Nice LED/Resistor Calculator

Parallel and Serial modes, pretty simple to use.  Very nice!

http://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator

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SMD LED's Seem Quite Small...

 ... Until you get the bright idea to use SMD resistors to save weight! See the tiny white thing?  That's the LED.  And the little spec beside it, that's the resistor.  I had no idea they would be so small... it didn't occur to me that the ebay vendors would be photographing those things in such closeup.  I'm going to try to see if there's a larger size of SMD resistor.  Ideally I would be able to solder the resistor directly to the LED, forming one piece to mount.  BTW the white thing in the upper-left is the package of 50 resistors.

Here they are getting ready to be soldered.  It turns out that it's possible, but I didn't get any pictures of the soldering process, mainly because I wasn't optimistic enough to have a camera ready.  I'll follow up with some notes on how I did it and some pictures.

This is for adding some nav lights to the ladybird.  If there were some ready-made ones I think I would buy them without hesitation, but it's been educational learning how to deal with such tiny pieces.

Adding some LEDs to the ArctiBaby

 I put some LEDs onto the ArctiBaby, hoping to make orientation a bit more visible.  Here's the 2S connector for attaching to the battery. I put an 82 ohm on the wire, which split to 4 power wires to each of the LEDs.  I'm using 28 gauge servo wire.

 Here's my mockup to make sure I was getting the circuit right.  I put one resistor in series with four parallel LEDs.  I'm going to ask some gurus if that's the right thing to do, but it seems to be working.

 Here's how I attached the wiring.  I zip-tied the end of each wire (where the LEDs are) to the end of each arm, with the LEDs pointing out.  The front had two 5mm frosted amber LEDs, and the back had two 5mm clear reds.  I put some scotch magic tape over the reds to get some frosting effect. It didn't work very well.

 Here's the final result.  I'll give it a try tomorrow and see how the visibility is.  Right off the bat I can tell you that amber/red is a pretty poor color combination for orientation differentiation.

I was using my jumbo 500 random LEDs for $2 package.  About 90% of the LEDs are red, and most of the other 5mm LEDs were amber.  There were a few tiny (2mm?) green LEDs.  So that's how I picked the color scheme.  I've ordered some 5mm frosted blue LEDs; I'll replace one color or the other and see if that makes it better.

SMD LED Notes and Tester

 Here's some more information on SMD LEDs.  First, they are small. really really small.  And impossible to tell apart regarding the color.  To sort out the colors I received in a package, I put together this LED tester.  It's got two servo pins to pick up and power the LED, and a 120 ohm resistor so that it can be powered by a 1S lipo.  So far it's working well, and the tips don't touch when the tweezer is squeezed together.  Everything's assembled with shrink tube.  Be careful, because if the LED slips (as I learned by hard experience) it will shoot out of the grip of the pins and be long gone.

Here's the resistor values I'm using, based on the LED data card from the ebay vendor.  Two nice resistance calculators are here (with color codes) and here (with parallel and series calculations).

SMD LED Sizes

Here's an illustration of the various sizes of SMD LEDs.  They're pretty cheap on ebay.  0603 Soldering tutorial.  Several more on youtube.  I'm trying to figure out what size is best for the Ladybird.

Note: on the back side there's an arrow. The arrow points to the negative wire.



Dimensions:

• 0603. Footprint: 1.60 x 0.80 x 0.40mm.
• 0805. Footprint: 2.00 x 1.25 x 0.80mm.
• 1206. Footprint: 3.20 x 1.60 x 1.10mm.

This is the 1206 data from the ebay vendor:

My Farm Fresh Quad Helmet

Here's how I attached a vegetable container from the supermarket to act as the cover for the Arcticopter 4.  I used these standoffs:

Nylon 6/6 Male-Female Standoff 4-40
1/2" Body Length,
3/16" Male and Female Thread Lengths,
White (Pack of 100)
http://www.amazon.com/gp/product/B00...ms_ohs_product

Even though the vegetable container is very thin, the standoffs keep the surface taut.  If you tap on the top it will reverberate like a drum head.

I attached the standoffs to the frame, and colored the tops with a Sharpie to align the holes. I handheld a drill bit to cut the holes in the plastic.

 4/40 bolts attach the stack of standoffs to the frame.  This stack is 1.5 inches, but I think you could double that and still be reasonably stable.

One nice feature of the nylon threads is that they will break before anything else.  If you break the threads off of a standoff, it becomes a perfect candidate for being the top screw.

I put a piece of blue tape on the back to block off the green LED, which I found to be too bright in the evening.  I added a 3-LED strip plugged into the balance port which works pretty well: visible without being blinding.

Let There Be Light (Emitting Diodes)!

Here's how we attached LED lights to Arcticopter 1.

 LED strip lights are pretty amazing things.  They're thin, have LEDs mounted on flexible strips with which carry the current, and have sticky backing.  We bought four colors: red and green for left and right (as per standard aviation habit), white for front, and blue for the rear.  They come in 1 meter strips, and can be cut every 5 cm (every third LED) to make the length you need.



