Wiring up LED's? Amateur Question
Wiring up LED's? Amateur Question
(OP)
I have a question with regards to LED's. I have a power supply that supplies 3, 41/2, 6, 71/2, 9 and 12VDC (nominal). Materials I'm using:
Aforementioned power supply
Circuit board
~80 Red LED's, "high" intensity ( http://www.jameco.com/webapp/wcs/stores/servlet/Pr... )
Connecting wires, soldering gun, etc etc
Assuming a voltage drop of 1.9V across each diode
How would I light 80 LED's if the combined voltage drop in SERIES is 80*1.9V?
All LED's will always be on when the power source is on. (The LED's will not be on-off intermittently or controlled by an IC)
Advice?
Thanks
Aforementioned power supply
Circuit board
~80 Red LED's, "high" intensity ( http://www.jameco.com/webapp/wcs/stores/servlet/Pr... )
Connecting wires, soldering gun, etc etc
Assuming a voltage drop of 1.9V across each diode
How would I light 80 LED's if the combined voltage drop in SERIES is 80*1.9V?
All LED's will always be on when the power source is on. (The LED's will not be on-off intermittently or controlled by an IC)
Advice?
Thanks





RE: Wiring up LED's? Amateur Question
Most LEDs have their characteristics specified at a current of 20 mA. If you want really good reliability and you are not certain you don't have worse-than-average heat conductivity in your mounting, heat buildup in wherever you mount them, voltage/current variations, etc. then design for 15 milliamps. I am designing for 15 mA.
The 1.9V drop is safe to assume for high-brightness, high-efficiency and low-current red. This is what I am using.
http://politicalplangetis.blogspot.com/
RE: Wiring up LED's? Amateur Question
TTFN
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RE: Wiring up LED's? Amateur Question
http://politicalplangetis.blogspot.com/
RE: Wiring up LED's? Amateur Question
Be sure to size the resistor for power dissipation in addition to impedance.
Mike Halloran
Pembroke Pines, FL, USA
RE: Wiring up LED's? Amateur Question
What truth do you see to this statement?
"Do not put LEDs in parallel with each other. Although this usually works, this is often not reliable. LEDs become more conductive as they warm up, which may lead to unstable current distribution through paralleled LEDs. LEDs in parallel need their own individual dropping resistors. Series strings can be paralleled if each string has its own dropping resistor."
This makes me wonder, should I have a resistor in series with EACH of the LED's in my parallel chain? Or is this statement not true.
http://politicalplangetis.blogspot.com/
RE: Wiring up LED's? Amateur Question
RE: Wiring up LED's? Amateur Question
TTFN
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RE: Wiring up LED's? Amateur Question
I also found a great little tool recommended to me by the store I'm purchasing my LED's from (Jameco). VERY useful for my application. http://led.linear1.org/led.wiz
http://politicalplangetis.blogspot.com/
RE: Wiring up LED's? Amateur Question
If you really want to build your own then use HBLEDs not those gumdrops. Go look at LEDGroupBuy or some other aquarist DIY lighting site and see how to do it the 'modern way'. That way you use 6, 12, or 24 LEDs to get you 2, 4, or 8 times more light.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Wiring up LED's? Amateur Question
RE: Wiring up LED's? Amateur Question
itsmoked - I'm not using the LED's to grow anything.
http://politicalplangetis.blogspot.com/
RE: Wiring up LED's? Amateur Question
why not stick them in series and put across the line? If I was doing it, I would start with a 10k resistor in series with them to limit current, lowering it in steps until the series ammeter showed 15ma or the brightness you want.
RE: Wiring up LED's? Amateur Question
RE: Wiring up LED's? Amateur Question
RE: Wiring up LED's? Amateur Question
TTFN
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RE: Wiring up LED's? Amateur Question
Keith Cress
kcress - http://www.flaminsystems.com
RE: Wiring up LED's? Amateur Question
RE: Wiring up LED's? Amateur Question
Of course the approach can be made to work (á la Xmas tree LED strings), that's not the point. The issue is directing an obvious neophyte to play with AC line voltages, with not a word of caution. It seems arguably a bit careless.
We cannot address the question of the optimum series-parallel arrangement for the LEDs without knowing more details of this available power supply.
A power supply that provides "3, 41/2, 6, 71/2, 9 and 12VDC" sounds suspiciously cheap and perhaps of limited capabilities. We need to know the maximum current output at each voltage setting. It's likely that the optimum voltage setting is the maximum 12v, but this assumption should be confirmed.
RE: Wiring up LED's? Amateur Question
RE: Wiring up LED's? Amateur Question
RE: Wiring up LED's? Amateur Question
Thanks for everyone's input. No I am not going to use 120VAC. I am using a 12VDC NOMINAL supply and it is by no means accurate - I'm buying the thing for $25. BUT for my purposes it is fine.
No more comments needed here. This thread can be closed. Thanks
http://politicalplangetis.blogspot.com/