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T Chap
05-09-2008, 02:46 AM
I see buzzers running straight off the output pins all the time, but in a case where there are 3 buzzers on one pin is this a potential problem for the Prop?

I haven't ordered these yet to test, but to run three off one pin in parallel [must be parallel], would a transistor be best to drive them?

It shows 4.0 min operating voltage below on the data sheet for a buzzer I found off digikey.

Part No: CCG-1206
Magnetic Buzzer
Rated voltage 5 Vo-p
Operating voltage 4.0 - 8.0 Vo-p
Mean current 50 mA max. Applying rated voltage, 2400 Hz square wave, duty
Coil resistance 40 6 Ω
Rated frequency 2,400 Hz

The data sheet shows their method of testing using a transistor and 2.5v square wave input.

Thanks

Mike Green
05-09-2008, 03:53 AM
You need to read the datasheet for the Propeller. It gives the maximum current output of a Prop I/O pin as well as the maximum current for groups of pins and for the whole chip. The datasheet shows the maximum voltage supplied by an I/O pin when it's set to logic high. If an I/O pin can't supply enough voltage or enough current for your device, you have to provide some kind of external switching. If one buzzer draws too much current, three buzzers will draw three times too much current.

T Chap
05-09-2008, 04:22 AM
Thanks Mike

I just added a LM386 amp to the Prop, that way I have more than enough gain if needed, and not have to worry about damaging the Prop.