As stated, I'm fresh to this little hobby, so please fear well with my humble question. I've done minimal programming, but I studied electronics during school. Arduino excites me
Now, for mye first (massive) project that will eventually help me learn more:
My plan is to have an Arduino control a fake-make-believe radar built for recreational games. I plan to have it work by switching a key switch, which then let's me input a start code via a keypad. I plan on purchasing a serial keypad, as I've read somewhere here that it's a clever thing to do to save up inputs. After all this I'd like the Arduino to check a Gyro/leveler of some sort to se that the radar is stabile and level. If not, abort, else run. If run, output to relay to start a big external motor. I would then start up a GPS and a GSM board of some sort to send positions to some server that outputs position as a beautiful little blue spot on a map, or send a push over prowl.
I'd also like to make a fake-make-believe C4 pack that contains a RFID chip that will after being placed on the radar (on marked place, over a RFID reader) do the following:
Count down 60 seconds..
Beep or make some sound..
Disable the whole setup, power down all things
Now only a reset of the Arduino itself would able the thing to work again.
Before the flamewars begin, I would like to say that I am a learn and go type. If I have interest I will do my best effort to master the knowledge needed. The reason for taking on such a big first project is simply to learn. I will start slow, and build upon as I iron out errors.
So, the point of this post is this; Which Arduino should I get? I'd hate to use up all ports before I'm done with project!
Well, this sounds like a Learning Experience alright
Fortunately, big projects can be successfully approached by "Stepwise Refinement". Here's one reference, although the original concept is from Nickolas Wirth (The creator of the language PASCAL). http://it.toolbox.com/blogs/irm-blog/stepwise-refinement-25007
And you can parallel that by learning Arduino and the software sketches by first getting modular pieces to work as separate sketches. Wirth would have appreciated referring to software as "Sketches"...
Diagram this out as a first step, figure out what interfaces you need and how many pins they use, and then decide between an Arduino 328 or a Mega. The 328 gives you 11 usable digital In/Out and 6 Analog In (Also usable as digital I/O)..
That was definitely the process I was going to develop in. Break every Input/output into small sketches and then try to compile it gradually together. That way I don't have panic the very first day
Terry,
11 digital IO? Think you missed one
D0-D13 = 14, I could see saying 12 if you assume that D0/D1 will be tied up with serial comms (to the GPS that was mentioned).
CrossRoads:
Terry,
11 digital IO? Think you missed one
D0-D13 = 14, I could see saying 12 if you assume that D0/D1 will be tied up with serial comms (to the GPS that was mentioned).
Well, the pin 13 is tied to an LED so maybe it can't be used for something critical? I've heard of this but don't actually know why.
CrossRoads:
Terry,
11 digital IO? Think you missed one
D0-D13 = 14, I could see saying 12 if you assume that D0/D1 will be tied up with serial comms (to the GPS that was mentioned).
It's real tempting to say John's explanation was right 8) but I was wrong (How many times in 39 years I've been doing digital???) with the "Origin Zero Thing"...
One of these days, Crossroads, some month, some year, some decade, I'll catch you out...
liudr,
I missed your earlier comment about pin 13 - there is a 1K to LED to ground (uno & duemilanove), so you lose maybe 3mA of high current drive capability, and none on low.
Maybe more on a promini if the 330R is correct.
I don't install that LED on my standalone designs, nor a power LED.
CrossRoads:
... about pin 13 - there is a 1K to LED to ground (uno & duemilanove), so you lose maybe 3mA of high current drive capability, and none on low.
...
I've seen posts where a few people have had unexpected results using pin 13 as an INPUT because of that small pull-up current from the LED & resistor.
So maybe a "Newbie Suggestion" is simply use 2 to 12 first, and 13 as an output only ??
Okay, it is not a pullup - it is a series resistor from the arduino pin thru the resistor to the anode of the LED, with the LED cathode grounded. Thus the arduino pin must be driven high for the LED to be on.
It can do nothing but sink current when the arduino drives high, or has the internal pullup enabled with no external driver, or the external source drives it high.
The LED may appear to be dimly on when the internal pullup is enabled. I think that is the result you are referring, the LED being dimly on. The LED and resistor can not source any current to anything, it can only be a small additional current load to the arduino output, to the internal pullup resistor, or to an external source if the arduino pin is used as an input.
There may have been some cases where the atmega saw 5v on a non-power pin from another source when power was off, and leakage currents thru the device went out the D13 pin and made the LED appear on also.
