Talk:PCB adaptions for Mendel

From RepRapWiki
Jump to: navigation, search

How much of this is really necessary

Jkeegan 04:24, 30 November 2009 (UTC) - Here's just a little feedback from someone going through all of this for the first time. Not wanting my first RepRap experience to be a SMT-soldering exercise, I'm one of the people in the boat you describe here - someone with pre-built generation 3 boards, but who is building a Mendel. While this issue (makerbot wiring vs mendel wiring) hasn't actually kept me awake at night with worry, it has at least caused me some worry and has slowed down my plans a bit. It certainly has to be having the same effect on others as it has had on me - it's yet another thing to have to worry about (and decide on), at a time when there are so many other unknowns to a RepRap beginner that it just amounts to a big unwanted distraction.

At the very least, it would be good to know which of these modifications are separate from each other, and which are at all required. Someone building their first RepRap probably wants to get something working first rather than having it look pretty and trimmed when it does work, and can push off the beautification aspects until later. That's certainly what I've been tempted to do with the RJ45 connectors on the extruder controller and motherboard, for instance - leave them alone for now, even with a long dangling patch cable in there, and fix them up later.

However, it doesn't seem to me (please correct me if I'm wrong) that it's a clean cut decision of "use RJ45 or use headers". In this same document describing the replacement of RJ45 jacks, there are also replacements of power connections, additional capacitors, and clipped resistors. Question: Is the power cable issue actually a non-starter for Mendel, vs just not looking pretty? Will I actually not be able to create a workable Mendel with all default-configuration boards (RJ45 jack, chunky 30 ohm resistor, and all) because normal power supply cables won't be able to reach the motherboard or stepper driver boards in their proposed location, for instance?

Once you're through a project and have it working, small/medium modifications to it can be an interesting additional project. Before you've ever had the project working though, those same modifications can seem huge and add to one's uncertainty and initial fears. I'm not tooooo worried about myself, really, I'm more worried about what percentage of people we have coming in trying to build this that it turns off or confuses.

I'm mostly sure that once I'm through this and wired it up, I'll look back and say "Wow that was a pathetic thing to worry about". But right now, where I'm at, the thought of ratcheting up power connectors side by side from my three hard-to-acquire SMT stepper driver boards (while desoldering them) sounds like quite a diversion from where I want to go - to a working RepRap that can print. So I want to avoid as much modification as I can, yet I still want this to be laid out as a functioning Mendel, and worry whether ATX power supply cables everywhere actually require this modification.

Anyway, that's what it feels like where I'm sitting right now. Identifying which of these modifications are really needed for Mendel (and which go with which - these components are for the power connector replacement, etc) would help a lot, IMHO.

Jkeegan 02:07, 8 December 2009 (UTC) - Even though Opto Endstops aren't shipped pre-built, this would still be a nice page to show how they're supposed to be wired. It would also be nice to have a quick bill of materials for this page, such as:

 Stepper Driver Boards (3)
 =========================
 3x:  3-pin 2.54mm-pitch pin-strip connector
 3x:  two-way 5.08mm-pitch screw connector  (for 12V wires)
 3x:  4-way 3.81mm-pitch screw connector
 
 Motherboard (1)
 ===============
 1x:  3.3 volt regulator (78L33 - get the TO-92 packaged one)
 1x:  100 μF capacitor
 5x:  2.54mm pin headers  (2 pins, breakaway headers are fine)
 tiny bit of insulated wire to connect power to USB
 
 Extruder Controller (1)
 =======================
 1x:  2.54mm screw connector for 12 volt power
 1x:  2.54mm 2-pin header (for RS485 comunications)
 
 Opto Endstops (6)
 =================
 6x:  3-pin 2.54mm-pitch pin-strip connector
 
 (plus some ribbon cable and compatible connectors for the opto endstops?)

Jkeegan 22:12, 21 May 2010 (UTC) - I want to add a big warning to this page that warns people to be extremely careful, as it's very easy to fry a stepper controller board, but I don't want to introduce unnecessary FUD (fear, uncertainty, and doubt). I've fried three boards already, even when trying to be careful.

I see that you were able to fix those 3 boards [1][2] by making sure the screw terminal made contact with the traces on the top and bottom. Yay! --DavidCary 17:42, 5 November 2010 (UTC)
I can't believe I didn't remember to come update this page once I determined the problem - I must have forgotten that I posted that here. Thanks! Jkeegan 18:26, 5 November 2010 (UTC)

I agree with Jkeegan -- this seems to be a lot of work with no clear benefits. There seem to be 5 independent changes here. Does anyone know: Why would anyone would want to make any of these changes? How much of this is really necessary?

  • Additional I2C on the mother board to connect to the stepper-motor extruder. This does seem necessary to drive a stepper motor extruder -- but not necessary to drive DC gear motor extruders, such as Nophead's Extruder Tweaks. But why does *this* stepper motor controller need 2 cables to the motherboard, when the *other* 3 stepper motor controllers seems to work fine with a single cable to the motherboard?
  • Another I2C on the motherboard to connect to ... something else?
  • Mods to the entire RepRap motherboard so it no longer needs an ATX power supply. This does look useful if you would like to replace the (heavy) ATX power supply with a smaller, lighter 12 V power supply, so it's easy to carry the system from one demonstration to another. But (if you happen to have an ATX power supply) it doesn't seem absolutely necessary.
  • bare motor wires plugged into screw terminal connectors vs. motor wires terminated with 0.156 inch pitch connectors plugged into corresponding connectors. How is either one is a significant advantage over the other?
  • MIN end-stop cable plugged into a 0.1 inch connector vs. MIN end-stop cable plugged into a RJ45 connector. How is either one is a significant advantage over the other?

--DavidCary 17:42, 5 November 2010 (UTC)