7 replies to this topic

[WannaFly]

I saw this and thought it might be a "simple" project for a beginner like my self: http://www.dougsword...om/gallery.html Since it's mainly turning a set of LED's on/off. The hardest part I think will be designing it to look good. I haven't used my netduino in a while and want to start again, but I've never used the digital ports, only the analog. I've read the forums a little and haven't found any answers to my main question, which seems like it shouldn't be too hard: How can I turn LEDs on/off with the digital ports? I believe I can do this without the complexity of a shift register/etc because I can tie one word to one port: ten half quarter twenty five minutes past to one two three four five six seven eight nine ten eleven twelve is 20 words, "it is" and "o'clock" will always be on. I'd like to set up a simple mock up with 2 or 3 single leds and turning them on/off through the digital pins and once I know for sure how to do it i'll plan on making the enclosure and LED grid. Any advice would be great, Thanks in advance!

[ItsDan]

The Projects page (http://www.netduino.com/projects/) has a tutorial on blinking an LED but conceptually you define an OutputPort for each pin (so you'd have 20, likely in an array), and can simply call obj.Write(true) or obj.Write(false) to switch the pin to HI or LO respectively. Driving a handful of LEDs off the board itself I don't think is a major problem but I'm assuming for something like the project you've linked even a single pin might control a dozen or more LEDs, so you need to make sure you're remaining aware of the current limits of the pins. I think normal practice would be to use transistors to use the signal from the Netduino to control the larger load needed by the project.

[WannaFly]

The Projects page (http://www.netduino.com/projects/) has a tutorial on blinking an LED but conceptually you define an OutputPort for each pin (so you'd have 20, likely in an array), and can simply call obj.Write(true) or obj.Write(false) to switch the pin to HI or LO respectively.

Driving a handful of LEDs off the board itself I don't think is a major problem but I'm assuming for something like the project you've linked even a single pin might control a dozen or more LEDs, so you need to make sure you're remaining aware of the current limits of the pins. I think normal practice would be to use transistors to use the signal from the Netduino to control the larger load needed by the project.

ItsDan:
Thanks for the info, I did get the onboard switch to light an LED and it was pretty simple.

I kind of understand what you mean about driving a lot of LEDS, I believe the most on at a time would be close to 100, one for each letter. Unfortunately I haven't used transistors yet so i'll have to pick them up and mess around with them a bit.

[ItsDan]

I started out buying the Arduino Starter Kit from SparkFun. It included an Arudino Uno, breadboard and board holder, bunch of leads, LEDs, resistors, various parts to get you started. My Arduino sits unopened as I've used all those parts with my Netduino instead. However it's a bit overpriced I think. I found this just the other day: http://www.seeedstud...e023ca97644b739 It has many of the same parts, minus the microcontroller, for under $20. Unfortunately it doesn't seem to have transistors but if you likewise could use a misc parts bin like I needed it might do well for you. I'm not affiliated with the site, found it mentioned in another thread on this forum though.

[Chris Seto]

Why not use a large LCD? -- OR -- why not have the words on scrolls? That's quite easy to do and you can make the scrolls go just fast enough to be an incremental indicator.

[WannaFly]

ItsDan: I have a starter kit that I bought off of ebay, and have started messing around with it. Thanks for the recommendation though. Chris: Because I was hoping it would be an easier project just lighting LEDS, it took me about 2 hours last night to get a piezo speaker to make a sound, I can't imagine output to a LCD/LED yet. It's also more of an "artistic" project that I think would look good in my office temporarily.

[Dan Morphis]

However it's a bit overpriced I think. I found this just the other day:
http://www.seeedstud...e023ca97644b739

It has many of the same parts, minus the microcontroller, for under $20. Unfortunately it doesn't seem to have transistors but if you likewise could use a misc parts bin like I needed it might do well for you.

If your in the US, check out Radio Shack. I picked up a pack of 500 resistors for $12, and a 10 pack of PNP and a 10 pack of NPN transistors for $3. Couple that with a pack of 1N400x diodes for $3-4 and find some caps and you will have all the basics.

AllElectronics.com has a great prices too. You can get a package of 100 1N4004 for $3.80 and a 10 pack of PNP's for $0.80 and they have the resistor pack for $11.50

Then I would pickup a parts bin from your home improvement store, I think I paid $20 for mine and I have all my resistors, caps, diodes, transistors etc all organized and easy to find!

[ItsDan]

That's suprisingly reasonable for Radio Shack. I always found them massively overpriced. I haven't been much into electronics for a long time but I'd use Jameco.com a number of times. Fast shipping from what I recall.