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 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 know there are some battery powered light strands on the market but not sure if any of them twinkle or do it in a slow enough fashion for my tastes(I just haven't looked yet). I work in retail and we have an LED light strand on clearance with a very tiny LED that is the perfect size but it doesn't twinkle. We do sell white LED Christmas lights in season. My problem with them is the LED light is much bigger then I want. 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 asspect. I have till May 2016 to finish this so plenty of time if I start now.

One reply to a post on here said to wire the 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'd like to know 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. 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 naturally 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 also add to the overall effect. I've also seen people do projects with LEDs pre made to blink. The one video I watched the LED's blinked 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.

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.

 

That's a thorough but lengthy conceptual problem description but it leaves too many parameters inadequately defined to offer much specific help.

You need to define the visual experience you intend the viewer to have and under what conditions. Some considerations: viewing distance and angle(s); ambient lighting; brightness, size and density (total number) of points of light; run time requirement; average duty cycle; etc. Some of these things you will already know, some you can readily ascertain and others may require some experimentation with a partial prototype such as a small curved panel of LEDs.

The terms "blink", "twinkle" and "shimmer" connote different visual experiences that are not well-defined but in general, blinking usually suggests the randomized on-off modulation of a light source at full brightness with 50% or lower on-time duty cycle; twinkling is characterized similarly but with a much higher duty cycle (short off times) and shimmer is similar to twinkle but modulated at higher frequency and often with multiple circuits interleaved within the same visual display.

To give you some idea how some simple control strategies and experimentation can have good results, I'll describe some things I've done. I created a simulated star field display using strings of small incandescent lamps positioned behind a transparent blue filter with approximately 90% of the lamps on solid while the remaining lamps were twinkled in two or three groups at different frequencies. For one stage production I created a classic eight-pointed "star of Bethlehem" using 721 miniature bulbs where 50% were on solid while the interleaved remainder were shimmered. This resulted in a mesmerizing twinkling effect. In another display using small LEDs packed closely together, I achieved an overall twinkling effect by interleaving eight groups of LEDs controlled by two 556 timers (4 timers, 2 states each).

 

Thanks for your response. The idea is to have as many of the spheres as possible depending on how hard or easy and how expensive they are to create, hung from the ceiling. They would be hung at a height just high enough that people can't reach them and you would need a ladder to get them down or put them up. As for viewing angle the idea is to have however many I build hung randomly across the whole ceiling of the event.

Never having built these before I could end up putting say 20 LED's in the spheres and think wow that's way too many or I need twice as much. It's hard to visualize the density without mocking one up. I'd like the blinking of the lights to be a slow random blinking rather then a fast strobe light type effect or shimmering water type effect. Meaning that each LED blinks independently of the next as best as possible. I basically want the small LED points to look more like stars in the sky hence doing LEDs of different sizes.

I had even thought of sewing together fabric in to one large sheet that would stretch across the ceiling of the room and the LED's would be spread out randomly across the whole sheet. But I kind of want the upper ceiling structures of what ever venue is chosen to be seen, hence the spheres. Also the venue will more then likely have it's own room lighting which will be used as the utilitarian see what your doing lighting. Hence why the sheet stretched across the room was nixed so it doesn't block any of the preexisting lighting in the room. The spheres will just be effect lighting so don't need to be super bright as a group. They will only need to run for 5 or 6 hours then be taken down. That's why I'd like them to be battery operated if possible and turn on and forget.

 

You mention Christmas tree lights, and that's exactly what jumped to my mind.

I have 3 different sets, 50, 100 and 200 (I think) that are battery operated and have a load of different effects, phase in and out, random flashing, or a twinkling effect etc, all built in to the battery pack. 2 of these sets have led covers (1 stars and 1 trees) that cover the leds, but easily pull off to leave a bare led.

It would be fairly easy to drill x number of holes and stick these leds through, and all wires and battery would be enclosed in the 'ball's.

I think this would be a very easy way of doing what you want (without the different size leds, but you could push some through the whole way, others not so much, and the functions of the lights would likely negate this need anyway through different on/off and intensity patterns). It'll definitely avoid any cable/power issues and meet your run time and enclosure requirements, whist staying cheap (think my dearest set was about £25 from a shop, not online), plus you can reclaim them for Christmas use and won't take an age to build each one

Like:
http://www.amazon.co.uk/Action-Christmas-Lights-Battery-Operated/dp/B00ET4UU0S

Cheers, Upex

 

I just finished a Firefly in a bottle project; 10 LED's flashing at random in a blue SKY vodka bottle. LED's white piranah 3V @ 30 mA. Could be 2 in series to give 20 LED's. Flash rate about 3/ sec. adjustable. 2 555's , 2017, 12 NPN's.
One member made a difused light source using 8 in plastic bowl as 1/2 sphere. Can also heat form styrene or ABS to form 1/2 spheres.

