Copper tape?

[Timtreo]

Hi guys, can anyone give me a link of a place in the US to get that copper tape for the DIY night blades? I read the sticky thread and don't quite get how it works. Is it + on 1 side and - on the other. There is a bunch of different kinds on ebay - shielded, single conductive, for stained glass, ect... I read Kavics thread a few down but they are sold out of that silver tape he posted a link to.
Also what size (mm) surface mount leds would be good for 325mm blades?
Thanks for any help. Tim

[kavic5150]

Did someone say kavic?

Regular copper tape will suffice but it tends to tarnish after a while. And conductive adhesive is not necessary for what we do. Look for the narrowest tape possible so there is less cutting lengthwise involved.

I think my ebay friend Robinann was just out of that particular item, heres a few items of hers:

9 feet:
http://www.ebay.com/itm/9-feet-1-2-Inch-SILVER-BOTH-SIDES-Copper-Foil-Tape-/350443488182?pt=LH_DefaultDomain_0&hash=item51980f 43b6

108 feet:
http://www.ebay.com/itm/1-4-WIDE-Silvered-Copper-Foil-Tape-Silver-Both-Sides-/260424625005?pt=LH_DefaultDomain_0&hash=item3ca284 6b6d

I think if you ask her, she will sell you half or a quarter of that 1/4" inch roll. That way you would only need to cut it in half lengthwise.

[TheBum]

Check the local craft stores. If they have supplies for stained glass work, they may have copper tape. That's where I got mine. It was a little too wide, so I just split it lengthwise.

[Heli-opolis]

Another source is hobby shops that cater to doll houses as it is often used to electrify the more detailed ones.

I didn't build one for me, it was for a girl friend's niece! Honestly!

[sewerfly]

Originally Posted by Heli-opolis

Another source is hobby shops that cater to doll houses as it is often used to electrify the more detailed ones.

I didn't build one for me, it was for a girl friend's niece! Honestly!

So does your friends doll house happen to have a Heli pad on the roof hmm?

[Timtreo]

Hey thanks guys, I ordered some from robinann . I still don't get it though, is it + on one side - on the other. From what I can tell from the pictures it looks like the surface mount leds are just soldered on top of the strip? How is the polarity shielded? What size leds are good for 450 blades? Thanks again. Tim

[TheBum]

Originally Posted by Timtreo

Hey thanks guys, I ordered some from robinann . I still don't get it though, is it + on one side - on the other. From what I can tell from the pictures it looks like the surface mount leds are just soldered on top of the strip? How is the polarity shielded? What size leds are good for 450 blades? Thanks again. Tim

It just acts as a wire. So, you'll need two strips to complete the circuit: one for the positive pole and one for the negative pole. Typically, you run two rails, one the length of the blade on the top and the other the length of the blade on the bottom. You then run shorter strips from the rails to the components as well as a strip between each LED and its associated resistor, preferably wrapping across the leading edge of the blade. You will also likely need to put some solder across the joint where one strip overlaps another because the adhesive is rarely conductive.

[Timtreo]

Ok thanks Bum, any thoughts on what is a good size surface mount led for 450 blades?

[TheBum]

The 0805 size is good for all blade sizes. I got the ones for my 430mm blades from here:

http://www.niktronixonline.com/0805_SMD_s/78.htm

Make sure you have a pair of pin-point tweezers though because they are really tiny. Here's the technique I used to install the LEDs:

1. Run a single strip between the rails where you want the LED.
2. Cut a tiny gap in the foil where the LED goes and, if needed (all colors except possibly blue), a gap for the resistor.
3. Solder the resistor and LED using the following method:
   1. Melt a very small solder ball on each foil trace at the gap (it doesn't take much).
   2. Re-melt one ball and while holding the soldering iron there, put the component in place with the tweezers with the correct end in contact with the solder.
   3. Re-melt the other ball and while holding the soldering iron there, press the component down into the solder with the side of the tweezers (not the points).

[Timtreo]

Hey thanks again Bum, I'll order some today. Hopefully when I have everything in hand I'll understand how it all goes together better. Thanks again for all the help.

[TheBum]

Originally Posted by Timtreo

Hey thanks again Bum, I'll order some today. Hopefully when I have everything in hand I'll understand how it all goes together better. Thanks again for all the help.

