Help from you electrical guru's pleeeaaase!

[nate80]

I';m in the middle of a F550 hex build and I';ve realised that I want to install some orientation lights.  I';ve done some research and had a good look around and have decided I';d like to install super bright LED';s, one beneath each arm (red on the two front arms and green on the other four arms).  So it looks like this:

[attachimg=1]

I';ve read that the brightest and best LED';s for this are 1W High Power LED';s with PCB, like these:

http://www.ebay.co.uk/itm/1-5-10-pcs-1W-3W-10W-High-Power-LED-with-PCB-Grow-lights-aquarium-LED-UK-COB-/131345637382?var=&hash=item1e94cf6006:m:mHleecjnrWfBVFJlszb8PPQ

But this is where I';m a bit (aka, pretty much completely) lost.  I';ve seen photos of this guy that installed an LED on each arm and soldered it to the ESC output on the PCB board.  He used a resistor wired in-line between the ESC power outputs on the PCB and the LED light, but he didn';t say which one.

[attachimg=2]

[attachimg=3]

I';m going to run a 4S liPo (and sometimes 2 x 4S in parallel) on my DJI f550 hex.  Can anyone help by telling me what resistor I will need to install to carryout the same set up on my hex and stop the led ';s from overheating or doing any damage to my multi-rotor please?

Thanks   

[nate80]

I';ve seen these (from the UK) which are advertised as 12V input.  4S LiPo';s are obviously 16.8V so I guess these wouldn';t be any good?

http://www.ebay.co.uk/itm/12V-AC-DC-LED-Driver-600ma-1-3-x-3W-Power-Supply-Constant-Current-MR16-N450-/221767993502?var=&hash=item33a267089e:m:mi8NNgK8AfvNd4qrgn_RE7w

Only reason I ask is that I saw some (from China) that look really similar and that were advertised as 12V, but in the description it said they could handle up to 24V.

[guest325]

If you wire 6 of them in series then the voltage each LED will see is 1/6th of the supply voltage.
Reds are usually about 2.0 - 2.6 volts and greens are about 3.0 - 3.5 volts it';s the supply current that kills LEDs as long as the voltage is reasonably close.
So you will have 4 x 3.0 + 2 x 2.0 = 14 Volts, I think that you may not need resistors.
I would guess he wired them individually so would have to have dropped the Voltage.

[nate80]

Many thanks Darrell.  Yeah, I think he did wire them individually, to cut down on unnecessary wire length and weight.  It does look super tidy, each LED wired to the ESC output on the PCB.

If I were to wire 6 in series I guess I could solder them directly to the battery cable posts on the PCB?  And would all the LED';s illuminate to the same brightness (no power drop) if wired in serial?

[guest325]

Have a look at this:
http://www.instructables.com/id/LEDs-for-Beginners/step7/Wiring-up-multiple-LEDs-in-series/
Series wiring means you run a single cable around from the one polarity in daisy chain and the end goes to the opposite polarity, so no real disadvantage you still have only 2 wires going up each arm.

[nate80]

Doh!  Sorry, I was having a thick moment.       Of course!  Thanks again.   

Out of interest, I';d still be very interested to know the answer to my initial query about running a resistor for each of the 6 LED';s powered off the ESC power output on the PCB.  It would help keep things very tidy.

[guest325]

Out of interest, I';d still be very interested to know the answer to my initial query about running a resistor for each of the 6 LED';s powered off the ESC power output on the PCB.  It would help keep things very tidy.

If you want it to be bomb proof run it in series off a 5A BEC, putting resistors in wastes battery power as heat

[nate80]

If you want it to be bomb proof run it in series off a 5A BEC, putting resistors in wastes battery power as heat

Great, sounds very sensible.    Using a 5A BEC looks like a good safety net.

Would you say I have the choice of running 6 x 1W or 6 x 3W LED';s.  The fact sheet on the eBay item webpage says:

6 x 1W = 16.0V - 19.6V Max

6 x 3W = 16.8V - 21.6V Max

Do you reckon 3W would be considerably brighter/beneficial/safe?!  Or should I stick with 1W?  I';ve read that there isn';t that much difference in luminescence between 1W and 3W?   

[guest325]

You get more light off a 3W but no more brightness - I know that sounds strange but your perception of the difference is only really more noticeable at short range.
The biggest difference is that they draw double the Amps so really not worth it 

[quadfather]

I agree with Darrell and suggest a regulator of sorts, perhaps the the BECs on your ESCs (if they have them).  Looking at the second image in your OP the builder seems to have used a regulator, perhaps an LED driver.  You can see it partly obstructed by the arm.

