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46  Topics / Science and Measurement / Re: Using PWM externally and getting triggered on edge on: September 03, 2014, 11:09:09 am
And just what is creating these high and low rising edges? How quickly?  Too little info
47  Topics / Science and Measurement / Re: Arduino Uno R3 as miliVolt meter? on: September 03, 2014, 11:06:40 am
I don't care about the damage to the Arduino, I'm worried about the damage to you.

When you measure the current over a shunt, the Arduino is connected to the mains. That can go bad very quick, for example when you connect a computer to the usb of the Arduino. I mean : when you really want to use a shunt, you should wear rubber gloves and boots, and have eye protection, and a fire extinguisher nearby.
It is safer to use a current transformer.

This website is all about measuring the mains : http://openenergymonitor.org/emon/
This is such an current transformer : http://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface
But there is a lot more information on that site.

Using the internal voltage reference is more accurate for lower voltages.
http://arduino.cc/en/Reference/AnalogReference


Did I read something completely different to what you read?

I read 50millivolts  ....


So are we measuring mains? In which a CT is used... I think those acs current measuring ic's handle AC current

48  Using Arduino / General Electronics / Re: NPN Transistor As Switch For Vin Pin on: September 02, 2014, 07:26:12 pm
http://m.instructables.com/id/Automatically-water-your-small-indoor-plant-using-/?ALLSTEPS


Needs banning....


The transistor will suck up max current from the Arduino via it's base ... I'm amazed the Arduino is not dead from excessive current draw..




Stick a 1k resistor between base of the transistor and the pin out from arduino.
49  Using Arduino / General Electronics / Re: Ohm's Law. on: September 02, 2014, 07:20:31 pm
It's C at fault here...

  • is the /first/ element of a C array.
  • [1] is the first element In a pascal array.

    1 - 1024  as there are 1024 elements in a 1k array (pascal style)
    0-1023 still 1024 elements / 1k.



    Blame C.. for the array type..

    Oh and for people wondering about arrayval
  • this was used to store the length of the array... but was made redundant in Delphi.
50  Using Arduino / Installation & Troubleshooting / Re: Burnt Arduino Uno? on: August 31, 2014, 09:39:09 pm
How you powering the servo?
51  Using Arduino / General Electronics / Re: Ohm's Law. on: August 31, 2014, 06:01:48 am
No no all is good... ohms law was taught to me via the triangle method

V
IR


Cover one to get the other, I've never used Ohms/Volts only Volts/Ohms so that triangle was lying....

Noone's using ohms/volts!  buffer is a pure number ratio, so we have ohms/number.
In other words the resistance ratio is the same as the voltage ratio.
.


Good! I thought I was going mad .....   thank you clearing that up.
52  Using Arduino / Project Guidance / Re: use arduino to control an adjustable boost converter? on: August 30, 2014, 07:08:08 pm
If you can get > 10 amps from two lithium batteries. ..

I'm betting you'll have a few minutes not 10-15... what's the capacity? The best I've seen is around 1a/h unless you spend big bucks.
53  Using Arduino / General Electronics / Re: Ohm's Law. on: August 30, 2014, 06:53:05 pm
{ sad, resigned sigh}
Code:
Vout = (5.0 / 1024.0) * raw;

Not my code, copy and paste job.
54  Using Arduino / Project Guidance / Re: use arduino to control an adjustable boost converter? on: August 30, 2014, 11:47:21 am
2 lithium 4.2v batteries

Adjustable to 10amps at 10v.....

100watts from 2 lithium batteries (before conversion loss)
55  Using Arduino / General Electronics / Re: Ohm's Law. on: August 30, 2014, 11:38:43 am
No no all is good... ohms law was taught to me via the triangle method

V
IR


Cover one to get the other, I've never used Ohms/Volts only Volts/Ohms so that triangle was lying....
56  Using Arduino / General Electronics / Ohm's Law. on: August 30, 2014, 09:00:52 am
Code:
int analogPin = 0;     // potentiometer wiper (middle terminal) connected to analog pin 3
                       // outside leads to ground and +5V
int raw = 0;           // variable to store the raw input value
int Vin = 5;           // variable to store the input voltage
float Vout = 0;        // variable to store the output voltage
float R1 = 10;         // variable to store the R1 value
float R2 = 0;          // variable to store the R2 value
float buffer = 0;      // buffer variable for calculation

void setup()
{
  Serial.begin(9600);             // Setup serial
  digitalWrite(13, HIGH);         // Indicates that the program has intialized
}

void loop()
{
  raw = analogRead(analogPin);    // Reads the Input PIN
  Vout = (5.0 / 1023.0) * raw;    // Calculates the Voltage on th Input PIN
  buffer = (Vin / Vout) - 1;
  R2 = R1 / buffer;
  Serial.print("Voltage: ");      //
  Serial.println(Vout);           // Outputs the information
  Serial.print("R2: ");           //
  Serial.println(R2);             //
  delay(1000);
}

While not strictly a programming question hence why i'm posting it here..

Now, i'm a little confused here...

Code:
  Vout = (5.0 / 1023.0) * raw;    // Calculates the Voltage on th Input PIN
  buffer = (Vin / Vout) - 1;
  R2 = R1 / buffer;


I simplified it down to this...

5v  --------~~~~~100ohms~~~~~----------(2.5v)-----------~~~~(Unknown Resistor)~~~~------------GND

Vout =  (5/2.5)-1 = 1
Unknown Resistor = 100/1 =  100

am i missing something or is that correct?
57  Community / Bar Sport / Gas carrying charged particles on: August 28, 2014, 11:22:13 am
Basically I was thinking 2 balloons full of gas that  carries charge and make balloon capacitors?

I googled found little. .

58  Using Arduino / General Electronics / Re: 240vac Aussie Plug Wiring. on: August 26, 2014, 05:14:08 am
Ugh....

The point of this question is to find out if it matters which way round it goes...

(I'm chopping the plugs off of them all if you must know....)
59  Using Arduino / General Electronics / Re: Laser Woes on: August 25, 2014, 08:19:28 pm
I've seen toy rc cars with capacitors across the motor, i presume it's there to prevent a high voltage from the collapsing magnetic field ?
60  Using Arduino / General Electronics / 240vac Aussie Plug Wiring. on: August 25, 2014, 08:11:08 pm


Active
Neutral
Earth

That's your Aussie Plug 240vac.

Now most of the Xmas lights (10m 100 LED ropes) i'm a little concerned with how i should wire these EU (2 pin) plugs.... does it matter which way it's wired? (since there's no Earth)




Now these cheap LED rope light plugs...
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