# Green LED fishing lights.

Discussion in 'The Projects Forum' started by bundick, Aug 12, 2010.

1. ### bundick Thread Starter Active Member

Dec 19, 2007
97
1
I got a bunch of 5 mm Green LED's off Ebay.

Now I'm going to make a circular ring of Green LED's.

* Emitted Colour : Green
* Size (mm) : 5mm
* Lens Colour : Water Clear
* Peak Wave Length (nm) : N/A
* Forward Voltage (V) : 3.2 ~ 3.8
* Reverse Current (uA) : <=30
* Luminous Intensity Typ Iv (mcd) : Average in 8000
* Life Rating : 100,000 Hours
* Viewing Angle : 20 ~ 25 Degree
* Max Power Dissipation : 80mw
* Max Continuous Forward Current : 30mA
* Max Peak Forward Current : 75mA

I know you have a pretty good LED tutorial on this site, but maybe this one time you could provide me with the size of the load resister for 30 of the LED's mentioned.

2. ### retched AAC Fanatic!

Dec 5, 2009
5,201
313
12v will not run 30 of these leds in series.

They each have a ~3.2v drop so you would need about 96v to operate this circuit as is.

3. ### Bernard AAC Fanatic!

Aug 7, 2008
4,240
414
I made some 9 LED strings, maybe a little time consuming but I checked V drop of of all 27 & put them in 5 piles of = V. Estimate average V drop for 3 in series & build up the strings so all have close to same combined V drop. You need 10 strings in parallel of 3 LEDs & a resistor comprising each the strings. Assume strings measure 10.8 V, 12V - 10.8V = 1.2V[ a little skimpy] 1.2V /.025mA=48Ω @ .o3W or 1/4 W & next higher std value is 51Ω. To measure V drops use 12V source, with a diode & 330Ω 1/2W resistor in series with LED under test, cathode to battery neg. Two parallel rods were taped to bench to make a LED socket, with V meter connected between them. Diode is to prevent smoke from reversed LEDs

4. ### bundick Thread Starter Active Member

Dec 19, 2007
97
1
That was quite a wakeup call. I realized while doing the math that I'm too far and too long out of school.
I have a 12V supply a 51-Ohm resister and a Diode to 3 green LED's. That makes one circuit using 90 ma.

I've always wondered if that's 90 ma per second? Hour?

5. ### Bernard AAC Fanatic!

Aug 7, 2008
4,240
414
Ten strings @ 25 mA each = 250 mA. Value of resistors will depend on measured V drop of strings.

• ###### Green LEDs 00000.jpg
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May 11, 2010
241
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Amps is a measure of current, which is a rate... it's just 90 mA, not per second or per hour.

Amps *is* a rate, like gallons per second.

1 femtoAmp is about 6,000 electrons per second. That helps me to put it in perspective.

One mA is then about 6,000,000,000,000,000 electrons per second.

7. ### bundick Thread Starter Active Member

Dec 19, 2007
97
1
Thanks Sage. I always used the ma as a part of a formula without ever realizing how long a Battery could last at that rate.

BERNARD, you drawing put it all into perspective for me. Thanks for making that clear for me. It's exactly what I asked for.
Dick