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Show"N"Tell ( Your Machines) / Re: The Laser Project.
« on: May 27, 2013, 03:37:48 AM »
Hi Brett,
I have sent you a PM but some more information for those that follow;
Initially (and as Jeff at the Warp9 forum suggested) I investigated electrical noise / incorrect earthing etc. (USB cables seldom have a screen to carry the PC earth via the USS to the Parallel Port cable screen) - once electrical noise / earthing had been ruled out my next thoughts was one of timing where the direction pulse was not being seen soon enough. Delaying the step pulses (to give the direction line transition more time) made the situation a whole lot worse so it definitely was not that.
In my mind there was always the possibility that if tri-state logic had been used in the SS design my stepper's driver could be picking up a false logic state in relation to the direction signal transitions so I tried delaying the direction signals and it worked.
Obviously, and as mentioned earlier, more investigation is required because 150nS is hardly worth considering as a delay so it may just be the Schmitt Trigger outputs which are doing the trick. As time permits I will look at this issue in more depth and post my findings.
The circuit I am using just consists of eight TTL gates, daisy chained for each direction line.
Tweakie.
I have sent you a PM but some more information for those that follow;
Initially (and as Jeff at the Warp9 forum suggested) I investigated electrical noise / incorrect earthing etc. (USB cables seldom have a screen to carry the PC earth via the USS to the Parallel Port cable screen) - once electrical noise / earthing had been ruled out my next thoughts was one of timing where the direction pulse was not being seen soon enough. Delaying the step pulses (to give the direction line transition more time) made the situation a whole lot worse so it definitely was not that.
In my mind there was always the possibility that if tri-state logic had been used in the SS design my stepper's driver could be picking up a false logic state in relation to the direction signal transitions so I tried delaying the direction signals and it worked.
Obviously, and as mentioned earlier, more investigation is required because 150nS is hardly worth considering as a delay so it may just be the Schmitt Trigger outputs which are doing the trick. As time permits I will look at this issue in more depth and post my findings.
The circuit I am using just consists of eight TTL gates, daisy chained for each direction line.
Tweakie.
