Decoration project with LED's for a special event in May 2016

[raidengl]

So I've already posted this on another forum but I just thought I'd post it here to get more opinions and help.

So a little about my experience level. I'm good with power tools and my hands especially woodworking. I took an electronics class in high school from a really good teacher back in 93/94. He taught us basic electronic circuit design, resistors, capacitors, timers, bread boards and the like. The same teacher also taught us computer programming, in basic mind you and the earliest versions of C and C+ on Windows 95 and 3.1. I haven't done any programming or circuit design in years though. I went ahead and did my due diligence before asking my question or I'm hoping I have. I've read a bunch of the online text books on this website. I've read countless post on here and other forums and websites about LEDs. I've watched several videos and read through an Instructable on making a flashing led display.

What I'd like to do is find a light weight spherical substrate no bigger then a basketball that would be hung from the ceiling of the event venue. The substrate would be either mat black or be able to be painted mat black. This substrate needs to be able to be cut in half or separated in half then put back together. That way all the wiring and circuitry can be placed inside. I had thought of shaping chicken wire around say a ball and then covering it in a non fuzzy heavy duty mat black fabric. I'd then punch tiny holes in the lower 2/3rds of each sphere at random. Each hole would be filled with the smallest possible white LEDs I can buy. I would also like to put as many LEDs on each sphere as possible but not a solid blanket mind you. Ideally each sphere would be battery powered so that I didn't have tons of power cords sprouting out the tops of each sphere traveling across the ceiling to a power strip. Each sphere would also have some sort of simple on off switch after the battery pack. Once the switch is flipped I would like the LEDs to slowly twinkle randomly not blink at a rapid pace. Having a simple way to adjust the speed of the blink would be nice. I could also adjust components in the circuit on a bread board test till I get the effect I want then build the permanent circuit. But if using a POT that I can just turn and the blink rate speeds up and slows down is doable that would be nice.

I already realize that simply buying white twinkling LED Christmas light strands and stuffing them in to the spheres would probably be the cheapest and easiest way to pull this off. The downside being that then I have the power cord issue. Though most LED Christmas light strands can be daisy chained nearly as long as your imagination can go. The daisy chaining would help with the visual of all the wires sprouting from the tops of the spheres but it's not perfect. And if I want to space the spheres far apart I run in to the issue that the distance from the plug to the first LED tends to not be very long. The venue hasn't been picked yet so I also don't know what kind of access to outlets the place will have. I looked on Amazon at battery powered LED light strands but not very many of them have a twinkling effect and if they do there are no videos of what it looks like. The other downside would be that if I use the light strands I won't have the satisfaction of having built the circuit myself and seeing it work the way I wanted. I'm sure you all can understand the satisfaction aspect.

One reply to a different post on the other forum I've posted this on said to wire LED's in parallel not series and to do one LED per parallel not many so they would all light up properly. Another post from 2008 that had a long well written multi chapter article in it had a few good pointers. the article said to run LED's in series. With the amount of LED's I want to use per sphere that worries me that they won't light up at all without a large power source. I haven't picked a set number of LED's per sphere yet. What I'd like to know is what everyone thinks the advantages and disadvantages of a bunch of LED's in series vs parallel are.

The article said that due to the varying nature of LED's even in the same batch run means you should include a voltage regulator circuit in your designs especially on a 9V battery (battery size hasn't been chosen yet). This will help insure that all the LED's come on with the same brightness no matter how much the battery fluctuates. I however wouldn't mind if some of the LED's came on at different brightness's due to their natural variability. I think it would add to the overall effect. Maybe even buying white LED's from different manufacturers to emphasize that variability on purpose. I'd love to hear everyone's thoughts on this but if there bright enough and small enough you might not notice the difference from one manufacturer to the next. I'm also now thinking that if there where a few different sizes of LED but again not very large it might add to the overall effect. I've seen people do projects with LEDs pre made to blink. The one video I watched had the LED's blinking way to quickly for what I want. I haven't looked to see if they sell blinking LED's in different blink rates. I'm curious what the advantages and disadvantages would be of pre blinking LED's.

I've read many a(n) post / article that says that 555's can be used very effectively to cause LED's to blink randomly especially if you chain multiples of them together in the same circuit. I've also read quite a few articles that say that an arduino can be used very effectively to make an LED chain or matrix blink randomly. My worry with the arduino is that it requires programming and it's been so long since I've done any programming. If I read or watched the right tutorial I figure I could probably learn how to write the needed program. Or if need be I have a brother who knows programming. What would the advantages and disadvantages of each approach be? Would one allow me to run more LED's per sphere then another. If say I'm running 20 or 30 LED's per sphere would I need a bunch of 555's to get them all flickering VS 1 arduino or vice versa? Would one require a bigger battery supply then the other. Or is there a better IC or group of IC's that would do what I'm trying to do?

Thanks in advance for any and all help in this.

 

[raidengl]

I've found these which I'll probably use to paint black and mount the LED's to.
https://www.superiorlighting.com/8_I...in_Lip_Opening_White_Acryl_p/02024wa-08wl.htm

I've also learned from the other forum that I should buy diffused LED's instead of clear LED's because they will look better.

 

[ClydeCrashKop]

Arduinos are way too easy and have lots of sample code online. Do a Google search for Arduino random LED. You may find code that will work for you as is, or that is easily modified to do what you want.

 

[raidengl]

So do you feel that the Arduinos will be easier then the 555's or some version there of?

