Step 15: Assemble the gondola

The gondola is the pen holder. There's a few alternative designs out there for them, including this 3D printable one that seems to do the business nicely. My design is much heavier, and has a hollow centre so that the pen can always be in the exact point where the cords converge. In practice, I'm unclear about how much difference this makes, but it makes me feel good.

I made the first one from corrugated cardboard, and a blank CD, stuck to some ball bearings (see the last picture on this step). Later I graduated onto some fancy-dan laser cut parts (available through ponoko, or you can grab the source from the github repo), but the principle is the same. I've attached the design in an EPS on a ponoko P1 sized board.

The parts just slide together, and then onto a length of brass pipe (see parts list). The laser cut parts have nodes in them that will need a little filing to get them on. Just be careful because the acrylic is pretty brittle. It should all push-fit together, but if it gets too loose, a few dabs of glue will keep it together. I usually put a bead of glue around the hole in the stabiliser, and then another couple of dots around the hole in the final spacer ring.

The sequence is, from bottom to top:

  1. Big stabiliser
  2. Empty bearing
  3. Spacer ring
  4. Bearing with straight cord hanger arm
  5. Spacer ring
  6. Bearing with offset cord hanger arm
  7. Spacer ring (this is the one I glue)
  8. And a plywood ring as a decorative touch
<p>Euphy,</p><p>New Problem. Well two actaully.</p><p>First, when I so a pen tip test it prints out super small not matter how much I change the setting.</p><p>Second, I am assuming also pen size related is that the lines it draws in the on pixel areas are really close together. When is gets to detail areas it just ends up filling in solid because I have not been able to figure out what the right setting are.</p>
Show me a pic of what you mean by super small. Small pixel, or small lines, or small spaces - you need to consider how you might expect me to be able to help based on what you state as the problem.<br><br>&quot;No matter How much you change the setting&quot; - which setting? Does the pixel density (the number of lines) change at all?<br><br>Are you using a very small grid size?<br><br>
<p>Euphy,</p><p>Here it what it looks like when I try to do a pen tip test and my settings. Not sure what I have done wrong.</p>
<p>Nothing wrong as such, but:</p><p>- Grid size is very very small. There is no effective way to express any differences in shade in a pixel that small, because of the thickness of the pen.</p><p>- Gondola is a bit wobbly by the looks of things. Even small details should have sharp corners and regularly curved edges.</p><p>You could try one (or all of):</p><p>- Put your grid size up to 50 and try again. </p><p>- Make sure your pen is not sticking too far out of the gondola, so the tip doesn't trail behind the movement of the gondola. Ideally you want the pen tip barely protruding.</p><p>- Knock your pen acceleration speed down (or up) to try and get some better control in the corners.</p><p>- Add a bit of weight to the gondola to pull the pen more taut</p><p>Pen width test is a great way of testing this though.</p>
<p>Euphy,</p><p>Here it what it looks like when I try to do a pen tip test and my settings. Not sure what I have done wrong.</p>
<p>Hello, can you help me with this step?</p><ol><li><strong>Install project: </strong>In the code bundle, copy the whole <em><strong>processing-source/polargraphcontroller</strong></em> folder into . </ol><p>Into where? Having problems with the software and I have no idea where you intended to tell us where to put this file.</p>
<p>Aha, I don't know why I'd removed that key part of the sentence, sorry... I've fixed the step.</p><p>The polargraphcontroller folder should be moved into your Processing sketchbook folder.</p>
<p>hey do you think I can built this project using labVIEW and my dec ?? It's really cool </p>
<p>I also plan to use this free standing with a raspberry pi zero and a display, to remove the need for a host PC in outdoor or mobile settings. The controller box is going to be very exciting since I am building it to support up to 4 stepper motors (Connected over a 5-pin MIDI cable, Supports both bipolar and unipolar steppers without wasting pins. MIDI Cables are perfect for this), as well as allow for on-board image processing, and real-time status info on the display.</p>
