The background bits

The proposal for this roadtest plus was written around the TI TPS92512 which is an LED Driver Buck converter. The idea was to design a 4Channel Lighting solution along with a variety of LED panels. In addition to RGB Lighting Panels, it was proposed that custom ones can be made using special LEDs for agricultural lighting more commonly known as ‘Grow Lights’. Additionally, the control over the colour as well as intensity of the lights should be controllable over say Wi-Fi which can be accomplished by using a CC3200. The system is to be designed in an enclosure that can replace the conventional home or industrial lighting hence the title “Multipurpose Modular Light Bar Project”.

In the last post, I showed you how I made the schematic in Eagle. There were some minor corrections needed and I added some stuff as well. Lets see what I did.

Modifications to the Schematic

There were some issues with the schematic from the last post and I made some corrections. I cleaned up the schematic as well as added connector to make the PCB into a booster pack for the Texas Instruments LaunchPads. I also added some additional resistors for the current sense resistor because the 0.2Ohm resistor was unavailable as well as costly. I have a bulk of 1K and 18K and some other resistors which I will use. In this instance I intend to use 1Ohm resistors in parallel to fabricate a 0.2Ohms resistor. It does take up a bit of board space but its more convenient and cost effective. Additionally, it will be useful for future current sensing circuits in the future.

The layout of the EVM modules was used as the basis for my layout for the most part. I initially intended to make a 4 channel single board but I would like to experiment with smaller boards first. Cleaned up schematic looks like this.

The tit-bits

As part of the deal, I got the capacitors, LEDs, Coils and connectors from WE-Online.de The image below shows some connectors as well as the coil which I got from them.

The biggest problem with getting connectors from anywhere is making their footprints for layouts. In the case of WE, the footprints are already available from their website. I downloaded most of em and here is what it looks like.

Using these I was able to finish the layout and it looks like this.

The difference from the EVM modules is that I used 0805 parts instead of 0603 so that I am able to hand solder them. The booster pack format also helps with the final assembly when I make the mountable assembly.

For production, I have sent these to Seeedstudio's Fusion service and should get them back by next week. I have also done some experiments with controlling the LED brightness using the PWM from a launchpad which I will explain in the next post.

Cheers,

IP