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721  Using Arduino / Project Guidance / Re: 7 inch led touchscreen on: June 10, 2012, 02:11:34 pm
I'd hazard a guess that 7" is more expensive as the main reason others use smaller displays - or the project has a size limit.

If the chip is the same, there should be no reason why more/fewer inches make any difference. Have you looked at the pixel count? The Arduino has to generate the pixels somehow, and it requiures some trickery with handling/expanding simple shapes to manage that with the RMA in the Arduino. If the 7" has many more pixels...
722  Using Arduino / Project Guidance / Re: Controlling a Thermoelectric heater/chiller for environmental chamber on: June 10, 2012, 01:59:19 pm
$70 H-bridge?!  It is only 8 Amp

As you do not need to switch quickly, I would use simple (cheap) relays. One relay to switch on/off and one to turn the current around (DPDT). Now your Arduino just needs a simple thermo device (choice are wide and varied, depends on how accurate you need to keep the temperature) and perhaps a RTC (realTimeClock) too so it konws the time of day even after a power glitch. (Otherwise it can just count seconds)

(NB: I am not a vivarium/aquarium owner at all)
723  Using Arduino / Motors, Mechanics, and Power / Re: Stepper motors and drivers problem on: June 07, 2012, 10:59:28 am
OK, here is some very simple code I have recently used to drive two steppers at the same time. I do not use any library, prefering to drive them directly. One is a Dir/Step type driver, the other a full H-bridge. The idea here is the StepCoil runs continuously (the MoveSteppers() is called as often) determined by "Slowdown", and the StepWireRatio() calls the other stepper (the one using dir/step) so I get the right kind of diagonal movement.
void MoveSteppers() {
 if ( micros()/100-Timer > Slowdown ) {
    Timer=micros()/100 ;
    StepCoil() ;
    StepWireRatio() ;

void StepWireRatio() { // Step according to ratio and respect limits
  TFC_Ratio += TFC_Ratio_Nom ;
  if ( TFC_Ratio > TFC_Ratio_Den ) {
    TFC_Ratio -= TFC_Ratio_Den ;
    if (TFC<TFC_Left) TFC_Dir=HIGH ;
    if (TFC>TFC_Right) TFC_Dir=LOW ;
    StepWire() ;

void StepWire() { //step always
  digitalWrite(WireDir,TFC_Dir); // adjust direction as needed
  digitalWrite(WireStp,(TFC%2>0)?HIGH:LOW) ;  // Step the Wire motor
  TFC = (TFC_Dir==HIGH)?TFC+1:TFC-1 ;
  if (TFC_Dir==HIGH)
    Serial.print(TFC_Right-TFC) ;
  Serial.print(TFC_Dir==LOW?" <":" >");Space(3);

void StepCoil() {
  // Change to next Coil state
  TurnState++ ; CursorGoto(2,13);
  switch (TurnState%4) {
    case 0:    // 1010
      digitalWrite(Coil_A, HIGH);
      digitalWrite(Coil_B, LOW);
      digitalWrite(Coil_C, HIGH);
      digitalWrite(Coil_D, LOW);
    case 1:    // 0110
      digitalWrite(Coil_A, LOW);
      digitalWrite(Coil_B, HIGH);
      digitalWrite(Coil_C, HIGH);
      digitalWrite(Coil_D, LOW);
    case 2:    //0101
      digitalWrite(Coil_A, LOW);
      digitalWrite(Coil_B, HIGH);
      digitalWrite(Coil_C, LOW);
      digitalWrite(Coil_D, HIGH);
    case 3:    //1001
      digitalWrite(Coil_A, HIGH);
      digitalWrite(Coil_B, LOW);
      digitalWrite(Coil_C, LOW);
      digitalWrite(Coil_D, HIGH);
You Milage may vary. No Garantees smiley
724  Using Arduino / Motors, Mechanics, and Power / Re: Stepper motors and drivers problem on: June 06, 2012, 05:56:15 pm
Try entering "57BYGH115-003 " in your google search. That usually gets you several web pages where the specfications (voltage, amperes etc ) are shown.

In your Arduino IDE try the menu File - Examples - Stepper - One revolution. There is the code fo one stepper. You only need to replicate the line defining the Stepper varaible (with a new name) and one call to each steper variable's move at different speeds. I also suggest you Google for "Arduino Stepper nonblocking " to run them simlultaneously.

