I am building a 2 axis robotic plankton feeder. Basically, I have six clear plastic tubes that are sitting in a row. These towers are 6 inches in diameter and they are a little over 6 feet tall. I designed a carriage that slides along a rail with feeding tubes attached to it. The second axis moves the 1/4 inch feeding tubes down into the tower for dispensation and back up again before moving on to the next tower.
A problem that I have is that when I turn of the power to the motor, the extender falls down into the tube because there is very little friction on the slide. The aluminum slide is about 16 inches long and has a plastic gear rack attached to it. The bracket and clips for the ¼ inch feeding tube(s) weigh almost nothing.
(This rack and pinion extender is mounted vertically)
Should I add some Teflon with a spring behind it for a friction stop or something else? I could get some of it (perhaps in a dowel shape) and put it in a tube with the spring and attach that to the carriage.
Another thing that I could do is to try to find a solenoid type brake. Since I have an Arduino controller, it would just require a few extra lines of code. The down side is that I would have to add a couple more wires that go to the carriage. I was hoping to limit it to two wires. That makes it easier to run without e-chain.
Can you think of anything that would work better?