Working on a previous project to make a prototype Pi UPS I pulled a number of salvaged lead acid batteries out of the scrap bin.

Battery Resuscitation through Desulfation
Battery Resuscitation through Desulfation

It quickly became apparent that the batteries were all flat and as each had a terminal voltage of around 0.5V they appeared to be beyond life ever again. Not surprising considering the number of years they had lived in the scrap bin without ever having a charge.

Initial attempts to put a charge into them and get them going again were without success. Even over voltage-ing them a little to get them started failed miserably. The best of them was taking around 10 micro amps. After leaving them on charge for 5 days or so the situation had not improved. So what were we looking at ? Maybe they had dried out, maybe the plates had fallen apart and were now mush or maybe being overly discharged the plates were caked irretrievably in insoluble hard lead sulphate crystals.

There are plenty of miracle cures for dead lead acid batteries and desulfation. Frankly I am rather sceptical of most of them. But for some reason I thought although slightly implausible desulfation was a fun hack to try. Chemical means to reverse the crystal build up were out as the batteries are sealed units. So it was time to rummage through the internet for ideas and then hit the scrap bins again for parts. The circuit I settled on is here Pulse Desulfator Doc. This formed the basis and the prototype as shown in the photo was a derivation of this.

Having nothing to loose other than a bit of time constructing and debugging it I set too to build it. The inductor was a hand wound approximation, the logic inverter shown in the schematic was replaced with a simple transistor based inverter using a 2N2222 NPN transistor and the mark space ratio of the 555 astabel circuit needed adjusting. Probably because the inductor value was a touch lower than it should have been. But in the end it appeared to be working.

Now the acid test (see what I did there….). From the picture you can just see the ammeter on the bench PSU showing the battery taking a charge of 200 milli amps. So success. It took 2 days of float charge plus the desulfator pulsing away to get this recovery. Over this period the input current could be seen steadily increasing, whereas before with a stable DC supply it had just sat there and done nothing. The open circuit voltage of the battery at the time of writing now shows 4.5 volts so there is a way to go yet. It could be a couple of weeks or so before the battery is as recovered as it ever will be. In reality I can’t see them ever being “as new” however a trick worth knowing about and trying when salvaging neglected lead acid batteries.

Not to self if trying this with an old car battery check the electrolyte levels first and be prepared to except that the plates could just be mush and the battery beyond recovery.

After advocating for a while that it is worth running up services on Pi Servers one at a time as needed. It occurred to me that we have no UPS to keep them going when the mains electricity drops out. We also have no way to prompt services to shut down in an orderly manor under the same circumstances. This gets to be more critical when we are running infrastructure services like RfID door access and a space automation MQTT broker.

An uninterruptible power supply for the Raspberry Pi
An uninterruptible power supply for the Raspberry Pi

Being as I am also running similar services at home I needed a similar solution for home. Sounds like a call to hack then, first stop was the junk and scrap bins, then a quick rummage through the spare bits left over from Chinese AliExpress shopping trips.

I found an ex UPS maintenance free lead acid battery that had sat in the scrap bin for too many years and a couple of these tiny 3A SMPSU DC-DC switcher modules that are incredibly cheap. The SMPSU modules can cope with up to 28V input and the output voltage is set by a small potentiometer. I also found a scrap laptop PSU that had a decent current delivery at under 24V. All in all the most expensive bits were the screw terminals that you can see from the picture I used to make conections to the board.

Lead Acid batteries have the useful property of being low maintenance and they will take a float charge providing you supply them with a constant voltage at the maunfacturers reccomended value. They will sit there on this float charge for as long as the battery will live. So after a quick rummage on the internet the first switch module was adjusted to provide a constant voltage at the manufacturers reccomended float value of 6.85V for the battery shown. The battery and input to the second switch module were conencted in parralel across the output of the first switcher. The ouput votlage of the second switcher was set to the 5.1V that is best to feed Pi’s with.

That then was the prototype UPS finished. When the supply to the UPS fails the battery takes over and supplys the Pi. When the mains supply comes back on the battery goes straight onto float charge and the Pi is running from the mains. Providing that the battery float voltage is less than the supply voltage and the Pi voltage is less than the battery voltage it all works. At 6V these thresholds are all a little close together and the UPS could do with a 12V battery and then adjusting to charge at that voltage instead. But this does work and the concept is proved.

