Coffee Machine Update

Coffee Machine Update

The coffee machine works. It's good for single cups of coffee, as you don't have to stand there too long pouring water. The old coffee machine is definitely dying, it now takes about an hour to run a pot of water through it.

To investigate how easy it would be to automate the new machine, I set this up:

There's a peristaltic pump:

which pumps water from the kettle to the filter. The power supply is adjustable, which is important to ensure the water flow isn't too fast as it will overflow the filter. For the pump I have the suitable voltage seems to be around 4V, which is pretty low. Usefully the power supply seems to remember its setting when it's off so you don't have to set it up every time you turn it on. A simple voltage regulator circuit and a knob would be equally and probably more suitable.

This arrangement also means you can replace the peristaltic pump pipe if it is dirty or damaged. You can also clean the pipe. We've never cleaned the insides of the old machine.

Can Transformer

I was thinking about the battery connections on my DIY digital watch and how tricky it was for me to create things out of thin metal. Either I cut it by hand, which always results in less than perfect parts, or I spend quite a while setting up my CNC3020 and cutting it on that. That gives better results but can be fiddly.

Then I made the link between the problem and the drinks cans that I melt down for raw material. Drinks cans are made of aluminium or steel and come in a nice uniform shape. So I decided to make a machine that can turn these cans into useful stuff. And the CanTran was born.

It's actually a sort of CNC lathe that is designed to chop up drinks cans, transforming them into useful things. Putting a can in the machine is a simple matter that takes just seconds, using a spring loaded tail holder and a 3D printed part that engages in the can top at the other end.
 
It's got three stepper motors and a Proxxon rotary tool to do the cutting. The controller is a Duet:

 

 
which has a nice web interface and accepts gcode. I've always had a problem finding a tool to generate gcode, so I created a small simple script to convert DXF files to gcode. This isn't too complicated a task as the CanTran has 3 axes, but in reality is a 2D machine. The script converts just lines and arcs from DXF (LibreCAD) into gcode with just 2 Z depths at the moment. Any tool that generates gcode should work.

I use a D bit cutter, the same type I use to mill PCBs.


There's a little tour of the prototype here:

This is the machine cutting some test slots into a can. This is sped up by a factor of 20:

You can make labels with it:

You can cut letters into the can and then illuminate  it:

Or, cut abstract patterns and do the same:

I've put the 3D files here:

https://www.thingiverse.com/thing:3570030

We'll have to see how useful it turns out to be...

And the there was what went wrong.

Card Success

I like it when a plan comes together, especially when it doesn't work well at first.
The story starts way back when I saw that a long time ago Casio had brought out a programmable calculator that used magnetic cards to store programs. I had a Casio fx-502p many years ago and learnt a lot about programming using that machine. Things like how to fit a program into not a lot of space. There's a program I remember from the 1980's written by someone who's name I don't know, that played tic-tac-toe. You could only ever lose or draw playing against it. I am still looking for the listing...

Anyway, I found that there were a few calculators before the fx-502p, such as the fx-201p. After a wait of a year or so I managed to buy one of those and found it was programmed in a strange language that Casio called Fortran, but is better described as 'fortran'. Then I found the Casio PRO fx-1, which is an fx-201p with a card reader.

My Casio PRO fx-1

 
The fx-201p just forgets when you turn it off, which is an exquisite form of torture when you've just spent hours crafting a gem of a program and have no way of preserving it. The card reader makes it worth spending the time working on programs.

Card reading calculators aren't common, but there were a few. The main two were the HP41C and the TI59. The TI 59 filled the same niche as the PRO fx-1 in that it has lesser siblings that forget when power is removed. Both TI and Casio families have 'continuous memory' versions that don't forget when the power is removed as they keep a low level of power supplied to the RAM chips, but changing the batteries can be a problem with these. You also can't swap between different programs easily as you can with a card reader. HP had many card reader calculators in the line up as they make proper stuff. Later on manufacturers used cassette interfaces a lot, but they are slow and bulky on the whole.

Back to the PRO fx-1. After an ebay search finally came up with a PRO fx-1, I had to buy it. Unfortunately it didn't come with any cards. The cards are no longer sold by Casio any more (shame on you). They could probably be obtained from someone who has some, but I think you'd need to give them at least two unicorns in exchange. The cards are a bit oddball, too. From photographs I'd worked out that they were 93mm long, which is a bit bigger than a standard credit card. I hunted for cards of that size and they do exist, but they are rare and expensive. So, I figured that if I used a standard credit card and pulled it a bit slower then the calculator wouldn't know it was a shorter card than it was used to. Hopefully.

