New printer electronics: Megatronics

The last few month I have been working on a new type of electronics. I like the power of the RAMPS board, but I think it has reached it's limits because of the limitations on the design.

So I have combined RAMPS, Arduino Mega 2560 and SD RAMPS into a single board solution (+/-125x115mm). More information will follow soon. For now here is a vid of the first test print with a prototype board:

[www.youtube.com]

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

Looks pretty nice. I like that you kept the socketed stepper motor drivers instead of integrating them into the board. How many driver sockets are there? Are there any other improvements over RAMPS, such as additional MOSFETS? It's a bit hard to tell from the video.

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For the final 1.0 version I plan
4x MOSFET: 3x 120A and 1x 340A
5 stepper driver sockets are already included

There are many other improvements. I will publish them later on [reprap.org].

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

brupje Wrote:
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> For the final 1.0 version I plan
> 4x MOSFET: 3x 120A and 1x 340A
> 5 stepper driver sockets are already included
>
> There are many other improvements. I will publish
> them later on [reprap.org].

Sounds good.

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Mogge

Any plans to extend the keyboard and display to this setup ?
And uhhh. WOW !!!

Ed

Thanks

There is a connector for the keypad and a LCD screen on board.

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

340A?

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[www.hydraraptor.blogspot.com]

353A actually, IRF1324PBF for the heated bed. The MOSFET will stay nice and cool. My Fuse is getting hotter than the MOSFET actually. I wonder if the 11A fuses have much benefit anyway.

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

This is extremely exciting. Very well done. At the moment there's always a compromise. If this goes mainstream it should level the playing field and let everyone have the opportunity to work with all the addons they choose to without having to find the limitations in their board and upgrade. You can put me down for a couple of preorders!!

Only thing I can think of is perhaps a pc fan header so people can plug and play with off the shelf fans for the chassis / board. The extra mosfet means you can already have an extruder fan and an extra extruder at the same time. Reckon you could squeeze in 5 servos? I had a thought about a servo based bed leveller in another thread on rams, this would mean you could do a three point bed leveller using nopheads genius z probe and have a spare for filament wipe etc

Gold medal effort!

353A is crazy. Even the datasheet seems to suggest the package limits it to 195A.

Anyway it is not a logic drive FET, so gets barely turned on from a logic pin. If you get a worst case specimen it will only pass 250uA with 4V. The best case threashold is 2V, so some if not most will work but like most reprap electronics, some people will be unlucky and get one that fries.

Either boost the gate drive to 10V, or use a FET designed for logic drive, or take a chance it will fail.

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[www.hydraraptor.blogspot.com]

@andy-net Thanks. I will see what i ca@n do for v1.1

@nophead i did test it and works, but i get your point. Any suggestion on a better FET is appreciated. I can change that easily now. Important thing is to keep it cool.

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

[www.fairchildsemi.com] is a logic drive FET used on Melzi.

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[www.hydraraptor.blogspot.com]

I use the IRLB8743 [www.irf.com] for my heated print bed, which should carry more than enough current at logic levels.

-Rob A>

Thanks to Nophead for helping me with the MOSFET's, I changed the MOSFET's for the final v1.0 board to 150A ones. I tested them with my heated bed PCB and they are holding up fine. They will get hot, but nothing exceptional.

I also have created a datasheet [reprapworld.com] (7.6M, source files will be posted as soon as I have time to clean op the schematic

All my tests have been good so far, no showstoppers, so I think we are good to go Sales price will be €59,99 excluding stepper drivers. I expect the board will be available 30th of september. Pre-ordering will be available later this week.

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

Now available for pre-order: [reprapworld.com]

With a little early bird discount

Edit: and I worked on the Wiki a bit [reprap.org]

Edited 1 time(s). Last edit at 08/14/2012 04:39PM by brupje.

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

I finally come around cleaning and uploading the schematics.

[reprap.org]

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

Just preordered a couple can't wait to have a play!

Another, sometimes overlooked consideration with driving FETs is the input gate capacitance/input charge. The first thing to consider is the gate threshold level but also good to think about the capacitance. The good news is that the Arduino PWM rate is very slow for things electronic...something like 540 Hertz. The concern is that this capacitance slows down the rise and fall times of the gate signal. During these transition periods, the FET transitions through a linear region as opposed to snapping instantly on and off. In the linear region, you have current flow *and* voltage drop across the FET and that equals power dissipation. The moral of the story...another consideration and why an over sized FET may have huge current carrying capacity but also very big input capacitance and therefore requires a beefier drive circuit to charge and drain the capacitance. BIgger may not always be better (or cooler).

This looks fantastic, definitely keeping in mind for my next build

what was the cad software was used to design the electronics?

It was created with DesignSpark. It's a freeware program.

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

yeah, I was anxious and I was looking through wordpad (given enough work) but found nonetheless thanks and congratulations for the work was very good ...

Boards are available now. Shipment starts Monday, but it may take a few days to catch up wil the pre-orders though.

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

Here is a vid of the Megatronics posted on youtube:

[www.youtube.com]

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

Megatronics support has been added to the official Marlin repository, so you can run now the latest Marlin easily with Megatronics.

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19

I have added some information to the wiki [reprap.org]

- Fix for problems when uploading firmware in Windows
- Basic setup layout
- Dual extruder setup layout

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reprapworld.com
PLA, ABS, PETG multiple colors (3 and 1.75 mm) €16,49 / kg
Megatronics 3.0 €79.99 / Minitronics €37,19