Ver 1.0 Manual

High Power RGB LED Shield Ver 1.0 Manual

Description

High Power RGB LED Shield for Arduino will drive power LEDs. The shield provides three independent channels which is ideal for RGB LED to make beautiful colors. Of course, you can connect white LEDs to shine your room as well. High Power RGB LED Shield can drive various power LEDs such as Philips Luxeon, Philips Lumiled, Cree XP-E, Cree XP-G, OSRAM Dragon, OSRAM Ostar, power LEDs from dealextream, and many others.

The shield can be powered by broad range of voltage (6 – 42V) and can power up 100 – 700mA LEDs. It supports two different dimming methods to control brightness of LEDs. Analog dimming has best energy efficiency while PWM dimming is better for RGB color mixing. The shield can be stacked as many as you want (theoretically 100) while it use only two pins from Arduino regardless of number of the shield stacked. The shield can be operated without Arudino.

Features

  • 700mA 3 channel LED driver based on lt3496 (buck configuration)
  • I2C controlled 3 channels PWM for dimming leds
  • Dynamically adjustable current output (can be used for analog dimming as well)
  • 42V input, 36V output. Drive up to 40W LEDs
  • 5V switching power supplier (up to 42V input)
  • Many shields can be stacked and only use two I2C pins (A4, A5) from arduino
  • Standalone operation without arduino
  • Optional temp sensor for monitor led temp and PCB temp

Application

  • Interactive High Power LED lighting

Getting Started

The shield needs to be connected to the Arduino to set maximum current to LEDs and operation frequency. Then connect your power LEDs and power the shield.

Shield Layout

HP_RGB_LED_Shield_V1_layout

Connecting to Arduino

The shield designed to be stacked on top of the Arduino as any other shields for Arduino. When single shield is used, user may use regular 0.1 inch spaced header pins to stack on top of Arduino. When multiple shields are stacked on the top of each other, it is recommended to use stackable pins (http://www.sparkfun.com/products/10007). The shield can be stacked up to 100.

When the shield is used separate from Arduino, Analog In 4, 5, and GND need to be connected to Arduino for I2C communication. You can supply 5V power from Arduino, if the shield is not connected to power adaptor.

The shield use standard I2C communication protocol for entire operation. Any microcontroller or computer that has I2C master function can be used with shield. Once the shield is configured, the shield may operate as stand-alone.

Setting for Basic Operations

The proper maximum current to LED needs to be set depending on LEDs that the shield drives. Manufactures of LEDs have specification for maximum operation current for a LED. Generally, so called 1W white LED and 3W RGB LED have 350mA operation current. Philips Lumiled, Cree XP-E , and Osram Gold Dragon have 700mA maximum operation current. For details, please check the datasheet of the LED from the manufactures.

Download the shield library from the Google code(http://code.google.com/p/neuroelec/downloads/list) and install it to your sketch directory. You will find an example file that has the example for maximum current settings for each channel and operation frequency as follow. For the frequency, please check “Input Voltage and Operating Frequency” section.

   1: #include "HPRGB.h"
   2: #include <Wire.h>
   3:  
   4: HPRGB ledShield; // default mcp4728 id(0) and default czyRGB address(9)
   5:  
   6: void setup()
   7: {
   8:   ledShield.begin();
   9:   ledShield.setCurrent(350,350,350); // set maximum current for channel 1-3 (mA)
  10:   ledShield.setFreq(600);// operation frequency of the LED driver (KHz)
  11:   ledShield.eepromWrite();// write current settings to EEPROM
  12:   delay(100); // wait for EEPROM writing
  13: }
  14:  
  15:  
  16: void loop()
  17: {
  18:   ledShield.goToRGB(255,255,255); delay (3000); //go to RGB color (white) now
  19:   ledShield.fadeToRGB(255,0,0); delay (3000); //fade to RGB color (red)
  20:   ledShield.fadeToRGB(0,255,0); delay (3000);//fade to RGB color (green)
  21:   ledShield.fadeToRGB(0,0,255); delay (3000); //fade to RGB color (blue)
  22:   ledShield.fadeToHSB(0,0,255); delay (3000); //fade to HSV color (Hue, Saturation, brightness)
  23:   ledShield.playScript(0,255,0); delay (10000);//play script 0 for 255 times
  24:   ledShield.stopScript(); //play script 0 for 255 times
  25: }

Connecting LEDs to the Shield

HP_RGB_LED_Shield_V1_LED_connection

Connector to LEDs are labeled as R (red, channel 1), G (green, channel 2), and B (blue, channel 3). When White LEDs are connected, just channel number is matter. Each channel has label for polarity (+,-). Right port of the channel is the GND. Connect the LEDs properly, otherwise you may damage LEDs.

When multiple LEDs connected to a channel, LEDs are recommended to connect in series. If multiple LEDs are configure as parallel, LEDs in parallel have to be exact same types of LEDs. Slight differences in voltage drop of LEDs may cause damage, so parallel connection of LEDs is highly undesirable.

Total 10 LEDs per channel can be connected to the shield depending on types of LED. The Input Voltage to LED is required to be higher than total output voltage to LED. “Input Voltage and Operating Frequency” section has detailed information for input voltage ranges.

Once LEDs are securely connected to shield, you can connect the power to the shield.

Power supply for the shield

HP_RGB_LED_Shield_V1_VINjumper

The shield has a standard power connector (2.1mm pole) which should fit with majority of AC wall adaptors. The shield has on-board 300mA, 5V switching power supply and can be powered by 6-42V DC wall adaptor. Optionally, users may connect power adaptor to Arduino power jack, if input voltage is lower than 12V. The shield will get power from VIN pin of Arduino.

