Halloween is such a fun time with kids and I decided that I wanted to make something special this year. At the time that I was pondering what to make I saw a video online that showed a bunch of small children getting scared by a Jack in the Box. For the record I do not advocate scaring small children, but it was the inspiration I needed to begin writing my tenth Instructable about a Jack-in-the-box with twist. This is an original Schockmade design.

I am not going to give much detail on the design steps of this build, but I did use Tinkercad to design this project. Tinkercad is a free program that I find very easy to navigate.

Initially I thought about building this project using some of my Son's Lego Mindstorm pieces, but then I settled on making something with simpler circuits and a hand powered mechanical drive instead. Mainly because I would have had to give the drivers and motors back to him after Halloween ends thus rendering my build useless.

Step 1: Parts List and Safety Warnings

Parts list:

3D printer or access to one - I have a Dremel 3D20 Idea Builder that prints in PLA

LED lights - I bought mine from Sparkfun.com

Batteries - 2 AA

wire - 18 or 20 gauge

switch - I bought mine at an auto parts store

Tools: wire cutter, wire stripper, soldering iron or station

Tooth brush or scrub brush

550 Paracord (Optional: I used it for visual effect on the outer arms)

Paints and brushes

5 minute epoxy

super glue

Safety Warnings:

Work with paints, soldering irons, and 3D printers in well ventilated areas. Always wear proper protective equipment such as safety glasses, gloves and a respirator when recommended by the manufacturer.

Use caution not to burn yourself if you use a soldering iron or hot glue gun on this project. I used both.

Step 2: Snake Head

After deciding what I wanted to make, a Jack-in-the-Box, I needed to find a unique object to pop out of the box. I found just what I wanted from "SSilver" on Thingiverse with his project Sir, Snake. I altered the files so that I could add LED lights to make the heads glow.

All three moving snake heads are printed in a translucent PLA material and the two outer heads are painted with a single coat of model paint and acrylic paint. I took care not to get paint onto the eyes as I want them to glow from the LED lights embedded inside.

When altering the heads I opened up inside of the snake heads with cylinders so that there is a cavity in them that houses the LED lights and wiring. This also gives the head less material that light needs to penetrate to reach the eyes. See photos during the printing of the heads to get an idea of what I mean.

Step 3: Arms to Hold the Heads

I decided that I wanted two heads on the outside of the box that move as well as the head inside the box. I made some holes in the lower box to drop the arms into and gave them motion with an oval wheel that turns via the knob on the front of the box. I made channels through the middle of the arms to pass the wires through to the LED lights located inside the heads.

I had to come up with a way to release the large snake head from the box. To do this I weighted the head toward the front so that it falls forward when released and designed a catch to hold the head in place until a knob on the oval pushes the release at the top of the rotation. I did add a rubber band to the head to bring it down with more force, but it is not really necessary.

The catch and the knob on the oval that release the catch are visible in the second and third photos. The arms that hold the outside heads stay in place on the oval wheel simply by gravity and a nodule on the outside of the box to keep them in place.

Step 4: The Boxes

I made the box in two pieces to allow for enough build volume with my printer. Total outer dimensions of the boxes once assembled are roughly 8 1/2" H x 4 5/8" W x 4 5/8" L .

The lower box is used to house the electronics and the mechanical mechanisms. The upper box is used to hide the surprise, a large flashing snake head, until the knob is turned.

I wanted to add a skull and cross bones to the front of the door of the upper box for effect. I will highlight how I did this as it is a handy skill that I use for all kinds of builds. First conduct an internet search for a logo you wish to use. Basic two dimensional designs like logos or tattoo artwork work best. In this case a basic skull and cross bones. After the desired file is located I save it as a JPG file. Then I use this free program, https://image.online-convert.com/ to change it from a JPG to an SVG file. To convert the file click on "image converter" on the left side of the page and then click on "convert to SVG" from the menu on the left. Next click on "chose file" and select the image that you saved as a JPG. Next click "start conversion" and then save your new SVG file. This file can now be loaded into your design software, sized as needed and added to your design. In this example I "grouped" a skull and cross bones with the door that opens to release the snake head. For those unfamiliar with grouping, it is the process of joining two shapes together in the design process.

Step 5: LED Lights and Wiring

The LEDs that I used require voltage of 3 to 5 volts. So I chose to power them with two AA batteries wired in series thus creating 3 volts. The power from the batteries is routed to the lights through channels inside of the arms. There are a total of 5 LEDs on the circuit. The two LEDs located inside of the outer heads are white lights, the two LEDs in the back upper corners of the box are slow flash RGB lights and the one LED inside of the large head is a fast flashing RGB light.

The wiring is very simple. All of the Positive (+) leads from the LEDS are wired together and soldered to one side of the switch. The Positive (+) wire from the batteries is wired to the other side of the switch. All of the Negative (-) leads from the LEDs are wired directly to the Negative (-) wire from the battery pack.

Step 6: Painting

Prior to assembly and testing I decided to paint the parts and trust I had done a decent job of designing the build. I figured that I was close enough and that I could fine tune anything that did not work. I was mostly correct in this assumption.

I saw a couple of Instructables that mentioned using salt to create a weathered look and I was anxious to try the technique on the door. I chose my paint colors based on some paracord that I had on hand. The base coat is a dark olive green and the accent colors I used are black and light sage green. I sprayed the parts with the base coat and then covered with black paint the areas that I wanted accented such as the eyes and area between the skull and cross bones. Water was added to the top of the paint after it dried and then salt sprinkled into the water. After the salt has dried you can spray on the top coat in a single coat.

It is fun to scrape off the salt to see the layers exposed from below. I used my thumb to rub some salt off the door and then finished with a scrub brush. I am impressed with the results and would like to thank those who have shared this process as I never would have thought of it myself. For the record if you are noticing that the salt pattern in the photos and the final door pattern do not look the same you are correct. I had to reprint a shorter door so that it did not hit on the bottom box and hang up.

For the painting of the boxes I simply painted with the base coat and finished with some black paint randomly sprayed on top. This is a very quick process and has a cool effect.

I added some paracord tied in a cobra pattern to the upper ends of the outer arms to add weight and give an added visual effect to the project. This cord can not be tied too far down the arms though as it will interfere with the arms' movement through the slots as they move in and out.

I used a snake head for the knob on the front that moves the arms and releases the surprise. This was painted with all three colors. The entire head was painted in the base coat, the top hat and eyes were oversprayed in black, and the bottom of the skull/fangs were oversprayed lightly in the light sage green.

Step 7: Final Fit and Assembly

I added a rubber band to the catch to hold it firmly in place and another one to drop the head quicker. Neither are necessary, but both do create better performance.

I cut a nail off to anchor the large head's arm to the pivot point.

I glued the wires to the boxes after wiring and routing them.

The top box is glued to the bottom box with careful alignment.

The shaft is held in place with the rings seen in Photo 4 above. One ring was used to keep the shaft from shifting within the box. The other ring I used to further anchor the oval wheel in the correct location.

The oval wheel is carefully glued so that it properly hits and releases the catch.

I added an adapter plate to use a different switch that I had on hand because the original switch was too large to fit into the design. It hit upon the wheel inside.

Mostly my initial design worked as planned. I did make some minor tweaks to get everything lined up just right and working, but overall I am happy with the results and enjoyed the build. In total it took longer than anticipated to complete, but it usually does when making a custom design. Print time alone is close to 30 hours.

The borrowed head design is Creative Commons-Attribution/Share Alike so I am able to use it and I did give reference to the creator.

Please feel free to comment or ask any questions.