V5 legal pneumatic pressure sensor

This year in VRC, my team relied heavily on pneumatics for shooting and especially endgame. Our current endgame uses 3 pistons to release and all of them require at least 50 psi to fire. As we have other systems on board that use pressure, we had to carefully regulate our pressure use during matches to make sure endgame would work. I tried to find an easy solution by simply getting a pressure gauge from the store for our bot, but learned that they weren’t competition legal. So, I designed my own. It’s a super compact and accurate design using a back tensioned piston connected to a gear on a potentiometer. Feel free to use this design for worlds or future competition years!


Wow this is genius!
20 char


The design is cool, but I just cant think of a good use case for this. If you have a well sealed pneumatic system (which you should in a competition robot), its not that difficult to count how many actuations you can do before another function doesnt work, and if I function doesnt work without lots of psi, its probably not a very well designed function/mechanism.

1 Like

Schrodinger’s pressure gauge… to check the pressure, you affect it.


How would checking the air pressure affect the pressure? It’s passively measuring how much force the air is exerting by comparing it to the strength of rubberbands. If anything it increases your air capacity due to the extra volume of the cylinder.

  1. it’s a joke
  2. in reality… extra tubing, connectors, seals, etc… chances for leaks.

only technically, but since anything that stores pressure not in a tank is illegal, you have to be careful to prove a function


our other great use for it is to make sure we have enough pressure between matches without having to connect, lose pressure, and have to recompress to top it back up. You have a point that on most bots, it’s not 100% necessary, but we’ve found it extremely useful as just a quality-of-life feature.


While cool, this design is unnecessary-

  • You should fill it up to full every match
  • It shouldn’t leak
  • The design is unnecessary weight, it also uses a pneumatic cylinder
  • Basically pointless to add on
1 Like

Instant feedback that the pneumatic pressure is good? Genius.

Plus judges would eat this up. I find this an extremely creative use of the parts available.

Great job!


Surely just spending an hour or two testing different mechanisms and how much that reduces the pressure as well as the idle pressure loss.

I agree that the judges will like this, but the weight, materials, and space takes up just isn’t worth it. A well designed mechanism that use pneumatics shouldn’t need lots of pressure to function. Practice matches will give you feedback on how many times you can use a mechanism. The idea is nice, but overall mostly unnecessary. I think it could me more useful in applications outside of competition, perhaps in work cell. I also think the reason vex hasn’t made an official pressure gauge is because it wouldn’t be useful to very many teams.


As a ref who has watched many sad faces when their shooter didn’t shoot because in the hectic chaos that is rushing match to match filling the tank was overlooked, I’d respectfully disagree. Or Billy thought Johnny filled the tank while Johny thought Billy did it. A few ounces of weight would be well worth it if an easily checked feedback device prevented a bracket elimination.

You can also consider the data collection aspect of it. It’s now possible to track air usage during matches. Trend that data over time and maybe you can start to catch worn seals, leaks starting to develop or maybe even driver performance metrics.


Or even use code to, for example, switch off certain systems, such as a PTO, to save air for other more crucial functions, like pneumatics, if the air gets low.


*like expansion systems, if the air gets low
my bad, typo

In everyone’s rush to win matches, we sometimes forget that learning is the real goal here. And a homemade gauge falls squarely into that category.

This opens up a ‘what if’ opportunity for sure.


Love this idea. While some may not see the need for it, it is definitely a nicely creative feature that provides more information about the bot. I showed this to one of my students and we have a few thoughts…

  • How consistent was it… Was it affected by the bands deforming over time?
  • Did you use a simple linear transform to convert the rotation sensor output to pressure or did you account for the fact that the piston end moves through an arc?
  • any consideration to using rack and pinion gears attached to a newer rotation sensor - maybe more compact and a linear relation between piston extension and sensor readings.

He has already thrown together a quick prototype based off of this (see animated gif) and will code it the next time we meet.
Linear Pressure Gauge

Thanks for sharing… you definitely sparked his imagination.


I loved this thing cause Anxeity on top !!!

Perhaps the most interesting aspect of this homemade pressure gauge is that many commercial pressure gauges actually function in much the same manner (force from the working fluid works against a spring).

This is a fantastic example of a clever engineering solution to a problem.

Well done!


If you look at a commercial gauge… it’s got a metal tube.

What about taking vex tubing, sanding down one side to make it weaker, then applying air? Maybe it will curve… making a pressure gauge.