24Hz to 60Hz PLL?
in [Design]
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From: JosephKK on 15 Feb 2010 21:45 On Sat, 13 Feb 2010 07:16:21 -0800 (PST), Chris <christopher.maness(a)gmail.com> wrote: >On Feb 12, 3:21 pm, Fred Bartoli <" "> wrote: >> Chris a écrit : >> >> > I need to make a PLL that slaves to a 24Hz square wave. The output of >> > the loop would be a 60Hz square wave. Any CMOS level chips that would >> > be good for this? I understand that I would need to divide by a >> > decimal value of 2.5 for the loop. >> >> PLLs a those low frequencies are real slow if you need some 'jitter >> free' output. >> >> Square waves have only odd harmonics. You could square up your 24 Hz, >> apply it to a narrow 120Hz BPF, then divide by two. >> >> -- >> Thanks, >> Fred. > >The 24Hz is square. What would I use for a BP filter at such a LF >without having a very large inductor? > >Chris Even the likes of myself have done that with RC filters. You might want to use good op-amps (low noise, low bias current) though.
From: Chris on 15 Feb 2010 23:29 On Feb 15, 6:45 pm, "JosephKK"<quiettechb...(a)yahoo.com> wrote: > On Sat, 13 Feb 2010 07:16:21 -0800 (PST), Chris <christopher.man...(a)gmail..com> wrote: > >On Feb 12, 3:21 pm, Fred Bartoli <" "> wrote: > >> Chris a écrit : > > >> > I need to make a PLL that slaves to a 24Hz square wave. The output of > >> > the loop would be a 60Hz square wave. Any CMOS level chips that would > >> > be good for this? I understand that I would need to divide by a > >> > decimal value of 2.5 for the loop. > > >> PLLs a those low frequencies are real slow if you need some 'jitter > >> free' output. > > >> Square waves have only odd harmonics. You could square up your 24 Hz, > >> apply it to a narrow 120Hz BPF, then divide by two. > > >> -- > >> Thanks, > >> Fred. > > >The 24Hz is square. What would I use for a BP filter at such a LF > >without having a very large inductor? > > >Chris > > Even the likes of myself have done that with RC filters. > You might want to use good op-amps (low noise, low bias current) though. I am noticing there seems to be many ways to skin a cat ;o) I will order the chips for the PLL as this seems to be the most straight foreword way, and proto it on my solderless bread board. If it does not work, I am only out of a couple of bucks and wiser for the experience. Thanks Guys, I will report back. Chris Maness
From: MooseFET on 16 Feb 2010 09:42 On Feb 15, 6:45 pm, "JosephKK"<quiettechb...(a)yahoo.com> wrote: > On Sat, 13 Feb 2010 07:16:21 -0800 (PST), Chris <christopher.man...(a)gmail..com> wrote: > >On Feb 12, 3:21 pm, Fred Bartoli <" "> wrote: > >> Chris a écrit : > > >> > I need to make a PLL that slaves to a 24Hz square wave. The output of > >> > the loop would be a 60Hz square wave. Any CMOS level chips that would > >> > be good for this? I understand that I would need to divide by a > >> > decimal value of 2.5 for the loop. > > >> PLLs a those low frequencies are real slow if you need some 'jitter > >> free' output. > > >> Square waves have only odd harmonics. You could square up your 24 Hz, > >> apply it to a narrow 120Hz BPF, then divide by two. > > >> -- > >> Thanks, > >> Fred. > > >The 24Hz is square. What would I use for a BP filter at such a LF > >without having a very large inductor? > > >Chris > > Even the likes of myself have done that with RC filters. > You might want to use good op-amps (low noise, low bias current) though. Making the filter have a notch at the 3rd harmonic and a peak at the 5th is easier than trying to make just a peak at 5th that excludes the 3rd well enough. A second notch at the 7th harmonic may be needed. If you want to stay in the semi-digital mode a little longer, you can make some oneshot like circuits that construct this: ....---................---........---............. ---......----------......--------......---------- .......---..........---..............---.......... With just two RCs, you can make the 5th harmonic much larger than the other components. This replaces one of the pole pairs in the filter with some oneshots.
From: Michael A. Terrell on 18 Feb 2010 10:22 Jim Thompson wrote: > > Michael A. Terrell wrote: > > > > Microdyne was still using a second source version of the MC4044 ten > >years ago. We were having trouble getting a good supply, but i couldn't > >convince them to switch to the 4046. The 'Engineer' responsible for > >supporting older designs insisted it couldn't be used, because it was > >too slow. He wouldn't look at the 20 year old drawings, and wouldn't > >admit that the PLL only had to lock to a 100 KHz reference. > > I have no idea who made the 4046 copy originally, but they blundered > several features :-( Wasn't that designed by, or for RCA in the early '70s? I know someone who worked for RCA at that time, but he was at the fab. -- Greed is the root of all eBay.
From: Jim Thompson on 18 Feb 2010 10:51
On Thu, 18 Feb 2010 10:22:36 -0500, "Michael A. Terrell" <mike.terrell(a)earthlink.net> wrote: > >Jim Thompson wrote: >> >> Michael A. Terrell wrote: >> > >> > Microdyne was still using a second source version of the MC4044 ten >> >years ago. We were having trouble getting a good supply, but i couldn't >> >convince them to switch to the 4046. The 'Engineer' responsible for >> >supporting older designs insisted it couldn't be used, because it was >> >too slow. He wouldn't look at the 20 year old drawings, and wouldn't >> >admit that the PLL only had to lock to a 100 KHz reference. >> >> I have no idea who made the 4046 copy originally, but they blundered >> several features :-( > > > Wasn't that designed by, or for RCA in the early '70s? I know >someone who worked for RCA at that time, but he was at the fab. I think you're right, Michael. "CD"4046 seems to be the very first moniker. I've not actually tried the current 74HC4046 version but, were it done right, with today's processing, it could be a screamer. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |