Electronics > Beginners

replace 3.58MHz with 3.579545MHz

<< < (3/7) > >>

Brumby:
This is what I would expect:


--- Quote from: mcovington on December 29, 2019, 09:03:29 pm ---3.579545-MHz crystals are extremely common and are commonly called 3.58-MHz.
--- End quote ---
I mean, if those crystals are as common as mud and there aren't any other frequencies in that vicinity which you would come across very often (if at all), then there is going to be a shorthand version of how it gets referred to.  Think of it ... if you're in a group off electronics people familiar with this area and you started referring to this common-as-anything crystal to 6 decimal places, then you're going to waste a lot of time reciting them and all those around you are going to look at you funny.  They know what you mean - and 2 decimals is all that needs to be mentioned to make it clear.


--- Quote ---I have even used them to substitute for 4-MHz crystals in microprocessor circuits.

--- End quote ---
A lot of the time, the precise frequency isn't all that important when driving microprocessors unless you have critical time-keeping requirements.

T3sl4co1l:
Yeah, worst possible case, NMOS Z80, it won't know the difference.  IIRC, they start getting loopy above 5 or 6MHz and below 2 or 1MHz.  CMOS CPUs work down to DC.

Anything to do with precise timing or output signals, that's an exercise for the student.

Tim

schmitt trigger:
One of my favorite ICs back in the 80s, was a device from National Semi, which generated a 60 Hz signal from a 3.579545 Mhz crystal.

It was a NM-something, and very useful for a timing backup for clocks.

mcovington:
MM5369AA, I believe it was.  I used it in, among other things, a power supply for astronomical telescopes (with 60-Hz motors, accurate frequency needed) in the first edition of my book Astrophotography for the Amateur.  The chip is no longer available.  I did a PIC-based circuit later to replace it.

schmitt trigger:
Exactly, that was the part number.

To obtain 60 Hz from an oddball frequency such as 3.579545 MHz, it alternated the frequency’s division ratio.

As such, the output wasn’t a 50% duty.

Sadly it is now obsolete, but can be emulated with any modern microcontroller.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod