XO controlled 480Hz Oscillator

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It also has a nice oscillator section so you don't need an external one. If you use the HC version, you can use a fairly high frequency crystal

As Moosefet mentioned, if you use a 3.29136MHz crystal and divide it by 8192 you'll get the 480 Hz you want. The 4060 has an 8192 ouput on Q13.

Ed

Tim Wescott schrieb:

Hello,

but if they deliver only a multiple of 480 Hz less external frequency dividers would be necessary compared with a crystal oscillator only.

Bye

Vladimir Vassilevsky schrieb:

Hello,

but for 480 Hz out of 12 MHz, the divider is 25. If a square wave is necessary, better use a 24 MHz crystal and divide two times by five and then by two.

Bye

I'd suggest a PIC12F508 and a standard 3.6864MHz crystal (eg. Citizen HC49US-3.6864MABJ-UB) which total less than $2 one-off.

To get exact 50% duty cycle 480Hz square waves you need exactly 960 instruction cycles between toggles during which time you can count down from 255 a few times, count down from something less than 255 once, and yank the leash of the WDT, and loop back. Easily done in a handful of lines of assembler. No need for interrupts, timers or any other fancy stuff.

If start-up really has to be guaranteed, best to use an external reset chip (eg. MCP100) or use a chip with built-in BOR.

It would be possible to use something like a 12F635 (which is guaranteed to work to 20MHz) and a 12.000MHz crystal, setting up all the additional registers (to turn off the analog stuff etc.) would be somewhat irritating and tedious for a one-off job.

Best regards, Spehro Pefhany

????

For 480 Hz square wave out of 12 MHz, the divider is 12500.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

OK this is probably a stupid idea. But could you phase lock to the

George H.

On Feb 2, 9:46=A0pm, ehsjr wrote: [..3.29136MHz..]

I suggest the HC4060 not the CD4060. The HC has a smaller delay so making a good oscillator a 3.29136MHz is easier with it.

Follow the app notes

With a HC4060 you need fewer instructions

Connect to AC, 3 full wave rectifiers in series, then comparator. Adjust DC bias at each rectifier for 50/50 duty circle?

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Vladimir Vassilevsky schrieb:

Hello,

i forgot a factor of 1000....

Bye

AC Line is sort of sinusoidal, so 8th harmonic content is probably not all that wonderful, but a PLL with a DIV8 as feedback should work great... do it all in cheapy CMOS, at low power ;-) ...Jim Thompson

AC -> XOR gate -> RC -> XOR gate -> RC -> XOR gate

:)))))

BTW, I actually used that sort of thing for frequency doubling in one of the projects...

VLV

Yep. I've done that sort of thing clear up into the GHz range. ...Jim Thompson

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I called a local custom crystal manufacturer -- $18 for a 7864320 Hz Crystal. The most straight forward approach looks like the CD4060B. I found a source $3 for a pack of 25. If you look at Fig. 13 in the data sheet for the CD4060B, it shows how to hook the crystal up to the chip. All I need is two caps and two resistors. The crystal manufacturer said that he would give me the values that I need to calculate C1 and C2. I am wondering what value I would need for RC.

Thanks, Chris KQ6UP

My comment about the extra divide by two is null and void if you pick a crystal such that you can use a FF output,i.e. the crystal is some power of two of 480Hz.

Or spend 40 cents for the 3.93216MHz crystal the MooseFET recommended. In stock at Digikey. Use Q13 to divide by 8192.

Ed

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=A0 =A0 ...Jim Thompson

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Yeah, that's what I meant. I've never done a PLL circuit.... But if I can 'restrict' the VCO so that it only 'goes' near 480 Hz, then it should be a simple matter to 'lock-in'.

George H.

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=A0 =A0 =A0...Jim Thompson

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Well, I already ordered the crystal. I will keep that in mind. I need to make a 60Hz VCXO in a PLL slaved to a 24Hz pulse. That is for later though.

Regards, Chris Maness