XO controlled 480Hz Oscillator
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From: Silvar Beitel on 2 Feb 2010 12:58 On Feb 2, 11:29 am, Chris <christopher.man...(a)gmail.com> wrote: > What is the simplest way to get 480Hz from a crystal controlled > oscillator? Looks like most of the pre-packaged XO's and VCXO, seem > to put out much higher frequencies. Would a series of dividers be the > best way? > > Thanks, > Chris KQ6UP Would a CD4060B + 7.86432 MHz crystal + 1 resistor (maybe 2) + 2 caps running at 12 volts work for you? Output (rail-to-rail square wave) from Q14. -- Silvar Beitel
From: Chris on 2 Feb 2010 13:34 On Feb 2, 9:58 am, Silvar Beitel <silverbee...(a)net1plus.com> wrote: > On Feb 2, 11:29 am, Chris <christopher.man...(a)gmail.com> wrote: > > > What is the simplest way to get 480Hz from a crystal controlled > > oscillator? Looks like most of the pre-packaged XO's and VCXO, seem > > to put out much higher frequencies. Would a series of dividers be the > > best way? > > > Thanks, > > Chris KQ6UP > > Would a CD4060B + 7.86432 MHz crystal + 1 resistor (maybe 2) + 2 caps > running at 12 volts work for you? Output (rail-to-rail square wave) > from Q14. > > -- > Silvar Beitel That sounds pretty easy divide by 2^14. Would that be a custom crystal, or a standard freq? I will be trying to repair a 480Hz standard tuning fork. It is actually a 960Hz fork that had it's divide by 2 flip flop die. It is from a 70's vintage piece of equipment. The fork is hermetically sealed with solder in a can. I try to get in there tonight, and if the dead part is some obsolete IC or something, I will probably replace with a crystal and divider to get my 480Hz. A crystal would be more quiet and stable I believe. Thanks, Chris KQ6UP
From: miso on 2 Feb 2010 14:25 On Feb 2, 9:05 am, Chris <christopher.man...(a)gmail.com> wrote: > On Feb 2, 8:46 am, Tim Wescott <t...(a)seemywebsite.com> wrote: > > > On Tue, 02 Feb 2010 08:29:47 -0800, Chris wrote: > > > What is the simplest way to get 480Hz from a crystal controlled > > > oscillator? Looks like most of the pre-packaged XO's and VCXO, seem to > > > put out much higher frequencies. Would a series of dividers be the best > > > way? > > > > Thanks, > > > Chris KQ6UP > > > 480Hz what? Forever constant frequency square wave? Yes. > > No need to vary the frequency. Yes, square wave 480Hz 12V swing into > a high Z load. > > > If you want to vary the frequency you may want to use a programmable > > divider, and the easiest way to do _that_ may well be to use a small > > microprocessor, particularly one with a hardware timer. > > For this application the frequency is fixed, but it needs to be > accurate. I don't think a xtal oven is called for, but I do need the > rock. > > > > > If you want a sine wave you could either divide down to a 480Hz square > > wave and filter, at the cost of a fairly elaborate analog filter. Or you > > could use that microprocessor again to generate a 480Hz almost-sine wave > > to a DAC or PWM, in which case you can use a much less elaborate (and > > therefor easier to design and cheaper) analog filter. > > Square wave, sorry for not clarifying. > > > > > If you can live with a healthy bit of output impedance, you could do this > > with PIC, a resistor, a cap, and either a crystal and it's capacitors or > > a crystal oscillator that'll be bigger than the PIC. > > > --www.wescottdesign.com > > Thanks, > Chris KQ6UP I'm old school, so I would build two divider chains out of logic gates. The first divider gets you to 960Hz, but it probably won't be a square wave. You use a binary counter and some gates to do the division. Follow up with a divide by two to get a square wave at 480Hz. You need a level shifter to get the larger 12V signal. You should investigate if the uP scheme causes jitter in the signal. In the dark ages when I played with uP, they always had peripheral timer chips that the uP could control so that the division would be jitter free. Maybe modern uP have these built in.
From: Silvar Beitel on 2 Feb 2010 14:37 On Feb 2, 1:34 pm, Chris <christopher.man...(a)gmail.com> wrote: > On Feb 2, 9:58 am, Silvar Beitel <silverbee...(a)net1plus.com> wrote: > > Would a CD4060B + 7.86432 MHz crystal + 1 resistor (maybe 2) + 2 caps > > running at 12 volts work for you? Output (rail-to-rail square wave) > > from Q14. > That sounds pretty easy divide by 2^14. Would that be a custom > crystal, or a standard freq? Guessing: not standard. But check crystal suppliers / distributors and see. How close to 480 Hz do you need the output to be? If not particularly close (i.e. stability is your main requirement), perhaps a catalog part will work. Good luck. -- Silvar Beitel
From: Bill Sloman on 2 Feb 2010 15:43
On Feb 2, 7:34 pm, Chris <christopher.man...(a)gmail.com> wrote: > On Feb 2, 9:58 am, Silvar Beitel <silverbee...(a)net1plus.com> wrote: > > > > > On Feb 2, 11:29 am, Chris <christopher.man...(a)gmail.com> wrote: > > > > What is the simplest way to get 480Hz from a crystal controlled > > > oscillator? Looks like most of the pre-packaged XO's and VCXO, seem > > > to put out much higher frequencies. Would a series of dividers be the > > > best way? > > > > Thanks, > > > Chris KQ6UP > > > Would a CD4060B + 7.86432 MHz crystal + 1 resistor (maybe 2) + 2 caps > > running at 12 volts work for you? Output (rail-to-rail square wave) > > from Q14. > > > -- > > Silvar Beitel > > That sounds pretty easy divide by 2^14. Would that be a custom > crystal, or a standard freq? Farnell doesn't stock it, so it probably isn't a standard frequency, but getting a custom frequency in that range is no big deal. > I will be trying to repair a 480Hz standard tuning fork. It is > actually a 960Hz fork that had it's divide by 2 flip flop die. It is > from a 70's vintage piece of equipment. The fork is hermetically > sealed with solder in a can. I try to get in there tonight, and if > the dead part is some obsolete IC or something, I will probably > replace with a crystal and divider to get my 480Hz. A crystal would > be more quiet and stable I believe. Probably. Look at the 74HC401013 from NCXP or TI if you want to use a standard crystal - it gives you a programmable 8-bit divider in a single package, and you can cascade them if you want more bits http://www.nxp.com/documents/data_sheet/74HC40103.pdf You will have to buffer the output to get a 12V swing, or use the slower HEF401013BEY from ST Microelectronics. -- Bill Sloman, Nijmegen |