2.x for kbob's maker space

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Laying out the electronics

Postby kbob » Mon Dec 24, 2012 6:38 am

I am deciding where to put all the things in the electronics bay. Here are two possibilities. I'll call them Configuration A and Configuration B. First, here's A.

IMG_9404.JPG
Configuration A, Top View


IMG_9405.JPG
Configuration A, Side View


And here's Configuration B.

IMG_9402.JPG
Configuration B, Top View


IMG_9403.JPG
Configuration B, Side View


The two configurations have some things in common. The main power plug is always at the back right corner (not shown). The mains power distribution block, represented by a silver bow, is right in front of it. The PC power supply is along the side of the box. I will cut a hole in the skin to let its fan breathe. The water pump is not shown. It will be outside the chassis. The laser power supply is not shown. It will be on a shelf above all these bits, at the same height as the laser tube. So there are really three components to place.

The air pump has power and air in and out. The air outlet is the brass barb on the end. The air inlet is a black screw fitting sticking out the side of the opposite end. I powered on this air pump for the first time today. It sounds like a freakin' jackhammer. I want a quieter pump. But its connections are very simple.
  • power from power distribution block
  • air in from grommet at back
  • air out to gantry

The Raspberry Pi is the front end processor. It will have these connections.
  • power from PC supply, +5V standby
  • Ethernet to back panel
  • USB from type A connector to the Azteeg
  • USB from type A connector to the front panel (optional)

The Azteeg X3 is the real time processor. It will also handle manual mode operations. It will have lots of connections.
  • power from PC supply, +5V standby
  • power from PC supply, +12V for motors and relays
  • lead to PC supply to switch main power (+12V for motors and relays, +5V for LEDs)
  • inputs from +Z and -Z limit switches in back
  • inputs from -X and +Y limit switches on gantry
  • outputs to Y and Z stepper motors in back
  • output to X stepper motor on gantry
  • input from door open switch in front
  • input from E-Stop switch on top panel(?)
  • inputs from buttons and joystick on top panel, details TBD
  • outputs to LCD panel on top panel, details TBD (optional)
  • SPI outputs to LED strip on gantry (optional)
  • outputs to relays to switch power on air and water pumps and laser power supply (optional)
  • inputs from thermistors in water lines (optional)
  • input from flow meter in water line (optional)
The Azteeg has three high current outputs (for bed heater and two hot ends) that I can use for a power relay. It already has inputs designated for thermistors. Just about everything labeled (optional) will be done later, after I get the basic laser running. Because it has wires going everywhere, it's really impossible to optimize its placement.

So. Back to configurations A and B.

Configuration A puts the CPUs up front where they're near the control panels and the PC power supply's output, but they're far from the back panel and the sensors and motors in the back. In configuration A, the Y cable carrier would exit toward the front of the chassis.

Configuration B puts the CPUs closer to the rear. It is possible to reach in and change the SD card in the Pi there. The Azteeg is closer to the motors and sensors in the rear. In configuration B, the Y cable carrier would exit toward the rear.

Now that I've taken time to describe all this, I'm envisioning Configuration C (no photo, sorry). Start with B, switch the Azteeg with the Pi so the Pi is closer to the front of the case, and rotate the Pi so its SD card slot is facing toward the laser bay for easy access. The Pi has many fewer connections, so it can be out of the way. The Azteeg's orientation is less obvious. It has power connections coming off both short ends of the board, gantry connections coming off both long ends, and connections to the front panel and rear chassis coming off everywhere. I might as well just orient it so its lettering is right side up. (-:

I've used the term "power distribution block" above a few places. I don't actually know what that should be. It will take in 110V power and redistribute it out to several other places. It's sort of a power strip. (-: I would also like it to have some outlets that are switched by a relay (or solid-state switch?) What do I need? Bart's BOM calls for a "DIN Rail" and several "DIN terminal blocks". Is that what I should use? Can I get a version of that that also has relays? (I hope that last question conveyed how very far I am from my areas of expertise here. (-: )

And while we're at it, what are some good ways to keep all these cables (and air hoses) tidy?

Thanks for all suggestions.
Bob
"If you didn't code it, it will never own you." (-:
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Re: 2.x for kbob's maker space

Postby BenJackson » Mon Dec 24, 2012 7:28 am

I wouldn't put the air compressor inside... It vibrates a lot. Even on its little feet. If you really had to I'd go for some extreme isolation, like hanging it from bungies. You can also cut the vibration and noise with an output reservoir and some backpressure.

