How Bright will these LEDs Be?

[Buffalosports]

I am looking to order some LEDs off of Ebay. I found these. They come with resistor but they claim to have 18,000mcd. Will this be to bright? Do you think this is true? Will they burn out fast? I am using them to put under the seat and under the dash.

http://cgi.ebay.com/ebaymotors/50-5...024QQitemZ370067277944QQrdZ1QQsspagenameZWDVW

 

[Bill Kemp]

1. Will this be to bright?
Yes
2,Do you think this is true?
Maby
3.Will they burn out fast?
They say they will last for ever.
For $15 how can you go wrong?

http://cgi.ebay.com/ebaymotors/50-5...024QQitemZ370067277944QQrdZ1QQsspagenameZWDVW

 

[shortstack]

yes they are probably everything the guy said, i've bought leds from him before. here are 5 leds 5,000mcd 5mm one each board/side, this should give you a good idea

note with the resistors provided, they shouldn't burn out for a very long time

 

[manaen]

18,000 mcd is good for ambient lighting, 18K will not be too bright, and if you are very creative you could wire it into the dash circuit so it will dim with the dimmer switch. Also if they are too bright, you can always increase resistor which will decrease the light output.

That is the great thing about LED's they are totaly adjustable up to thier max mcd.

As long as you do not over drive them they will last for a long time, so be sure to use the resistors they give you to limit the current going into each LED and they will last a long time.

 

[Buffalosports]

Ok I ordered them last night. I plan on running atleast 4 series. Should I put a resistor before every LED or will one resistor before each series be enough?

 

[MustangP51]

18,000 MCD will put out plenty of light. However I am concerned about one thing from his description.

"1.9 V Max: 2.3 V"

The operational voltage of the LED is 1.9 volts, and I think he is using resistors that will only bring the voltage down to 2.3 volts to squeeze out more MCDs. Is it a big deal, not really, but the LEDs will only have a lifespan of a few hundred hours rather then a few thousand.

 

[MustangP51]

Ok I ordered them last night. I plan on running atleast 4 series. Should I put a resistor before every LED or will one resistor before each series be enough?

Wire a resistor to each + LED lead, In my opinion the voltage fluctuates to much in a vehicle to wire LEDs in series.

 

[shortstack]

^^^ bingo

 

[manaen]

If you want the best lifespan wire a 12v regulator in the line before the resistors and the LED's that way you will only be feeding them a constant 12v instead of the 12 to 14 volts

or you can also wire them into the dimmer switch which will also hold the voltage back.

 

[manaen]

Just looked at the auction again, the seller does specify 12v dc input voltage. So you will need to supply no more then 12v to the units to keep them in the safe operational voltage. When your alternator is running they will receive about 14v therefore will be outside of the nominal voltage and probably shorten their life considerably.

I would really recommend using the 12v regulator something as simple as THIS

 

[Buffalosports]

Just looked at the auction again, the seller does specify 12v dc input voltage. So you will need to supply no more then 12v to the units to keep them in the safe operational voltage. When your alternator is running they will receive about 14v therefore will be outside of the nominal voltage and probably shorten their life considerably.

I would really recommend using the 12v regulator something as simple as THIS

Looks good. Couple questions:

a. Can this be bought at Advance Auto Part or AutoZone (do not like Radioshack... way over priced and I will need many of these, I think)

b. Isn't the job of the resistor to only allow the proper voltage through

c. If I wire parallel, do I need to put one in before every resistor or one just before the series starts?

 

[shortstack]

i have a bunch of led that use 12volt resistors, never had any of them burn out, wire a resistor to each led on the + or - side then connect all the + or - together. i wouldn't waist my money on getting new resistors, but yes you can get some at radio shack or online

 

[manaen]

a resistor will limit the flow of current, a regulator will limit the voltage. So if you feed too much voltage into the resistor, it's output voltage can be too high for the LED.

The one unknown is what resistors are you getting with the LED's. If we knew that we could tell you if you need to regulate the power going into them.


Oh and you would only need one or two of those regulators depending how you need to wire up the LED's. One of those regulators could run all of the led/resistor combo's together.

 

[shortstack]

http://led.linear1.org/led.wiz

 

[JCUZ]

They should be OK, but you would be better off just getting the LEDs, and buying the resistors separately. I got 100 15000mcd 5mm LEDs for around $15, and then bought resistors - 100 for $6. You need to solder the resistors to the LEDs, but it's not too much work. The resistors I got were 560 Ohm 1% Tolerances, and I've even used up to 620 Ohm - the difference in light output between the two ratings is negligible, but the safety margin increases with the 620. I worked this out using 15 Volts, and not 12.

The Calculation for resistor is as follows
R = (V-LEDVolts)x 1000/I

R = The Resistor Value in Ohms
V is the Supply Voltage (The Vehicles Operating Voltage)
I is the Resistor Supply Current in Milliamps.

So for 2.0V LED's
R = (15-2.0)*1000/20
R = (13.0)*1000/20
R = 13.0 * 50
R = 650 Ohms
Because a 650 Resistor Value is not available, the value of 620 was
selected because it was the closest value available
Basically, the lower the resistor value, the brighter the LED will
become, but the margin for poor voltage regulation becomes less.