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1  Using Arduino / Installation & Troubleshooting / Ongoing Arduino Uno & OSX Mavericks communication issue on: May 03, 2014, 07:32:21 pm
I was forced to upgrade to OSX Mavericks recently due to the death of my laptop. The replacement laptop came with Mavericks 10.9.2 installed.

I am experiencing the known issue involving Apple's FDTI drivers and can no longer upload code to any of the Arduino Uno boards I have. I have searched out solutions on the web but the ones I have tried ( and - basically disabling Apple's FDTI driver and installing the most recent drivers from FDTI - have not worked.

So far nothing has worked and my projects are completely stalled as a result. Short of switching from Arduino (or OSX), does anyone know of something else I can try? I am getting rather desperate.
2  Using Arduino / Project Guidance / Rigging an electronic switch for a salvaged Mac 8100 power supply on: October 17, 2012, 10:52:50 am
I salvaged a power supply out of my ancient Mac 8100. (it's an Apple 614 0012 200W Power Supply Power SMP 220DB 8100 Series).

At first I was baffled about how to turn it on but eventually came across the post below. With some trial and error I was able to identify the correct pins to trigger the relay (I guess) which turns the supply on and off.

My question: A momentary 5 volts is sufficient to turn the supply on so I am wondering what kind of switch I should use. Specifically, would a DTSP switch which applies continuous 5v power to the 'on' pin cause damage? Those switches are cheaper and easier to find than momentary DTSP switches. This is a nice project power supply and I don't want to burn it out through a silly mistake.


3  Using Arduino / Project Guidance / Re: suggestions for programming structure and storing of animatronic sequences on: September 20, 2012, 09:58:18 am
So for now I have decided to roll my own simple data format in order to keep the project moving (on another forum, someone had suggested using MIDI as a data format).. I was also concerned about storing cue data in a way that doesn't eat up RAM.

Since I am using an Ardunio Mega with 128 KB of Flash memory I want to use that before resorting to an SD card. With the excellent Flash Library ( accessing PROGMEM is very easy and I was able to rough out a test sketch in minutes.

For motor control I am using dedicated motor controller boards using serial comm. Each board controls two motors. For testing, the maximum data size I needed to send was four values: *rate, slope, x target, y target* in order to make a move so that determines my data format for motors.  This will change when I add a timestamp and board ID values.

With the Flash lib, you can define a FLASH_TABLE, store it in PROGMEM and then access it using simple array bracket access. Testing with a couple of thousand entries shows no issues.

So it becomes a simple task of pulling data out and sending it to the standalone boards or using it internally for my LEDs.

// simple example:

    #include <Flash.h>
    FLASH_TABLE(int, command_table, 4 /* width of table */,
        {111, 222, 333, 444},
        {1001, 900, 3210, -4567},
        {1002, 1000, 3210, -4567},
        {1003, 1100, 3210, -4567},
        {666, 777, 888, 999}
    void setup() {
        Serial.print("Mem: "); Serial.println(availableMemory());
        // Determine the size of the array
        Serial.print("Rows: "); Serial.println(command_table.rows());
        Serial.print("Cols: "); Serial.println(command_table.cols());
        Serial.print("RAM: "); Serial.println(sizeof(command_table));
    void loop() {
    int availableMemory()
      int size = 1024;
      byte *buf;
      while ((buf = (byte *) malloc(--size)) == NULL);
      return size;

4  Using Arduino / General Electronics / Re: Should I control the high power LED or its driver? on: September 18, 2012, 09:48:48 am
Thanks for the replies!

Good point about destabilizing the circuit - makes sense now that you point it out.
5  Using Arduino / General Electronics / Should I control the high power LED or its driver? on: September 18, 2012, 07:13:29 am
I have some older Luxeon high power LEDs and bought some drivers (spec below) to power them. They work fine for what I need.

