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Did we settle on a safe way to connect LED's to the NANO? — Parallax Forums

Did we settle on a safe way to connect LED's to the NANO?

potatoheadpotatohead Posts: 10,261
edited 2012-12-21 10:45 in Propeller 1
I'm working on the remainder of monitor use examples to finish up my "Using The Monitor" get started guide, and some pin action would be really handy at this stage. On the DE2, there are switches and pins mapped to the virtual P2 pins, so I've got LED's to work with.

On the NANO, there are just the pins and some discussion on how to safely connect them. I don't want to put something in that guide that breaks things. Could you guys take a moment and clarify how best to connect a few LED's, say 8? I'm thinking standard LED's found laying around on the average work place. I don't want things to focus entirely on the DE2, because the NANO is the less expensive option and perfectly fine for lots of testing.

I'll use the NANO picture we've got out there already and a circuit diagram for the text. If somebody wants to donate a photo to the cause, you get a seriously good karma bonus for life! +1 "good on you" kind of thing. :) Oh, and a mention as that cool person who took a photo for me. That too.

Thanks!

Comments

  • ctwardellctwardell Posts: 1,716
    edited 2012-12-21 09:08
    I used 74HC04's and 220 ohm resistors for the LED's, I grabbed 3.3V and GND from the header.

    You could easily do 6 LED's with a single 74HC04.

    Clusso mentioned using using ultrabright LED's with 10k or so resistors, but you may be excluding that with the "standard LED's" comment.

    C.W.


    One thing to keep in mind when buffering is that the P0-P31 pins seem to have weak pullups during reset.
  • potatoheadpotatohead Posts: 10,261
    edited 2012-12-21 09:16
    Well, I'm really hoping for resistors and LED's only. Maybe that's not realistic. If that's the case, and I'll let the thread percolate for a while, then I may well have to just include both options as each will require something that a person might not have. I've got a coupla super brights and 10K's around, but no 74* chips... for example. Maybe both would hit a reasonable set of people.
  • ctwardellctwardell Posts: 1,716
    edited 2012-12-21 09:25
    I just tried 2.2k using the LED's that come with the PEK and had reasonable illumination.

    That was with LED cathode grounded and 2.2K from anode to P0 of the Nano.

    Ignoring the drop of the LED the max current would be 1.5mA, so should be safe.

    C.W.
  • potatoheadpotatohead Posts: 10,261
    edited 2012-12-21 10:45
    I'm going to mark this one solved as that makes sense. However, LED + photo chatter can and should continue if that makes sense too.
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