Planet Arduino

Use the Texas Instruments TLC5940 16-Channel LED Driver IC with Arduino in Chapter 57 of our Arduino Tutorials. The first chapter is here, the complete series is detailed here.

Introduction

Today we are going to examine the Texas Instruments TLC5940 16-channel LED driver IC. Our reason for doing this is to demonstrate another, easier way of driving many LEDs – and also servos.  First up, here is a few examples of the TLC5940

The TLC5940 is available in the DIP version above, and also surface-mount. It really is a convenient part, allowing you to adjust the brightness of sixteen individual LEDs via PWM (pulse-width modulation) – and you can also daisy-chain more than one TLC5940 to control even more.

During this tutorial we’ll explain how to control one or more TLC5940 ICs with LEDs and also look at controlling servos. At this point, please download a copy of the TLC5940_data_sheet (.pdf) as you will refer to it through this process. Furthermore, please download and install the TLC5940 Arduino library by Alex Leone which can be found here. If you’re not sure how to install a library, click here.

Build a TLC5940 demonstration circuit

The following circuit is the minimum required to control sixteen LEDs from your Arduino or compatible. You can use it to experiment with various functions and get an idea of what is possible. You will need:

• An Arduino Uno or compatible board
• 16 normal, everyday LEDs that can have a forward current of up to 20 mA
• a 2 kΩ resistor (give or take 10%)
• a 0.1uF ceramic and a 4.7uF electrolytic capacitor

Take note of the LED orientation – and remember the TLC5940 is a common-anode LED driver – so all the LED anodes are connected together and then to 5V:

For this particular circuit, you won’t need an external 5V power supply – however you may need one in the future. The purpose of the resistor is to control the amount of current that can flow through the LEDs. The required resistor value is calculated with the following formula:

R = 39.06 / Imax

where R (in Ohms)  is the resistor value and Imax (in Amps) is the maximum amount of current you want to flow through the LEDs. For example, if you have LEDs with a 20 mA forward current – the resistor calculation would be:

R = 39.06 / 0.02 = 1803 Ohms.

Once you have the circuit assembled – open up the Arduino IDE and upload the sketch BasicUse.pde  which is in the example folder for the TLC5940 library. You should be presented with output similar to what is shown in the following video:

Controlling the TLC5940

Now that the circuit works, how do we control the TLC5940? First, the mandatory functions – include the library at the start of the sketch with:

#include "Tlc5940.h"

and then initialise the library by placing the following into void setup():

Tlc.init(x);

x is an optional parameter – if you want to set all the channels to a certain brightness as soon as the sketch starts, you can insert a value between 0 and 4095 for x in the Tlc.init() function.

Now to turn a channel/LED on or off. Each channel is numbered from 0 to 15, and each channel’s brightness can be adjusted between 0 and 4095.

This is a two-part process…

First – use one or more of the following functions to set up the required channels and respective brightness (PWM level):

Tlc.set(channel, brightness);

For example, if you wanted to have the first three channels on at full brightness, use:

Tlc.set(0, 4095);
Tlc.set(1, 4095);
Tlc.set(2, 4095);

The second part is to use the following to update the TLC5940 with the required instructions from part one:

Tlc.update();

If you want to turn off all channels at once, simply use:

Tlc.clear();

You don’t need to call a TLC.update() after the clear function. The following is a quick example sketch that sets the brightness/PWM values of all the channels to different levels:

#include "Tlc5940.h"
void setup()
{
  Tlc.init(0); // initialise TLC5940 and set all channels off
}

void loop()
{
  for (int i = 0; i < 16; i++)
  {
    Tlc.set(i, 1023);
  }
  Tlc.update();
  delay(1000);
  for (int i = 0; i < 16; i++)
  {
    Tlc.set(i, 2046);
  }
  Tlc.update();
  delay(1000);
  for (int i = 0; i < 16; i++)
  {
    Tlc.set(i, 3069);
  }
  Tlc.update();
  delay(1000);
  for (int i = 0; i < 16; i++)
  {
    Tlc.set(i, 4095);
  }
  Tlc.update();
  delay(1000);
}

and the sketch in action:

The ability to control individual brightness for each channel/LED can also be useful when controlling RGB LEDs – you can then easily select required colours via different brightness levels for each element.

Using two or more TLC5940s

You can daisy-chain quite a few TLC5940s together to control more LEDs. First – wire up the next TLC5940 to the Arduino as shown in the demonstration circuit – except connect the SOUT pin (17) of the first TLC5940 to the SIN pin (26) of the second TLC5940 – as the data travels from the Arduino, through the first TLC5940 to the second and so on. Then repeat the process if you have a third, etc. Don’t forget the resisotr that sets the current!

