Help with wiring up LED strips

Other Hardware General Electronics
1

Hello all,
I am a cosplayer using Arduino for the first time, rigging up LED strips to make a "flaming" sword. I have the LED strips soldered and wired in parallel (so both sides of the blade light up) and everything tentatively works on a breadboard. I am trying to build the circuit to be as compact as possible to fit inside a hollow sword grip I can design and 3D print later. I have a few more components I need to add, and that's where I could use some help:

I plan on using a 9V battery to power the sword, with an on/off switch built into the grip. I have capacitors and resistors, but where do I add them in the circuit, and what values of each should I use?

Additional info: Each LED strip (WS2812B) has 43 individual LEDs, so 86 in total, wired in parallel. The code is on an Arduino Nano.

Thank y'all so much!

2

I have capacitors and resistors, but where do I add them in the circuit, and what values of each should I use?

I don't have a schematic of your circuit so I don't know how I am supposed to answer that.
Common sense says a circuit should have some filter caps . In your case, with a 0.1A load, probably 470uF.

I can't comment on your leds because you didn't post a link to the vendor where you bought them so
I have no information on them except the type.
Post a schematic and a vendor link.(and/or datasheet)
If you can't find a link that gives the load current per light string then you will have to measure it with a
DMM.

There are many different products that use the ws2812 so what you have told is essentially nothing.

3

Here's the link to the LEDs:

I got my circuit to work with a 9V battery inline with an on/off switch and a 100uF capacitor, is the resistor necessary if it's working without one?

4

Number of Neopixel LEDs? “86 in total”

For 5v 86 X .06A = ~5 Amps

5

Two strips of 43 LEDs each.

6

The Nano uses a 78M05 regulator that has a typical dropout voltage of 2V.

This is the discharge curve for Energizer 9V battery:
energizer9V.jpg
You'll be lucky to get 2 hours with a 100mA load.

energizer9V.jpg

7

If all your LEDs are turned on, you will need 5 Amps.

A 12V car battery might work; you should be able to strap the battery on your back.

8

dl324:
You'll be lucky to get 2 hours with a 100mA load.

That's not a big deal, it just has to light up and look cool for the 30 seconds I'm on stage during the costume contest, while posing for pictures, and pre-judging. I can swap out batteries to keep them fresh.

9

You'll be lucky to get 2 hours with a 100mA load.

It's worse than that:

Each led dissipates 0.24W P = I*E =>I =P/E = 0.24W/5V= 0.0480A per led

Total Load current = 0.048A *86 = 4.1280A

.048*86

ans = 4.1280A

MATLAB

Ah =0.500;
Ileds = 0.048;
N=86;
Iload =Ileds*N;
T = Ah/Iload
minutes = T*60
>>T = 0.1211
minutes = 7.2674

According to my calculations , a 9V battery will give you about 7 minutes with 86 leds.

I got my circuit to work with a 9V battery inline with an on/off switch and a 100uF capacitor, is the resistor necessary if it's working without one?

Really ?
Post a photo of the 86 leds running off one 9V battery.
Time it to see how long it lasts.

I have the LED strips soldered and wired in parallel (so both sides of the blade light up) and everything tentatively works on a breadboard.

I plan on using a 9V battery

So if that's a plan, then what you are saying is that you haven't tested it with a 9V battery yet , right ?

A 12V car battery might work; you should be able to strap the battery on your back.

funny Larry :grin:

10

I measured 800 mA at peak brightness, but the flame code flickers between 200 and 800 mA and not all the LEDs are always on as the "flame" flickers up the length of the strip, so I figure that should extend the life a little more.

So, I don't need to add a resistor?

11

So, I don't need to add a resistor?

Welcome to the 21st Century.

The leds are PWM controlled.
The brightness (and hence current draw) are a function of the PWM pulse width.
If you are already using the code you should already know this.

Look for a parameter called Brightness

 FastLED.setBrightness(brightness);

I measured 800 mA at peak brightness, but the flame code flickers between 200 and 800 mA and not all the LEDs are always on as the "flame" flickers up the length of the strip,

Because the leds are flickering, the load current maximum is probably 800mA.
So your operating at approx 20% average duty cycle , which puts your 9V battery life at about 36 minutes.

12

Recommended wiring.

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13

Here's a diagram of the schematic. It works via breadboard, I just have yet to connect the parts directly together. FYI, I am a biologist in my day job and completely self-taught on everything from the coding to the circuitry, so I really appreciate everyone's patience.

14

Guaranteed you will destroy your Arduino like that.

Get a USB 5v battery pack.

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15

I'm trying to learn more--can you tell me why it would destroy the Arduino with the current setup?

I tested it before on a phone charger bank before and the problem was it would work at first but then shut off automatically within a minute, and I'd have to disconnect and reattach the USB cord to turn it on again, which isn't easily done when in full costume. Is there a different model that will continue to deliver power when devices other than phones are attached?

16

You cannot power large loads from the 5v pin on the Arduino.

You need to use a limiting resistor on each input on your strips, see previous image offered you.

You could power the Arduino and strips with a 5v USB battery (as shown).

17

Why are you running the circuit without the 86 0.1uF capacitors ?

18

raschemmel:
Why are you running the circuit without the 86 0.1uF capacitors ?

Because I am a complete electronics newb that has no idea what you even said or how I would even go about attaching those to an LED strip.

19

The link you posted was for individual leds , sold from a reel, not a strip.
If you MADE the strip it was your duty to LOOK at that data sheet (that YOU posted) and ask about the caps from +5V to GND at every led. The caps must be wired DIRECTLY to the power (5V) and GND pins of EACH AND EVERY ONE OF THE EIGHTY- SIX LEDS.
If you haven't done that, you need to do that NOW.

20

Connect ‘Out1’ to Arduino 5v pin.

Even better, plug an A/B cable into the USB jack on the Arduino.

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Connect ‘Out2’ to LED strips, see image in Post #11.

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When the Arduino is connected to the PC, do not connect the Arduino to USB Battery pack.