Hi I am new here. Can I use these speakers with my arduino uno .Each speakers are 8ohm 0.5W Will it destroy my arduino uno ???Can anyone give some tips how can i use it with out sd card module??
You need an amp. Max output on most Arduino devices is 20mA, or .1W @ 5v.
Currently I don't have amplifier. Can I use it with out amplifier ? If I put the pin 3 of arduino uno on Positive of the audio jack and GND of the arduino uno to the GND of the audio jack will it destroy my arduino uno by taking more current ?
No, you don't want to do that. What would be the purpose? All you would hear would be the click-click as the pin went from 0 volts to 5 volts and back to zero volts, again.
Put a limiting resistor in series with the output.
Try a 1" piezo speaker instead of a conventional one. Or buy a set of POWERED speakers, they have an amp built in.
Order from WalMart HERE
And put a large capacitor in series with that as well to stop the DC component damaging the speaker.
A question: has anyone tried driving an 8 Ohm speaker connected to its impedance matching transformer from an Arduino?
What is the output impedance of your Arduino pin
?
You posted a picture of a voice coil speaker.
Description reads
# MCKP2644SP1F-4748 PIEZO, 400HZ, 86DB; Transducer
I've seen a lot of piezos.
Usually quite solid-looking metallic sounders.
I've also seen a lot of voice coil transducers.
Frequently with clear mylar diaphragms, and circular copper-coloured voice coils.
A lot like the one in the photo.
It is what it says. It works but the sound only comes out one side. Maybe the description is wrong. I agree it looks voice coil to me too, but it'll drive direct from a D pin with the tone() op.
As someone else mention you'll need an amp - probably not like you're thinking though. Check these from Adafruit:
Well, that would depend on what "its impedance matching transformer" actually is, but you definitely want a capacitor (say, 100 µF) in series and probably a 220 Ohm resistor also just in case. 
The volume will likely be quite adequate driving directly from the Arduino for the sort of purposes you are likely to want - beeps and boops. You are not going to be playing music or speech.
You know, Walmart doesn't directly sell stuff like that... It's a 3rd-party seller with a confusing description. It doesn't look like a piezo and piezos are not 8-Ohms. You have to buy from reliable electronics suppliers (Digikey, Mouser, Jameco, SparkFun, Adafruit, etc.). Also stay away from AliExpress or Amazon 3-rd party sellers, etc.
It will also step-down the voltage. A 20:1 step-down transformer would give you 1/20th of the voltage and since power is related to the square of the voltage, that's 1/400th of the wattage (compared to getting the full voltage into the speaker, which you can't get without an amplifier or driver circuit.)
...Vacuum tubes run from high voltage and have relatively high impedance so in the tube-days it was common to have an audio transformer between the tubes and the speaker.
I know that the vendors are Chinese knock offs, but i but from Walmart because if i have ANY problem one chat will get my $$$ back.
I do buy from mouser, Digi-Key, Jameco.com, McMaster for good stuff, again where i can get instant refund if there is a problem. I don’t think this is a QA issue, but more of a lack of docs issue. Im only out $15 if someone has a better idea.
I just need beeps. I thought of using a speaker & transformer salvaged from a small transistor radio and so not knowing the driving impedance. I wanted to check with others in case this is a bad idea. Thanks.
However an 8 Ohm speaker in series with a 220 Ohm resistor - as is necessary to protect the Arduino - will also receive 1/28th of the voltage so if you are using the capacitor, with a transformer you can reduce the resistor value to say, 100 Ohms and it will be more efficient.
This is referred to as "impedance matching."
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