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        Discussion Running LEDs off Flight Battery

#1 HoosierGuy Sep 28, 2012 03:43 PM

Running LEDs off Flight Battery
 
I've done two flights now with LED lights on my glider and I love it. I'm hooked!
I've been using a 2200mah 3 cell for my flight battery and smaller 800mah 3 cell to power my LEDs. I would now like to get rid of the smaller battery and power everything off my flight battery through the balance charger.

Where do I get those connectors so I can connect my LEDs to the battery balance connector? Is there anything I should now about wiring everything up?

Thanks!

#2 Timtreo Sep 29, 2012 02:31 AM

Here you go they start at the bottom of the page http://www.rc-connectors.com/index.p...ort=20a&page=2
As for wiring them I'm in the same boat as you. been using a separate lipo but would like to run my heli frame lights off of 2 cells of my 3s main battery. Hopefully someone will chime in :).

#3 C₄H₁₀ Sep 29, 2012 04:35 AM

It's dead-simple if the LEDs are already set up to run off a 3S lipo. Just replace the normal connector with the balance one; the outer two pins will connect to all the cells in series so it's just like a regular battery.

The only thing to note is that if this is a powered glider, the voltage will fluctuate a bit depending on motor current draw (~2-2.5V down from a full charge for an average 3S setup), so the LEDs will change in brightness slightly,

Quote:

As for wiring them I'm in the same boat as you. been using a separate lipo but would like to run my heli frame lights off of 2 cells of my 3s main battery. Hopefully someone will chime in :).
Running them off two cells from a 3S pack is possible but not really ideal. I'd say just go with the full three cells and then add a resistor in series to cut down the extra input.

#4 Timtreo Sep 29, 2012 04:54 AM

Hey thanks butanol:), that is probably a better idea for me to just use a resistor if they are too bright at 12V. Just wondering though if I did want to use 2 of the 3 cells for anything would it be the red balance wire for + and then the 3rd black wire over from that for - ? Thanks again, Tim

PS One more thought, would a resistor(s) restricting around 4 volts waste that energy has heat or would it just restrict the electricity from ever getting to the LEDs and still be able to be used by the rest of the electronics (motor, servos, gyro) running off the main battery?

#5 C₄H₁₀ Sep 29, 2012 05:10 AM

What voltage are they set up to run off now? If they're only set up to run off two cells, then going to three directly will cause more than just additional brightness- it'll most likely cook them. Their current draw spikes up sharply when you go a bit past their normal running voltage (usually like 3-4V for most of the ones we use).

To run them off two of the three cells, just connect them to pin #1 and pin #3, or pin #2 and pin #4. They'll obviously only let current flow if you get the polarity right. The red balance tap wire is usually connected directly to the positive pack lead, and the black is usually connected directly to the negative lead, and then each adjacent pair of wires (1+2, 2+3, 3+4) will connect to one cell. (Thinks): "I wish I had a picture to explain it better"... Ah, wait: Google to the rescue:

https://f47fb5b4-a-62cb3a1a-s-sites....attredirects=0

#6 C₄H₁₀ Sep 29, 2012 05:11 AM

I don't think that one worked. Google to the rescue... Again :rolleyes:

http://seantu.com/RC/Pictures/3s_wiring.png

#7 Timtreo Sep 29, 2012 01:54 PM

Thanks again, awesome explaination and pic! And thanks to the OP for starting this thread. My LED strips can handle 12V, they have resistors every 3 LEDs or so. I was running them off a 2 cell battery because they were too bright because I use heli night blades also, (these - http://www.rcgroups.com/forums/member.php?u=433840) and with too much frame LED light the whole heli can become a blur. But I am going to add some RGB strips and controller (got from fellow member Bombay http://www.rcgroups.com/forums/member.php?u=207250) so I'll see how 12volts total works out with all of them. Thanks again!

