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46  Using Arduino / Project Guidance / Re: Saving power by cutting servo supply on: April 10, 2014, 01:28:25 pm
Removing power from a servo will remove all torque force from the servo and only leave gear friction to resist any load changes. Also removing power with a servo output signal still active will cause 'phantom' current to flow via the output pin if the arduino is still powered up. So detach servo command and a digitalWrite low should be performed. In all likelyhood when re-powering up the servo and re-attaching the servo library will mostly like cause a jitter or worst.

47  General Category / General Discussion / Re: Are you legally allowed to edit your own homes wiring? on: April 10, 2014, 11:44:13 am
In the US the National Electric Code disallows an individual to adjust mains wiring unless they are a licensed electrician. I'm not sure how strict that rule is, e.g. if it disallows replacing a light fixture or such, but y'know.

 The NEC is not a governmental organization with no regulatory powers, it's an industrial organization that publishes standards and recommendation. Typically local city or counties have the authority in this subject with their local building codes and often do stipulate NEC recommended practices. Also one's home insurance may most likely have wording about owner modified or new wiring and not cover fires if the result of owner actions.
48  Using Arduino / Motors, Mechanics, and Power / Re: Filter cap needed on regulated supply? on: April 10, 2014, 11:31:05 am
Why not just connect the 12 volt to the arduino external power connector or Vin pin?

49  Using Arduino / Project Guidance / Re: Saving power by cutting servo supply on: April 10, 2014, 10:36:57 am
For cheap it's hard to beat this one on E-bay:

http://www.ebay.com/itm/New-1-Channel-H-L-Level-Triger-Optocoupler-Relay-Module-for-Arduino-5V-/221409246814?pt=LH_DefaultDomain_0&hash=item338d04fe5e
50  Using Arduino / Programming Questions / Re: How to solve this problem ?Libraries that i download wont compile . on: April 10, 2014, 10:05:00 am
Quote
so where i can put the user download libraries ? YES i always restart my IDE after add downloaded libraries
before i got this problem

3rd party and user written libraries should be loaded into a folder named library in the user's sketch directory, If one isn't there then you need to create this library folder. Then specific downloaded libraries are saved in a folder with the same name as the xxx.h file along with any other files used by the library.

 If you do install 3rd party libraries into the arduino core section the problem is that if and when you ever upgrade to a newer version of the IDE you will lose all your 3rd party libraries unless you manual copy them before you upgrade the IDE and then manual re-install them into the IDE's core library folder. The user's sketch directory is not erased when one upgrades the IDE so all your 3rd party libraries are not disturbed.

 
51  Using Arduino / General Electronics / Re: Power consumption on: April 09, 2014, 01:14:59 pm
Quote
Honestly, I don't think most alkaline battery companies will tell you.  Its a little frustrating.

 Some of the 'name brand' battery companies do have datasheets with such information, but they can be difficult to locate. However such ratings are usually expressed at some small current discharge rate and if your actual current draw is at a higher value then that, then the equivalent mAh rating will be lower. Especially for those small 9 vdc batteries, that are really designed for low current draw devices like smoke alarms and the such.
52  Using Arduino / General Electronics / Re: Can code be a substitute for a resistor? (noob alert!) on: April 09, 2014, 01:05:40 pm
The resistor is required to establish a safe maximum led current when the analogWrite() is at 100% (255 counts), then under software you can lower the average led current from the max by lowering the analogWrite count value.

Sorry, but I don't think this is correct.

The PWM output is a combination of periods with 5v and 0v. When the voltage is high (even with a low duty cycle) the LED will pass as much current as it can get (until it burns out) and will usually draw more than the 40mA max that an Arduino pin is capable of. The resistor is essential to keep the current within safe bounds for the Arduino, under 20mA is best and lower if the LED can't accept that much. The LED will not average the PWM output.

...R

Yes, it was correct. Note I said "average led current ", not instantaneous current while the PWM is at some variable percentage at a HIGH level. The resistor is calculated to limit the current for the led, typicall 20ma for standard leds, which of course also has to be below the maximum safe current rating of a output pin when the pwm is at 100%. The calculation for the resistor is based only the voltage of the output pin, minus the Vf drop of the led, and the max safe continuous current rating for the led, it does not use 40ma in the calculation.
53  Using Arduino / Programming Questions / Re: Reading Servo Position Through Serial? on: April 09, 2014, 11:28:29 am
How about you just move your serial write statements to where the servos are actually being commanded to move?

