MendelMax Upgrade

MendelMax Shaft Couplers

Our MendelMax 3D printer hasn’t even printed anything yet (The first extruder we fitted was unfortunately far from serviceable, and we’re still awaiting some parts for the replacement – a tried and tested design) but we’ve upgrading parts on it already. The printed shaft couplers never seemed particularly robust, and since we’ve got our lathe working it seemed like an excuse to produce something useful. I’m rather pleased with the result, they should be far more rigid than the printed parts they replace, and they’ll fit in rather nicely with the black and aluminium colour scheme.

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Weaponry makes the Perfect Gift

As a member of the Hackspace it crosses a few members minds of how to use the functionality of the space with the opportunity of giving a present to someone.

A long friend of mine is a devout fanatic of the TMNT - collecting nigh everything available and it’s his 30th birthday this year near christmas. So myself and the girlfriend thought, what better than to give him something he cannot buy?

With Jo‘s talents in Fimo and the resources available to me, we decided upon figurines. However, these required weapons. With a bit of resourcefulness, soldering, patience and heavy hitting by myself and pbrook and some laser off-cuts we managed to produce something resembling the TMNT load-out:

TMNT Weapons

They have since been touched up with a bit of paint to cover the initial attempts at soldering the metal pieces together and neaten up the blades from being hammered. The ‘grips’ on the swords may be lightly painted, to retain the look formed by squishing the metal under great pressure by a vice.

I’m quite happy with the result and the ‘chain’ for the nun-chucks, made by braiding wire together.

Update: Here are the finished items:

TMNT Weapons

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Is it me, or is it hot in here?

As anyone who’s been to the hackspace recently will know, it’s often not the warmest place.  This has led to some members becoming a bit obsessed with temperature sensors.  Our resident bot already has a temperature sensor, but we had our suspicions about its accuracy, and it doesn’t have a convenient readout.

Minimus based temperature sensor

I recently acquired a nice 1″x4digit 7-segment LED displays. Unfortunately these came without datasheet, so the first task was to reverse-engineer the pinout.  It turns out they aren’t 5v tolerant.  Applying 5v causes the segment to briefly glow orange, followed by the release of magic smoke. After installing some limiting resistors I figured out the wiring for the remaining 3.5 digits!

This combined with a minimus (small arduino-like microcontroller) and a DS18B20 temperature sensor gives in a handy self-contained temperature readout.  About the only notable oddness is I chose to multiplex round the segments rather than across the digits.

This all seemed a bit too easy.  We’ve recently had a big pile of discrete logic chips donated (mostly 74 series).  A digital temperature sensor seemed like a reasonable project to make use of them.  i.e. replicate the device above without using a micro-controller.

The design is constructed as follows:

  • A thermistor in voltage divider, driving the analog input of an ADC0804.
  • An 8-bit (dual 4-bit ripple connected 74LS191) binary count-down counter.  Load with the ADC output value.  Clock gated on zero detect.
  • Dual 4-bit BCD counter (CD4518 in ripple configuration).  Counts up from zero synchronously with the count-down counter.
  • Dual 4-bit tri-state buffer (74LS244) multiplexing BCD counter output onto BCD 7-segment driver (CD4511).
  • Common cathode 4-digit (2 used) 7-segment display with N-channel MOSFET (BS170) drivers on the cathodes.
  • Control logic consisting of 2-bit counter (74LS191, bit 2->reset) feeding 2-to-4 address decoder (74F138).  The 4 outputs trigger the ADC conversion, counter reload, and two display digits in turn.
  • 30KHz 555 based oscillator clock input to ADC and counters.
  • 200Hz  555 oscillator clock input to control logic.
  • Misc NOT (4069) and AND (7400) gates.

A few issues encountered along the way:

  • It’s worth trimming the legs on capacitors and resistors before plugging them into breadboard.  Otherwise adjacent long-legged components are liable to short together causing intermittent hard to debug failures.
  • The oscillators are quite noisy.  It’s important to have sufficient power supply decoupling/smoothing capacitors, especially on long supply rails.
  • I initially got the clock polarity wrong for the count-up timer.  This resulted in a race between the active clock edge and the reset/enable signals.  Inverting the clock signal gave a stable count.
  • My nice jumper wires are slightly more than 0.1″ diameter.  i.e. they don’t quite fit in adjacent breadboard sockets. After a while I ended up just using lengths of solid core equipment wire.
  • Logic analyzers are really handy.  I don’t have one but bodged together a cheap one using a Minimus/Arduino. It’s not fancy, but more than sufficient for debugging 30KHz signals.

There are two multi-turn potentiometers for adjustment.  The first sets the zero point via the ADC negative input.  The second forms the potential divider with the thermistor, and allows the scale to be adjusted.  While the temperature response is nonlinear, within a small range (say 0-30°C) it’s not too far off.

