Elevator "Up" Date
The elevator mechanicals - RIP old drawer hardware...
I've been working on the mechanical part of the elevator project lately, and I thought I had an easy idea - use some of the drawer runners, the ones that have the little wheels that the rails ride on.
I figured I'd just use one rail for a guide, and two of the little wheels to attach to the elevator car.
That didn't work because of the way the rails are constructed - they are only shaped to cradle the wheel on one side, and are flat on the other. That means putting the wheels into the rail vertically would cause the car to flop out of the flat, open side.
I put up two rails next to each other, with the curved (closed) sides on the outside, and that was enough to keep the wheels from flopping out. I superglued some of the drawer rail parts together well enough so they would slide without much friction. I then glued some other wood pieces to it to create a test platform. It's pretty ugly to look at from the back, but it works, and it is enough of what I would call a "Proof of Concept" to be happy with it.
The next challenge was to get the motor working with the rest of the circuit. For all of my testing of the ultrasonic sensor (the one that tells the program how far the nearest object is) I used a tiny toy motor. It doesn't take much power to run that tiny motor, but the bigger motor I am using to raise and lower the elevator car drains a lot more of the power from the rest of the circuit. As I was setting everything up, I noticed that the ultrasonic sensor was not working at all if I hooked up the bigger motor. I went back to my book, "Arduino Cookbook" and checked the wiring diagram again. I knew I needed a second power source for the motor, and I had one setup for that, but I discovered that I hadn't hooked it up correctly. The diagram got me straightened out.
I set the program to raise the elevator car until it was about 3.5 inches from the sensor and hooked up the really fancy pulley system to give the elevator its final test.
The Moment of Truth
A Few Pictures
The setup at the bottom of the rails is the sensor and the power supply for the motor. The sensor is the two small metal cylinders - one sends out a signal, and the other receives it as it bounces back. The time between the "sent" and "received" times can be converted to a distance by the program.
The red light is part of the power supply for the motor, and the black cord coming out of it is plugged into a power strip that's not pictured.
At the top of the elevator rail is the Arduino Uno board (the blue one) and a breadboard that contains a chip called an H-Bridge. It's the H-Bridge's job to control the motor based on the Arduino's commands, turning it on and off, and setting its speed and direction.
You can see the string wound onto a threaded rod, attached to the motor. This raises and lowers the elevator.
M helped me measure the distance between the sensor and the bottom of the elevator car. About 3.5" which is what I was hoping for.
I still have some work to do - it's not an elevator if you can't get the car back to the first floor! Next up, I'll add some buttons to the circuit to allow a user to control its up and down motion. That will require some changes to the program to handle the button presses, and to know where the car is. I don't want the car to keep going up if it's already at the top, and there's no need to let it back down if it's already at the bottom.
I'm also going to create a better rail system than what I have. It works, but is not a very elegant solution, and everyone knows that if there's one word that describes me, it's "elegant." (Maybe not.)
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An updated shot of some of the components - the ultrasonic sensor is now soldered to a small circuit board instead of plugged into a breadboard. The wiring is more complete and it's been tested. Some of my later posts in this blog have a link to YouTube videos of it in action.