For power switching I got a 15A lighted rocker from a HW store and put it in the front panel. That switches the main PSU and the laser PSU. The main PSU is the power for the relays, so the blower/air/chiller current don't flow through it but the front switch still turns them off (the blower switching might kill it if the switch actually controlled it).
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Re: 2.x for kbob's maker space

Postby kbob » Mon Dec 24, 2012 7:41 am

BenJackson wrote:I wouldn't put the air compressor inside... It vibrates a lot. Even on its little feet. If you really had to I'd go for some extreme isolation, like hanging it from bungies. You can also cut the vibration and noise with an output reservoir and some backpressure.

For power switching I got a 15A lighted rocker from a HW store and put it in the front panel. That switches the main PSU and the laser PSU. The main PSU is the power for the relays, so the blower/air/chiller current don't flow through it but the front switch still turns them off (the blower switching might kill it if the switch actually controlled it).


I agree, the air pump would be better outside. I'll have to figure out where to put it.

What relays did you use for the blower?

Thanks.
Bob
"If you didn't code it, it will never own you." (-:
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Re: 2.x for kbob's maker space

Postby BenJackson » Mon Dec 24, 2012 9:01 am

This is the post from my buildlog where I show my electronics tray: viewtopic.php?f=16&t=557&start=40#p5741

The image is big enough you can read off the part number of the blower relay (you can't miss it!). It's a DIN mount relay that Bart sold me when I told him what I wanted to do. It's 3-phase (I only use one) and rated for inductive loads. I use it to switch the dust collector I use to exhaust air. It's way more powerful than necessary.

I may end up buying another small DIN relay to split up control of the air/chiller (currently I have those together on one relay, automatically activating when the laser is enabled and for 20s after). Some jobs don't really want assist air (cutting paper, engraving LaserMAX) so it would be nice to be able to enbed that in the job instead of doing it manually.
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Re: 2.x for kbob's maker space

Postby jv4779 » Tue Dec 25, 2012 4:00 pm

I have all the same stuff running in my Y axis cable carrier (minus the LED strip control line, mine is just a dumb 12v white strip). The limit switches run in a 4 conductor shielded cable and have not had any spurious limit errors on X or Y. Motor power and LED power are just unshielded wire.
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Re: 2.x for kbob's maker space

Postby kbob » Tue Dec 25, 2012 11:50 pm

Comment From Buildlog Author
I wonder whether the Azteeg has conditioning on its limit switch inputs like cvoinescu suggested. Roy hasn't posted the Azteeg schematic, has he? He did mention that some of the inputs have MOSFETS. (link)
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
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Re: 2.x for kbob's maker space

Postby Cre8ivdsgn » Wed Dec 26, 2012 6:08 pm

Kbob, I thought there was a post in this branch where someone was looking at how to go about rolling their own software/firmware controls. Perhaps I am mistaken, but just to have this information somewhere, there is the book "Stepper motors and their Microprocessor Controls"

Here it is on Amazon: http://www.amazon.com/Stepping-Motors-T ... r+controls

I apologize for injecting this into your buildlog but perhaps I am going crazy and this isn't where I saw it. Rolling your own is not for the faint of heart and your build is looking great!
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Re: 2.x for kbob's maker space

Postby cvoinescu » Wed Dec 26, 2012 9:25 pm

kbob wrote:I wonder whether the Azteeg has conditioning on its limit switch inputs like cvoinescu suggested. Roy hasn't posted the Azteeg schematic, has he? He did mention that some of the inputs have MOSFETS. (link)


Those seem to be outputs, not inputs (or, at least, the MOSFETs are used as outputs). Many controllers simply enable the internal pull-ups of the microcontroller, but that's not enough. Stiffer pull-ups are needed to reduce susceptibility to noise. I don't know what any of the Azteegs do, but even if they have external pull-ups I doubt they go lower than 4.7 Kohm or so (which, by the way, may well be plenty).
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Re: 2.x for kbob's maker space

Postby kbob » Thu Dec 27, 2012 12:02 am

Comment From Buildlog Author
Oops, you are correct. Pins D4, D5, D6, and D11 are used as outputs.

The ATmega datasheet says the internal pull-ups are 20 kΩ minimum, 50 kΩ maximum. That is very high, but not surprising.

