Dividing a 32768 Hz crystal frequency

I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator.

I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is  a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.

On Monday, June 26, 2023 at 10:20:48 AM UTC-4, John Woodgate wrote:
> I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator. 
> 
> I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.

You can make an oscillator out of pretty much any inverter.  I've not seen it done, but I expect you can use the reset input and Q output of the 4013, which forms an inverter.  

Just be aware that CMOS has little output drive and is very sensitive to voltage spikes.  If you have any external input or output signals to these parts, they need to be well protected. 

-- 

  Rick C.

  - Get 1,000 miles of free Supercharging
  - Tesla referral code - https://ts.la/richard11209

mandag den 26. juni 2023 kl. 16.20.48 UTC+2 skrev John Woodgate:
> I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator. 
> 
> I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.

get a  32768 Hz oscillator instead of a crystal, saves alot of headaches

On Mon, 26 Jun 2023 08:00:44 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>mandag den 26. juni 2023 kl. 16.20.48 UTC+2 skrev John Woodgate:
>> I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator. 
>> 
>> I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.
>
>get a  32768 Hz oscillator instead of a crystal, saves alot of headaches

Yes. Oscillators made from a crystal and a chip and some caps and
maybe a resistor, tend to not oscillate. And certainly won't be PPMs
on-frequency, as a purchased oscillator usually is.

Maybe play with the math and use some other oscillator frequency and
some easy divisor?

On Tuesday, June 27, 2023 at 12:20:48 AM UTC+10, John Woodgate wrote:
> I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator. 
> 
> I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.

If you want to divide by twenty you need five stages of division. The CD4096 contains only two bistables, so it won't do it

https://pdf1.alldatasheet.com/datasheet-pdf/view/66451/INTERSIL/CD4096BMS.html

A 4017 is a divide by ten, so if you use one of the J-K bistables in in the 4096 as a divide by two you've got you divide by 20 and can use the other half to drive your oscillation.

A 4018 is more flexible.

A small programable logic device could do it in a single packages, but you have to work out how to program it, which isn't all that difficult.

I was fond of the Philips cool-runner parts about twenty years ago, and they seemed to get even easier to use when Xilinx took them over, but I never bothered to work out how to program them from my home computer (which looked as it it would be easy enough).

There's probably a chip which does exactly what you want but I've given up reading the Farnell catalogue thoroughly enough to know what it might be today.

Lasse is probably right about the 32768 oscillator. It won't be as cheap as the crystal on it own but Farnell has lots

https://www.farnell.com/datasheets/2581434.pdf

is one of many, and fairly cheap at about $1 each in small quantities. For test gear. why mess around making something you can buy?

-- 
Bill Sloman, Sydney

On 6/26/2023 11:09 AM, John Larkin wrote:
> On Mon, 26 Jun 2023 08:00:44 -0700 (PDT), Lasse Langwadt Christensen
> <langwadt@fonz.dk> wrote:
> 
>> mandag den 26. juni 2023 kl. 16.20.48 UTC+2 skrev John Woodgate:
>>> I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator.
>>>
>>> I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.
>>
>> get a  32768 Hz oscillator instead of a crystal, saves alot of headaches
> 
> Yes. Oscillators made from a crystal and a chip and some caps and
> maybe a resistor, tend to not oscillate. And certainly won't be PPMs
> on-frequency, as a purchased oscillator usually is.
> 
> Maybe play with the math and use some other oscillator frequency and
> some easy divisor?
> 

Yeah 32768/20 seems like kind of weird reference frequency, anyway. 1 
kHz is easy from a 4.096 MHz crystal and a 4060.

On 6/26/2023 10:41 AM, Ricky wrote:
> On Monday, June 26, 2023 at 10:20:48 AM UTC-4, John Woodgate wrote:
>> I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator.
>>
>> I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.
> 
> You can make an oscillator out of pretty much any inverter.  I've not seen it done, but I expect you can use the reset input and Q output of the 4013, which forms an inverter.
> 
> Just be aware that CMOS has little output drive and is very sensitive to voltage spikes.  If you have any external input or output signals to these parts, they need to be well protected.
> 

Yes, use a 74HCxxxx if it's available unless there's some pressing need 
to use the old CD series, hard to think of a good reason to though if 
there's a silicon-gate equivalent.

On Monday, June 26, 2023 at 3:42:02 PM UTC+1, Ricky wrote:
> On Monday, June 26, 2023 at 10:20:48 AM UTC-4, John Woodgate wrote: 
> > I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator. 
> > 
> > I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.
> You can make an oscillator out of pretty much any inverter. I've not seen it done, but I expect you can use the reset input and Q output of the 4013, which forms an inverter. 
> 
> Just be aware that CMOS has little output drive and is very sensitive to voltage spikes. If you have any external input or output signals to these parts, they need to be well protected. 
> 
> -- 
> 
> Rick C. 
> 
> - Get 1,000 miles of free Supercharging 
> - Tesla referral code - https://ts.la/richard11209
Thank you. That is helpful.

On Monday, June 26, 2023 at 4:00:50 PM UTC+1, Lasse Langwadt Christensen wrote:
> mandag den 26. juni 2023 kl. 16.20.48 UTC+2 skrev John Woodgate: 
> > I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator. 
> > 
> > I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.
> get a 32768 Hz oscillator instead of a crystal, saves alot of headaches
I'm not sure what you mean by 'a 32768 Hz oscillator'?  Part number? Web site?

On Monday, June 26, 2023 at 4:09:51 PM UTC+1, John Larkin wrote:
> On Mon, 26 Jun 2023 08:00:44 -0700 (PDT), Lasse Langwadt Christensen 
> <lang...@fonz.dk> wrote: 
> 
> >mandag den 26. juni 2023 kl. 16.20.48 UTC+2 skrev John Woodgate: 
> >> I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator. 
> >> 
> >> I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine. 
> > 
> >get a 32768 Hz oscillator instead of a crystal, saves alot of headaches
> Yes. Oscillators made from a crystal and a chip and some caps and 
> maybe a resistor, tend to not oscillate. And certainly won't be PPMs 
> on-frequency, as a purchased oscillator usually is. 
> 
> Maybe play with the math and use some other oscillator frequency and 
> some easy divisor?
I think I'd be very lucky to find a better combination of crystal frequency and division ratio. But if you could suggest a simple way of getting closer to 1591.55 Hz I would be very interested.