Animating a static, commercial snowman
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- So you picked up a wire frame snowman at your local home improvement center and now that you've plugged it in, it glows nice and bright but it just stands there. And you want to make it interact a bit more with your viewers by adding some motion. It's not as hard as you might think, but it does involve a bit of DIY engineering, and truth be told, sometimes it turns out to be the one-of-a-kind-I-hope-I-never-have-to-do-this-again kind of engineering! But stick to it, and it'll come together. Here's one way to do it... (The original forum thread is here: https://diychristmas.org/vb1/showthread.php?10500-Another-snowman-conversion&goto=newpost)
- The first thing was to separate the head from the body. A Dremel Moto Tool with appropriate cutter wheel is a good option to cut any wire/welded sections. However, the lights attached to the head were a bit more problematic -- and not wanting to dislodge them, they were kept connected.
- A swivel collar was designed which allowed for the light cables to remain intact. The collar was made in 3 parts, a top and bottom section and a washer spacer. The material chosen was a plastic, kitchen cutting board because they're very strong, inexpensive and rust-proof, although it's a bear to cut. A saber saw or band saw is highly suggested although a hack saw could also be used. The open slot allows the cable to be slipped through into the opening to prevent binding on any cables between the head and body. A picture of the assembled swivel head before final drilling shows how the slots overlap. The washer spacer is important and it should be wide enough to support the weight of the head.
- Holes were drilled around the perimeters of the top and bottom parts for attachment to the wire frame. Small gauge wire was used to "sew" the top and bottom sections to their respective parts of the snowman frame using every 3 or 4 holes. The washer spacer adds distance between the top and bottom to prevent these wires from binding. A lockwasher was used to connect the top and bottom through the spacer and adjusted for easy motion. Lubrication is likely not required, but certainly WD-40 could be used if necessary. The plastic material is also quite impervious to ice and snow, too -- an added benefit!
- The side-to-side head motion in this conversion is accomplished by the use of a cam lever, which allows placing a push/pull actuator elsewhere in the snowman's body and connecting the actuator to the cam with a push rod. As the actuator moves the connection rod up/down, the cam translates the motion into horizontal motion. The same plastic material was used for the cam. Connecting the cam to the head was facilitated with a simple screw eye around one of the wires in the back of the head (see the top part of the plastic cam). This creates a sliding friction/wear point but as motion will be relatively slow and intermittent, it's not anticipated that significant wear will become an issue.
- The cam's attachment bracket became an exercise in extreme DIY engineering. Because one can't buy one of these anywhere on the planet, it's a fun challenge to make this work.
- Trial-and-error also showed it would be possible to bend the ends of the bracket around parts of the snowman's wire frame, solving the problem of physically mounting the bracket onto the frame! Oh... the things you'll learn with DIY engineering!
- A linear actuator was chosen as the "motor" to drive the contraption. A linear actuator uses a geared motor to drive a threaded piston in/out of its sleeve. Actuators incorporate built-in micro-switches to cut power when they reach either end of their throws, eliminating the need to worry about overloading the motor. Actuators are quite powerful -- this one delivers 22 pound of push/pull force over a distance of only 25mm in about 1 second. The faster you need, the less force they can deliver. Because this actuator's throw was only 25mm (about 1 inch), the cam was used to accentuate the range of motion by a factor of about 3, which also has the effect of reducing the push/pull force to 1/3 of the total, resulting in about 7 pounds - plenty of power to move the head from side-to-side. To reverse the actuator's direction, the polarity simply needs to be reversed, which is easy to do with an H-bridge circuit.
- Note: An actuator was chosen over a servo or continuously rotating motor for multiple reasons, the most important of which was sheer power. The head-turning motion need not be super fast but snow and ice can collect on outdoor props where the author lives, adding to the difficulty of making the props move. A servo could certainly be used as well, but a servo with sufficient force to move the head is more expensive and overall, more difficult to control. Also, servos must be continuously powered and usually have a return-to-center function when power is applied. An actuator stays put until told to move. The automatic end-limiting of an actuator produces a finite amount of motion and automatically disconnects motor power, so no monitoring of full motion is necessary. To sequence the actuator's in/out direction, two control channels are required to trigger the electronic H-bridge to reverse the polarity of the actuator's motor. And if the full range of motion requires 1 second of time, applying power for a half-second results in half the motion (either in or out) so it's possible to move the head only slightly and thus, controlling the prop's motion is a simple on/off function -- similar to turning lights on/off -- although two channels are used instead of only one. It's important to note that actuators generally do not enjoy waterproofing, so some care must be taken to weatherproof them. Another considering can be operating temperature and duty cycle. The inexpensive ones such as this example (about $20 US) are designed for about 10-20% duty cycle and continuous use will likely burn them out. Turning the snowman's head is an intermittent, gradual action for perhaps 1/4 to 1/2 second at a time about every 5 to 10 seconds and the auto-limiting switches turn it off anyway when it reaches either end of its throw. Operating temperature in extreme climates -- either cold or hot -- can become more of a problem and may require additional attention.
- H-bridge electronics. An h-bridge is a circuit that switches the polarity of a voltage applied to a load, which then allows a DC motor to run forwards or backwards. It's named because the switching mechanism looks like an "H" around the central DC motor. It's normally used with a microcontroller of some type to trigger the h-bridge to do its work, similar to turning a light on or off. Here's a manual circuit diagram and a sample of a commercially available product. A suitable h-bridge for this project costs about $5 from Amazon or other sources.
- Video of the above conversion, triggered manually before adding the control electronics: CLICK HERE
- Video of the above electronics in action: CLICK HERE
- Video of the fully completed project: CLICK HERE
- Video of another conversion, using a continuous motor and eccentric for head motion: CLICK HERE
- Video of another snowman with two actuators, one for the head, one for the arms: CLICK HERE
- Additional lights for the eyes and/or mouth can certainly be added to the project at the whim of the DIY'er, as can additional motor devices for moving the snowman's arms -- only limited by your creativity and effort!