Finally introducing… PolargraphSD v2!

I wondered if I would ever get here to be honest. It was only the thought of dozens of angry Polargraphers chasing me into the town square with pitchforks that gave me fear hope.

PolargraphSD v2

I have stock! The first couple of machines will be being posted or collected during this week.

PolargraphSD v2

To the folks who have so far only paid a deposit: I’ll be sending you an email out when your machine is ready, and asking you to go and pay the balance. To those kind, generous trusting souls who already paid up front during the pre-order period: Thank you. Without that we wouldn’t have even got this far. I will drop you an email to confirm your delivery address (in case it has changed in the meantime), but unless I hear back in the next few days, your machine will be winging it’s way to you as soon as it’s built.

PolargraphSD v2

 

Seriously, thanks for being so patient. This machine is a much better product because of it, I have much more faith in it now than if I’d had to rush it out the door two months ago (eek, when I said I would). I really hope you’ll enjoy using it.

I’ll do a bit more of an “unboxing” guide in the future. There is a still a long waiting list for this machine, but now stock actually exists, it’ll be moving fast at least. It can be bought along at The Polargraph Shop.

 

Slow going

Slow going, but … going!

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The hardware is working fine now, working with all kinds of SD cards, all servo motors and all power supplies, but I’m waiting for the full set of the new cases to be cut and sent.

The case is funny. Probably the ugliest thing I’ve ever made, but I quite like it.

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Choice between clear acrylic and MDF – any thoughts? The clear looks shows fingerprints but looks pretty snazzy.

 

PolargraphSD progress

The PCB v2 testing is still ongoing, the end is closer and I’m expecting the final boards late next week. This extra round of board testing was always accounted for in the schedule, but what I didn’t account for is the last set of PCBs taking three weeks instead of one week to arrive. So although I feel this is disastrous, and the project is crashing down around me, actually it’s only literally two weeks behind, and I just need to get a grip.

I know that’s not much consolation to those of you who have been waiting since February, and I am really sorry about that, and that’s the bad news.

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Why

I’ll do a proper introduction when it’s done, but in short, the Polarshield v2 has an integrated switch-mode step-down power supply so that the arduino can be run safely from a single higher-voltage power supply, without overworking the arduino’s on-board voltage regulator. That’s all gone fairly smoothly. This makes the system much more tolerant of working with cheap, basic arduino clones.

The second feature is fixing the circuit that converts the arduino’s 5v signals to the 3.3v signals that the screen and SD card expect. Previously this used resistor networks, but I’m using logic buffer chips now. This should make SD cards from different manufacturers much more reliable. BUT, it is new to me, and that’s why I’m determined to make a mess of it.

For those who are interested, the PCB files, and the gerbers that go to the PCB house are in the repo at https://github.com/euphy/polarshield_hardware.

Parts are slowly rolling in

A big lovely batch of shiney stepper motors arrived today. My electronics parts came last week (£650 of ICs and connectors – that is always so disappointing to receive). I’ve got a pile of touchscreens, and stepper motor drivers, and a big bag of drive sprockets. A big box of MEGA2560 R3s. Red ones.

The first version of the Polarshield v2 was tested and found wanting, so I’m expecting the samples of the final version at the beginning of next week. The first batch of PCBs took a week to arrive, this batch has taken three weeks so far. I am looking for a new supplier.

So unfortunately, that has eaten up all of my contingency, and then some, and so I’m already behind before I’ve even started. Great!

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Running Polargraph on RAMPS

There’s been a bit of discussion on the forum about the adaptations required to run the Polargraph firmware on RAMPS. The good news is it’s easy. I’ve just committed some changes to the polargraph_server_polarshield firmware that should make it easier to run on different hardware other than the Polarshield.

There is a little chunk of code like this in the main polargraph_server_polarshield.ino file:

#ifndef MOTHERBOARD
#define MOTHERBOARD POLARSHIELD
//#define MOTHERBOARD RAMPS14
#endif

Comment out the POLARSHIELD line and comment in the RAMPS14 line, and your machine will be rigged for RAMPS. See this Polargraph wiki article wot I wrote up.

 

Polargraph Server for Adafruit Motorshield v2

There’s been a bit of ongoing investigation about getting the polargraph firmware running with the new Adafruit Motorshield (v2). I have just got one of these shields recently, so have only just had a chance to work on it tonight.

https://github.com/euphy/polargraph_server_a1

The new Adafruit library is slightly bigger than the old one, and the polargraph_server_a1 firmware was super tight on space already, so I’ve split up the code into a set of features that can be easily enabled or disabled at compile time to save space:

  • PIXEL_DRAWING – This is pixel shading.
  • PENLIFT – Controlling a servo to lift the pen.
  • VECTOR_LINES – Drawing straight lines, aka vector plotting.

So to get this to fit on, you need to disable either PIXEL_DRAWING or VECTOR_LINES – can’t have both anymore, not with Motorshield v2.

For convenience, I’ve pre-compiled two binaries, one for Motorshield v1 (using AFMotor), and the other for Motorshield v2 (using Adafruit_MotorShield). The firmware for Motorshield v2 has pixel drawing disabled.

This is a bit of a pain, but I don’t see an acceptable alternative.