The next task is to scale this up to run a whole shelf of Pi’s, with a mains high current SMPSU to drive the float voltage and supply the Pi’s, a salvaged car battery for the uninteruptible bit and one of these cheap tiny DC-DC SMPSU’s per Pi. But that is another article for another day.

Burnell Bot Breadboard

As part of our hacking the space project, we’re building a network of sensors and effectors in our space. Communicating over WiFi using the MQTT protocol, the idea is to make lots of data about the hackspace easily available for members to use in their projects, and to make it easy for members to add their own data streams to the space’s network of things.

One of these is the Burnell Bot, responsible for monitoring motion and light intensity, plus temperature and humidity. These data will end up being used to automate the hackspace’s lights and heating, as well as forming part of our security system. In the meantime, they’re flying over the WiFi in our hackspace ready for members to monitor and use however they want.

At its heart is an ESP8266-12E, sitting on a handy breakout board; you can see its silver enclosure covering most of the board, plus the etched WiFi antenna. This takes input from a BH1750 light sensor over I2C, a passive infra-red motion sensor that sends a digital HIGH signal in response to movement, and the DHT22 temperature and humidity sensor. Thanks to the support for ESP8266 in the latest Arduino IDE, the BH1750 and DHT22 are used via their existing Arduino libraries. A couple of warning messages pop up when compiling, but the code runs without issue. The motion sensor, of course, is monitored by simply checking the status of a GPIO pin set to input. Data from each sensor are transmitted over MQTT in their appropriate topics, subject to dampening (e.g. change in light level must exceed a certain threshold before being reported) and throttling of message rates.

Now that our planning permission has gone through (the downside of being hosted in such a great, historic building is dealing with its listed status) and we’ve refurbished our ceilings ready for the wiring grids to be installed, expect to see a few of these appearing in the space and start thinking of things to do with the data!

Personally, I want to add sensors for carbon dioxide, carbon monoxide, nitrous oxide and particulates, to keep an eye on our air quality and to try to get a sense of whether the reported effects of high CO2 / low O2 in classrooms (impaired concentration, amongst other things) affects our hacking. If you want to get involved in this or other projects, get in touch or just look at our calendar and turn up to a session!

sousvide controller breadboard

We have a couple of members interested in the geeky side of cookery, and our experimental foods day a little while ago was a great success.

Along these lines, I wanted to try sous vide cooking, a style of cooking in which foods are held at an accurately regulated temperature in order to favour some cooking reactions over others. It’s most commonly used when cooking meats, resulting in amazingly tender, juicy meat even from the toughest cuts. People with an interest in food chemistry — as a biologist by training, I’m definitely one of them — can also have a fascinating time experimenting with the cooking of, for example, the humble egg.

This project was to turn my slow cooker into a sous vide water bath. Along with several other SHH&M members, I’ve been playing with the ESP8266 microcontroller: a great little chip with easy WiFi connectivity, a decent number of GPIO pins and, fairly recently, support in the Arduino IDE, making it very easily accessible to anyone with some passing familiarity with using Arduino. As part of our hackspace renovation project we’re setting up a system of sensors and effectors that communicate using the excellent MQTT messaging protocol; there’s a great Arduino libraries for MQTT, so getting my sous vide controller to report its heating activity and my food’s temperature over WiFi was simple.

On the breadboard, you can see a ESP8266-12E with a silvery enclosure and the etched WiFi antenna. It takes input from a waterproof DS18B20 temperature probe using the standard Arduino library, which works perfectly with the ESP despite some warnings thrown up by the compiler. The ESP gets its power from a switch-mode (“bucky”) voltage regulator set to 3.3v; a second voltage regulator next to it provides 5v to the 240v AC relay. Both are fed from a 12v, 1A wall wart, not shown here. The relay, isolated from touch and moisture in its lunchbox housing, controls the power running through a short extension lead and happily accepts the 3.3v control signal from one of the ESP’s GPIO pins. The cluster of unused wires in the top right of the breadboard are in place to connect with my USB->serial board, in case I need to reflash firmware or debug over serial.

In use, the slow cooker is turned to “high” and plugged into the modified extension lead. The ESP8266 monitors the temperature in the slow cooker via the waterproof temperature probe and, by switching the relay, controls the heating. The logic is managed by a popular Arduino PID library, based heavily on their example code for relay-controlled systems.