Out of interest, I';d still be very interested to know the answer to my initial query about running a resistor for each of the 6 LED';s powered off the ESC power output on the PCB.  It would help keep things very tidy.

To figure out the resistor value for a single LED in circuit you use Ohm';s Law, R = V / I.  In this case V is the voltage supplied minus the forward voltage of the LED (which changes depending on the colour!).  I is the forward current of the LED.  I';m using the example of a 5 V regulator with the green LED from your eBay ad.

V = 5 V - 3.6 V = 1.4 V
I = 350 mA = 0.35 A
R = 1.4 V / 0.35 A = 4 Ω

The next bigger resistor from the (most commonly available) E12 range is 4.7 Ω.  This would put the current on the LED at ~ 300 mA, which is below the max rated.

To calculate the wattage of the resistor (it needs to be able to handle the "heat") we use, P = V² / R. Here V is the voltage difference between the source and the LED again, and R the resistance we calculated above.

P = 1.4² / 4.7 = 0.42 W

You can get 0.5 W resistors, but taking tolerances into account I would go for the next bigger thing, i.e. 1 W.

Adjust the numbers as you see fit, e.g. you may not want to run the LED at 3.6 V since that';s the max rated.

Hope it helps. 

[nate80]

You get more light off a 3W but no more brightness - I know that sounds strange but your perception of the difference is only really more noticeable at short range.
The biggest difference is that they draw double the Amps so really not worth it 

Thank you!  I really appreciate the help.   

By any chance is there a 5V BEC that you prefer/would recommend?  I';ve not bought one before so I don';t know if their are any stand out examples?

[nate80]

I agree with Darrell and suggest a regulator of sorts, perhaps the the BECs on your ESCs (if they have them).  Looking at the second image in your OP the builder seems to have used a regulator, perhaps an LED driver.  You can see it partly obstructed by the arm.

To figure out the resistor value for a single LED in circuit you use Ohm';s Law, R = V / I.  In this case V is the voltage supplied minus the forward voltage of the LED (which changes depending on the colour!).  I is the forward current of the LED.  I';m using the example of a 5 V regulator with the green LED from your eBay ad.

V = 5 V - 3.6 V = 1.4 V
I = 350 mA = 0.35 A
R = 1.4 V / 0.35 A = 4 Ω

The next bigger resistor from the (most commonly available) E12 range is 4.7 Ω.  This would put the current on the LED at ~ 300 mA, which is below the max rated.

To calculate the wattage of the resistor (it needs to be able to handle the "heat") we use, P = V² / R. Here V is the voltage difference between the source and the LED again, and R the resistance we calculated above.

P = 1.4² / 4.7 = 0.42 W

You can get 0.5 W resistors, but taking tolerances into account I would go for the next bigger thing, i.e. 1 W.

Adjust the numbers as you see fit, e.g. you may not want to run the LED at 3.6 V since that';s the max rated.

Hope it helps. 

That';s very useful info.  Thanks very much.   

The ESC';s I';m using are hard plastic sealed DJI ones, so I couldn';t get to the BEC inside them (if there even is one).

From what you';ve shared I believe that one of these drivers per LED would work fine?  My only concern is that they';re listed as 12V and a 4S LiPo is obviously 16.8V.

http://www.ebay.co.uk/itm/221767993502?_trksid=p2055119.m1438.l2649&var=520614622684&ssPageName=STRK%3AMEBIDX%3AIT

[hoverfly]

http://www.hobbyking.com/hobbyking/store/__31693__TURNIGY_3A_UBEC_w_Noise_Reduction_EU_Warehouse_.html

The above are quite good, I';ve used a few of them on slope soarers and had no problems. The go in and out of stock quickly.!!

[nate80]

http://www.hobbyking.com/hobbyking/store/__31693__TURNIGY_3A_UBEC_w_Noise_Reduction_EU_Warehouse_.html

The above are quite good, I';ve used a few of them on slope soarers and had no problems. The go in and out of stock quickly.!!

Thanks, I was looking at these a little earlier.  Real shame they';re out of stock.  Given my experience with HK re-stocking times I';m not sure I';m wanting to take the chance and wait on those.

From what you';ve shared I believe that one of these drivers per LED would work fine?  My only concern is that they';re listed as 12V and a 4S LiPo is obviously 16.8V.

http://www.ebay.co.uk/itm/221767993502?_trksid=p2055119.m1438.l2649&var=520614622684&ssPageName=STRK%3AMEBIDX%3AIT

Is anybody electrically minded able to confirm whether these would do the trick, please?   

[nate80]

Looks like I';m going to have to go back to the beginning as I seem to have become more and more confused.   

