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1  Using Arduino / General Electronics / Re: Sizing source drive on: April 05, 2013, 08:37:20 pm
From the 2981 i was planning some resistors before the leds. This is why I was measuring the output of the 2981. I am getting no where near the results I need. I only need 60ma and 7 v per segment. Could I have a faulty unit? I figured I would get no output at all if faulty.
2  Using Arduino / General Electronics / Re: Sizing source drive on: April 05, 2013, 04:53:00 pm
I guess that is where I am confused, I thought the max7219 is sending a low voltage, low current to the UDN2981 source drive. I though this low current will switch the source drive will allow the 12 volts higher amp current to the segments. I am wrong in this assumption? I thought the source drive acts as a transistor?
3  Using Arduino / General Electronics / Re: Sizing source drive on: April 05, 2013, 03:36:23 pm
forgive me,maybe, i am not describing my problem well enough. My layout works, however the leds are not as bright as they are supposed to be. i can get digits to scroll ( using ledcontrol library with intensity-15)
So the MAX is turning on the source driver, however i just tested and with a 12v input i am only getting 6.9v output.

yes, that was my post, after posting i thought it may be too specific, and thought i would go for a more general question.
4  Using Arduino / General Electronics / Re: Sizing source drive on: April 05, 2013, 03:14:39 pm
UDN2981
5  Using Arduino / General Electronics / Re: Sizing source drive on: April 05, 2013, 01:40:19 pm
I thought the source driver will take small current from the MAX7219 and "open" the path for the 12v to go to the segment. I thought the driver act as a series of transistors. I guess, then that comes back to my original question, Where can learn about how to properly use and size a source driver, no matter what the application.
6  Using Arduino / General Electronics / Re: Sizing source drive on: April 05, 2013, 11:57:02 am
i am developing  a larger 7 segment display which uses about 7 volts 60ma per segment. The source drive will have a 12v 2A regulated supply, the source drive would be turned on from a max7219. One question i have is, is the output voltage dependent upon the input voltage from the max7219? (i.e. will a 4 volts result in more output voltage than a 1v?)
7  Using Arduino / General Electronics / Sizing source drive on: April 05, 2013, 07:21:55 am
Can anybody point me where to learn more about how a source drive ( transistor array) works, how to read the datasheet and properly size. i am trying to troubleshoot a design and i am a beginner.
8  Using Arduino / LEDs and Multiplexing / Re: Max 7219 with 12v Power on: April 05, 2013, 05:26:09 am
I am using the MAX for it's intended use, that is a seven segment display. However, I am confused with the lack of current, especially using a 12v, 2A external voltage boost. From what I understand from the data sheets, I should be able to get an output around 500ma if needed?
9  Using Arduino / LEDs and Multiplexing / Max 7219 with 12v Power on: April 04, 2013, 07:01:27 pm
I need help,
I have prototyped a 4 digit seven segment up/down counter, however have run in to difficulty getting the leds bright as i want.
First the schematic is attached, It utilizes MAX7219, UDN2981 Source Driver,ULN2803 Sink Driver.
(I know everything works because I had the digits working)

I tested the voltage to see what the actual voltage to the segments are, to my surprise alot of voltage is used by the drivers,
With a 12volt external supply to the source drive, I read approx 7.0 volts but slowly rises to past 8 volts.

I then attached required leds for a segment , required voltage 3.8 V,(2 leds at 1.9V), 60ma (3 sets in parallel), 49OHM resistor.
To my surprise current to all leds total was 30ma. Was trying to get 60ma, (20 for each series).

Why the fluctuation in my voltage after the UDN2981, and why the lack of current to my leds?
Is it possibly a capacitor? Might the drivers be wrong size or faulty?
I am pretty much a beginner when it comes to electrical engineering, so please be patient with me as I try to learn.

10  Using Arduino / General Electronics / Re: 12v Power supply for Uno, Smart idea? on: March 01, 2013, 11:26:04 am
Thank You all for your input.
It is nice to know the arduino will not get ruined.
I will test and see if it gets warm.
11  Using Arduino / General Electronics / Re: 12v Power supply for Uno, Smart idea? on: February 28, 2013, 02:40:50 pm
if you say "ow!" then you need to reduce the load.

Or lower the input voltage. Higher input voltage = more voltage to drop = more heat.

BTW, 12V is listed as the upper recommended supply voltage in the Uno specs.

That is what is getting me a little nervous, (the 12v upper limit). That is why I thought about lowering input voltage with a regulator before it gets to Arduino and its regulator.
12  Using Arduino / General Electronics / 12v Power supply for Uno, Smart idea? on: February 28, 2013, 12:57:45 pm
Is it smart to  use a 12vDC / 2A regulated power supply for an Arduino Uno?
I have heard that the voltage regulator on the Arduino may overheat.

My project is a 4 digit (seven segment display).
I am using a max7219,source driver and sink drivers to deliver the external 12v power supply to my display (Segments require 60ma/9V).

Therefore I beleive the arduino is only using 5v to power the max 7219 and small amps to open the source drive outputs. Everything is working GREAT right now. But I am finalizing the project and want to only have one power source to my project. I have been powering the Arduino by USB until this point. I do want to utilize the 12v/dc regulated power to power the Arduino.