Running at max speed depends on the load, and a bit of tweaking the (software) acceleration and driver current "curves" (if the DQ-542MA supports that)
725  Using Arduino / Programming Questions / Re: PC Keyboard on: June 06, 2012, 05:21:43 pm
Your code seems to use the numeric keypad as a simple joystik operation. You should look at the switch ( n )  case construct, it is more fitting for this type of code.

Servos stop on their own. Your code tells the "lijevi"servo to move to position "85" when you push "2". If you hold "2" down, it will receive this command repeatedly, and not move (after the first move has completed). If you mean for it to keep moving away from "90" as long as you hold "2", then you must do something linke
servo_lijevi.write( which will move it another 5 degrees for as long as you send "2" from the keyboard.

If the servos are continous, then your code will set the servo speed to "85" (a slow move in one direction) and keep doing that for every "2" (it is already moving, so additional "2"s have no effect, like before). BUT letting go of "2" will keep not stop it (as it remembers the last write). In your loop you should do an "else" to act on (Serial.available is not >0) and send the servo_x.write(nn) that makes it stop.

Another hint: If you hold a key on a pc keyboard for a few seconds, it will send many "2"-characters very quickly, which ar buffered in the Arduino input buffer, so even if you let go, it may still have lots more movement to go.

The English is OK smiley-wink
726  Community / Bar Sport / Re: The How Long Post on: June 06, 2012, 05:01:08 pm
Three projects that were collaborative with others had a definte delivery deadline - they took "all the time that was available". If we started the project and it was 2 weeks to "showtime" we spent 1.999 weeks on it, calender time. The amount of man hours .. dont want to think about that .. but the usual exponential curve with hours/day as dead line approached. These projects have been between 1 week and 1 month.

My other projects seem to get stuck at the 85% or 95% complete - usually a case of finish the coverbox, or make it a little more sturdy for moving about, or replacing the glue with proper screws. The small projects take 3 days - but two projects are in eternal POC, tweak and redesign now for the 2nd year.

So to answer the OP - any number between 2 to 2000 hours.

Tips for reducing time? Let me ask a contra-question: Why? It is my hobby, I do it for enjoyment, why shorten it? OK, producing more finished project to show off to friends and family would be nice, too. ( Hmmmm-- food for thought. )
727  Development / Other Software Development / Re: #include documentation on: June 04, 2012, 06:53:17 pm
The documentation on is rather sparse.

Doing multifile programs in the Arduino IDE is not easy - despite the fact that it is good programming practice. On the other hand, most Arduino projects are only 50 or 200 lines. For a single project getting to big, just write several .PDE/.INO files, and have them in the same sketchbook folder. When you compile the IDE will compile them as one file. (The IDE also "cheats", compared to pure "C" - it rearranges the functions so they are defined before being called - thus the order of the PDE files is irrelevant). No need to use .h

I have found that you must have a subfolder called LIbraries in your Arduino sketch folder, and in there you can have folders wich contain a .h and .cpp files. This is a proper library. The IDE looks both in this "user-library" folder and in the system library folder (and I think also in a subfolder to the compiler). As far as I know it makes no difference if you use " or <>

728  Community / Bar Sport / Re: Congratulations to the Latest Two Members to the 10K Club! on: June 04, 2012, 06:17:50 pm

(This post got me another tiny step closer to achieving the same smiley-wink smiley-wink )
729  Community / Bar Sport / Re: Your latest purchase on: June 04, 2012, 06:08:57 pm
Bought a 3D print at - just a tiny test shape. The picture shows the same shape done on the now rather old MendelRepRap at the club, and another done on a friends Ultramaker. You may guess which is which smiley Price info:
500$ machine
20¢2000$ machine
10$ plus shipping50000(?)$ machine
730  Using Arduino / LEDs and Multiplexing / Re: general question: NxM RGB LED matrix with PWM on: May 23, 2012, 03:10:21 pm
Why is everyone using additional hardware like shift registers od led control ics?
Shiftregisters: Because there are not enough pins on the Arduino. LED control:For good LED control you want constant current. (More reasons below)

M Digital IO pins for the cathodes (my case 10) and N*3 PWM pins  (my case 9)
I can not see any obvious flaws in that argument. Remember that you still need a transistor/FET on all (your case, 19) lines - the  microcontroller can NOT give enough current. Worst case the top transistor/FET needs to cope with 10 LEDs (about 0.5 A, maybe 1 A depending on your LEDs) the bottom transsitor likewise.