Anyone care to tackle this question?
Quote:

One more thought, would a resistor(s) restricting around 4 volts waste that energy has heat or would it just restrict the electricity from ever getting to the LEDs and still be able to be used by the rest of the electronics (motor, servos, gyro) running off the main battery?

#8 C₄H₁₀ Sep 29, 2012 02:11 PM

Resistor... Current equals voltage divided by resistance. Increasing voltage and adding resistance lets you keep the same current flowing. Running the higher voltage with an inline resistor means you have more potential ahead of the resistor, but (for a given LED brightness factor) the circuit will still be using the same amount of current as it did on the old power source. Going up to the full 12V will mean more current draw and brightness, but the light strips can handle it.

At ~12.4V, I measured one of those light strips (36-LED type, blue) drawing something like 0.4A, which could run off a 1000mAh pack for two hours before you needed to charge, so you won't see much of an impact on flight time either way.

#9 Timtreo Sep 29, 2012 11:29 PM

:) Ok I think I get it, thanks again.

#10 Barn-E-Stormer Oct 03, 2012 05:19 AM

2 Attachment(s)
The balance tap is great place to tie in lights. I have bags of the connectors, I got from DigiKey. Long lead time but if you pay for them up front you will eventually get them. PM if anyone wants one for $1.

The resistor question: You stated 4 volts across the resistor but did not specify the current, so we need to set some parameters. 1 meter of LED strip draws 200ma @ 12V. If the current is limited to 70ma the strip is still plenty bright. So P=I*E or 4*.070=.28W So our answer is just over a quarter watt, you will need a half watt resistor. (This refers to the size of the resistor body.

Now E=I*R so we have 4E and .070I. Solve for R, R=E/I or 4/.070=.057
57 is a 5% R value, so you need a 57 ohm, half watt resistor to give you a voltage drop of 4 volts and 70ma.

You can also make my dimmer switch.

#11 HoosierGuy Oct 05, 2012 03:02 PM

Along with ordering some leds that change color and flash from Hobbyking, I also ordered a connector cable that hooks up the battery balance connector to six or seven JST (I think they are called JST) connectors. This will really help me with my electric glider. It has way too many cables with my solder connections running inside. I need to downsize a little. Hopefully the connector will help.

#12 tonto458 Oct 12, 2012 11:17 PM

Running leds off of flight battery
 
I have been flying with LEDs for several years and all you have got to do is get a two prong micro plug and wire it to your LEDs and plug it into the ground and the first battery balance port and the lights will be bright and will not drain the cell anymore than if you flew the plane during the daytime in normal flight.

#13 HaventFlownSince2014 Oct 16, 2012 02:53 PM

Here is my experience without getting scientific or complicated. When not using hundreds of LEDs, you can use one pack. My ship's LEDs burn approximately 500 mAh of 3s battery every 4:30 minutes, so it is not smart for me to power them off of my 2200 mAh flight battery because of the excessive draw.

As mentioned above, also avoid using one battery when flying high powered setups. As you put the throttle to the coals, LEDs will fade- very bad thing to happen when you have several hundred dollars in the air... so for good measure it would be best to run separate batteries for LEDs on something like a warm or hot liner. When pushing the flight battery hard and running LED's off of the same battery, one can easily LVC without much warning.

My rule of thumb is any park flyer with under 250 or less LEDs needs no separate LED battery. In larger planes, redundancy is highly important and I highly recommend separate batteries.

#14 Robertos3 Oct 28, 2012 07:16 AM

pretty interesting post



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#15 jpheli Nov 21, 2012 12:00 AM

If you need any custom activity on LEDs. You can program your own patterns etc easily with Arduino. Check out jD-IOBoard, it's a small Arduino board made just for this type needs. There are 6 high voltage outputs that can drive about 500mAh each. Analog inputs and so on so you can check your battery voltages etc while flying and if voltage drops too low you can have warning lights.
One way to save some mAh's is to make strips/LEDs to blink fast and you can basically save 50% on current and still it looks like lights are always on.


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