[[Category: Primer]]

{|
|- valign=middle
| align=center width=300px| __TOC__
| [[Image:RBG.jpg|500px]]
|}

<br clear="all" />
==Introduction==

Like normal diodes, Light Emitting Diodes (LEDs) are semiconductor devices designed to conduct current in one direction only. What makes LEDs unique is their internal material makeup: when atoms in an LED release energy due to the flow of forward current, it is released in the form of photons (light). Different construction materials and various phosphor coatings are used to produce numerous colors of light.

LEDs that Phidgets sells are all operable via the [[Digital Output Primer|digital outputs]] on any of our interface kits. However Phidgets also sells a specific [{{SERVER}}/products.php?product_id=1031 PhidgetLED-64 Advanced LED controller] since it is often desirable to control more LEDs than even the [{{SERVER}}/products.php?product_id=1012 1012 Phidget Interface Kit 0/16/16] can operate. It offers some unique features such as brightness control.

==How it works==
[[image:led.png|thumb|350px|Parts of an LED. The flat spot on the epoxy casing, is an anchor to prevent twisting from damaging the leads.]]

LEDs emit light from current flowing through them. As the current flows, the electronics experience a sudden drop in energy level (voltage). When that happens they release energy in the form of light. The amount of light produced is proportional to the current. Depending on the material used to make the LED, different colors can be created. Like a conventional diode, the current can only flow in one direction - from the anode to the cathode.

==Controlling LEDs==

===Forward Voltage===

The materials used within LEDs that cause them to emit different colors of light affect a property called its forward voltage. The forward voltage is the voltage at which current in the forward direction will flow through the device and allow the LED to convert electrical energy into light. If the voltage applied to the LED is below the forward voltage of the LED, very little current (or none) may flow, and therefore very little light will be emitted. Most standard LEDs with colors such as red, amber, orange, yellow, and green have forward voltages below 2.75 Volts, and can be used with a [[Digital Output Primer|digital output]] by simply soldering them to a connector-wire and inserting the wire into the output port. The forward voltage in the [{{SERVER}}/products.php?product_id=1031 1031 - PhidgetLED|PhidgetLED]] will default to 2.75V, and the maximum current defaults to 20mA.

===Supply Voltage===
{|
|- valign="top"
|To be an effective LED controller your digital outputs must be capable of <br />adjusting the forward voltage supplied to the LEDs to 1.7, 2.75, 3.9 and 5 volts<br /> settings allowing you to properly drive blue, white, violet, ultra violet and purple LEDs.<br /> The supply voltage will affect all LEDs. If you set the supplied voltage too high,<br /> power will be wasted and the controller may shut down from thermal overload. If you<br /> set the supply voltage too low, your LEDs will not be driven at the requested<br /> current, and will be dim or non-functional.
|
{| {{table}} border = 1
!colspan="2" style="background:#f0f0f0;"|Typical Forward Voltages
|-
| align="center" style="background:#f0f0f0;"|'''Color'''
| align="center" style="background:#f0f0f0;"|'''Forward Voltage'''
|-
| Infrared||< 1.9
|-
| Red||1.7 to 2.2
|-
| Orange||2.0 to 2.2
|-
| Yellow||2.1 to 2.4
|-
| Green||2 to 2.3
|-
| Blue||3.2 to 4.0
|-
| Ultraviolet||2.1 to 3.8
|-
| White||3.3 to 3.6
|}
|}

===Maximum Current and Brightness Control===

{|
|-valign="top"
|
Most LEDs fall within 20, 40, 60 or 80mA, and applies to all LEDs. The <br />Phidgets DiscreteLED API call can be used to provide more current <br />or control brightness and will adjust the current linearly between 0 <br />and the set maximum. This however does not imply a precise method <br />for controlling the visibility of emitted light, as this is affected by the <br />construction and quality of the LED as well as the eyes of the viewer. <br />Be cautious when changing the current property. Many small LEDs are <br />designed for a maximum 20mA, and can be destroyed if driven at higher <br />currents.
|
[[image:Ledcurrent.png|400px]]
|}

