Author Topic: homemade axon "compatable" board UPDATE preliminary PCB design (Read 17007 times)

SmAsH · « **Reply #30 on:** June 06, 2009, 06:42:26 PM »

Quote from: sonictj on June 06, 2009, 05:43:13 PM

I did pick up eight 8x8 led matrixes. I only ordered four but eight showed up lol.

my god... why does this never happen to me!
i cant wait for pics of the matrix... make up a picture of you dp...

sonictj · « **Reply #31 on:** June 06, 2009, 06:56:51 PM »

I'm in the process of fixing my laptop so it may be a while.

sonictj · « **Reply #32 on:** June 25, 2009, 08:56:11 AM »

I just made what I think is my final revision of my PCB design.

Features
* Dimensions are 2.05x3.05".
* The board has a 5 amp 5v regulator the PCB supports up to 3amps (diode limit)
* uart0 is broken out for connection to a ftdi 232 usb cable (does not power board)
* DC barrel jack 2.1x5.5mm
* I expect the voltage input to be 7.2-12V (the datasheet was a tad uninformative)
* Arduino compatible, and should also be axon compatible
* All i/o are available and spaced in .1" increments. Also all components are short enough so that a protoboard/shield can be placed on top.
* special pins: Reset, Aref, 2x 5V, 2x gnd, VIN
* Current limiting ptc polyfuse connected to the microcontroller +5V bus to "prevent" failure via short circuits.
* reverse polarity protection diode

I would like feedback on how you like or do not like the design. Is there anything you would want/add? Any input on a diode in a small package that can withstand 5+ amps and 12-15V. I could only find up to 3A.

PDF is attached

Admin · « **Reply #33 on:** June 26, 2009, 12:21:29 PM »

Quote

Current limiting ptc polyfuse connected to the microcontroller +5V bus to "prevent" failure via short circuits.

Then how would you know if you accidentally shorted something?

Quote

Any input on a diode in a small package that can withstand 5+ amps and 12-15V. I could only find up to 3A.

Multiple diodes in parallel

sonictj · « **Reply #34 on:** June 26, 2009, 01:09:35 PM »

Quote

Quote
Current limiting ptc polyfuse connected to the microcontroller +5V bus to "prevent" failure via short circuits.
Then how would you know if you accidentally shorted something?

The power led was also connected through the polyfuse. I say "was" because I've decided to cut it from the design.

I'm looking into designing the board with a built in USB level shifter (ftdi chip). Also how desirable is it to have the ability to power via usb? In my opinion its nice but not necessary. I will be able to avoid incorporating a toggle switch and a PTC fuse if I go without a USB power option.

SmAsH · « **Reply #35 on:** June 26, 2009, 03:18:06 PM »

Quote from: sonictj on June 26, 2009, 01:09:35 PM

I will be able to avoid incorporating a toggle switch and a PTC fuse if I go without a USB power option.

why not jumpers like arduino?

sonictj · « **Reply #36 on:** June 26, 2009, 03:56:49 PM »

jumpers can't handle the current. The jumpers may be able to do 3amps, but I would like a reasonable factor of safety.

SmAsH · « **Reply #37 on:** June 26, 2009, 04:21:09 PM »

ahh i see, but isn't a toggle very big and clunky to have on a board?

sonictj · « **Reply #38 on:** June 26, 2009, 05:05:20 PM »

absolutely, that is why I said

Quote

I will be able to avoid incorporating a toggle switch and a PTC fuse if I go without a USB power option.

I want to make board ~2x3" and a toggle switch will make that difficult.

Admin · « **Reply #39 on:** June 26, 2009, 08:15:11 PM »

Quote

Also how desirable is it to have the ability to power via usb? In my opinion its nice but not necessary.

A bootloader won't won't if you can't power from USB. You need to keep USB turned on while the mcu power cycles for a bootloader (through USB) to work.

I learned that the hard way on a prototype Axon

sonictj · « **Reply #40 on:** June 27, 2009, 01:31:47 AM »

Quote

Quote
Also how desirable is it to have the ability to power via usb? In my opinion its nice but not necessary.
A bootloader won't won't if you can't power from USB. You need to keep USB turned on while the mcu power cycles for a bootloader (through USB) to work.

