short edges detection

[PortmannJ]

hello,

i have LabVIEW 8.2 FPGA and i need to detect edges coming from a Hall effect probe build on a motor. i need it to initialize a counter when a rising edge appeer on the Hall effect probe to know how many states per turn my motor has. the time isnt constant between 2 rising edges, because the motor can rotate with several speeds. i tried it with the bloc boolean crossing, but its not good. i also tried to put a delay between to mesures of my probe, and then compare the two values to know if there is an edge, but sometimes this method doesnt detect anything...

the time of the edge is 24ns and i must do the same thing (another application) with an edgetime of 4us.

best regards

Portmann J.

[Christian Mergl]

Hi PortmannJ,

Which hardware are you using for this detection? You said the time of the edge is 24ns, so from low to high state? What is the maximum number of revolutions per minute (or second) the motor can run?

Can you please figure out a little bit more specific.

[PortmannJ]

i enter in a PCI interface with the hall effect probe signal (0-5V : digital input). the motor can run at max 12000 revolution / min, but the duration of the edges is not depending of the speed. the low to high edge is during 4us and the high to low edge is during 24ns. now i tried to filter the signal and i received good results.

thank you for your help

best regards

Portmann J.