Which resistor with Piezo speaker

Using Arduino Motors, Mechanics, Power and CNC
1

Hello!

I'm beginner and I don't know which resistor can I use for Piezo speaker. At Tone tutorial is written to use 100 ohm resistor with speaker, but I don't have it because I've bought this starter kit. Which resistor in this kit can I use instead of 100 ohm ?

Thanks! :slight_smile:

2

Looks like there are some 220-ohm resistors in that kit, one of those should work fine. Might not be quite as loud is all.

3

You don't need to use a resistor with a piezo, according to what I've found by searching the net. I've been using my piezo without a resistor with no problems. If you have a potentiometer, you could use it to vary the volume though.

Here's a link to an old thread:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1265926572

4

What about Tone2 tutorial, where I need 4.7K resistor - Can I use 10K instead?

Thanks! :slight_smile:

5

You need to do some basic reading about resistors so's you understand what they are and how you can use them in combination.

For 100 ohm you could have used 2 x 220 in parallel and ended upo with 110 - near enough for your needs. For 4k7 you could use 2 x 10k in parallel to end up with 5k - again near enough for your needs.

6

jackrae is spot on. OTOH, the resistor values in either tutorial aren't terribly critical, so experiment. Try a 10K instead of 4.7K, then try two 10Ks in parallel and observe the difference in the circuit behavior. Piezo transducers are primarily a capacitive load, and so can draw large current spikes for brief intervals every time the pin toggles. The 100? resistor is to limit this inrush current so as not to exceed the limits of the microcontroller. A lot of people drive piezos without a resistor, I've done this a fair amount and no smoke yet, but using the resistor is definitely the conservative approach which will treat the MCU more gently.

7

Thanks for help!

Can you please link me a good book / article / tutorial or something, because it's real that I don't know anything about resistors. I've bought Arduino for hobby and I know some small basics about electricity, but that's all. I actually don't know where to start searching for those things because I don't want to get bad basics from newbie tutorials.