Also I just found these
https://www.justartifacts.net/10quot-black-chinese-japanese-paper-lante10.html
at 1$ a piece you can't really go wrong but I'd be worried about the thin nature of the sidewall and the LED's staying in place without it tearing.

 

[ClydeCrashKop]

The Arduino Uno has 20 I/O pins. Some digital, some do Pulse width modulation and some are analog. Most can light 1 LED with just a resistor in series.

Below is all the code it takes to flash 1 LED

Example
intledPin=13; // LED connected to digital pin 13
voidsetup()
{
pinMode(ledPin,OUTPUT); // sets the digital pin as output
}
voidloop()
{
digitalWrite(ledPin,HIGH);// sets the LED on
delay(1000); // waits for a second
digitalWrite(ledPin,LOW); // sets the LED off
delay(1000); // waits for a second
}

 

[raidengl]

Thanks. I could even use the Arduino mega to increase the number of LED's per sphere.
So if I use the Arduino or even the Mega and say a 12v power supply how many LED's could I safely run in parallel off of each output?

 

[ClydeCrashKop]

By sourcing current, the Arduino I/O pin acts as source for +5 volts,
providing a high-side positive supply of current. On the other hand, by sinking current, the Arduino I/O
pin acts like a connection to ground, providing a low-side or negative current.
While each pin can provide about 40 milliamps of current, this is just about enough juice for one or
two LEDs to work on each pin safely. Drawing more than 40 milliamps or exceeding +5v on any pin may
either damage the microcontroller or the connected device. To safeguard against this happening, it is
generally a good idea to connect output pins to other devices using one of two components, the first of
which is a current limiting resistor used to drop or limit the current needed by the device. Playing it
safe, a 1 kilohm resistor is a common value for current limiting for general applications, although we can
get away with less resistance, as with our earlier LED schematics where we used a 220 ohm resistor to get
more brightness out of the LED without damaging anything. Alternatively, we could use transistors or
other switching components to switch larger current loads, like motors, solenoids, or strings of LEDs
that exceed the maximum 40 milliamps of current and/or operate at voltages greater than +5v.

There is also a maximum current output for the entire chip. ( You couldn't turn all outputs on at 40 milliamps.)

IRL520 MOSFET logic level transistors will ground 10 amps at 100 volts.

 

[ClydeCrashKop]

These are both Arduino, with open source code I think.

https://hackaday.com/2012/09/11/disco-planet-a-massive-rgbw-led-array-in-a-6-globe/

 

[raidengl]

Thanks Clyde that helps. In theory since I want the LED's to blink randomly at any given moment they won't all be on at the same time. Thus I won't have to worry about overloading the chip. Hence how I'm thinking many of these animated LED displays I've seen in YouTube videos that are controlled by an Arduino get away with that many LED's connected to it.

 

[raidengl]

The disco ball looks cool but I just want white LED's and much smaller LED's then that. Plus the flash rate of the LED's is way too fast. But the flash rate is all in the programming you upload to the Arduino.

 

[analog1]

You may buy strings of auto 12v leds as many of 600 on a 5 meter string. You may buy dimmers and RF controllers to do all kinds of fancy dancing with a push of a 2x3" controller. You may add and subtract to these set ups to your heart content.

 

[raidengl]

Found these with a quick search.
http://lighthouseleds.com/3mm-diffused-flat-top-led-white-ultra-bright.html
and these
**broken link removed**

Not knowing what the venue looks like (hopefully soon) I don't know what kind of overhead space I'll have to work with. But for right now I'm thinking maybe 15 spheres with 20 - 30 LED's per. I'll probably make one with 20 LED's in it then determine if I like the look and if not increase the amount till I like it. In a YouTube video with a flashing LED decoration the man used adhesive copper tape on the back side of a sheet of foam core. He then soldered all his connections to those. With the plastic globes I could easily run the copper tape along the inside of the globe and attach the wires to that. Or possible some kind of a push or crimp connection between the LED leads and the wires running from the Arduino circuit.

 

[raidengl]

This guy uses the TLC5940 in his video and it's a very thorough video and explanation of the chip and how he uses it. Some of his explanations do get a bit technical so if you haven't done programming in a really long time then your brain might get a bit fried like mine done. Now he uses RGB LED's which require two pins per LED. I'm just using white so I only need one pin and it has 16 outputs. You can also daisy chain them very easily for 32 outputs. Thus 30 LED's per globe easy. It has a current limiting pin that sets the whole chip resistance via what ever resistor you put on it. Thus none of the LED's need resistors on them. The programming is rather complex though. Hopefully I could find a free downloadable premade program I can customize to do what I want.

 

[raidengl]

So I've decided to use the Arduino. I'm just trying to decide whether or not to use the UNO or the Mega. The UNO is obviously cheaper per board and if I do say 15 globes that could really help keep my costs down.

If I use the UNO I can wire up a 6 x 6 matrix and get 36 LED's per sphere. Then I could put in three random number generators, one for the columns and one for the rows. The first two numbers would determine which LED gets turned on. Then I would use the third to determine how long the LED stays on and maybe a 4th to create a random amount of pause before moving on to the next LED. I could also create a conditional that if the LED chosen is connected to a PWM pin then do a random fade in and out instead of blink.

If I use the Mega I could hook up to 53 LED's to each pin individually instead of a matrix. Not sure what the advantages and disadvantages of each design would be. Anyone have thoughts on this.