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Author Topic: Kia Ora from New Zealand
RussellR
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Post Kia Ora from New Zealand
on: August 23, 2018, 04:38
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Kia Ora!

After desmantling several large office printers a few years ago I've been sitting on a heap of odd steppers, servos, belts etc.

I have a running polargraph going with some minor changes to suit the following hardware:
Arduino Uno
CNC Shield v3
2 x A4988 drivers
Generic 5v stepper

I fluffed around and have included a 'pen down/up' and indicator which doubles as control for a solenoid to do the lifting. Solenoid means substantially quicker transitions between pen up/pen down making the drawing process quicker. I'm still waiting on a 5v solenoid from China to finalise the gondola. My end goal is to have this scaleable and to run it at the local pop-up galleries and to do some cooler stuff with interchangeable gondolas and to try and figure out how to use gCode tool paths and pocketing to colour in my SVGs.

The software offered up a ton of problems in the start as I found a lot of the tutorials easy enough to follow but (for me) failed to have enough of the 'why' behind things and it was also the first time I'd touched java/processing.

I want to do more and have ordered an Arduino Mega, prototype shield and a 3.5" touch tft to suit. Hopefully I'll be able to get it all working.

I have a question - is anyone sitting on some notes or a guide to making a 'custom' Polargraph SD to use whatever step/dir/enable pins, lcd pins etc?

Also, when using the mega tethered to a pc via USB, are the extra mega functions available? (Norwegian, circular etc).

Probably enough for now - time to get the kids from school! Happy graphing...

RussellR
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Post Re: Kia Ora from New Zealand
on: August 23, 2018, 04:51
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These are some snaps 🙂
Image
Image
Image

sandy
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Posts: 1323
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sandy
Post Re: Kia Ora from New Zealand
on: August 24, 2018, 06:33
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Great build! That solenoid lift is good and I'm glad you got the software running well enough eventually 🙂

I haven't seen any other builds that use a TFT though I think MarginallyClever's bot is based on a 3D printer control board that has an LCD+encoder for input.

The source files for the PolargraphSD are all open and available (https://github.com/euphy/polargraph_server_polarshield) but I'll admit it probably isn't very easy to read.

It uses Henning Karlsen's UTFT and UTouch libraries so any display that that is compatible with should work. I've only ever used a screen with a parallel connection and an 8 bit data buss with that library. I have a good stock of those screens leftover if you want a couple - drop me an email (sandy.noble at gmail ) with your address if so.

The newest PolargraphSDs will be based on an ESP32 microcontroller with an SPI controlled LCD. Those SPI screens are easier to find than the older ones these days, and the ESP32 is plenty fast enough to drive them fluidly. I did try the same screen on a MEGA2560, running on SPI and it worked, but it was too slow to be practical - the screen redraw took more than a second (there's a video of this kind of screen with a regular Arduino here https://www.youtube.com/watch?v=rXMZHMmk9pQ).

The MEGA-only features are available while tethered, but the norwegian pixel does need an SD card. So you can start the drawing via the controller app, but you give it the name of the file and it looks for the file on the SD card. It wasn't practical to run it over USB! Too slow.

sn

RussellR
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Posts: 6
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Post Re: Kia Ora from New Zealand
on: August 25, 2018, 07:04
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G'day Sandy,

Regarding the speed over USB being too slow: I've had a play and found that doing simple things like unchecking 'Show Image', 'Show Vector' etc makes a Highly noticeable difference to speed. Maybe the delay is in the Controller software implementation as oppose to the USB itself. Then again, I programmed Borland C++ at Polytech night classes while I was in grade 9 some 25 years ago. While I can still interpret syntax etc I find it a slow process to write/edit code nowdays.

I like the whole 'being tethered' part of your polar plotter as it kind of takes me back to old dot matrix printers. I'd love to have a dirty old LPT port with a brakout cable running things!

I have my plotter running next to me laying several different images to hopefully get some cool outputs. Post when done.

sandy
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Posts: 1323
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sandy
Post Re: Kia Ora from New Zealand
on: September 1, 2018, 19:09
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Yes, I've noticed the speed difference too. I never imagined that the graphics update would be the bottleneck in that chain! It is mostly a fairly inefficient comms protocol, but there is a bit of time swallowed up in drawing. Switching to the "Queue" tab is fastest of all.

sn

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