Temperature data from about 20 hours of sous vide cooking
Temperature data from about 20 hours of sous vide cooking
PID algorithm output -- in each 10 second chunk of time, for how many seconds the heating element was receiving power, over about 20 hours of sous vide cooking
PID algorithm output — in each 10 second chunk of time, for how many seconds the heating element was receiving power, over about 20 hours of sous vide cooking

Data from the sous vide controller is reported over WiFi via MQTT, meaning that I could keep an eye on the two critical parameters (current temperature and how hard it was working to increase the temperature) using my laptop, phone, or, in principle, other ESP or Arduino devices connected to my flat’s WiFi. The excellent MQTT Spy even generates handy graphs from your incoming data in real time, bringing the food geekery to new heights. In future, also sending the data to something like data.sparkfun, to easily monitor and graph data when I’m out of the flat, should be straightforward.

The most important part of the post: The resulting food is amazing! So far I’ve only used it for meat, although there are plenty of interesting things like eggs and custards that I’m keen to try. Traditionally tough cuts of meat — shoulder of lamb, beef brisket — come out rare, tender, and juicy, with their distinctive flavours intact. More tender cuts, like sirloin steak, are done to perfection every time and, really, have to be tried to be believed. This was a quick and hacky project, but the results are fantastic. Definitely a success, and well worth making yourself.

The PID algorithm needs tweaking to improve temperature regulation to within a degree or two (easy but time consuming, and in the current warm weather I’m trying to avoid having a bath of hot water sitting in my well-insulated flat for hours on end), it needs to go in a case, and it needs a better control mechanism than re-flashing the firmware to change the target temperature. Getting the ESP to host a simple web page displaying controls — or even to just accept commands over MQTT — should be simple enough.

If you’re interested in learning to make this sort of project — or already know how, and want to meet up or work with others who do — come along to SHH&M! Get in touch with us here, or look at our calendar and just turn up to one of our scheduled meetings and introduce yourself.

Janine at Halifax

Aaron (of Oomlout fame), interviewed SHH&M member and trustee Janine about our hackspace and what we do here. It’s a nice writeup, with Janine giving a great introduction to our group and a few of the projects that we took along to the Halifax Mini Maker Faire. You can read the interview, and see some nice photos of the projects we took to Halifax, here.

As ever: if you’re interested in what we do, get in touch, or look at the calendar and just turn up to a meeting to meet us.

I have to apologise to the guys at the London Hackspace (LHS) in advance for this write up. I visited around a month or so ago and have only just got to writing it up. Whilst kicking around in London with a day to spare, at short notice, I contacted the London Hackspace and asked if I could come visit. Jasper replied pretty quickly and despite the horribly short notice was a very willing and helpful host. Many thanks then to Jasper.

The Front of London Hackspace
The Front of London Hackspace

The nearest tube station is Bethnel Green but the walk to the space through Tower Hamlets and past the Museum of Childhood is not very far and it was a pleasant day. LHS can only be described as huge. We were impressed at the size of Nottingham Hackspace but London is actually bigger. Not that size matters…. It leaves our hackspace feeling positively bijou, in true 80’s estate agent speak. The space itself occupies the entire ground floor of the A2E building as pictured, the equally large basement and the whole of the rear yard. Turning up as I did mid-week it was surprising to see how busy the space was with a number of folk working away on their projects.

Chillout Space
Chillout Space

Straight in through the door you walk into the communal chill out area. With a display of things made in the space, comfy seating and the kitchen area featuring a re-purposed fridge/beer cooler and beer on tap. More about the beer later. On the wall dividing this room and the next on this side is a sizeable makers library. Straight ahead through a pair of double doors is a substantial classroom area, with the biggest TV I have ever seen for presentations, apparently gifted by a very generous donor. This classroom area doubles as communal workspace for folk more software oriented when not being used as a classroom. Just out of shot on the left of the classroom is a passage way to the basement stairs and yard door.

