Motherboard Shield thoughts

I have been thinking about designing a Motherboard 1.2 into a shield for the Arduino-Arduino Mega platform.

Some thoughts I have on this is.

1. the board is to work on a Arduino (I have found this will require the stepper pins to be moved a little.)

2. the board is to have rs485 I2c

3. The board is to be mostly tru. hole to ease in the building of the board.

4. The Board will be be able to work on a Arduino Mega also and things like SD card slot will be on the Arduino Mega.



5. An other thought was to Design a Sanguino that uses the same foot print as the Arduino Mega just a little bit smaller since the Sanguino does not have the same amount of pins.

I would also like to add some more diagnostic leds and make this so that somebody can expand with the electronics.

I want to do this also for the Extruder Controller and make it work a little bit better with a stepper.

Any ideas and anybody want to help please join in.

I think the next step is to list the pins and features under each controller type.

IE Arduino/ steppers and 485 comms

Sanguino/ same as Arduino but more Stepper control, added comm type, and SD card support.

Arduino Mega/ ??


Thanks Bruce Wattendorf

Don't be too quick to dismiss SMT assembly. I just built the through hole version of the stepper controller v1.2 With the LM297/298 and the Gen 3 motherboard (also labled v1.2) I completed the motherboard in a fraction of the time it took to make the stepper board.

The stepper board has been the first through hole project I have built in a number of years. It was actually more difficult than the SMT version. Reworking SMT is also a lot easier as one can use a heat gun to remove components quickly. Often the removed component can be re-used. With through hole once the parts are in place, they stay there. It is next to impossible to rework a through hole board.

Even making boards, Surface mount has advantage. A lot less holes to drill. If one places the vias away from under the chip, then it is only a matter of soldering in a wire here and there.



The motherboard v1.2 uses exactly the same footprint pins as a Sanquino. In effect this board is a shield for the latter.

With the existing designs, there are not enough pins on the Arduino to drive all the steppers and com channels. The chip used on the Sanquino has a second serial port which is used for Rs485.

I have not looked at which chip the Arduino Mega is using, Undoubtedly this has more than 64 pins.

The real issue currently with the electronics are not the designs, but the availability or accessibility to others. Currently most of the designs are in Eagle Layout editor, which is not an open source program. The free version is quite accessible, and runs on all the popular OS systems. This outputs the industry standard Gerber which is the same as the G code reprap uses.

The downside to Gerber is the strength that there are a lot of choices as to who can make the board. This is a competitive business with the manufactures looking to volume. This makes ordering one to 5 boards cost prohibitive.

There is a service I have been using for 10 years, expressPCB. Unlike Eagle one has to use there format for the layouts. This is also a free program and has no restrictions to size. ExpressPCB will also sell the Gerbers should one want to go to volume production. I have no interest in this company other than as a somewhat satisfied user for more than 10 years. That is a long time in this business.

With expressPCB one does not have to worry about drill files and other design files which are used for accounting practice. One sends the board through a secure program (Which unfortunately requires windows) A week later the board arrives.

This option is probably more what is needed, a way to distribute more of the stable electronics, than some of the research projects discussed here.

What this project really needs is someone to make more kit packages to second source those makerbot sells.


-julie

Bruce Wattendorf Wrote:
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> I have been thinking about designing a Motherboard
> 1.2 into a shield for the Arduino-Arduino Mega
> platform.
>

You might be interested in my Seeeduino Shield:

[bothacker.com]

-Tim

Sheep-

I do agree with you on SMT, But I am looking at how easy it is to get the parts and I feel a lot of users might be intimidated by SMT and cause them to not build the electronics.

As far as the Sanguino foot print that is great but try to move the electronics to the Arduino Mega.

As far as the availability yes it is an issue but it is also an issue in my eys that the present Electronics does not fit very well on a Reprap Mendel.

And as far as not being enough pins there is enough if you do not run the end stops (which I want to be able to have but on pins that would be on the Arduino- Mega..

So if somebody wants to run with just an Arduino they can with limited features.

The other pin is the enable pin it does not have to be used or it can be all the same pin.


Bothacker-

That was very close to what I was talking about. 2 things I see is the SD slot and maybe I2C?


Bruce Wattendorf-

Tim

Is your seeeduino shield available to buy>?

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Regards

Ian