Code:
#include <Servo.h>

Servo servo1;
int pos = 0;

void setup()
{
  Serial.begin(9600);
  servo1.attach(9);
}

void loop()
{
  for(pos = 0; pos < 180; pos += 1)
  {                                 
    servo1.write(pos);
    Serial.println(pos);
    delay(15);                     
  }
  for(pos = 180; pos>=1; pos-=1)     
  {                               
    servo1.write(pos);
    Serial.println(pos);
    delay(15);   
  }
 
  delay(1000);
}
54  Using Arduino / General Electronics / Re: Powering Arduino from 12v 1A linear regulator? on: April 09, 2014, 09:27:21 am
I think that's mainly to cover their backs.  There's no real technical reason not to do it, but numptys could connect what they think is 5V only to find it's unregulated and actually much higher.

It's perfectly safe to apply a properly regulated 5V supply to the 5V pin.  You might like to add a diode between 5V and Vin (anode to 5V, cathode to Vin) to allow any reverse voltage to safely bypass the onboard 5V regulator, just to protect it from damage in case you should apply any load to Vin.

Yes several people have shared that view, including the addition of the diode across the on-board 5 vdc regulator. Also keep in mind that powering via the 5V pin also doesn't allow the arduino auto-voltage selection circuit to properly isolate the USB  power from the board when you attach a PC to the USB connector for uploading and/or serial monitoring, as there is no Vin voltage to trigger the voltage switch which isolates the USB power from the board's 5 volt bus. Having USB 5 vdc and the external regulated 5 vdc voltage source effectively wired together is not considers a good engineering practice.


55  Using Arduino / General Electronics / Re: Can code be a substitute for a resistor? (noob alert!) on: April 09, 2014, 09:21:18 am
Quote
Sure, I could just use a resistor, but I want to be able to do as much as possible with code.  Plus, if code can substitute for a resistor, then I have an unlimited supply of resistors to choose from, and they don't need soldering! smiley


The resistor is required to establish a safe maximum led current when the analogWrite() is at 100% (255 counts), then under software you can lower the average led current from the max by lowering the analogWrite count value.

56  Using Arduino / General Electronics / Re: Powering Arduino from 12v 1A linear regulator? on: April 09, 2014, 09:11:32 am
Yeah the RS ones require an inductor, a capacitor and a diode, although I can design these into the circuit without too much bother.

Just to be 100% clear; will the Arduino function as normal from 5V by simply supplying 5V to it's 5V pin and leaving the Vin pin disconnected?

Not so simple to give a definitive answer.
 Many do just that with no problems reported. However be aware that the official Arduino recommendation is to not do that. From the product page description:

Quote
5V. This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.
57  Using Arduino / Project Guidance / Re: Servo question on: April 08, 2014, 06:18:12 pm
Quote
The 40 ma maximum rating of output pins has nothing to do with the subject of powering servos, at least to my mind?
I guess it depends on how you intend to power the servo.

Best to stick with software subjects Paul.  smiley-wink
58  Using Arduino / Project Guidance / Re: Bypass a push button as a power supply on: April 08, 2014, 06:13:33 pm
Not real clear what you are trying to describe. However maybe you just need a simple relay that the arduino turns on and off and the relay contacts are wired across the two terminals of the switch that presently opens your door. Does that help?

http://www.ebay.com/itm/New-1-Channel-H-L-Level-Triger-Optocoupler-Relay-Module-for-Arduino-5V-/221409246814?pt=LH_DefaultDomain_0&hash=item338d04fe5e

59  Using Arduino / General Electronics / Re: Battery powered board-duino: external oscillator vs. internal oscillator on: April 08, 2014, 06:05:21 pm
Quote
Does that mean the processor running at 16MHz uses an additional 4mA current compared to 8MHz?  How much of that additional 4mA is due to powering the external crystal?  Should I even be worry about the power consumption due to external crystal, or is that silly?

 An AVR chip inherently draws more current the faster you clock it, regardless of the clock source. Another way of saying that is that there should be no appreciable difference of current draw from using the internal 8 Mhz R/C clock or an external 8 Mhz crystal resonator. There are graphs in the AVR datasheet showing the relationship of chip current draw Vs clock speed
60  Using Arduino / Project Guidance / Re: Servo question on: April 08, 2014, 05:41:01 pm
Well I'm confused. Many do, in disregard of recommendations not to, power their servo via the arduino 5V pin, which can supply maybe 300-400ma and if it's a small enough servo with little mechanical load, not see any apparent problem.

 Again the best advice is to power servos separately via an independent 4.8-6.0 volt DC power supply or batteries, but that does not mean one can't get away with powering one small unloaded servo directly from the arduino via it's 5V power pin. The 40 ma maximum rating of output pins has nothing to do with the subject of powering servos, at least to my mind?

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