Using white LEDs for lighting

sinalization light

We are trying use a white LED array replacing fluorescent lamp. In first prototype, with 72 5mm round white LED´s, we not have same lighting then one 30W fluorescent lamp.

What the factors that adjusted may increase the lighting? What ideal LED for this application?

Thanks, Gorkin

as far as i know white LED is ideal for this... just try increasing the current drive....

What is the current consumption per LED?
Let us assume that each LED has a forward drop of 3.5 V at 20 mA driving current, thus consuming about 70mW. Therefore your array should be consuming 5 W.

However if you are driving it using full rectified AC, take this down to 63%.

I guess, 5W (or less) of LED being equal to 30W of CFL is great. However, check the angle of illumination for LEDs and CFL.

gorkin said:

We are trying use a white LED array replacing fluorescent lamp. In first prototype, with 72 5mm round white LED´s, we not have same lighting then one 30W fluorescent lamp.

What the factors that adjusted may increase the lighting? What ideal LED for this application?

Thanks, Gorkin

Click to expand...

Consult the datasheet of the LED and let the LEDs consume the maximum current indicated there.

White LED maximum current usually the same as other LEDs. Its about 30 to 40mA per LED. But white LED has an operating voltage higher than other color, that is 6.3V.

I've made this project for my room, I use honeycomb matrix format in total of 150 LED in 5 by 30.The hight of the LED forming a triangular shape so the effective intensity can reached.

Today, reading a local electronic magazine, I read that the amount of lighting LED are affected by the temperature and running time. The author suggest yet the use of compensation circuit for minimise these effects.
I just question how function and how complicated are the circuits used today in some applications like in automotive environment, street sinalization, emergency sinalization, etc...
If the fact these degradation has effected, one more elaborated circuit is necessary, but the cost of product rise too! I am very confuse 8O 8O 8O

Thats all! Gorkin

No don be confused with such non sens. Anyway, if you want to use LED for lighting, there will be no concern if the light dimmed a bit... our eyes cannot see. trust me its not significant...I know because I've build one.

Anyway, have you build it?

Thanks Rikie!
I never build similar application! Then my primary doubts! I post this quest just for question people with lot of experience in this field!

Now I have choose different vendors for analise and build a test circuit for evaluate the best LED. I think a association of 5mm round LED can be a good idea. Maybe a large cluster even with 3 LEDs associate in triangle geometry...

Gorkin...

Using LED for room lighting is expensive, but the life time of LED and the reliability is high.

I made another LED array for room lighting, but this time I use 400 LEDs. 100 super bright white, 100 super bright green, 120 blue, and 80 red. Using mcu to control its dimming and color mixing facility, i'm sure it will make my friends who came in to my room says WOW!

gorkin said:

We are trying use a white LED array replacing fluorescent lamp. In first prototype, with 72 5mm round white LED´s, we not have same lighting then one 30W fluorescent lamp.

What the factors that adjusted may increase the lighting? What ideal LED for this application?

Thanks, Gorkin

Click to expand...

Hi Gorkin,
I have designed several applications for high power LEDs, there are many different issues you have to think about when you designing a replacement for ordinary light sources such as:

- LEDs have limited angel (look in the data sheet, they range from 11 to 45 and in some rare cases, up to 90)

- LEDs can be extremely efficient if you use a PWM controller to lower your consumption

- LEDs behavior depends on many facts such as constant current, the stability of the voltage, the temperature etc.

You must look into the spec of the LEDs to find the correct setting for that particular device, many of the high power LEDs (probably the 5W you are trying to use) can not be connected in series, a mistake many people do and causes problem with the quality of the device.

Hope this helps,

Best regards,
/Farhad

Wow Farhad! Very nice project!
My application is for internal and external bus lighting. Replacing electronic fluorescent ballast.

Gorkin

I made a lighting device to replace a fluorescent lamp. I used LED’s made by http://www.hebeiltd.com.cn/?p=led.auto.piranha.
I recommend 980MW7C (http://www.hebeiltd.com.cn/led.datasheet/980MW7C.pdf). The lighting system has 100 LED’s. There are 20 linear groups connected in parallel mode. Each group has 5 LED’s connected in series with a limitation resistor (22 ohm). The power drop on resistor is small because the current in each group is 40 mA. It is important to use a power supply with a stable output voltage. I used this type of LED’s because their price is reasonable (0.179USD).

can anybody post 12-30v led emergency lamp circuit diagram (tested)