avsolute encoder

hiiii,
I am new with multiturn absolute encoder. I am using absolute homing method to home the motor.If the the power is cycled (off to on) to the drive, then what will be the position of the motor?Does it will be at its current position or will move to the home position automatically?I can't try it at my office as the set up is at my customer site. So please help...
thanks,
mahesh

welcome to the site
there are many posts on this site re-Absolute encoders - please also look at those.
the term Absolute - refers to usually Gray Code - so the actual value of the encoder will be known even if the power is cycled down and the unit is moved.
However, the main 'Homing' problem could occur around the Zero point because the next value below zero would be the maximum encoder value say 6000 or similar - you need to ensure that returning to home is not going to harm your setup if this happens

iant said:

welcome to the site
there are many posts on this site re-Absolute encoders - please also look at those.
the term Absolute - refers to usually Gray Code

Click to expand...

This depends on the interface. SSI absolute encoders don't need Gray code.

However, the main 'Homing' problem could occur around the Zero point because the next value below zero would be the maximum encoder value say 6000 or similar

Click to expand...

There shouldn't be a need for homing. If the controller can only handle unsigned numbers the range of numbers the encode can return should be limited to unsigned numbers. If the controller can only handle signed numbers then the returned numbers should be only positive signed numbers. If the numbers may be negative then a software trick must be used.

If the encoder is a 12 bit encoder you can wire up the 12 bits to the upper 12 bits of a 16 bit input and tie the lower 4 bits low or mask them off. The next trick is to read the 12 bits and shift right four bits and then do a signed shift right 4 bits.

Absolute encoders usually have a range of 0 to (2^n)-1 so rolling over to 6000 counts is unlikely.






- you need to ensure that returning to home is not going to harm your setup if this happens[/QUOTE]

hey Peter
:nodi:dont give me a hard time I was too lazy to correctly show the calcs.
sorry:beerchug: