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31  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: April 03, 2013, 12:18:58 pm
In one diagram I see them placed between the + supply and the VCC pins

Wrong.

Quote
and another diagram put across the + & - supply lines.

Correct.

The capacitor is connected from (A)VCC to GND as close as possible to the chip.


Thats what I thought, thanks.
32  Using Arduino / Project Guidance / Re: Labeling: Have any tricks/tips for identifying your DIY PCB's pins etc.? on: April 03, 2013, 12:25:23 am
Why not print out the board layout with all the pins labelled on it?
That way you can put the unlabelled board next to the printout and see exactly what goes where.
33  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: April 03, 2013, 12:21:29 am
Even more confused. now with bypass caps.

In one diagram I see them placed between the + supply and the VCC pins, and another diagram put across the + & - supply lines.
Which one is correct?
34  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: April 02, 2013, 11:29:30 am
My pcb is a varient of the trihole pad design but has two tracks made to run under the chips as supply lines. Would it be ok to put it across these lines at one end of the chips? or should I hide them under the ic sockets as close as possible to the chips power pins.
35  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: April 01, 2013, 12:51:18 pm
?? not on here?

http://arduino.cc/en/Main/Standalone

Stupid additional question but I plan on running this of a 3.6v PSP battery (always have 2 spare in camera bag + 1 in each of my psp1001 consoles)

Am I supposed to change some component values?

Stupid question and you have permission to roll your eyes.
36  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: April 01, 2013, 12:21:00 pm
Quote
and added the bypass to the tlc5940

The processor also needs them.


Where? i haven't seen one any ware?
37  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: April 01, 2013, 07:01:39 am
I prefer DipTrace, and I've been using it for the last year for my personal projects. I know Eagle might be more powerful and has a gigantic user base, but I like DipTrace better. The free version is great and should be enough even for more advanced hobbists.

Back on topic: ditch that layout, since there are several problems with it:
- the crystal is too far from the 328
- there are sharp corners in the traces. Never, NEVER route traces with 90ยบ angles.
- there is no bypass capacitors for either chip
- it is good practice to use every space left in the board (in its signal side) for a copper pour linked to the ground net.

If you decide to go ahead and use that circuit anyway, that one is easier done with a perfboard, rather than etched. Make use you use DIP sockets, instead of soldering the chips directly to the board.

I have moved the crystal under the board and added the bypass to the tlc5940
Still playing with layout designs.
Need to order some electronics to check out part size's
38  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: April 01, 2013, 02:09:39 am

Crystal is rather far from the processor.  I believe Atmel recommends as close as possible with a ground plane.

No bypass capacitors?

I believe the TLC5940 datasheet calls for a capacitor of several microfarads across VCC and GND.


Now that I missed because I didn't see a referance for it on the sheet (still trying to understand it tbh) but the arduino prototype doesn't have one.

Codelink - still building the schematic for this  smiley-eek  smiley-cry
39  Using Arduino / Project Guidance / Re: Atmega 328 crystal location. on: April 01, 2013, 02:06:58 am
Thanks DigitalRS and Cross roads.
I was still working in single layer format!
I think I will go duel layer and add it under the mega chip.

Thanks for the interference info, that was what I was looking for.
40  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: March 31, 2013, 03:08:41 pm
Well Eagle is so unfriendly it's crap, without a ton or reading I cant even get started.
Fritzing keeps putting things in the wrong place.
Screw that where my copper clad stripboard.
41  Using Arduino / Project Guidance / Atmega 328 crystal location. on: March 31, 2013, 05:47:36 am
I'm designing very slim pcb for use with the TLC5940 (20mm wide), so far I've been working on the plan for a single layer pcb but i came across a question.

Wheres is the best place to put the crystal and route the connections?
I have 2 versions with the crystal mounted on the end.
V1 runs the crystal lines around the outside of connections from the end to the XTAL pins.
V2 runs the Crystal lines underneath the mega to the XTAL pins.

Is there a problem with interference from the crystals lines being run around the outside?
(see the attached image for the v1 pcb.
42  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: March 30, 2013, 04:19:53 pm
Quote
Using the breadboard layout on the libs google code page which has given me the working prototype.
I'm just sruggling with the conversion from arduino to minimal 328 circuit.

I can say that not using a schematic to route the PCB in Fritzing has gave me quite a few boards that are now coasters.  Designing a schematic in Fritzing is next to impossible.  Just make sure you re-recheck your routing on the PCB.  I dropped Fritzing because of it's schematic downfalls.  If you plan on making more PCBs, I would highly suggest moving to Eagle. 
Yup I noticed schematic view is hopeless that why I only use BB or PCB view.

I posted here because I don't know where else to ask to get someone to check out my wiring.
Eagle is not in the Mac apps store.
43  Topics / Product Design / Re: Atmega 328 and TLC5940 routing on: March 30, 2013, 03:46:49 pm
Is this going to be etched?  
Yes
What's the overlap in the red circle?
Another resistor goes here
Also I am assuming the 2K resistor is going on the under side of the board?
No, unless ic sockets have changed over the years It should fit in the middle of the base.
I am guessing that you don't have a schematic?
Using the breadboard layout on the libs google code page which has given me the working prototype.
I'm just sruggling with the conversion from arduino to minimal 328 circuit.
44  Topics / Product Design / Atmega 328 and TLC5940 routing on: March 30, 2013, 01:16:14 pm
I'm trying to build a barebones pcb layout just to drive the tlc5940 (standard pin layout.)\
Im going to have to run a few jumpers for some of the wires but have I connected what I've done so far correct?
45  Using Arduino / LEDs and Multiplexing / Re: TLC 5940 Max current sink. on: March 30, 2013, 06:49:07 am
I am planning on running this on a 3.6V circuit and my prototype scrolls through 15 20mA led's.
Will this chip be able to handle running 4 led's on each pin? (80mA?) while (on rare occasion) fade all 60?

The datasheet says:

60 mA (VCC < 3.6 V)
120 mA (VCC > 3.6 V

It doesn't say what happens when VCC=3.6V but 80mA is right in the middle...

You're planning on having the chip dissipate about 0.5V per channel (3.6 minus 3.1). 0.5V*80mA*16 channels=640mW. That's well within the limits for power dissipation.

You should be fine.

Thanks fungus
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