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61  Using Arduino / General Electronics / Reliable digital Pot for audio on: January 25, 2013, 09:43:55 pm
So a while back I wanted to automate a guitar pedal with 5 pots. I was told that an actual digital pot chip is too noisy for an audio circuit. Also using optoisolation was really difficult, I never got it working right. I ended up giving up.

Has anyone done this? Is there a well documented way of doing it?

62  Using Arduino / Project Guidance / Re: Help a newbie with an important decision! on: January 25, 2013, 09:39:39 pm
Also with the uno you can take the atmega out rather than dedicating your entire arduino board to a project.
63  Using Arduino / Project Guidance / Re: 328 3v 8mhz boot loader on: January 25, 2013, 09:32:13 pm
Ok I figured it out. I had two main problems. First, the tinyusbavr was supposed to be powering the arduino while it programmed but I guess it wasn't doing it right (maybe something about the other 5v pins on the chip). I switched it to no power and powered the arduino with USB and it bootloaded fine. Then to program it I had to take it out of the arduino and stick the 8Mhz crystal on a breadboard, it wouldn't program with the 16Mhz chip in the arduino.
64  Using Arduino / Project Guidance / Re: 328 3v 8mhz boot loader on: January 25, 2013, 12:48:49 am
I am trying to bootload the pro mini 8Mhz board onto my 328 with a tinyusbavr but I get this error:

avrdude: verification error, first mismatch at byte 0x7980
         0x21 != 0x88
avrdude: verification error; content mismatch

I have no problems burning the regular UNO bootloader. I tried doing it on the arduino board and on a breadboard with different combos of 3/5v and 8Mhz crystal.

Any advice?

65  Using Arduino / Project Guidance / Re: How to get power supply from Car on: January 22, 2013, 04:44:44 am
There should be a battery wire for the stereo, just splice into that. Sometimes it's also called the memory wire because it's always on, keeping the volatile memory working.
66  Using Arduino / Project Guidance / 328 3v 8mhz boot loader on: January 22, 2013, 04:42:41 am
I wish to use the atmega328 at 3v but still with ok timing. I have some 8mhz crystals, would the arduino pro mini boot loader work fine for this or is there a better boot loader for this scenario?

67  Community / Bar Sport / Re: YSD-998 6500mAh battery... on: January 19, 2013, 06:00:22 pm
Well, like I said, I didn't expect much. The real disappointment wasn't even the capacity.
68  Community / Bar Sport / YSD-998 6500mAh battery... on: January 17, 2013, 09:14:19 pm
So I got one of these "6500 mAh" batteries off of ebay. I didn't expect much and it's still a bit of a let down. After testing it a few times, the best capacity I got out of it was 3500mAh at 12v. I haven't tested the other voltages yet, I'm not sure I'll bother. I also attached a graph of the voltage over time for my test.

I can't really say how accurate the test is. I used 15 100ohm resistors, each 5 in parallel and those groups in series. I measured just about exactly 60ohms with my crappy multimeter. Then I connected an analog input of my arduino between group 2 and 3 to divide the voltage by 3, giving me a range of 0-4 volts for the arduino to measure. The arduino took a reading every second, and averaged every ten readings to record to an SD card every 10 seconds. I verified my calculations were correct with a multimeter before starting the tests. Voltage wasn't perfect but it was easily within 5% and even better when i tweaked the math a little...

So even though it only delivers just over half of it's claimed capacity, my main problem with it is the charging. It takes between 24 and 30 hours to get it fully charged. It took about a week before I realized it actually has a full charge indicator because I had never seen it. The charger has two lights, one indicates power to the charger, the other indicated that it is delivering power to a device. On the device itself there is a red light that seems to turn green when it is sufficiently drained and also snaps green for a moment when you turn it off, seemed like a weird system to me and unfortunately the seller was no help.

This is the exact one I got, I figure they're all different so maybe if you want to try one of these, don't try this one.
69  Using Arduino / Project Guidance / Re: How do you make the current draw from a device gradual instead of instant? on: January 11, 2013, 06:22:19 pm
What exactly is your goal? There may be a more clever way of accomplishing it if there was more information.
70  Using Arduino / Project Guidance / Re: LED strip light fade on: January 09, 2013, 06:41:59 pm
I feel like maybe that the perceived brightness of daytime would be similar to the perceived brightness of an LED, especially taking in a persons adjustment to brightness over the day. It might actually be a desired effect...

And if not it's quite simple to fix, but causes some ugliness in the lower numbers.
71  Using Arduino / Storage / SD card lib, seek to last line on: January 09, 2013, 02:30:23 am
Is it possible to seek to the last line of a file without having to read it all into memory? I want to be able to "pick up where I left off" in terms of number being played with but my file will be way too big to read through the whole thing.

