>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>On Behalf Of John Chung
>Sent: 02 April 2007 05:31
>To: Microcontroller discussion list - Public.
>Subject: [EE] Buzzer puzzle.
>
>
 I checked the current
>consumption during Q and it was draining about 32mA.
>
>Why do I need a resistor in
>series?

The PICs I/O pins have an absolute maximum rating of 25mA!

Also if this is a magnetic device then you will probably be getting some nasty current spikes when you switch it off which could cause problems with the PIC.  The resistor is limiting both the DC current and any transient currents when you set the port pin low.

If you want to use this device purely as a buzzer then I suggest that you put a resistor in to limit peak current and also AC couple it (i.e. put a capacitor in series) to prevent excessive current being drawn if the PIC's ouput remains high.  Connecting a diode accross the buzzer (cathode to PIC pin, anode to ground) will help suppress any spikes.

Regards

Mike

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