Quadrature decoder
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From: Jamie on 1 Jun 2010 16:31 GregS wrote: > Been searching all morning for one, and did find one by LSI/ LS7184. > > I have been looking at a drawing of one from the mid 70's, drawn up by > a coworker who is long gone. > using 74121;'s and 7400. > > I got a sample request, but I think i can do this myself quickly. I got stepper motors > and controllers requiring step and direction input. > Good thing I have this diagram because I can't find others. > Must be some other stuff around ?? > > I don't need indexing or counters. > I also see optical encoders that have the outputs I need for the controllers. > But I need something fast. > > greg That can be done with a 7474 (dual Data flip flp). I'm not going to get into details but, you do need to invert the CLK signal for each FF in the package.. Basically: Channel A drives FF #2's Data and Clr pin while it also drives the inverted circuit for the CLK of FF #1 Channel B drives FF #1's data and clr pin while it also drives the inverted circuit for the CLK for FF #2 Net results are: FF #1 outputs CW pulses while FF #2 outputs CCW pulses.. Using a basic NPN common emitter type inverting circuit for the CLK with a pull up R, should work just fine.. I guess one could also use a pre biased transistor.. P.S. Most encoders use a open collector scheme. You'll need to supply a pull-up or use a PNP inverting circuit which would remove the need of the pull up of the encoder line.. You would still need a pull down R on the inputs of the CLK I guess..
From: langwadt on 1 Jun 2010 16:38 On 1 Jun., 21:19, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- Web-Site.com> wrote: > On Tue, 01 Jun 2010 19:14:04 GMT, zekfr...(a)zekfrivolous.com (GregS) > wrote: > > > > >In article <hu3ksm$f8...(a)usenet01.srv.cis.pitt.edu>, zekfr...(a)zekfrivolous.com (GregS) wrote: > >>In article <khka065j6tthlvak56n4c9pfchpkn83...(a)4ax.com>, Jim Thompson > >> <To-Email-Use-The-Envelope-I...(a)On-My-Web-Site.com> wrote: > >>>On Tue, 01 Jun 2010 16:52:32 GMT, zekfr...(a)zekfrivolous.com (GregS) > >>>wrote: > > >>>>Been searching all morning for one, and did find one by LSI/ LS7184. > > >>>>I have been looking at a drawing of one from the mid 70's, drawn up by > >>>>a coworker who is long gone. > >>>>using 74121;'s and 7400. > > >>>>I got a sample request, but I think i can do this myself quickly. I got > >>> stepper motors > >>>>and controllers requiring step and direction input. > >>>>Good thing I have this diagram because I can't find others. > >>>>Must be some other stuff around ?? > > >>>>I don't need indexing or counters. > >>>>I also see optical encoders that have the outputs I need for the controllers. > >>>>But I need something fast. > > >>>>greg > > >>>Work statement too vague :-) > > >>>What _exactly_ are you looking for? A _detector_ that produces a > >>>pulse train _and_ direction? > > >Its been a long project. i tried to get an existing controller to work > >with my steppers. For a Z axis motion. I thought i needed more power > >so I used two audio amps to act as buffers from the stepper > >output. That did not help much. i didn't figure out why the motors > >did not like the drive output. So now I am wiring a separate Z axis > >system, which is a lot simpler than using the existing system. > >The movement is by knobs, and the speed will not > >be over 500 Hz. I also did not want to drive two steppers > >in sync, but thats what I was given. I could have also > >ordered an opto knob with step and direction outputs but its > >a time thing right now. > > >greg > > If one phase clocks a D-flop which has as "D" the other phase, you get > a direction signal. > > Pulses is pulses is pulses ;-) Maybe XOR the two phase for fun ?:-) > for most things that is a terrible way of doing it, a slight mechanical mechanical vibration or electrical noise that gets into the channel you use for pulses, will looks just like it constantly moving in one direction do it the right way and it will just toggle back and fourth -Lasse
From: Jamie on 1 Jun 2010 16:52 langwadt(a)fonz.dk wrote: > On 1 Jun., 21:19, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- > Web-Site.com> wrote: > >>On Tue, 01 Jun 2010 19:14:04 GMT, zekfr...(a)zekfrivolous.com (GregS) >>wrote: >> >> >> >> >>>In article <hu3ksm$f8...(a)usenet01.srv.cis.pitt.edu>, zekfr...(a)zekfrivolous.com (GregS) wrote: >>> >>>>In article <khka065j6tthlvak56n4c9pfchpkn83...(a)4ax.com>, Jim Thompson >>>><To-Email-Use-The-Envelope-I...(a)On-My-Web-Site.com> wrote: >>>> >>>>>On Tue, 01 Jun 2010 16:52:32 GMT, zekfr...