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31  Using Arduino / General Electronics / Re: Audio out and speaker on: October 28, 2012, 12:11:47 pm
Oh... so when I connect the line out the speaker gets automatically disconnected? That is awesome.
And R9 is the volume, right?

32  Using Arduino / General Electronics / Audio out and speaker on: October 27, 2012, 03:38:49 pm
I am working on some sort of synth and want to add a speaker output but also a line out, and if I am using line out the speaker should be deactivated.
I was thinking that I can use this amplifier: and have a switch on the OUT after the Master volume so it can switch between speaker and line out
Will that work ok? with no noise or problem at all?
33  Using Arduino / General Electronics / Re: Weird led behavior? on: October 22, 2012, 04:28:53 pm
Thanks for answering!
yes I did it like the picture, now I see what you mean, as the leds were not polarized (I mean they turned on on whatever orientation) once one shift register output becomes high it will get trough the led and as the other outputs of the SR are on low it will make the other leds turn on (on inversed polarity)... so that is what happened.

Now that I changed the leds to polarized ones it works perfect!
34  Using Arduino / General Electronics / Weird led behavior? on: October 21, 2012, 10:00:59 am
I have made a PCB for the circuit I have attached. Those 12 leds on the left are sharing one resistor because only one of them will turn on at a given time, on those leds I put some I had stored, they don't seem to have a cathode and annode, the orientation work the same and the 2 legs are equally length. What they did is some of the voltage seems that was going trough the leds into GND.
I really don't know a lot of ellectronics so really can't explain it very well, but when connecting the PIN13 of arduino to the GND terminal of the leds, if one of them was turned on, I could get a "1", and so some of the other leds got turned on as well. After replacing those leds with normal ones it did work as intended.

Could someone explain why I got a "1" on the GND terminal after the leds? Of course if I connected PIN13 after that shared resistance I got a "0".
35  Using Arduino / General Electronics / Re: Help with drum machine schematic on: October 16, 2012, 08:24:26 pm
oh, so can I take the 5V from the arduino board and maybe put a resistor somewhere in there in order to get the voltage down to 4,5V... or something like that?  smiley-razz
Sorry, I am a begginer about circuits.
36  Using Arduino / General Electronics / Re: Soldering leads to arduino to finish up? on: October 16, 2012, 12:29:24 pm
I get strips of male pin headers.  You can get long strips and snap off sets of the desired size.  I then plug the male pins into the female sockets on the Arduino board and solder to the part of the pin that would normally be soldered into a circuit board

Sorry, I don't understand you mean a pin header like this, right?
How do you solder that to the inside of the Arduino female pin? it has plastic all around!
37  Using Arduino / General Electronics / Help with drum machine schematic on: October 16, 2012, 12:21:13 pm
Hi, I saw this webpage which has the circuit for a drum machine explained:

I was wondering, once I do the circuit for a "snare drum" (SD) for example, where should the Arduino output pin be connected? To the termination where it says SD maybe?
And what type of output should it use? Just sending a digital "1" on the Arduino pin to the snare circuit make it sound?

38  Using Arduino / LEDs and Multiplexing / CD4051 Multiplexor input test sketch on: October 13, 2012, 07:07:11 pm
I made a little sketch to test my MUX shield and thought it may be useful to someone else
It's for testing INPUT potentiometers

Sorry for spanish comments, but you just need to copy, paste and change multSelPins[] to the inputs (S0,S1,S2) of the MUX and muxPin to the Pin of "COM OUT/IN" (Pin 3 of IC)

//change multSelPins[] to the inputs (S0,S1,S2) of the MUX and muxPin to the Pin of "COM OUT/IN" (Pin 3 of IC)

const int multSelPins[]={2,3,4}; //selectores del multiplex (S2,S1,S0);
const int muxPin=A5; //salida del mux

void setup() {
  pinMode (muxPin,INPUT);
  for(int x=0;x<3;x++){

void loop() {
  int channel[]={0,0,0};
  int value=analogRead(muxPin);
  int channel1[]={0,0,1};
  int channel2[]={0,1,0};
  int channel3[]={0,1,1};
  int channel4[]={1,0,0};
  int channel5[]={1,0,1};
  int channel6[]={1,1,0};
  int channel7[]={1,1,1};

void multSelectInputFun(int inputSel[]){
  //Serial.print("multInput :");
  for (int x=0;x<3;x++){
    //digitalWriteFast2(multSelPins[x],0); //prueba
    digitalWrite(multSelPins[x],inputSel[x]); //escribe el selector del multiplex con el valor que le pasamos
39  Using Arduino / General Electronics / Re: Aproaching definitive PCB on: September 23, 2012, 05:21:26 pm
In the board image you can see that I made some lines above and under the board to guide both layers, maybe as you say, doing something like that on four corners it's better, I'll try that.
Another thing that made the layers to dis-align was the paper (I used magazine paper), it wrinkled and made it more difficult I think.
I should try with photo paper.
40  Using Arduino / General Electronics / Re: Aproaching definitive PCB on: September 22, 2012, 05:52:00 pm
I thought about that, there are 2 inconveniences.

1) I live in Argentina so I would have to wait like 2 months for it to get to me.
2) I may have some errors on the design so everything will be wasted if I can't correct them. That's why I wanted to make this by myself first, in order to test it.

I may try consulting some prices with China companies, the shipping to here is cheaper from China.

Also, by ordering one alone I think the price will be high, right?
41  Using Arduino / General Electronics / Aproaching definitive PCB on: September 22, 2012, 05:19:06 pm
First of all it's the first time I am doing a complex project with Arduino and also with any electronics.

For the past months I have been working on some sort of synth with an AY-3-8910 chip.
I have finished with almost all of the Arduino programing and did a schematic with Eagle for taking the next step, creating a PCB and soldering the components for a definitive installation.
From the attached image you can see that the circuit is somewhat complex and after designing the actual board (2nd image) everything fits in a 12x12 cms square (4.8x4.8 inches)

Now, using Eagle autorouter it's imposible to do all the connections on a single layer, so I have to use two (up and bottom). That increments the difficult of printing and etching.

I tried printing both layers with the toner method (using a magazine paper) but I failed because I couldn't align both layers correctly, I think it's because it was difficult to do with magazine paper. After doing the holes with a manual drill and a 1mm drill bit I noticed that the component holes where off from the actual printed place.

What would you recommend me to do? Should I try again with photographic paper? Do you think it would be better separate it to different single layer modules and connecting them with cables?

What do you think?

42  Using Arduino / General Electronics / Re: Button with led (how to connect?) on: September 06, 2012, 09:43:08 pm
yes, that was my question.
by biased you mean that the led should be spin in order to let the current go to GND?
43  Using Arduino / General Electronics / Re: Button with led (how to connect?) on: September 05, 2012, 05:01:06 pm
ok, perfect!
but there is something I don't understand, without the 10K Resistor why the current doesn't goes to GND, even if it has a Resistor it's the only way, right?
44  Using Arduino / General Electronics / Re: Button with led (how to connect?) on: September 05, 2012, 04:35:55 pm
let me see if I understood, by putting a small resistor on the INPUT PIN you will force the current trough there when the button is not pressed? I am not sure I got that right.

you mean exactly like the attached picture?
45  Using Arduino / General Electronics / Re: Button with led (how to connect?) on: September 05, 2012, 03:48:22 pm
wait... retrolefty is right, when button is not pressed the output is floating, a solution anyone?
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