===Choosing Current and Voltage Settings===

Make sure to choose the minimum supply voltage setting to drive the LED that requires the most voltage during operation. Any extra voltage not required by the LED will be converted to heat by the 1031. For example, a Blue LED being driven at 20mA, 3.9V Supply, that requires 3.7 volts will cause (3.9V-3.7V + 0.4V) * 0.02A = 12 milliwatts of heat to be produced on the 1031. If this example instead uses a high power, 1.5V infrared LED at 80mA, this will create (3.9V-1.5V+0.4V)*0.08 Amps = 224 milliwatts of heat. See the Heat Dissipation and Thermal Protection section later on in this manual for more information about this issue.

==Multiplexed LEDs==
Multiplexing is a system wherein the entire display is not active at the same time. Instead, sub-units of the display are driven one at a time and the electronics combine with human persistence of vision (the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina) to make the viewer believe the entire display is continuously active. Many controllers use this architecture to reduce power consumption. 7 segment display clocks are an example of this.

In an effort to reduce electrical noise in the system the PhidgetLED does not use multiplexing. All 64 anodes are connected to the same power supply and the cathode of each LED connection is attached to an individual constant current sink. Also, the LEDs are not controlled by PWM - they are driven at a constant current.

==Other uses for LED controllers==

LED controllers are typically just a set of special digital outputs. This means they aren't limited to just controlling LEDs. They can be used to control relays, solenoids and even very small motors. The PhidgetLED can also be used to drive opto-isolators and MOSFET SSRs. A diode integrated into the 1031 on each cathode will clamp inductive surges to the anode supply voltage.

==Power Requirements and Power Supply Selection==

The power supply that is included with the 1031 is rated at 12V and 2A (max). If your application requires more power, a larger power supply may be necessary. The on-board voltage regulator is able to supply up to 6A for each LED supply voltage setting, as long as the power supply is able to provide enough voltage and current to the regulator. Assume an efficiency of 80% for the on-board voltage regulator when determining if a different power supply is required.

==Heat Dissipation and Thermal Protection==

Projects that require a high supply voltage, or have a lot of heat being produced from over voltage settings, will have over-temperature problems. This can be mitigated somewhat by understanding how channels are grouped and how the heat is distributed around the controller. On the 1031 channels are split into four groups: (0-7,24-31), (8-23), (32-39, 56-63) and (40-55); each controlled by their own individual IC. Evenly distributing the LEDs that may produce a lot of heat across these groups will balance the load on the ICs and reduce the risk of thermal overload. When thermal overload occurs, the integrated circuit (IC) controlling the involved LEDs will disable the output of all the channels it controls. For example, if an over-temperature occurs due to channel 12, all of the channels 8 through 23 will be disabled by the IC until the temperature back within the operating range. Thermal protection is activated when the die of the IC reaches approximately 160 degrees Celsius. Once the over-temperature fault has been corrected (ie, the IC has cooled down), the output channels will be re-enabled with the same settings as before the thermal shutdown. An error message will be produced during an over-temperature.

==Products that fall under this category==

*[{{SERVER}}/products.php?product_id=1031 1031 - PhidgetLED-64 Advanced]

*[{{SERVER}}/products.php?product_id=3601 3601 - 10mm Red LED (Bag of 20)]
*[{{SERVER}}/products.php?product_id=3602 3602 - 10mm Green LED (Bag of 20)]
*[{{SERVER}}/products.php?product_id=3603 3603 - 10mm Blue LED (Bag of 20)]
*[{{SERVER}}/products.php?product_id=3604 3604 - 10mm Yellow LED (Bag of 20)]
*[{{SERVER}}/products.php?product_id=3605 3605 - 10mm White LED (Bag of 20)]

