Encoder - Would it help Shooting Power Cells in Infinite Recharge?

Really, a second year team. We are using two 775Pro motors to spin a set of 4-inch compliance wheels on a 1/2-inch hex axle. They are at 100% RPM. What does an encoder do? Would it help? The Power Cells aren’t going high enough. About 7.5 feet. Even if it’s too late, I would like to get this to work.

Can we see your shooter design? Also, if you have wheels that aren’t compliant wheels between 4-in to 6in that would help. How much compression do you have? (how much smaller is the ball in the shooter vs normally).

What does an encoder do?
An encoder is a sensing device that provides feedback. Encoders convert motion to an electrical signal that can be read by some type of control device in our case the RoboRIO. In the case of a shooter, an encoder on the shooter shaft would be allow you to get the speed of that shaft accurately and some more information.

There is not much an encoder will do for you in terms of your efficacy (at this point at least), issues like this have to do with shooter design most of the time.

For a more technical encoder explanation, see here Encoders - Hardware — FIRST Robotics Competition documentation


If you are already at 100%, an encoder is not going to help you. But, once you get a shooter that has enough range/power that you are not running at 100%, then an encoder would allow you to control/regulate the speed of the shooter to achieve different target ranges.

So, as you improve your shooter design, you may want to have a plan for how you would add an encoder so that once you have it shooting well, you can control it.


We have a similar setup and are able to shoot with plenty of velocity. We have geared the 775 pros via a belt at 2:1 driving 4" wheels. We are using a Rev through bore encoder and although the motors are running at a higher percentage than ideal we are definitely able to PID the velocity to improve consistency.

How much compression are you putting on your Power Cells? We’ve found the best results when the PCs are squished to 5.5".

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an encoder would defiantly help. out team uses a Through Bore Encoder to read and regulate the speed of our motors.

Other people have explained encoders, we used Neo motors for our shooter. The built in encoders are a great benefit. I suspect a more rigid wheel will make a big difference for you. How wide is your wheel? Can you add more wheel? If you only have one wheel and there is some space for the ball to move sideways you can end up with very different results. Two strategies - start with modifying the angle, simply stick some boards under the front and use A protractor to determine the angle. We marked a grid on our target and recorded where the ball landed at different distances - are you getting consistent results? Does the angle help?
Strategy 2 is film the shooting sequence in slow motion multiple times. If you can get an angle that shows the ball coming out you can see how things are compressing. Changing your compression and the type of wheel can have a huge impact.
Good luck!

We used 4:1 gearbox on the 775Pro driving the axel. Would a 2:1 increase velocity/shooting height?

Earlier you had mentioned using two 775 motors. We’re having pretty good results with them hooked up through this.

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This thread had some really good information: Idiots Guide to Making Good Shooters

Also, +1 @Taylor for 5.5 inches of compression.

Does any have a JVN calculator handy? I have to run so I don’t have time to find the link, but I think it would be beneficial for OP.

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