Next, open the file tlc_config.h located in the TLC5940 library folder. Change the value of NUM_TLCS to the number of TLC5940s you have connected together, then save the file and also delete the file Tlc5940.o also located in the same folder. Finally restart the IDE. You can then refer to the channels of the second and further TLC5940 sequentially from the first. That is, the first is 0~15, the second is 16~29, and so on.

Controlling servos with the TLC5940

As the TLC5940 generates PWM (pulse-width modulation) output, it’s great for driving servos as well. Just like LEDs – you can control up to sixteen at once. Ideal for creating spider-like robots, strange clocks or making some noise. When choosing your servo, ensure that it doesn’t draw more than 120 mA when operating (the maximum current per channel) and also heed the “Managing current and heat” section at the end of this tutorial. And use external power with servos, don’t rely on the Arduino’s 5V line.

To connect a servo is simple – the GND line connects to GND, the 5V (or supply voltage lead) connects to your 5v (or other suitable supply) and the servo control pin connects to one of the TLC5940′s outputs. Finally – and this is important – connect a 2.2kΩ resistor between the TLC5940 output pin(s) being used and 5V.

Controlling a servo isn’t that different to an LED. You need the first two lines at the start of the sketch:

#include "Tlc5940.h"
#include "tlc_servos.h"

then the following in void setup():

tlc_initServos();

Next, use the following function to select which servo (channel) to operate and the required angle (angle):

tlc_setServo(channel, angle);

Just like the LEDs you can bunch a few of these together, and then execute the command with:

Tlc.update();

So let’s see all that in action. The following example sketch sweeps four servos across 90 degrees:

#include "Tlc5940.h"
#include "tlc_servos.h"

void setup()
{
  tlc_initServos();  // Note: this will drop the PWM freqency down to 50Hz.
}

void loop()
{
  for (int angle = 0; angle < 90; angle++) {
    tlc_setServo(0, angle);
    tlc_setServo(1, angle);
    tlc_setServo(2, angle);
    tlc_setServo(3, angle);    
    Tlc.update();
    delay(5);
  }
  for (int angle = 90; angle >= 0; angle--) {
    tlc_setServo(0, angle);
    tlc_setServo(1, angle);
    tlc_setServo(2, angle);
    tlc_setServo(3, angle);    
    Tlc.update();
    delay(5);
  }
}

And the following video captures those four servos in action:

If you servos are not rotating to the correct angle – for example you ask for 180 degrees and they only rotate to 90 or thereabouts, a little extra work is required. You need to open the tlc_servos.h file located in the TLC5940 Arduino library folder and experiment with the values for SERVO_MIN_WIDTH and SERVO_MAX_WIDTH. For example change SERVO_MIN_WIDTH from 200 to 203 and SERVO_MAX_WIDTH from 400 to 560.

Managing current and heat 

As mentioned earlier, the TLC5940 can handle a maximum of 120 mA per channel. After some experimenting you may notice that the TLC5940 does get warm – and that’s ok. However there is a maximum limit to the amount of power that can be dissipated before destroying the part. If you are just using normal garden-variety LEDs or smaller servos, power won’t be a problem. However if you’re planning on using the TLC5940 to the max – please review the notes provided by the library authors.

Conclusion

Once again you’re on your way to controlling an incredibly useful part with your Arduino. Now with some imagination you can create all sorts of visual displays or have fun with many servos. And if you enjoyed the tutorial, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

The post Tutorial – Arduino and the TLC5940 PWM LED Driver IC appeared first on tronixstuff.

Use the Texas Instruments TLC5940 16-Channel LED Driver IC with Arduino in Chapter 57 of our Arduino Tutorials. The first chapter is here, the complete series is detailed here.

Introduction

Today we are going to examine the Texas Instruments TLC5940 16-channel LED driver IC. Our reason for doing this is to demonstrate another, easier way of driving many LEDs – and also servos.  First up, here is a few examples of the TLC5940

The TLC5940 is available in the DIP version above, and also surface-mount. It really is a convenient part, allowing you to adjust the brightness of sixteen individual LEDs via PWM (pulse-width modulation) – and you can also daisy-chain more than one TLC5940 to control even more.

During this tutorial we’ll explain how to control one or more TLC5940 ICs with LEDs and also look at controlling servos. At this point, please download a copy of the TLC5940_data_sheet (.pdf) as you will refer to it through this process. Furthermore, please download and install the TLC5940 Arduino library by Alex Leone which can be found here. If you’re not sure how to install a library, click here.

