Phase Lock Indicator
in [Design]
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From: Grant on 19 Mar 2010 16:37 On Fri, 19 Mar 2010 10:02:09 -0700 (PDT), Chris <christopher.maness(a)gmail.com> wrote: >On Mar 19, 9:35 am, D Yuniskis <not.going.to...(a)seen.com> wrote: >> Hi Chris, >> >> Chris wrote: >> > I was watching a youtube video about a Nagra reel-to-reel deck and it >> > had a neat little phase lock indication that I would like to >> >> No, this indicates *frequency* lock. It was also commonly >> used on some turntables -- with multiple sets of "spokes" (your >> term) on the platter. >> >> > duplicate. However, I want to make a stroboscope with an LED >> > illuminating a small white disk with 5 black spokes on it. When the >> > spokes appear stationary phase lock is achieved. The ratio is 5/2. I >> > realize the ratio has to be a whole integer number for this phase >> > indicator to work. This is easy as I can tap the part of my circuit >> > that gives a 10:2 phase ratio and paint 5 spokes on the disks. I am >> > confident it will work. I am just wondering if they make small ac >> > sync motors that will run off of low voltage (i.e. 9V) AC. It would >> > need almost no torque. It would just be turning a tiny white disk >> > over a window in my project. >> >> Presumably, you will be varying <something> to adjust the speed >> of your motor to bring the "rotating disk" into frequency lock with >> the strobe? (or, are you varying the strobe rate to cause >> the disk to "appear" to stop -- it's unclear what your purpose >> here is) E.g., you might find it easier to use a small *DC* motor >> (e.g., out of a child's toy) and control the drive to that. > >Well, adding the DC motor controller would double the complexity of >the whole circuit. But looking around I did not find too many low >voltage motors, and the ones I did find had reduction gears. Small stepper? Really tiny, like the old floppy stepper that shrunk to about 1/2 " diameter over the years. Speed control is open loop. > >I will have to rethink this. My current design has an LED that lights >up when lock is achieved, but I am not sure it will be dim enough when >the frequency is not locked. I might have to set up some sort of >threshold that only indicates when there is a steady lock. Here is my >current design: > >http://chrismaness.com/backend/pulse_converter_v3.jpg Image is too small for my tired eyes. Grant.
From: Chris on 19 Mar 2010 16:55 On Mar 19, 1:37 pm, Grant <o...(a)grrr.id.au> wrote: > On Fri, 19 Mar 2010 10:02:09 -0700 (PDT), Chris <christopher.man...(a)gmail..com> wrote: > >On Mar 19, 9:35 am, D Yuniskis <not.going.to...(a)seen.com> wrote: > >> Hi Chris, > > >> Chris wrote: > >> > I was watching a youtube video about a Nagra reel-to-reel deck and it > >> > had a neat little phase lock indication that I would like to > > >> No, this indicates *frequency* lock. It was also commonly > >> used on some turntables -- with multiple sets of "spokes" (your > >> term) on the platter. > > >> > duplicate. However, I want to make a stroboscope with an LED > >> > illuminating a small white disk with 5 black spokes on it. When the > >> > spokes appear stationary phase lock is achieved. The ratio is 5/2.. I > >> > realize the ratio has to be a whole integer number for this phase > >> > indicator to work. This is easy as I can tap the part of my circuit > >> > that gives a 10:2 phase ratio and paint 5 spokes on the disks. I am > >> > confident it will work. I am just wondering if they make small ac > >> > sync motors that will run off of low voltage (i.e. 9V) AC. It would > >> > need almost no torque. It would just be turning a tiny white disk > >> > over a window in my project. > > >> Presumably, you will be varying <something> to adjust the speed > >> of your motor to bring the "rotating disk" into frequency lock with > >> the strobe? (or, are you varying the strobe rate to cause > >> the disk to "appear" to stop -- it's unclear what your purpose > >> here is) E.g., you might find it easier to use a small *DC* motor > >> (e.g., out of a child's toy) and control the drive to that. > > >Well, adding the DC motor controller would double the complexity of > >the whole circuit. But looking around I did not find too many low > >voltage motors, and the ones I did find had reduction gears. > > Small stepper? Really tiny, like the old floppy stepper that shrunk > to about 1/2 " diameter over the years. Speed control is open loop. > > > > >I will have to rethink this. My current design has an LED that lights > >up when lock is achieved, but I am not sure it will be dim enough when > >the frequency is not locked. I might have to set up some sort of > >threshold that only indicates when there is a steady lock. Here is my > >current design: > > >http://chrismaness.com/backend/pulse_converter_v3.jpg > > Image is too small for my tired eyes. > > Grant. Thanks, Grant. I fixed it. I just had to change the RC time constant to ignore all the little fluctuations until the loop locks. Regards, Chris Maness
From: a7yvm109gf5d1 on 19 Mar 2010 23:08
On Mar 19, 3:37 pm, Grant <o...(a)grrr.id.au> wrote: > On Fri, 19 Mar 2010 10:02:09 -0700 (PDT), Chris <christopher.man...(a)gmail..com> wrote: > >On Mar 19, 9:35 am, D Yuniskis <not.going.to...(a)seen.com> wrote: > >> Hi Chris, > > >> Chris wrote: > >> > I was watching a youtube video about a Nagra reel-to-reel deck and it > >> > had a neat little phase lock indication that I would like to > > >> No, this indicates *frequency* lock. It was also commonly > >> used on some turntables -- with multiple sets of "spokes" (your > >> term) on the platter. > > >> > duplicate. However, I want to make a stroboscope with an LED > >> > illuminating a small white disk with 5 black spokes on it. When the > >> > spokes appear stationary phase lock is achieved. The ratio is 5/2.. I > >> > realize the ratio has to be a whole integer number for this phase > >> > indicator to work. This is easy as I can tap the part of my circuit > >> > that gives a 10:2 phase ratio and paint 5 spokes on the disks. I am > >> > confident it will work. I am just wondering if they make small ac > >> > sync motors that will run off of low voltage (i.e. 9V) AC. It would > >> > need almost no torque. It would just be turning a tiny white disk > >> > over a window in my project. > > >> Presumably, you will be varying <something> to adjust the speed > >> of your motor to bring the "rotating disk" into frequency lock with > >> the strobe? (or, are you varying the strobe rate to cause > >> the disk to "appear" to stop -- it's unclear what your purpose > >> here is) E.g., you might find it easier to use a small *DC* motor > >> (e.g., out of a child's toy) and control the drive to that. > > >Well, adding the DC motor controller would double the complexity of > >the whole circuit. But looking around I did not find too many low > >voltage motors, and the ones I did find had reduction gears. > > Small stepper? Really tiny, like the old floppy stepper that shrunk > to about 1/2 " diameter over the years. Speed control is open loop. > > > > >I will have to rethink this. My current design has an LED that lights > >up when lock is achieved, but I am not sure it will be dim enough when > >the frequency is not locked. I might have to set up some sort of > >threshold that only indicates when there is a steady lock. Here is my > >current design: > > >http://chrismaness.com/backend/pulse_converter_v3.jpg > > Image is too small for my tired eyes. > > Grant. Man, that image is too tiny for Superman's eyes. |