Laser and handcraft area
Laser and handcraft area

Just off this passage way on the left hand side is the kitchen proper and toilets. Turning immediately left there is the laser and handicraft area, plus the full size roller shutter door to the large rear yard. The yard is just visible through the windows. The area is set up for a bunch of textile oriented projects with a good range of textile oriented machinery and facilities. As I already mentioned, considering it was a midday, and mid-week visit I was pleasantly surprised at how many folk were in the space working on their projects. To the left down the rear wall, again just out of shot is a small quite room/meeting room. Despite there being so much in this open ground floor area the feeling is very light and spacious. So far we have only walked in through the door and turned to our left.

Electronics Lab
Electronics Lab

If we turn left again so we are looking behind where we came in we can see the electronics lab. Just out of shot to the right is the 3D printing area, behind which is the quiet room we mentioned earlier. The electronics lab is well appointed with a range of test equipment, soldering stations and a whole bunch of components in drawers. There was a large 16 segment display made up from sticks of LED’s on the rear wall. What was starting to become apparent was that for a busy hackspace with a lot of equipment and ongoing projects it was surprisingly tidy. Before heading down to the basement to see what was in there, Jasper and I took a little time out to have a talk. London Hackspace seem to use IRC quite a bit for extended discussion out side of the space. Questions I had that Jasper was not sure about someone on IRC could help with. Access to the space is via RfID and 24×7. Interestingly enough being London most folk have Oyster cards or some other RfID tag. So the entry system works with these rather than sourcing tags for members to use. Re-purposing starting early. I was curious as to how they managed to have such a large space, especially n London giving the high property and rental costs. Jasper explained that although difficult and a bit of a struggle they do have well in excess of a thousand members. This does sound a lot until you consider just how many folk actually live in London.

Biohacking Lab
Biohacking Lab

Having talked a while we headed for the basement. To the right as you enter the basement area, and extending under the stairs we had just come down, is the biohacking lab, with the appropriate certification. I took this photo through the door glass not wanting to risk contaminating the workspace. Immediately behind me or to the left as you enter the basement is a large storage area with lines of shelving full of storage boxes for donated things to hack upon and personal projects. The basement area appeared to stretch on forever. Maybe it is a tardis like thing, bigger on the inside. Apart form the biohacking lab, this is where the dirtier and dust making work gets done. This lab is the first of a chain of enclosed areas leading from the main work area that make up the right hand side.

Personal Protective Equipment
Personal Protective Equipment

Moving along the right hand side passed a space that is currently a work in progress, we came to the essential stash of Personal Protective Equipment (PPE). As can be seen from the photograph a quantity of this was in use at the time. It was good seeing this in place and the shadow board shows how much is in use. Storing this equipment out of the main mess making rooms helps keep it clean and ready for use. There is a temptation to place it next to the place of use, with the resulting consequences. As appears to be the norm with hackspaces, PPE is provided and it is the members responsibility to select that which is appropriate for the task and use it. This point marks the end of the storage section of the basement and the beginning of the workshop proper.

Woodworking and Metal Bashing
Woodworking and Metal Bashing

Next in line are the two messier work areas for metal bashing and for woodworking. The metal bashing area has a sub-area set aside for welding and cutting operations. This area can be curtained off with a heavy shade curtain to protect the other workspace users from the effects of welding arc flash and showers of hot metal particles. The usual machine shop equipment is also available together with a power hacksaw. Always useful. The wood working area further along is similarly well provisioned with things like planer/thickeneser, lathe band-saw and workbenches along with dust extraction equipment. Keeping dust and mess levels down in a basement is a challenging pastime. Wood working is a particularly difficult, case in point.  The dust extraction was a standard blower and bag type set-up, that could perhaps benefit from a vortex separator.

End Right
End Right

Arrayed just outside the messy workspaces was a goodly selection of hand and power tools for use in either the cleaner workshop area or the messier one. Finally at the end of the right hand side there was a remaining open area with the spaces server racks and a collection of interesting robots.  To the right of the picture covered in plastic is one of the bench robots that were used as in the early stages of the Human Genome Mapping Project (HGMP). There were many of these used to brute force the sequencing of a single human genome using the wet bench technology of the day, these were principally used to save on the huge number of man hours that the repetitive tasks would otherwise of consumed.

