DIY Night Blades Help

[TheDeltaFlight]

Ok, So here is what I will probably order (Unless you guys think otherwise)

1206 SMD Red Link
1206 SMD YellowLink
1206 SMD GreenLink
1206 SMD WhiteLink
1206 SMD BlueLink

So the Red and Yellow have a forward voltage of 1.8-2.2v and the Green, White, and Blue have a forward voltage of 3.0-3.2v. They all have a current of 20mA.

2x 1s 3.7v 150maH Lipo For Each Blade


So my question is what resistor(s) will I need. I will have 5 LED's per blade. Can I just use on resistor between the negative lead and the copper tape similar to the one in the video?

I will be wiring the blade like this:

How to make a set of night blades simply - Part 2 (9 min 20 sec)

I edited this post to include more/better information on what I wanted to do.

[dvdouden]

The ones referenced in that thread are 0603 or 0805 sized LED's.
Something like this:
http://www.ebay.com/itm/100-x-SMD-SM...item2a1af585bf

[kavic5150]

I like to use 1206 or 1210 smd leds. They are a bit bigger and thus easier to work with than the miniscule 0805 or 0603s. 1210s also appear brighter because they have a larger lens surface area.

Leds:

http://lighthouseleds.com/led-component-lighting/smd-leds-surface-mount-diodes.html

Or from here, but be sure to check the data sheets to see what the led footprint looks like. Sometimes they have several solder points making them difficult to solder to:

http://www.digikey.com/scripts/dksearch/dksus.dll?FV=fff40008%2Cfff801b9&vendor=0&mnonly=0 &newproducts=0&ptm=0&fid=0&quantity=0&PV69=3

I've tried a few UV leds from a couple of sources but they emit mostly in the non visible spectrum. If its purple leds you are after, the only place I know of that has them is hobbypartz.com. I just buy a strip, desolder individual leds and use the same resistor value that I would for a blue led.

http://www.hobbypartz.com/ledlights.html

Also I've never seen a yellow smd led. When they say amber, they really mean orange.

Micro switches:

http://www.digikey.com/product-detail/en/AYZ0103AGRLC/401-2014-1-ND/1640123

Pin connectors that can be used as both male and female charge connectors:

http://www.ebay.com/itm/3pcs-Strip-T...item5ae37cb826

Be sure to use plenty of CA, especially on the copper tape. The adhesive backing can come loose in flight. Also its good to stretch the copper tape a bit when applying longer pieces, then use a credit card or fingernail to get rid of any wrinkles. The tape does not need to be 1/4 inch wide. It can be cut lenthwise into 1/8th.

[kavic5150]

Copper tape with silver on both sides. Much less prone to tarnishing than plain copper tape:

http://www.ebay.com/itm/Copper-Foil-...item51ab81334b

[TheDeltaFlight]

Thanks guys! Just one last question. If I get the 1206 LEDs, and have 5 LEDs per blade, what resisters will I need. I will probably use a 1S 3.7v 150mAh 25C Li-Po for each blade. I just don't understand the online calculator.

Is 5 LED too much for the battery?

[dvdouden]

(input voltage - LED Forward voltage) / current = ohms
As an example
(4V - 3V) / 0.02 = 50 Ohm
1Cell lipo can be up to 4.2V when fully charged. LED voltage depends on the color and material of the LED, consult the datasheet or specs. Current is usually 20 milliamps (0.02 amps) per LED.

5 Leds will do fine for your battery. You'd have 0.1 amp draw and should get well over an hour on a single charge.

[TheDeltaFlight]

Originally Posted by dvdouden

(input voltage - LED Forward voltage) / current = ohms
As an example
(4V - 3V) / 0.02 = 50 Ohm
1Cell lipo can be up to 4.2V when fully charged. LED voltage depends on the color and material of the LED, consult the datasheet or specs. Current is usually 20 milliamps (0.02 amps) per LED.

5 Leds will do fine for your battery. You'd have 0.1 amp draw and should get well over an hour on a single charge.

Ok.

So the LED's I'm using have a forward voltage of 3.0v - 3.2v and a current of 20mA.

