Gen 7 electronics questions

Just had a few questions about the generation 7 electronics. I can't decide between gen 7 and RAMPS. From my understanding gen 7 is just ramps on a single board with less components.

How many people are running the gen 7? Are there any problems or quirks I should be aware of? stable firmware, etc?

Unless there's a place I can purchase a board, I'm planning on etching it myself. Opinions?

I'm just doing a couple Gen7 boards myself. I like it because you don't have to buy an arduino and a shield, just an atmega 644. I don't have it running yet, but it sounds like the initial testers have used it with success. It could use auxiliary power connections for heated bed, but overall it seems like a promising project. Still pretty new though, so if you want a mature electronics solution, RAMPS is better.

BTW, you might want to check out sanguinololu too. It is a single board solution too, has two power connectors, is double sided/small board with integrated FTDI usb to serial chip. I think there are some guys getting ready to sell boards, or you can have some made. It is a lot like gen7 but built for commercial board manufacture instead of DIY board etch/route.

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From my understanding gen 7 is just ramps on a single board with less components.

That is one of the two main development goals. The other one is replicatability, you can manufacture the PCB on your RepRap. Either by PCB milling, or by etch-resistant drawing + etching. Industrial processes work too, of course.

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How many people are running the gen 7?

Currently I know about four running Gen7. At least one additional board is manufactured each day, so this number should raise soon.

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Are there any problems or quirks I should be aware of? stable firmware, etc?

As Bryan said, driving a heated bed directly from the board is currently not possible because connectors don't match the required currents. Gen3 or RAMPS can't do that either, so it's not really a penalty.

Firmware is the same as for RAMPS (Teacup, FiveD), just a different pinout. Since last week there's even a bootloader made for 20 MHz, so there's no reason not to use this 25% speed increase.

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Unless there's a place I can purchase a board, I'm planning on etching it myself.

If you research new sources for the electronic components, please add them to the tables in the Wiki. If you're lazy, I can send you kits

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

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Firmware is the same as for RAMPS (Teacup, FiveD), just a different pinout. Since last week there's even a bootloader made for 20 MHz, so there's no reason not to use this 25% speed increase.

That cleared up a lot of confusion for me. The main reason why I wouldn't want to make the gen7 electronics is because the whole "bootloader" thing intimidates me. I've made a few sketches on my arduino duemilanove, so I understand the firmware part. I just need the chip and a programmer to install (Is that the right term?) the bootloader, right?

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If you research new sources for the electronic components, please add them to the tables in the Wiki. If you're lazy, I can send you kits

I'll be sure to do that. Thanks for the offer, but I can find someplace. Chances are my technology teacher has most/all the components needed besides the ATmega and programmer. I'm not new to electronics at all; I've never really done much with microcontrollers before and I really, really don't want to mess up my first attempt.

So the programmer is for the bootloader, is the "USB to TTL cable or USB to TTL breakout board" to actually program the firmware/send files to the printer to be printed?

Just ordered the pololu stepper drivers

EDIT: Now that I'm looking for places to buy the ATmega 644, I've noticed there are two kinds: ATmega 644-20PU and 644-20AU. Is there any difference/which should I get?

Edited 1 time(s). Last edit at 04/01/2011 11:02AM by Cain.

Cain Wrote:
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> EDIT: Now that I'm looking for places to buy the
> ATmega 644, I've noticed there are two kinds:
> ATmega 644-20PU and 644-20AU. Is there any
> difference/which should I get?

The 20 is the maximum speed (MHz), the letter is the package type (P=PDIP, A=TQFP, M=VQFN); Gen7 uses a -20PU.

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I just need the chip and a programmer to install (Is that the right term?) the bootloader, right?

Plus a/the board to connect these two.

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So the programmer is for the bootloader, is the "USB to TTL cable or USB to TTL breakout board" to actually program the firmware/send files to the printer to be printed?

You can upload the firmware with the programmer, too, but communication between firmware and host software ( = sending G-Code files) requires this USB to TTL thing.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Alright, so I'm getting together the materials to etch my own gen7 PCB, along with the components and stepper drivers.

I know the gen7 electronics call for the pololu a4983 stepper driver, but the a4988 will work too, correct? the pololu website claims it is a drop in replacement, only difference being overcurrent protection and "an internal 100k pull-down on the MS1 microstep selection pin". Will this (The a4988) work fine or do I need to make any changes?

Since I am going to etch the board myself, I'm going to attempt to use the toner transfer method. Can I just print "Gen7Board Layout.pdf" and use the "front (mirrored)" view to transfer to the copper-clad board? Also, the "front (mirrored)" view on the .pdf is placed twice, one in the first few pages and one in the last few. I can't see any difference other than one is black and one is light-black. Which should I use for the toner-transfer?

Edited 1 time(s). Last edit at 04/05/2011 04:15PM by Cain.