Note that I edited my post above with a more complete process. Make sure you check continuity to make sure you don't get a short between positive and negative through the CF of the blade. The gel coat on most blades will protect you, but it can melt if you get the solder joints too hot.

[Timtreo]

Woops I guess I jumped the gun on my led order. I thought red was the only color you needed a resister for? I can see though if they are that tiny resistors would be necessary. They have a pretty good resistor calculator on that site. I'll try to figure out which resistors I need. I ordered yellow, green and purple and plan on using 1S 120 mAh batteries I have. Thanks again, Tim

[Timtreo]

Just a thought but I have some 100 Ohm 1/2 watt resistors. Do you think I could just put one (or more, I'll try to figure out the correct resistance needed) resistor coming off the + battery lead instead of soldering a bunch of tiny resistors by the leds?

[TheBum]

Originally Posted by Timtreo

Just a thought but I have some 100 Ohm 1/2 watt resistors. Do you think I could just put one (or more, I'll try to figure out the correct resistance needed) resistor coming off the + battery lead instead of soldering a bunch of tiny resistors by the leds?

The problem with that is the voltage drop across each color is going to be different. You'd likely end up lighting up the one with the lowest drop and none of the others. I used one resistor per LED except for the two red ones I put on the top and bottom of the blade at the tip, in which case I parallel-connected the LEDs (which keeps the voltage drop equivalent to that of a single LED but doubles the current) and had a single resistor feeding both.

[Timtreo]

Gottcha, thanks again Bum for your time explaining all this to me.

[flyinfool]

Originally Posted by Timtreo

Woops I guess I jumped the gun on my led order. I thought red was the only color you needed a resister for? I can see though if they are that tiny resistors would be necessary. They have a pretty good resistor calculator on that site. I'll try to figure out which resistors I need. I ordered yellow, green and purple and plan on using 1S 120 mAh batteries I have. Thanks again, Tim

When you are using the resistor calculators for your 1S LiPo, use 4.2 volts as the battery voltage. 4.2V is what a fully charged LiPo will be. You do not want to cook the LEDs right away....

[kavic5150]

Originally Posted by flyinfool

When you are using the resistor calculators for your 1S LiPo, use 4.2 volts as the battery voltage. 4.2V is what a fully charged LiPo will be. You do not want to cook the LEDs right away....

I disagree. The LED calculator always returns resistor values that run the LEDs at about 80% brightness. It says 56 ohm and I use 33 for white and green. It says 27 and I use 8 for blue. Havent popped an led yet.

On a night blade with at least 3 or 4 leds the voltage drops to 3.9 very fast.

With the higher value resistors those 3s led strips outshined my blades.

[flyinfool]

It is not just the extra heat in the LED that may be shortening there life.
I have 7 LEDs on each blade, They are rated at 20mA each. That should be a total draw of 140mA on the pack. When I used the resistor that the calculator said for 3.7V the 7 LEDs were pulling 525mA measured. Once I put in the LEDs for 4.2V I was getting the correct 140mA for the full duration of the battery. I could not tell the difference in brightness with just my eyes, I still had to crank up the lighting on the heli so the blades did not wash it out.
The battery I use is a 200mAh LiPo. it is only rated for 2 C discharge. With the lower resistor values I was exceeding the max output rating of the LiPo. Some people are using even smaller cells. Measure you current to be sure you are not risking the LiPo.

I never checked to see if different online calculators gave different results. They shouldn't, but we'll never know till someone gets ambitious enough to check.

[kavic5150]

Didnt mean to start a debate on the subject. When I tried the recommended 33ohm resistors on the 1208 size blue smd it was dimmer than the other 2. I replaced it with an 8ohm and it was a similar brightness as the other 2 (green and white).

Maybe I got the wrong specs for the blue leds.

[Heli-opolis]

Originally Posted by kavic5150

Maybe I got the wrong specs for the blue leds.

Doubtful. The specs are not intended to show values to be used to achieve equal brightness.

Usually one will have to over-drive blue LEDs to get them anywhere close to the same brightness as other colored LEDs, especially red or the converse, run other color LEDs at less then their maximum ratings to match a blue LED running full tilt.

I rarely use blue LEDs mainly because of that and prefer to stick with red, yellow, green and white.