I learned that the hard way on a prototype Axon Tongue

I don't understand how that could be true the arduino runs via bootloader yet you can power it exclusively via the on board power jack. When you say power cycles couldn't you just have the watchdog timer trigger a reset? The arduino uses the dtr line of the ftdi chip to trigger a reset. I believe a null character is sent to from the host computer to toggle dtr. The dtr line is connected to the reset line of the atmega168 through a .1uf cap for auto-reseting.

Also I'm wondering about a few things. what is the general guideline for how far away a trace should be from the outside edge of a pcb? Two I'm planning on saving space by putting the ftdi chip on the bottom of the board. Is there any reason this may be a bad idea? I don't see a ton of two layer microcontroller boards with ics on both sides.

The way the design is going I think the board will be under 2x3" with support for micro usb, just not power via usb.

Admin · « **Reply #41 on:** June 27, 2009, 06:39:02 AM »

Quote

I don't understand how that could be true the arduino runs via bootloader yet you can power it exclusively via the on board power jack.

So when you have the Arduino 100% unplugged from power, and you plug in USB, does your PC recognize the Arduino? Unless its taking power from somewhere, your computer can't see the connection.

So when it does get power, it takes a few seconds for your computer to detect the new hardware, missing the bootloader time window.

And yea, you can do a watchdog reset. But you'll have to dedicate a button to that (not that you don't already have more than enough pins!).

Quote

what is the general guideline for how far away a trace should be from the outside edge of a pcb?

Depends on manufacturer and the process they use. I usually leave ~2mm at least.

edit: fixed typo

SmAsH · « **Reply #42 on:** June 27, 2009, 07:36:44 AM »

Quote

So when you have the Arduino 100% unplugged from power, and you plug in USB, does your PC recognize the PC? Unless its taking power from somewhere, your computer can't see the connection.

when you use the bootloader on the arduino i always have to have my pc supplying power otherwise my pc comes up with the "usb device not recognized" message, weird?

sonictj · « **Reply #43 on:** June 27, 2009, 11:15:25 AM »

Quote

So when you have the Arduino 100% unplugged from power, and you plug in USB, does your PC recognize the Arduino? Unless its taking power from somewhere, your computer can't see the connection.

I program my arduinos all the time with the external power being used rather than usb. The pc recognizes everything just fine.

**update I just confirmed this by connecting my arduino to my brand new pc. No power was coming through USB yet the device was recognized and I was able to send a program to the board.

Admin · « **Reply #44 on:** June 27, 2009, 04:26:08 PM »

This is because the USB was getting power from the plug. I haven't used the Arduino, and too lazy to look up the schematic, but I promise you they are keeping it always powered when you power cycle the ATmega.

sonictj · « **Reply #45 on:** June 27, 2009, 05:08:46 PM »

Quote

This is because the USB was getting power from the plug. I haven't used the Arduino, and too lazy to look up the schematic, but I promise you they are keeping it always powered when you power cycle the ATmega.

When you say USB are you talking about the ftdi chip being powered all the time ? If that is what you meant then I'm in total agreement. The arduinos all have a 3 pin power select header with the center pin being 5V. This connection powers the atmega and the ftdi chip the whole time. I think we misunderstood one another

.

I just bread boarded the schematic I made for the ftdi and successfully programmed via bootloader so everything is peachy

. I'll post my ftdi chip schematic in a few minutes just in case your interested.

sonictj · « **Reply #46 on:** June 27, 2009, 05:28:43 PM »

Here is the schematic for the ftdi chip USB level shifter.

Admin · « **Reply #47 on:** June 27, 2009, 05:41:50 PM »

Quote from: sonictj on June 27, 2009, 05:08:46 PM

When you say USB are you talking about the ftdi chip being powered all the time ? If that is what you meant then I'm in total agreement. The arduinos all have a 3 pin power select header with the center pin being 5V. This connection powers the atmega and the ftdi chip the whole time. I think we misunderstood one another .

haha yea, i meant ftdi chip (or CP2102, if you were using that instead). total agreement.

sonictj · « **Reply #48 on:** June 27, 2009, 06:15:53 PM »

I've sent out for the parts now. Here is a pdf of the current board. I may tweak a few things before I send out for the PCB. I wanted the parts in hand to confirm measurements etc.. I'm very excited this is my fist PCB I've ever made.

possible issues:

1) I'm not sure what pin 4 of the micro usb connector should be connected to. I think that its only used for determining USB A via a ground signal. I looked at the axon schematic and it had pin 4 and 5 grounded.