(a)zekfrivolous.com (GregS) >>>>>wrote: >> >>>>>>Been searching all morning for one, and did find one by LSI/ LS7184. >> >>>>>>I have been looking at a drawing of one from the mid 70's, drawn up by >>>>>>a coworker who is long gone. >>>>>>using 74121;'s and 7400. >> >>>>>>I got a sample request, but I think i can do this myself quickly. I got >>>>> >>>>>stepper motors >>>>> >>>>>>and controllers requiring step and direction input. >>>>>>Good thing I have this diagram because I can't find others. >>>>>>Must be some other stuff around ?? >> >>>>>>I don't need indexing or counters. >>>>>>I also see optical encoders that have the outputs I need for the controllers. >>>>>>But I need something fast. >> >>>>>>greg >> >>>>>Work statement too vague :-) >> >>>>>What _exactly_ are you looking for? A _detector_ that produces a >>>>>pulse train _and_ direction? >> >>>Its been a long project. i tried to get an existing controller to work >>>with my steppers. For a Z axis motion. I thought i needed more power >>>so I used two audio amps to act as buffers from the stepper >>>output. That did not help much. i didn't figure out why the motors >>>did not like the drive output. So now I am wiring a separate Z axis >>>system, which is a lot simpler than using the existing system. >>>The movement is by knobs, and the speed will not >>>be over 500 Hz. I also did not want to drive two steppers >>>in sync, but thats what I was given. I could have also >>>ordered an opto knob with step and direction outputs but its >>>a time thing right now. >> >>>greg >> >>If one phase clocks a D-flop which has as "D" the other phase, you get >>a direction signal. >> >>Pulses is pulses is pulses ;-) Maybe XOR the two phase for fun ?:-) >> > > > for most things that is a terrible way of doing it, a slight > mechanical mechanical vibration > or electrical noise that gets into the channel you use for pulses, > will looks just like > it constantly moving in one direction > > do it the right way and it will just toggle back and fourth > > -Lasse Really, I've never seen that. I use a dual D-ff, the other Channel holds the Data and CLr pin to one state. Even if lets say channel A is chattering, channel B is in the middle of the phase supplying the DATA pin for the state which isn't moving. Oh well, maybe we have different circuits..
From: whit3rd on 1 Jun 2010 18:29 On Jun 1, 9:52 am, zekfr...(a)zekfrivolous.com (GregS) wrote: > Been searching all morning for one, and did find one by LSI/ LS7184. > > I have been looking at a drawing of one from the mid 70's, drawn up by > a coworker who is long gone. > using 74121;'s and 7400. > > I got a sample request, but I think i can do this myself quickly. I got stepper motors > and controllers requiring step and direction input. The controller converts that 'step and direction' into quadrature when it drives the motor. Are you SURE it requires step/direction, there's no other options? True quadrature is a four-state counter, and only transitions to adjacent states are 'known-direction' transitions. In other words, 0=>1 is an up count, 0=>3 is a down count... and 0=>2 is indecipherable. You have to decide how your decoder should misbehave in that case...
From: krw on 1 Jun 2010 19:11
On Tue, 01 Jun 2010 12:19:38 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >On Tue, 01 Jun 2010 19:14:04 GMT, zekfrivo(a)zekfrivolous.com (GregS) >wrote: > >>In article <hu3ksm$f87$3(a)usenet01.srv.cis.pitt.edu>, zekfrivo(a)zekfrivolous.com (GregS) wrote: >>>In article <khka065j6tthlvak56n4c9pfchpkn83k0t(a)4ax.com>, Jim Thompson >>> <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >>>>On Tue, 01 Jun 2010 16:52:32 GMT, zekfrivo(a)zekfrivolous.com (GregS) >>>>wrote: >>>> >>>>>Been searching all morning for one, and did find one by LSI/ LS7184. >>>>> >>>>>I have been looking at a drawing of one from the mid 70's, drawn up by >>>>>a coworker who is long gone. >>>>>using 74121;'s and 7400. >>>>> >>>>>I got a sample request, but I think i can do this myself quickly. I got >>>> stepper motors >>>>>and controllers requiring step and direction input. >>>>>Good thing I have this diagram because I can't find others. >>>>>Must be some other stuff around ?? >>>>> >>>>>I don't need indexing or counters. >>>>>I also see optical encoders that have the outputs I need for the controllers. >>>>>But I need something fast. >>>>> >>>>>greg >>>> >>>>Work statement too vague :-) >>>> >>>>What _exactly_ are you looking for? A _detector_ that produces a >>>>pulse train _and_ direction? >> >>Its been a long project. i tried to get an existing controller to work >>with my steppers. For a Z axis motion. I thought i needed more power >>so I used two audio amps to act as buffers from the stepper >>output. That did not help much. i didn't figure out why the motors >>did not like the drive output. So now I am wiring a separate Z axis >>system, which is a lot simpler than using the existing system. >>The movement is by knobs, and the speed will not >>be over 500 Hz. I also did not want to drive two steppers >>in sync, but thats what I was given. I could have also >>ordered an opto knob with step and direction outputs but its >>a time thing right now. >> >>greg > >If one phase clocks a D-flop which has as "D" the other phase, you get >a direction signal. You only get the direction once per "cycle". The four flip-flop (two two-bit shift registers) and XOR solution updates every quarter cycle and is more stable around edges. >Pulses is pulses is pulses ;-) Maybe XOR the two phase for fun ?:-) |