CD4093 oscillator frequency

Measure the P-P voltage and recalculate using that?

A 200 resistor across a crystal is basically shorting the crystal.

Your calculations. You could also check if the parameters of the CD4093 are correct, by measurement.

I've made a PWM-amplifier once with a quad nand and two BC547s. That was fun. But I don't remember how I arrived at the correct frequency. Probably trial and error.

A 30 kHz ceramic resonator? How large would those physically be? I mean, they are not available for that low frequency.

joe

Yep, that datasheet :-)

At 5V suply CD logic is like molasses. The output impedance easily enters the kOhm range so your 200ohms in reality is much higher.

Not really with this one, I'd use a watch crystal chip for that but a

Use a 74HC series device if you want to operate with 5V supply. Or make the resistor tens of kOhms (or better hundreds) and the cap smaller. But if you want any kind of accuracy a CD4093 isn't going to cut it with a

Ah. That's it. I'm so used to using the HC stuff I'd forgotten that. I'll try recalculating for a different RC network...

I've got 60 and 100 KHz tuning fork (watch, I guess) crystals I bought on a lark which were not terribly expensive (right, sorry, they cost the earth by jeorg standards, where all pennies must scream.)

For the common 32.768 KHz onesies look like $0.18 and up if "around 30" is "within 10%", 60 KHz looks like $0.49 (or $1.75 in SMT) and would give you an honest 30 with a divide circuit.

Ecnerwal Wrote in message:

The precise freq. isn't critical, just would like it to be fairly stable and above the audio range. I think a watch crystal would work fine

For practical purposes, the threshold(s) are one-half of the CMOS supply voltage (at room temp). Reasonably dependable.

Most of the CMOS oscillators I've seen, the resistor is more like 2M.

The OP could check out the catalogues from various crystal/resonator manufacturers - many include example circuits.

"half" in the sense of "anywhere between one third and two thirds."

Cheers

Phil Hobbs

I'm now using a 68k R and a 680 p polystyrene capacitor - I'm right in the 32 kHz ballpark.

when a CD4060 is run from crystal it seems that it does not use a schmitt inverter

what frequency are you chasing? 32768 Hz is a standard frequency.

And that, on the properly specified kinds only.

I've seen microcontrollers and shitty ASICs like that where the input thresholds are 20-80%, I think even 10-90%. One boggles at how their process can even be so awful!

Tim

and smiles at the price

You'll be hosting Romper Room next...

And you'll be organizing Canasta games at the managed care facility.

Here's another stupid question from me. If the output impedance inflates the value of his R then why is his frequency lower than he calculated?

Nevermind. I wrote that a few seconds ago standing on my head.

Mornings are the times for thinking...this time of the afternoon is for drinking