*[{{SERVER}}/products.php?product_id=3606 3606 - 5mm Four Chip Super Flux Red (Bag of 5)]
*[{{SERVER}}/products.php?product_id=3607 3607 - 5mm Four Chip Super Flux Green (Bag of 5)]
*[{{SERVER}}/products.php?product_id=3608 3608 - 5mm Four Chip Super Flux Blue (Bag of 5)]
*[{{SERVER}}/products.php?product_id=3609 3609 - 5mm Four Chip Super Flux Yellow (Bag of 5)]
*[{{SERVER}}/products.php?product_id=3610 3610 - 5mm Four Chip Super Flux White (Bag of 5)]

*[{{SERVER}}/products.php?product_id=3611 3611 - 5mm Diffused Red (Bag of 30)]
*[{{SERVER}}/products.php?product_id=3612 3612 - 5mm Diffused Yellow/Green (Bag of 30)]
*[{{SERVER}}/products.php?product_id=3613 - 5mm Diffused Blue (Bag of 30)]

*[{{SERVER}}/products.php?product_id=3614 3614 - Flexible LED Strip Green (5m)]
*[{{SERVER}}/products.php?product_id=3615 3615 - Flexible LED Strip Blue (5m)]
*[{{SERVER}}/products.php?product_id=3616 3616 - Flexible LED Strip White (5m)]

*[{{SERVER}}/products.php?product_id=3618 3618 - RGB LED Modules - String of 10]

LED Primer

2012-06-29T18:52:08Z

Cora:

[[Category: Primer]]

{|
|- valign=middle
| align=center width=300px| __TOC__
| [[Image:RBG.jpg|500px]]
|}

<br clear="all" />
==Introduction==

Like normal diodes, Light Emitting Diodes (LEDs) are semiconductor devices designed to conduct current in one direction only. What makes LEDs unique is their internal material makeup: when atoms in an LED release energy due to the flow of forward current, it is released in the form of photons (light). Different construction materials and various phosphor coatings are used to produce numerous colors of light.

LEDs that Phidgets sells are all operable via the [[Digital Output Primer|digital outputs]] on any of our interface kits. However Phidgets also sells a specific [{{SERVER}}/products.php?product_id=1031 PhidgetLED-64 Advanced LED controller] since it is often desirable to control more LEDs than even the [{{SERVER}}/products.php?product_id=1012 1012 Phidget Interface Kit 0/16/16] can operate. It offers some unique features such as brightness control.

==How it works==
[[image:led.png|thumb|350px|Parts of an LED. The flat spot on the epoxy casing, is an anchor to prevent twisting from damaging the leads.]]

LEDs emit light from current flowing through them. As the current flows, the electronics experience a sudden drop in energy level (voltage). When that happens they release energy in the form of light. The amount of light produced is proportional to the current. Depending on the material used to make the LED, different colors can be created. Like a conventional diode, the current can only flow in one direction - from the anode to the cathode.

==Controlling LEDs==

===Forward Voltage===

The materials used within LEDs that cause them to emit different colors of light affect a property called its forward voltage. The forward voltage is the voltage at which current in the forward direction will flow through the device and allow the LED to convert electrical energy into light. If the voltage applied to the LED is below the forward voltage of the LED, very little current (or none) may flow, and therefore very little light will be emitted. Most standard LEDs with colors such as red, amber, orange, yellow, and green have forward voltages below 2.75 Volts, and can be used with a [[Digital Output Primer|digital output]] by simply soldering them to a connector-wire and inserting the wire into the output port. The forward voltage in the [[1031 - PhidgetLED|PhidgetLED]] will default to 2.75V, and the maximum current defaults to 20mA.

