My DIY LED Project needs help

Thread Starter

RicardoRamos

Joined Jun 13, 2020
2
Hi,

I'm a complete noob but I like to learn in trial by fire.
So I got the idea to turn an old IKEA lamp from traditional lights to LED's.

It's this one:
Captura de ecrã 2020-06-13, às 21.08.06.png

It's 36 lights.
So I decided to buy 36 RGB LED's and a bunch of resistors.
The problem that some of the kind souls around this forum can help me with is the diagram to make this a reality.
I seen some videos with a single rgb led connected to an Ardoino board to controle the lights.
There are also controllers for RGB led strips, can I use that instead?
I was also thinking of using the power source from the lamp itself. It has an output oh 11.5V and 70W max.

I used this array wizard for each color but I'm not sure if this is the right way to go forward with it since their RGB led's and not the traditional one color 1 led design. And also I have no idea about the best way to controle the lights.

Any help would be so very helpful.
Led Azul ou Verde .png
 
How many pins on your LEDs? RGB usually have four pins... one for either + or - depending on how they are built, and the other three for the three colors. If they are the four pin type you will not be able to wire them in series as your diagram shows. Many LED strip controllers actually send out data to the LEDs that the individual LEDs decode with a built in controller chip to vary the brightness of the individual colors. Each color in RGB LEDs will require a different resistor due to the each color has different power requirements. In my own projects I've found it hard to find the right resistors to make the LEDs produce the correct colors. A constant current power supply makes this much easier (although not perfect depending on the LEDs themselves). Microchip's LED driver comes to mind and I've used them in a couple of my own projects https://www.microchip.com/wwwproducts/en/CL2.
 

Thread Starter

RicardoRamos

Joined Jun 13, 2020
2
How many pins on your LEDs? RGB usually have four pins... one for either + or - depending on how they are built, and the other three for the three colors. If they are the four pin type you will not be able to wire them in series as your diagram shows. Many LED strip controllers actually send out data to the LEDs that the individual LEDs decode with a built in controller chip to vary the brightness of the individual colors. Each color in RGB LEDs will require a different resistor due to the each color has different power requirements. In my own projects I've found it hard to find the right resistors to make the LEDs produce the correct colors. A constant current power supply makes this much easier (although not perfect depending on the LEDs themselves). Microchip's LED driver comes to mind and I've used them in a couple of my own projects https://www.microchip.com/wwwproducts/en/CL2.
Hi,
Thank you for your insight. It's the 4 pin RGB LED's. 1 (-)3(+) for the each color.
SO what i'm getting from you're experience, I should add this CL2 for each LED?
I also read about using Arduino with a MOSFET.
Can anyone draw a viable schematic to make the 36 RGB led array?
I'm not finding an easy to use OSX app that I can play with and test virtualy.
 
SO what i'm getting from you're experience, I should add this CL2 for each LED?
Actually you will need one for each red, blue, and green pins for each LED. The hardest part is getting white to look right. If your resistors aren't carefully calculated it will either be too blue, or too green, or both. Then on top of that finding the exact value resistor to make everything right won't happen. You can get close enough with resistors to make it work though.

Is this a one LED per strand sort of light or do they kind of blend together? What are you planning on using to control it? How do you want to control it (all on one color, random colors, some on, some off, etc)? Can you program or willing to try?

Even though you have already purchased LEDs it may be easier in the end to get a small strip of WS2812 or APA102 LEDs, cut them individually, glue them in place, wire them up, and eliminate the resistors and everything else altogether. Those are the type of LEDs with built in controllers. You just give them power and send data from a microcontroller. The APA102 cost a little more, but they can be used with any sort of microcontroller. The WS2812 have very strict timing requirements that can't be accomplished by some slower devices. The reason I say this is with a multiplexed circuit like the schematic above you will be cycling through the rows every time so at most your LEDs will only be on 1/6 of the time.
 
Last edited:

Reloadron

Joined Jan 15, 2015
5,623
The only problem I see with the wizzard numbers is that you have RGB LEDs which don't normally have the same forward voltage for a given current. For example here are a few inages of a RGB LED strip which uses 50 50 LEDs.

RGB Strip.png

Each section of the strip has 3 LEDs and three current limiting resistors. Each of the three LEDs really has three LEDs which are the Red, Green and Blue so if I look at it as a schematic it looks like this.
5050 LED String.png

Just focus on the left side of the drawing. So what happens if I tie the +12 volts to 12 volts and all three bottom connections to ground is I get White. If I only tie one to ground I only get that respective color. We can mix colors to come up with more colors and if we want to get fancy add all sorts of effects like fade in and fade out shifting colors along the way. That is what most controllers do. Anyway I just found it unusual that all of the resistors are 120 Ohms.

Ron
 

mcardoso

Joined May 19, 2020
149
+1 to the addressable LEDs. The most common is the WS2812b (or at least it was when I played with them 5 years ago). You need a hefty voltage supply, but beyond that, a micro controller can control a long string of them with only 1 pin.

I found the SMT version to be rather sensitive to soldering temperatures so be careful. I bet using the datasheet gives 100% reliability, but hot air reflow fried a couple out of the hundreds I was soldering.

As shown in the link above, they come packaged in bulb styles if you want with flying lead wires out the back. very easy to work with.
 
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