Arduino Forum

Using Arduino => LEDs and Multiplexing => Topic started by: suicidalacorn on Jan 15, 2013, 08:28 pm

Title: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 15, 2013, 08:28 pm
I am going to make a 5x5x5 LED cube. i was going to use the colomns of the LEDs for the anode and have the anode of each LED in the colomn connected. Then i was going to connect the cathode of each LED in a layer together and use it to control the cathode of each layer. that way i can turn on a certain layers cathode and a certain colomns anode and get a certain LED to light up. i will be using an arduino uno and as many transistors and shift registers as i need. i also have thought about using MOSFETs, but i think since each LED uses about 20ma, i will only ever have 100ma max going through a transistor at a time. i do believe a transistor can handle that. but my question is what transistors i should use to turn the anode and cathode on and off. i should be able to use some basic transistors due to the small amount of current that will be going through each one. but my main question is what i will do about power. i think im going to buy 2 5Volt 2Amp dc wall wart power supplies. that would be plenty of power to power everything, but the LEDs are only 3volts each. so i am either going to use resistors, or i am going to put some high current voltage regulators between the power supply and  the power to the transistors that turn on the LED anodes. i really dont want to have to wire a resistor to each LED, but if that is the best choice, i can do it. any help is appreciated. i do not know much when it comes to this stuff. i am trying to use this to learn and figured the challenge would be nice.
Title: Re: 5x5x5 LED cube help
Post by: fungus on Jan 15, 2013, 09:25 pm

I am going to make a 5x5x5 LED cube. i was going to use the colomns of the LEDs for the anode and have the anode of each LED in the colomn connected. Then i was going to connect the cathode of each LED in a layer together and use it to control the cathode of each layer. that way i can turn on a certain layers cathode and a certain colomns anode and get a certain LED to light up. i will be using an arduino uno and as many transistors and shift registers as i need. i also have thought about using MOSFETs, but i think since each LED uses about 20ma, i will only ever have 100ma max going through a transistor at a time. i do believe a transistor can handle that. but my question is what transistors i should use to turn the anode and cathode on and off. i should be able to use some basic transistors due to the small amount of current that will be going through each one. but my main question is what i will do about power. i think im going to buy 2 5Volt 2Amp dc wall wart power supplies. that would be plenty of power to power everything, but the LEDs are only 3volts each. so i am either going to use resistors, or i am going to put some high current voltage regulators between the power supply and  the power to the transistors that turn on the LED anodes. i really dont want to have to wire a resistor to each LED, but if that is the best choice, i can do it. any help is appreciated. i do not know much when it comes to this stuff. i am trying to use this to learn and figured the challenge would be nice.


Don't use resistors for LEDs, use a proper current regulating chip. This protects the LEDs and makes sure they all run at the perfect current.

Most cubes illuminate a whole layer at a time with the layers as anodes and the columns as cathodes ("common anode"). The reason is that LED switching devices prefer to be between the LED cathode and GND (even simple NPN transistors). You switch power to each layer in turn and put your switching devices in the base.

So...unless you've got a really good reason for doing otherwise, I'd use a tried-and-tested design. Common anode layout and something like four daisy-chained TLC5916 chips for switching and current regulating.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 15, 2013, 09:58 pm
well, i would much rather use the shift registers because of multiple reasons. i see what you are saying, and that makes perfect sense. but i really want to do it with shift registers. i know it will add more parts and wires, but i am willing to do that if i can use shift registers. thanks for the advice, though.
Title: Re: 5x5x5 LED cube help
Post by: fungus on Jan 15, 2013, 10:12 pm

well, i would much rather use the shift registers because of multiple reasons. i see what you are saying, and that makes perfect sense. but i really want to do it with shift registers. i know it will add more parts and wires, but i am willing to do that if i can use shift registers. thanks for the advice, though.


The TLC5916 is a shift register, it just happens to have current regulation built-in.

Whatever you do, don't use MOSFETs. They switch very slowly unless you add special circuitry (extra transistors) to switch them.

A good transistor for switching LEDs would be a BC337 (or maybe a 2N2222 if you can't get a BC337).
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 15, 2013, 10:26 pm
I would suggest that switching speed depends on the selected MOSFET.
Th '328P is all CMOS(FET), and it switches 40mA outputs pretty quick.
Choose one with low input capacitance.
Title: Re: 5x5x5 LED cube help
Post by: fungus on Jan 15, 2013, 10:38 pm

I would suggest that switching speed depends on the selected MOSFET.
Th '328P is all CMOS(FET), and it switches 40mA outputs pretty quick.