As far as i have read one scans the whole matrix row by row (M=10). Inside the active row one scans again over all leds (N*3). What scan times can i expect from an arduino mega 2560 and how do i calculate it?
Each LED can at most only be ON a 10th of the time, when you scan the rows. You can then parallel control your 9 column lines. Or the other way round. You define the scan rate, as fast as possible to avoid flicker, ie 100Hz+. The standard PWM runs at 400Hz, so you may get odd "beats" between your scan rate and the PWM. An LED ic will do the PWM at a higher rate, and you can tweak the Arduino core likewise.

To get the LED to seem bright enough, when the scanning limits it to a 10th ON, you can overdrive it so the "average" is within specs. The circuits get a little tricky, you dont want the overdrive to happen if the program stops and one row remains lit ... so the LED ics are nice.
731  International / Scandinavia / Re: arduino uno alarm on: May 21, 2012, 04:32:16 pm
Velkommen til!

Når du læser lidt af de andre indlæg, så kan du se at du er nødt til at fortælle lidt mere end kun "nemt og hurtigt alarm".

Hvad er den "nemme" del : Konstruktion? Kredsløbet? Softwaren? Brugen af det?

Men begynd med at fortælle
1) Hvad det er du overvåger (temperatur, vandniveau, antal fodtrin på et følsomt område)
2) hvordan du måler det (eller har tænkt at måle det, sensor type)
3) Hvad alarmen består af (blink, lyd, mail, SMS ...)
Og måske hvorfor du mener du behøver en Arduino involveret (kompliceret niveau/antal sensor input, kompliceret alarm (sende en SMS))

(Istedet for en lang beskrivelse kan du attache en tegning, muligvis en indscannet en)
732  Using Arduino / Programming Questions / Re: Branch To Subroutine on: May 06, 2012, 11:02:00 am
On a standard Arduino pin 0 will not work as an interrupt, only pin 2 and 3. So your interrupt is never activated, never setting resetP to 1, thus never satisfying the if to call your subroutine.
733  Using Arduino / Programming Questions / Re: Branch To Subroutine on: May 06, 2012, 10:57:13 am
Subroutines are called, not branched to.

There is nothing in your description as to why it should not be called.

Looking inthe attached code, I am missing a few #includes (or the other *.cpp in your directory) to get it to compile. That way I could see if you have mismatched a bracket or two.

You only go into your reset code if the interrupt on pin 0 triggers. Which never happens as I mention further down.
734  Using Arduino / Programming Questions / Re: Ardiuno UNO, a4983 driver and stepper motor on: May 05, 2012, 07:57:52 am
Swapping the 4-wire is a good try, assuming the chip is controlled correctly. It is enough to just swap any (adjacent) pair of motor wires.

Code suggestion (your actual pinnumbers and values may vary)
const int Mdir=6 ;
const int Mstep=7 ;
pinMode(Mdir,OUTPUT) ;
pinMode(Mstep,OUTPUT) ;
digitalWrite(Mdir,HIGH) ;  // LOW to go the other way
for (int j=0; j<200; j++) {
  digitalWrite(Mstep,HIGH) ;
  delayMicroseconds(12) ; // Step occurs on rising edge
  delay(3) ; //  more delay-> slower rotation speed.
Lastly, if you use delay() you are blocking, that is, the Arduino wont be able to do other things, like watching if a button is pushed, whilst turning the motor. That is also how the stepper-library works. If that is good enough, fine. Otherwise you have to start reading about "avoid using delay". Here and here and lots more from other contributors.
735  Using Arduino / Programming Questions / Re: From float to seperate INTs - in an elegant manner :-) on: May 05, 2012, 07:29:28 am
Damn, you're right ! smiley Didnt test it. The cause is that 24.8 is (probably) internally stored as 24.7999999... due to the finite limit of representing decimal fractions in binary.

Well, in an effort to keep my pride intact smiley-wink and to keep it "elegant" use the round function for the last bit
c=round((f[n]-int(f[n]))*10) ;
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