Hello all,
Firstly I hope that I am posting in close to the right section.
I am new to Arduino and came across this sketch for Coffee-cup Color Mixer: Code for mixing and reporting PWM-mediated color on this forum. http://arduino.cc/hu/Tutorial/LEDColorMixerWith3Potentiometers
I wish to try this project out but seeing as there is no schematic provided (I realise "it's not rocket science" as they say…) would I be correct in assuming that the three (10k ? ) centre pins of the pots are connected to analog pins 0, 1, and 2 with 220 ? resistors (on the ground lead ? ) and two outer pot pins to 5V and analog ground respectively. LED's anodes connected to digital pins 9, 10 and 11 and cathodes to digital earth. Also presumably there are 1K ? resistors on the LED anodes (anode in this application being positive ?)
Also presumably on the Uno R2 the digital ground is the pin next to digital pin 13 whereas the two grounds on the other side of the board, between 5V and vin are anolog grounds ?
As I stated I am a raw beginner at all this and hope that someone has the time and inclination to help me with this.
Thanks for reading Pedro147
There is only one ground on an arduino they are connected to the same point.
1K sounds high for a LED's seriese resistor, use 220R.
No need to put that 220R resistor from analogue input to ground.
Good luck.
Grumpy_Mike:
There is only one ground on an arduino they are connected to the same point.
True, however it is good practice to dedicate one of the ground pins as "analog ground" and use it to connect the ground side of any sensors or filtering capacitors attached to analog inputs. Connect output devices and power using the remaining ground pins. The purpose of this is to prevent noise induced on the ground wire when switching output devices from feeding back to the analog inputs. I have found that even switching a few LEDs using a common ground line affects the analog readings.
Wires have inductance, and the change of current through an inductance (e.g. when a device is switched on or off) induces a voltage across it. If the current is large or the connections poor, then resistance plays a part as well.