Sure, but the MOSFETs in a '328P are tiny...

You can get TO-92 size MOSFETs that switch really fast. They might be worth using instead of a BJT if you need a very low "on" resistance

(which LEDs usually don't)


Choose one with low input capacitance.


Easier said than done.

Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 15, 2013, 10:45 pm
so if i used 2N4401 transistors to control the cathode(because it is a npn) and 2N4403(it is a pnp) to control the anodes, will that work? keep in mind i will probably make the anode be on the colomns so that there are only five LEDs per transistor. if i used common anodes on each level instead of common cathodes, there would be 25 LEDs per transistor. i think it would be better to use the common anode on the colomns. but i may be wrong. any input is appreciated.
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 16, 2013, 03:16 am
I would suggest PNPs for common anode layers, and open drain shift registers, TPIC6B595 type, on the cathode columns.
Can use 5 '595s, 25 for cathode, and 5 to pull the PNP gates low to turn them on.
Each TPIC6B595 can easily sink the 160mA from  8 LEDs all on at once at 20mA if want them good & bright.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 16, 2013, 04:50 am

I would suggest PNPs for common anode layers, and open drain shift registers, TPIC6B595 type, on the cathode columns.
Can use 5 '595s, 25 for cathode, and 5 to pull the PNP gates low to turn them on.
Each TPIC6B595 can easily sink the 160mA from  8 LEDs all on at once at 20mA if want them good & bright.

that makes a lot of sense and would probably be the best way to do it, but i am on a tight budget. i do not want to spend more than i have to. right now i can get 20 of the 74HC595 shift registers for $5. but it would be $10 to get 5 of the TPIC6B595's. so it wouldn't end up costing much more, but i wouldn't have any spares in case something happened. i am pretty much a noob, so if i accidentally wired it wrong or shorted something out and fried all of the shift registers (or TPIC6B595's) i would have plenty to replace them. but if i bought some TPIC6B595's i would probably buy only a few since they are much more expensive. yes with regular 74HC595 shift registers i will have to buy transistors, but those are extremely cheap and they are always nice to have laying around in case i need them for something or for future projects.
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 16, 2013, 05:54 am
TPIC6B595 are 83 cents at avnet.com
Who is asking $2 each?
Less likely to make wiring mistakes with fewer parts I would think.

Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 16, 2013, 07:21 am

TPIC6B595 are 83 cents at avnet.com
Who is asking $2 each?
Less likely to make wiring mistakes with fewer parts I would think.



That's what they were asking on eBay. From a US seller, that is. I can get them cheaper from China, but they might take a month to get here. So I only buy from US sellers.
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 16, 2013, 07:29 am
https://avnetexpress.avnet.com/store/em/EMController?langId=-1&storeId=500201&catalogId=500201&action=products&term=tpic6b595&Nn=25&N=100153+4294956112

78 cents. avnet.com is a US supplier.
I ordered a tube of 20 a while ago. Don't recall what shipping was. You have other parts to buy also?
If not, 74HC595 and NPN transistors will work too.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 16, 2013, 06:09 pm

https://avnetexpress.avnet.com/store/em/EMController?langId=-1&storeId=500201&catalogId=500201&action=products&term=tpic6b595&Nn=25&N=100153+4294956112

78 cents. avnet.com is a US supplier.
I ordered a tube of 20 a while ago. Don't recall what shipping was. You have other parts to buy also?
If not, 74HC595 and NPN transistors will work too.

ok. thanks for the help!
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 16, 2013, 07:55 pm
What crossroads says is pretty accurate. Basically what he is saying is that using parts that meet or exceed your needs will reduce your chance of premature failure. You could get away with 595s, they wont break right away, but your needs exceeds the parts specifications, and *may* cause premature failure, and its not the proper way of doing things.

There are actually a lot of ways to solve this problem. I do like your idea of controlling 5 LEDs at a time, and doing that in a loop of 5 that is inside another loop of 5, and you have controlled all 125 LEDs. I dont think that I have seen that one before. It will have an extremely low duty cycle, so It will probably end up very dim, which is probably why we dont see that technique being used. It also means electrically isolating rows, which maybe tricky to make the structure hold up. its still an interesting idea, and may be worth playing around with.

