hello,

i am not completely sure what specs i should be looking for with reverse
voltage and forward and voltage drop...

so will these LEDs work? they are the cheapest 3mm white LEDs that i
could find. i don't like going cheap but the others are a buck a pop.

http://www.coolerguys.com/840556011262.html

Yes it would be nice if we could get som spesifications on the leds 
minimum.maximum values...
My two kits are in the mail juhu!!
a

I'm going to Jameco today and am trying to sort this out.

In this thread
http://forum.monome.org/topic/943#new
tehn says the LEDs in the 'new units' are Jameco 33307
http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=333307

The spec sheet for the LED driver is here, check page 11 for specs:
http://datasheets.maxim-ic.com/en/ds/MAX7219-MAX7221.pdf
but the dang chart doesn't have units, I believe it's kilo-ohms, the 
resistor in the kit is a 9.69k, so on the spec sheet that's the upper 
right corner, making for a VLED of 3.5V @ 40mA which is where tehn gets 
the 3.5V drop for LEDs.  That means the LED has 3.5V across it when its 
on and get 40mA through it.  **that's just outside the spec from the 
Cooler Guys**

The more I look at this I think there's an easier option.
Get a 100kOhm potentiometer (at least 70kOhm)
Buy whatever LEDs you want, pick one with a wide viewing angle and 
decent brightness (mcd - millicandles).
For the Vd for that diode, check the 7221 spec sheet, set the 
potentiometer accordingly then tweak it a little bit to adjust the 
brightness.

Gah... there was a thread with more info, can't find it.


A thread where tehn mentions 1.7Vf (Vd) @ 20mA
http://forum.monome.org/topic/236#1439

As the kit stands look for LEDs with a turn on voltage of 3.5V and can 
take 40mA (too much current blows them out.)  Order at least 70, if you 
get 64 and one or two blow you won't be happy, get extra and experiment 
a bit.


There's the Jameco catalog here
ftp://ftp.jameco.com/Archive/Catalog%20272/272Catalog.pdf
<---- that's a 332 page .pdf give it time to download.

I was going to get surface mount because for me they're easier to work 
with but SURFACE MOUNT WON'T WORK in the kits, the pads for the LEDs are 
on the UNDERSIDE of the board.  The holes are through plated but I want 
it to be more solid that than and don't want to much with 64 of them.

So, I'm looking at that Jameco catalog starting on page 50.  Two things 
to look for first.
Under the 'FIG' column at the left, we want "Fig 1"
Under the 'Viewing Angle' on the far right we want something at LEAST 70 
degrees or better.  70' is what the current ones were at, don't want to 
go narrower than that or the LED might look like a dot on the button 
rather than a glow.  tehn would know better, he's played with more of 
these.

I'm hoping for blue, don't see anything.  The tough part is that the 
type we want have narrower viewing angles.


I hope that helps and I didn't mislead anyone.

Thank you! Looking forward to hear the result of youre research today.
a

***All this is pending a reality check from tehn, he's done a lot of 
experiments with LEDs on this babies***

OK OK OK... I went to Jameco and the parts I picked above were in the 
wrong form.

Do yourself a favor and print out the catalog pages of interest, it was 
a lot easier to find parts with a catalog in front of me.

In the end I came home with 70 Jameco P/N 333358 at the top of page 54 
for just $17, if I don't like them it was a cheap mistake.

I did not want red, green would be OK, I really really wanted blue but 
no dice, orange is OK, the catalog has it listed as amber, anyway, 
should be fine and I can replace them later.

So let's look at that catalog page .pdf
first column - Jameco part number, tell them this to get a part

2nd column - cross reference to another part, didn't use that

3rd column - what the part looks like.  this is where I screwed up in 
getting the wrong part, "figure 1" in any section can be different from 
another section.  We want figure 1 as shown at the top of that page.

4th column - color.  red is the most ubiquitous, blue is hardest to 
find.

5th column - lens feature.  just some info on what the lens is like, the 
top of the LED

6th column - LED size.  we want 3mm T1 but skip this column, go to 7

7th column - Diameter.  This is 1 of 3 places to look.  We want one that 
says 0.119/3 which means the diameter of the lens is 0.119 inches or 3 
mm.  I believe I read that tehn said 5mm LEDs won't work as well.

8th - dimensions, no big deal, redundant for this part

9th - lead spacing.  0.100" is standard, no big deal

10th - Vf.  This is the diode voltage you plug into page 11 of the 7219 
LED driver spec sheet.  This is the voltage across the LED when it's on.

