dreamproject
New Member
Hi all,
. Just recieved my encoder from US Digital . But I guess i got pretty excited when ordering and screwed up . My encoder i just recieved is specified to have 2500 cycles per rev.
now my calculation yeilds.
. 2500 x 4 = 10000 pulses per rev
at 1000 rpm , i get 10000 x 1000 = 10000000 pulses / min
dividing that by 60 , i get 166666.66 pulses /sec
. or a pulse freq of 166.6 KHz.
The motion control IC LM629 requires the the encoder pulses remain at the input pins for a minimum of 8 clock periods.
running the IC at 6 Mhz , the max input frequency of the encoder pulses is 750 Khz.
I know , i'm safe here . But here's the catch. The 629's architecture is designed to give a 4x increase in position resoultion .
ref : page 2 (sec 2.2) of User Guide .
So ,
. Max rpm = L
. 2500 x 4 x 4 x L
------------------- = 750000 (750 Khz.)
. 60
. 750000 x 60
. L= -------------
. 40000
. yields , L = 1125 rpm
am i safe here ? (is the 750 Khz. capture rate irrespective of the 4x resolution increase). But then , in page 3 of the user guide , it is said that with a 1 Mhz. capture rate (8 Mhz. clock) , a 500 ppr encoder , the max motor speed can be 30000 rpm.
. 1 x 10e6 x 60
. L= ------------------- = 30000 rpm.
. 500 x 4
guess the reslution increase does apply.
Since this output would drive a steering column with 1:3 reduction . A speed of 900 rpm would produce 300 rpm on the steering shaft . This corresponds to 5 rev / sec. Assuming full lock-to- lock of 4 turns , means my steering would turn from full left to right in 1 sec or less .
Am I correct ?
Would i also get a positional accuracy of 360 / 40000 = 0.009 degrees ?
Is this realistically possible ? or are all my assumptions wrong ?. Can the resolution of the encoder be decreased with external circuitry , eg flip flops .
or am i on the right track needlessly worrying ?
Thanks for ur time n patience
. Just recieved my encoder from US Digital . But I guess i got pretty excited when ordering and screwed up . My encoder i just recieved is specified to have 2500 cycles per rev.
now my calculation yeilds.
. 2500 x 4 = 10000 pulses per rev
at 1000 rpm , i get 10000 x 1000 = 10000000 pulses / min
dividing that by 60 , i get 166666.66 pulses /sec
. or a pulse freq of 166.6 KHz.
The motion control IC LM629 requires the the encoder pulses remain at the input pins for a minimum of 8 clock periods.
running the IC at 6 Mhz , the max input frequency of the encoder pulses is 750 Khz.
I know , i'm safe here . But here's the catch. The 629's architecture is designed to give a 4x increase in position resoultion .
ref : page 2 (sec 2.2) of User Guide .
So ,
. Max rpm = L
. 2500 x 4 x 4 x L
------------------- = 750000 (750 Khz.)
. 60
. 750000 x 60
. L= -------------
. 40000
. yields , L = 1125 rpm
am i safe here ? (is the 750 Khz. capture rate irrespective of the 4x resolution increase). But then , in page 3 of the user guide , it is said that with a 1 Mhz. capture rate (8 Mhz. clock) , a 500 ppr encoder , the max motor speed can be 30000 rpm.
. 1 x 10e6 x 60
. L= ------------------- = 30000 rpm.
. 500 x 4
guess the reslution increase does apply.
Since this output would drive a steering column with 1:3 reduction . A speed of 900 rpm would produce 300 rpm on the steering shaft . This corresponds to 5 rev / sec. Assuming full lock-to- lock of 4 turns , means my steering would turn from full left to right in 1 sec or less .
Am I correct ?
Would i also get a positional accuracy of 360 / 40000 = 0.009 degrees ?
Is this realistically possible ? or are all my assumptions wrong ?. Can the resolution of the encoder be decreased with external circuitry , eg flip flops .
or am i on the right track needlessly worrying ?
Thanks for ur time n patience