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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 Quote from: DVDdoug on August 20, 2013, 01:43:55 pmTake a look at this page.That was good, thanks. Stack Exchange is fantastic.Quote from: DVDdoug on August 20, 2013, 01:43:55 pmHave 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.Quote from: DVDdoug on August 20, 2013, 01:43:55 pmA 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
 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/RMr. Kirchhoff (V=V1+V2), thus a 1.2V front voltage LED turns off at 5V=1.2V+VacrossCap=VacrossCap=3.8V.Charge C = F*VCharge C = I*tTime 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 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?