If you limit the current to 8ma to your LEDs with resistors, you could reduce the current to the diodes to 8ma, then you would be within the 70ma max current spec of the 595s, and well within the LEDs specifications.

Another option is to simply run the LEDs and shift registers over spec, and expect to replace them sometime i the future, it can take months to wreck your leds or shift registers. You could build a spare in that time, and have it ready if this one fails.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 16, 2013, 10:15 pm

What crossroads says is pretty accurate. Basically what he is saying is that using parts that meet or exceed your needs will reduce your chance of premature failure. You could get away with 595s, they wont break right away, but your needs exceeds the parts specifications, and *may* cause premature failure, and its not the proper way of doing things.

There are actually a lot of ways to solve this problem. I do like your idea of controlling 5 LEDs at a time, and doing that in a loop of 5 that is inside another loop of 5, and you have controlled all 125 LEDs. I dont think that I have seen that one before. It will have an extremely low duty cycle, so It will probably end up very dim, which is probably why we dont see that technique being used. It also means electrically isolating rows, which maybe tricky to make the structure hold up. its still an interesting idea, and may be worth playing around with.

If you limit the current to 8ma to your LEDs with resistors, you could reduce the current to the diodes to 8ma, then you would be within the 70ma max current spec of the 595s, and well within the LEDs specifications.

Another option is to simply run the LEDs and shift registers over spec, and expect to replace them sometime i the future, it can take months to wreck your leds or shift registers. You could build a spare in that time, and have it ready if this one fails.


well, i was going to isolate each layer, not the rows. that way it requires less transistors and less pins on the shift registers. and i was planning on having the layers be the cathodes for the LEDs. but to do that with transistors i would have to use a npn transistor to control a pnp transistor for each colomn. i will try to attach a pic of the circuit. but that is a lot of transistors, a lot of wiring, and a lot of work. lets say i decide to do it completely with transistors and the 74HC595's. What would be the easiest way to do it? keep in mind i do not want to spend a lot of money on this. it is mainly just for learning. it probably will not stay together for very long. after i finish this i am going to make an 8x8x8 RGB cube based off of this one. this one is almost like a prototype so that i know what im doing. thats one reason i do not want to spend much money on it.

basically the circuit is just something i made really quickly. it just shows how i would control the anodes of the LEDs on each colomn. In the Circuit the LED represents a colomn of LEDs. the transistors are just ones that the circuit creator tool had. i will use whatever will work best. same goes for resistors and power. i do still need help on that. i still do not really have a good answer on the best way to power these 3.2v LEDs. any help with that would also be appreciated. thanks for what you have told me so far. everything helps.
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 16, 2013, 10:20 pm
"controlling 5 LEDs at a time, and doing that in a loop of 5 that is inside another loop of 5, and you have controlled all 125 LEDs."
I have posted that before. Doubt I could find it with a forum search - I can post it again when I get home.
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 16, 2013, 10:47 pm
Cool! If you find it, please send it to me, or post it, im mostly just curious, sometimes i do build samples, just to see it work, just because I think thats neat.
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 16, 2013, 10:49 pm
I know where it is, I had it open to maybe copy part for what I had posted earlier in this thread.
Be home in an hour or so, will post it then.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 16, 2013, 11:35 pm

I know where it is, I had it open to maybe copy part for what I had posted earlier in this thread.
Be home in an hour or so, will post it then.

awesome! thanks!
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 17, 2013, 12:48 am
Here it is.
I only did 3 of 5 rows, the other 2 are connected up the same.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 17, 2013, 02:11 am

Here it is.
I only did 3 of 5 rows, the other 2 are connected up the same.


i do not really understand that. i understand the logic and how it works, but not how you would implement it in the cube. it looks like it would control each colomns cathode, and then somehow have a second transistor to control the cathode a second time, but it would be based on each layer. i just do not know how you would wire that. maybe i am understanding it wrong. sorry for my questions, i am just trying to learn. as previously stated, i am a noob. i have been messing with electronics since i was a baby, but never anything like this. thanks so much for your help!
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 17, 2013, 05:19 am
The first 3 layers are shown. Columns are the anodes.
Each layer is made of 5 groups of 5 common cathodes  - one group of one layer is turned on at a time.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 17, 2013, 07:04 pm

The first 3 layers are shown. Columns are the anodes.
Each layer is made of 5 groups of 5 common cathodes  - one group of one layer is turned on at a time.

but wouldnt turning on group 1 section 1 turn on that whole section? not individual LEDs?
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 17, 2013, 07:14 pm
I think I was imagining something different than that, but that is pretty interesting too.

