Hi,
Its not the speaker thats at risk, its the Arduino. The 40ma limit is the most that a pin will safely output, it will output more if you let it, but it will die in the process. It will look like your getting away with it, but you are not, your damaging your chip and at some point the output pin will stop working.
I am not sure that the 318 op amp is a solution, its more of a voltage amplifier than an current amplifier.
If you don't have an LM386, you can try a simple resistor and capacitor network to send the output to an mp3 player or anything else with an Aux input - the circuit is shown in the Illutron B link above.
DuaneB:
Hi,
Its not the speaker thats at risk, its the Arduino. The 40ma limit is the most that a pin will safely output, it will output more if you let it, but it will die in the process. It will look like your getting away with it, but you are not, your damaging your chip and at some point the output pin will stop working.Are you sure about that? Thats not how I understand it . The USB port sets the current to the arduino at a set amount. (200mA? not sure atm). I thought each pin could not supply or sink any more than 40mAs ?
I am not sure that the 318 op amp is a solution, its more of a voltage amplifier than an current amplifier. Yes, but it was all I had and it did not work. Just something to try as I won't get the right one for a week.
If you don't have an LM386, you can try a simple resistor and capacitor network to send the output to an mp3 player or anything else with an Aux input - the circuit is shown in the Illutron B link above.I tried this to a 100 ohm resistor but it just reduced it more . With a 16 ohm impedence speaker it would take 300mA at most at this voltage (3.3V), the 100 ohm resistance droped this again
Duane B
Just a quick squiz at the datasheet for my ATMega328 and I have the (p) model which is low power I think
Electrical characteristics
29.1
Absolute maximum ratings*
Operating temperature................................... -55°C to +125°C
*NOTICE:
Storage temperature...................................... -65°C to +150°C
Voltage on any pin except RESET
with respect to ground .................................-0.5V to VCC+0.5V
Voltage on RESET with respect to ground ......-0.5V to +13.0V
Stresses beyond those listed under “Absolute
Maximum Ratings” may cause permanent dam-
age to the device. This is a stress rating only and
functional operation of the device at these or
other conditions beyond those indicated in the
operational sections of this specification is not
implied. Exposure to absolute maximum rating
conditions for extended periods may affect
device reliability.
Maximum operating voltage.............................................. 6.0V
DC current per I/O pin.................................................. 40.0mA
DC current VCC and GND pins ..................................
So if anybody knows for sure please jump in . It stands to reason that perhaps certain chips can push more than 40mA's but I would like to know for sure.
A resistor is the only way to be sure that the current will not exceed the pins current rating. The USB power supply might allow higher currents for a short period of time such as bursts. There is no way to know what is possible without careful testing. It is easier to and cheaper to provide your own protection like the resistor.
I use the amp circuit so that I can power a PC Speaker directly from the Arduino without needing an MP3 dock or anything else.
I have used the simple Resistor/Capacitor circuit in the link below (from digital pin 6 to the Audio out jack) to output sound without amplification - for example to send sound output from the Arduino into the aux input of an MP3 dock or similar equipment.
I am far from expert though so others might have better suggestions -
Hi,
The way the delay switch on/off is implemented is ugly - everyone has buttons, not everyone has a switch so I wrote the code as a very simple button/toggle switch.
To force delay, replace this section of code
// if the delay button is pressed, toggle delay
if(0 == digitalRead(DELAY_BUTTON))
{
bDelay = !bDelay;
// keeping it simple,
delay(500);
}
with
bDelay = true;
I will change the delay toggling code for something less ugly some day soon.
I've compiled both scketches, the one with LDR sensor is working, the other not. I've attached a button to digital pin 4, but i can't hear the delay....
now I want to retry your scketch with an arduino duemilanove, instead of an arduino mega...
Hi,
The way the delay switch on/off is implemented is ugly - everyone has buttons, not everyone has a switch so I wrote the code as a very simple button/toggle switch.
To force delay, replace this section of code
Code:
// if the delay button is pressed, toggle delay
if(0 == digitalRead(DELAY_BUTTON))
{
bDelay = !bDelay;
// keeping it simple,
delay(500);
}
with
Code:
bDelay = true;
I have a doubt....
I must change all the section that you indicate with
bDelay = true;
or just this part
bDelay = !bDelay;
thx for helping me Duane sorry for my dumb questions...
want to show me how I can merge this two scketches now????
I'm tryng to build even the LM386-N4 circuit amp, but I can't figure out how to power the IC... in the schematics you say its better to separate the power...
but how could do this? For my Auduino I use an arduino mega powered via usb.... I prefer not to use a battery... have you some advice for this?
Its a stupid idea try to power the circuit with the arduino mega??
I don't know why but the volume pot doesnt seems to work in the right way... is like a switch, you have to turn it until he reach a sort of treshold.... after that limit the volume start to pump...
The pot is on the input side, its there to adjust the level of the input signal, not the output volume.
You do not hear much difference with square waves but with a sine wave you can hear the amp get overdriven as you adjust the input level, it can add an extra bit of colour to the sound.
Do you want volume ? I usually find the default volume is about right.
I've notice a sort of colored sound.... yes the volume works good but iI would like to have less noise signal.... before solder all together I liked the filter "cut off"...
have you find a solution for the delay??? I would like to help you but I'm very bad in coding
Hi,
Very simple update to the code is now in place here -
It assumes a toggle switch is connected between the DELAY_BUTTON pin and ground and that a 10K pull up resistor is connected from 5V to the DELAY_BUTTON pin - your typical button with a pull up circuit except we are using a toggle switch inplace of a button.
I am making slow progress with a ribbon synth that uses and adaptation of the Auduino synth engine, hope to be able to post something soon.