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Topic: Arduino pin to headphone jack (Read 1 time) previous topic - next topic


I have a mono 3.5 mm headphone jack and I want to solder wires on it to go to an Arduino pin for the Tone() function. I was wondering what ohm and wattage resistor I would need to bring down the volume to a good earbud volume. I also have a potentiometer so I would prefer a resistor to get me to maximum volume because I can greater turn down the volume afterwards. I don't know what amperage and voltage audio jacks usually put out.


What is the impedance of the earbud you are using?
You don't want the IO pin to see Less then 180 ohm so you don't overdrive the IO pin.
So your earbud plus a series resistor should measure 180 minimum, then your pot in series should add to that to lower the volume. 1/4 watt resistor & 1/4 watt potentiometer will be fine.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


Dec 02, 2016, 07:34 pm Last Edit: Dec 02, 2016, 08:01 pm by LarryD
Assuming earphone resistance is 8ohms.

The resistance between the Arduino O/P pin to GND should be: 5v/20ma=250ohms at a minimum.
270 1/4 watt is a standard value.
See image for circuit (a few minutes please).

'Increase' the value of R6 as needed for maximum volume.
No technical PMs.
The last thing you did is where you should start looking.


You should really have a capacitor in series as the speaker wants ac without a dc-offset.  Something like
100uF electrolytic would be suitable.
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Dec 02, 2016, 08:47 pm Last Edit: Dec 02, 2016, 08:47 pm by LarryD

No technical PMs.
The last thing you did is where you should start looking.

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