tomcody Posted January 31, 2011 Report Share Posted January 31, 2011 Hello everybody, I'm starting gathering the part to make an midibox fm and I realized the difference between a crystal and oscillator ... but too late :tongue: 'cuase I bought a bunch of crystal from ebay. I know there are a lot of webshops but the shipping to my country are very expensive compared to ebay. So I've found this page looking for a solution: http://www.gaby.de/z80/uexosc.htm I saw the scope pictures about the 74LS00 circuit and looks like a nice TTL pulse at the output :thumbsup: , so this may work, but the guy doesn't specify the max frec. this cicuit will work (the circuit uses a 4 MHz crystal), maybe a 74HC00, I don't know. The bad thing is if someone choose this solution needs to make a circuit apart for this or to know how to use the eagle to edit the schematic. Have anyone use something like this? What do you think? Thanks you. TomCody. Quote Link to comment Share on other sites More sharing options...
nILS Posted January 31, 2011 Report Share Posted January 31, 2011 I think you should ask around if some midiboxer is willing to forward you a crystal oscillator. Quote Link to comment Share on other sites More sharing options...
Janis1279 Posted January 31, 2011 Report Share Posted January 31, 2011 I use a crystal oscilator. The specification for the some 74 series logic ICs : 74HC and 74HCT family characteristics: 74HC Supply: 2 to 6V, small fluctuations are tolerated.74HCT Supply: 5V ±0.5V, a regulated supply is best.Inputs have very high impedance (resistance), this is good because it means they will not affect the part of the circuit where they are connected. However, it also means that unconnected inputs can easily pick up electrical noise and rapidly change between high and low states in an unpredictable way. This is likely to make the IC behave erratically and it will significantly increase the supply current. To prevent problems all unused inputs MUST be connected to the supply (either +Vs or 0V), this applies even if that part of the IC is not being used in the circuit! Note that 74HC inputs cannot be reliably driven by 74LS outputs because the voltage ranges used for logic 0 are not quite compatible. For reliability use 74HCT if the system includes some 74LS ICs.Outputs can sink and source about 4mA if you wish to maintain the correct output voltage to drive logic inputs, but if there is no need to drive any inputs the maximum current is about 20mA. To switch larger currents you can connect a transistor.Fan-out: one output can drive many inputs (50+), except 74LS inputs because these require a higher current and only 10 can be driven.Gate propagation time: about 10ns for a signal to travel through a gate.Frequency: up to 25MHz.Power consumption (of the IC itself) is very low, a few µW. It is much greater at high frequencies, a few mW at 1MHz for example.74LS family TTL characteristics: Supply: 5V ±0.25V, it must be very smooth, a regulated supply is best. In addition to the normal supply smoothing, a 0.1µF capacitor should be connected across the supply near the IC to remove the 'spikes' generated as it switches state, one capacitor is needed for every 4 ICs.Inputs 'float' high to logic 1 if unconnected, but do not rely on this in a permanent (soldered) circuit because the inputs may pick up electrical noise. 1mA must be drawn out to hold inputs at logic 0. In a permanent circuit it is wise to connect any unused inputs to +Vs to ensure good immunity to noise.Outputs can <A href="http://www.kpsec.freeuk.com/components/ic.htm#sinksource">sink up to 16mA (enough to light an LED), but they can source only about 2mA. To switch larger currents you can connect a transistor.Fan-out: one output can drive up to 10 74LS inputs, but many more 74HCT inputs.Gate propagation time: about 10ns for a signal to travel through a gate.Frequency: up to about 35MHz (under the right conditions).Power consumption (of the IC itself) is a few mW.Regards, Janis Quote Link to comment Share on other sites More sharing options...
monokinetic Posted January 31, 2011 Report Share Posted January 31, 2011 Hi Tom, I found this page a few years ago. It's by a guy who built a MBFM: http://web.t-online.hu/gyurek/midibox.htm#oscillator I have not used it myself, but the schematic seems simple to try. David Quote Link to comment Share on other sites More sharing options...
tomcody Posted January 31, 2011 Author Report Share Posted January 31, 2011 wow monokinetic! thanks that's a good page, I will try that circuit and follow the Janis1279's indications and post the result, if doesn't work I will follow the nILS's indications and hope for the good will of an midiboxer :D . Thank you everybody. TomCody Quote Link to comment Share on other sites More sharing options...
michael82 Posted October 18, 2012 Report Share Posted October 18, 2012 Here's a complete list to be able to know the maximum frequency of your crystal oscillator http://www.ndk.com/en/products/search/fcxo/index.html Hope this helps you Quote Link to comment Share on other sites More sharing options...
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