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16  Using Arduino / General Electronics / Re: Basic maths: 10kΩ resistor, 5V voltage, 100µF cap=0.76 second LED fadeout on: August 20, 2013, 02:27:04 pm
Take a look at this page.

That was good, thanks. Stack Exchange is fantastic.

Have you had calculus yet?

LOL i admit my calculus is rubbish, after so many years since highschool. That's why i'm doing such basic math now, and also looking for peer support here. Thanks for it DVDdoug, i appreciate it! This is great exercise.

Now that the day is drawing to night, and it's getting darker, i can empirically see that the 0.76 seconds is too short a time for my LED's fadeout; it seems to be above 1 second.

A capacitor discharging through a resistor is an exponential function.  (Since the current is not constant, you cannot use C = I x t except for "one instance" in-time.)

That's right, it makes sense; the LED is fading, and that is exactly the reason why it's getting less and less bright; the current is dropping... and thus it's bleeding the charge in the cap slower and slower.

My amended calculation, assuming an exponential decay of current, is -10000Ω*0.0001F*ln(1.2V/5V)=1.43s. That seems to correlate better with sense-based observations. Next, maybe i should build a tool, using Arduino, a light-dependant-resistor and millis(), that would measure the time it takes for the LED to fade smiley-cool
17  Using Arduino / General Electronics / Basic maths: 10kΩ resistor, 5V voltage, 100µF cap=0.76 second LED fadeout on: August 20, 2013, 12:40:27 pm
As an exercise in basic EE and basic maths, i want to fade out a LED with a capasitor. I wonder if anybody could peer-review my calculations?



Given i am using a 10kΩ resistor and a standard LED in series, and in parellel with a 100µF cap, all in a 5V circuit, shouldn't my timeout be 0.76 seconds?

  • Mr. Ohm (V=IR), thus I=V/R
  • Mr. Kirchhoff (V=V1+V2), thus a 1.2V front voltage LED turns off at 5V=1.2V+VacrossCap=VacrossCap=3.8V.

Charge C = F*V
Charge C = I*t
Time t = F*V/I = 0.0001F*3.8V/(5V/10000Ω) = 0.76s

+=?
18  Using Arduino / Interfacing w/ Software on the Computer / Re: What does Android logcat say when connecting Arduino ADK (ie. an "accessory") on: July 21, 2013, 02:31:12 pm
Hi, i'm happy my monologue here has helped someone... well it's not a monologue since i feel i was talking to the future via Google and other search tools by publishing it smiley

Anyhow, my personal strategy has been to skip Android stuff for now, and concentrate on Arduino and electronics for the time being. Besides i ruined my Galaxy Nexus in a massive rain we had here in Helsinki, and haven't got a new Android device yet. Anyhow, what i did personally to
Quote
[...] and i can even confirm (using demo apps) that data is being passed between Arduino ADK and Android.
was by using the serial monitor with the AOA Android demo apps, and see stuff there when i was operating the demo app. I haven't built a working Android app that would work with Arduino over AOA, though i tried. I will come back to it at some later point in time.

Do you know how to build Android apps? That's a basic skill to learn, and then learn to use the USB Manager, and serial connection to push/receive data.
19  Using Arduino / Interfacing w/ Software on the Computer / Here is a simple example of sending data from Arduino to PureData over serial on: July 18, 2013, 02:41:39 am
Hi everyone, some time ago i made a simple exercise in sending data from an Arduino to PureData over serial, and i would like to share a video of it. The Arduino code is simply a 16-step step sequencer, like so:

Code:
int i = 0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  step = i % 16;
  Serial.write(step);
  i++;
  delay(200);
}

And you can see my PureData patch in the video. It uses the comport object to communicate with the Arduino, and the hslider object is limited to values between 0 and 15. You can find the video here on YouTube

20  Using Arduino / Project Guidance / Re: Arduino to Pure Data via serial - how to unpack data from accelerometer? on: June 09, 2013, 03:28:34 pm
This article about Pd messages seems relevant for your question. How are you sending the messages over from Arduino to Pd, are you using directly the code from the website you linked to?
21  Using Arduino / Installation & Troubleshooting / A fix for LilyPad USB on Ubuntu (or maybe GNU/Linux in general) on: March 11, 2013, 11:08:22 am
Hi. I just acquired an Arduino LilyPad USB today, and had trouble making it work on my GNU/Linux computer (i'm using, and loving Ubuntu). The problem was that Arduino IDE was telling me that it couldn't find a Leonardo device. I'm really sorry i haven't got the exact error message anymore, it would be great for people who search the forums. Sometimes i would get a message 'Serial port /dev/ttyACM0 not found' instead.

Anyways, after some headscratching and debugging, i found out that a component of the Ubuntu Network Manager called modemmanager was snatching the /dev/ttyACM0 device. I filed a bug report on Ubuntu Launchpad #1153632, made a bugfix, and submitted a merge request to Ubuntu.

<3

So it should be fixed for everyone who upgrades their Ubuntu eventually when 13.04 is out, or if this bugfix get's backported. Meanwhile, if you are using an Arduino LilyPad USB, create a file called /etc/udev/rules.d/70-arduino-lilypad-usb.rules with the following contents:

Code:
# Arduino LilyPad USB
ATTRS{idVendor}=="1b4f", ATTRS{idProduct}=="9207", ENV{ID_MM_DEVICE_IGNORE}="1"
ATTRS{idVendor}=="1b4f", ATTRS{idProduct}=="9208", ENV{ID_MM_DEVICE_IGNORE}="1"

And then run sudo service network-manager restart or restart your computer.

