A few months ago, I reviewed Servocity camera slider. As cool as it is, one thing that was missing from my initial build is a way to automatically stop the slider when it gets to the end. If you’re watching it, as I was before, this isn’t a problem, but if you’re taking a long time-lapse, an automatic stopping method would be needed.
Servocity’s answer comes in the form of two easily-mountable limit switches (See Parts list later in the post) along with two diodes that allow for current to go one way when the switch is depressed but not the other way. In other words, you can reverse the motor and back the slide mechanism off of the switch, but not move into the switch more, preventing motor damage.
Here’s the slider auto stop wiring diagram that I came up with. Note that I’m not an electrical engineer, but sometimes I try to pretend:
Power is applied where it says “+-“ depending on which way you’d like the motor to go. Switches stop the carriage on either side, but there is a diode wired in (symbol should have another line) that allows current to bypass this switch if the motor is turning the correct direction. I guessed* on diode direction, but you’ve got a 1 in 4 chance of getting it right the first time.
Here’s a video of the resulting slide. Note that I’m using a 3 volt battery pack, underpowering a 10 RPM motor to get a much slower speed.
This should be quite useful for time-lapses, or any time I don’t want to ruin my motor!
Here’s my full parts list for this setup:
As cool as this is to have the slider stop automatically to preserve your motor, if you’d rather have it “bounce” back and forth, here’s an interesting idea/wiring setup from Cheesycam.
*Servocity originally sent me the wiring diagram below, which can supposedly make the motor switch direction automatically. I tried to hook it up, but didn’t get it to work this way. The diodes were, however, pointed in the correct direction when rewired. I was using their speed controller, which stopped working at some point after this experiment, so maybe one has something to do with the other.
Edit 1/19/2015: I decided to try this controller again, and it worked both when hooked up to my wall power supply and a 9 volt battery. Maybe something was going on with my power supply, so I guess the moral is to make sure something is actually broken before panicking.
Regardless of these issues, I’m happy with my results now. The setup uses the same components as shown in this diagram, but configured differently.