Custom LED Flash Design

This page is the current central source of research and design documentation for the Modular LED Flash Unit project.

To Summarize:

Existing Consumer Flash Units

• Awkward to mechanically integrate

• Awkward to electrically integrate

• No meaningful ingress protection

• low durability / reliability

• Still too costly for the multi camera systems

Existing Industrial Flash Units

• Expensive ($1500+) per unit

• Not bright enough for BB / IAS applications

• Very few options / suppliers available

  • Limits install flexibility

 

Open

Consumer Flash Unit

Open

Industrial Flash unit

For these reasons we are exploring the design of an in-house flash unit to fulfill our needs.

Direction

The flash system will likely be LED for the following reasons:

• LEDs are more physically durable than Xenon flash tubes.

• A well implemented LED flash should last much longer than Xenon tubes.

• LED flash systems require much lower voltages (50-100V vs. 300-500V) which helps size, cost, complexity, and safety.

• Building a flash from multiple LED modules provides more flexibility than Xenon tubes which come in a limited number of sizes and shapes.

• An LED flash can be controlled in a much more precise way than Xenon tubes, where if implemented both brightness and duration can be precisely controlled.

Initial research has found that there is a significant lack of information / standard designs with LED camera flashes. So, the design phase will be proceeded by a more significant research / prototyping stage than our typical hardware projects.

For the development of this flash system, we will need to characterize the output of LEDs in many different overdrive conditions. Typically, in electrical / electronics design we can utilize the components data sheet for this type of information; However, LED manufactures typically do not publish data beyond 200% output levels. But research and commercial products show that it is possible to significantly overdrive an LED chip without damaged for short periods dramatically increasing the light output.

Some References Related to LED Overdriving:

Testing Setup

Preliminary Specifications:

• Enclosure rated to handle outdoor environments for extended periods of time unprotected (weatherproof & IP 65 or better). What Does IP65 Mean? | OnLogic

• Accepts common input voltages present in our systems (12, 24, or 48 VDC).

• Design or resulting units are configurable for various applications (such as PM3D vs. AgIR).

• An individual unit suitable for PM3D application will cost <$200 in quantity to build.

• Incorporated proper heatsinking for good longevity of LEDs and continuous operation.

• Form factor accommodates integration into out hardware systems.

Prototype Design

Here various design decisions and calculations will be documented through the protype design phase.

Selection of LED

The first step is to choose what LED(s) will be used. There is a large variety of form factors and suppliers to look at, both individual properties of the products themselves need to be considered, as well as their form factor. Common form factors include chip LEDs that get individually soldered and large COB (Chip On Board) modules. What makes one a better choice over the others is related to several factors:

• Light output vs. Area.

• Ease of integration into a thermal management solution.

• Optics availability and cost.

• Labor needed to assemble units (more smaller LEDs may take longer to build unless they can be done on an SMT machine).

• Cost in dollars per lumen output (brand / model dependent).

• Efficiency (brand / model dependent).

Determining Necessary Luminous Flux of LEDs

There are many factors to consider here.