole in the very tip of the servo horn, it may split open, so it is better to use two of the other holes.


Use the two small screws to connect the servo horn extender to the servo horn.


Connect the servo motor to the lower row of the 6-pin header with the dark wire connected to ground on the right side of the board. Put batteries in the battery holder and turn it on. Allow it to go through the full range of motion. The lower position should be the smaller range.


Move the servo motor to the upper row of the 6-pin header to try out the larger range: one or the other position may work better for the size of your mini-pumpkin.

Pumpkin Carving[edit]

Mini-pumpkins are typically available at grocery stores and supermarkets near the larger pumpkins. They are often placed with the decorative gourds. You can usually buy them singly, but sometimes they're bagged in sets of four or five. You may also be able to find them at florist shops for use in fall centerpieces, but they'll likely be more costly than at a grocery store.

Please see the original Snap-O-Lantern article for carving instructions.


You can use the holes in the mounting tabs on the servo motor sides to mount part of a toothpick to help hold your servo motor into your pumpkin. Alternately, you can hold your servo motor down with toothpicks anchored entirely above it. If your servo motor sits too low or unevenly in your pumpkin, a scrap of cardboard makes a good leveling surface.