Here's the shopping list:

• - LED strips (non-waterproof): Red, Green, White, Blue
• - Brushed ESC
• - Connectors
• - Wago Connectors -- these are great for temporary wiring, since it can hold five wires together and the snaps allow wires to be added and removed individually.

There are two different kinds of light strips -- waterproof and non-waterproof.  For aeronautical purposes, get the non-waterproof, they are a lot lighter... 12 grams vs 36 grams per meter.  Unless of course, you're making an amphibious flying vehicle!

The current draw for four 1-meter strips is 0.1, 0.4, and 1.1 amps at 11.4 volts at min, half, and full power (unscientifically measured by my turning the knob on my servo tester -- more on hooking things up below).  I haven't measured with smaller strips, but I think the current draw will be smaller in proportion to the number of LEDs being driven.

Here are the two kinds of strips.  Note that every 5cm there's a "cut here" spot.  The waterproof strip has a nice scissors marking to leave no doubt.

On the far left of this photo, we can see there's a built-in resistor; we don't have to worry that we'll burn out the LEDs.  In the middle we see the cut line. On either side of the line, we see the solder pads.

Here are side views of each of the normal and waterproof strips.  You can see there's lots of plastic encasing the waterproof strip.  Both have 3M sticky backing.

Wiring the Strips -- First Try

Here's my first try at wiring the strips.  I used some JST-RCY connectors (with leads: male and female) that I had laying around. It works, but I think it can be better -- lighter, smaller connectors, and with less wire clutter.  See below for a second try.

The arms are about a foot long -- a 15-light, 25cm strip will fit perfectly.







I cut 2 each 25cm strips of the four colors: red, green, white, and blue.  Some of the strips had the original wires attached; Since we want all the strips to be consistent in the wire length, we'll desolder those.




Soldering the Strips

[placeholder for LHS pic] I'll add some pictures later of the soldering.  For now, I'll just note that I had some JST-RCY connectors attached to leads, and soldered those to the strips.  The small circles next to the cut lines are solder pads.

Strip your wires to about 2mm, tin them, tin the solder pads with a blob of solder, and then "mash" the tinned wire into the solder blob.  It will melt almost immediately and make a nice looking connection with your wire in the middle.  When you tin the solder pads, there will be a thin covering film that will evaporate off and expose the pad.  If you don't get a nice circular blob, try again.

If you're working with the waterproof strips, use an Exacto blade and push it straight down through the plastic.  You can then lift the plastic off of the strip.  Get as much of the plastic off as you can... you can melt through it with the soldering iron, but it's probably made of stuff you don't want to be inhaling a lot of.

Note that LEDs have polarity, and the strips do as well.  Before you desolder the supplied wires, note which sides are attached to the hot and neutral wires. After you solder each pair of wires, stick them onto a convenient 2S or 3S battery -- if the strip doesn't light up, you've got the wires backwards -- desolder them and try again.

Here's the power harness I wired up... Eight female (note discrepancy of terminology) JST-RCY leads for each of the strips, and a male JST lead to plug into the wired ESC output (or to a battery, if you're skipping the ESC).  It's heavy, and bulky when stuck into the frame, but it works.  I soldered a female JST-RCY onto the ESC output leads.



Here's everything connected together and attached to a 3S battery. You can use a 2S battery if you want it dimmer, but it seems most people like the brightness from the 3S.  I've got the ESC attached to a servo tester.  If you don't have one you can connect to a receiver and control with your transmitter, but you really should consider getting one -- it's cheap and saves you a lot of time at the workbench.



I used 8mm shrinkwrap to wrap the end of the strip.  It doesn't seal up tight on the wire end, but it does do a good job of strain relief.  If you know of a better way (funnel-shaped shrinkwrap?) please drop me a line!




Wiring the ESC

Wiring the ESC is pretty simple.  Put your favorite battery connector on the battery end.  If you don't have a favorite, the JST-RCY is small.  That's what I will be using.  On the other end, put whatever connector you've used to wire up your lighting harness.  For my first try, that was a JST-RCY.  For the second attempt, I'll try using a universal servo connector if the current isn't too much -- I don't think it will be.

Another option is powering the strips directly.  It will work (because of the built-in resistors), but may give you much brighter lights than you want.  This is especially important if it's dark, since they may clobber your night vision.  Perhaps this could be controlled with resistors?

Wiring the Strips -- Second Try

coming...

Attaching the LED strips

Attaching the strips was pretty straightforward.  I used blue tape to position everything temporarily to make sure everything fit.








I wrapped the inside wire for strain relief.  You can see the big clump of wires below, and why I want to rewire this.







Here's everything attached and turned on.  I'm hoping that it will be plenty bright for daytime use.  It's sure bright sitting on my dining room table!