Build a TLC5940 demonstration circuit

The following circuit is the minimum required to control sixteen LEDs from your Arduino or compatible. You can use it to experiment with various functions and get an idea of what is possible. You will need:

• An Arduino Uno or compatible board
• 16 normal, everyday LEDs that can have a forward current of up to 20 mA
• a 2 kΩ resistor (give or take 10%)
• a 0.1uF ceramic and a 4.7uF electrolytic capacitor

Take note of the LED orientation – and remember the TLC5940 is a common-anode LED driver – so all the LED anodes are connected together and then to 5V:

For this particular circuit, you won’t need an external 5V power supply – however you may need one in the future. The purpose of the resistor is to control the amount of current that can flow through the LEDs. The required resistor value is calculated with the following formula:

R = 39.06 / Imax

where R (in Ohms)  is the resistor value and Imax (in Amps) is the maximum amount of current you want to flow through the LEDs. For example, if you have LEDs with a 20 mA forward current – the resistor calculation would be:

R = 39.06 / 0.02 = 1803 Ohms.

Once you have the circuit assembled – open up the Arduino IDE and upload the sketch BasicUse.pde  which is in the example folder for the TLC5940 library. You should be presented with output similar to what is shown in the following video:

Controlling the TLC5940

Now that the circuit works, how do we control the TLC5940? First, the mandatory functions – include the library at the start of the sketch with:

#include "Tlc5940.h"

and then initialise the library by placing the following into void setup():

Tlc.init(x);

x is an optional parameter – if you want to set all the channels to a certain brightness as soon as the sketch starts, you can insert a value between 0 and 4095 for x in the Tlc.init() function.

Now to turn a channel/LED on or off. Each channel is numbered from 0 to 15, and each channel’s brightness can be adjusted between 0 and 4095.

This is a two-part process…

First – use one or more of the following functions to set up the required channels and respective brightness (PWM level):

Tlc.set(channel, brightness);

For example, if you wanted to have the first three channels on at full brightness, use:

Tlc.set(0, 4095);
Tlc.set(1, 4095);
Tlc.set(2, 4095);

The second part is to use the following to update the TLC5940 with the required instructions from part one:

Tlc.update();

If you want to turn off all channels at once, simply use:

Tlc.clear();

You don’t need to call a TLC.update() after the clear function. The following is a quick example sketch that sets the brightness/PWM values of all the channels to different levels:

#include "Tlc5940.h"
void setup()
{
  Tlc.init(0); // initialise TLC5940 and set all channels off
}

void loop()
{
  for (int i = 0; i < 16; i++)
  {
    Tlc.set(i, 1023);
  }
  Tlc.update();
  delay(1000);
  for (int i = 0; i < 16; i++)
  {
    Tlc.set(i, 2046);
  }
  Tlc.update();
  delay(1000);
  for (int i = 0; i < 16; i++)
  {
    Tlc.set(i, 3069);
  }
  Tlc.update();
  delay(1000);
  for (int i = 0; i < 16; i++)
  {
    Tlc.set(i, 4095);
  }
  Tlc.update();
  delay(1000);
}

and the sketch in action:

The ability to control individual brightness for each channel/LED can also be useful when controlling RGB LEDs – you can then easily select required colours via different brightness levels for each element.

Using two or more TLC5940s

You can daisy-chain quite a few TLC5940s together to control more LEDs. First – wire up the next TLC5940 to the Arduino as shown in the demonstration circuit – except connect the SOUT pin (17) of the first TLC5940 to the SIN pin (26) of the second TLC5940 – as the data travels from the Arduino, through the first TLC5940 to the second and so on. Then repeat the process if you have a third, etc. Don’t forget the resisotr that sets the current!

Next, open the file tlc_config.h located in the TLC5940 library folder. Change the value of NUM_TLCS to the number of TLC5940s you have connected together, then save the file and also delete the file Tlc5940.o also located in the same folder. Finally restart the IDE. You can then refer to the channels of the second and further TLC5940 sequentially from the first. That is, the first is 0~15, the second is 16~29, and so on.

Controlling servos with the TLC5940

As the TLC5940 generates PWM (pulse-width modulation) output, it’s great for driving servos as well. Just like LEDs – you can control up to sixteen at once. Ideal for creating spider-like robots, strange clocks or making some noise. When choosing your servo, ensure that it doesn’t draw more than 120 mA when operating (the maximum current per channel) and also heed the “Managing current and heat” section at the end of this tutorial. And use external power with servos, don’t rely on the Arduino’s 5V line.