I was wondering if I should regulate the 12v source to 7volts before plugging into Arduino?
Any thoughts?  I would hate to overheat my Arduino
(I am new to this and am proud of how much I have learned in 6 months.)
13  Using Arduino / Programming Questions / Re: Beginner 7 segment display on: February 22, 2013, 10:38:59 pm
Thankor the response,
I made changes based on recommendations.
The same result, my digits scroll from "00" to "01" then stops.
They stay nicely lit but stop scrolling.
I have attached my updated code.
Code:
#include "LedControl.h"

LedControl lc=LedControl(12,11,10,1);
unsigned long delaytime=200;//  v*75
void setup() {
  /*
   The MAX72XX is in power-saving mode on startup,
   we have to do a wakeup call
   */
  lc.shutdown(0,false);
  /* Set the brightness to a medium values */
  lc.setIntensity(0,15);
  /* and clear the display */
  lc.clearDisplay(0);
}
void loop() // function to send digits to 7 seg led
{
  for(int v=0;v<100;v++)  {
 
  byte ones=v%10;
  v=v/10;
  byte tens=v%10;
  v=v/10;
 
  lc.setDigit(0,1,(byte)tens,false);
  lc.setDigit(0,0,(byte)ones,false);
  delay(3000);
}
}
14  Using Arduino / Programming Questions / Re: Beginner 7 segment display on: February 22, 2013, 08:08:36 pm
sorry,
updated code posted correctly.
Did I say I am new to this.

Code:
#include "LedControl.h"

LedControl lc=LedControl(12,11,10,1);
unsigned long delaytime=200;//  v*75
void setup() {
  /*
   The MAX72XX is in power-saving mode on startup,
   we have to do a wakeup call
   */
  lc.shutdown(0,false);
  /* Set the brightness to a medium values */
  lc.setIntensity(0,8);
  /* and clear the display */
  lc.clearDisplay(0);
  int v = 0;
}
void loop()
 
// function to send digits to 7 seg led

{
  for(int v=0;v<99;v++)  {
 
  int ones;
  int tens;
  boolean zero;
 
  if(v > 99)
    return;
  ones=v%10;
  v=v/10;
  tens=v%10;
  v=v/10;
 
  lc.setDigit(0,1,(byte)tens,false);
  lc.setDigit(0,0,(byte)ones,false);
  delay(3000);
}
}
15  Using Arduino / Programming Questions / Beginner 7 segment display on: February 22, 2013, 08:04:40 pm
I am a beginner, but i have managed to develop a 2 digit seven segment display.
I am utilizing an external 12vdc power source, max7219, common anode digits, source driver and sink drivers.
I have been developing source code to scroll through 0 to 99. Unfortunately i go from 00 to 01 then i am out of the loop and nothing else happens. I have been through the arduino foundations, tutorials etc... . But I still can not figure out what I am doing wrong. Maybe somebody can lead me in the right direction to get this to work.
(I hope my code is posted correctly, my first time for posting).
I can set "v" to any value and it displays correctly.
Thank you in advance.
   
Code:
[quote]
#include [color=#006699]"LedControl.h"[/color]

[color=#CC6600]LedControl[/color] lc=[color=#CC6600]LedControl[/color](12,11,10,1);
[color=#CC6600]unsigned[/color] [color=#CC6600]long[/color] delaytime=200;[color=#7E7E7E]//  v*75[/color]
[color=#CC6600]void[/color] [color=#CC6600][b]setup[/b][/color]() {
  [color=#7E7E7E]/*[/color]
[color=#7E7E7E]   The MAX72XX is in power-saving mode on startup,[/color]
[color=#7E7E7E]   we have to do a wakeup call[/color]
[color=#7E7E7E]   */[/color]
  lc.[color=#CC6600]shutdown[/color](0,[color=#CC6600]false[/color]);
  [color=#7E7E7E]/* Set the brightness to a medium values */[/color]
  lc.[color=#CC6600]setIntensity[/color](0,8);
  [color=#7E7E7E]/* and clear the display */[/color]
  lc.[color=#CC6600]clearDisplay[/color](0);
  [color=#CC6600]int[/color] v = 0;
}
[color=#CC6600]void[/color] [color=#CC6600][b]loop[/b][/color]()
  
[color=#7E7E7E]// function to send digits to 7 seg led[/color]

{
  [color=#CC6600]for[/color]([color=#CC6600]int[/color] v=0;v<99;v++)  {
  
  [color=#CC6600]int[/color] ones;
  [color=#CC6600]int[/color] tens;
  [color=#CC6600]boolean[/color] zero;
  
  [color=#CC6600]if[/color](v > 99)
    [color=#CC6600]return[/color];
  ones=v%10;
  v=v/10;
  tens=v%10;
  v=v/10;
  
  lc.[color=#CC6600]setDigit[/color](0,1,([color=#CC6600]byte[/color])tens,[color=#CC6600]false[/color]);
  lc.[color=#CC6600]setDigit[/color](0,0,([color=#CC6600]byte[/color])ones,[color=#CC6600]false[/color]);
  [color=#CC6600]delay[/color](3000);
}
}

[/quote]
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