Recently, we acquired some LED ring lights for our projects. These little gadgets arrived this week at our shop. We got a chance to check them out before passing them to product design. Let’s do a quick review, get them working and do a write up. Let’s go!
For some reason the product is called White Light Car Angel Eye, most likely they are to mimic the halo ring of the late models BMW headlight. We purchased the rings from Deal Extreme website. The site offers this product in a variety of sizes and we got 70mm, 80mm and 90mm version. Each light comes packaged individually in Ziploc bag.
Photo 1. – The White Light Car Angel Eye
The ring itself is a circular PCB that measures 1.55mm in thickness, outside diameter of the 70mm ring measures 69.88mm and ID is 54.15mm. With white solder mask on both sides, LEDs and resistors placement are clearly marked and silk screened in black brackets. A total of 21 LEDs (Surface-mount Technology, dimension measures 3.5mm x 2.7mm, emits white cool color with a diffused and yellow tinted lens) are mounted on the 70mm ring. Similar product can be found in digikey. The LEDs are equally spaced on one side of the ring and resistors (Surface-mount Technology, 180 ohm) are on the other side.
Photo 2. – Side view showing 1.5mm thickness PCB and Surface Mount Technology LEDs
For simplicity we will call the side with resistors “top” side as it has the positive power track. The red cable terminates to the positive track which is a circular main path runs along the inner diameter of the ring, feeding seven resistors. After the resistor, via connect the track to the “bottom” side to the LEDs. Three LEDs grouped in series (7 groups in total thus 21 LEDs) and exiting to ground track that runs along the outer diameter of the ring. Two vias connecting the ground track back to the top side where the black cable is.
Photo 3. – This is the bottom layer. Note the via on right LED and left LED exits to ground track (Outer diameter of ring)
Photo 4. – The outer ground track has two vias
Photo 5. – This is the top side. Note the power cables termination
Photo 6. – Solder joints and vias
Photo 7. – The top side. Note the + power track on the inner diameter of ring
Photo 8. – LED under microscope.
Photo 9. – Off position resistor but still works
Photo 10. – Bad solder joint
Overall this product is simple with good design but quality is sub par. We witness chipped solder mask layer, bad placement and poor solder joints. Some re-work is necessary before use.
|Thickness (incl. LED)||4mm||4mm||4mm|
|Number of LEDs||21||24||24|
Enjoy, Team BTF.