To connect a servo is simple – the GND line connects to GND, the 5V (or supply voltage lead) connects to your 5v (or other suitable supply) and the servo control pin connects to one of the TLC5940′s outputs. Finally – and this is important – connect a 2.2kΩ resistor between the TLC5940 output pin(s) being used and 5V.

Controlling a servo isn’t that different to an LED. You need the first two lines at the start of the sketch:

#include "Tlc5940.h"
#include "tlc_servos.h"

then the following in void setup():

tlc_initServos();

Next, use the following function to select which servo (channel) to operate and the required angle (angle):

tlc_setServo(channel, angle);

Just like the LEDs you can bunch a few of these together, and then execute the command with:

Tlc.update();

So let’s see all that in action. The following example sketch sweeps four servos across 90 degrees:

#include "Tlc5940.h"
#include "tlc_servos.h"

void setup()
{
  tlc_initServos();  // Note: this will drop the PWM freqency down to 50Hz.
}

void loop()
{
  for (int angle = 0; angle < 90; angle++) {
    tlc_setServo(0, angle);
    tlc_setServo(1, angle);
    tlc_setServo(2, angle);
    tlc_setServo(3, angle);    
    Tlc.update();
    delay(5);
  }
  for (int angle = 90; angle >= 0; angle--) {
    tlc_setServo(0, angle);
    tlc_setServo(1, angle);
    tlc_setServo(2, angle);
    tlc_setServo(3, angle);    
    Tlc.update();
    delay(5);
  }
}

And the following video captures those four servos in action:

If you servos are not rotating to the correct angle – for example you ask for 180 degrees and they only rotate to 90 or thereabouts, a little extra work is required. You need to open the tlc_servos.h file located in the TLC5940 Arduino library folder and experiment with the values for SERVO_MIN_WIDTH and SERVO_MAX_WIDTH. For example change SERVO_MIN_WIDTH from 200 to 203 and SERVO_MAX_WIDTH from 400 to 560.

Managing current and heat 

As mentioned earlier, the TLC5940 can handle a maximum of 120 mA per channel. After some experimenting you may notice that the TLC5940 does get warm – and that’s ok. However there is a maximum limit to the amount of power that can be dissipated before destroying the part. If you are just using normal garden-variety LEDs or smaller servos, power won’t be a problem. However if you’re planning on using the TLC5940 to the max – please review the notes provided by the library authors.

Conclusion

Once again you’re on your way to controlling an incredibly useful part with your Arduino. Now with some imagination you can create all sorts of visual displays or have fun with many servos. And if you enjoyed the tutorial, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

The post Tutorial – Arduino and the TLC5940 PWM LED Driver IC appeared first on tronixstuff.

Hello everyone!

During July there was another competition which was quite fun, so from August and onwards we shall do it again. The winner ‘S.R.’ won the minor prize so the major prize jackpots into this month. Running these competitions are a way of saying thank you to my readers, and to generate some interaction. So …

All you have to do for a chance to win is the following:

1. Read the blog posts and articles in August, as there will be six questions you will need to answer placed randomly amongst the posts. To keep track, subscribe using one of the methods on the right hand side of this page
2. When you have answers for all six questions, email them to competition@tronixstuff.com
3. If you follow me on twitter (@tronixstuff) and retweet one post in August, you will receive two entries, so put your twitter address in your email.
4. On September the 1st, all the email addresses will be placed in a random draw and one selected. If the entry drawn has all six questions correct, they will win the major prize!
5. If the first entry drawn does not have six correct answers, they will win the minor prize, and the major prize will carry over until September, to be combined with the new major prize.

The prizes!

Major prize

The major prize for August consists of the following:

• One assembled, used JYE Tech Digital Storage Oscilloscope – from the kit review;
• One new pair of 315 MHz wireless data modules, as used in Getting Started with Arduino – Chapter Eleven;
• And something different, the new Texas Instruments MSP430 Launchpad kit, including evaluation board, two MCUs  and the USB cable.