So if I use 5 LEDs, do I type a forward voltage of 3.2v and a forward current of 100 into the calculator? This tells me I will need a 1/4watt 10ohm resistor. Or do I multiply the voltage by 5 as well?


http://led.linear1.org/1led.wiz

[dvdouden]

If you put the LED's parallel you multiply the current with the amount of LED's, so you get 100mA (or 0.1A), you don't change the voltage. If you place them parallel then you have to make sure all LED's have the same forward voltage.
You only multiply the voltage if you place the LED's in series, but then you don't multiply the current

So in your case you need a single 10 ohm resistor. Or five 50 ohm resistors if you use one resistor per LED

So 5 times 50 ohm (1/8 watt will be enough)



or a single 10 ohm (1/4 watt)


Edit:
I just noticed I swapped the anode and cathode in these images... The legs of the LEDs should be swapped.

[TheDeltaFlight]

Thanks for all your help!

[kavic5150]

Since you are probably using different color leds, you will want a separate resistor for each different color.

Go ahead and use 4.1v for source voltage since you have 5 leds. That 150ma lipo will quickly drop from 4.2v under no load to 4.1 or even 4.0v under no load. From there it will drop voltage slowly.

What you want to look out for as the voltage gets low is the blue or purple leds. They will begin to fade first. Then the white ones begin to fade right after that, but your heli should be on the ground by then.

I use:

8 - 12 ohms for blue/purple 3.6 to 3.8v Vfd
28 - 33 ohms for white/green 3.1 to 3.3 Vfd
90 - 100 for amber(orange)/red 1.8 to 2.1 Vfd

Keep in mind that is the maximum brightness for discreet leds with 20ma forward current. I find the led resistor calculator returns values that run leds at 80%

[kavic5150]

One more thing before you start. Take a volt meter, set it to either the lowest ohms setting or the one that beeps when there is any amount of continuity.

If you are using carbon fiber blades, sometimes the trailing edges are conductive. Most blades have a clearcoat even on the surfaces that appear as unfinished CF.

Take a small piece of the name brand scotch tape with the red plaid packaging (or something similar). and cover any spots that the copper tape will cross.

Or see this thread which outlines an even more effective way of insulating bare CF:

https://www.helifreak.com/showthread.php?t=495423

[TheDeltaFlight]

I just updated my first post to address my main question.

[dvdouden]

You cannot place LED's with different forward voltages in parallel using one resistor. So you'll have to use at least two resistors. Just multiply the number of LED's with 0.02 to get the total current for that group of LED's and apply it to the formula I gave you earlier. Then hook them up per group using the second diagram I posted earlier.

So for example, 2 red/yellow: (4Vbat - 2Vled) / (2 * 0.02A) = 2 / 0.04A = 50 Ohm

[adam911]

nice and informative post a friend of mine is also working on it. I am sure that this post will help him.

[cbrkhan]

I tried to make my first set DIY night blades yesterday. Messed it up at soldering the resistors and LED's

What is the secret to holding down tiny resistors and LEDs and solder at the same time? Do you glue them in place first and then solder?

[JWeber]

I just made a set of blade this past weekend.

1 - Put minimal space between the copper strips
2 - Pre-tin the copper ends with a minimal amount solder
3 - Use tweezers to place the resistor or LED on the two tinned ends.
4 - I just use the tweezers to put some pressure on the resistor to hold it in place then reheat the solder to get it flowing. I also use the soldering iron to sort of push the solder toward the component.
5 - Once you've done both sides and tested your connections, let it cool and then a small drop of CA on the side of the resistor or LED to hold it in place. I wouldn't put it on top in case heat needs to be dissipated.

Don't heat the component too long. These little guys can't take heat for a long period of time.

Couple of other tips.

1 - If one LED is dimmer than the others that means that you have a bad solder joint on either the LED or resistor
2 - Make sure you get the polarity correct on the LED. It's a pain to unsolder both sides of the LED after it's attached.
3 - Test the LED before you use it. There can be bad ones in the pile. Not likely but possible.

[myxiplx]

Kapton tape, its worth its weight in gold, tape down the led and resistor and solder away. It's referenced in the tutorial sticky on this site, there's a great video series that walk you through everything.

[myxiplx]

Here you go, post 11 in this thread, its a really good set of videos
https://www.helifreak.com/showthread.php?t=176408

[cbrkhan]

Originally Posted by myxiplx

Here you go, post 11 in this thread, its a really good set of videos
https://www.helifreak.com/showthread.php?t=176408

Thanks, the tape trick worked for me.

It does take a little bit of practice... Burnt three LEDs before getting it right. I think I applied too much heat. Any one starting afresh, I would highly recommend ordering extra LEDs and resistors and practice on old/crashed but not broken blade before you work on the baked you are going to use