XO controlled 480Hz Oscillator
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From: Chris on 2 Feb 2010 12:05 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
From: Vladimir Vassilevsky on 2 Feb 2010 12:11 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? The simplest way is MCU with external crystal. For 480 Hz output, the crystal is likely to be a multiple of 3 MHz. The 12.0 MHz would be the most common. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
From: Chris on 2 Feb 2010 12:47 > The simplest way is MCU with external crystal. For 480 Hz output, the > crystal is likely to be a multiple of 3 MHz. The 12.0 MHz would be the > most common. Is an MCU the same as a PIC? Regards, Chris KQ6UP
From: Tim Wescott on 2 Feb 2010 12:53 On Tue, 02 Feb 2010 09:05:33 -0800, Chris 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. >> Crystal oscillator, divide by the appropriate (large) number. Come to think of it, a PIC may still be the smallest way to go -- one 8- pin PIC is way smaller than all the 74whatever161's you'd need, or a PAL for that matter. -- www.wescottdesign.com
From: Tim Wescott on 2 Feb 2010 12:56
On Tue, 02 Feb 2010 09:47:50 -0800, Chris wrote: >> The simplest way is MCU with external crystal. For 480 Hz output, the >> crystal is likely to be a multiple of 3 MHz. The 12.0 MHz would be the >> most common. > > Is an MCU the same as a PIC? All PICs are MCUs. Not all MCUs are PICs. The top contenders that I know of are the PIC and the AVR from Atmel. There are probably low pin- count 8051 derivatives out there, not to mention the '430 from TI. Intersil ought to revive the 1802 core, in a 16-pin package surrounded by all the usual peripherals. -- www.wescottdesign.com |