===Supply Voltage===
{|
|- valign="top"
|To be an effective LED controller your digital outputs must be capable of <br />adjusting the forward voltage supplied to the LEDs to 1.7, 2.75, 3.9 and 5 volts<br /> settings allowing you to properly drive blue, white, violet, ultra violet and purple LEDs.<br /> The supply voltage will affect all LEDs. If you set the supplied voltage too high,<br /> power will be wasted and the controller may shut down from thermal overload. If you<br /> set the supply voltage too low, your LEDs will not be driven at the requested<br /> current, and will be dim or non-functional.
|
{| {{table}} border = 1
!colspan="2" style="background:#f0f0f0;"|Typical Forward Voltages
|-
| align="center" style="background:#f0f0f0;"|'''Color'''
| align="center" style="background:#f0f0f0;"|'''Forward Voltage'''
|-
| Infrared||< 1.9
|-
| Red||1.7 to 2.2
|-
| Orange||2.0 to 2.2
|-
| Yellow||2.1 to 2.4
|-
| Green||2 to 2.3
|-
| Blue||3.2 to 4.0
|-
| Ultraviolet||2.1 to 3.8
|-
| White||3.3 to 3.6
|}
|}

===Maximum Current and Brightness Control===

{|
|-valign="top"
|
Most LEDs fall within 20, 40, 60 or 80mA, and applies to all LEDs. The <br />Phidgets DiscreteLED API call can be used to provide more current <br />or control brightness and will adjust the current linearly between 0 <br />and the set maximum. This however does not imply a precise method <br />for controlling the visibility of emitted light, as this is affected by the <br />construction and quality of the LED as well as the eyes of the viewer. <br />Be cautious when changing the current property. Many small LEDs are <br />designed for a maximum 20mA, and can be destroyed if driven at higher <br />currents.
|
[[image:Ledcurrent.png|400px]]
|}

===Choosing Current and Voltage Settings===

Make sure to choose the minimum supply voltage setting to drive the LED that requires the most voltage during operation. Any extra voltage not required by the LED will be converted to heat by the 1031. For example, a Blue LED being driven at 20mA, 3.9V Supply, that requires 3.7 volts will cause (3.9V-3.7V + 0.4V) * 0.02A = 12 milliwatts of heat to be produced on the 1031. If this example instead uses a high power, 1.5V infrared LED at 80mA, this will create (3.9V-1.5V+0.4V)*0.08 Amps = 224 milliwatts of heat. See the Heat Dissipation and Thermal Protection section later on in this manual for more information about this issue.

==Multiplexed LEDs==
Multiplexing is a system wherein the entire display is not active at the same time. Instead, sub-units of the display are driven one at a time and the electronics combine with human persistence of vision (the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina) to make the viewer believe the entire display is continuously active. Many controllers use this architecture to reduce power consumption. 7 segment display clocks are an example of this.

In an effort to reduce electrical noise in the system the PhidgetLED does not use multiplexing. All 64 anodes are connected to the same power supply and the cathode of each LED connection is attached to an individual constant current sink. Also, the LEDs are not controlled by PWM - they are driven at a constant current.

==Other uses for LED controllers==

LED controllers are typically just a set of special digital outputs. This means they aren't limited to just controlling LEDs. They can be used to control relays, solenoids and even very small motors. The PhidgetLED can also be used to drive opto-isolators and MOSFET SSRs. A diode integrated into the 1031 on each cathode will clamp inductive surges to the anode supply voltage.

==Power Requirements and Power Supply Selection==

The power supply that is included with the 1031 is rated at 12V and 2A (max). If your application requires more power, a larger power supply may be necessary. The on-board voltage regulator is able to supply up to 6A for each LED supply voltage setting, as long as the power supply is able to provide enough voltage and current to the regulator. Assume an efficiency of 80% for the on-board voltage regulator when determining if a different power supply is required.

==Heat Dissipation and Thermal Protection==

Projects that require a high supply voltage, or have a lot of heat being produced from over voltage settings, will have over-temperature problems. This can be mitigated somewhat by understanding how channels are grouped and how the heat is distributed around the controller. On the 1031 channels are split into four groups: (0-7,24-31), (8-23), (32-39, 56-63) and (40-55); each controlled by their own individual IC. Evenly distributing the LEDs that may produce a lot of heat across these groups will balance the load on the ICs and reduce the risk of thermal overload. When thermal overload occurs, the integrated circuit (IC) controlling the involved LEDs will disable the output of all the channels it controls. For example, if an over-temperature occurs due to channel 12, all of the channels 8 through 23 will be disabled by the IC until the temperature back within the operating range. Thermal protection is activated when the die of the IC reaches approximately 160 degrees Celsius. Once the over-temperature fault has been corrected (ie, the IC has cooled down), the output channels will be re-enabled with the same settings as before the thermal shutdown. An error message will be produced during an over-temperature.