11th - mcd.  millicandles, how bright is the thing?  This is the 2nd 
place to track.  It seems monomes have used anything from 100-900mcd in 
their designs.  This also ties into viewing angle.

12th - wavelength - just another description of the color.

13th - viewing angle.  this is the 3rd place that's important to look. I 
wanted 100'+ of viewing angle, I had to settle for 40'.  After staring 
at the catalog for a while it dawned on me that viewing angle and 
brightness are related.  Take a bright light with a narrow angle and 
make the angle wider, that bright light won't be as bright, it's spread 
out.  So, I think I went with a good average on that one, 40' but really 
bright.


So, I'll look up a Vf of 1.7V, check the 7219 page 11 table, set a 
potentiometer to that resistor value, put it in place of the "iset" 
resistor (iset means current setting in case you were wondering) and 
adjust it a LITTLE to get the brightness where I want it.  Then take the 
pot out of the circuit and replace it with the resistance you came up 
with, OR just leave the pot in there, maybe put a touch of glue on it. 
Leave it in just to be lazy ;) .

it also occurred to me that people should get a pair of tweezer for 
soldering in the diodes (not the LEDs).

put a dab of solder on one pad (I do the right side, I'm right handed)
put the diode on the board near the solder
grab the diode with the tweezer
scoot the diode over to the solder while you heat the solder up
push the diode into the solder, line up the left side
remove the soldering iron, count to 3
let go of the tweezers
solder the left side.

I don't know how I'd do it without tweezers, the diode would stick to 
the soldering iron.

Whether or not the white leds will work, these are cheaper:

http://cgi.ebay.com/50P-Mega-White-LED-3mm-5000mcd-Free-Ship_W0QQitemZ140133683863QQihZ004QQcategoryZ66952QQrdZ1QQcmdZViewItem

http://cgi.ebay.com/100x-White-3mm-LED-5000mcd-Lamp-Light-Free-Resistors_W0QQitemZ300127020303QQihZ020QQcategoryZ66952QQrdZ1QQcmdZViewItem

eBay in general has the best deals on LEDs.

http://business.search.ebay.com/3mm-white_Industrial-Electrical-Test_W0QQcatrefZC12QQfromZR40QQsacatZ92074

-Colin

those have 20 degree viewing angles, might be a bit narrow, I'd consult 
tehn on that call.  the brighter they're rated at, the more likely 
they'll have narrow viewing angles.

my $0.02, thanks for finding a cheap source.

i still know nothing.

what is a good way to figure out whether LEDs will work as is? what can
i read to understand how all these specs matter? normally if i look at
sets of numbers long enough they begin to make sense. that is not
happening here. no one wants to present data on their LEDs in a uniform
manner.


i am tempted to just get the same ones in the normal monome even though
that isnt my vision. (i know tehn said they discontinued the part but he
is finding a replacement)

i ...just want some white LEDs man. LoL.why do people insist on SUPER 
BRIGHT white leds ? nothing seems below 4000mcd.

if it's the brightness, just turn down the current going through the LED 
by using a smaller value for the iset resistor that goes on the logic 
board.

you want a white, low brightness LED??  Let me know, I'll look through 
the Jameco catalog and recommend one, I took today and tomorrow off of 
work.

keep it simple, guys. this isn't as complicated as it sounds. there are 
lots of parameters for leds, but it's really just this:

what color? (nm value, google "visible spectrum")
what size? (you want T1 = 3mm)
how bright? (higher mcd = brighter)

seriously, that's it pretty much.

on print version of the jameco catalog, all of the standard and medium 
brightness leds that are T1 (3mm) will work just fine. some of the 
super-brights might also work.

here are some suggested part numbers:

yellow: 3333294
red: 333260
green: 114681

note that 137411 has a Vf of 4.8, this won't work! get led's with a Vf 
at or below 3.5 to be certain, though i'd be curious to have someone 
test out higher Vf leds. just get a few, test them out without soldering 
them in.

more leds, brighter:

red: 333374
orange: 333358
blue: 334764

(I had e-mail notification turned on)

tehn-
I've been psyching myself out over viewing angle, does it matter?  The 
asthetic aspect of these are important, art, music, science.

Also, the 7219 LED driver and the iset resistor, is it picky about the 
settings?
I only have this one to play with, what was your experience?  With 
different LEDs there's different current and voltage settings per page 
11, how much does it REALLY matter?  When you tried different LEDs do 
you bother to change the iset resistor?  One size fits all?