 

Thanks Upex I may end up going the Christmas light route in the end. But it would still be cool to be able to say I made the LED circuit myself.

 

I'll also have to see if they have something similar to that in the US side of Amazon instead of the UK version.

 

Sure you'll have something in one of your super stores, if we hold them in our short stores.

Try and build one, and have these as a fall back, especially if you want loads of leds (ie 100 per globe) and that presents a lot of work across 20 globes etc.

As an aside, I found a globe like container that would be perfect, except its clear plastic, but could be sprayed etc. a holder from lindor chocolates:

http://www.amazon.co.uk/Lindt-Lindor-Maxi-Ball-550/dp/B006IUY480
When that big wrapper comes off, it's inside, full of chocolates. The plastic case splits in half and has a small flat to stop it rolling about, but for you use, would make a great place for hanging point and also could stick the control box onto as well, so can turn on off even when all assembled.

Heck, thinking it through, if you literally stuff the lights in the see through globe, without needing to drill, that might work as it is, as when darker, wouldn't see the wires etc, but the light might reflect and shimmer and such and add more twinkle from within the globe itself. Just a thought.

Plus think of all the chocs you'd have!

Cheers, Upex

 

Sadly Upex it's not Dark Chocolate and you can't buy it in the US LOL. Oh well on with the search.

 

As for the work making these things this is an important event for me so I'm willing to put in the work. Even if I have to make the LED strands myself and build each circuit individually.

 

Fair play to you, and at least you got a good lead up with plenty of time to do it.

Let us know how you get on, with pics eh.

Thanks, Upex

 

For direct viewing and wide viewing angles, diffused LEDs look far better than water clear packages.

 

Thanks KJ6EAD.

 

I found these
http://www.superiorlighting.com/8_I...in_Lip_Opening_White_Acryl_p/02024wa-08wl.htm
I can drill two holes in the lip on the top and then put a wire loop from one hole to the next to hang it. I should be able to spray paint it mat black very easily.

 

It's difficult to work through an opening that small but you could insert standard 3mm or 5mm LEDs through drilled holes from the inside. If the hole sizes are precise, you get a good interference fit, otherwise some adhesive can be used.

 

Search paper lanterns. You can get them for $1 each for 10".

Another option is paper clips and clear solo cups. Drill a hole through a stack of 18 cup bottoms and put an LED or Christmas tree light bulb through each hole. Then paper clip/hot glue the cups together into a sphere. They are light weight and can be hung by the cord of the Christmas lights. About $2 each plus lights. Look great.





http://www.thriftyfun.com/Making-Sparkleball-Decorations.html

 

Thanks that looks very cool. Not exactly the look I was going for though.

 

I posted the same question on another forum and one persons opinion on there was that the Arduino would be easier to do then the 555. It also looks like if I use the Arduino mega I can increase the number of LED's per sphere.

 

Found these with a quick search.
http://lighthouseleds.com/3mm-diffused-flat-top-led-white-ultra-bright.html
and these
http://www.led-switch.com/1.8mm LED.htm

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

I'm thinking these would work well to connect the leads on the LED's to the Arduino board.
http://www.amazon.com/Jumper-Wires-...9&sr=1-3&keywords=female+to+male+jumper+wires

 

I just made a 6 in dia hemisphere from 3/16 clear thermo plastic. I had a 6 in glass globe. cut a 6.25 in hole in 1/2 in plywood & another 6.5 dia as a clamp. Clamped plastic between sheets, heated whole thing to 320 deg. F, 8 min. then pressed globe into plastic. Think I would use a router to cut off scrap. Might be worth a try?
My understanding is that Arduino requires an output pin for each LED, and may require drivers for 20 mA LED's.
If using Discrete IC's, 4017 = 10 LED's @ maybe 15 mA, or with 2 in series = 20 LED's, or cascaded 4017 for 17 LED's; Or similar 74AC138 3 line to 1 of 8 ($ .42 ), 2 ICs for 16 LED's & can direct drive LEDs up to 25 mA. Wanted 74AC154 4 line to one of 16, but do not believe it exicts.
Top hat LED looks good.