Background
This is a project that has been simmering on my TODO list for a handful of years. I dreamed it up and go
t the parts, then did nothing. Then I started working on the conveyors, and did nothing. Finally this year I decided to finish it once and for all, and I am pretty happy with the outcome. The gist is a toy block making plant (Santa’s Workshop) that takes a rough cut of wood, turns it into a nice cube, and then finally into a painted block.
The Mechanics
I puzzled over how I wanted to do the conveyors belts for a while. The first thing was to treat them as actual conveyors (with the wood screwed to the belts), but my concern with that was tension. As the “belts” started to stretch, I would have to continuously adjust the tension so that the belts remain tight. Along those lines, I also worried that if the tension wasn’t perfect, a belt could slip and I would run into cases where the blocks would run into each other between belt one and two.
What I ended up compromising on was to run everything off of #35 roller chain (like the chain on your bicycle, only it is a hair smaller). I purchased sprockets on surpluscenter.com to drive the chains and I used a windshield wiper motor to drive it all. I went with 1/2″ bore with 10 teeth per sprocket as the price was cheap and I could use 5/16″ threaded rod with some 1/2″ nylon spacers (with the center bored out to fit the threaded rod) as the rod for the conveyor. To round it out, I took some wooden dowels the diameter of the sprocket with the chain on it, and put it on either side of the sprocket under the “belt” so it would look consistent across the belt.
Below you can see some behind the scenes videos of how everything is connected. Basically I have a sprocket connected to the wiper motor and this is the main drive. I then connected a sprocket to one of the rollers on each conveyor. At this point, when you run the motor, one of the rods will spin for each conveyor. Next I put another sprocket on every rod (so some rods have two). I then hooked up a small piece of chain in a loop on each individual conveyor. Now when I run the motor, it drives one of the rods on each of the conveyors, and then each conveyor is turned because of their own individual sprocket pairs (this makes so much more sense in the video).
Two things that complicated things slightly was 1) I needed to reverse the direction of the chain for the lower conveyor since it goes the opposite direction of the top two and 2) I added an additional sprocket to the large “driving” chain that I use to make a moose (his name is Harris) look like he is controlling the whole thing.
By using the same number of links on each of the three mini conveyors, everything will always run in sync. This means that if the second block is midway down its conveyor when the third block is just about the “fall” over the edge, it will be in the same location the next time to. So everything is predictable and nothing will happen out of order.
I then had my mother-in-law (THANKS!) sew up some “conveyor belts” made out of a burlap type of material. I lay this over the roller chain and velcro them together. To keep the belt and chain in sync, I used a “connecting link” to allow me to screw the wood to the roller chain (through the conveyor belt) and allow the belt to be pulled around the loop.
The Microcontroller and its Code
This was another Arduino project for me, again the Nano in particular.
The main purpose of the Nano is to monitor when a block reaches a certain point and then start or stop some action. I have 3 actions in the display, 1) a warning light when the wood is about to come out of the chute (I disabled the beeping to as to not annoy the neighbors), 2) a spinning saw blade for when I am cutting the wood, and 3) a multi-color (LEDs) tube for when the block gets painted. On the back of all the pieces of wood I have a Neodymium rare earth magnet, and inside the different wooden boxes I have home window alarm sensors that get triggered when the magnet comes near it (they act as a Reed switch that closes a connection when the magnet gets near). Using those triggers, the micro knows when to start and stop an action. The code is pretty simple and can be found here.
Extras
Two extra pieces I have in the box that I’ve glossed over are the “power meter” and the “saw blade.” The power meter is an analog meter that measure the amount of current passing through it (an ammeter). I had the analog meter lying around, I just needed a way of making it bounce around on its own. What I ended up with was using a flickering LED from Electronic Goldmine that mimics a candle (it has been lying around for about 6 years in my junk drawer). The amount of current it draws depends on what it is currently doing in the flicker. I powered it via the Arduino’s 5V output and put the meter in series and now I have a stand-alone bouncing meter.
The second item was the saw-blade. I used my new 3D printer to print up a design I found online. My wife then painted it silver and I installed it on a tiny DC motor for a kid’s toy. They motor spun it WAY to fast, so I had to run it off of 1.5VDC to get it to a more reasonable speed. In the future, I might add some sort of design to the saw blade in paint so you can tell it is spinning easier.
Power
This is a pretty low power display and in all it draws about 0.8A at 120VAC (which equals 96W). Almost all of the power is going to the lights which are incandescent C7 bulbs. If I change the lighting to LEDs, I will drop the power even more.
I am running the non-lighting portion of the display off of a 12V laptop charger. I drop the 12V to 5V and 1.5V via some buck converters.