To protect Arduino from high voltage, the shield has a protection diode. VIN in the shield is not available in Arduino while the shield supplies 5V (about 200mA) to Arduino. Users may override protection diode for stacking shields using a jumper (JP1) next to the VIN pin. When the jumper is connected, users may consider bending or cutting VIN pin to Arduino for protection.

Dimming LEDs

The shield supports two dimming methods (analog and PWM dimming). User can choose one of them based on needs.

For general dimming such as RGB color mixing, PWM is recommended. The ATTINY microprocessor on the shield functions as an I2C PWM controller with cyzRGB firmware. The cyzRGB use same command as Blinkm. For detailed commands, please check the cyzRGB wiki (http://code.google.com/p/codalyze/wiki/CyzRgb).

Input Voltage and Operating Frequency

LED driver part of the shield is buck switching regulator which requires higher input voltage than output voltage. Please find proper input voltage and operation frequency based on LEDs (Vf = 3.0 – 3.65).

Following table has recommended input voltage and recommended operating frequency based on number of LEDs in series per channel

If higher input voltage is used than recommend input voltage, operation frequency may require being higher than recommended operation frequency. Users can calculate exact operation frequency from the spreadsheet.

Current Rating Number of LEDs Input Voltages RecommandedInput Voltage RecommandedOperation Frequency
350mA 1 6-42V 9 (>0.8A) 600KHz
350mA 2 8-42V 9 (>1.2A) 600KHz
350mA 3 12-42V 12 (>1.2A) 600KHz
350mA 4 16-42V 18 (>1.0A) 800KHz
350mA 5 21-42V 24 (>1.0A) 1200KHz
350mA 6 26-42V 28 (>1.0A) 1300KHz
350mA 7 31-42V 32 (>1.0A) 1500KHz
350mA 8 36-42V 36 (>1.0A) 1700KHz
700mA 1 6-42V 9 (>1.2A) 330KHz
700mA 2 8-42V 9 (>2.0A) 330KHz
700mA 3 12-42V 12 (>2.2A) 330KHz
700mA 4 16-42V 18 (>1.9A) 400KHz
700mA 5 20-42V 24 (>1.8A) 600KHz
700mA 6 24-42V 24 (>2.1A) 600KHz

Efficiency and Thermal Consideration

The shield has very efficient LED drivers which normally has 85-95% efficiency. Even though it is driving power LEDs at high efficiency, it will still dissipates heat. For example, when the shield power 30 watts of LEDs, it dissipate about 3 watts of heat from the shield at 90% efficiency. The shield gets warm or slightly hot (120-140ºF, 50-60ºC) which is completely normal. If users want to connect more than 40W of LEDs to the shield, shield require a heat sink on the top or bottom of the LED driver chip and temperate of the chip need to be monitored (should be lower than 100ºC). Since operation frequency of the LED driver effect heat dissipation, low operation frequency has to be used.

Programming ATTINY85 on the Shield

The shield has a latest cyzRGB firmware. User may use other version of cyzRGB firmware or custom firmware. The ATTINY can be easily programmed with Arduino ISP example. There is a ICSP header which has standard pin layout as Arduino ICSP. For detail, check a tutorial at http://arduino.cc/en/Tutorial/ArduinoISP

HP_RGB_LED_Shield_V1_ATtiny85

Stacking Shields

The shield is designed for easy of stacking. Regardless of the number of stacked shield, the shield use only two pins from the Arduino. Up to 8 shields can be stacked when analog dimming is used. When analog dimming is not required, 100 shields can be stacked theoretically. For stacking shield, I2C addresses of the chips need to be changed. There are two I2C chips, attiny85 and mcp4728 on the shield. Address of both can be easily programmed with the shield library. However, changing address of mcp4728 requires jumper for address change command. As in the image, LDAC jumper is normally connected to – (GND). For the address change command of mcp4728, the jumper needs to connect to + (pin D8). After changing LDAC jumper, load address change example from the shield library. It will let you change the address of mcp4728. Once address change is done, LDAC jumper need to be – (GND) again for normal operation.

HP_RGB_LED_Shield_V1_LDACjumper

Temperature Sensing

If you have the shield with temperature sensor(TMP421), users can acquire PCB and remote temperatures. TMP421 is located close to LT3496, so local temperature is co-related with LT3496 temperature (about 5-10 Celcius degree lower than LT3496 temperature).  The shield come with five remote temperature sensors (2N3906). As in figure below, tie base and collector and connect it to “N” of the shield. The emitter of 2N3906 is connected to “P”. It is recommended to put resistors (50 ohms) and a capacitor(100pF) as a filter. For detail, please check the datasheet. The shield library has couple of commend to acquire temperatures, please check “temperature example” from the shield library.

HP_RGB_LED_Shield_V2_TPMtransistor

Online Resources

  • Shield Library

http://code.google.com/p/neuroelec/downloads/list

  • CYZ_RGB Firmware

http://code.google.com/p/codalyze/wiki/CyzRgb

  • Shield Design Explanation

http://neuroelec.com/2011/02/designing-rgb-led-shield-1-led-driver/

http://neuroelec.com/2011/02/designing-rgb-led-shield-2-dimming-leds/

http://neuroelec.com/2011/02/designing-rgb-led-shield-3-power-and-temp-sensor/

  • Shield Schematics and Design

http://code.google.com/p/neuroelec/source/browse/#svn%2Ftrunk%2FHP_RGB_LED_Shield

Manual Revision History

3/24/2011 Add temperature sensing section.

3/15/2011 Change frequency table, add link to google spreadsheet.

3/10/2011  fix ICSP labels, add efficiency and shield stacking section.

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