View Full Version : Encoders for 2015 Season
stufflikethat
11-12-2014, 21:54
Hi guys. I have been looking for encoders for the new season and we typically use these from andy mark (http://www.andymark.com/product-p/am-0180.htm), but I was trying to find a cheaper and better overall option.
I know that some teams are experimenting with these (http://www.chiefdelphi.com/forums/showthread.php?t=131030&highlight=encoder) new ones, but I was trying to see how people feel about them and then where to get them if they are nice.
techhelpbb
11-12-2014, 22:41
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 :ahh: when someone suggests using an encoder.
billbo911
12-12-2014, 12:18
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 :ahh: 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 (http://www.usdigital.com/products/encoders) 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
12-12-2014, 12:50
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/encoders/incremental/rotary/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
12-12-2014, 12:56
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.
12-12-2014, 15:25
From our experience with the CUI encoders (http://www.cui.com/product/resource/amt10-v.pdf), 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.
mman1506
12-12-2014, 16:20
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.
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.
hzheng_449
12-12-2014, 17:20
We use the US digital H6 encoder (http://www.usdigital.com/products/encoders/incremental/rotary/shaft/H6)
The extra cost vs the E4P is definitely worth is as the H6 is more reliable and easier to use than the E4P.
Ben Wolsieffer
12-12-2014, 19:08
What are the mounting options for the CUI AMT-10 encoders (like the ones mentioned above and included in FIRST Choice)? Has anyone tried using them with Andymark or VexPro gearboxes (specifically Touchbox Mini or 3-CIM ball shifter)?
I know I could do more research into the technical documents, but I'd like to hear people's experiences too.
AdamHeard
12-12-2014, 19:10
We use the US digital H6 encoder (http://www.usdigital.com/products/encoders/incremental/rotary/shaft/H6)
The extra cost vs the E4P is definitely worth is as the H6 is more reliable and easier to use than the E4P.
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!
Twins Inc.
13-12-2014, 02:41
I know I could do more research into the technical documents, but I'd like to hear people's experiences too.
I think that might be the best option right now, researching the spec sheets. I haven't seen the CUI encoders before this year, and I haven't really seen teams use them on those gearboxes yet. But hey, Prove me wrong! I'll get back here and let you all know what I find if I do eventually research this myself.
Joey Milia
13-12-2014, 03:27
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.
My favorite encoders are the greyhill ones. They're more expensive and a tiny bit larger, but they are quite strong.
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!
Which grayhill model do you use and where do you source them?
mman1506
13-12-2014, 08:13
Which grayhill model do you use and where do you source them?
The grayhill 61K, 61E, 63R are the series commonly used in frc. They can be purchased from digikey.
nathannfm
13-12-2014, 10:13
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.
AdamHeard
13-12-2014, 10:56
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
13-12-2014, 14:28
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
14-12-2014, 11:47
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.
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
14-12-2014, 12:38
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/-fNO2i5t5DAA/UvnRW5T1jWI/AAAAAAAARe8/wuHWjmMzshY/s1280/CAD%2520%252841%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.
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
14-12-2014, 13:30
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.
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
14-12-2014, 14:22
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/-fNO2i5t5DAA/UvnRW5T1jWI/AAAAAAAARe8/wuHWjmMzshY/s1280/CAD%2520%252841%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
14-12-2014, 22:27
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
05-01-2015, 22:51
From our experience with the CUI encoders (http://www.cui.com/product/resource/amt10-v.pdf), 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*
What specific Grayhill encoder is best to purchace from Digi-Key for a drive using a Talon SRX?
wmarshall11
13-01-2015, 00:31
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
13-01-2015, 01:10
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
13-01-2015, 08:11
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 (http://en.wikipedia.org/wiki/Gray_code#Position_encoders) 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.
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 (http://en.wikipedia.org/wiki/Gray_code#Position_encoders) 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.
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.
We use Grayhill Encoder 63R128 (http://www.digikey.com/product-detail/en/63R128/GH3069-ND/304478) They are terrific encoder, and Digi key sells them at a good price. We use 128 count encoders for our drive train, and since we have them laying around, they get used for other systems frequently as well. In order to to attach our encoder to our output shaft we use 1/4 OD and 3/16 ID surgical tubing. It sounds sketchy, but works great, it also helps absorb some slight misalignment issues that you might have. Simply slip the tubing over the .250 part of a AM output shaft and the other side slips onto the encoder. Create a bracket to hold it in place and you are good to go.
Here is an image:
https://drive.google.com/file/d/0B026cUnrs9JwSUk3S1Q4ZkU4aWc/view?usp=sharing
Hope this helps!
marshall
13-01-2015, 10:35
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
The_Drive_DR
13-01-2015, 11:43
We are using the CUI encoders (http://www.cui.com/product/components/encoders/incremental/modular/amt10-v-kit) and they work great!
with the Grayhill encoders, how do you wire them? Do you use the same connector as the AM USDigital encoders?
May seem like a dumb question but I am not an electronics guy.
Thanks
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
Yeah but 2bit grey code is the same as quadrature, unless I'm missing something.
I'm always interested in new sensors, send me a data sheet if you can.
wmarshall11
13-01-2015, 12:35
with the Grayhill encoders, how do you wire them? Do you use the same connector as the AM USDigital encoders?
May seem like a dumb question but I am not an electronics guy.