Thanks!

i've put a pot in the iset resistor for testing, but 10k seems safe for 
pretty much everything.

viewing angle changes slightly how the light gets diffused, but there's 
a pretty substantial chunk of silicone as a diffuser.

again, i suggest making first a test order, get 8 different leds, then 
choose one for the real thing.

Hi,
I have been testing each LED I place in my circuit before I solder them.
I have three AA bateries taped together, with wires sticking out and 
into a proto-board.  If the LED lights up, it's good to go.

The first row, is composed of these, and they light-up good:
http://www.sparkfun.com/commerce/product_info.php?products_id=532
I see them leaning towards orange, not yellow but I guess it's just an 
artifact of under-powering them...

I have bought 70 of the following to use on my 40h kit:
http://www.sparkfun.com/commerce/product_info.php?products_id=529

Yet they don't light up.  I guess, the three AA reduced to (3.4 V) 
through resistor network has not enough juice??

The big question is Will the above BLUE superbright LEDs Work?
The small print question is the following clause:
The LED driver on the monome can theoretically supply each LED with 
3.5V,
My chosen LED has a nominal mystery value of 3.4V.  3.4<3.5 so this 
should work.  Is this the correct analysis or am I comparing oranges and 
apples?

sorry for the overcomplexification of things: It's just that I read the 
debate and a lot of this information has to be inferred because it is 
sort of stated implicitly; maybe I can draw out a simple rule-out once 
and for all.

many thanks,
-h

3.4V should work. i can't say for certain because i've never tried them, 
but they *should* work according to the datasheet of the max7221.

again, test them in the grid pcb without soldering them before 
committing.

too late, for about 12 of them.

I did try to test them with the above described batteries, but they 
wouldn't light up; I guess I better finish that ATX-PC-PS unit to 
electronix PS conversion project.

I am operating on the premise that they will light up when they have 
more current through them (perhaps the batteries are too low) I 
registered 220 mA yesternight....

When my logic kit arrives, I'll power these babies up from the headers, 
getting power from USB ... I'll let everyone know.

att.
-h

(thanks, btw)

on your voltmeter, set it to the setting with the picture of the diode 
on it (the one where it beeps when you touch the probes together.)  put 
the LED across the leads, it should light, if not, reverse it.  when the 
LED lights the Vd for the diode shows on the voltmeter.

220mA would fry most LEDs, it's about 10 times the current they expect.

I'm not sure about the LED driver on the monome kit, but this is how you 
work with LEDs.
- Find the Vd (turn on voltage, usually 0.7 - 4V)
- Find the recommended current, usually at the top of the charts in the 
spec sheet they'll say "tested at 20mA or whatever", that's a good sign 
they expect 20mA across them, call that Id.
- Figure out your supply voltage, I'll refer to that as Vs.

(Vs-Vd)/R = Id

R = a resister you put in series with the diode


BUT in all reality, just try some out with the monome kit, there's no 
need whatsoever to go through this, tehn has already done all the work. 
that's great that you're learning and asking all the right questions but 
a lot of this doesn't apply to the monome kit but rather a hobbyist 
electronics web site.  I fear people are going to read about your trials 
and tribulations and think they'll have to go through the same obstacle 
course.  you'll be fine, wait for the kit, you'll be rocking your own 
flavor in no time.

***************************************************
* DISCLAIMER:                                     *
*                                                 *
* MOST OF MY POSTS, QUESTIONS and GENERAL ANXIETY *
* REGARDING PUTTING TOGETHER THE KITS DO NOT      *
* REFLECT THE GENERAL EXPECTED EXPERIENCE.        *
* THOSE PAINS ARE DUE TO THE FACT THAT I CHOSE A  *
* DIFFERENT KIT, THAN THE ONE SOLD HERE.          *
* REGARDING DIY KITS, I CAN BE MASOCHISTIC        *
* LIKE THAT, IT'S TRUE.  BEST REGARDS. H.         *
***************************************************

There :D
Thanks,other than that, you are so correct in so many places.
AND, I think a post like that was needed. I understand this is the
power of the WIKI concept.  See, your post should really be a
DIY reference article.  Perhaps only a Pathfinder, with links
everywhere that's needed.  It's basically a glorified FAQ edited
whithin a WIKI, in wiki-fashion by all.

Perhaps I read the units wrong, but then 220uA is too small ...
Need to investigate.  Having (anxious) fun.  Many thanks.
-h

lmfao!!!  godspeed with your kit and journey.  you'll be just fine.

good luck, have fun!!

