LED ring light for Velleman K8200 3D printer

K8200 3D Printer K8200 - Your printer, creations, and ideas for imp
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LED ring light for Velleman K8200 3D printer

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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.
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 :slight_smile:

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.

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

And here is the source code:

[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);
}[/code]

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

For more details, photos, schematic - please visit my blog: http://ljwinkler.blogspot.com/2014/02/led-ring-light-for-velleman-k8200-3d.html

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Cheers,
LJ