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From: John Larkin on 28 Feb 2010 14:30
On Sun, 28 Feb 2010 07:25:56 -0800 (PST), Chris
<christopher.maness(a)gmail.com> wrote:

>I bread boarded my PLL yesterday. I was able to get it to lock just
>fine on a multivibrator running at 33Hz. I was able to solve the
>jitter problem by using a very large value for C1 (1000u). However,
>when I attached my cameras to the loop, (one running at 22.2fps and
>the other running at 25fps) the loop would lock at a frequency
>slightly above the camera speed ~39Hz. The camera has a contact that
>closes ~5ms every frame advance. I tried using the contact to pull to
>ground, and to pull to rail. I got the same result either way. Any
>suggestions?
>
>Thanks,
>Chris Maness

Contact bounce?

John

From: MooseFET on 28 Feb 2010 16:56
On Feb 28, 8:23 am, Chris <christopher.man...(a)gmail.com> wrote:
> On Feb 28, 7:39 am, MooseFET <kensm...(a)rahul.net> wrote:
>
>
>
> > On Feb 28, 7:25 am, Chris <christopher.man...(a)gmail.com> wrote:
>
> > > I bread boarded my PLL yesterday.  I was able to get it to lock just
> > > fine on a multivibrator  running at 33Hz.  I was able to solve the
> > > jitter problem by using a very large value for C1 (1000u).  However,
> > > when I attached my cameras to the loop, (one running at 22.2fps and
> > > the other running at 25fps) the loop would lock at a frequency
> > > slightly above the camera speed ~39Hz.  The camera has a contact that
> > > closes ~5ms every frame advance.  I tried using the contact to pull to
> > > ground, and to pull to rail.  I got the same result either way.  Any
> > > suggestions?
>
> > > Thanks,
> > > Chris Maness
>
> > Which phase detector are you using?
>
> > An XOR can lock to ratios of numbers of the input signal like 2/3
>
> > A tristate phase frequency comparator is bothered by contact bounce.
>
> I am using Comparator II for edge detection.  Yes, there might be some
> bounce.  How can I clean up the signal?  Also, with the 33Hz multivibe
> there is a extremely low frequency FM'ing ~1/2Hz.  Should I try a
> smaller C2 in combination with a bigger R3?
>
> Correction: the 1000u is C2.
>

Since you know the rough frequency you have options:

(1)
A one shot that has a time a little over 1/2 the cycle time can be
made so
that is only accepts the switch closures that are about far enough
apart.

(2)
A few stages of HC14s connected one to the next by a low pass RC
filter
will add delay but will also take the bounces off.

(3)
Your VCO can be running at a multiple of the input and you can use
logic from the divide down counter to only allow edges at the right
time
through. Basically this would mean to use a flip flop that is cleared
just before the time the edge is expected and gets clocked by the edge
to go high.


> Thanks,
> Chris Maness

From: Chris on 28 Feb 2010 17:48
On Feb 28, 1:56 pm, MooseFET <kensm...(a)rahul.net> wrote:
> On Feb 28, 8:23 am, Chris <christopher.man...(a)gmail.com> wrote:
>
>
>
> > On Feb 28, 7:39 am, MooseFET <kensm...(a)rahul.net> wrote:
>
> > > On Feb 28, 7:25 am, Chris <christopher.man...(a)gmail.com> wrote:
>
> > > > I bread boarded my PLL yesterday.  I was able to get it to lock just
> > > > fine on a multivibrator  running at 33Hz.  I was able to solve the
> > > > jitter problem by using a very large value for C1 (1000u).  However,
> > > > when I attached my cameras to the loop, (one running at 22.2fps and
> > > > the other running at 25fps) the loop would lock at a frequency
> > > > slightly above the camera speed ~39Hz.  The camera has a contact that
> > > > closes ~5ms every frame advance.  I tried using the contact to pull to
> > > > ground, and to pull to rail.  I got the same result either way.  Any
> > > > suggestions?
>
> > > > Thanks,
> > > > Chris Maness
>
> > > Which phase detector are you using?
>
> > > An XOR can lock to ratios of numbers of the input signal like 2/3
>
> > > A tristate phase frequency comparator is bothered by contact bounce.
>
> > I am using Comparator II for edge detection.  Yes, there might be some
> > bounce.  How can I clean up the signal?  Also, with the 33Hz multivibe
> > there is a extremely low frequency FM'ing ~1/2Hz.  Should I try a
> > smaller C2 in combination with a bigger R3?
>
> > Correction: the 1000u is C2.
>
> Since you know the rough frequency you have options:
>
> (1)
> A one shot that has a time a little over 1/2 the cycle time can be
> made so
> that is only accepts the switch closures that are about far enough
> apart.
>
> (2)
> A few stages of HC14s connected one to the next by a low pass RC
> filter
> will add delay but will also take the bounces off.
>
> (3)
> Your VCO can be running at a multiple of the input and you can use
> logic from the divide down counter to only allow edges at the right
> time
> through.  Basically this would mean to use a flip flop that is cleared
> just before the time the edge is expected and gets clocked by the edge
> to go high.
>
> > Thanks,
> > Chris Maness

I was thinking about #1 just using a NE555 for a one shot @ 1/2 a
cycle. Also, the NE555 (1.5 cycle one shot) could be used with an AND
gate to shut the output off when there is no signal from the camera.
Starting to feel like all of this would be better done in software.

Thanks,
Chris Maness
From: Mark on 28 Feb 2010 21:46
On Feb 28, 10:25 am, Chris <christopher.man...(a)gmail.com> wrote:
> I bread boarded my PLL yesterday.  I was able to get it to lock just
> fine on a multivibrator  running at 33Hz.  I was able to solve the
> jitter problem by using a very large value for C1 (1000u).  However,
> when I attached my cameras to the loop, (one running at 22.2fps and
> the other running at 25fps) the loop would lock at a frequency
> slightly above the camera speed ~39Hz.  The camera has a contact that
> closes ~5ms every frame advance.  I tried using the contact to pull to
> ground, and to pull to rail.  I got the same result either way.  Any
> suggestions?
>
> Thanks,
> Chris Maness

low pass filter the ref signal coming from the camera contacts, there
may be bounce and the PLL is correctly locking to the "higher
frequency" as it sees those extra edges.

Mark
From: Chris on 1 Mar 2010 01:20
On Feb 28, 6:46 pm, Mark <makol...(a)yahoo.com> wrote:
> On Feb 28, 10:25 am, Chris <christopher.man...(a)gmail.com> wrote:
>
> > I bread boarded my PLL yesterday.  I was able to get it to lock just
> > fine on a multivibrator  running at 33Hz.  I was able to solve the
> > jitter problem by using a very large value for C1 (1000u).  However,
> > when I attached my cameras to the loop, (one running at 22.2fps and
> > the other running at 25fps) the loop would lock at a frequency
> > slightly above the camera speed ~39Hz.  The camera has a contact that
> > closes ~5ms every frame advance.  I tried using the contact to pull to
> > ground, and to pull to rail.  I got the same result either way.  Any
> > suggestions?
>
> > Thanks,
> > Chris Maness
>
> low pass filter the ref signal coming from the camera contacts, there
> may be bounce and the PLL is correctly locking to the "higher
> frequency" as it sees those extra edges.
>
> Mark

That sounds like a good Idea. What would be a good cutoff frequency?

Chris
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