It looks to me like that does all rows at the same time, but does one section at a time, meaning a 20% duty cycle.

I was thinking something that would do one section on one row, then sequence through each section, until it gets to the last section, then shifts to the second rows first section, sequences through each of that rows sections, and moves on to the next row, until it completes each section in each row one time. I think that would be a 4% duty cycle.

Actually building one of those seems quite challenging, but I could be wrong.

suicidalacorn, I think that anode pin controls the individual led, in each section of 5 LEDs, if I understand your question.
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 17, 2013, 08:40 pm
"wouldnt turning on group 1 section 1 turn on that whole section? not individual LEDs?"
Only if the anodes were driven high for all LEDs. Otherwise, just the LEDs with High anodes turn on.

The idea is you enable 1 group of 5 LEDs at a time, a 5x5x5 cube would have 25 groups to cycle thru. 4% duty cycle.
Driving each group for 1667microseconds would yield a 24 Hz refresh rate - leaving over 25,000 cyckes in between writes to do other stuff.
I would imagine a loop within a loop to cycle thru the groups & layers, reading from a 25-byte array (upper 3 bits ignored) to send out a new byte every 1667uS. 2nd array of 5 keeps track of group enable pins, 3rd array of 5 keeps track of layer enable pins.
There are 5 anode drive pins, 5 group select pins, 5 layer select pinsl, so the whole cube is multiplexe with just 15 pins, directly controllable by a single '328P chip with no extra shift registers. Just 15 resistors and 20 transistors.
I didn't make one myself, just helped the original requestor with a design that could be done.
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 17, 2013, 09:20 pm
Cool, thanks for the explanation, I had missed the third group of pins, now i see 3 and understand that the other 2 would go with the last 2 rows.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 17, 2013, 11:21 pm

"wouldnt turning on group 1 section 1 turn on that whole section? not individual LEDs?"
Only if the anodes were driven high for all LEDs. Otherwise, just the LEDs with High anodes turn on.

The idea is you enable 1 group of 5 LEDs at a time, a 5x5x5 cube would have 25 groups to cycle thru. 4% duty cycle.
Driving each group for 1667microseconds would yield a 24 Hz refresh rate - leaving over 25,000 cyckes in between writes to do other stuff.
I would imagine a loop within a loop to cycle thru the groups & layers, reading from a 25-byte array (upper 3 bits ignored) to send out a new byte every 1667uS. 2nd array of 5 keeps track of group enable pins, 3rd array of 5 keeps track of layer enable pins.
There are 5 anode drive pins, 5 group select pins, 5 layer select pinsl, so the whole cube is multiplexe with just 15 pins, directly controllable by a single '328P chip with no extra shift registers. Just 15 resistors and 20 transistors.
I didn't make one myself, just helped the original requestor with a design that could be done.

oh ok. that makes more sense. i thought you were saying to have constant current driving the anodes at all times. so you would just have transistors to control the anodes (or an LED driver like you posted earlier)?
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 18, 2013, 12:36 am
ok, so for driving the LEDs i plan on doing what is described in this video (or something similiar with the ideas recommended by you guys). this is what i was trying to describe before. but i will use a pnp transistor where he uses a MOSFET (because i had a hard time finding those MOSFETS and transistors are much cheaper). skip to about 32:30 in the video to see what im talking about. https://www.youtube.com/watch?v=wVYXAR1GWxU
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 18, 2013, 02:29 am
You can drive the anode with 5 arduino pins.  PNP transistors are not needed.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 18, 2013, 02:40 am

You can drive the anode with 5 arduino pins.  PNP transistors are not needed.

i am now confused. wouldnt that draw too many amps from the arduino? if i have all the anodes of each layer connected and i have 25 LEDs per layer, that would be 500ma per pin from the arduino to power it. am i misunderstanding something?
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 18, 2013, 02:52 am
You are misunderstanding - only 5 LEDs at a time will be on. That's why the discussion of cycling thru the 5 groups, and the 5 layers.
5 x 20mA = 100mA max.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 18, 2013, 03:15 am

