Originally Posted by tr6scott (Post 1601908)

Did you wire your cimcoders to the srx? If you did, did you solder in the pull up resistors? If not that is probably the issue with missing counts. We ran them on Minicims for our shooter wheels, to srx running speed control loop on the srx, and worked beautifully.

From Omar, at CTR when I asked question about cimcoder and pullups.

Originally Posted by ollien (Post 1601946)

Do other encoders generally need pull up resistors?

Originally Posted by tr6scott (Post 1602126)

It's less about the encoders, as to what is reading the encoders. The roborio has pullup resistors built in. In the cRio days the digital side card had pullup resistors built in too. Read an input on either with nothing wired up, the all will return TRUE, or that the signal is high.

Originally Posted by pwnageNick (Post 1601863)

Any reason you guys didn't bring that polycarb bracket across to mount the tube on the other side of the pulley? I know it's just an encoder but it would drastically lower any worry about that encoder moving too much for basically no extra weight.

Originally Posted by Oblarg (Post 1602166)

We used to use thick surgical tubing for the coupling, but found that this actually causes a fair amount of noise in the encoder reading (my best guess is that the torsional flex in such a coupling leads to something like a stick-slip behavior, but I have no way of actually testing this). We now use helical beam couplers instead.

Originally Posted by tr6scott (Post 1602209)

We found the same on our elevator in 2015, switched to 1000psi 1/4" fuel line and the problem was resolved. (available in all auto stores for a couple bucks a foot, max.)

Originally Posted by thinker&planner (Post 1602216)

I discovered this summer that adhesive-lined heat shrink tubing works well too. It is designed to be used for underwater applications, but works well for attaching encoders too. It's easy to install, but a little more difficult to remove (you can just cut it off).

The McMaster part number is 7861K44, but don't buy the 4' length unless you want it to be shipped in a 4' long cardboard tube (not coiled up in a bag).

Originally Posted by Oblarg (Post 1602166)

We used to use thick surgical tubing for the coupling, but found that this actually causes a fair amount of noise in the encoder reading (my best guess is that the torsional flex in such a coupling leads to something like a stick-slip behavior, but I have no way of actually testing this). We now use helical beam couplers instead.

Originally Posted by MichaelBick (Post 1602269)

If your encoder mount has some free play or reasonably tight tolerances, I also really like slotting the given shaft and then clamping down with a hex or round shaft collar.

Originally Posted by Oblarg (Post 1602283)

It'd also be a good opportunity to get the students to practice drilling into the end of a shaft accurately with our hobby lathe, which is something we seldom do (c.f. turning down a shaft).

Originally Posted by MichaelBick (Post 1602420)

I really like thunderhex for this, just because it has the pre-bored hole. This keeps the drill relatively concentric to the axle and helps with chip clearing (the two biggest issues you have to face with small diameter drills).

Originally Posted by AlexanderLuke (Post 1601867)

In the past with our fully custom WCD systems, Team 696 has placed encoders on the drive shafts of wheels other than the output shaft of the gearbox. It was perfectly reliable for us, with no slippage of the encoders or wandering of the encoders out of the shafts during practice, competition matches, or offseason events. I do not personally see any reason for us to change this practice in the future for such a setup.

We have often relied on US Digital S4 encoders for drivetrains and other systems, which are now replaced with the S4t as far as I understand. We have not had any experience with the S4t.

One tip for encoders in shafts though: feel free to use some hot glue to aid in the interface between the encoder shaft and the shaft it is connected to. This will certainly help in keeping that encoder from slipping inside the shaft, or the encoder from becoming removed from the shaft unintentionally.

Originally Posted by gc_coxen (Post 1602434)

Did your team experience any backlash with mounting to the drive axle? One of my teams mentors is worried that we will experience backlash if using PID on the drivetrain if mounting to the axles.

Originally Posted by AdamHeard (Post 1602436)

The drive axle is closer in gearing to the floor than somewhere near the motor, it will have a much more accurate measurement of floor position.