LED lm/watt

Hi guys,

I'm trying to find an LED for my project, so far my best option is the one attached, the specs show that it gives me a max of 1000lm @10.9W. I need a maximum of 400lm and I am trying to calculate my requirements, Is there a linear co-relation between lm and watts? If i only produce around 5W would it give me the amount of lumen that I need?

Look at the data sheet. Optical output in lumens is proportional to the current in the LED. There should be a graph of lumens versus forward current if the data sheet is any good. Then use a resistor and voltage source to supply that current. You need to make sure that at the current you use, that the LED is operated a reasonable amount above the forward turn on voltage, which is current, temperature and manufacturing sensitive. For that, look at the worst case forward voltage versus current graph.
There is plenty of information on the web about how to choose the resistor value, including on line calculators. If you have a supply between say seven and twelve volts you will be OK. Note that you have to calculate the power in the LED and resistor at the working current and voltage to make sure that you are operating them within their power ratings. Power LEDs need attention paid to heat sinking,
cheers,
Richard

Lumens or brightness of an LED can be correlated with the amount of current flowing through it. But for different LEDs the values or the graphs will be different. All you need to do is to find a datasheet and try to find the optimal value of current required for most brightness. Please note that the graph of lumens vs current input is not always linear and for best output and most efficiency, you might need to check the datasheet.

Regards,
Levent Iblis

Hi,

Please checkout this video. It might help you.

http://addohms.com/ep8/


AMit