==Products that fall under this category==

*[{{SERVER}}/products.php?product_id=1031 1031 - PhidgetLED-64 Advanced]

*[{{SERVER}}/products.php?product_id=3601 3601 - 10mm Red LED (Bag of 20)]
*[{{SERVER}}/products.php?product_id=3602 3602 - 10mm Green LED (Bag of 20)]
*[{{SERVER}}/products.php?product_id=3603 3603 - 10mm Blue LED (Bag of 20)]
*[{{SERVER}}/products.php?product_id=3604 3604 - 10mm Yellow LED (Bag of 20)]
*[{{SERVER}}/products.php?product_id=3605 3605 - 10mm White LED (Bag of 20)]

*[{{SERVER}}/products.php?product_id=3606 3606 - 5mm Four Chip Super Flux Red (Bag of 5)]
*[{{SERVER}}/products.php?product_id=3607 3607 - 5mm Four Chip Super Flux Green (Bag of 5)]
*[{{SERVER}}/products.php?product_id=3608 3608 - 5mm Four Chip Super Flux Blue (Bag of 5)]
*[{{SERVER}}/products.php?product_id=3609 3609 - 5mm Four Chip Super Flux Yellow (Bag of 5)]
*[{{SERVER}}/products.php?product_id=3610 3610 - 5mm Four Chip Super Flux White (Bag of 5)]

*[{{SERVER}}/products.php?product_id=3611 3611 - 5mm Diffused Red (Bag of 30)]
*[{{SERVER}}/products.php?product_id=3612 3612 - 5mm Diffused Yellow/Green (Bag of 30)]
*[{{SERVER}}/products.php?product_id=3613 - 5mm Diffused Blue (Bag of 30)]

*[{{SERVER}}/products.php?product_id=3614 3614 - Flexible LED Strip Green (5m)]
*[{{SERVER}}/products.php?product_id=3615 3615 - Flexible LED Strip Blue (5m)]
*[{{SERVER}}/products.php?product_id=3616 3616 - Flexible LED Strip White (5m)]

*[{{SERVER}}/products.php?product_id=3618 3618 - RGB LED Modules - String of 10]

Use Phidgets Wirelessly with the SBC

2012-06-29T18:05:42Z

Cora: /* Phidgets */

[[Category:phidgetsSBC]]
[[Category:Application Guides]]
The project described here is a basic network control program for an LED plugged in to an SBC.

{|
|Practical concepts covered are (click on links to see other projects on that topic):
* Using the Phidget SBC
** Using [[:Category:PhidgetsSBC|Phidgets over the Webservice]]
* Using Phidgets with C/C++
|width="45px"| 
|[[Image:app_guide_sbcweb_sbc_image.jpg|200px|link=|alt=]]
|}

As with any of our [[:Category:Application Guides|described projects]], Phidgets takes care of the electrical component design. This project demonstrates what the SBC already does naturally from the time it ships. If you want something more powerful and flexible to control Phidgets over a network, you may be interested in these other Application Guides:
* [[Web Page on the SBC]] - Controlling Phidgets over the web using CGI
* {{LinksNeeded|Web Server on the SBC|[[Web Server on the SBC]]}} (coming soon) - Controlling Phidgets over the web using a full self-contained webserver embedded in C code

{| style="border:1px solid darkgray;" cellpadding="5px;"
|'''Time:'''
| About an hour
|-
|'''Special Needed Tools:'''
|None
|-
|'''Materials and Phidgets:'''
|A Phidget SBC, Ethernet and power cords (or Wireless), an LED, and your computer
|}

You should have already worked through the [[1072 - Getting Started]] page to have set up the network on your SBC and obtained its IP or local link address.