Thanks
You can get them with wires attached or with .1in pins. Getting the pins tends to be more feasible. You can either solder to them or attach standard .1 female connectors (same as pwm) and run cable back to your control board.
You can get them with wires attached or with .1in pins. Getting the pins tends to be more feasible. You can either solder to them or attach standard .1 female connectors (same as pwm) and run cable back to your control board.
With the USdigital encoders there were 4 wires, with these I see 5 pins.
What do they get wired to?
Thanks
marshall
13-01-2015, 13:14
Yeah but 2bit grey code is the same as quadrature, unless I'm missing something.
I'm always interested in new sensors, send me a data sheet if you can.
Is it?!?! I didn't know that. I will find some spec sheets and send them your way for the ones we were looking at. There is also a CAN based sensor from a BMW steering wheel that looked promising...
Alan Anderson
13-01-2015, 13:18
With the USdigital encoders there were 4 wires, with these I see 5 pins.
What do they get wired to?
The data sheet (http://lgrws01.grayhill.com/web1/images/ProductImages/Series%2063R%20Encoder.pdf) shows the pinout. Pin 4 is not connected.
Alan Anderson
13-01-2015, 13:19
Yeah but 2bit grey code is the same as quadrature, unless I'm missing something.
Marshall wants absolute sensors.
marshall
13-01-2015, 13:24
Marshall wants absolute sensors.
It's true. I also want a pony.... perhaps even a striped one with a horn on it.
It's true. I also want a pony.... perhaps even a striped one with a horn on it.
YAY PONIES!
Every time that we've used encoders for swerve drive, we've coupled them with a 360 degree potentiometer for initial calibration. This way, you (almost) always know where your wheels are pointing and how much you're slipping.
If you throw a well-calibrated Gyro into the mix then you've got field-oriented drive + drift compensation!
We've also had great results using the US Robotics encoders included in previous KOPs. One for steering, and one for drive.
That's an interesting idea.
With a custom breakout/cable you could wire out both the potentiometer and quadrature encoder for each wheel for each Talon SRX (since SRX decodes both at the same time and puts both on CAN bus).
YAY PONIES!
Every time that we've used encoders for swerve drive, we've coupled them with a 360 degree potentiometer for initial calibration. This way, you (almost) always know where your wheels are pointing and how much you're slipping.
If you throw a well-calibrated Gyro into the mix then you've got field-oriented drive + drift compensation!
We've also had great results using the US Robotics encoders included in previous KOPs. One for steering, and one for drive.
marshall
13-01-2015, 15:45
That's an interesting idea.
With a custom breakout/cable you could wire out both the potentiometer and quadrature encoder for each wheel for each Talon SRX (since SRX decodes both at the same time and puts both on CAN bus).
That's a complicated mess though. Mounting one of these widgets is bad enough. I really just want someone to start selling 3.3v absolute encoders instead of 5v ones.
We are already building a custom breakout to do the conversion... it's just extra circuitry that I'd love to get rid of.
jman4747
13-01-2015, 16:09
That's a complicated mess though. Mounting one of these widgets is bad enough. I really just want someone to start selling 3.3v absolute encoders instead of 5v ones.
We are already building a custom breakout to do the conversion... it's just extra circuitry that I'd love to get rid of.
Are the MXP/0-9 GPIO not 5V tolerant?
James Kuszmaul
13-01-2015, 16:13
Are the MXP/0-9 GPIO not 5V tolerant?
The Talon SRX analog pin isn't.
marshall
13-01-2015, 16:14
Are the MXP/0-9 GPIO not 5V tolerant?
They are but the Talon SRX is not. The goal is to offload PID control to the Talons. We just need more options for 3.3v absolute encoders that output a 3.3v analog values.
In 2013 I put together a group buy for sealed US Digital encoders. You can see all the details in this thread:
http://www.chiefdelphi.com/forums/showthread.php?t=116899
We absolutely love them.
Despite what the product page says (http://www.usdigital.com/products/encoders/incremental/rotary/shaft/s4) these are available for purchase. I just got off the phone with the sales rep I worked with on the group order, and they are available for same day shipping.
If someone wanted to put together another group buy to get the price down, we would be interested in participating. But, fair warning, during build season might not be the best time to put one of these together.
Monochron
14-01-2015, 12:41
They are but the Talon SRX is not. The goal is to offload PID control to the Talons. We just need more options for 3.3v absolute encoders that output a 3.3v analog values.
Just to put me at ease, the quadrature input pins on the Talon ARE 5V tolerant correct? It is only the analog input that needs 3.3V?
marshall
14-01-2015, 13:34
Just to put me at ease, the quadrature input pins on the Talon ARE 5V tolerant correct? It is only the analog input that needs 3.3V?
That is correct. I highly recommend the awesome datasheet for the Talons that CTRE has: http://www.crosstheroadelectronics.com/Talon%20SRX%20User's%20Guide.pdf
Monochron
14-01-2015, 13:50
That is correct. I highly recommend the awesome datasheet for the Talons that CTRE has: http://www.crosstheroadelectronics.com/Talon%20SRX%20User's%20Guide.pdf
Yeah I didn't see any specifications for what voltage was allowed on the quadrature pins. Thanks!
ayeckley
14-01-2015, 13:54
We typically use our Automation Direct voucher towards the purchase of the TRD-family ("light duty") encoders they offer. I believe they are re-branded Koyo units.
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