Easiest way to get stable 12vdc for LED array?

[dma251]

I bought these led boards from ebay for my hexa, and I am trying to come up witht the lightest and simplest method to supply them with steady voltage.

http://www.ebay.com/itm/250924448338?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649#ht_5047wt_922

[lperagallo]

I would run them directly off a 3S lipo battery. I use 12V strip LED lighting and I am hooked up directly to my Deans so when I connectteh battery they come on. A fully charged 3S pack is 12.6 volts so I don't think you will hurt that board.

Lou

[jamesb72]

The description says 11-13v so 3S should be fine.

I have another question, I've bought some 5mm ultra bright LEDS to put in my 'tub' for orientation (plan to hot glue a couple of white at the front, red at the back), I was planning on running these on the 6v off receiver pins - should I connect the 4 LEDS in parallel (ie 6v across each), or in pairs in series (ie 3v across each??) - I can't find voltage specs on these anywhere ??

[Tomstoy2]

In parallel.

[jamesb72]

Just trying to wire up the LEDS, I've already puffed out two red LEDS, running them off a 4 cell nimh rx pack to test.

Do I need a 100Ohm resistor inline with the LED's, or can I just connect them in parallel across the 6v input ??

[chansen1953]

james, all LED's need a low voltage resister to reduce the current. which should be in series in the circuit. The led strips have a series resister built-in on the strip board..but if you are connecting up individual LEDs then you need to add the RESITOR.. ( a low wattage 1/4 to 1/2 watt size is fine)

I have just wired my quad with pairs of REd, Green and White hi-brite LEd='s as follows..
red/green are on the rear, port/starboard and the whites are on the front arms

2 x RED LEDs in parallel, with a 1K ohm series resistor , wired to the main power plug
2 x GREEN LEDs in parallel, with a 1K ohm series resistor , wired as above
2 x WHITE LEDs in parallel, with a 1K ohm series resistor , wired as above
2 x WHITE LEDs in parallel, with a 1K ohm series resistor , wired as above

The total drain on the circuit is just around 150 ma, which in nothing, and it does not have to be stable or a separate supply, as it causes negligible drain on the whole system and the only effect of a voltage drop in the circuit wil be a slight dimmimg of the led's..

as far as brightness goes, it is harble descernable if I use a 500 Ohm series resister or a 2000 Ohm , as it is the current that is reduced, the higher the resister value goes.
Basically you want to get a resister size that still has nearly full brightness, but does not allow to much current to flow, which will generate heat and blow the LED..

I found 280Ohm to get quite hot, so I moved up to 500-1000 ohm and it was cool and still plenty bright !

hope this helps mate !!

[jamesb72]

Thanks Chris, thats brilliant, will order some resistors.

One more question, I found some flashing LEDS which have Vdd of 5-6v, does this mean I can run them directly on 6v or do I always need a resistor inline to reduce current ? (ie is Vdd the voltage needed across the LED, so if its less than supply voltage you need a resistor to drop/share voltage, or is the resistor ALWAYS needed to stop the LEDs taking too much current regardless of their Vdd).

I plan to run the LEDs from 6v (plugging into a spare reciever port, so running of the BEC voltage inside my tub) - this is for convenience, as saves running extra wires into the tub. Someone I know is running LED's with 68ohm resistors, this seems lower value than what I saw on the LED Calculator online (for 6v two LEDs it came out with 100-150ohm, red in series, white in parallel).

[chansen1953]

James,

The Flashing LED's have inbuilt series resistors, so can be put onto any voltage upto about 12V , certainly no problem directly onto your 3s cells or onto the BEC voltage !1

The 68Ohm is a bit low, depending on the voltage, , but this will just cause excess hea tin the resistor.. you need to use a few hundred ohms at least so that the current is lowered.. otherwise you get too much wasted heat.. and power consumption..

As I said above,, if the series resistor is too low, it may not blow the LEd, but it will get hot, and you are just wasting powrer on heat ...

using a 6V supply, anywhere from 300-600 ohms is fine, just turn on and hold the resister to see if it gets warm.. ..too warm.. increase the resistor value... it is not critical, just anything below 100ohms will get hot and waste power... over 1k ohms,, the led starts ot get a bit dull !

[jamesb72]

Thanks Chris, I got some 68 and 82 ohm resistors from someone at the club, have wired the LEDs up with 82ohm seperate resistor for each LED, the two white (brightest) LEDS are drawing 60ma between them - I will check if they get warm but hopefully this should be OK.

I plan to order some more LED's flashing and brite, so will get some bigger resistors for stock at the same time.

[Windbreaker]

When I created an LED light bar for my aquarium, here's where I got the resistor values and a schematic.

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

You provide the input voltage, and other specifications, and it'll give you all the necessary details.