Infrared Sensitive Lights

Abstract

The infrared sensitive light is a digital interactive LED module filled with ultra bright LEDs that respond in complex and gentle ways to stimulus provided by human interaction. The infrared sensitive light module will contain 8 LEDs, also has eight infrared proximity sensors— one for every LED —to detect nearby motion, even in total darkness.

The infrared sensitive light module is controlled by an on-board microcontroller and functions as a self- contained, stand-alone device. You do need to provide power (~5 VDC).

The infrared sensitive light module comes pre-programmed with eight different effects that respond to motion and gradually fade back to idle when there is no motion. You can switch between different effects and light sensitivity options with a button press.

Brief Project Description

Infrared Sensitive Lights (ISL) is a digital interactive LED module filled with ultra-bright LEDs that respond in complex and gentle ways to stimulus provided by human interaction.

Each ISL module is 4 X 8 inches in size, and features eight huge (10 mm) ultra-bright LEDs, spaced along a two-inch grid. Each ISL module also has eight infrared proximity sensors — one for every LED —to detect nearby motion, even in total darkness. The modules can be tiled edge-to-edge, seamlessly, in any size or shape of rectangular array. You can use them to cover a full wall, or just make a long strip or border as narrow as 4 inches wide.

ISL modules come pre-programmed with eight different effects that respond to motion and gradually fade back to idle when there is no motion, making them ideal for interactive LED walls, bar tops, and coffee tables. You can switch between the different effects with a button press: Gently fading trails after your motion, a "heat" mode that gets brighter as it detects more motion, simple positive and negative "shadow" effects that light the LEDs— or darken them — wherever you touch, ripple, sparkle, and a "melting" mode where activated pixels fade only very slowly.

Each ISL module is controlled by an on-board microcontroller and functions as a self- contained, stand-alone device. You do need to provide power (5 V DC), but no central computer or complex communication wiring is needed. Because it's self-contained, there is no trade-off between array size and performance.

Figure 1: Final ISL PCB Board

Specifications

General Specifications

Through hole
All components are RoHS compliant
Hardware license: Fully open source hardware
Firmware license: Fully open source software

Physical Dimensions

Module size: 4 x 8 inches (10.16 x 20.32 cm) wide
Board thickness: 1/16” (1.6mm)
Overall thickness: 0.75” clearance above and below circuit board
Mounting holes: 0.25” x 0.25” from each corner (4)

LEDs and Sensors

8 LEDs per board
LED type: Ultra-bright, 10mm OD, with wide viewing-angle diffused lens
LED color: blue
8 Sensors per board
Sensor type: Near-infrared proximity detector (active/passive)
Sensor range (active): 10cm, in dark room
Sensor range (passive): Unlimited, for detection of light and shadows from IR light sources

Microcontroller and Interfaces

ATmega 164, pre-programmed for stand-alone operation
MCU socket: 40-pin socket
Clock source: 8 MHz internal RC
User input: Single tactile button switch
Programming interface: Standard 6-pin AVR ISP (SPI)

Power Requirements

Input voltage: 5V DC, regulated
Current requirement: 200 mA capacity per panel
Idle current 50 mA
Current rating of power switch: 4A
Input power source: 2.5 x 5.5 mm jack

Board Design

Debugging

Before the layout was implemented on Diptrace, a prototype on a breadboard was built in order to insure the concepts behind the schematic of Evil Mad Science original implementation. When first developed the circuit was not working properly, however after further inspection, the issue was the distance between the phototransistor and the infrared LED sensor. This was due to the way that both sensors interact with each other. The infrared light LED is consistently emitting infrared light as seen from figure 2, and when triggered the IR light emits through the phototransistor.

Figure 2: IR LED and Phototransistor Interface

When debugging the breadboard version of the ISL this the was major problem, required further research into the distance allowed between the two sensors in order to properly place them on the PCB layout in order for both to work properly. The following image is the debugging stage:

Figure 3: ISL on Breadboard

As one can see from the image, I decided to only test one LED sequence. Being that all eight sequences are independent of each other, one sequence properly working should be sufficed testing behind the concept in order to deem it conclusively working. Notice the distance between the phototransistor and the IR LED. They are relatively close in order to insure that the sensitivity is up to par with the desired specifications. Furthermore, the debugging stage was successful teaching me more regarding the required layout format. The key takeaway was the distance between the sensor clusters. Another addition to the circuit is the polarized capacitor (C3) and ceramic capacitor (C4) to insure a more stable input voltage. However, these two components are not required in order for the circuitry to properly work, this was placed more for safety precautions.