Main Workshop Area
Main Workshop Area

Finally we take a step back and look down the basement taking in the main workshop area that lays down the length of the left hand side. Note the keep clear walkways taped out on the floor. A goodly supply of tooling and workbenches to suit most tasks. The dark door way just visible at farthest end of the room leads to the brewing area. In the brewing area there were stored various iterations of Brewbot and brewing paraphernalia. It was about this point in the tour that something that Jasper had mentioned several times sunk in. In talking about the biohacking, brewing, 3D printing or whatever maker thing etc. Jasper had refereed to them as groups. I guess with that many members and that much space a degree of grouping must take place. Being a small, compact hackspace Sheffield is still pretty homogeneous. We tend to refer new folk to members as individuals that have the skills or interests in common, as opposed to referring them to a group with skills. It was interesting to see how the social structure had evolved and coagulated around specifics. It is almost like a mini town or ecosystem with groups making not just for themselves but for the hackspace at large. The brewing group was a particular case in point, considering their produce was made available to the hackspace in the chill out area upstairs. This left me thinking, this is what community’s and society used to be like before the disruptive model of mass manufacture and mass consumption came to prevail. It was not enough to just sell something, it had to be made as well.

All in all then, wow, what a hackspace. I could do with a visitors pass to drop in the half a dozen times a year I am in London, with time to spare. It would sure beat hanging around the usual touristy parts of town and save me the money spent on impulse buys in Foyle’s Bookshop. A “must go see” for makers visiting London then, and a “must be a member” for makers working, living or spending extended time in London. The number of pictures do not do it justice.

Busy times here at SHH&M! A few snapshots of things our members have been working on recently in the hackspace:

Project Snapshots

 

 

Some of the stuff we’ve been up to lately includes:

  • Upgrading one of our 3D printers
  • Building comfy deckchairs for slow afternoons in the coutyard
  • Ultra-lightweight aircraft for indoor flying
  • Building and upgrading our network and servers
  • Running workshops, including amazing ice-cream!
  • Arduino and ESP8266 programming
  • Prototyping a pocket-sized (taking-to-the-pub-sized!) boardgame
  • Learning woodworking and joinery
  • …plus our high altitude balloon project, catching up with friends and being inspired by cool projects at the Halifax Mini Maker Faire, further work on our RFID entry system, and a hundred other things that I don’t have photos of.

 
It’s been another good month, and it’s only going to get better! If you’re interested in joining in, at any skill level (NB: “any” definitely includes “complete beginner”), get in touch or look at our calendar and just turn up to a session!

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This Saturday we made dry ice icecreams and sorbets, had a chocolate truffle making masterclass, and experimented with molecular gastronomy to make burst-in-the-mouth fruit puree spheres. Plus a BBQ and our normal hacking session alongside. An exhausting, brilliant day!

For the dry ice icecream, we made a couple of batches of simple custard, cooled to around room temperature using a dry ice bath (because why not?):
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…then everyone started adding their own mix of flavours, before quickly beating in dry ice converted to a powder in a finely calibrated process of Janine frenetically bashing it with a hammer.

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Verdict: Amazing icecream! My personal favourite was the Glenlivet whisky icecream, but they were all (vanilla, cherry and chocolate, chocolate mint, Rum, Kahlúa) fantastic.

Andy’s Kiwi, Apple and Lime sorbet was similarly great. The fizzy taste from the dry ice gave it a really delicious edge.

Sarah ran our truffle making masterclass — deliciously messy, with fantastic results! Another great mix of flavours tried out — my personal favourite was chocolate and Henderson’s Relish. Because I’m pretty sure it’s illegal to cook anything in this city without at least a splash of Hendo’s.
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Finally, a bit of molecular gastronomy. We got hold of some calcium lactate gluconate and sodium alginate to try out “reverse spherification”. A simple berry puree was mixed with the calcium salt, and dropped into a bath of sodium algniate, for about 2 minutes. This grows a thin layer of flavourless gel around the droplet of fruit, making a burst-in-the-mouth fruit sphere! Well, sort of sphere:
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Never mind that they look like monkey kidneys, they were delicious, a really fun texture, and surprisingly simple and enjoyable to make. Lots of finesse needed for perfect spheres, but definitely worth trying yourself!

Finally, our incipient tradition of a BBQ and a few beers in the sunny courtyard before cleaning up and heading home to our respective food comas.

Thanks to everyone for helping out! If you missed it (maybe you haven’t come along to a meet yet?), you should’ve been there!

PS: There may have been some further gratuitous playing careful and sensible use of the dry ice:

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…but our lips are sealed.