I hadn't seen the Pololu a4988 breakout before, it's a new product. It'll work fine though.

And it requires fewer external components. MS1 floats on the a4983 if it's not connected to anything. Not that we'd do that, as we'll be wanting some form of microstepping. I wish it has a pull up instead of a pull down. With pull down, you have a choice of full step or quarter step. If it had a pull up instead, you could choose from half, eigth, or sixteenth without having to hook anything to MS1. Oh well.

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I'm building it with Baling Wire

Wait, so this means I need to add components to be able to have microstepping?

EDIT: I guess I mean to ask, do/what do I need to change from the standard gen7 board, if anything, to have microstepping on the a4988.

I'll be etching the board in a few hours now, thanks for all the help. Definitely couldn't have gotten this far without you guys.

Edited 1 time(s). Last edit at 04/05/2011 05:01PM by Cain.

No you don't have to add anything to the Gen7 Board it already has a pull up wired to that pin. It just means that the Gen7 board can't be simplified by taking advantage of the built in pull down (wish it were pull up) resistor. Also Ben Jackson did a couple mods to the board to make it TT easier, (teardrop pads, small holes) ben.com/misc/gen7board.pdf and ben.com/misc/gen7board.pcb.

Bryan

Got a question of my own now. What are the requirements for replacement FET's. I have some FET's that seem like they should work, but I'm just not sure. Also, neither mouser or digikey have the one listed in the parts list, so I think other US builders may have the same question. Should any FET work as long as the current rating is sufficient for the job, or are there other considerations? I'm probably not worried about high frequency PWM.

Bryan

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What are the requirements for replacement FET's.

They have to be fast enough to allow PWM at 62.5 kHz. Formerly, there was the TIP120, which can switch currents fine, but only with a low frequency - like 10 Hz - algorithm.

The curious thing I've yet to understand is, AFAIK all available firmwares use PWM for the heating elements, but the FETs on Gen2/Gen3 are these TIP120s. Wonder how this works together, probably I miss some detail.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I just spent wayyy too much time trying to get an old laser black & white printer working well enough for this, and the only 2 prints that didn't come out with toner or random lines through them I didn't iron enough. Ah well, practice....going to wait to use a different laser though.

I'm really starting to get excited...thanks for all the help Traumflug.


Edit: I got it. Etched and everything. That was a lot more effort that I thought it would be. The method of using glossy magazine paper worked first time for me, although there are a lot of pinholes in the traces where 2 motors connect to the pololu drivers, they have continuity. I had to patch a few places up with sharpie, and the other side of the board wasn't completely etched away, but I can dab it on with some Q-tips or something. Looks beautiful...I'm going to have to make PCBs more often.

I'm not looking forward to drilling all these damn holes, though.

Edited 1 time(s). Last edit at 04/07/2011 12:47AM by Cain.

Traumflug Wrote:
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OK now I'm confused. Is there a Traumflug impersonator in the house? Weren't the first few Gen7 boards unable to do PWM, and using Teacup as in the post linked below?

[forums.reprap.org]

Have things changed since a couple weeks ago that no fimwares use on/off heater controll? I have some TIP 120's I might use unless that is no longer an option.

Bryan

> What are the requirements for replacement FET's.
>
> They have to be fast enough to allow PWM at 62.5
> kHz. Formerly, there was the TIP120, which can
> switch currents fine, but only with a low
> frequency - like 10 Hz - algorithm.
>
> The curious thing I've yet to understand is, AFAIK
> all available firmwares use PWM for the heating
> elements, but the FETs on Gen2/Gen3 are these
> TIP120s. Wonder how this works together, probably
> I miss some detail.

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Have things changed since a couple weeks ago

Yes:
[github.com]
[github.com]

The nice thing about replicatable boards is, you can change them from one to the next.

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that no fimwares use on/off heater controll? I have some TIP 120's I might use unless that is no longer an option.

Generation 3 Electronics uses the TIP120, at least in all the design files I could find so far. So, heater control with a TIP120 is definitively possible. I still haven't found out how it works for those people running a recent Teacup on Gen3. Older versions of Teacup use on/off heater control and probably older versions of FiveD as well.

It would be great if you could help bringing light into the issue, bryan. The TIP120 is not only cheaper as the IRFZ 44N, low frequency heating also wastes less energy inside the MOSFET, reducing the need for heatsinks.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Hmm. I wonder why we need high freq. heater control. Does it make a big difference in quality? I can't imagine that the temp is changing so fast that you can't wait a few tens of milliseconds to adjust the heater. I'll start a thread in the firmware forum and see what comes of it.

I believe that most tip that use an aluminum or brass block heater has enough mass and slow response that PID control is not necessary. Simple bang-bang control is sufficient. Adrian mentions this in the wiki on his extruder design.