Can I directly connect 8ohm 3W speaker in Arduino Uno?
Adapters input voltage: 5V - 12V
Adapters amp : 500mA - 2A
thank you for your help
Well lets say it is an 8 ohm speaker, How much current will 8 ohms draw at 5V?
.625 amps, now how much current can your MCU handle on a GPIO pin?
.040 Amps.
.625>.040, so what is the answer?
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No. Use an audio amplifier, with a separate power supply.
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You need an amplifier or some kind of driver circuit. You can build-or buy a little amplifier board (or you can use a more powerful amplifier).
...You can "get away" with a driver circuit because the Arduino doesn't put-out analog anyway, but an amplifier usually has a volume control and it's made to drive a speaker.
You can also put a resistor (about 120 Ohms) in series with the speaker, but most of the voltage will be dropped across the resistor and it will be very quiet.
The "absolute maximum" current from an I/O pin is 40mA with 20mA the recommended maximum.
Ohm's Law defines the relationship between voltage, resistance, and current as:
Current = Voltage / Resistance. That means the minimum resistance (or impedance) is 125 Ohms. (Resistance is "the resistance to current flow".)
If you hook-up the 8-Ohm speaker you won't really get 625mA because the chip can't put-out that much. The voltage is going to drop and the Arduino will overheat. (I'm not sure how much voltage & current you'd get, but you'd be over-stressing the ship.)
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Yes You can but the output of the Uno will be badly overloaded and might get burned down.
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