There was another, more serious, problem, though. The cards that Casio made had a strange band of stripes running the length of the card just below the magnetic stripe. They were printed in the same magnetic ink that the stripe is printed with, but this made no sense as intermittent magnetic stripes are just nonsense. As I had a calculator, I could investigate, so I dismantled my calculator and had a look. It turns out that, as people had guessed, the band of stripes was for optical synchronisation (of recording). There is an optical sensor in the top part of the calculator. This also explains why the cards are transparent.

This made more sense, the band of stripes isn't magnetic at all. This is a bit at odds with the manual which tells users that they can write protect a card by putting an 'anti-magnetic self adhesive strip' on the bottom stripe of the card. This implies that the band of stripes is part of the recording of a card, not the reading.

So, I needed to have an optical band of stripes on the cards. How do I do this? It occurred to me that instead of printing a set of stripes on a transparent card (You can get transparent cards, but they are another rarity) I could make holes in a normal card. Making 85 3mm x 0.5mm holes in a credit card sized card isn't exactly trivial, but when you have a CNC engraver it is in the realms of possibility.

I had a couple of expired credit cards so I put them on the CNC, created a quick DXF file, converted to gcode and had a go. The result was better than I expected. I tried the cards but they didn't work. I was expecting this as there are tow types of magnetic stripe (in general, there are actually many different subsets): low coercivity and high coercivity. Coercivity is a measure of how hard it is to magnetise something: if it's low corecivity (LO-CO) then it's easy to magnetise. If it's high coercivity (HI-CO) then it's harder. The units used for coercivity is Oe (Oersted) and LO-CO is around 300, HI-Co around 3000. HI-Co is used for cards that have permanent data on them, such as credit cards, as you don't want it to be accidentally erased. LO-CO is used for data that is rewritten often (more than once, really). The Casio cards are LO-CO, as you want to be able to record cards at will. HI-CO cards could have been used, but as they are harder to write data to, they take more power to write and hence battery life would be adversely affected.

So, the credit cards wouldn't work, but the optical stripe looked fine. I ordered some LO-CO CR80 sized blank PVC cards. In the meantime I had some help from the calculator community and was sent a photograph of a Casio card with a ruler nbext to it. Up until now I'd been sizing cards from parts of the calculator, which, it turns out, isn';t a good way to size things. This picture enabled me to determine that I'd got the size of the cards wrong and they were actually CR80 size. Good news.

There was bad news, though, as my PRO fx-1 seemed to have taken exception to being dismantled and had decided to stop responding to keypresses properly. After a disappointing hour or two where I thought I'd broken my calculator I determined that my calculator, even though it looked pristine, had actually had some battery leakage in the past. This seems to have caused some problems with the keyboard scanning, which I fixed by giving the keyboard PCB a good scrub.

With the keyboard reliable again, i was ready for the CR80 cards to arrive. Which they did. I put them on the CNC and milled some slots.

I used a 20 degree D cutter for this, at a low rpm to avoid melting the plastic. A 10 or 15 degree cutter is better.
Trying the card was disappointing, as it didn't seem to work. I couldn't get a card to store a program. As a last resort before giving up, I soldered some wires on the card read/write head and looked at the recording signals on my scope. I was interested in the data format and even if I didn't get my cards working then at least I'd be able to work out what the data format was and why there were 85 slots (for 127 steps, odd number). I was also wondering if the card reader was faulty in my machine. Looking at the recording waveforms

they looked healthy, so I looked at the read waveforms. They also looked healthy:

In fact they looked very healthy, and I thought that maybe I was pulling the cards through too fast. I slowed down the pull speed and success! I managed to record and read a card. Oddly, from that point on I have had no real problems recording and reading cards. I have also tried to pull them through too fast and too slow, but they just work, so I'm not sure why I had a problem before.

So, I can make cards for the machine. They take a while to mill, I have to mill twice, once for the cut and once to clean it up, and I have to use a scalpel to clean the swarf off the slots, but they do work.