Controller doesn't really work on raspberry pi, but something lighterweight will run fine. Once the command queue is generated, the load to deliver it is very low.<br><br>https://github.com/euphy/polargraph/wiki/Standalone-command-queue-runner describes a low-cpu method.
<p>Awesome tutorial! I really love the design you used for the gondola, however, I have a question. How do you keep the drawing utensil tightly locked inside the brass tube? I recently started assembling and noticed that there is a bit of movement room even with a full-sized sharpie marker. I thought of possibly using some foam wrap or possibly making the tube longer to add some locking screws in the back. Thanks!</p>
I use this (https://github.com/euphy/polargraph_models/blob/master/Gondola_mod_v4_cutout.STL), which is very like this http://www.thingiverse.com/thing:31973.<br><br>But I used to just use a blob of blu-tack, worked fine!<br><br>sn
<p>In advance thank you very much for your great work ...</p><div><p>I do not know much about programming, but why Processing v.3 gives many errors when running the driver source ?</p></div>
There's lots of changes in Processing 3, so there's lots of work to adapt the code. I haven't done the work.
<p>I'm trying to verify polargraph_server_a1 to push it to my Arduino UNO, but I keep getting this error: polargraph_server_a1:157: error: 'multiplier' was not declared in this scope</p><p>The multiplier function is clearly defined in util.ino, but polargraph_server_a1.ino can't seem to see it. Am I making a basic mistake here?</p>
Nope not a mistake here, but there was a change brought in in the Arduino IDE v1.6.6 and later that broke some things, and this is one of them. There is a fix for it in the main repository (https://github.com/euphy/polargraph_server_a1), but it's not been bundled up for a official release yet. There's no reason not to use it though, if you can get it downloaded.<br><br>Workaround is just to use ARduino v1.6.5 for a bit longer.<br><br>sn
Can I use a Arduino uni R3?
<p>The Polargraph firmware works on an Arduino UNO.</p>
Can you send a circuit diagram of the polargraph
<p>Please don't spam the comments section. I would recommend you start with a more simple project to introduce you to Arduino, I can't help you with such basic questions.</p><p><a href="http://www.instructables.com/id/Arduino-Beginner-and-Basic-Electronics-Kit-Primer/," rel="nofollow">http://www.instructables.com/id/Arduino-Beginner-a...</a> or </p><p><a href="https://learn.adafruit.com/adafruit-motor-shield" rel="nofollow">https://learn.adafruit.com/adafruit-motor-shield</a></p>
Can you send a circuit diagram of the polargraph
How do you convert 220v(power socket) into 12v
How much should the voltage be
How much should the voltage be
Thank you for the answer.How can I connect everything to the power supply. Is the micro controller wireless?
Does the Arduino uno need to be connected to the computer at one end and the motor driver at the other end? Can I use a 9v battery to power everything or can I use my computer
Arduino needs a power supply. It can usually use USB power, but the pen lift servo sometimes causes it to reset.<br><br>The motor shield itself needs a power supply to drive the motors. It needs a proper mains power supply. A battery will not do. <br><br>This instructable contains links to Adafruit's descriptions about the motorshield https://learn.adafruit.com/adafruit-motor-shield/use-it.<br><br>sn
How should I connect the power source to the polargraph
<p>Hi, I am not sure how to upload the files into the arduino. I keep getting multiple errors every time I try to verify the code. I opened the files from the source code and opened them separately into one sketch. How could I fix this?</p>
http://www.instructables.com/id/Polargraph-Drawing-Machine/step8/Electronics-Arduino/ is the step that discusses this part.
awesome project
<p>Hello.</p><p>The motors are rotating in the directions they're supposed to. But, they won't stop rotating. What's the problem?</p>
Did you do a &quot;upload machine spec&quot;, and remember to do a &quot;set home&quot; each time the machine is restarted?<br><br>sn
