I have a bunch of rolls of copper tape and I would like to use it on part of my lighting array. It measures 3mm wide x .15mm thick. If I have it right that is the same as 34 gauge wire. Yes/no?
Also, I want to be sure what gauge wire I should use for this array?
Solution 0: 4 x 7 array uses 28 LEDs exactly
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
34 gauge wire is 0.16mm - about the same as the thickness of your copper tape. Divide the diameter of the wire into the width of your tape and that equals 18.75. So, basically, your tape is equivalent to almost 19 pieces 34 gauge wire bundled together. That would make your tape approximately the equivalent of 22 gauge wire. That is more than adequate for what you have drawn.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Thanks, Mark.
What is the thinnest wire I can use on the array? Can I use this?
http://www.ngineering.com/accessories.htm
That'll still work fine.
Remember per the message below, those resistors are too small. You want bigger - use the wizard again but don't put the maximum LED current of 20ma in the LED current box, you want to use half that or less. And that might STILL be too bright - you might want to try it. One string of 4 LEDs is the same as any other, so you only need to hook up one set of 4 to test it, all else remains the same.
I would use something larger than the magnet wire to collect all 7 strings together - the wire that goes from the power supply to the point where each of the 7 strings ties together. The #38 will be fine for each LED in the groups of 4.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thanks, Randy.
I have 1/4w 4.7ohm resistors on hand. If I plug in 7ma on the diode forward, it says to use my
4.7ohm R. This is good?
For what supply voltage? 4.7 ohm is VERY low, almost a wire.
Or did you leave out the K? 4.7k I'm reversing it to see what supply voltage and what voltage drop you used for the LEDs and none of it is making sense. 12 volts into a 3.1 volt LED, 4.7k is like 2ma.
A clue the value doesn;t make sense - if you are talking the same LED string 4 of them in series, with that same 15V power supply, for LESS current, the resistor has to be LARGER, if the one for 20ma was 180 ohms, for 7ma it needs to be BIGGER, not smaller.
Oh - did you put .07 amps? 7ma is .007. Bond, James Bond.
Whoops, Package says R1/4 4k7-25
OK so if you use that 15 volt power supply and just ONE LED, that'll be about 2.5ma. The LED will light. What era is your roundhouse supposed to be? For those little surface mount LEDs, 2.5ma may be enough.
Early 1900s. I want lots of lights but quite dull.
What gauge would you suggest for the collector wire? I will use the #38 for the strand with the 4 lights.
That #30 they have listed right below it should be good, not too big to hide, but plenty big enough for the total current of the 28 LEDs.
So try one with the 4.7K resistor and see if it is bright enough. I suspect it will be, for an early 1900's era.
Okay thanks, So just to be sure, what resistor do I use if I only want to use 1 resistor per 4 lights and have it dull?
Plugging it back in your wizard, it returns 390 ohms, for arranging the LEDs as 4 in series, and 7 groups of those in parallel, with a 15V power supply.
Oh wait, I put 7ma in for that. 1.2K for 2.5ma. If it's slightly too dim, try the old standby 1K. That jumps it to a whopping 2.6ma But you can see a range there, of resistors to try, which will not put anythign in danger of blowing up. 7ma is 3090 ohm, 2.5ma is 1.2K - so anythign in between thouse two, closer to 390 ohms will be brighter, but if you don't go smaller than that there's no chance of it all blowing up on you because 7ma is well within the ratings of the LEDs. Somewhere in there should generate a pleasing glow for the period.
Thanks Randy.
What do I use these things for. Can I turn the brightness up and down with them?
https://www.amazon.com/Control-adjustable-regulator-Step-down-Regulator/dp/B01ARR8NNG
No, those just adjust the voltage. LEDs are current devices, so all that will happen with one of those voltage regulator modules is that over a very small range (they're not boost converters so they can put out no more than the input voltage), there will be pretty much no percepitble change of the LED brightness and then the output will be below the voltage required for the LEDs to even work.
For something like this project, your best bet is to experiment at the workbench a little until you get a light level you like by changing the resistors around, and once you find the one that works best for you, build up the full array. A tool that can help is a resistor substitution box - the one I have can select any value from 1 ohm to like 11M ohm. You do have to be careful that you don;t select a value below the lowest that will keep the current to a safe level for the LEDs, but if you don;t have a bunch of resistors of different values it's a good way to test something like this. Not terribly expensive. Just keep in mind, resistors come in set values, based on tolerances. You can't get any old value you want, so when using something like a substitution box, you have to pick the nearest standard value to what result you get. For example, 470 ohms is a standard value, 480 ohms is not. If you have an assortment of resistors in the range calculated, wire it up on a breadboard or with clip leads so you can swap in different resistors to see how it looks.
Thanks, Randy, I bet my Father in-law has one of those boxes. He is too old to help me with these questions, however everytime I ask to borrow a piece of equipment, he just gives it to me.