Hi and welcome to my blog! This is my first post so bear my inexperience!
After visiting a friend's home, I was kinda jealous of the remote-controlled lights in his ceiling, so I wanted to have a similar "fixture" in my house too. This is how I thought and created my own.
Remote controller
IR controllers require optical contact and I didn't want to point at the receiver for every change in settings, so this RF remote controller was the initial step for my project. I got mine off eBay, but they should be available in other sites too.
It features a tiny PCB that goes in series with a light source (an LED strip for example), and controls its brightness using PWM (5-100% with 5% steps). It also has 5 preprogrammed "modes" of varying brightness that I'm not using.
Here are some specs:
| Working Voltage | DC 5-24V |
| Output current | peak 12A |
| Remote control mode | RF wireless |
| Remote frequency | 433.92MHz |
Light source
Next I had to choose the source of light. These single LED modules (1-200W) have an amazing light output for their very low price but also have the disadvantage of high localized heat output which requires a large heatsink in order to have a long lifespan (i.e. not get fried). Also, despite their 120° viewing angle, they still act like point sources (creating shadows behind objects, etc). Therefore my next best choice were LED strip lights. They are not very efficient in terms of power/space, but spread heat over a large area so no heatsink is needed. Also, just because of this inefficiency, they illuminate more evenly and the shadows produced are softer.
There are various configurations of LED strips, most commonly comprised of 3528 (smaller, single diode per chip) or 5050 (larger, 3 diodes per chip) SMD LEDs. You can also choose between single or double row, and 60 or 120 LEDs per meter, the latter having more dense light output. I ordered a 5m single row, 120 LED/m, cool white strip like this one:
Specs were as following:
LED Chip Model: SMD 3528
View angle: 120°
LED Quantity: 600 LEDs /5 meters
Working Voltage: 12V DC
Working current: 0.35-0.4 A /meter
Output power: 20-24 W /5 meters
Light output: 360-480 Lm /meter
Color temperature: 6000-6500K
Support / Attachment
I used a small PVC cable duct (or channel) for attaching the strip to the wall, and the idea is to have 2 strips of 2.5m point towards the ceiling and diffuse the light across the room.
Power supply
For the power supply a 230 to 12V AC-DC switching power supply was used, as they are superior in almost every aspect as opposed to the simple transformer-rectifier-regulator power supply in many applications including this one.
Installation
The main parts (controller, led strip) were ordered from eBay, while the rest were bought from local stores. Installation was complete in an afternoon and was really simple. Here are some photos of the finished project.
Shorted controller
I had some setback when i accidentally ramped up the voltage of the test power supply, and the controller (the wired part) was shorted "ON", not accepting any command from the RF device. The part was only covered by a heat shrinking tube, so I cut it open and noticed the output MOSFET was the one causing this (the rest of the circuit was protected using a zener diode regulator). All pins were shorted together (pretty delicate devices after all). I couldn't find a replacement as it was in SOIC8 package, and I would either have to pay a fortune to buy it locally, or wait for an overseas order to arrive. None of these was an option, so I went for a DIY style repair fitting a salvaged MOSFET from another device to the pcb. Here are some pics of the final repair:
Final thoughts - further improvement
I'm kind of obsessed with this remote controller now, and really like the finished look. Although, as satisfying as this project is, it does have some problems.
First, the light color is poor. Almost ugly. OK I know cool white is 'cooler' than natural (i.e. sun) light, but this strip almost outputs a blue / slightly violet light. It's not so distinguishable in the photos but it's visible in person. I might add another strip of warm white color to 'mix' them and make the light warmer. A spectral output measurement would help me optimize the design, unfortunately I don't have that capability for now.
Secondly, the controller has a low PWM frequency. All the effort put in the power supply being 50Hz-ripple free is lost with the controller having a 150Hz switching frequency. It's not so obvious but you do notice it with fast eye movement or when shooting video. It would really be appreciated if the designers used a higher frequency (kilohertz range) so all these problems would disappear.
Last, although you could say it's not a problem, is the lower power consumption of the strip. And if power consumption is lower, I assume light output is decreased? Anyway, i was expecting a current of 1.75-2A, but I measured 1.5A at 12V. That's a 75% to 85% decrease from the rated specs.
That's all for now, see ya!
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