The finished build spans two and a half large (~1200 hole) breadboards, and runs off a 5v supply.  It displays positive temperatures to within about a degree.

Update: A bit of rewiring and it now fits on a single (large) board.

Discrete logic implementation

 

"Compact" discrete logic layout

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Leeds Raspberry Jam – 15th December

We’re hosting Leeds’ first Raspberry Jam!  For anyone who’s interested in the Raspberry Pi and would like to meet up with other people who share that interest.  There’s no strict structure to the meetup, but we plan to have demonstrations of things people have done with their Pi, maybe a talk or two on people’s projects, and hopefully plenty of people on hand to help out with any issues people are having.

You don’t have to have a Raspberry Pi to come along!  In fact, this might be a good opportunity to see what all the fuss is about.

If you’re interested in attending then please register here so we have some idea of numbers attending.

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Workshop Update

First job in the lathe

I’m happy to report that our lathe is now working. There’s a shortage of tooling at the moment, but hopefully this situation will improve over the next few weeks. Details on the lathe are being collected in our wiki.

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Come Find Us – November 2012

From the 23rd to the 25th of November creative places around Mabgate and Sheepscar will be open to the public and we’re happy to announce we’ll be taking part. The hackspace will be open from 12pm to 6pm on Saturday the 24th and Sunday the 25th of November for you to drop in and investigate the projects we’re working on and the facilities we have available.

Further details of Come Find Us events can be found here.

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3d Printshow London

This weekend was the 3d printshow in London and I (Martyn) went down to see who was there, on the midnight coach on Friday, arriving in at 06:20!

Well there were quite a few interesting people at the show, but some really stand out ones as well.

Makerbot were there in force, I didn’t actually speak to any of the main team, but I understand Bre was there at some point.  Makerbot are quite a controversial brand at the moment given their choice to not opensource the Replicator2.

There was a very nice all-metal 3d printer from cb-printer.com - the idea here is that the printer is a tool, should be solid and well built, much like our MendelMax that we’re building.

Formlabs are perfecting the high-resolution resin-based 3d printing technologies with their very nice looking Form1 printer – with a 25 micron layer height.

Autodesk, Tinkercad and various other 3d software vendors were there, most trying to sell their solutions, which to an opensource advocate like myself, didn’t impress :-)

There were also a lot of exhibitors of artwork, jewellery etc. which even to an uncultured geek like myself were very impressive!

But the hidden gem was printrbot – Brook Drumm was there and is a really cool guy – the printrbot really is the little printer that could – all laser-cut parts, foldable, fits in a backpack and on top of that, it can run off rc car batteries for about two hours!

Of course I got really excited and printrbot is open hardware and $400 for the kit.  If I had a pot of money I’d be looking at becoming a UK distributor for it.  He also showed off his latest prototype that is is a transformer of sorts – it folds up into a suitcase!

I managed to squeeze in a visit to Star Trek London, which in comparison was a huge money making exercise.  Whilst they had a lot of famous actors there, you couldn’t get into the packed talk areas, as the people with money who had the special tickets for guaranteed seats.  £15 for an autograph… £10 for something to autograph… yeah, the yorkshireman in me was sorely disappointed.

I rounded off my visit to London with a visit to London Hackspace, which was good, although I was disappointed to not get my hackerspace passport stamped as they had no stamp and their lasercutter was out of order.

So that’s the weekend of one northern hacker in London.

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Everything’s Better With Lasers!

We have a saying, “everything’s better with lasers!”, this definitely applies to a hackspace and now we’ve got access to a laser cutter we’re out to prove it. Inductions in use of the laser cutter are ongoing, laser cutter time is available for a small charge, and we have a selection of laserable materials available at reasonable prices. If you’re designing something to be laser cut then we’d recommend using either inkscape or librecad (totally down to personal preference) and export it in dxf format.

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It’s coming….

Soon our battlestation laser cutter will be fully operational, and we’ll be one step further towards world domination.

Yes, on Saturday 6th October we’ll be acquiring our first laser cutter, and it seems that members are already thinking up lots of projects involving it.

We’ll provide further updates once it’s safely installed in our workshop.

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Arduino and the Minimus 32

We recently bought a big pile of very cheap AVR Minimus 32 USB dev boards via Manchester Hackspace.

These ship with a DFU bootloader.  This works fine when building regular C code, but that involves a fair learning curve for people new to embedded development.

To that end I implemented Arduino support for the Minimus.  This is now available on github.  An AVR-ISP programmer (or Arduino pretending to be one) is required to replace the bootloader, but after that ‘s just as easy to use as any other Arduino board.

We have spare Minimus boards for sale at the space.  We’ll even flash the Arduino bootloader at no extra cost :-)

 

Posted in Arduino, Bought Kit | 4 Comments