To be honest, I';m overwhelmed right now.  Maybe I shouldn';t have started looking into 3D printers until I';d finished my other projects!   ;D   A current relapse of depression isn';t helping either, truth be told.  I';m finding it quite difficult just to piece sentences together properly at the moment.  But, onwards and upwards. 

Trying to build my first multi is difficult enough as it';s pretty much all new to me, like how the equipment all works (FC';s, RX';s, VTX';s, OSD, Action cam as FPV and recording device, Gimbal etc.  Plus what talks to what and how it talks to each other, Sbus, PPM, telemetry, setting up a taranis etc.  And, of course, LED lights.

I thought I understood the basics of running an led through a driver that would regulator the current being drawn from the PCB at the ESC power outputs.  And I thought I understood that it would be possible to run 6 x 1W led';s in series directly from a 4S battery.  Then I thought it was good practice to install a 5V BEC, but now that doesn';t seem to make sense as the LED';s will draw 16V and wouldn';t illuminate properly if run through a 5V UBEC.  And I';m reading that I will need to run resistors to limit the voltage even if I run 6 x LED';s in series off of a 12v supply.    

I managed to place an order for green and red 1W High Power LED';s, so that';s something!   

I think I need to take a step back, take some deep breaths, and start again.

[guest325]

Sorry, the 5A BEC was a bump steer, it is only 5V I forgot.
I still think that the best way is to connect in series and if you want to protect the circuit just put a fuse in line (5A would ok).
The other alternative is to make them switchable using a RC switch and run it through the Gear channel.

[pheasant_plucker]

http://www.ebay.co.uk/itm/LM2596S-DC-DC-Constant-Current-and-Voltage-Adjustable-Module-LED-Driver-/141304467644?hash=item20e66710bc:g:jbUAAOxynwlTcgAl

you will need one for each set if leds if they have a different forward voltage so set your green and reds in 2 different strings and set the voltage and current.

gerry

[subpixel]

Just get 2 MR16 LED drivers, 1 for the red and 1 for the green. make sure they are 1w (300ma) ones and connect the LEDs in series to the driver, simples.

Ignore the input voltage rating listed on any MR16 listing as they are all good for at least 25v and make sure you only get 1w LEDs as they will run hot enough as it is.

For a different arrangement you could get a 3W (700ma) MR16 driver for the reds and a 10w (1000ma) driver for the greens and wire the LEDs in parallel.

Get 28AWG silicone wire for wiring them up as well.

[nate80]

Sorry, the 5A BEC was a bump steer, it is only 5V I forgot.
I still think that the best way is to connect in series and if you want to protect the circuit just put a fuse in line (5A would ok).
The other alternative is to make them switchable using a RC switch and run it through the Gear channel.

Hey, no worries.  I think I was getting myself confused anyway.   

http://www.ebay.co.uk/itm/LM2596S-DC-DC-Constant-Current-and-Voltage-Adjustable-Module-LED-Driver-/141304467644?hash=item20e66710bc:g:jbUAAOxynwlTcgAl

you will need one for each set if leds if they have a different forward voltage so set your green and reds in 2 different strings and set the voltage and current.

gerry

Cheers Gerry.  Funny enough I had looked at those ones during my research.   

[nate80]

Just get 2 MR16 LED drivers, 1 for the red and 1 for the green. make sure they are 1w (300ma) ones and connect the LEDs in series to the driver, simples.

Ignore the input voltage rating listed on any MR16 listing as they are all good for at least 25v and make sure you only get 1w LEDs as they will run hot enough as it is.

For a different arrangement you could get a 3W (700ma) MR16 driver for the reds and a 10w (1000ma) driver for the greens and wire the LEDs in parallel.

Get 28AWG silicone wire for wiring them up as well.

Thanks very much.  That';s exactly what I needed.    

I think I was pretty overwhelmed with things yesterday, so I just took the evening off and started again today.  Sometimes you just need a break.   

Cheers, that';s so helpful and is in line with some of what I was thinking.  I was surprised you said 28 AWG, only because it';s so physically thin, but you';re absolutely right.     I looked on this handy AWG table:

http://www.powerstream.com/Wire_Size.htm

I ended up buying 26AWG silicone wire, only because it was cheap and would be delivered quickly.  And I bought these MR16 drivers:

http://www.ebay.co.uk/itm/221738699994

I bought 10 as they were cheap and it means I can still decide whether I want to run the lights in series (one loop with 1 resistor for red, one loop with another resistor for green) from the main power points on the PCB, or run each led off it';s own resistor from the PCB';s ESC power points.

The Green and Red 1W LED';s turned up already!  I only ordered them yesterday!

http://www.ebay.co.uk/itm/131345637382?_trksid=p2057872.m2749.l2649&var=430892055981&ssPageName=STRK%3AMEBIDX%3AIT

I';m looking forward to seeing how they look.   

