Azteeg X3 3DP Controller - Single board RAMPS

Hi All,

I have been working for a few weeks on my first Prusa and at the same time I am also working on several electronic projects in support of the 3D printer I am about to finish(soon I hope). Since my friends and I are building several printers we decided to design a single board version of the RAMPS to basically lower the cost plus add some stuff that we think might be useful, but for the first design it is pin to pin compatible with the RAMPS except that's its just a single board.

Before I start describing the Azteeg 1280 3DP I would like to introduce myself first, My name is Roy, Im a maker like everybody else and intensely interested in 3D printing since Im a mechanical engineer by day. I am also an electronic enthusiast like some of you and a believer in open-source hardware. Im based in Irvine CA.

Azteeg 1280 3DP is based on the RAMPS and Arduino Mega designs. It sports the ATMEL ATmega 1280 running at 16Mhz and FDTI FT232RL USB chip.

Features:

ATmega 1280 micro processor
FDTI USB TTL chip
500ma Switching Power supply (VinMAX = 30V)
Larger Terminal Block for single power input
Lower RDSon N-Mosfets
Higher Gate drive for H-Bed mosfet
Reverse Polarity protection (experimental)
Can accept separate Vmot up to 30V(experimental)
Manual selector for USB power
Separate SDRAMPS / uSDCarrier connector
Single ATC fuse (Comes with 5A and 20A fuse)
Expansion port for future peripherals


Other than listed, everything else is the same with the Arduino + RAMPS. I have 10 PCBs made and will receive the rest of the parts this week so I will start assembly as soon as possible. Most of the parts are surface mounts to ease in manufacturing and lower cost. I have a website but not much in there except for current sensors, when I get the Azteeg 1280 3DP page up I will post it here.

I will update this post if there's anything new. I attached top and bottom 3D rendering of the PCB in DipTrace PCB software (sorry not an Eagle fan).

Pricing? I have an idea already but will hold on until everything is accounted for.

Dimensions: 3.9" x 2.7" 2 layer board( not much bigger than the RAMPS+Arduino MEGA)

The schematic is still a mess and will post it once development is well underway. Its not much different from the RAMPS + Atmega 1280.

Let me know if you have questions, comments or suggestions.

Thanks for looking

royco

############ UPDATES ############

11/5/2011 - Some of the parts arrived and I soldered them so I can try the Mosfets. The H-bed mosfet seems to be ok with the copper pours as heatsink. Temp is at 52C at 11 amps for 1 Hr. Vgs drive is 12v. The metal parts on the terminal block and wires seem to help in dissipation. So far it looks ok but I think i'll be taking up on brnrd's heatsink idea for better reliability. I also tried a logic level drive and its a no go for the H-Bed Mosfet, can only go up to 8Amps with the small copper pour under the it. At 10amps with logic level drive it wants to go into thermal runaway with just a few minutes. At 12Amps it quickly gave its last puff, so the higher Vgs drive is here to stay.

Edited 3 time(s). Last edit at 03/04/2012 06:08PM by royco.

A few things:
1. I like the idea/initiative
2. This has way too many surface mounts (more than 0) for a public board.
3. Not sure a second set of end stops is necessary. And I would try to keep all connections on the edge of the board. Enclosures will depend on it. Maybe move the expansion port to where the endstops are?
4. That surface mount on the back side of the board will be a bitch if you are doing solder reflow. Maybe swap that one for a pin thru?
5. Is the board grounded at the screw mount holes? If so, a little ring around the hole will help conduct.
6. I may have completely missed them, I was looking for your MOSFET placement? Anway, make sure you can mount/get to MOSFETs (and have room for heat sinks if people want them)
7. Torn between saying put the z axis on one driver, and use the 5th pololu for a second extruder. Either way, maybe keep movement axis together on the mask? So like (Y, X, Z1, Z2, Extr.) instead of (Y,X,Ext,Z1,....Z2)

Also, what are you you looking at for pricing?

Each of the driver boards needs ~ 2 amps.

I would keep the ftdi chip apart, so ppls could use what they want / have, e.g. maybe 8U2

In extremis i would check about how much complication would be to add some header space (even if unequipped by default), or a shield header format, for purpose to hack into the pins directly, like motherboard12 headers, that are placed all around the mcu instead of having the expansion slot. I like those headers but now to be honest i never used them so still dunno how usefull would really be in practice. Maybe if you go one more mile with this, and copy a arduino shield layout in a standard arduino format for whole board, then it will be quite something extraordinaire, and then maybe has a chance to get adopted by some distributors and in time could turn into a better product. But then again i'd rather use another mcu for the purpose of something like that, maybe the new stuff.

Also in extremis i would have provisional space for a 3rd temperature reading and perhaps even a 4th fet, both even if just wont be equipped by default.

Mosfets - and this is probably the only important thingy.
I would also use exact same type of mosfet for all of them (same snubbers also), basically that is because one gets burned, ppls turn to any of the other as replacement, so if HB fet burns out, someone will try use the others, and if those are lesser, then would probably end up burning all fets one by one. Ppls will always think that if it looks same, then it has to work the same so unless HB fet is not visually significantly different, then all have to be same type exactly.
In some thread back someone posted having an issue with small spikes / transients across mosfets. Maybe something to deal with that, e.g. small blind / generic overpowered r-c snubber perhaps, should be most welcome. Also i would rather use to-220 fets, because i think they are easier to sink if there is a little free area.

