What Did I Do Wrong

salvatore

salvatore

Member
I made an attempt to wire up an LED moonlight this evening, and it ended with all four LEDs being blown. Based on the following information, what did I do wrong?
Parts (everything purchased at RadioShack:
6v power supply.
4 2600 mcd LEDs
Wire
Soldering iron/solder
Steps:
Soldered wire to the long lead of the LED as positive. Soldered wire to the short lead of the LED as negative.
Did this for all four LEDs.
Cut off the end of the power supply to expose the wires.
Individually connected each LED to the power supply to make sure it was working.
Soldered the ends of all four positive LED wires together.
Soldered the ends of all four negative LED wires together.
Connected the positive portion of the LED wires to the positive end of the power supply.
Did the same for the negative side.
Plugged in the power supply and marveled at my own work. They lit with a great intensity, and stayed lit... for about two minutes.
One by one each bulb went to a pale green and then extinguished completely.
I broke everything down to its component parts and individually connected each LED to the power supply. Nothing.
So, what step did I miss?
The LEDs say they use 3.7 volts, and Im using a 6v power supply. Did I run too much juice through them? I have a 3.7 volt power supply from an old cell phone charger, should I try that next? Anything else Im missing?
Thanks.
Im slowly becoming an electrician in addition to a reef keeper.
 
gatorcsm

gatorcsm

Member
You didn't use resistors. Without resistors you're shorting out the powersupply. That means 6v divided by a resitance of... let's say .5 ohms... That means you had a current maybe as high as 12 amps. That will do it.
Put atleast a 20 ohm resistor in series.
 
salvatore

salvatore

Member
How many amps are your LEDs rated for?
The RadioShack site says the following about the LEDs:
"Wavelength: 468 nm (typ.), Type: T-1-3/4 (5mm), Lens Color: Clear, Viewing Angle: 30°, If mA: 20 (max.), Vf: 3.7 (volts typ.), Vf: 4.5 (volts max.)"
So...20mA?
I need to add a resistor to the mix? More than one?
To add a resistor, I insert it where? In line with the positive lead?
Thanks.
 
salvatore

salvatore

Member
300mA is the rating on the 6v. 800mA on the 12v I have and I think 200mA on the 3.7v p.s.
I was able to figure this out, though. I used the 3.7v supply, a 100 ohm resistor and three LEDs. Works great and I'll probably re-do everything to include more and brighter LEDs.
Thanks.
 
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