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Topic: Acceptable speaker impendance (Read 957 times) previous topic - next topic

turbine495

Hello all,
I have a question about the acceptable impendance of a regular speaker (not piezo)
I own an Arduino Uno, and I recently obtained a 1" 16 ohm speaker from an old computer.
Is this an acceptable impendance (not too much current, etc ?).
Thanks in advance.

Peter_n

You need a 100 ohm resistor in series with the speaker.

DVDdoug

#2
Apr 01, 2014, 08:32 pm Last Edit: Apr 01, 2014, 08:36 pm by DVDdoug Reason: 1
An Arduino output puts-out 5V (when on/high) at 40mA or less.

Using Ohm's Law we can calculate the minimum allowable resistance (for the maximum 40mA current):  5V/0.040A = 125 Ohms.

So that's a minimum resistor value of 109 Ohms.

Note that most of the energy will be wasted in the resistor so you may not get enough volume.


P.S.
5V/16 Ohms = 313mA.    If you were to connect the 16 Ohm speaker directly, you'd probably get less than 5V out, so the current would be less than calculated but the Arduino might overheat and die!

turbine495

Thank you very much! I actually do not have a 100 ohm resistor, so I just used a 500 ohm one. Hope it is audible.

turbine495

I actually just hooked up a transistor's base to the IO pin and attached the collector and emitter to the speaker to 5v and GND. It is way louder now - too loud for my parents! 8)

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