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I am having a problem with Pierce oscillator designed to work with my SMART Card reader. I am using 3.58MHz oscillator, 74HCU04 gate IC for the NOT gate, and both 22pF capacitor and 1Mohm resistor. I was unable to get any clock pulse.

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  • \$\begingroup\$ Measure the voltage with a multimeter from output of NOT gate to ground - it should be around one-half Vdd (+5v) - that's WITH the 1Mohm resistor from output to input. Also, add a 0.1uf capacitor from 74HCU04 Vdd (pin 14) to gnd (pin 7). \$\endgroup\$ – glen_geek Nov 28 '16 at 15:39
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The Pierce oscillator requires two capacitors! See this circuit.

The capacitor values depend on the crystal load capacitance; they are effectively in series so you need roughly twice the value of the load capacitance. You need to allow for stray capacitance.

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  • \$\begingroup\$ Thanks. I actually tried it with the 2 capacitors, but still didn't get anything. How can i get the crystal load capacitance? \$\endgroup\$ – Paul A. Mar 28 '11 at 17:08
  • \$\begingroup\$ It'll be in the crystal specification. It should work with two 22pF capacitors, although the frequency might be slightly out. Check your soldering. \$\endgroup\$ – Leon Heller Mar 28 '11 at 17:54
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Aren't you missing one capacitor? Also, you should separate the oscillator from other circuits by another inverter, otherwise you may be overloading it.

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  • \$\begingroup\$ Thanks. I actually used two capacitors in my schematic, and also another inverter at the output, but still that dint work! \$\endgroup\$ – Paul A. Mar 28 '11 at 17:09

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