Jameco part number: 334749

These are some blue LEDs that should work just fine. They are cheaper 
than the ones that then suggested(although still pricey), they have a 
wider viewing angle and lower voltage. tehn, maybe you could shed some 
light on why you chose the blue one that you did? If it was just out of 
looking through the catalog real quick, I would say that you should 
suggest these instead since they are much cheaper.

my suggestions were arbitrarily based on whatever jameco catalog i had 
lying around.

what's the mcd difference between these two blue leds?

Theyre actually the same MCD at 900.. Pretty bright. I tested one the 
other day and they look damn good.

Actually, I cant tell the difference between the two, why the one you 
picked is so much pricier. The only differences I can see from the 
catalog is that the one I suggested is 470nm wavelength with a 45 degree 
viewing angle and the one you have selected is 470 with a 30 degree 
viewing angle. And the one I have is 3.2v as opposed to the 3.7v one you 
suggested. Also, the dimentions appear to be slightly bigger on the one 
you mentioned. Not significantly though. Like I said, they're both 
900mcd though.

Like I said I tested one and it looks fantastic. I put in an order, I 
will let you know how it works out but I don't anticipate any problems.

Here's the link for all you blue LED fans:
https://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&pa=334749&productId=334749

Part No: 334749

2 questions

will these LEDS work?
http://cgi.ebay.com/50-WHITE-LEDs-6000mcd-3mm-led-leds-FREE-RESISTORS_W0QQitemZ270099240580QQihZ017QQcategoryZ294QQtcZphotoQQcmdZViewItem


do i need to ask for resistors?

you don't need any resistors whatsoever.

it's within the voltage spec, so they should work, i think?

also weird auction, in that it says they're in palmdale, ca, but ship 
from the uk? hmm.

i'd suggest getting the manufacturer part number, and finding the real 
datasheet on your own. the possibility for misinformation on ebay is 
huge.

Is the T1 (3mm) restriction due to physical layout of the keypad kit or 
the circuit?
If I'm using my own display, could I use T1 3/4 (5mm)?

keypad kit restriction

yeah, clearance under the buttons.  the best bet is to get a couple 
types, try them then buy 70 of what you liked the most.  in hindsight it 
seems that just about any LED works and looks good as long as it's under 
the voltage limit (3.4V?  don't recall right now, too lazy to go find 
it) tehn specs out and is 3mm through hole.  surface mount LEDs will 
also work, they're just not as easy to solder onto the board.

ok.  so i've read all the above posts, and have a pretty decent 
understanding of what i need for the LEDs.  I want blue leds, and found 
some with the following specs:

Reverse Voltage:5.0 V
DC Forward Voltage: Typical: 3.4 V Max: 3.8V
DC Forward Current:20mA
Viewing Angle:20±10 degree

I havn't read anything about REVERSE VOLTAGE specs, and quite honestly 
don't know enough about electronics yet to make the call myself.

Any help?

Also, these LEDs i found seem super bright (Luminous Intensity-MCD: Min: 
8000mcd  Max: 13000 mcd) but their viewing angle is rather narrow.  Is 
that really going to matter much if they are indeed super bright?  Will 
it more or less 'glow-up' the entire button?

Thanks guys!!

I'm sure they'll be fine.  Best to get a few and try them or make sure 
you can return the bunch.

I pretty much over analysed the LEDs in the above posts, maybe I should 
delete some of them??

Here's a nice page on LED basics
http://www.kpsec.freeuk.com/components/led.htm

Diode voltage - A diode or LED (aka Light Emitting Diode) are voltage 
controlled current switches.  They will not let current pass through 
them until the voltage across them hits a certain value called Vf 
(forward) or Vr (reverse) (not all diodes conduct in the reverse 
direction.)  Hooked up in the forward direction (cathode <negative> at a 
lower voltage than the anode <positive end>) the voltage across the 
diode rises until it hits the forward voltage (Vf), then current flows 
(LED lights up) and then the diode maintains Vf across it.  Diodes 
aren't ideal devices, they're non-linear so Vf will be a short range of 
values, like 3.4 - 3.8V.  Reverse voltage, Vr is the voltage the diode 
holds when connected in reverse, you can ignore that value because yours 
will never be hooked up in reverse.

Anyway, the LED driver on the 40h kits is great, very forgiving.

As for viewing angle, IMO it doesn't really matter, there's enough 
silicon in the button that light disperses throughout.