Hello,
I'm working on a project that has two speakers (6V, 13W) in the Arduino and they make a bunch of noises just using the tone() function.
Everything would be powered from a converter plug in the wall...
I was recently told that if I do this, eventually the pins are going to get worn out on the Arduino and that I should drive the
speakers through an LM386 IC. Would they also need a separate power source?
I'm having a hard time finding any tutorials on how to do this...is it necessary? If I use some 100ohm (or around there) resistors, will the pins be
fine?
If I do need the LM386...does anyone know some decent tutorials on how to wire this up?
Thanks!
(6V, 13W)
Unusual spec for a speaker - are you sure about that?
yeah...i thought it was weird, too. it says on the back of the speaker 6(with the little omega sign)13W
I've been using it with just a 100ohm resistor and it works fine...
but will it destroy the arduino eventually?
thanks for any help
6(with the little omega sign)
The commonly accepted symbol for "ohm"?
i guess...is that normal?
on the back it says 6(omegasign) 13W
below that: 5L24V
24 volt then?
24 volt then
?
What does Ohm's Law tell you about 5V and 106 ohms?
i'm sorry...i'm really terrible with this stuff...still just learning it.
but ohm's law is that the current is the voltage divided by resistance? so in this case i=.226? what do i do with that?
do i need to drive these speakers with an LM386 or can they work just with an arduino? how do i figure that out?
thanks so much for your help
i=.226?
Can you show your working to see how you got to that figure?
(Absolute maximum on an AVR pin is 0.04 A)
Measure the speaker with a multimeter - should show aroubd 6 ohms.
To keep from burning up you arduino, you don't want more than 25-30mA going out, 40 worst case.
So 5V/25mA = 200 ohm total resistance. See if that's loud enough for you. If not, you need an amplifier.
You could also make a simple single transistor amplifier like this.
Use any decent logic level N-channel MOSFET as this one seemed to have dropped off the face of the earth since I bought some last fall.
The speaker is still available, has nice sound.
http://www.mpja.com/prodinfo.asp?number=14618+SP $1.49
To protect your arduino output pins I wouldn't go below 160ohms of resistance for the series resistors to the speakers. The problem is that will protect the pin, but may not provide enough volume for your requirements. A lot depends on the efficiency spec for your speakers. That's why the recommendation to use a audio amplifier.
Now the simplest solution I can think of is to find a pair of small amplified PC speakers. I've seen them in thrift stores for $5 and they come with their own AC power module. You will need to find a mating 3 terminal audio plug for the line in jack for the speakers. Then make the connection to the Arduino on the ground terminal and either just one channel or two channel audio wired to arduino output pins, depending on if you are outputting one or two tones. You will not require series resistors as the line in is high impedance (>20k ohms). You will also gain a nice volume control in the set-up.
Even new, this is a pretty cheap audio solution: Cyber Acoustics CA-2002 2.0 2 Piece Amplified Computer Speaker System - Newegg.com
thanks so much for your help. ok i think i understand more or less now....i'm going to set up that circuit and see if i can't get it to work 
thanks!