128 build questions.

  • Good morning all, my sparkfun buttons arrived as did most of components, I just have to select the LEDs and associated resistor.
    I've got a few questions, I'm building a 128 based on two bibo boards.

    1. LEDs

    I've read various posts about LEDs covering topics including viewing angle, brightness, reliability. People seem to have vastly different opinions. I'd like a bright blue set of LEDs for a Tron like appearance :) Do the following LEDs look ok? Are they going to be bright enough? Would I be better paying for more expensive LEDs for any reason such as reliability?


    2. Bus powered vs Mains powered.

    From what I've read I'll have a USB hub internal to the device. Is there any advantage of powering the USB hub via the mains or is bus power sufficient?

    3. ADC

    I read an article on Arduinome with potentiometers (http://elettrofonesi.blogspot.com/2009/11/arduinome-x16adc-mod.html), I notice that the Arduinome firmware has support for this:

    * Changes 03/21/2009
    * Added ADC support for arduino ADCs 0 - 3. Thanks to Josh Lory for the first cut of the code for
    * this. Added handling of the ADC enable/disable serial messages, and changed Josh's checkADC code
    * to loop through the 4 ADCs rather than read each one individually.

    Does this mean that I can hook up four pots to each unsped shield, and have a total of eight for my 128? Does anyone have any links to any more resources/information (such as a build blog) on this? The post above for the 16x mod seems overly complex for my needs.

    4. Diode orientation?

    I know that for LEDs the annode goes into the square peg on the bibo board, I think the diode in the the following picture may be the wrong way round. Should the end with black line be soldiered to the rectangular rather than the rounded connection?



  • Hi,
    Avoid led from ebay.
    Because of the reliabillity, they seem to have a different brightness levels.
    But also because you have to be able to find the same later when you'll need to change some that stopped working.
    For 200 leds of a good quality you'll have to pay like 30€ or so.
    It's not a great spending compare to the rest of the project.

    I'll have a look to my keypads tonight for the diodes orientation.

  • @suburbanimal

    no way are you looking at 30 euro mate. Ill post a link later for a reliable UK retailer who i get my leds from. Its around 8GBP for 100. Perfect blue with not one led that was off colour.

  • @marto

    Though I didn't intend for that Tron-like blue, the LED's I bought are exactly that color. See my comments in the following post for where I got them: http://post.monome.org/comments.php?DiscussionID=4413&page=1#Item_4

    Had it for over a year now and things look great. Color is uniform and they're very bright. The only downside is that they shipped from China so it took about two weeks to get to me in the US. If you want to get a feel for the color check out my blog: http://ilikeblinkystuff.blogspot.com/

  • Thanks for the feedback regarding the LEDs. I'll keep searching for more resources/answers for the rest of my questions.

  • @deanjkd
    So 16GBP for 200 leds =20€
    Yeah that's pretty what i got for my yellow leds.
    Some colors are a bit more expensive the red are 40% more expensive where i bought them.
    I bought mine directly in a hardware store.

    The point i wanted to make is that the leds are not (for me) the part where you should try to get a great bargain cause having to unsolder and resolder 100s of leds is not the kind of thing you want to happen.

  • @Space_moose thanks, I checked out your videos, that's exactly the look I'm going for. The leds I linked to look almost identical to yours. I'll double check before ordering.

  • @suburb dont worry mate i wasnt trying to prove you wrong haha, just sharing my experience, the way its worded does seem a bit firm.

  • Re my diode question, do the black lines in the pic I linked to above corresponding to the line on surface mount diode in this pic:


    I'm guessing they do, and the alignment in the first pic I linked to is right, but I don't want to have to re solder 128 of them. :)

  • So I just ordered 150 leds, bright blue from ebay. The spec says "forward voltage 3.2 to 3.8v forward current 20mA(typical) 30mA(Max)". Looking at the resistor chart I think I want to be secting the 20mA 3.0v resistor, 24.5k? Does that seem right?

    On another note I'm going to pop out at lunchtime and see if I can pick up a pot from maplins to test adc on the unsped shield with the monome test app.

  • You could probably even go with a slightly lower value resistor and still be ok. If the LED's are bright enough for you at that value, then great. Can't hurt by being a little conservative.

  • My 128 is finished, well I now need to make an enclosure.

    Thanks deanjkd and space_moose, the LEDs I got from eBay are great.

    I'm planning on getting a faceplate made by http://www.zapcreatives.co.uk/

    I was wondering, I've seen some builds where you can't see the screws on the faceplate. Is it common for people to have two thinner faceplates made, one to screw to the boards and another to sit on top?

    I also need to get a faceplate for a sparkfun 64 build for a friend, I'll do some searching for templates/files for the sparkfun 64 and bibo 128.

    Thanks again for the advice. I'll post a photo once it's housed.

  • I recently made my own enclosure for a 128 (used a laser-cutter at my university) and used the two-thinner-faceplates-method. It looks great because you only see the few screws that hold the faceplate. I've used two 3mm thick plates of acrylic and the lower plate. The lower plate holds the pcbs in place, the faceplate just hides all the screws. Works as a charm and looks great.

    I've made my own drawings for the faceplates (had this urge to just have done EVERYTHING myself :D), but while looking around the forums, i've found those drawings a while ago, which might be very helpful to you. Credits go out to whoever made them. As i said, i'm not the author.

  • Thanks x2mirko, do you have any pics of your arduinome I can see?

    Zap Creatives accept .ai files (I'm pretty sure the Gimp can edit these files, if not Inkscape), I'll need to wait until I'm back at work so I so I can edit and print these faceplates to paper, purely to test them out.

  • Sure. I've attached a few pictures. The Arduinome is standing on a laptopstand

    edit: hah, forgot the attachment. NOW, here it is:

    1200 x 800 - 199K
    1200 x 800 - 236K
    1200 x 800 - 255K
  • For the Sparkfun build you may want to look at the Curious Inventor enclosure (http://store.curiousinventor.com/blog/arduinome-case-now-available-build-log/). That's what I ended up going with. Its construction is a little more industrial looking but I really dig the clear acrylic. The whole body gives off a good glow in dark environments.

  • Thanks for that x2mirko, I'm going to have to send individual files for each that I want cut to the zapcreatives people. My Inkscape fu is weak. Could some one confirm that the dimensions I have are right, say for the bibo 123 top? I have:

    w: 419.453mm
    h: 216.253mm

    I just don't want to send my files off only to find I've made a mistake when I receive tiny faceplates :P