Encoders for 2015 Season

[AdamHeard]

Originally Posted by nathannfm

Are there any good options for measuring off the back shaft of a banebots style motor? Mainly common FRC encoders than can do 20,000 RPM and if there are any known good mounting options/tricks.

By the time you have any meaningful reduction off it the precision will be poor due to backlash for average FRC gearing. This could be acceptable for the application or a huge pain.

[nathannfm]

Originally Posted by AdamHeard

By the time you have any meaningful reduction off it the precision will be poor due to backlash for average FRC gearing. This could be acceptable for the application or a huge pain.

Right, thanks for pointing that out, so no good for 100:1 VP on a swerve drive. We tried reading a shoulder bolt sticking out of the tapped hole but the tolerance on on that hole is non existent and it wobbled all over the place. Guess we are going to have to press a pin in and turn it to round after its in the shaft.

[Qbot2640]

Originally Posted by mman1506

The grayhill 61K, 61E, 63R are the series commonly used in frc. They can be purchased from digikey.

Excuse my lack of experience - we have never used encoders, and I desperately want to this year. The Grayhill models referenced above look like potentiometers, for lack of a better description...How are they installed? Do you just couple the shaft to the gearbox shaft?

I understand how the US Digital one's install - in fact, we installed a pair on our robot this fall for the off-season, but never figured out how to wire them up or program them.

[Jared]

Originally Posted by Qbot2640

Excuse my lack of experience - we have never used encoders, and I desperately want to this year. The Grayhill models referenced above look like potentiometers, for lack of a better description...How are they installed? Do you just couple the shaft to the gearbox shaft?

I understand how the US Digital one's install - in fact, we installed a pair on our robot this fall for the off-season, but never figured out how to wire them up or program them.

They're installed just like potentiometers, but they have no restriction on how far they can turn. If you want, you can couple them to a gearbox shaft, or you could put a sprocket or pulley on the encoder shaft.

To couple the shaft of the encoder to the gearbox without having to buy/make a shaft coupler, you can actually use a short piece of surgical tubing, and stick the two shafts inside the hole in the middle of the tubing and put on a few zip ties to prevent it from sliding out.

[mman1506]

Originally Posted by Qbot2640

Excuse my lack of experience - we have never used encoders, and I desperately want to this year. The Grayhill models referenced above look like potentiometers, for lack of a better description...How are they installed? Do you just couple the shaft to the gearbox shaft?

I understand how the US Digital one's install - in fact, we installed a pair on our robot this fall for the off-season, but never figured out how to wire them up or program them.

You are correct, they interface mechanically exactly like a pot would. Here is a pic of two grayhills 971 has on their bot https://lh6.googleusercontent.com/-f...52841%2529.JPG .
What's really great about the greyhills is that the shaft is supported by a ball bearing so they are MUCH more tolerable tolerable to axial and radial load than the commonly used US digital encoders.

[Ether]

Originally Posted by mman1506

What's really great about the greyhills is that the shaft is supported by a ball bearing so they are MUCH more tolerable tolerable to axial and radial load than the commonly used US digital encoders.

Two things:

1) It's spelled "Grayhill", with an "a". (It's easier to find if spelled correctly)

2) Not all models of Grayhill encoders have ball bearings. Make sure to check the datasheet before ordering.

[mman1506]

Originally Posted by Ether

Two things:

1) It's spelled "Grayhill", with an "a". (It's easier to find if spelled correctly)

2) Not all models of Grayhill encoders have ball bearings. Make sure to check the datasheet before ordering.

All of the models I previously listed and referenced to in my post are ball bearing supported.

[Ether]

Originally Posted by mman1506

All of the models I previously listed and referenced to in my post are ball bearing supported.

I should have been clearer: The caution clarification was for other readers.

The specific post I responded to had no list and no reference.

[AdamHeard]

Originally Posted by mman1506

You are correct, they interface mechanically exactly like a pot would. Here is a pic of two grayhills 971 has on their bot https://lh6.googleusercontent.com/-f...52841%2529.JPG .
What's really great about the greyhills is that the shaft is supported by a ball bearing so they are MUCH more tolerable tolerable to axial and radial load than the commonly used US digital encoders.

Us digital does have shaft based encoders as well.

[stufflikethat]

Originally Posted by AdamHeard

I'm a big fan of US Digital, and use the super high count E6's where it makes sense... but for a shaft based option I'm not seeing the advantage of the H6 over the grayhill encoders. Much more money and size!

Hey Adam would you mind linking me to your preferred grayhill encoder.

Many thanks.

[Mecanum Wheel]

Originally Posted by Twins Inc.

From our experience with the CUI encoders, we have had only a positive experienceso for. They seem to be more reliable becuase the actual disk is enclosed and magnetic, not optical. They and mount in a very similar way to the E4P, and could be used for a variety of similar uses.

We used E4Ps for our mechanum last year. Because they were hard to reach under the robot and thus even harder to install/replace during a breakdown, we will probably use all CUI encoders for future mechanum drives. BUT. Be warned:

"*We recommend no more than three cycles of mounting and
removal of the AMT top cover base. Multiple cycles of mounting
and removing the top cover can cause base fatigue over time
and affect encoder performance."

....Its easy to exceed this recommendation if you are careful and treat the plastic tabs and axle mount nicely, but every time you do you risk damaging the disk inside and breaking the plastic mount.
How delicate is the magnetic disk anyways?

Mind, the encoders in the FIRST Choice are a little different then the ones in our picture from the OP, they are "straight radial" pins while the FC ones are "right-angle axial" ones.

mecanum*

[IndySam]

What specific Grayhill encoder is best to purchace from Digi-Key for a drive using a Talon SRX?

[wmarshall11]

Originally Posted by IndySam

What specific Grayhill encoder is best to purchace from Digi-Key for a drive using a Talon SRX?

I'm a fan of the 63R Series. Specifically, the 63R128 and 63R256 are good picks.

[Dunngeon]

Originally Posted by IndySam

What specific Grayhill encoder is best to purchace from Digi-Key for a drive using a Talon SRX?

I don't know if there is a specific encoder that works *better* with the SRX than any other. That said, as in the post above the Grayhill 63R-xxx series has been the most reliable encoder Team 955 has ever used.

[marshall]

Word of caution about absolute encoders with the Talon SRX... most of them that provide analog output seem to require 5v power instead of 3.3v power which the Talon SRX must have for analog input. DO NOT connect 5v to the Talon's analog in. It might not end well.

CTRE is releasing a converter board and we are making some custom ones. We have a student working on a write-up of how we created ours along with details.

It might be neat to see the Talon SRX controllers support gray code in the future in addition to analog output for absolute encoders but that would likely require a firmware update and some serious coding witchcraft for the Talons.