Magnetic Encoder Advice

[Jogo]

We have been relying on the kit magnetic (rotary) encoder to measure the position of an arm, with decent success. However, at one point today, our encoder just stopped giving us good data (0 for position, 0 for magnetic field strength.) We are using it in SPI mode. We've ensured all proper wiring--and it's definitely giving a signal--when it doesn't, it reads 255, not 0.

Anyone else face similar problems/have suggestions?

[Gdeaver]

The KOP magnetic encoder is ok as a demo board. For our robot we prefer a more rugged device. This year we are using Vishay 981He and last year Cherry AN8. Both are automotive qualified. They have some electrostatic protection and are sealed. They are both analog. Couldn't find a spi or i2c device I liked that was with in our budget.

[Alan Anderson]

My advice: replace the encoder board. If other teams at your event followed suggestions, at least a couple of them will have unused Kit of Parts components to share.

[Ether]

Originally Posted by Gdeaver

This year we are using Vishay 981He

Do you know if the 360-degree continuous-rotation model has essentially no "dead zone" when transitioning from 360 to zero? It's not clear from the datasheet.

[Travis Hoffman]

Originally Posted by Ether

Do you know if the 360-degree continuous-rotation model has essentially no "dead zone" when transitioning from 360 to zero? It's not clear from the datasheet.

Unicorn drive?

I love the Cherry AN8 1640 used last year - 48/3193 are using it on our arms this year, with much success.

Mouser sells these for $45:

http://www.mouser.com/ProductDetail/...qh3niR4xw% 3d

Data Sheet:

http://www.cherrycorp.com/english/se...AN8_Series.pdf

Also have to buy some Delphi automotive connectors and terminals, both of which Mouser sells and are in stock.

[Ether]

Originally Posted by Travis Hoffman

Unicorn drive?

Yeah :-)

I love the Cherry AN8 1640 used last year - 48/3193 are using it on our arms this year, with much success.

Mouser sells these for $45:

http://www.mouser.com/ProductDetail/...qh3niR4xw% 3d

Data Sheet:

http://www.cherrycorp.com/english/se...AN8_Series.pdf

The graph in the lower-left corner of the second page of the datasheet seems to strongly imply no dead zone - it shows a sharp saw-tooth transition from max back to min. Has that been your experience?

I was specifically inquiring about the Vishay 981HE.

[Gdeaver]

They have no dead band. How ever they are dependent on the supply voltage. if they are given 5 volts they will give an analog voltage from 0 deg - .5 volts and 360 deg 4.5. If the supply voltage was 4.95 then it would be .495 to 4.45.
This isn't a problem with the analog break outs this year but was noticeable last year. We did manage to eat a Vishay this year from a mechanical failure. They work great as long as we don't smash them. The Cherry AN8 served us well last year too. Ideal for pivot drive and arm sensing.