This robotic casket is a Halloween project I have been working on for years. I usually get started around the first of October, get lost in my A.D.D., and I never accomplish everything I wanted to do on any given year. But that's O.K. because in this case it’s perseverance that wins... I just never gave up.
This video of the casket is already 5 or 6 years old. The mechanics were primitive and unreliable and control was done via the printing port of an old laptop, which had to be running Windows 95 to support my means of printer-port-access using Q-basic
This years video is still a work in progress...
When I get the new video posted you'll notice very little change in its operation but it has evolved enormously. In the above video, the LID_LIFT system mechanism was a primitive pulley system. A thin nylon rope was being pulled through a series of pulleys (to leverage the lift) and the rope was being rolled up and unrolled on to a spool which activate motion. Today it has evolved to a rocker/fulcrum mechanism being moved back and fourth/up and down by a push-rod with heimjoints on either end. Since this video, all mechanical mechanisms have improved. The casket, mechanically speaking, is much more reliable than it has ever been. Developing the mechanisms has been way too much fun. Not without frustration, but success is always sweet.
Over the years the project has evolved mechanically, electronically and how it’s all control. For most of the years that I have been working on it, control of the electronics and mechanics has been provided by a computer printer port. However, last year, 2010, I started using an Arduino micro-controller. If you are in to robotics/animatronics and you have not discovered the Arduino, you don’t know what you’re missing
As much fun as improving the mechanical aspects of the project have been, the ability to control those mechanisms is where the creative ideas really begin to take hold. In all the years that I have been working on it, the must exciting event of this project so far has been the introduction of the Arduino. Having the Arduino has forced me to improve mechanical mechanisms so that they can reliably respond to the instructions of the Arduino.
I am anxious to complete the video and share details of the evolution of this project. It has been a great individual development experience. In other words... it's been a lot of fun.
About the Casket
The casket is actually a wooden frame covered with canvas. The skeleton is from two sources. The skull was originally a stand-alone prop that had a motion sensor to activate it. movement in front of it would trigger the flapping jaw and eye falling out. The rest of the bones are a cheap plastic mold set, but they work.
There are three motors to power the mechanic of the casket. One little 3.5V motor in the skull (original motor), and two large power-window motors out of a 88 Ford Taurus. The one sitting up and laying down the skeleton is a bit of an over-kill, but a hefty motor was required to lift and lower the lid. Lifting the lid of the casket from the inside, at the swing of the hinge, needs a lot of power. To interface the motors with the Arduino (or previously with printer-ports) I needed a motor control interface circuit that could use low voltage/low current (5V @40mA max.) from the Arduino and converts it to 12 volts and high current (2A-3A) to operate the two big motors. I used a MOSFET H-Bridge design I found out on the internet (Mondo Tronics, Maxi Dual 2 H-Bridge Circuit Kit, #3-773) .
The Maxi Dual 2 H-Bridge Circuit controls two motors. It uses optocouplers for voltage/current protection (isolation) between the 5 and 12 volt sides. It can safely switch the 12-volts on and off, fast enough to take advantage of the Arduinos PWM features, while running the motors in either direction. I found the Maxi Dual 2 H-Bridge board a nice fit for the caskets power needs, but if something on the board burns out it's almost impossible to repair (remove and replace components) without damaging the board. Throughout my learning curve, I have gone through 3 of the Maxi Dual 2 H-Bridge's. At $60.00-plus, controlling the motors was becoming too expensive. I finally expanded my IC inventory to include all the components of the Maxi 2 H-Bridge and designed a project-board layout based on Maxi-dual. It's a single-sided project board, I order 25 and got them for like $30. My design on the project board is much larger than the original design, but it's much easier to de-solder and replace components. And it goes without saying... it's much more cost effective.
The Maxi Dual 2 H-Bridge Circuit controls two motors. It uses optocouplers for voltage/current protection (isolation) between the 5 and 12 volt sides. It can safely switch the 12-volts on and off, fast enough to take advantage of the Arduinos PWM features, while running the motors in either direction. I found the Maxi Dual 2 H-Bridge board a nice fit for the caskets power needs, but if something on the board burns out it's almost impossible to repair (remove and replace components) without damaging the board. Throughout my learning curve, I have gone through 3 of the Maxi Dual 2 H-Bridge's. At $60.00-plus, controlling the motors was becoming too expensive. I finally expanded my IC inventory to include all the components of the Maxi 2 H-Bridge and designed a project-board layout based on Maxi-dual. It's a single-sided project board, I order 25 and got them for like $30. My design on the project board is much larger than the original design, but it's much easier to de-solder and replace components. And it goes without saying... it's much more cost effective.
My motor control board on a project board