Minor prize

The minor prize for August is John’s Fun with LEDs! pack, consisting of:

• ten each of red, green, yellow and orange 5mm LEDs;
• four RGB 10mm diffused LEDs
• three 74HC595 shift registers
• two Texas Instruments TLC5940 16-channel LED driver ICs
• two LM3914 bar graph/dot driver ICs
• 20 x 560 ohm 1% resistors (they missed the photo call)

Hopefully everyone can have some fun reading about electronics and learning along the way. As with any competition, there are a few rules:

1. If you have won a previous competition, you cannot enter
2. If you know me personally, you cannot enter
3. The prizes carry no warranty, we accept no liability for anything at all that they may cause
4. Prizes only include what is in the photograph, and will be sent via standard airmail free of charge
5. My decision is final
6. You can witness the draw in person with prior arrangement
7. The time used is Australian Eastern Standard Time (GMT: +10)

If you cannot wait for a chance to win, the DSO and and a range of LEDs are available from our friends at Little Bird Electronics.

So keep your eyes peeled and have fun!

Hello readers

Today we are going to examine the Texas Instruments TLC5940 16-channel LED driver IC. My reason for doing this is to demonstrate another, easier way of driving many LEDs as well as LED display modules that are common-anode. If you have a common-cathode display module, you should have a look at the Maxim MAX7219. Moving along, here is the IC:

Another nice big DIP IC. Also available in HTSSOP and QFN packaging. What can this IC do for us? It can control 16 LEDs per IC, and also be cascaded to control more and more, with the display data arriving via a serial line in the same manner as a 74HC595 shift register. Furthermore, another benefit of this IC is that you don’t need matching current-limiting resistors for your LEDs, as this IC is a current sink, in that the current flows from the 5V rail, through the LED, then into the IC. However, it can control the brightness of the LEDs using pulse-width modulation over 4096 steps via software, or using a single resistor.

What is pulse-width modulation? Normally an LED might be on, or off. But if you switch it on and off very quickly, it does not look as bright (as it is not on 100% of the time). If you alter the period of time between on and off, you can alter the perceived brightness of the LED. Here is an example, compare the brightness of the LED bars against the display of the CRO – as the brightness increases, the voltage (amplitude [vertical thickness]) spreads across the entire time period (horizontal axis); as the brightness decreases, the voltage spread across time retreats:

Using the IC is very easy on the hardware front. Here is the data sheet: TLC5940.pdf. The pinout diagram is quite self-explanatory:

Pins OUT0~OUT15 are the current-sink pins for each LED. When one is selected they allow current to flow into the IC from the 5V rail, with the LED in between – turning it on. However it is easier to understand with a practical example, such as this (click to enlarge):

Here we have our Arduino board or compatible sending serial data to the TLC5940 to control sixteen LEDs. The 2k ohm resistor is required to set the maximum current available to flow through the LEDs, thereby adjusting their brightness. Using software you can adjust the brightness with PWM for each LED by itself. Very important: this circuit will need external power into the Arduino or a separate 5V power supply. The circuitry on the breadboard draws up to ~318 mA by itself – running the Arduino from USB only made it somewhat flaky in operation. Here is the circuit in action with an ammeter between the breadboard and 5V out on the Arduino:

Anyhow, let’s get moving once more – here is the assembled demonstration circuit:

For our example, we will be using the Arduino way of doing things. Thankfully (once more) there is a library to make controlling the IC exponentially easier. The library page and download files are available from here; the documentation page is here.  If you need guidance on installing a library, please visit here. However the commands to control the IC are quite simple with the Arduino library.

First of all, include the TLC5940 library, as such:

#include “Tlc5940.h”

Then in void setup(); you create the object using the function:

Tlc.init();

You can insert a number between 0 and 4095 to set the starting PWM (LED brightness) value, however this is optional.

Setting an output for display requires two functions, first Tlc.set(l, p); where l is the output (0~15) and p is the PWM brightness level – then execute Tlc.update(); which sends the command to the IC to be executed. The sketch below is easy to follow and understand the process involved.

Moving forward with the demonstration, here is the sketch  – TLC5940demo.pdf, and the video clip of operation:

When the LEDs are glowing from dim to bright and return, we are altering the PWM value of the LEDs to adjust their brightness. This also occurs during the last operation where the LEDs are operating like the bonnet of KITT.

Well once again that’s enough blinkiness for now, again this is another useful IC that helps simplify things and be creative. As always, avoid the risk of counterfeit ICs  – so please avoid disappointment, support your local teams and buy from a reputable distributor. Living in Australia, mine came from Farnell (part number 1226306). So have fun!

Remember, if you have any questions at all please leave a comment (below). We also have a Google Group dedicated to the projects and related items on the website – please sign up, it’s free and we can all learn something. High resolution photos are available from flickr.

Otherwise, have fun, stay safe, be good to each other – and make something!

[Note – the TLC5940 was purchased by myself personally and reviewed without notifying the manufacturer or retailer]