Cre8ivdsgn, thanks for the book reference. It is available in the local university engineering library. (It's $81 on Amazon!)
Bob
"If you didn't code it, it will never own you." (-:
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Miscellaneous Assembly and Some Questions

Postby kbob » Mon Dec 31, 2012 1:03 pm

In the last four work sessions, I've done several things.

I printed Ben Jackson's laser pointer holder, got the right screws, and affixed it to the chassis.. I thought I'd ordered this laser pointer from Lightobject, but failed to do so. I've placed a second order, but I think they've shut down for New Year's.

I did order and did receive a big red E-stop switch, a two-axis joystick, and some silicon tubing from Lightobject. I don't need any of them immediately; I just wanted to fill out the order with the laser pointer. You know, the laser pointer that I forgot to put into the order. (Grrr...)

I cut the aluminum eggcrate to size on a borrowed bandsaw. Cutting aluminum eggcrate on a bandsaw is just like cutting butter with a chainsaw, only not as messy. The bandsaw is completely oblivious to the piece it's cutting.

IMG_9419.JPG
Eggcrate in Place


The eggcrate was 600×600 mm (23⅝ inches). That's a little short for the 2.x bed. I cut it as wide as possible, and cut out notches around each of the Z lift screws. After cutting everything, I cleaned up the rough edges with a Dremel and then folded and burnished them with a piece of pine 2×4.

IMG_9416.JPG
Cutout Around Z Screw


Question: How are you guys securing your eggcrate to the platform? Mine is just resting on the aluminum rectangle, but I want to secure it somehow.

I also printed a bracket to hold the Raspberry Pi. The Pi's designers neglected to put any holes into the board, so you have to find a way to clamp it. I printed this bracket. (I also printed this one, but it didn't fit as well.) The Azteeg X3 has the usual mounting holes at the corners, so I'm using conventional standoffs for it.

I mounted the two mirror holders. I had not noticed that they are different — one has the mirror left of center (mloc), and the other has the mirror right of center (mroc). You might say that they are mirror images of each other. (-: The mroc one lined up with the carriage mirror better, so I put that one on the gantry. Bart's drawing, D30025 rev 8, shows two mroc mirrors.

I originally put the X idler bracket where the X carriage would hit it just before it would hit the gantry end, and adjusted the X limit switch to match. But that puts the idler bracket in the path of the laser. It looks like there's room to put the idler bracket to the left of the laser's path, but that puts the belt into the laser. So I've put the idler bracket to the right of the laser's path, and I've lost about an inch of X travel. My assembly matches the drawings, but it seems like I must be doing something wrong.

Question: Where did you put your X idler bracket?

On 12/22 and 12/23, I overanalyzed the orientation of the Y cable carrier and the layout of the electronics bay. (Link 1, link 2) Now I have made the big decisions. The Y cable carrier will go loop-at-the-front, exit toward the back. The electronic components will go as shown here. Not shown: the Raspberry Pi snaps into the black bracket; the DIN rail will go just in front of the back panel, oriented laterally; and the air pump will go on the table beside or behind the laser cutter. (Thanks, BenJackson, for talking sense to me there.)

IMG_9426.JPG
Electronic Modules Placed


In this photo, the power supply is screwed down. The Azteeg and Pi have holes drilled and screws sitting in the holes, but I don't have any nuts. Hopefully the local fastener emporium will be open tomorrow.

I printed some brackets to attach the power supply to the Misumi rail. The one in front is straightforward .

IMG_9427.JPG
Power Supply Front Bracket


The rear bracket was trickier because the hole in the power supply is just 9 mm above the floor. I copied Bart's trick of intersecting screw holes. I doubt I would have thought of that if I hadn't just seen Bart do it.

I attached the Y cable carrier to the gantry end and marked holes in the bottom skin. But I did not get around to drilling them yet. (Also, no nuts.)

That is where I am now. What's next?
  • Get those nuts and screw down the computer boards,
  • Make a harness for the power wiring,
  • Test powering on the Pi and the Azteeg,
  • Get that laser pointer and wire it up,
  • Install the mirrors and lens and align them using the laser pointer,
  • Wire up the stepper motors,
  • Write software for a long, long time. (-:
Attachments
IMG_9429.JPG
Power Supply Rear Bracket
Bob
"If you didn't code it, it will never own you." (-:
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