However, I am going to be controlling these using TIP120 circuits (one to one) from an Arduino and it occurs to me that I don't know if I should be controlling power flow to the driver or to the lamp itself. I'll be doing both on/off and PWM.

Might sound like (and be..) a dumb question but when I stopped to think of it I wondered about which is least stressing on the hardware, delayed start and/or hysteresis. Is there a best practice or rule of thumb here?

6  Using Arduino / Project Guidance / suggestions for programming structure and storing of animatronic sequences on: September 16, 2012, 10:18:52 am
I'm working on some animatronics for an art installation which will use several stepper motors and some high-power LEDs. In the past when I have done this sort of thing I have used a tethered computer to handle the logic and timing. For this project I would like to try making it self-contained (e.g. just the Arduino board). For Arduino hardware, I have an Arduino Mega and could expand it with an SD card shield for more storage, if need be.

I'd really welcome any ideas or suggestions on how to approach this (and am not asking for code).

For the data, essentially I would be storing cues for each stepper and each LED. And of course I would need some kind of clock or timestamp to keep track of things.

A stepper cue would be something like:

 - cue start time
 - stepper ID
 - stepper direction
 - stepper speed
 - number of steps

An LED cue would be something like:

 - cue start time
 - Start brightness
 - End brightness
 - duration

So what I am wondering about:

 - ideas about a data format compact enough to store lots of cues
 - any suggestions for a clock or timestamp. (A simple counter is the obvious choice)

As for just how many cues/how much data, since I am just beginning this, I will work within whatever limits I bump up against.
7  Using Arduino / LEDs and Multiplexing / Threaded (non-blocking) RGB LED crossfade - examples? on: June 09, 2011, 08:47:36 pm
HI - I've seen lots of great examples for working with color fades on RGB LEDs but they all use a tight loop with a delay() controlling duration. I need to control a number of LEDs and have each of them transitioning concurrently. I'm looking at using the Penner easing functions as a starting point but I am wondering if this wheel has already been invented (threaded LED control on Arduino)?

I'm using ShiftBrites - so that adds a little.... complexity.

Cheers, and thanks for any tips.

8  Using Arduino / Project Guidance / Re: Driver board? on: June 03, 2011, 03:32:02 pm
How many LEDs? It looks like you said just one? If so you might check out the ShiftBrite ( They are easy to use and don't require other circuitry.
9  Using Arduino / LEDs and Multiplexing / Alternatives to the MAX 7219? on: June 03, 2011, 03:29:04 pm
Hi - I seem to recall mention of good/low cost LED driver chips that are similar to the Max 7219 but I can't find the thread in the forum. I've used the 7219 (through hole/DIP) chip a bunch and like it but for an upcoming project want to see what else is out there.

10  Using Arduino / Motors, Mechanics, and Power / Re: H-bridge (L298N DUAL FULL-BRIDGE DRIVER) gets very hot - help! on: June 03, 2011, 03:24:36 pm
Those Radio Shack ones look good but they may be an online only thing - have never seen them in the bins at a RS store.
11  Using Arduino / Project Guidance / Re: Making shield from perf board? on: May 21, 2011, 03:33:24 pm
Cool - thanks! Picture says it all.
12  Using Arduino / General Electronics / Re: When NOT to have a common ground? on: May 21, 2011, 11:19:22 am
Cool thanks ('s all fine until the smoke comes out ;-))
13  Using Arduino / Project Guidance / Re: Making shield from perf board? on: May 21, 2011, 10:44:57 am
Not able to picture that - are you using long legged pin headers?
14  Using Arduino / General Electronics / Re: When NOT to have a common ground? on: May 21, 2011, 10:25:32 am
Hmm... so with my TIP 120 transistor I am controlling a 20V fan. I have a common ground (between Arduino, TIP 120, 20V/3 amp power supply). Is this going to be a problem?
15  Using Arduino / Project Guidance / Re: Making shield from perf board? on: May 21, 2011, 10:17:25 am
Thanks! Looks like that is what I need.
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