Rotary encoders vs. price

Technical Technical Discussion
1

I’m having trouble reconciling what differentiates popular FRC rotary encoders, especially since their price varies so much. For example, based on DigiKey:

  • AS5145B Quadrature Magnetic Encoder; $38; 0.0879deg resolution
  • Grayhill 63R Quadrature Optical Encoder; $54-$75; 64PPR encoder more expensive than 256PPR encoder?
  • TT 6120 Hall Effect (Absolute?) Encoder; $15; 0.088deg resolution
  • CUI AMT203-V Absolute Encoder; $49; 0.2deg resolution

I know max RPM and mechanical life varies between each encoder, but what else accounts for each sensor’s price difference/popularity?

2

Another good option is CUI’s AMT-102V. It’s $24, has up to 2048 counts per revolution and is easy to mount. We used them extensively in the 2015 season and expect to continue in 2016.

3

The Grayhill encoders have internal bearings, which increases the cost.

4

Grayhills are also sealed and require no assembly (read: stupid-proof). This is why we use them.

5

Re stupid-proof - no such thing; rather say “stupid resistant” :slight_smile:

6

AS5145B - low RPM, magnet must be positioned very precisely

TT 6120 – haven’t looked at this before – isn’t it a position sensor, not an encoder?

7

Some more options…

CTRE Magnetic Encoder (absolute within one rotation and relative - we make this one)
These are unique in that it uses the same cabling as Talon SRX, so they plug right into the Talon.
http://www.ctr-electronics.com/srx-magnetic-encoder.html

If you are using Versa, there is a slice with same CTRE sensor built in.

Another analog encoder (MA3 US digital) I’ve used and seen teams use (absolute within one rotation)


Another popular quadrature encoder(relative - us digital) I’ve used and seen teams use.

8

Alot of the popularity comes from how easy they are to mount. For example the greyhills yoy can easily zip tie down the wire and attach to a shaft via surgical tubing (so I hear). To some teams that justify the price. I perfer the CUI ATM-102V encoders because of the price, that said they are a pain to mount, but for my team that is a sacrifice we are willing to make.

9

Also the US Digital S4T, which is essentially the shafted version of the E4P.