I haven’t tried this for actual drawing yet, because I haven’t got a machine made up that uses this system, but at least the motors move! Please let me know if there is any success – or otherwise.

Happy scribbling!

Polargraph at the Edinburgh Science Festival

So I’ve finally been able to step away from the new installation that I’ve been building to be presented as part of the Edinburgh Science Festival, in the Grand Gallery in the National Museum of Scotland. It’s pretty swish.

Polargraph at Edinburgh Science Festival

A little PC inside uses a webcam to detect faces in the crowd, and the faces that stay still are snapped, cropped, converted to line art and then drawn out on one of the two drawing machines either side.

The machines themselves are a new prototype breed of Polargraph, with Teensy 3s at their hearts, and Easy Drivers doing the moving. The guts of them are laid out as on an dissection table.

Polargraph at Edinburgh Science Festival

The drive chain consists of a stepper motor and an optical encoder, coupled by the beaded cord. The encoder keeps track of the true position of the cord, and so these machines are wonderfully robust. They can hop and skip, get pulled around and abused and they do not lose position.

PolargraphPro transmission

Small magnets sewn onto the cord, and reed switches above the encoder wheel make self-homing trivial.

PolargraphPro homing mechanism

The pen lift is half a lolly stick, hot-glued onto a servo motor, blu-tacked onto the gondola.

Polargraph at Edinburgh Science Festival

The controller is a Python Flask web app, publishing its interface as a web page. It is very simple at the moment, but is pretty extensible. Part of the app is a core class that encapsulates the communications, queueing and commands. Writing this in Python rather than Processing / Java has been a resoundingly positive experience (less so actually installing Python and it’s libraries on Windows – but you win some, you lose some).

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The firmware is a stripped-back version of the standard Polargraph firmware, using a couple of nice Teensy features – namely the IntervalTimer library to deal with serial concurrent serial comms.

The Making It exhibition runs from the 5th to the 20th of April, in the Grand Gallery of the National Museum of Scotland. It is presented by the Edinburgh International Science Festival. You should go and see it!

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Polargraph Pro Preview

Hello, I’m getting excited about the new Polargraph installation that’s been eating up all my time recently. IMG_20140327_160058025_HDR This is part an exhibition called Making It, itself a feature of the Edinburgh International Science Festival, and it’ll be running in the Grand Hall of the National Museum of Scotland, here in Edinburgh, for most of next month (April 2014).

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I’m just putting some finishing touches to the machine and the control software.

There’ll be more of an update when it’s up and running.

Mystery of the Gappy Drawings- new controller version

I have uploaded v1.7.1 of the controller here on github. I know it’s in the wrong place, but I couldn’t figure out restructuring the projects quite yet.

So, polargraph innovator Kongorilla pointed out that he was getting gaps in his pixel shaded drawings, some 8 months ago. I was baffled, but agreed that , forsooth, they were gaps. Like him, I’d seem them, but never seemed to be able to replicate them. Like a ninja, they seemed to melt into the night, leaving me with a haunted feeling.

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Well, thanks to his work, including the sample drawing patch above, and encouraged by code sleuthing from Nosetinker (and literally no contribution from me), a solution has been found!

While the value for grid size is displayed as integers, internally it is handled as a float. In the example above, the grid size was displayed as 41, but was actually 41.5, internally. When the positions of each pixel were calculated, and rounded to the nearest integer, 41.5 became 41. The next pixel along was put at 41.5+41.5: that is 83, and there’s no rounding there, but that means that there is 42 steps between them instead of 41.

So one pixel is 0.5 steps too high, and the next pixel is 0.5 steps too low. Simple! I had thought it would be something more tricky than that – thanks to Nosetinker and Kongorilla for shining a light on this – sorry it took me the better part of a year to get around to doing anything about it.

Note – I don’t have a machine right here to test it with, so it still might be something afoot. There are no updates to the firmware, but it is included in the zip.

(Note the first version of this, 1.7 wasn’t right, hence the extra .1)

Pre-order PolargraphSD v1.8

I’ve just made a listing for the PolargraphSD v1.8, over at the Polargraph Shop.

The price of it is likely to be the same as the last round, but if you want to pre-order at a decent discount, you can put a 25% deposit down to hold your place in the queue as well as make cash flow a little more predictable. It’s a kind of micro kickstarter. I hope to have this ready for shipping in May, but it’s more likely to be June.

I hope to enlist an extra pair of hands to help me assemble this time around, and am having this semi-formal fund-raising period so that I can buy a few critical parts in a full-sized batch (ie 50), rather than buy them piecemeal over the run of the batch. That ended awkwardly last time, with delays and malfunctions a-go-go.

Edinburgh Science Festival Project

I’ve been asked to make an installation as part of the Edinburgh Science Festival in April, so that’s the project that’s eating up my time at the moment, and the reason for the halt to PolargraphSD manufacturing.

This thing is going to be great though: Two large portrait machines, continuously drawing faces from a kinect / webcam on rolls of paper.

I’m using a Teensy rather than an Arduino for this project, EasyDrivers and optical encoders to close the loop and keep track of position. This will make for a more robust, semi-automatic machine. I hope to have endstops too, and a good presentable gondola that can take a range of fat pens.

I also hope to be taking one of my machines along to the Mini Maker Faire that closes the festival at the end of April.