Encoders for 2015 Season

[stufflikethat]

Hi guys. I have been looking for encoders for the new season and we typically use these from andy mark, but I was trying to find a cheaper and better overall option.

I know that some teams are experimenting with these new ones, but I was trying to see how people feel about them and then where to get them if they are nice.

[techhelpbb]

Had nothing but trouble with the US Digital encoders like the one you linked.
Years of trouble.

Many teams swear by them we simply can't have any more surprises.

DigiKey sells may fine encoders that are slightly more expensive.
If, like me, the time you waste playing with the encoders in the end is way more valuable than the encoder I would go shopping at the higher price.

One hour of my time more than buys all the encoders we are likely to need from a company like GrayHill.
Further it reduces this when someone suggests using an encoder.

[billbo911]

Originally Posted by techhelpbb

Had nothing but trouble with the US Digital encoders like the one you linked.
Years of trouble.

Many teams swear by them we simply can't have any more surprises.

DigiKey sells may fine encoders that are slightly more expensive.
If, like me, the time you waste playing with the encoders in the end is way more valuable than the encoder I would go shopping at the higher price.

One hour of my time more than buys all the encoders we are likely to need from a company like GrayHill.
Further it reduces this when someone suggests using an encoder.

Our experience with the US Digital encoders is mixed. They work very reliably when handled and installed properly. But, as hard as we try, working with High School students, that is not always possible. Disk get dirty, smudged, and misaligned. Shaft run-out and end-play will destroy the little US Digital encoders in a heartbeat.

Don't misunderstand me, US Digital makes some fantastic encoders. It's the ones linked to by the OP that can be a bit suspect.

A sealed encoder that is mechanically isolated from motions that can damage it are your best bet.

[Ivan Helmrich]

We have never used the ones linked in the OP, but I did mount a couple for a preseason project and didn't like them at all. Too many things to go wrong. I like these:
http://www.usdigital.com/products/en...otary/shaft/S4

We get the ball bearing version and have never had a failure. Some have been around for a number of years. I don't like the tiny wires and connectors, those do fail and need to be replaced. They're easy to mount and we just hook to the shaft with snug fitting surgical tubing. They are pricey, but as mentioned above, I get that back in time not messing with them and we use them over and over.

We will also test the ones we got with FIRSTChoice. I prefer encoders with a shaft, but the price is better and they look like a good compromise.

Ivan

[SteveGarward]

We use the E4P every year, on our drive at least. In 2012 and 2013 we have also used them on our flywheels for shooting as well, with a lower CPR encoder disc. In 2012, we did have some issues with bad readings, but it was because of scratched old encoder discs rather than the encoder itself. (Hooking up a logic analyzer showed what was going on the signal when code wasn't behaving as expected.)

Most other issues we have during testing is usually due to an old encoder unit that has more than done its time. Whenever we use new, well handled units we seem to have no trouble. Having said that, everyone is also taught how to handle them and is careful with them.

US Digital has discontinued the E4P though (last year), and has just recently released the E4T as a replacement, so they will be interesting to try out.

[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 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.

[ozrien]

Originally Posted by 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.

Breakouts are available at andymark and vex. Search for analog breakout for 5v analog signals.

Why greycode ? CANBus has strong error detection.

[marshall]

Originally Posted by ozrien

Breakouts are available at andymark and vex. Search for analog breakout for 5v analog signals.

Why greycode ? CANBus has strong error detection.

Mainly because we could then get 3.3v absolute encoders. It's hard to find those things other than 5v. Most of the ones I saw that supported 3.3v were using gray code as output instead of analog. I just want to be able to interface the encoder without peripheral circuitry.

EDIT:

Links to the CTRE breakouts from Vex. I could not find them at AndyMark:

http://www.vexrobotics.com/217-4398.html
http://www.vexrobotics.com/217-4401.html

[mman1506]

I can't stand the tiny little connectors on us digital encoders, they always broke on us. I much prefer the solder terminals on other encoders like greyhills.

[Jared]

The E4P (us digital) encoders are okay if installed properly. The S4 series with ball bearings are far superior.

My favorite encoders are the greyhill ones. They're more expensive and a tiny bit larger, but they are quite strong. You should have no problem putting a sprocket/pulley on the end of the shaft. You'll gain a lot of reliability and a much larger margin of error for relatively insignificant losses.