You are misunderstanding - only 5 LEDs at a time will be on. That's why the discussion of cycling thru the 5 groups, and the 5 layers.
5 x 20mA = 100mA max.

oh ok. now i understand why you broke it up into sections. that makes sense now. so i wouldnt even need an external power supply for this since it will be using very little power. correct?
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 18, 2013, 03:20 am
Correct - no external supply needed. Use superbright LEDs tho.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 18, 2013, 03:20 am
so does that mean i can use the pwm ports on the arduino? i do believe, if i remember correctly, the arduino uno has 5 pwm pins.
*edit: i looked it up and it has 6 pwn pins
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 18, 2013, 03:24 am
Yes.
An Uno has 6 - 3, 5, 6, 9, 10, 11
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 18, 2013, 03:25 am
awesome! thank you so much for all of your help! i really do appreciate it! ill try to post pictures of the finished cube when i finish it. i do believe i have all the information i need to feel comfortable ordering parts and not worrying about buying the wrong things.
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 18, 2013, 05:27 pm
I really want to build one of these, sadly I have a lot of things going on, so not sure when i will be able to get around to it. The difficulty, as I see it is the isolation of each row. I will be curious how you work that one out.

Thanks again crossroads, I may build one of these, but mostly I really like the idea. Nice work that.

After typing this post, I had a crazy idea. RGB LEDS. It would need a total of 25 control lines. I suppose you could do bi-color LEDs using a total of 20 control lines.
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 18, 2013, 06:59 pm
Yes, having 5 isolated groups per row would make it a little trickier mechanically vs having the whole layer connected.

RGB, yes add 10 more control lines.

Could use '1284 for that, 32 IO total. Could achieve same update rate, send out 2 bytes of anode info vs just 1.
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 18, 2013, 07:35 pm
you would be doing 300ma, instead of 100, You might not even have to use different transistors for the sourcing, so it sounds like you could do this without having to change anything else.

It seems to me that you could also do the anodes differently, like with shift registers or LED drivers. I wonder, if you serialized all the data, could you run this off an attiny?

That 32kb data limit may be an issue too, it seems that isnt much space for 4x4x4 RGB cube, and a 5x5x5 is twice the data.

I was thinking about the mechanical aspect, and Im thinking if we turn it on its side, so that the 25 freestanding iines of LEDs mounted to the bottom plane, (similar to the charliecube), it might work. I will have to ponder this a bit more.
Title: Re: 5x5x5 LED cube help
Post by: retrolefty on Jan 18, 2013, 07:55 pm
I might add from experience building a 5x5x5 led cube to be sure to use diffused leds as the brighter leds are too directional in their light to give good observation from wider angles of view. Narrow spread leds will have a negative effect on a lot of the visual pattern effects, where diffused leds give better consistent views.

Lefty
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 18, 2013, 07:58 pm
I've read of people lightly sanding them to diffuse them, dipping white paint, putting a white ping pong ball over them ...
Title: Re: 5x5x5 LED cube help
Post by: retrolefty on Jan 18, 2013, 08:03 pm

I've read of people lightly sanding them to diffuse them, dipping white paint, putting a white ping pong ball over them ...


Yea but doing that for 125 leds can get very boring after awhile and it's just makes more sense to buy diffused leds in the first place. They don't carry a cost penalty.

Lefty
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 18, 2013, 08:21 pm
i bought 10,000mcd LEDs because i figure i can always make them dimmer with code or resistors, but if i get like 1,500mcd LEDs i cannot make them brighter. CrossRoads also recommended high brightness LEDs. unfortunately they did not come diffused, so i plan on putting them in a drill and using that to sand them down. i know it will be a lot of work, but oh well. i wanted the higher brightness LEDs to be safe and not risk having a super dim cube.

edit: this is the link to the LEDs i bought. i bought 2 lots.
http://www.ebay.com/itm/100-x-3mm-round-Blue-LED-superbright-bulb-lamp-light-/230634491097?pt=LH_DefaultDomain_0&hash=item35b2e30cd9
Title: Re: 5x5x5 LED cube help
Post by: retrolefty on Jan 18, 2013, 08:24 pm

i bought 10,000mcd LEDs because i figure i can always make them dimmer with code or resistors, but if i get like 1,500mcd LEDs i cannot make them brighter. CrossRoads also recommended high brightness LEDs. unfortunately they did not come diffused, so i plan on putting them in a drill and using that to sand them down. i know it will be a lot of work, but oh well. i wanted the higher brightness LEDs to be safe and not risk having a super dim cube.


