I want to get a 27Mhz clock signal.
I got a 27Mhz quartz crystal. I usually used a few caps and resistors along an HC inverter to get the clock signal, but never used more than 4Mhz.
for example :
**broken link removed**
Can I do the same for the 27Mhz crystal?? Do caps and resistors need to change?? I can't find clear information about this.
Thank you.
I want to get a 27Mhz clock signal.
I got a 27Mhz quartz crystal. I usually used a few caps and resistors along an HC inverter to get the clock signal, but never used more than 4Mhz.
for example :
**broken link removed**
Can I do the same for the 27Mhz crystal?? Do caps and resistors need to change?? I can't find clear information about this.
Thank you.
You need to be careful of the type of crystal you get! - by 27MHz, some crystals are overtone crystals, which means their fundamental resonance is a sub-multiple of their marked value. This means you MUST use an LC oscillator design to get the desired frequency.
Assuming you're talking about clock crystals?, a 27MHz one should be a fundamental crystal - but an RF crystal could well be overtone.
I really don't know much about quartz crystals yet.
I only used 4Mhz one with the CMOS inverters, appart from clocking PICs.
My 27Mhz crystal is like this one : **broken link removed**
The picture of the crystal is not much help, it is impossible to determine the characteristics just by looking.
I suggest that you build the oscillator using the basic inverted circuit and measure the output frequency, if it is 27 Mhz - you have cracked it!
If it is only 9Mhz, you need an overtone circuit.
Read the article in your link, it gives information on how to make an overtone crystal work in that circuit.
Just a note of caution - in the overtone mode, the overtone frequency is close to an intergral (odd) multiple but not an exact integral multiple.
I used to use 7 mHz crystals for the 21 mHz band - the oscillator was configured as a tripler, if I am not mistaken. In this case the resulting output was an exact intergral multiple.
A crystal operates by mechanically vibrating at the required frequency. For low frequencies a larger piece of quartz is used than for higher frequencies.
As the frequency goes up, the piece of quartz gets smaller and thinner, eventually it gets too small to be practical.
So for higher frequencies, the quartz vibrates on an overtone, 3, 5 or sometimes 7 times the fundamental frequency.
Just plugging a crystal into an oscillator will usually result in it oscillating on its fundamental frequency.
If the oscillator is designed for overtone operation, the crystal can vibrate at one of the overtone frequencies.
A 27Mhz crystal I would expect be a 3rd overtone type. So to operate at 27Mhz you need an overtone oscillator circuit. If you put the crystal into an ordinary oscillator you will get the 9 Mhz fundamental.
Incidently, presuming you want a logic level 27MHz for a micro or something?, I happened to notice the other day that Sky Digiboxes (UK digital satellite receivers) have a 27MHz oscillator module in them!.
danielsmusic, I used thouse circuits when using 32KhZ and 4Mhz crystal, but I don't know if it would work with 27Mhz. also, I don't know how to calculate the caps and resistor values for sure, for a certain crystal...
But, how do I know if my 27Mhz crystal is overtoned crystal, and it vibrates as a 9Mhz? How can I make it oscilate? (a simple circuit?). And if it vibrates at 9Mhz, how can I build an overtone circuit??
To clock a CPU in an old videogame system (NES). It is clocked with a 24Mhz clock, I think, but I want to make it run a bit faster. Just experimentations
To clock a CPU in an old videogame system (NES). It is clocked with a 24Mhz clock, I think, but I want to make it run a bit faster. Just experimentations
Depending on how the system is designed, changing the crystal frequency may well prevent it working at all?, if the video generation is run from this crystal.
To clock a CPU in an old videogame system (NES). It is clocked with a 24Mhz clock, I think, but I want to make it run a bit faster. Just experimentations