Edited 1 time(s). Last edit at 11/01/2011 11:41AM by NoobMan.

Since he looks to be using mostly SMD, I don't know if a breakout board for FTDI is really necessary. Sanguinololu might be a better board for a breakout FTDI, since it is the only SMD device in the design. I do prefer breakout smd boards, but if you're already doing 30 SMD connections, one chip shouldn't be a problem.

marnargulus,

Thanks for your comments. Highly appreciated. My answers in red.


marnargulus Wrote:
-------------------------------------------------------
> A few things:
> 1. I like the idea/initiative
Thanks!

> 2. This has way too many surface mounts (more
> than 0) for a public board.
Yes, too many for DIY(that 100pin Atmega chip may be a challenge for some). My original intention is to have the board assembled professionally similar to the GEN6, this way it could drive the cost down and would be perfect for those who just needs an assembled controller.

> 3. Not sure a second set of end stops is
> necessary. And I would try to keep all
> connections on the edge of the board. Enclosures
> will depend on it. Maybe move the expansion port
> to where the endstops are?
The # of endstops where lifted from the RAMPS and originally they where placed on the edge but was moved to where it is now to avoid going to a 4 layer PCB. I was also concerned about enclosures but we'll see if the trade off is worth it.

> 4. That surface mount on the back side of the
> board will be a bitch if you are doing solder
> reflow. Maybe swap that one for a pin thru?
Its a solder jumper selector, the original RAMPS seem to use up all the interrupt pins so the jumper selector is used to swap the Z- endstop with another digital pin. I needed the interrupt pin for the LCD interface I was designing for this controller.

> 5. Is the board grounded at the screw mount
> holes? If so, a little ring around the hole will
> help conduct.
The circuit is not grounded but the USB connector casing will be.

> 6. I may have completely missed them, I was
> looking for your MOSFET placement? Anway, make
> sure you can mount/get to MOSFETs (and have room
> for heat sinks if people want them)
The Mosfets are those square pads on the lower left corner of the board labeled Q1 Q2 Q3, if my calculations are correct they wont need a heat sink aside from the extra copper pours they have. Power dissipation would be around 0.6 watt for the H-Bed, would be warm to the touch I would assume but should be nothing to the Mosfet( will soak up with a constant on electronic load to confirm that)


> 7. Torn between saying put the z axis on one
> driver, and use the 5th pololu for a second
> extruder. Either way, maybe keep movement axis
> together on the mask? So like (Y, X, Z1, Z2,
> Extr.) instead of (Y,X,Ext,Z1,....Z2)
The Z1 and Z2 shares a controller, I tried to get the Z next to the Y but I chose the easy way out again because its an easier layout.

Edited 2 time(s). Last edit at 11/01/2011 12:13PM by royco.

If you use the USB housing for ground, but someone uses SD cards, if they remove the USB how will it be grounded? Best practices would be a common ground.

marnargulus - what I meant was the USB connector chassis will be grounded together with the pads on the screw holes and would be a good idea to tie it to one point on the circuit ground.

Noobman - Nice Ideas. Thanks. The Mosfets are the same for all three and are logic level, but I added a full on drive for the H-Bed to get the lowest RDSon possible. I'll put it under the scope and see what are the spikes like. My original choice was a Dpak but opted for something smaller, might be hard to replace if needed but my goal is to have it designed right that it would just keep churning along for a long time under normal conditions.

Quote
royco
The Mosfets are those square pads on the lower left corner of the board labeled Q1 Q2 Q3, if my calculations are correct they wont need a heat sink aside from the extra copper pours they have. Power dissipation would be around 0.6 watt for the H-Bed, would be warm to the touch I would assume but should be nothing to the Mosfet( will soak up with a constant on electronic load to confirm that)

My experience with RAMPS is that you do need heatsinks on the MOSFET for the heated bed if you want to use it for ABS. I suppose if you use higher than 12 V for the heated bed, you might be able to get away without a heatsink. But for 12V, you need them.

Posted an update for those interested. See original post.

Love the idea, especially the 2 Z-Axis outputs.

Just a thought, wouldn't it be wise to move LED 2 to 4.
They look like they are almost directly beneath the wires. This would make them hard to see and potentially lead to them being shorted by a lose wire.

---

My Reprap blog

jds-reprap.blogspot.com

Why not include the SD or microSD socket in the design so there won't be a need for a daughter card?

JoeDaStudd,

Yeah, found about the LEDs when I built one up, cant see much of them with a #12 wire in there. Moved them on the new revision.

brndr,

I was on the fence on that one since I also made a microSD card adapter based on Adafruit's design. I initially laid out a board with it but didnt went that direction with this proto i have. I was thinking that in case users break these flimsy sockets they can just replace the adapter boards instead of trying to de-solder it.

Im finishing up on the new rev, will be changing the Mosfets out and include drivers for each + heatsinks, replaced the optional servo pinouts with switched mosfet output for anything to fans, LEDs, servos, solenoids up to 1 Amp.

I'm putting together a Prusa Mendel. I've been looking at both RAMPS and Sanguinololu. But I think I'll leave the electronics for last and see how this Azteeg goes.

I am very interested in this design -- I've been thinking of doing the same thing myself. I have a lot of experience soldering fine-pitched SMT parts -- is there any chance I could get a copy of the PCB design? I will be happy to report back on my progress.

-Eric