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1  Using Arduino / General Electronics / Re: Confusion with Formula for LM317 circuit on: April 20, 2013, 12:02:50 pm
I found this more detailed diagram: http://www.globalspec.com/reference/81979/203279/chapter-4-linear-power-supplies

And got abit more confused  smiley-cry

Can some kind soul explain to me how this circuit works?
As in how are the voltages at the inverting and non-inverting input determined and stuff

Thanks in advance
2  Using Arduino / General Electronics / Re: Confusion with Formula for LM317 circuit on: April 20, 2013, 07:44:56 am
The LM317 itself it not connected to ground.
The Vout is regulated to 1.25V higher than Vadj.
The output voltage is set higher than 1.25V by lifting the Vadj above ground level.

The voltage over R1 is always 1.25V. The current through R1 is 1.25/R1.
That same current has to go through R2. Also the current of the LM317 itself is going through R2, but that is only 50uA, so that is not in the formula.

If R1 = 100 ohm, and R2 = 200 ohm. The voltage over R1 is 1.25V and over R2 is 2.50V. The output will be 1.25+2.50 = 3.75V

So it does not use the voltage divider rule in this case?

And the inside of the LM317 is a non- inverting op amp right?
Similar to this: http://yano.wasteonline.net/electronics/opamp/index.php?mode=1
Where Rg is R2, Rf is R1 and Vin is the reference voltage of 1.25V.
Then what is the Voltage at V-? Is it 1.25V also? If so, why?

And from which law is the formula obtained?

Thanks
3  Using Arduino / Displays / Re: To use LCD backlight or not use? on: April 20, 2013, 05:19:43 am
Guys, a little off topic:

I have a confusion with a voltage divider rule, hope you guys could help.
It is over here: http://arduino.cc/forum/index.php/topic,161659.0.html
4  Using Arduino / General Electronics / Confusion with Formula for LM317 circuit on: April 20, 2013, 05:17:43 am
Hi guys,

For a LM317 circuit as shown in this link: http://www.learningaboutelectronics.com/Articles/LM317-voltage-regulator

The formula is given as Vout = 1.25 x (1 +R2/R1)

May I know how is this formula obtained??

If using voltage divider equation: Vadj = Vout x (R2/(R1+R2)) right? (the symbols used are wrt the circuit on the link, and Vadj is 1.25)
So if I rearrange, shouldn't I get Vout = 1.25 x (1 + R1/R2)??

Am I missing something?

  
5  Using Arduino / Project Guidance / Re: What are the typical current drawn by these components? on: April 19, 2013, 10:13:01 pm
It is hard to know what you are doing but an LED with only 0.48mA through it would be very dim indeed. So no your measurements on the face of it do not sound reasonable.
When you measure 20mA through the LED, is there a resistor and what voltage are you applying to it?

What sort of meter do you have?
Does it have a battery and is it in good condition?

when measuring 20mA, there is no resistor and voltage applied is around 2V.

I am using this meter: http://www.myflukestore.com/p1348/fluke_73-iii.php

The meter looks like it should be able to read current properly, as I am able to get 20mA when I connect it in series with the LED alone.
But I am confused with the low readings I get for the LED in connection to a resistor and the LCD..
6  Using Arduino / Displays / Re: To use LCD backlight or not use? on: April 19, 2013, 09:24:40 am
Quote
Guys, I have measured my LCD current drawn( only at the Vcc pin). And it is ard 1mA.. Is this in the normal range? And when I measured the backlight alone, it is ard 6mA.. Normal?
You really haven't provided us with enough information to give you a definitive answer.  All we can do at this point is make some guesses based upon some assumptions.

Without a datasheet for your specific LCD module it is hard to tell if your values are normal but as far as the LCD current of 1 mA is concerned that seems possible. 

