Gene Heskett wrote: > On Sunday 15 July 2012 23:29:40 Jon Elson did opine: > >> >> Now, I'm not too clear on the +/- 3 fluctuation in terms of REVOLUTIONS >> rather >> than COUNTS, which you seem to be saying above. >> > > That is exactly what I am saying Jon, using the hal encoder module. > > >> I completely expect >> jumps of +/- 2 counts/sample, but that should be divided by the number >> of encoder counts/rev. If the measured speed is jumping by +/- 3 RPS, >> > > It is. > > >> something seems to be really wrong. >> Well, something IS really wrong. Detective work is needed. Have you run the latency tests, with something like glxgears running, to simulate the axis 3-D preview load on the graphics system?
I gather now you are using the hal encoder component. You need to be sure that the update-counters function is called from the base thread, and that the hal_parport is also called from the base thread. If these are being called from the servo thread, it will introduce higher latency and cause it to miss counts. What is the base thread set to? What is the encoder resolution and the top speed you intend to achieve? You have mentioned 20 RPS = 1200 RPM. For it to work, you need to be sure that the base thread is running fast enough that it samples more than once per count from the encoder. So, for 20 RPS x 400 counts/rev (100 tooth encoder wheel) that is 8000 counts/second. Your base thread should be twice that rate, so 16000 samples/second, or BASE_PERIOD=62500 > I have not been able to see/find a signal with > halscope that zeros itself on the index pulse. > This only occurs when an axis is synched to the spindle, at the beginning of a threading operation such as G33 or G33.1 OK, so you've checked the sensors themselves, but maybe there is something interfering wit the computer reading the sensor signal. Since you are using the hal encoder component, the A and B quadrature signals are available to Halscope. Maybe there will be some disturbance there. It really HAS to be on these signals, the encoder component works as designed, and hasn't needed any adjustments in the counting section since 2009. Jon ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