72  Using Arduino / Project Guidance / Re: Battery Type on: January 08, 2013, 03:53:06 pm
I just got one of these. It's a gamble, I hear sometimes they bloat up or catch fire. But mine seems find so far except that I can't figure out how the indicator lights work.
73  Using Arduino / Project Guidance / Re: Sending Audio Data over WIFI? on: January 08, 2013, 12:04:27 am
Is this Roland pickup a midi device? If so you should not have any trouble interfacing with it.

If you are considering doing anything with actual analog audio, forget about it, the arduino can't handle it... Unless you want very basic info from it, certainly not transmitting it.
74  Using Arduino / Storage / Re: Ethernet shield SD card initialization failed on: January 07, 2013, 08:46:40 pm
But on the shield they are supposed to be independent. What I'm saying is, I can't even get the SD card to work when I completely ignore the Ethernet stuff. I have no problem with the Ethernet stuff. And I am aware that there is some conflict when using both. But I am running code as if it were just the SD card and it doesn't work.

For instance the cardinfo sketch:
  SD card test
 This example shows how use the utility libraries on which the'
 SD library is based in order to get info about your SD card.
 Very useful for testing a card when you're not sure whether its working or not.
 The circuit:
  * SD card attached to SPI bus as follows:
 ** MOSI - pin 11 on Arduino Uno/Duemilanove/Diecimila
 ** MISO - pin 12 on Arduino Uno/Duemilanove/Diecimila
 ** CLK - pin 13 on Arduino Uno/Duemilanove/Diecimila
 ** CS - depends on your SD card shield or module.
  Pin 4 used here for consistency with other Arduino examples

 created  28 Mar 2011
 by Limor Fried
 modified 9 Apr 2012
 by Tom Igoe
 // include the SD library:
#include <SD.h>

// set up variables using the SD utility library functions:
Sd2Card card;
SdVolume volume;
SdFile root;

// change this to match your SD shield or module;
// Arduino Ethernet shield: pin 4
// Adafruit SD shields and modules: pin 10
// Sparkfun SD shield: pin 8
const int chipSelect = 4;   

void setup()
 // Open serial communications and wait for port to open:
   while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only

  Serial.print("\nInitializing SD card...");
  // On the Ethernet Shield, CS is pin 4. It's set as an output by default.
  // Note that even if it's not used as the CS pin, the hardware SS pin
  // (10 on most Arduino boards, 53 on the Mega) must be left as an output
  // or the SD library functions will not work.
  pinMode(10, OUTPUT);     // change this to 53 on a mega

  // we'll use the initialization code from the utility libraries
  // since we're just testing if the card is working!
  if (!card.init(SPI_HALF_SPEED, chipSelect)) {
    Serial.println("initialization failed. Things to check:");
    Serial.println("* is a card is inserted?");
    Serial.println("* Is your wiring correct?");
    Serial.println("* did you change the chipSelect pin to match your shield or module?");
  } else {
   Serial.println("Wiring is correct and a card is present.");

  // print the type of card
  Serial.print("\nCard type: ");
  switch(card.type()) {
    case SD_CARD_TYPE_SD1:
    case SD_CARD_TYPE_SD2:

  // Now we will try to open the 'volume'/'partition' - it should be FAT16 or FAT32
  if (!volume.init(card)) {
    Serial.println("Could not find FAT16/FAT32 partition.\nMake sure you've formatted the card");

  // print the type and size of the first FAT-type volume
  uint32_t volumesize;
  Serial.print("\nVolume type is FAT");
  Serial.println(volume.fatType(), DEC);
  volumesize = volume.blocksPerCluster();    // clusters are collections of blocks
  volumesize *= volume.clusterCount();       // we'll have a lot of clusters
  volumesize *= 512;                            // SD card blocks are always 512 bytes
  Serial.print("Volume size (bytes): ");
  Serial.print("Volume size (Kbytes): ");
  volumesize /= 1024;
  Serial.print("Volume size (Mbytes): ");
  volumesize /= 1024;

  Serial.println("\nFiles found on the card (name, date and size in bytes): ");
  // list all files in the card with date and size | LS_DATE | LS_SIZE);

void loop(void) {

Initializing SD card...initialization failed. Things to check:
* is a card is inserted?
* Is your wiring correct?
* did you change the chipSelect pin to match your shield or module?

I've tried all of the example sketches for the SD card and they all fail to initialize the card.
75  Using Arduino / Project Guidance / Re: complete novice, where to start, arduino aquarium controller on: January 03, 2013, 11:45:18 pm
Pretty much any digital reading from an aquarium except for temp is going to very expensive, just be prepared for that.
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