Potentiometer Autonomous Selector Switch

So, our team saw a video by another team which showed a cool Autonomous Selector Switch: https://www.youtube.com/watch?v=2nsJ9RqT_G0

We really liked it and built a version of our own which includes colorful zip ties and nylon lock nuts.


We are really synced about this selector switch, but our coach wanted us that potentiometers sometimes go out of whack and that we should have a LCD screen to as well or just do straight with an LCD screen.

Do we need an LCD screen or will we be fine without it?

Also, just generally speaking, is it worih it to have an LCD screen? What are the benefits of having one?

From my experience you should be fine with just the potentiometer selector, however an LCD could be extremely useful anyway. The LCD can provide feedback to whether you have actually selected autonomous which would be better than the potentiometer, and it can also do other useful things such as displaying battery voltage or other debugging info. So if you have an LCD it is worth installing it, however if you don’t have one I would not suggest buying one just for selecting autonomous.

I can’t see the photos.

Yes, pots do sometimes give incorrect values. However, I think you would be extremely lucky to get a bad value on exactly the spot you set it at. Th bigger risk would be that the pot is unplugged, which returns a value of around 250. So make sure that if you have a value below, let’s say 300, you don’t do anything.

Having an LCD (if you own one) would be a good idea, and even if you don’t use it to select it can display the choice so you can make sure you set it right.

If you have an LCD, I would use it.

Personally, I use a potentiometer to select autonomous and have it display whatever is selected on the LCD. That way you can set it back in the pits (Before the match), but still see what’s going to be called.

In my own opinion, i wouldn’t use either system alone. A potentiometer without a display runs a risk of calling the wrong program and although I’ve never used the LCD alone, I’ve seen multiple teams have major issues with it resetting itself and just general mayhem.

You don’t need an LCD but they sure are nice to have. I think you would be fine with a pot so long as your pot selections have very distinct ranges with decent gaps so that there is less chance of the wrong thing getting selected even if the pot gets nudged off a little or the pot drifts a little because of temperature or humidity.

For example, you would never want your selection values to look like this:
Autonomous 1 Pot value range 500 to 600
Autonomous 2 Pot value range 600 to 700

Instead, you might have the ranges set something like this:
Autonomous 1 Pot value range 500 to 600
Autonomous 2 Pot value range 1200 to 1400

in which your pot selector switch would be physically centered at pot values of 550, 1300, respectively. That way if your pot gets knocked somewhat out of center, your code can tolerate a little error, or if something has gone horribly out of whack, then the code can detect that, too, and sound an alarm with your speaker or light an LED.

EDIT: I should add that you probably want your pot pointer to have some sort of mechanical stop (detente) so it can’t be easily knocked from one position to another.

We’ve used an LCD for a lot of tournaments and we’ve never had troubles with it, as far as I know. I have written little snippets of code for it so my kids can use it for debugging and for programming their autonomous. For example, last year we used it to read the values of the encoders, so the kids could push their robot around the field and get some numbers on their LCD so they could then insert those values into their autonomous program. I think it helped save some time with writing an autonomous. If nothing else, it was very instructional to see the values on a display so the kids could make a mental connection between how they moved the robot and what sort of numbers the sensors generated.

Having an LCD makes a great excuse for teaching them about multi-tasking, too: you write a task just to display sensor values on the LCD and the rest of their code can run as normal without being interrupted by the LCD. The buttons allow them to cycle through a large number of sensor values, if need be.

A speaker can provide feedback just like an LCD.

It then can be used for other things throughout the match as well as debugging.
Speakers are cheaper and you don’t have to look at a small screen to get info.

Lcd’s are definitely nice, for a variety of reasons already listed. And tabor makes a good point about the speaker for feedback, except sometimes, at competitions it’s too loud to hear a speaker. One solution I had with the potentiometer selector back in Gateway was to use 3 Vex led’s and as the potentiometer is at different thresholds, it would display a binary 0-7, so I would know what autonomous is selected. The nice thing about that, is you are getting live feedback, so you would know if the pot isn’t plugged in or reading properly. However I highly recommend an LCD if you have one.

Since I’m not clever enough to figure out the picture issue, here is a link to our Google+ post which features our selector switch:

My team has the idea to now use LEDs to be our double check measure for the correctly selected autonomous. We plan on using 3 LEDs with different light combinations to represent different selections. We already has a a cheat sheet for what each autonomous does and the color coding. WE plan on just adding the LED pattern to the cheat sheet for ease of use.

(All of our autonomous programs do different things and all but one involve a human player turning the robot in the colored square. {That’s legal, correct? Or is it just for skills?} Knowing what the robot is going to do is very important for us.)

This year I think you are not allowed to interact in any way with your robot during the normal autonomous period.

Only in Programming Skills are there opportunities to interact, I think.