Go Down

Topic: Simple 10 - 12 LED Display (Read 3833 times) previous topic - next topic

nobikes

Okay, I put the circuit together this week with no luck. Can any one see a problem with this schematic?

All of your help is greatly appreciated!
High School Engineering Teacher

jluciani

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.

I also like to add a couple of things --
protection diode for the reset pin and ADC filtering.
For a schematic see the datasheet at
http://wiblocks.luciani.org/PICO/PICO1TRC-index.html

(* jcl *)

http://www.wiblocks.com
www: http://www.wiblocks.com
twitter: http://twitter.com/wiblocks

nobikes

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.
High School Engineering Teacher

jluciani

The AREF cap goes from AREF to GND (not VCC).

A couple of style suggestions --

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.

(* jcl *)

http://www.wiblocks.com
www: http://www.wiblocks.com
twitter: http://twitter.com/wiblocks

nobikes

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.
High School Engineering Teacher

jluciani

Looks much better.

You may want to ask a separate question about Eagle and junctions.

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

nobikes

thank you, I think i have it now. Here is an image of the circuit board. I know the leads are a little close together, but i am trying to keep things simple for my students. The thicker leads tend to have less troubles after the etching tank.
High School Engineering Teacher

nobikes

#22
Jan 14, 2011, 05:11 am Last Edit: Jan 14, 2011, 05:13 am by nobikes Reason: 1
feel kinda bad for not posting my finished results. I had to remove two LEDs from the board, just couldn't get them working. But my students were very excited about doing it with 12 LED. We made 10 of them and they all worked well.

Attached is my finished Eagle file. feel free to use it. If any one comes up with some simple mods let me know. I do not want to get to complicated, this is my introduction to electronics project.
Board:
https://sites.google.com/a/theprojectinventory.com/envertech/enver-creek-engineering/scamatics/Arduinolightdisplay.brd?attredirects=0&d=1
Schematic
https://sites.google.com/a/theprojectinventory.com/envertech/enver-creek-engineering/scamatics/Arduinolightdisplay.sch?attredirects=0&d=1
High School Engineering Teacher

graymalkin

Should you do this again, things would have been far cheaper with an 8 pin ATtiny and a shift register with 8 LEDs, setting them isn't hard with one SR, the parts are more easily (and cheaply) replaced.. Etc

Depending on the final use (driving 2 motors on a robot based on two inputs, for example) the ATTinys are ideal, and they can be programmed by an Arduino, ref ArduinoICSP. Code could even be written in the arduino IDE (with some tinkering).

That said many props for using Arduino in general, more people need to be making things involving micro controllers, if nothing else it creates a sense of appreciation for how advanced computers truly are.

nobikes

The Attiny sounds interesting especially if it can cut down on cost. We are doing a line following robot with arduino as well so the course cost a fare bit of money for the students.

Is there a good thread on using the Attiny on an Arduino Duemilanove? I am very interested in checking it out?
High School Engineering Teacher

Go Up