high speed tracking

[ttnn58]

hi CD!
we are thinking about the idea of a flywheel for our robot, spinning at about 2000-3000 RPM (not entirely sure about this number) and we want to see how fast he is spinning, and we tried to use this encoder:
http://www.andymark.com/MA3-A10-250-...-p/am-2899.htm
this encoder couldn't measure the speed of the wheel fast enough...
how can we measure the speed of our wheel to know how fast he is spinning?
thanks guys

[Ether]

Originally Posted by ttnn58

we tried to use this encoder:
http://www.andymark.com/MA3-A10-250-...-p/am-2899.htm

That's an absolute position encoder:

Product Overview:
This kit contains one encoder and one encoder cable. The MA3 is a miniature rotary absolute shaft encoder that reports the shaft position

Select an encoder that's designed to measure speed.

[Ether]

Originally Posted by Ether

That's an absolute position encoder:

Also, it has a sleeve bushing and the rated max speed is 100 rpm.

The datasheet is available via a link at the AndyMark page you posted. Download it and take a look. You may not understand all of it, but take a look anyway. It's a great way to start learning.

[MetaEngineer]

The best solution is an encoder meant to handle higher speeds, such as the Grayhill 63R series. It can handle up to 5000 RPM and we have found them to be reliable.

There are different resolutions available, so be aware which part number you are buying. Lower resolutions such as 63R32 and 63R64 will work for high speed flywheels such as yours. The high resolution 63R256 is better suited to drivetrain and other places where speeds are lower but you want more precise measurement at those lower speeds.


For checking the RPM of parts you have not put an encoder on, a laser tachometer is a very useful tool to have.

[MACH]

Try the MACH Engineering Touchless Encoder: https://www.chiefdelphi.com/forums/s...d.php?t=153808

It was specifically designed for applications like this. You don't need extremely high resolution, there are no bearings to worry about, and mounting is a breeze!

[sraque]

I can also recommend the CTRE magnetic encoder:

http://www.ctr-electronics.com/senso...c-encoder.html

As well as the CUI AMP 10 series of encoders:

http://www.cui.com/catalog/component...mental/modular

We have successfully speed-controlled high speed wheels with both of these encoders directly connected to a Talon SRX.

Both encoders are available from AndyMark.

[BDRessler]

Originally Posted by sraque

I can also recommend the CTRE magnetic encoder:

http://www.ctr-electronics.com/senso...c-encoder.html

As well as the CUI AMP 10 series of encoders:

http://www.cui.com/catalog/component...mental/modular

We have successfully speed-controlled high speed wheels with both of these encoders directly connected to a Talon SRX.

Both encoders are available from AndyMark.

We use the CUI AMT-103 encoders, they are super nice because they are robust and have an adjustable resolution.

[Gdeaver]

I'll 2nd the CUI AMT102 or 103. We have used them for the last 3 years and they have been rock solid. We got the AMT102 on the shooter Sunday hooked into a Talon SRX at 512 resolution. Testing done at 4100 to 4300 rpm. Using FPID looks very good but the graphs show that we need a fly wheel. CRE has done a good job. Proud of the programmers. They studied the CRE manual and got it up and running in a couple hours. This is not easy but with CUI and CRE we are getting there.

[dtengineering]

A more basic approach might be to use a reflective object sensor, such as a QRD1114 (or OPB706A, or any of a wide range of IR reflective sensors) and a bit of reflective tape on your wheel. If your wheel is already reflective, then use non-reflective tape... anything so you have part of the wheel reflective (shiny, white) and part of it non-reflective (dull, black). The non-reflective part could also consist of a hole in the wheel... anything that doesn't reflect IR light back into the sensor. You have to add a couple resistors to the QRD1114, but you'll find plenty of tutorials on how to do it.

This way you'll get one pulse per revolution... just use the RoboRio to time the interval between pulses and you're set. You can achieve the same thing by looking at the shaft... paint half of the shaft flat black, and leave the other half shiny.

Do note that the effective range of the QRD1114 is about 1mm. And that it has 1114 in it's name. If it's 1114, that means it's got to be good, right? :-)

Jason

[Ether]

Originally Posted by dtengineering

just use the RoboRio to time the interval between pulses and you're set.

Just highlighting this for emphasis. For a one-per-rev sensor, do not count pulses and divide by time.