How does it work 12 steps rotary encoder COM-09117

[shemo]

https://www.sparkfun.com/products/9117

1)If I turn the knob, then the wave form would be output on Pin A and B? but where does the power come from?

2)12 steps mean 12 sectors in one full revolution?

3)old A ,old B, A, B 4 bit word would give 16 values right?

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why there's corresponding table with value of 0, -1 and 1 only?

 

[chuckey]

1) pin C
2) you have a 2 bit pattern(4 states) each repeated three times in one revolution
3) not 4 bit.
Your picture (table .prg) where does this fit in?
Frank

 

[shemo]

1) pin C
2) you have a 2 bit pattern(4 states) each repeated three times in one revolution
3) not 4 bit.
Your picture (table .prg) where does this fit in?
Frank

1)Pin C is common pin tied to Ground. That's not power.
2)4 states. can this identity 12 sectored wheel? but I guess it also depend the A and B previous states right?

 

[FvM]

1. The encoder uses mechanical switches and doesn't need a power supply. It's your decision if you connect pin C to ground or a high level.
2. It's an incremental decoder, the output code is periodical with 120 degree. "12 steps" just says that 12 incremental steps make a full revolution, not that 12 positions can be identified.

 

[D.A.(Tony)Stewart]

The contact switches are grey codes in which only one contact will bounce at a time with 4 phases per 2 bit sector and 12 sectors per rev. each the same outputs separated by mechanical detent.

"If" you had another switch to indicate only 1 sector, you could have a 3 bit encoder and with a counter could decode 48 positions per revolution and a state machine for direction of motion and XOR 1 shot to compute velocity.

But normally these are just used for relative motion, direction and speed, not absolute position.