linear incremental scale

[email protected] · Joined: 28 Jul 2014 Posts: 38

I have connected an incremental linear scale in QEI module 1 of DSPIC33EP512MU810 controller. If i move the scale i am getting pulses in increment of 1 but my qei module is 4x.

Also the Repeat-ability of the pulses for a fixed linear distance is not same. It fluctuates by 4 to 7 counts.

If i connect the same scale to DRO of the scale manufacturer i am getting exact pulses of for the fixed linear distance.

I have attached the wave form of the linear scale.

temtronic · Posted: Sat Apr 13, 2019 4:41 am

You need to post the mfr/make/model of the scale or a link to it's datasheet. The scope view doesn't look like any encoder I've ever used. I've never used a PIC with internal QEI, used US Digital chips though.

edit: just saw/read the post below this one, SAME PIC ! Now I know there's a LOT of errata for this PIC, which leads me to believe it's a 'die' issue ( hardware ) that may not be fixable.

Jay

Jerson · Joined: 31 Jul 2009 Posts: 126 Location: Bombay, India

With a caveat that I may be wrong, I am thinking your encoder signals are shorted together via some low value resistance like a winding or such.

temtronic · Posted: Sat Apr 13, 2019 3:21 pm

OK, I looked at the waveforms again and I can't understand the 'stepped' waveform. You should have clean 1' and 0's being 5 volt '1's and 0 '0's. Well if the PICs running at 5 volts which I think dsPics run at. Leads me to again asking for datasheet as maybe the sensor is really a 3 volt device ??
Generic 'mice' always give nice +5, 0V signals......BTW