2) I haven't looked yet to see if I have enough clearance for an ISP connector. Anyone know where I can get the mechanical specs to check?

If you see anything out of the ordinary let me know.

sonictj · « **Reply #49 on:** July 01, 2009, 09:02:43 PM »

I sent my PCB design to Advanced Circuits today. I guess in a week I'll be able to see how the design came out.

Features

* 2.3"wide by 3" long
* access to ALL 86 i/o
*axon compatible
*.1" protoboard spacing on all i/o for simple shields
* USB boot loader support via a micro usb connector (arduino mega)
* 3amps of 5V and ~3amps unregulated
*basically all features of the atmega640/1280/2560 family.

jamort · « **Reply #50 on:** July 01, 2009, 10:24:39 PM »

you planning on selling this at completion and if so how much?

sonictj · « **Reply #51 on:** July 01, 2009, 10:54:15 PM »

I'm very seriously considering it, but I have to make sure the design is sound first

. I also want to make sure I will not be upsetting Admin. I would not want to advertise on Admin's forum without permission. Especially for a product that would be competitive with one of his own.

jamort · « **Reply #52 on:** July 01, 2009, 11:12:10 PM »

yeah i know the feeling.... If the decision isnt sound it probably ownt need but small tweaks.... I'm considering to start a motor driver and sensor product line but still havent decided

SmAsH · « **Reply #53 on:** July 02, 2009, 12:33:52 AM »

if this became a product i would probably buy it too

jamort · « **Reply #54 on:** July 02, 2009, 01:18:37 AM »

depends on price to though... I mean i kno the stuff i would need to build it but i think it might be worth 50-80$ to avoid all that soldering

sonictj · « **Reply #55 on:** July 02, 2009, 02:14:52 AM »

Quote

depends on price to though... I mean i kno the stuff i would need to build it but i think it might be worth 50-80$ to avoid all that soldering

That's within the price range I'm considering. It all depends on how the board performs,and what quantities I purchase PCBs in. My plan for "if" I do sell the board, is to build small quantities myself for sale. So the only costs out of my pocket would be parts and PCBs.

As a side note, I'm curious how easy it is to go about selling something over the internet. I don't really have a grasp of what is involved. I've never done it before.

SmAsH · « **Reply #56 on:** July 02, 2009, 03:55:06 AM »

Quote from: sonictj on July 02, 2009, 02:14:52 AM

As a side note, I'm curious how easy it is to go about selling something over the internet. I don't really have a grasp of what is involved. I've never done it before.

well, you advertise your product, the consumer sees the add or hears about your product, they submit an order for one, you receive the order and send out an invoice.
they pay, you ship it. basic but thats the bare bones of it.

kpmcgurk · « **Reply #57 on:** July 02, 2009, 04:47:23 AM »

I think what he is talking about is taxes/laws and such... but I am not 100% sure

SmAsH · « **Reply #58 on:** July 02, 2009, 05:15:43 AM »

ahh, but if its not too much of a commercial product (imagine soldering a few hundred of them) it shouldn't be too different from selling on ebay should it? although, if there is anything about ROHS and lead then maybe...

sonictj · « **Reply #59 on:** July 02, 2009, 10:05:26 AM »

There is a lot of legailty which is what I was referring to. I would have to set up a website, and credit card checkout system. I also would have to pay $50 to license eagle. ~~There is also the possibility of needing a small business license, but I don't know if that is necessary.~~ **Update A home based business license is required** stupid legal crap

.

Smash is Australia a ROHS compliant countriy ie. can you buy something that may contain lead?

EDIT: my design is now 100% ROHS compliant so no worries.

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Author Topic: homemade axon "compatable" board *UPDATE* preliminary PCB design (Read 17007 times)

Author Topic: homemade axon "compatable" board UPDATE preliminary PCB design (Read 17007 times)