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961  Using Arduino / Microcontrollers / Re: L293D overheated but not burned !! what's the solution ? on: July 28, 2013, 03:56:04 pm
can you please show me an example on how to do it by posting a picture ?
I have attached ST's datasheet (PDF).
If you look at page 4 of 7 ("4/7") they depict [see "Figure 2"] the sort of board surface required.

i wasn't sure were to ask this question so i chose microcontrollers isn't it ?
I'm not "The Boss", but a L293D is a "four channel driver".
962  Using Arduino / Networking, Protocols, and Devices / Re: Serial is not working! on: July 28, 2013, 03:40:44 pm
But then why isn't the Uno reacting at all?..

Maybe it's your sketch?

Code:
if(Serial.available() > 0)
{
    reader = Serial.read();
    if(reader == 0x31)   // hex code for numeral 1
    {
       digitalWrite(4, HIGH);
    }
}

Once it gets a '1' then D4 will go on, so I assume you can send it a '2' or other characters or modify it to toggle or turn off otherwise.
963  Using Arduino / General Electronics / Re: Prototype PCB board soldering tips needed on: July 28, 2013, 03:23:35 pm
Tin your tip!
Clean off the tip and then have some fresh melted solder on the tip of the iron, just before you touch it to your work, so that you don't have to heat the joint so long - touch the joint and hit it with a bit more solder.
964  Using Arduino / Networking, Protocols, and Devices / Re: Serial is not working! on: July 28, 2013, 03:09:42 pm
I was modifying my previous Reply, but while you were composing yours

Following, I'll restate what I'd added:
If you just want to verify results of the test sketch above (seeing is believing), remember that the output (TX) from D1 is normally high - place an LED with its anode to +5 and its cathode going to D.  A resistor isn't needed because D1 and D0 have on-board resistors (600Ω) between the output header and the ATmega328 pins.
965  Using Arduino / Microcontrollers / Re: L293D overheated but not burned !! what's the solution ? on: July 28, 2013, 01:05:57 pm
so about the piece of metal for heat sink, it should be connected with a wire to the pins ?

No, that will not work.  
Ideally, those pins (Gnd - 4, 5, 12, 13) should be soldered to a "ground plane", with the underside of the IC laying right on the copper of the "ground plane".  That's how the heat gets drawn out - mechanical, physical contact.
Barring that, any heatsinking will have, at best, only marginal effect.
I would not anticipate any marked result from clamping a piece of metal atop the IC.

The L293 is a #%@& IC that people expect too much from.

> > > Why is this being discussed in "Microcontrollers"?
966  Using Arduino / Networking, Protocols, and Devices / Re: Serial is not working! on: July 28, 2013, 10:22:37 am
If you look at one of the schematics ("the board" == Arduino whichever, Uno, Nano, etc) you'll see that those LEDs aren't connected to D0 / D1 at all.
D0 & D1 are routed back to the USB interface IC, yes, but the LEDs are connected to two entirely different pins on the USB interface IC.
They 'blinkle' only when the USB is connected, indicating USB comms activity.

Uploading a simple sketch --

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

void loop ()
{
  Serial.print("A");
  delay (1000);
}
demonstrates this much.

When connected to the USB, the on-board "TX" LED shows activity.
But when disconnected from USB and powered through the barrel jack, there is no "TX" LED activity.

> > > If you require a comms indicator, I could offer suggestions. 
If you just want to verify results of the test sketch above (seeing is believing), remember that the output (TX) from D1 is normally high - place an LED with its anode to +5 and its cathode going to D.  A resistor isn't needed because D1 and D0 have on-board resistors (600Ω) between the output header and the ATmega328 pins.
967  Using Arduino / Networking, Protocols, and Devices / Re: Serial is not working! on: July 27, 2013, 07:00:20 pm
The RX and TX LEDs only indicate the comms via the USB, they're not status indicators for activity on D0 and D1.

I may not have this right, but I think you'd have to modify the board to power the USB IC.  As built, it only gets power from the USB cable.  V_USB can power the board, but powering the board through Vin or the external barrel connector does not feed the V_USB.
968  Using Arduino / Microcontrollers / Re: Arduino Nano V3.0 328 Problem Uploading To Board on: July 27, 2013, 11:05:32 am
I once bought some compatibles that "didn't work" - because the USB cables included with them were all no good.

I've seen reviews of compatibles sold on dx.com that weren't bootloaded.  They had a "blink" running, must have been uploaded ICSP.

The official Gravitech boards are official Arduino licensed product.
969  Using Arduino / Project Guidance / Re: How To Display Data On A Dot Matrix Display - Behaviour Lights on: July 27, 2013, 10:34:43 am
http://playground.arduino.cc/Main/HT1632C

https://github.com/gauravmm/HT1632-for-Arduino

http://blog.generaleccentric.net/?tag=holtek

Your ebay seller states, "The small API with fonts was written on NXP LPC1769 in standard C/C++.  API can be easily port to other processors.  Full source code is available free to use without restriction, BSD style license. "
He didn't link to "small API" or the "full source code" nor is there any info there on the connector/pin-out.  Maybe it's like what's shown in the first link I provided.

Wouldn't it be easier to assign each student a number?    smiley-twist
970  Using Arduino / LEDs and Multiplexing / Re: LED activates only when probed with meter on: July 24, 2013, 07:31:33 pm
"Probing" with an ohmmeter can forward bias a P-N junction, too.
971  Using Arduino / Motors, Mechanics, and Power / Re: Jerky motion/incorrect code reading when DC wall adapter is used as power source on: July 23, 2013, 01:33:38 pm
Is the wallpack providing juice for
  • the motor
  • the motor and the adafruit board
  • everything (the Arduino incl.)
?
972  Topics / Device Hacking / Re: Hack garage door opener Liftmaster 973LM on: July 22, 2013, 01:35:20 pm
A transistor could be placed at/near the rear panel terminals without tearing anything apart.
But that's a lot for someone asking this question and being "totally new to Arduino/electronics in general" to get right.
By getting the relay clicking at the kitchen table, it'd be easy enough to lead the relay contacts (no polarities to observe) out to the terminals.
It could be big fun with a "relay shield", too.

I don't know if it's supposed to be available selectively, sporadically, switched on as needed or  ready at all times (battery powered v. line powered.)
What to do, yes?
"The best laid schemes o' mice an men..."
973  Using Arduino / Project Guidance / Re: Getting into radio on: July 21, 2013, 07:49:01 pm
Jammer Shield...
it's
Sparkgapuino
974  Topics / Education and Teaching / Re: How well US students prepare for science and engineering on: July 21, 2013, 04:06:51 pm
What are people who cannot "add" doing in college at all? 
Remedial arithmetic and remedial language arts, too - in college - so they can hang out for two or three years for an "associate's" degree (drop out).
It's absurd.

I don't understand the "engineering" angst, it's not everyone's ken and that's OK.  I think the last thing anyone needs is a haircut from an "engineer".

Colleges do not turn out well-rounded people.  Nowadays they manufacture self-important excuse-makers and conceited, would-be technocrats.
975  Using Arduino / General Electronics / Re: An inverter for under 3 bucks! on: July 21, 2013, 03:40:51 pm
On the one hand, there's the raring to tear into this thing this way and on the other there's a reluctance to cobble up a little circuit from two or three components to find out what's going on.

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