Voltage reducer?

[CBFryman2 5,000+ posts]

Resistor.

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[CBFryman2 5,000+ posts]

Depends on the resistance of the LED. If you can tell me that I can tell you how big of a resistor per LED, If you want to put more than one LED on a single resistor you will have to tell me how many.

 

[CBFryman2 5,000+ posts]

a 30ohm is the lowest resistor I would go with on 6 LED's wired in parrallel.

 

[CBFryman2 5,000+ posts]

FYI the resistance is 175-200ohm (even though it doesnt state it)

 

[qtipextra 5,000+ posts]

Or, you could just buy 12v LEDS that are ready to be hooked up to 12v. No hassle.

http://www.superbrightleds.com/mini-wedge.html. Go there, then go to the first product.

 

[lilmaniac2 5,000+ posts]

step down transformer? alot of over kill for that tho

check into zener diodes

 

[JimJ 5,000+ posts]

You could get a couple volts of drop across some Zeners...and also provide reverse polarity protection if you goof //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[qtipextra 5,000+ posts]

If you have many available, you coud wire 3 or 4 in series with each other. at 3 together, thats 12v, at 4 its 16v.

 

[lilmaniac2 5,000+ posts]

id run 12 v to one and see if it takes it... most of the time they take them

 

[qtipextra 5,000+ posts]

If you have many available, you coud wire 3 or 4 in series with each other. at 3 together, thats 12v, at 4 its 16v.

That would work even if you dont do it in clusters, like I was picturing when I wrote that up. As long as you keep track, you can wire 3 or 4 in series. Just make sure you have enough wire to place them where you need to still.

 

[CBFryman2 5,000+ posts]

Wiring LED's in series would make them get dimmer down the line. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

DC current FTL.

 

[qtipextra 5,000+ posts]

Wiring LED's in series would make them get dimmer down the line. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
DC current FTL.

Good point. I hadnt thought of that.

 

[thch 10+ year member]

a diode has a current - voltage characteristic that is very sharp. if you apply 4V you will have maybe 50mA of current. at 5V the current would be much higher.

this is why 12V is dangerous to the LEDs. but also why resistors are VERY effective.

the voltage across the resistor is V = I*R. thus as the current through the diode increases, the voltage across the resistor increases. because of the sharp V-I curve on the diode, and the lack of need for percision current to the diode, the math is pretty much:

I_diode = (V_source - V_diode) / R

if you want 30mA on a 4V LED on a 12V source, its just:

30mA = (12-4) / R, thus R = 8/30m = 267ohm.

the series LEDs should be approximatly equally bright in series -- equal current must flow through each.

for 4V LEDs on 12V, i'd put 2 LEDs in series. 20mA may be ok for currents. this is 12V - 4V - 4V = 4V across the "current limiting resistor". for 20mA, 4/20 = 200ohm. a 0.25W resistor is fine.

find out the suggested forward current, and rated forward voltage @ this current for best resistor selection.