Thanks again.   

[Saleem]

4 strobon standalones!

I have never seen an led with my own eyes that shines so much.i am certain it';s got to do with the lens they fit,there';s an idea for you,try flytron and look at their lens.i gotta strobon standalone today and I can safely say at this moment in time I am happy with it even though I ain';t flown with it yet.you can see the blast of light from it,it';s like a mini explosion.

Expensive?at £11.40 delivered for 1 I think as long as it lasts it';s a bargain.

I put on mine not for me but for everyone else so it serves as a warning that it';s there.just hope it won';t gather crowds all looking in awe!

[nate80]

Interesting little product that Saleem.  Looks good for quick fixing to quad in the field, or fully encased drones like Phantoms that are a pain to wire up an LED to.   

[nate80]

All the orientation lighting bits have now arrived.  I';ve been thinking about my requirements and I reckon I';ve come up with the best wiring solution solution that will allow the LED';s to run at max efficiency with least power consumption.  I also decided I definitely want it wired up to a remote switch as the LED lights could negatively affect photography in some instances.

The MR16 drivers support 1-3 1W LED';s, so as the red and green LED';s need to be powered separately from each other (due to differing voltage and current draw) I plan on using 1 driver per 2 LED';s.

The only thing I';m not 100% sure about is whether they will run slightly dim in a series configuration rather than parallel.  All the LED electrical guides I';ve come across say to run LED';s in parallel to avoid voltage drop.  But all these guides I';ve seen have been talking about LED lights capable of running directly off a 12V DC output, and therefor share the 12V between the LED';s when run in series.  These 1W High Power LED';s may be able to run in pairs within a small series circuit fed from a single MR16 driver without any dimming issues?  I don';t know?

The driver is rated at 1-3 x 1W, but does that mean in series or only in parallel?

[attach=1]

[guest325]

We run 5X 1W led';s in series in my design Electric fires no real issues at all provided that you are running in the driver parameters. Be careful about wiring in parallel because it is possible  (if the output voltage of the driver is higher than the forward voltage of the led) to get the led';s flashing because the driver is going into the overload cutout.

[nate80]

MR16 LED drivers are only rated to power 1-3 1W bulbs, which is why my wiring plan uses the 3 drivers.  The drivers are output a max 300mA and a voltage equal or less than the input voltage - based on what the LED';s require.  Theoretically there shouldn';t be any overheating issues whether in series or parallel.

The only slight overheating issue I have is with the LED itself.  It';s mounted on an aluminium PCB/heatsink (which is ok but not the best at dissipating heat), and will be placed underneath the props, so I don';t think there will be a heat issue, but time will tell.

[guest325]

The forward current of Green is usually 350mA and Red 400mA for 1W, before you actually fit then I would test them (possibly by wiring them in choc block. If you connect in series you add the voltages of the led';s together but they run at the same current, in parallel you add the currents together but the voltage stays the same; as I said it may not work - if there is no overload circuit then it will work for a time but then something will eventually go phut!!!

[nate80]

You';re spot on: 350ma and 400ma.      All the specific stats are logged on my wiring diagram too.

Yes, I see what you mean.  I';ll be sure to test before final wiring / soldering.  I think I';ll be wiring the led';s after the driver in serial anyway, as is shown in my wiring digram.

All the MR16 drivers get the full 12v (as required) and then each driver provides a constant current of 300mA to 2 LED';s run in series.  The LED';s might not illuminate at 100% brightness (350mA and 400mA, as you said) as they are only being fed 300mA, but that';s still plenty bright enough.  I';ve tested them and the LED';s are blindingly bright.

[guest325]

In your case the result will be not as bright but if the amount underdriven is too much they might not emit light at all, there is a way round this problem that is by using dimmable led';s - these are specifically designed to be tolerant of being underdriven.
The thing to remember is that you will have 300mm off the driver but up to 12V going into just over 5V of led';s so how well it will work will depend on if the driver has current limiting, if not you could get thermal runaway and burn the led';s out - I would leave them running in your test circuit for at least a few hours to make sure you don';t have to take it all apart at what could be frequent intervals.

[Saleem]

Buy some of them lens covers if suitable for your less from flytron or wherever you can find them.theh certainly will make a difference as they make the light explode in a given angle making them more visable.

[nate80]

Buy some of them lens covers if suitable for your less from flytron or wherever you can find them.theh certainly will make a difference as they make the light explode in a given angle making them more visable.

Thanks.    The LED';s I bought are really great quality and come pre fitted with 120 degree lenses. They also come installed on solid aluminium heat sinks which work really well.