But then again diffusing the leds will take the same light output of the led and spread it over a wider beam, so I don't think you gained anything by starting out with 'high brightness' in the first place just to then sand them down Vs getting diffused leds in the first place. However the proof is in the tasting of the pudding so maybe when you are done get a single diffused led of the same size and see if you did indeed gain any overall brightness.

Lefty
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 18, 2013, 08:34 pm
Sanding them to diffuse the output I am sure will be a lot less work than the actual assembly and all the lead bending/alignment prior to soldering that is needed for cube stability and overall squareness.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 18, 2013, 08:35 pm

But then again diffusing the leds will take the same light output of the led and spread it over a wider beam, so I don't think you gained anything by starting out with 'high brightness' in the first place just to then sand them down Vs getting diffused leds in the first place. However the proof is in the tasting of the pudding so maybe when you are done get a single diffused led of the same size and see if you did indeed gain any overall brightness.

Lefty

yeah, that makes sense. but i guess we'll find out when i get the LEDs. they are supposed to come next tuesday. i'll update you guys with my progress throughout the build. but i am expecting to have issues with coding. i know java so c++ shouldn't be hard to learn. ill probably watch a bunch of arduino tutorials on coding, but i may still need help with coding for the shift registers.
Title: Re: 5x5x5 LED cube help
Post by: fungus on Jan 18, 2013, 08:52 pm
Sanding works well... the results are usually better than the real thing. Try a couple and see.

nb Use fine sandpaper.


Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 18, 2013, 09:24 pm
I bought a bunch of LEDs for several projects, and I got clear ones because I figured that I could make them diffused if I wanted, but I couldnt make diffused clear if thats what i needed.

I have a set of 64 LEDs Im using for a wearable project, and I decided i would try diffusing them with sandpaper. I started with 400 grit, and twisting the LED in it. It took about 5 minutes to get it lightly diffused, I didnt want to spend 5 hours sanding my 64 LEDs, so I tried using the dremel with a sanding drum (about 60 grit or so), and they only took about a minute to do each, they look very opaque, but they are a bit misshaped, and rough. I havent used them yet, and as such, i cant say what way has the best results.

I may try the drill technique, that may just work.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 18, 2013, 09:32 pm
i got 75 spare LEDs so i can experiment with different diffusing techniques. hopefully i figure out something that is both fast and yields good results.
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 18, 2013, 09:38 pm
There maybe a quick easy way to use chemically diffuse them (dip in acetone, something) I also considered flat based transparent lacquer, but I just dont think it will diffuse much. I should probably experiment more.
Title: Re: 5x5x5 LED cube help
Post by: fungus on Jan 18, 2013, 09:45 pm

It took about 5 minutes to get it lightly diffused


Maybe you're using the wrong sandpaper. I can do then in about 30 seconds each.

Another way is to add a thin coat of hot glue, although it's harder to get them evenly diffused that way. It's good for weird shapes like "candle flames" though.

I haven't tried it myself but people also paint them with nail polish.
Title: Re: 5x5x5 LED cube help
Post by: fungus on Jan 18, 2013, 09:45 pm

There maybe a quick easy way to use chemically diffuse them (dip in acetone, something) I also considered flat based transparent lacquer, but I just dont think it will diffuse much. I should probably experiment more.


Hairspray?

Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 18, 2013, 09:52 pm
It is just some kind of plastic, yes?
I don't see anything about it here as an example source

http://www.superbrightleds.com/moreinfo/through-hole/5mm-red-led-30-degree-viewing-angle-8000-mcd/281/1208/
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 18, 2013, 11:37 pm
i have some 10,000mcd blue LEDs that are probably identical to the ones i bought. i only have about five left because i have used the others. but when i get a chance i will experiment with different ways of diffusing them. i will try to mess with them today, but i cannot guarantee that i will be able to,
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 19, 2013, 05:21 pm
i tried leaving a LED in finger nail polish remover (acetone) all last night and it did not do anything. the LED is the same as it was when i put it in. i guess sanding it is the only option i have left. anyone else have any ideas for diffusing the LEDs?
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 19, 2013, 06:30 pm
How about covering them with a frosted finger nail polish?
If it looks good, have your wife/girlfriend/teeanaged daugther help - probably be way quicker than a guy could do it 8)
Set up a piece of perfboard to drop painted LEDs onto for drying.
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 19, 2013, 06:55 pm
I tried acetone (like for painting, or cleaning), and i tried some brush cleaner (it has more aggressive solvents like MEK), I just dipped them, and let them dry, and they had no effect (not even dulling the surface).

