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16  Using Arduino / Motors, Mechanics, and Power / Re: How to power 4.5v DC motor with 12v power supply using dk electonic motorshield? on: August 30, 2014, 07:25:46 am
For 7 cents less, you get 50 diodes  smiley-razz

You're making something of a "straw man argument."
You don't need 100, or even 50, just 8.
I have a plenitude of diodes around here.

Ok that means that in any case i have to go down to 5V.

Well, it doesn't. 

You can lead a horse to water but you cannot make him drink.

It seems you're hell-bent on going to a lot of effort to make the problem fit the solution.
17  Using Arduino / General Electronics / Re: PWM drive MOSFET not working properly. on: August 29, 2014, 10:35:48 pm
Connecting all the grounds got it to work.

Imagine.

How do I probe the circuit to see the signal?

Provided that your scope and circuit are "isolated" (your FET circuit is on batteries or the DC source is not referenced to Neutral/Chassis) then you should be able to place the scope across the LED and the resistor.
18  Using Arduino / Motors, Mechanics, and Power / Re: How to power 4.5v DC motor with 12v power supply using dk electonic motorshield? on: August 29, 2014, 10:28:16 pm
1) With 12V supply, to motor voltage will probably be around 9V [it's that darlington thing]

2) PWM notwithstanding, the motors still get full amplitude (whatever the output is.)

3) 2A DC-DC converters aren't cheap. At that rate, why not just get a 12V motor and do away with the complication?

It's not that I'm "willing to take some risk", there are no easy answers here, something simple, inexpensive, one-size-fits-all UNLESS we go back to the diodes.

So, if "we" have 12V and we lose 3 in the motorshield output, that leaves "us" with 9V.  5V from 9V leaves us with another 4V to lose, approximately 4 diode drops.  [Or get out your wallet. That's simple.]
Dwg attached.
19  Using Arduino / LEDs and Multiplexing / Re: Looking for a good tutorial on using LM3914 with LED bar and an Arduino on: August 29, 2014, 07:37:08 pm
I really need someone to explain how the chip works in a simple way because i am still new to electronics.

My previous submission is very practical, there's a lot of information there.
I mean, what kind of explanation does a "still new to electronics" person need?
How do you feel about hammering out that circuit? A bridge too far?
20  Using Arduino / Motors, Mechanics, and Power / Re: How to power 4.5v DC motor with 12v power supply using dk electonic motorshield? on: August 29, 2014, 07:33:11 pm
Those guys, with their darlington outputs, lose 3-4V (it's load related) anyway.
Maybe there's nothing to worry about, maybe you'll be OK with the limited-range PWM idea, maybe lots of things.

Why do so many cars use them for the 5-speed A/C Blower motor ?

Assuming that's so, I suppose it's because their loads don't change so much as a motor running wheels (uphill, downhill, faster, slower, start and slow down) on the floor or whatever.
Does that seem plausible?


21  Using Arduino / LEDs and Multiplexing / Re: Looking for a good tutorial on using LM3914 with LED bar and an Arduino on: August 28, 2014, 08:31:30 pm
I am still learning so data sheets are a little over my head.

OK
Here's a way (attached.)
22  Using Arduino / Motors, Mechanics, and Power / Re: How to power 4.5v DC motor with 12v power supply using dk electonic motorshield? on: August 28, 2014, 08:11:02 pm
If it was a couple of volts then I'd say, "definitely pad it with diodes", but that might be pushing the envelope in this case.
But then again, that's better than resistors.
So, yes, 7 or 8 resistors diodes, and both motors could feed off that.

Be that as it may or may not: nothing is known of the "dk electronic motorshield", so we're just shooting into the dark.
That's the context for deciding what to do.
23  Using Arduino / General Electronics / Re: LM324 output to Arduino interrupt not working correctly (with schematic) on: August 28, 2014, 08:00:36 pm
Aren't you supposed to "post your code" or something?
Just a thought - I must go (back) to sleeeeeeep.
24  Using Arduino / General Electronics / Re: PWM drive MOSFET not working properly. on: August 28, 2014, 07:56:17 pm
Quote
Should I just put all grounds on the power supply (-) port?

Yes, connect the Gnds.
25  Using Arduino / Motors, Mechanics, and Power / Re: How to power 4.5v DC motor with 12v power supply using dk electonic motorshield? on: August 28, 2014, 07:50:52 pm
We've reasoned together on this "dropping resistor" proposal once before as I recall.
What's the effect of the "dropping resistor" when the motor has little work to do and, by implication, draws less current?
26  Using Arduino / Programming Questions / Re: error does not name a type on: August 24, 2014, 06:21:00 pm
"The library file MFRC522.h has a wealth of useful info. Please read it."

Oh, and make certain that it has been placed in your Libraries folder.

27  Using Arduino / General Electronics / Re: [Beginner] How can I use the Arduino as a switch? on: August 24, 2014, 04:49:38 pm
Having B and J is redundant, it's junction transistor or bipolar transistor.
[So saith I.]
28  Using Arduino / LEDs and Multiplexing / Re: Bluetooth HC-06 control RGB LedDiode, Help in Serial read command. on: August 24, 2014, 02:28:56 pm
http://forum.arduino.cc/index.php?topic=262655.msg1853066#msg1853066

(Cross-posting is "bad form".)
29  Using Arduino / Programming Questions / Re: Help with a button press duration sketch... on: August 24, 2014, 02:15:52 pm

Code:
//  pirtrippoint5sec
//
//  wait for 5 secs of constant detection
//  ** works  07APR2014 **

unsigned long refTime;
unsigned long trippoint;

const long threshold = 5000;

byte DET;
const byte pirPin = 8;
const byte ledPin = 13;

void setup ()
{
  //pirPin is INPUT by default, BUT use ExtPullup
  pinMode (ledPin,OUTPUT);
  digitalWrite (ledPin,LOW);
}

void loop ()
{
  DET = digitalRead(pirPin);
  if (DET == 1)  // inactive
  {
    refTime = millis();
    trippoint = refTime;
  }
  else   // Active Low
  {
    pir_active();
  }
}

void pir_active ()
{
  trippoint = millis();
  if ((trippoint-refTime) > threshold)
  {
    digitalWrite(ledPin,HIGH);
  }
}
30  Using Arduino / General Electronics / Re: Arduino AC Voltage Dimmer (Variable Resistor? PWM?) on: August 21, 2014, 08:09:48 pm
It could run on 65V DC, too.
What's your 65V AC source?

If you need VAC then you need a Triac.

You could use a 120/220v transformer, put 120 into the 220 side and get 60 or so out.
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