Here's a video of me using one of the cards:

Making your own

If you want to do this, here's some details:

I used:

 LO-CO cr80 blank PVC cards
 0.2mm D 20 degree cutter  (10 degree or 15 degree is better)
 3D printed CR80 holder
          https://www.thingiverse.com/thing:3571814
 Gcode file to cut slots (on Thingiverse page above)
 CNC 3020 (generic CNC milling/engraving machine)

         

Cheap DRO Revisited

I thought it was time I revisited the cheap DRO, so I have put the files on github and made a video showing it all working. The files are very much a dump of my code and PCB files, there's no guarantee it will build.

DRO Github

It's a start though, if you want to have a go at making one. The video shows the physical arrangement and also shows the update rate.

I milled the PCBs on my CNC3020, so they were very cheap, if you were to have them made then you'd probably want to reduce the size quite a bit, or the cost could be quite high. They are all single sided.
I have not put it in a case, I have mounted it up high in the workshop so chips don't get to it (I only have a mini-lathe and mill, so they don't throw things about much).

I think the cost I gave of £150 is probably quite a bit on the high side, as I milled the PCBs, which is cheap and used cheap calipers. Some discrete components came from my parts bin, too.

Fisher Problem and Fix

The friend's problem with his Fisher printer has probably been fixed. The problem was a snag of the filament when the angle of the Bowden tube was anything other than vertical. The filament enter the heatsink in the hot end through a pneumatic fitting on his printer. neither of mine have that arrangement, so I haven't seen that problem. I made an aluminium tube that helped to hold the Bowden tube vertical, but it didn't quite fix the problem. Some support from the RepRap people and a design for a bracket was sent and printed. This does seem to have fixed the problem, except maybe when the effector is at the top of its travel.

The final arrangement is here:

It's difficult to see how the tube can be anything other than vertical, with all this encouragement...

Fisher 3D Printer Widget

This isn't for either of my Fishers, rather it is for a friend who has a Fisher that only prints when the Bowden tube is held in a particular orientation. This is odd and hopefully a proper solution will come forth. Until it does, I knocked up a widget that hopefully will perform the 'holding in a particular position' job. The position is vertical, so it was easy to make this widget on the lathe:

The pneumatic fitting is the latest way that the Fisher attaches the Bowden tube to the effector. Both of my printers have the tube screwed directly into he heatsink. The tube comes out at quite an angle and I see no problems.

The widget has a hole each end, one for the tube:

and one for the pneumatic fitting:

The fitting is a (very) snug fit into the end:

The flat is to provide some clearance for the fan which is close to the tube entry point. This could maybe have been 3D printed, but I didn't have any dimensions for the part, other than a 4mm hole for the tube. I machined the fitting hole by performing many test fits as I bored the hole out. To 3D print this would have taken many prints to get the correct fit. Hopefully Aluminium is a bit more rigid and durable than PLA.

Coffee "Machine"

The old coffee machine that we use is probably going to fail soon, it's second hand and pretty old. I saw a simple Japanese design a while back and decided to have a go at something similar. My version uses cheap Chinese components sourced from Ebay and some recycled  bits and bobs.

There's a filter in a funnel that direct coffee into a jug below. The funnel, filter and jug are ebay items. The stand is made from part of an old chair frame and some wood from a tree we had taken down in the garden.

It makes pretty good coffee, but has the downside that you have to pour the water through the coffee over a few minutes, it's not very automatic. It does have the advantage that you can quickly make a single cup of coffee, probably quicker than the automatic machine can manage.

The filter is metal, I had to cut a handle off it so it had a circular outline and would fit in the funnel.

Visit

The nephews visited, and were entertained in the workshop. Each of them made or had a hand in making an item to take home. here they are:

There's a starship access pass made from antique drinks can aluminium, a name carved into wood and a glass tetrahedron.

A nice day's work.

Not My Hack

In the UK we have string pullcords on lights in bathrooms. These are usually in two pieces, joined with a plastic or metal widget that has a couple of holes, one in each end.  You put the ends of the two piece of cord in the holes and tie two knots to hold them there. then you hang a quirky thing off the end of the bottom cord. the plastic 'joiner' in a friend's house had broken, and he wondered if I could make a replacement. I thought about it for a while and made this:

Before  I had a chance to deliver the part, I was sent this photo of his solution:

This was just too good not to put up here. It's cheap and effective, and has the quirkiness required of a pull-cord. How long will it last? Who knows? But then, it doesn't matter, as you just replace it with another bottle...