I have recently purchased a class set of the Arduino Boards for my High School Engineering class. The programing is very simple for the students to understand. My end game is to use the chips for simple robotics. But before that i want to make a simple 10 LED display that the students can take home for cheap.
The Idea is that students program the chip then remove it and plug it in to their light display. Has any one done this before?
If not, I need to know a few basics.
Which pins hook up to the timing crystal?
What is the spec on the crystal?
Can the Arduino run on 9V? (Simple battery clips make 9V perfect)
Any way, i probably have more questions, But any input at this point would be great.
What you basically want to do is create a dedicated arduino just for driving LEDS?
I think a more efficient path would be to purchase/build/design an LED shield. That way you can still use the chip with oscillator and voltage regulator for other projects.
If you still want the dedicated circuit then there are a ton of examples online for building your own. look up HACKDUINO
there are a few other things necessary to just plug in the chip, but they are all well documented in the many arduino schematics floating around.
I would recommend just building the shield or using bread boards. In addition breadboard wiring is always a learning experience, especially when trouble shooting your rats nest ;D
I have also been looking at the pin configuration of the ATMEGA 328 chip, I am a little confused on which pins on he chip correspond to pins in the Arduino Software.
A basic schematic for how to hook up the Atmega chip in to a simple circuit would be ideal.
The specification for the crystal depends on the input voltage.
For a 5V system most people use a 16MHz. For my 12V boards I use
12MHz. The ATmel specification recommends loading capacitance
of 22pF or less.
The 9V battery can power a 5V system but it is not very efficient.
Most systems use a linear regulator which wastes 4/9 of the capacity.
I make a low-cost ($12) Arduino compatible board (PICO1TR) and a matching
LED matrix. You can check out the schematics which are in the datasheets.
I "charlie-plex" the LEDs which minimizes the number of lines required.
For 10 LEDs you would only need 4 lines.
See the datasheets at Loading...
and Loading...
Okay, i think i know what i am doing. a few more questions though.
Is the pin configuration on The Atmega 168 the same as the 328?
The price of the 168 is cheaper then the 328, will the 168 work if i plug it in to my Duemilanove board? Do
I need a voltage regulator if i run 4.5volts from a pack of 3 AA batteries?
I have attached a Schematic of what i think will work. does any one see a problem with it?
will the 168 work if i plug it in to my Duemilanove board
Yes but change the board type in the tools menu.
Remember you have to have a boot loader in the chip before you plug it in the board. Chips can either be bought with a boot loader ready loaded otherwise you are going to have to burn one in yourself with a programmer.
assuming 1.7V drop across each LED the across the resistor you have 5 - 1.7 = 3.3 volts
across a 220R resistor gives you 15mA per LED.
With 14 LEDs you have a total source current of:-
14 * 15mA = 210mA
Now the absolute limit for the current taken along the arduino supply pins is 200mA. Given it takes about 20mA to power the chip you are 30mA over the current where damage would be done.
So best bet is just to up the resistors a tad say to 270R.
Pins 22 should be connected to gnd.
There is no junction for the Vcc connection.
It may not be a good idea to connect AREF to Vcc since the reference
can be programmed to a voltage other than Vcc. I would
just put a 0.1uF decoupling cap on the pin.
I would change the 1K reset pull-up to 10K.
okay, i made those changes. i am a little confused about the AREF capacitor, is this what you mean? i also added the 9Volt battery clip, makes laying out the board easier.
Since crossing wires are not necessarily connected it is
a good idea to only have three lines connected at one point
(versus the cross you have for Vcc). When you are checking
your schematic it is easier to find omissions.
Use the GND and Vcc symbol more. This eliminates
a lot of wires and makes the schematic more readable.
I would use the GND symbol for C2, C3 and ground on IC1.
I am not sure why you have all the unnecessary junctions in this
schematic versus your original. I would eliminate them.
sorry about the clutter, I am using eagle to route the board and if i don't put those junctions in it doesn't seem to make the connections. Okay, i fixed the Aref to ground and cleaned it up.
