Thanks to all for your help. ----- Original Message ----- From: "Russell McMahon" To: Sent: Tuesday, August 17, 2004 2:47 AM Subject: Re: [PIC:]BUZZERS/SPEAKER > > > Can anyone recommend a piezo speaker/buzzer that I can > > > drive direct from a PIC I/O pin. I just need to get someones > > > attention if they walk away from a machine without > > > shuting it off. > > You will probably get more output from a small speaker type transducer than > a piezo if using a single pin. With two pins driven antiphase you get twice > the voltage (arguably 4 x the power). Small electromagnetic transducers > (like mini speakers) are available. > > For a one off or small volume you could consider using earpieces from the > ultra low cost in the ear headphones available everywhere. > A PIC pin is capable of a nominal 20 MA at 5V (this is actually somewhat > qualified) = 100 mW. This is about 2.5V RMS so ideal load impedance is about > V^2/Power = 6.25/0.1 =~ 60 ohms. A "speaker" with impedance in the 20 to 200 > ohm range would be a good starting point. > > You can also buy small self contained annunciators with a self contained > oscillator. These look after levels and impedance matching themselves and > are an easy solution - apply 5 volts and you're running. > RS 172-7627 (EuroInd EI-242-B) is one example but you'll be able to get > cheaper and/or better locally. > Similarly RS 172-7380 = Murata PKB24SPC-3601 > > > > RM > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body