__TOC__

==Introduction==

When the SBC is powered on and connected to a network, it automatically handles any network requests for the Phidgets attached to it. All sensor and other Phidget data is broadcast over the local network as it changes, and all incoming Phidget control requests to the SBC over the local network are directed to the appropriate Phidgets.

This Webservice system looks something like this:

[[Image:app_guide_sbcweb_webservice_flow.png|500px|link=|alt=]]

To create these requests to control the attached Phidgets, or to receive incoming sensor data, we write code on the controlling and receiving computer. This application guide simply blinks an LED plugged in to the SBC, and does so over the network.

==Phidgets==

For this, you will need:
* A [{{SERVER}}/products.php?product_id=1072 Phidget Single Board Computer], set up as per the [[1072 - Getting Started]] guide
** This is the SBC that this guide used; others will probably work fine as well
* An LED, such as one of the ones from Phidgets (many part numbers starting at 3600), attached to digital output port 0 (long wire) and ground (short wire)

==Code==

On your external computer, you can use this code to control the Interface Kit (which is attached to the SBC) over the network:

<div class="source">
<syntaxhighlight line start="1" lang=cpp>

#include <stdio.h>
#include <stdlib.h>
#include "phidget21.h"

int main(int argc, char* argv[]) {

int result;
int outputState;
int i;

CPhidgetInterfaceKitHandle interfaceKit = 0;
CPhidgetInterfaceKit_create(&interfaceKit);

CPhidget_openRemoteIP((CPhidgetHandle)interfaceKit, -1, "phidgetsbc.local", 5001, NULL);

result = CPhidget_waitForAttachment((CPhidgetHandle)interfaceKit, 10000);
if (result) {
printf("No Device!\n");
return 0;
}

outputState = 1;
CPhidgetInterfaceKit_setOutputState(interfaceKit, 0, outputState);

for (i = 0; i < 1000; i++) {

if (outputState) { outputState = 0; }
else { outputState = 1; }

CPhidgetInterfaceKit_setOutputState(interfaceKit, 0, outputState);
}

CPhidgetInterfaceKit_setOutputState(interfaceKit, 0, 0);

CPhidget_close((CPhidgetHandle)interfaceKit);
CPhidget_delete((CPhidgetHandle)interfaceKit);

return 0;
}

</syntaxhighlight>
</div>

Some highlights:
* Line 14 is the line that actually opens the Interface Kit over the network.
** Notice that there is no mention of the SBC, or any SBC object.
** The SBC will simply act as a transparent pipe between the Phidget and your computer.
** The local link address ({{Code|phidgetsbc.local}}) and the port (5001) are the defaults, make sure to change them to what you have set in the Getting Started guide.
* Lines 25-31 blink the LED quickly; however, the flashing will barely be visible and the LED will simply appear to be on

==Putting it All Together==

Compile your C file using the instructions for our examples on the Language - C/C++ page.
*This code was written for gcc, so you'll either have to use a gcc compiler (Cygwin, Mac OSX, or Linux) or modify the code to work with your favourite platform.
*The code has been tested on Linux, and Cygwin on Windows.
*Make sure to copy the last blank line return at the end of the file - many Windows compilers insist on this being present.

Then, run the program and watch the LED on the SBC!

[[Image:app_guide_sbcweb_sbcled.jpg|300px|link=|alt=]]

==Extra Credit==

# Phidgets attached to the USB ports on the SBC will be opened the same way as the Interface Kit in code, except with different software objects.
#* Plug a USB Phidget in (if you have one) to one of the SBC's USB ports, and add that Phidget's object and some functionality to the code above
# Sensors attached to the analog ports will be opened via a port on the Interface Kit.
#* Try using the function {{Code|CPhidgetInterfaceKit_getSensorValue}} on the different Interface Kit analog ports to read them.