stonefox Posted December 13, 2015 Report Share Posted December 13, 2015 How do I measure how many watt LED diode is on. Have some different that I do not know the value of. Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 13, 2015 Report Share Posted December 13, 2015 You need the part number and detailed datasheet from the manufacturer of the LED to determine its continuous and pulsed absolute maximum allowed currents. The datasheet tells you the range of forward voltage or you can measure it. Then the power (Watts) is the current times the voltage.Or you can try one at higher and higher currents until it fails or smokes then you can guess that the other LEDs are the same or better. Most 5mm diameter LEDs have their voltage and brightness rated at 20mA. Their maximum continuous current might be 30mA or 40mA. Quote Link to comment Share on other sites More sharing options...
stonefox Posted December 13, 2015 Author Report Share Posted December 13, 2015 Is there a device that can be put on + wire of a transformer, and I manually adjust up or down to find the correct voltage?ExampleIf I have a 15 volt - 5 A adapter - sets a variable device on the + wire - and the more I turn up from 0 the more power to the LED Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 14, 2015 Report Share Posted December 14, 2015 An LED sets its own voltage. A red one is about 1.8V to about 2.0V. A blue or white one is about 3.2V to about 3.6V and they are all different unless they were all measured and grouped. The brightness of an LED is controlled by adjusting its current, not its voltage. To avoid burning out an LED it must have a series current-limiting resistor. The series resistor and LED can be fed a variable voltage that adjusts the current which controls the brightness. You said you have a transformer. A transformer has an AC output which might burn out an LED that needs a DC current. +15V at 5A will heat an LED with 15V x 5A= 75W which will instantly fry an LED designed for 2V x 20mA= 0.04W. Quote Link to comment Share on other sites More sharing options...
sepp1234 Posted December 15, 2015 Report Share Posted December 15, 2015 That's right! Watt is Current x voltage => [w] = [a] x [V] Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.