Netduino home hardware projects downloads community

Jump to content


The Netduino forums have been replaced by new forums at community.wildernesslabs.co. This site has been preserved for archival purposes only and the ability to make new accounts or posts has been turned off.

xprment626

Member Since 21 Oct 2011
Offline Last Active Dec 02 2011 07:39 AM
-----

Topics I've Started

another 7 segment display

21 October 2011 - 08:01 AM

Hi netduino community!

This is my first post and my first project with netduino and I am quite excited. I will share some photos of my project, but have several questions too. You will have to forgive me, for I am a code monkey and thus the physical world is a strange place to me ;)

My wife got me a netduino plus and I got started! I did the basic blinking onboard led example naturally followed by a morse code version of the blinking led. Being already over budget getting the netduino, I stopped at radio shack yesterday and picked up some inexpensive parts, including a 7 segment led, some resistors, and a set of photo-resistors (my next project).

Posted Image

Posted Image

Attached is a short video of my project. Yes, it's corny, but it's cool!

My questions are very, very basic questions, but I want to make sure I understand what I did here ... and why :-p

  • Are all of the digital pins on the netduino 3.3V? Up to 5V tolerant?
  • The display schematic mentioned the cathode pins. This basically means ground, correct? Anode would indicate 5V, right? If you notice in my photo, I connected these to the ground on the netduino on the digital-pins side.
  • The netduino has 3 ground pins, 2 with the power and 1 with the digital pins. Why are there 3? Don't they all share a common ground?
  • Now for some Ohm's law. The display schematic indicates that the max forward current is 30mA and typical rating of 20mA. I assumed 3.3V out from the digital control pins (but checked my numbers with 5V just in case). Since I = V/R, I had V = 3.3V, I = 0.03A (30mA max on the display), resulting in R = 110 Ohms on the low end and R = 275 Ohms (assuming 5.5V and taking 20mA typical rating for the display). So far, is this correct? This means that I would need a resistor with about 275 Ohms of resistance. I went with 220-Ohms since I figured I'd probably be safe. Is this correct? Did I [potentially (no pun intended)] do damage to the led (or netduino)?
  • Does it look like I missed anything? Any connections? Any grounding/power/etc?

I apologize for the simple questions, I just want to make sure I'm understanding this correctly. I promise I will go read up on the basics more now that I got my first project done :)

Cheers!

home    hardware    projects    downloads    community    where to buy    contact Copyright © 2016 Wilderness Labs Inc.  |  Legal   |   CC BY-SA
This webpage is licensed under a Creative Commons Attribution-ShareAlike License.