Without knowing how your backlight is powered and what type of meter you are using we really can't evaluate your 6 mA reading except to speculate on why it is so low.  Nick could be on the right track with the observation that the 6 mA reading "may reflect the characteristics of the meter more than the power consumed" (when you substitute the term 'current' for 'power').  This isn't much of a problem when measuring non pulsating DC or pure sinusoidal AC but can be a big problem when measuring anything else.

Also - many of the forum members do not have English as their native language and may therefore have problems with texting type abbreviations.  I was able to figure out that you meant 'around' when you used the term 'ard' but others may not have done so. 

On the other hand I still haven't figured out what these sentences mean:

    "Nonetheless, it is a hell of a lot less than 120mA and any pulsed supply has to be good!"
    "They best way to go is probably to suck it and see by flattening the battery."


Don



I have attached the Datasheet.

And the LCD is powered by the Arduino which is powered by a 7.5V battery source..

And the multimeter I am using is similar to this: http://www.myflukestore.com/p1348/fluke_73-iii.php

Is there something wrong in the way I measure the current using the multimeter?
I connected the probes in series to the Vcc(the power pin) pin of the LCD display. And the other ends of the probes were connected to the ground and 300mA slots in the multimeter...
7  Using Arduino / Project Guidance / Re: What are the typical current drawn by these components? on: April 19, 2013, 06:05:08 am
When I measure the current thru a LED alone, I get ard 20mA.

But when I measure it on a circuit that I built, it gives me 0.48mA now... Is that reasonable?
There is a resistor connected to the LED..
8  Using Arduino / Project Guidance / Re: What are the typical current drawn by these components? on: April 19, 2013, 04:46:59 am
Hmm.

For the led, used a multimeter to measure the current thru the anode leg of the led. Held the probes in series to check. To confirm the value, I connected a resistor to the led and measured the voltage between the resistor. And used V=RI to calculate. Both, I got the same value.

For the LCD, I connected the probe in series to the power pin of the LCD.

Anyway, in the multimeter itself, I connected one probe to the ground and 1 to a pin labelled "300mA".
So the current value read in the display is taken as it is? Or do I have to do further calculations?
9  Using Arduino / Displays / Re: To use LCD backlight or not use? on: April 19, 2013, 12:48:44 am
Guys, I have measured my LCD current drawn( only at the Vcc pin). And it is ard 1mA.. Is this in the normal range? And when I measured the backlight alone, it is ard 6mA.. Normal?
10  Using Arduino / Project Guidance / Re: What are the typical current drawn by these components? on: April 19, 2013, 12:39:49 am
And when I measure the backlight alone for the LCD, it is ard 6mA.. acceptable value?
11  Using Arduino / Project Guidance / What are the typical current drawn by these components? on: April 19, 2013, 12:35:27 am
Hi guys,

As the title says, I need to know what are the typical current drawn by the following components:

1) Red LED  (1.5mA?)
2) Small analogue clock running on 1.5V battery
3) Servo motor
4) LCD display with no backlight (1mA?? measured the current at the Vcc)

I have measured some of the components (those with values in bracket) and would like to check if they are normal, while the other components I am not able to measure.
12  Using Arduino / Motors, Mechanics, and Power / Re: Urgent: How to "sleep" a servo motor when not in use on: April 18, 2013, 11:52:20 pm
Quote
So I would like to know if it is possible to have a code to temporarily sleep the servo till its next rotation time.

You might try the servo.detach(); function to stop the control signal to the servo.

Ok, Then if I want to turn it back on just before the motor is required to rotate, is it servo.attach(); ?