I hope this helps, and i hope people will find here via Google, and i also encourage you to see the Ubuntu Launchpad bugreport https://bugs.launchpad.net/ubuntu/+source/modemmanager/+bug/1153632
22  Using Arduino / Programming Questions / Strategies to use version control system (like Git, SVN, CSV) with Arduino on: March 10, 2013, 01:24:39 pm
Hi, i would like to discuss various strategies of version control you people are using when you are working with Arduino.

Personally, i'm used to using a version control system, nowadays use Git. My development platform is Ubuntu, and i intend to stick with the Arduino IDE. The Arduino IDE creates new subfolders under my ~/sketchbook, and it seems the most sensible idea to initialize a git repository for each of these directories. I don't know if Arduino IDE ever creates more than one file though...

+ =

I also would like to use some program to document the electronics for my Arduino projects. I just installed Fritzing since everyone seems to be using it. And i might be using other files as well, like photos and text. Unfortunately Fritzing uses a binary file format (a zipped XML), and these are a little unconvenient with version control systems.
23  Topics / E-Textiles and Craft / Re: Are we expecting a larger LilyPad USB? on: March 08, 2013, 02:28:50 am
Is the bit laying on the table a hood?

Haha no, but thanks for a good idea for an avenger cape! smiley-grin
24  Topics / E-Textiles and Craft / Re: Are we expecting a larger LilyPad USB? on: March 07, 2013, 06:41:18 am
Well, either way i just purchased a LilyPad USB smiley-wink Twinkle, twinkle little puppydog!

25  Topics / E-Textiles and Craft / Are we expecting a larger LilyPad USB? on: March 07, 2013, 04:31:25 am
Hi. Looking at the way the LilyPad Arduinos are developing from LilyPad Simple to LilyPad USB,



do you think we will see a larger LilyPad, like LilyPad Main Board which uses USB instead of FTDI for programming?

Then there is Adafruit's the Flora too.

Personally, i'm looking at ways of making my Arduinos portable, and the wearable platforms (LilyPad and Flora) seem like a pretty good and beginner-friendly starting points for me, instead of bringing a whole Uno, or going to the itsy-bitsy Arduinos or even ATTiny etc.
26  Using Arduino / Microcontrollers / Re: Should i somehow "reset" my Arduino when moving it from one project to another? on: March 04, 2013, 10:50:20 am
Thanks for the input folks!
27  Using Arduino / Microcontrollers / Should i somehow "reset" my Arduino when moving it from one project to another? on: March 04, 2013, 10:19:28 am
Hi all. I have been wondering, would it be somehow a good idea or best practice to somehow reset my Arduino every time i move it from one project to another one? Point being, that for one project the Arduino might be outputting stuff on various pins, and this might lead to all sorts of trouble when electronic components of a new project are connected, and the Arduino starts running the old program?

Would it be a good habit to run

Code:
setup() {}
loop() {}

before connecting new components? Or am i being too careful?  smiley-roll
28  Using Arduino / Interfacing w/ Software on the Computer / Re: What does Android logcat say when connecting Arduino ADK (ie. an "accessory") on: January 16, 2013, 07:53:10 am
Aha, I managed to solve my issue, and now my Jelly Bean logcat gives the entering USB accessory mode -message, Android pops up the dialog for starting the registered app, and i can even confirm (using demo apps) that data is being passed between Arduino ADK and Android.

The core of the issue was that the Arduino USB Host Shield libraries are no longer compatible with new, Android Jelly Bean, and i installed first a beta version of the USB Host Shield libraries from Arduino.cc (which work, after some fiddling), and then I moved to the Circuits@Home USB Host Shield libraries version 2.0. Not a lot of information about the changes in JB accessory mode is available online, unfortunately, I hope someone with the same problem will find this forum and i'm willing to give more details and help out the best I can!

Woohoo!
29  Using Arduino / Interfacing w/ Software on the Computer / Re: What does Android logcat say when connecting Arduino ADK (ie. an "accessory") on: January 15, 2013, 10:42:09 am
After more time spent with google, i can see i should expect to receive an entering USB accessory mode -message from UsbDeviceManager, f.ex. this question on StockExchange lists it.

Code:
D/UsbDeviceManager(  163): entering USB accessory mode: UsbAccessory[mManufacturer=Embedded Artists AB, mModel=AOA Board - Nodes, mDescription=Demo - AOA Nodes, mVersion=1.0, mUri=http://www.embeddedartists.com/_aoa/Demo_AOA_Nodes.apk, mSerial=N/A]
30  Using Arduino / Interfacing w/ Software on the Computer / What does Android logcat say when connecting Arduino ADK (ie. an "accessory") on: January 14, 2013, 11:06:38 am
Hi all. I'm connecting my Arduino (Mega ADK) to my Android device (Galaxy Nexus running CyanogenMod 10.1 Nightlies, based on Jelly Bean 4.2.1), and i'm having some issues.

Thus, I would like to ask from someone who actually has this Android USB Accessory stuff working, that is the output of the command

Code:
adb logcat -s UsbDeviceManager:*

Mine only says "exited USB accessory mode", and nothing else, when connecting and Arduino. On the Arduino serial monitor, i'm getting first a message that the Android is identified and supports protocol 1 and up, and then setup package error D on acc.isConnected(), when Arduino is trying to setup the file descriptors. I'm using the normal USB Host Shield libraries, not the 2.0 -flavour.

Thanks, i would really appreciate to see the logcat output of a normal, operating Android Accessory (=Arduino) handshake.
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