I may have some clearcoat with sparkly stuff in it (it seemed really cool, but it turned out horrible when I used it) I may try it on one, if I can find it.

Sandblasting would probably work really well, but Ive never used one, so I can only assume.

Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 19, 2013, 08:28 pm
brake fluid, plastic glue, brake cleaner dont seem to effect the plastic either. I seem to be out of paint stripper.
Title: Re: 5x5x5 LED cube help
Post by: retrolefty on Jan 19, 2013, 08:38 pm

brake fluid, plastic glue, brake cleaner dont seem to effect the plastic either. I seem to be out of paint stripper.


Try soaking them in Coke, that is suppose to dissolve meat overnight.  :D

Lefty
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 20, 2013, 08:02 pm
So far, the only thing I can get to stick to the LEDs is model paint, and i dipped the whole LED in the paint.

Ive been searching the web, and I've found that someone had some results with thinning liquid paper with acetone, and painting the LEDs with it.

Im also considering plastic glue or clear paint, and tissue paper, or white powder (like flour or corn starch).

I've been re-thinking the RGB 5x5x5 cube, and it seems that if I change that to 4x4x4 then I need 12 and 8, or 20 total control lines. If I arrange it so that the common lead goes toward the back, and the RGB leads go down, I think it will be a stable structure, but maybe a bit ugly on the backside.
Its so freaking weird, that im seriously considering building it.
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 20, 2013, 09:16 pm
haha. ok, this is a completely random idea...but what if instead of trying to add paint and things to the cube, we took a heat gun and melted the LED a little bit. not a lot, but maybe just a little. that will either work well, do absolutely nothing, or make it uneven and look terrible. but it *may* work.
Title: Re: 5x5x5 LED cube help
Post by: CrossRoads on Jan 20, 2013, 09:20 pm
Dang. What are they covered in?  I thought it was just plastic. Maybe not?
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 20, 2013, 11:35 pm
So far, searching the internet has lead me to "plastic" and "epoxy resin", which is a bit too general.

My guess is that heat will pop the LEDs before diffusing, but its worth a try.

It also seem that I've messed up LEDs by getting super glue on them (the fumes can diffuse the plastic).
Title: Re: 5x5x5 LED cube help
Post by: fungus on Jan 21, 2013, 01:46 am

haha. ok, this is a completely random idea...but what if instead of trying to add paint and things to the cube, we took a heat gun and melted the LED a little bit. not a lot, but maybe just a little. that will either work well, do absolutely nothing, or make it uneven and look terrible. but it *may* work.


It may deform them but it won't roughen the surface...
Title: Re: 5x5x5 LED cube help
Post by: Hippynerd on Jan 21, 2013, 02:09 am
Superglue and toilet paper actually works pretty well, the hard part is getting an even coating of glue, and paper. Superglue and cornstarch also worked well, but is also dependant on an even coating of glue.

I tried putting the LED in a drill, and used a file, it worked pretty good, only took about a minute, but leaves circular scratch marks in the LED. The hard part was getting concentric in the chuck. (a 4 jaw chuck would be a lot better than 3 jaws)

I tried using a lighter to melt the plastic, and it did sort of smoke it a little bit, but I dont want to get it hot enough to melt, its just too messy and stinky. but if you could get the surface to liquify, then roll it on a cloth, you might be able to unsmooth the surface.

Im also wondering if just diffusing the tip would be good enough?
Title: Re: 5x5x5 LED cube help
Post by: suicidalacorn on Jan 21, 2013, 05:47 am

Im also wondering if just diffusing the tip would be good enough?

it probably would be. all (at least most) of the light is going out through the tip. even if that was just diffused with sandpaper or a file, it might just be enough.