Go Down

Topic: Simple 10 - 12 LED Display (Read 3838 times) previous topic - next topic

nobikes

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.  8-)
High School Engineering Teacher

artjumble

Quote
Which pins hook up to the timing crystal?

What is the spec on the crystal?

Not sure if this is exactly what you need, but take a look at this http://www.uchobby.com/index.php/2007/07/01/ardunio-breadboard/ for a minimum setup.

Or you could buy one of these http://www.moderndevice.com/products/rbbb-kit and then duplicate the setup.

Quote
Can the Arduino run on 9V? (Simple battery clips make 9V perfect)

Yes. Look around here, I think there is a very recent thread talking about 9V hookup.

donkahones

#2
Jun 29, 2010, 06:39 am Last Edit: Jun 29, 2010, 06:43 am by donkahones Reason: 1
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
http://www.instructables.com/id/Perfboard-Hackduino-Arduino-compatible-circuit/

you will need a voltage regulator as the atmega 168/328 chip  needs between 1.8 and 5.5 volts....7805 http://www.datasheetcatalog.org/datasheets/228/390068_DS.pdf

The usual timing crystal used is http://www.vishay.com/docs/35014/xt49s.pdf
between pins 9 and 10.

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



nobikes

Thank you, that gets me closer.

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.  
High School Engineering Teacher

donkahones

assuming you have the duemilanove cross reference this:

http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf

with this:

http://www.atmel.com/dyn/resources/prod_documents/doc8161.pdf

Quote
A basic schematic for how to hook up the Atmega chip in to a simple circuit would be ideal.


see above, Hackduino or the duemilanove schematic

nobikes

#5
Jun 29, 2010, 06:50 am Last Edit: Jun 29, 2010, 06:51 am by nobikes Reason: 1
Thank you Again. That instructable is perfect. I will draw up a schematic tomorrow.
High School Engineering Teacher

jluciani

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 http://wiblocks.luciani.org/PICO/PICO1TR-index.html
and http://wiblocks.luciani.org/PICO/PICO1TR-LED-L-index.html

(* jcl *)
www: http://www.wiblocks.com
twitter: http://twitter.com/wiblocks

nobikes

#7
Sep 13, 2010, 12:08 am Last Edit: Sep 13, 2010, 12:18 am by nobikes Reason: 1
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?

Thank you for all the help

http://sites.google.com/a/theprojectinventory.com/envertech/_/rsrc/1284329142030/enver-creek-engineering/engineering-level-2/arduino/arduino-4/light%20display.jpg
High School Engineering Teacher

Osgeld

#8
Sep 13, 2010, 12:26 am Last Edit: Sep 13, 2010, 12:32 am by Osgeld Reason: 1
Quote
Is the pin configuration on The Atmega 168 the same as the 328?


yes

Quote
The price of the 168 is cheaper then the 328


usually the same. the 168 might be nominally cheaper

Quote
will the 168 work if i plug it in to my Duemilanove board


yes

Quote
Do I need a voltage regulator if i run 4.5volts from a pack of 3 AA batteries?


no (though that does not leave a lot of wiggle room with discharging batteries and the voltage vs speed ratio)

Quote
I have attached a Schematic of what i think will work. does any one see a problem with it?


not off hand
http://arduino.cc/forum/index.php?action=unread;boards=2,3,4,5,67,6,7,8,9,10,11,66,12,13,15,14,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,86,87,89,1;ALL

deSilva

Quote
does any one see a problem with it?

You should have a ground connection to pin 8..

nobikes

#10
Sep 13, 2010, 12:42 am Last Edit: Sep 13, 2010, 12:43 am by nobikes Reason: 1
Okay, I have added the ground off of pin 8. does this look appropriate?

High School Engineering Teacher

Grumpy_Mike

Quote
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.

Grumpy_Mike

Just been looking at your circuit again.

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.

nobikes

High School Engineering Teacher

deSilva

#14
Sep 14, 2010, 03:47 pm Last Edit: Sep 14, 2010, 03:47 pm by mpeuser Reason: 1
Or just have some green LEDs among them ...

Go Up