Artists create aesthetic problems and solve them. When an artist creates a problem which is technical in nature, but for which no commodified solution exists, a solution must be invented. This is the realm of "making". Making often represents novel unions of sensible phenomena, information, and dynamic objects. 

making blog

Thyratron under load

Submitted by Ed_B on Thu, 10/21/2010 - 22:38

A thyratron is a type of electron tube used for controlling large amounts of AC power in motor drives and simlar applications. I have a small collection of thyratrons. This one is medium size. It can switch up to about 1000 volts and about 1.5 amps.  The load it's carrying is a 40 watt 120 volt light bulb (out of the image frame). (Click READ MORE to see the whole post.)

Simple Subversion: status, add, delete, and commit

Submitted by Ed_B on Thu, 10/07/2010 - 14:39

I'm using Subversion on google code for writing "timer-scheduler", an Arduino library.  (http://code.google.com/p/timer-scheduler/)  It turns out that the everyday commands are add, delete, status, and commit. I use them on the command line. Here's how they work for me.

Warning: It is important to understand that Subversion manages the local svn folders as well as the ones on the svn server. In particular, all file/folder deleting operations on the local folder must be done with the "svn delete" command. You can add folders locally, and then use "svn add" to add them to the Subversion project. But you cannot delete local folders and then "commit" (See "Deleting" Below.)

click READ MORE to see the whole post

 

timerInterrupt_Overflow.pde

Submitted by Ed_B on Mon, 08/30/2010 - 16:12

click READ MORE to see the whole post

timerInterrupt_Overflow.pde Copyright (c) 2010 Ed Bennett <ed@kineticsandelectron ics.com>

 
A simple demo of using the Timer2 overflow to generate interrupts in an Arduino.
Measured output is a sqaure wave of period 8.2mS. Note: A complete, technical explanation of an
AVR timer setup is in the posting on timerInterrupt_Match.pde Refer to that for more detail. Setup
for Timer0 should be nearly identical to implement.

timerInterrupt_Match.pde

Submitted by Ed_B on Mon, 08/30/2010 - 16:09

click READ MORE to see the whole post

timerInterrupt_Match.pde  Copyright (c) 2010 Ed Bennett    Demo of setup for a compare-match timer2 interrupt for an Arduino AVR.  Timer2 counts up to a pre-defined value, then clears the counter and sets an interrupt which toggles an i/o pin.   The program generates a square wave with a period of about 30uS -- at the expense of the chip doing anything else. Slowing the interrupt rate will free up the processor, but the speed control values chosen for this example are to make the output go fast.


Happy Pins 7 -- video demo and Arduino code example

Submitted by Ed_B on Thu, 07/22/2010 - 23:10

I'm discovering that there was an unknown-unknown challenge in writing the timer-scheduler demo examples. It really shouldn't have been a surprise at all, but giving aesthetic structure to time with C code is an odd thing to do. It must be a little like composing music in code. That's something to ask around about. The previous posting had a demo video, but the code behind it was awful. I didn't understand what the mindset should be to use the timer-scheduler library. The right way to think about it in the context of rhythmic composition is pretty much limited to timer events controlling other timer events and generating outputs. Here's a video, and the Arduino sketch is below. Code is at http://code.google.com/p/timer-scheduler/

READ MORE ==>

Flag Register

Submitted by Ed_B on Sun, 07/18/2010 - 22:34

In a previous post I described the use of flags in code and the cpu. Flags are data bits that are grouped into bytes called flag registers. The the flags can be True or False, also called Set and Clear. Flags can be read from or written to by the hardware in the cpu, and by the user's code. Some flags are only used internally by the cpu. An important use of flags in user code is in making and using timers. Here is a demo of using flags to control timing of some lamps, some rotary solenoids, and a very old dumb terminal. The Arduino controlls everything. The dumb terminal only prints messages from the Arduino.

 

Differences in Approach to Choosing a Timer Method

Submitted by Ed_B on Tue, 07/06/2010 - 23:04

 The timer-scheduler library gives three methods for using timer generated events in your code. 

  • Polling a flag attached to a timer.
  • Using callback functions that are activated by the timers.
  • Driving an i/o pin directly from the timer service (pin-direct method).
  Poll a Flag Callback Pin-direct
loop() will be interrupted during normal operation (this is usually ok)    X  
user code runs at every timer event (too much can choke the AVR)    X  
must attach a pin to a timer to see anything happen      X

can attach a pin to timer, but it's better to control the pin in the program

 X  X  
user code must be tight and fast (no delay(), minimal use of Serial.print(), etc.)    X  
should avoid using delay()  X won't
work
 
can have empty loop()    X  X
can use Timer.setHighTime() and Timer.setLowTime()  X  X  X
can use Timer.repeat()  X  X  

 

Timer-Scheduler Library Examples Using Three Different Methods

Submitted by Ed_B on Wed, 06/30/2010 - 12:47

I've been working on a  timer/scheduler library for fairly accurate, low speed timing of function calls on the Arduino. Using timers to schedule simple function calls, you can have multiple repeating events happening at the same time. As you know, this is very hard to do using delay().  The timer-scheduler library can give the appearance of multiple channels of independent activity. It looks kind of like multitasking. Maybe it is. Maybe it isn't. 

The timer-scheduler library provides eight (8) software timers. There are three methods for using a timer to make something happen. The first method is polling a flag. A flag is read from or written to by hardware and your code. A flag has two states: set (high) or clear (low). Flags tell you when something has changed in hardware. The second method uses callbacks. These are small functions you write. They fire off when a timer event happens.  The third method, pin-direct, attaches a software timer directly to a pin. The pin will go high and low based on the timer settings.  The videos are of the actual code samples running. The video for the flag-polling method and the callback methods is the same footage(!?) for both methods, because they look the same when they're running. The video for the pin-direct sketch has asymmetrical blink patterns because it was more fun to write it that way.

  READ MORE =====>

 Video for the flag-polling method and the callback method:


Notes about SVN and Mac

Submitted by rdrink on Sat, 06/26/2010 - 06:07

I started this as a comment to Ed's post but decided to make it it's own. I wanted add a few notes, especially for first time svn users and especially for Mac users...

Using the Command Line to Interact with Google SVN During an Edit

Submitted by Ed_B on Mon, 06/14/2010 - 20:41

Now that the timer-scheduler code is safely stored in Google's SVN system, it's time to try a first edit. I'm using the Kate editor for my project. Kate is very minimal, but has most of the features I  want for simple projects like these. The Kate tools menu has a terminal window available. As you click around the files in your project, Kate will cd to the directory containing the file in the editor window. I'm issuing SVN commands from the terminal window. In the screenshots below, I'll check the project to see what's there, edit the TimerScheduler.cpp file by adding a "warning" to line 25 and save to my hard disk. Then run update in case I think I might need to merge my changes with someone elses (none required). Running status -v shows the modified file  flagged with "M". Then the change is committed to SVN. The project version increments to 3, even though only the TimerScheduler.cpp file was changed. The full version increment on each commit, no matter how small, is a feature of SVN. A checkout gives you get the "head" version that has all the most current files in it. I'll learn more about that soonly.

See what's there:
svn status -v

make changes, then save to hard  disk

READ MORE =====>

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