I want to make some project and I don't have buzzer so I decided to replace it with headphones. Is it safe to use 32 ohm headphones. Should I place resistor, which value?. I have seen people use two alligator clips on headphones jack to connect headphones to breadboard. My initial thought is to use two paper clips for connection is it even possible?

The absolute maximum output current from an Arduino pin is 40mA, a 32 ohm load at 5V
would greatly exceed that... Basically you either use an audio amp chip, or add 150 ohm resistor
in series to limit the current to a safe level (it may then be too quiet).

Thank you. Can I ask how did you come with this value? 150ohm seems little.

The value is derived from the 40mA Absoloute maximum current from a pin. You want the load on a pin to draw less than this.

inmydreams:
Thank you. Can I ask how did you come with this value? 150ohm seems little.

The resistance is given by R = V/I.

Now V = 5 V and I 0.04 A maximum.

So R = 250 Ω minimum

Take away the 32 Ω you already have and you are left with 218 Ω. A 220 Ω resistor is probably OK as the output voltage on the pin will be slightly less than 5 V although it is not specifie in the data sheet. To be 100% safe you should also take into account the supply voltage tolerance and the resistor tolerance.

Russell.

Thank you, but why R=250ohm if r=5/0.04=125ohm. Have you multiplied it by 2?

inmydreams:
Thank you, but why R=250ohm if r=5/0.04=125ohm. Have you multiplied it by 2?

Sorry, I was thinking of halving the maximum current to give a safety margin but didn't follow through in the post.

Russell.

Ok thanks. Actually this is that I thought of to cause save operational current is suppose to be 20mA.

How did this project go? I've seen a similar headphones project in the past, but it did not turn out so well. Would be interesting to hear how yours went.

What worries me most is the suggestion of using paper clips to connect to the headphone plug.

That is virtually certain to cause a complete short circuit.