DIY Moonlight

[Nickel]

Just curious, if my memory serves me right, when LED lights up, the voltage across it drops to 0.7V (or thereabout ?). So Oceandeep, what jc85 meant when he mentioned how big a resistor needed to take on the balance voltage of 8.4V, assuming you use a 12V adaptor and 5 LEDs ? You using the adaptor's internal resistor (variable ?) to absorbed the balanced voltage ? How is the heat amount generated by the adaptor ?

I am thinking of doing a moonlight consisting of 2 sets of 5 LEDs each. Both sets powered from 1 variable-voltage adaptor.

Any DYI guru can advise the best series/parallel connection from voltage/current standpoint ?

Thanks.

[CalciumReef]

i thought its an adjustable adapter

[jc85]

I'm definitely not a guru but tot I can share my setup.

I'm using a variable power supply of up to 12v supplying 1amp current. I have 7 Ultra Blue leds in parallel. Each LED will have a 430ohms resistor to limit the voltage or is it current? The voltage is then adjusted to 6volts instead of 12volts.

What I released is that if I change the voltage to 9volts, the LEDs is brighter but I did not do it because worry that the LEDs might not last long (abit like overdriving). Using ohms law, V = I * R. It does make sense that the voltage increase will result to brighter LEDs.

Anyone need an online calculator?

Cheers

JC

[Oceandeep]

Well here my calculation :

Normal LED's forward voltage drop is 0.7 Volt

Super bright LED's forward voltage drop is 2V, current is 0.03A

Ultra Bright LED's forward voltage drop is 3V, current is 0.03A

White LED's is 4 volt.

My adaptor is 12V 0.2A. Which means I can connect 4 LED's in series

without over drive the LED's

Adjustable adaptor is more easy to break down as due to heat...

So I only using a not adjustable adapter...

A constant voltage adapter means constant voltage but variable current depend on load.. So a resistor in series in this case

will be a voltage divider.... not a current limiter... then

all heat will be on the resistor... 0.03A x 0.03A x 430 = 0.387W

*this datasheet can show u that the forward voltage drop is 3.65 volt.*

http://www.sun-led.com/products/spec/XLBB12W.pdf