Layout

After the concept was successfully tested and debugged, the following step was implementing the component/pattern libraries in order to create a working schematic (refer to Appendix) and further create the ISL layout. The following image is the final PCB layout created with the Diptrace software:

Figure 4: ISL Board Layout (Top)

Figure 5: ISL Board Layout (Bottom)

As one can see in figure 4 and 5, I decided to cluster each sequence together. This will ensure that when the correct IR sensor was triggered, the correct LED would be triggered as well. Being that the IR LED spread out the IR lights a certain radius, I had to make sure that each IR LED would only trigger the corresponding phototransistor. In the middle of the board is the ATmega microcontroller and in the center horizontal axis are, tactile switch, power jack, and power switch. Being that the board requires external ~5V from an outlet, I decided to place the power jack facing the bottom of the board to not have a cluster of components on the top. Also, I decided to elevate the board via the mounting holes so this elevating gave me enough space on the bottom of the board to be able to place the power jack without interfering with any of the board design. The power switch is also on the bottom of the board. The following image is of the final PCB unpopulated:

Figure 6: ISL Unpopulated PCB

The final manufactured PCB was all through-hole technology and was outsourced from a company established in Chicago. Some of the issues with the final PCB board consisted of the following. The via size for the resistor was a little smaller than anticipated so slightly more effort was placed into placing the leads through the via. The holes for the power switch and power jack were very snug, so slight amount of force was used to place them. Furthermore, the board did not have any design flaws as far as the layout and the routing was exactly to the original design.

Final Product

The final ISL PCB was a success. After the board was populated, very carefully, the ISL where up and running. The methodology behind the soldering process was to solder each sequence individually and debug each one if needed. This was done simply because of the amount of through-hole components needed to be soldering on to the board. Having this method allowed for a more focused debugging session if needed. Although taking this approach may seem longer, it is necessary when dealing with multiple components all at once. The following image if of the board finally populated with all the components:

Figure 7: ISL Populated PCB (Top)

Figure 7, shows all the components solder on to the PCB. The only components not shown are the Power Jack and the Power Switch, which are on the bottom side of the board. As we can see from Figure 8, the Power Switch is on the left side and the Power Jack on the right side:

Figure 8: ISL Populated PCB (Bottom)

After slowly soldering on all the components, the PCB was up and running. As we can see from Figure 7, there are eight total clusters of LED and sensors. The 6-pin AVR SPI is the programming header in case the user wants to change the settings on the ATmega microcontroller. The mode select button allows the user to change between settings and also to adjust the sensitivity of the lights.

Microcontroller

There are eight standard response functions. To advance to the next response function, press the button once. When you do so, the “next” LED in sequence will light up for about two seconds (to indicate which program), and then the board will go begin working with the new response function.

0. Gentle fade
1. Slow fade
2. Quick fade
3. Ripple
4. Sparkle
5.“Heating” with fade
6. Shadow mode
7.Trigger and very slow fade
(Program 0 is indicated by LED D0, and so on.)

There are four built in levels of sensitivity. To change the sensitivity level, hold the button for about ten seconds until it enters a different mode, where 1, 2, 3, or 4 pairs of LEDs are lit. While in this “sensitivity adjustment” mode, press the button to switch between the four sensitivity levels. Higher sensitivity increases the effective sensing range, but can also lead to more jittery behavior and “false positive” motion detection.

Figure 9: ISL Sensitivity Guide

Overall the sensitivity does effect the triggering of the LEDs however for a good range of sensitivity it is recommend to function in the “low sensitivity” mode, simply to avoid any false positives. For a complete demo of the ISL PCB, watch the video.

Conclusion/ Recommendations

In conclusion, the final board turned out to be a success. Future recommendations consist of the following; adding edge connectors, making via slightly bigger. The preprogrammed ATmega microcontroller has another perk that I did not use in this board. The first five pins from the microcontroller as we can see from the schematic (refer to Appendix) are not connected to anything in my schematic. However, those first five pins are designed to connect to edge headers. So the modules can connect to each other side-to-side through their edge connectors. For small arrays (or small sections of large arrays), these edge connectors can be used to share power between neighboring boards. When an array of boards are connected by the edge headers the LEDs react sequentially, in other words the board acts as if its one complete board.

The second recommendation would be making the resistor vias slightly larger. Reason being, a slight amount of force was used to push the resistors through the vias. This was not a major issue because they all worked just fine however; I had to be careful not to damage any vias while mounting on the components.

Furthermore, the seconds steps would consist of developing a chassis for the ISL and perhaps later on in the future develop a stand alone system that will not require the board to be plugged into any external outlets. For more information on the board design/specifications, visit Evil Mad Science (see References).