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Thursday 13 February 2014

LED ring light for Velleman K8200 3D printer



This time I would like to present you how I have added a light around the extruder.
Instead of re-inventing the wheel I just bought a simple tent light in Argos (LINK).


It contains 2 rings with white 5mm LEDs and it is battery powered. It takes 3x AA batteries so the maximum voltage is about 4.5V – close enough to onboard 5V. I’m going to drive it using PWM so I’m not worried about exceeding the limits (I’m sure there is a voltage margin in the product design so it will not catch the flames if 4.51V is provided :) 

I’ve created a circular holder for the rings:




To mount the PCB rings – I simply marked all the holes in the PCBs with a tip of soldering iron (mmmmm, that sweet smell of melted PLA :)) and then used some small screws lying around to hold the 2 rings in place.



Then was a time to make some brackets to hold the lights next to the extruder:







To mount it to the Z carriage arm I used clips from my previous design: 
http://ljwinkler.blogspot.com/2014/01/frame-clip-and-locking-pin-for-velleman.html





For the PWM driver I used Atmega328P microcontroller with an Arduino bootloader. It is a bit overkill using a microcontroller for such a simple purpose but it leaves me an open window for future modifications and it was also very quick to set up from parts I had. The other big advantage of this solution comes when a small tweaks are required – it just means changing the source code and re-uploading it back to the microcontroller.
I used one of the analogue inputs (A0 - pin 23) to read value of the potentiometer and one of the PWM outputs (D10 - pin 16) to drive a transistor that controls the LEDs. Atmega328P has a 10 bit A/D converter, therefore it can read 1024 positions of the potentiometer (0-1023). However, the PWM output is only 8-bit (0-255). I have modified the range to be 3-255 – so turning the potentiometer to its edge will turn off the lights completely. I have also added averaging of last 10 readings to prevent flickering.
A 4-pin header (Reset, RxD, TxD, GND) was added for programming purposes.
As a power supply I used the main controller board, pins marked as +5V and GND from the header J1 located in the corner of the controller board.

Here is a quick schematic:

 

List of components used:
  • 1x ATmega328P with Arduino bootloader
  • 1x BUF644 NPN transistor
  • 1x 16MHz crystal
  • 2x 22p ceramic capacitor
  • 1x 10k resistor
  • 1x 100R resistor
  • 1x 10k potentiometer


I have soldered it on a single layer protoboard:


Then I have designed a base for the PCB.
I have created small support elements keeping the board raised 5 mm and holding it in place by two M3 screws in the corners. The whole unit is mounted on the main controller board mount (described here: http://ljwinkler.blogspot.ie/2014/01/controller-board-mount-for-velleman.html)




Afterwards I have created a holder for the potentiometer. I have redesigned one of my clips - this time I used the flat one as there are wires running underneath.




And here is the source code:


// Arduino program for PWM LED lighting
// Copyright 2014 - LJ Winkler (lwinkler247@gmail.com)
//
//-------------------------------------------------------------------------//
// Permission is hereby granted, free of charge, to any person             //
// obtaining a copy of this software and associated documentation files    //
// (the "Software"), to deal in the Software without restriction,          //
// including without limitation the rights to use, copy, modify, merge,    //
// publish, distribute, sublicense, and/or sell copies of the Software,    //
// and to permit persons to whom the Software is furnished to do so,       //
// subject to the following conditions:                                    //
//                                                                         //
// The above copyright notice and this permission notice shall be          //
// included in all copies or substantial portions of the Software.         //
//                                                                         //
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,         //
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF      //
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  //
// IN NO EVENT SHALL THE AUTHOR OR COPYRIGHT HOLDERS BE LIABLE FOR ANY     //
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,    //
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE       //
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                  //
//-------------------------------------------------------------------------//

/*
 * pin A0 - PWM pot input
 * pin 10 - PWM output
 */

const int numReadings = 10;
const int potINpin = A0;
const int pwmOUTpin = 10;
int potValue = 0;
int pwmValue = 0;
int readings[numReadings];
int index = 0;
int total = 0;
int average = 0;

void setup() {
  pinMode(pwmOUTpin, OUTPUT);
  pinMode(potINpin, INPUT);
  for (int thisReading = 0; thisReading < numReadings; thisReading++){
    readings[thisReading] = 0;
  }   
}

void loop() {
  total = total - readings[index];        
  readings[index] = analogRead(potINpin);
  total = total + readings[index];      
  index = index + 1;                   
  if (index >= numReadings){
    index = 0;                          
  }
  average = total / numReadings;        
  pwmValue = map(average, 0, 1023, 255, 0); 
  if(pwmValue<3){
    pwmValue=0;
  }
  analogWrite(pwmOUTpin, pwmValue);
  delay(1);
}




To download the files - visit my profile on Thingiverse (http://www.thingiverse.com/ljwinkler/designs) or use direct links below:



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