Thanks! On Tuesday, January 15, 2013 7:09:44 PM UTC+1, mikeselectricstuff wrote: > > On Tue, 15 Jan 2013 09:59:46 -0800 (PST), you wrote: > > >Also, is there any need to protect the controller pin from the voltage > >spikes? And what about current draw, should I put a resistor because of > the > >inductor, or can I expect small currents? > > No - the small high-value inductors have typically hundreds of ohms of > series resistance so no smoke > if the transistor turns on continuously > > the transistor base resistor won't pass enough current to damage the MCU. > > > >> Put a 10-100millihenry Inductor across piezo ( you can get some very > >> cheap axial ones), and drive > >> withan open collector transistor, Note that disconnecting the piezo > will > >> produce a high voltage > >> that may kill the transistor unless you use a HV transistor like > MPSA42,. > >> if the piezo is solidly > >> connected you can usually use a bog-standard NPN as the piezo will > limit > >> the voltage. > >> Also remember that piezos are sharply resonant so tweaking the > frequency > >> for loudest output makes a > >> big difference, regardless of how you drive them. > >> >
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