<p>It started drawing instead of rotating endlessly. But it won't draw the picture. Instead it's only drawing those lines, as you can see in the attached image.</p>
<p>Hi.</p><p>The sequence of work is all right according to your instructions. But we still get empty waves. We tried different grid sizes and only one of them worked, it actually drew something, only the drawing was kind of compressed. It never drew again however.</p>
<p>II have the same problem. did you figure out a solution that you can share? thx</p>
<p>Hi, </p><p>I noticed that you used four wire stepper motors.</p><p>Would it work if i used 5 wire stepper motors? Is there somewhere to set that in the software? (I would be using my own chip to control the stepper motors instead of the motor driver boards)</p>
<p>Nope a 5 wire motor works exactly as a four wire one, you just don't connect the centre tap wire.</p>
<p>Great!</p><p>Also, when I try to run the controller software on my 64 bit machine running windows 10 the default.properties file is created but nothing is displayed. I've played with the compatibility settings, but still nothing :(</p><p>What OS do you run it on?</p><p>Could I run the Linux version on a raspberry pi? </p>
<p>Try the 64 bit, and the 32 bit version on windows. If neither work, you'll need to run it from source, using Processing. Luckily, I have just written up a page about how to do this :)</p><p><a href="https://github.com/euphy/polargraph/wiki/Running-the-controller-from-source-code" rel="nofollow">https://github.com/euphy/polargraph/wiki/Running-t...</a></p><p>Don't try to run on a pi.</p>
<p>Compiling from the source files worked :)</p>
<p>That's great news - good luck for the rest of the build :)</p>
<p>Your stepper motors are 400 steps per revolution (0.9 degree per step). My stepper motors are 48 steps per revolution (7.5 degree per step). I will probably use about a 1 inch diameter pulley. Do you think it will be accurate enough to be able to draw details with a 0.5 mm pen?</p>
<p>Define &quot;accurate enough&quot; and &quot;details&quot;. I say that like it'll make a difference, either way they answer is &quot;try it and see&quot;!</p><p>Are your motors really 48 steps per rev? Aren't they geared?</p>
<p>When i say &quot;accurate enough&quot; with a 0.5 mm pen, I mean that if i divided the drawing surface into 0.5mm spaces. Would the motors be able to move the pen to each 0.5mm space? </p><p>Yes, my motors are 48 steps per revolution (360 / 7.5) and if you turn the motor by hand i count only 13 steps per revolution. I'm 100% sure my motors are not geared.</p>
<p>You can probably figure this out easily enough yourself:</p><p>sprocket diameter is 25.4mm, therefore circumference is 25.4*3.141=79.8mm</p><p>So one step will pull in 79.8mm / 48. So about 1.6mm per step.</p><p>That's a pretty coarse resolution, yes, and no you couldn't achieve a solid inked area with a 0.5mm tipped pen. A sharpie might do it.</p><p>I would actually be pretty surprised if you found your 48 step motors could generate enough torque to actually turn reliably under load. Because each step is bigger, you'd usually need plenty of current to pull the motor to the next step. With a 200 or 400 step motor the distance between steps is much smaller so it can use a correspondingly smaller current - there's just less work to do.</p><p>That's why I asked if your motors were geared - the ones I've seen with a low steps-per-revolution have been geared because it's hard to drive motors with such big steps, unless your load is low.</p><p>sn</p>
<p>Now that i think about it Great Idea! because i'm using meccano i can easily gear the motors! The only problem with that is that it will make it noisier :( </p><p>How long does it take to draw an image? (Obviously it depends) On average for a &quot;normal&quot; piece of paper</p>
<p>Can I use a 12 v, 14 amp power supply? pls answer</p>
14 amp is a massive power supply, but it should work - it will power almost any stepper motor and driver you'd like to have. Depending on your motors and drivers, you might find that 12v runs the motors a bit &quot;hot&quot;.

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Bio: Like everyone, I like making things. I'm currently a computer programmer by trade, which I adore, but I like building physical things when I ... More »
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