I have attached a part of my code below:
Code:
       if (feedfrequencyperday == 2)                                                  // freq input is 2
        {
          lcd.setCursor(9,3);
          lcd.print(totalfeedforfeedfrequencyperday2);                                 // total number of feed (freq x
days)

          for (runninghour = currenthour; runninghour <= 24; runninghour++)             // runninghour acts
as hour clock value
          {
            if (feeddone == totalfeedforfeedfrequencyperday2)                         // total number of feeds
   completed
            {

              setCounter = 0;                                                       // stop running the program
            }
            else if (feeddone < totalfeedforfeedfrequencyperday2)                   // feeds not completed
            {
              if (runninghour == 24)                                                         //if runninghour = 24, reset to 0 (just
like hour clock)
              {
                lcd.setCursor(13,2);
                lcd.print("  ");
                runninghour = 0;
              }
              lcd.setCursor(13,2);
              lcd.print(runninghour);                                                        

              if (runninghour == firstfeedhour)                                              // when runninghour value reaches the firstfeedhour
              {          
                servo();                                                             // servo rotates
                feeddone++;                                                         // feeddone will increase by 1
     whenever servo rotates
                lcd.setCursor(17,3);
                lcd.print(feeddone);


              }
              secondfeedhour = firstfeedhour + 12;                                              // 2nd feed hour calculated
              if (secondfeedhour < 24)
              {
                newsecondfeedhour = secondfeedhour;
              }

              else if (secondfeedhour >= 24)
              {
                newsecondfeedhour = secondfeedhour - 24;
              }
              if (runninghour == newsecondfeedhour)                                // when runninghour reaches 2nd feed hour, servo rotates
              {
                servo();
                feeddone++;                                                        // feeddone value increases
                lcd.setCursor (17,3);
                lcd.print(feeddone);

              }
              delay (3600000);                                                  // delay func acts as the timer
                                                                             // every 1 hr interval, the
runninghour value (hour clock) will increase by 1
for test purpose, 2000ms interval used
            }

and the servo code is:
Code:
void servo()
{
  
  for (int i= 0; i < 1; i ++)
  {
    for(servoposition = 0; servoposition < 180; servoposition += 1)        // goes from 0 degrees to 180
     degrees
    {                                                                            // in steps of 1 degree
      myservo.write(servoposition);                            // tell servo to go to position in variable 'pos'
      delay(15);                                                               // waits 15ms for the servo to reach the position
    }
    for(servoposition = 180; servoposition>=1; servoposition-=1)           // goes from 180 degrees to 0
            degrees
    {                                
      myservo.write(servoposition);                       // tell servo to go to position in variable 'pos'
      delay(15);                                                           // waits 15ms for the servo to reach the position
    }
  }
}


So would it be correct to use the detach command at the end of the servo code?
13  Using Arduino / Motors, Mechanics, and Power / Re: Urgent: How to "sleep" a servo motor when not in use on: April 17, 2013, 10:58:13 pm
More info:

I am using an LCD display as well and I am making use of the "delay" command as the "timer".
The user would input a "1st hour" and a "current hour". The current time would then increase by 1 using the delay(3600000) which is 1 hour. when the current hour reaches the 1st hour, the servo will rotate. The next rotation time would be the 1st hour + 12 hours/8hours/6 hours (this depends on the user input as well). So the motor would then rotate again at the calculated time. In between, the servo does not do anything. But upon running the program, I understand that internally, the servo still running and could feel some vibration.

So I would like to know if it is possible to have a code to temporarily sleep the servo till its next rotation time.

Thanks.
14  Using Arduino / Motors, Mechanics, and Power / Urgent: How to "sleep" a servo motor when not in use on: April 17, 2013, 10:42:54 pm
Hi guys,

I am controlling a servo motor using an arduino UNO R3.
The servo motor would rotate once every 6 hours using a timer.
How do I make the servo motor sleep when it has just rotated and wake up every 6 hours when it has to rotate?
Is there a code to do this?

I need this quite urgently.

Thanks.
15  Using Arduino / Displays / To use LCD backlight or not use? on: April 17, 2013, 12:09:29 pm
Hi guys,

I am using an Arduino UNO R3, connected to a 20 x 4 LCD display.
The arduino is powered by a 7.5V battery source.
And the battery would only last for around 1 day.
Currently I am using the backlight of the LCD display on.
So I am wondering, if I do not use the backlight, would I be able to extend the battery life significantly? If so, by how much?

Thanks.
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