LowBrau – Screen Protector

March 8, 2013

I am trying to keep the controller box as water-tight as possible.  Although I don’t expect it to be hosed down, I can see that with an inherently liquid-based enterprise it is entirely foreseeable that it’s likely to get the odd splash.  At the moment the LCD module simply pokes through a hole in the box, so it needs some sort of cover to seal it all up (as well as provide some knock protection).

All I really want is a rectangle of thin clear plastic.  So I went looking for some trash that could be repurposed.  My first attempt was using an old CD cover.  This proved too flimsy – once the edges were removed it was quite floppy.  In the end I used the plastic from a box of ex-Christmas Ferrero Roche.  I’m sure that an old iPod/iPhone box would work even better (not that I have many of them lying around).

The best way to work the material is to rough cut the sides off to leave a single flat sheet of plastic.  A hacksaw or Dremel cutting wheel works well for this.  To actually cut the final edges of the rectangle (ie the fine work) the best approach is one similar to glass cutting.  Score your line a few times with a craft knife and straight-edge.  The bend to snap along the score line with some flat-nosed pliers.

lowbrau - screen protector cutting

This way the rough stock can be made properly square (as in, given proper 90 degree corners) and the results are quite accurate, straight sides.  Any jagged edges can be knocked back to smooth with a light sanding.

Then all is needed are a few holes for mounting screws and (later) a little silicone sealant.

lowbrau - screen protector installed

As you can see in the photo above, my box has a little dot imperfection where the injection molding has taken place.  I may end up sourcing a better piece of stock and remake using this one as a template.  If that were to happen this would actually be a very quick operation to duplicate the two (this one took about 5 minutes to make).  Or I may just live with what I have…


LowBrau – Low Voltage Wiring

March 6, 2013

Now that the major components have been fitted to the front and back halves of the controller box it’s time to start wiring up the low voltage components.

lowbrau - low voltage wiring front

I started by installing an earth wire (green) to the LED bezels – as any conductive surfaces on the exterior of the box should be properly earthed.  Next the cathodes of the LEDs were bent together and soldered in place with a ground wire (black).  Each anode then got its own signal wire (orange).

Next the navigation buttons received their common ground (black) and individual signal wires (white/grey).  Each signal wire not only connects to an input pin on the arduino, but also connects to the 5V rail via a 10k pull-up resistor.  This circuitry, however, I will deal with soldered directly on the proto-board.

After this my LCD needed its leads, so I soldered together the connections in the pin header sockets using red for 5V, black for ground and yellow for data lines.

lowbrau - low voltage wiring back

On the back panel the SSRs need their signals and common ground.  As the signal that triggers the SSR is physically the same pin that lights the respective LED I chose to use orange for these lines too.

All these various lines then connect each component to the arduino via a shield made from prototyping board.  I took strips of pin header and pushed the pins all the way through their black plastic strip so that I could keep the solder side towards the arduino.  Unfortunately the second bank of digital connections (data lines 8 to 13) are not aligned with the grid of the proto-board, so they need to sit on their own little board.  This is a slightly annoying feature of the way that the arduino has been designed – and the cynic in me wonders if it’s to create a market for people buying prototyping shields!

lowbrau - pcb

The main items that live on the circuit board are 5V, 12v and ground buses; the button pull-up resistors; the LCD contrast trim-pot and the buzzer transistor.  As a result, none of the circuitry is mind-boggling complex and a custom printed PCB is an unnecessary expense (although it would make for a far quicker job).

Once all this wiring had been completed it was time to flash the arduino and see if it all works.  And success!

lowbrau - lcd first run

Currently the LCD, navigation buttons, and LEDs are fully functional.  There are header pins for the SSR signal wires to plug into (allowing both halves of the box to split apart) and the transistor for the buzzer needs to go in.  My temperature probe has not arrived yet, so that only has some loose wires (purple) awaiting it.


LowBrau – Front Panel Hardware

March 5, 2013

After mounting the SSRs and heatsink to the rear half of the waterproof control box, I figured I’d plough on and fit all the front panel hardware.  As such this post doesn’t really have a lot of earth-shattering content, but I will run down a few of the items that make up this part of the build.

lowbrau - front panel inside

The green circuit board in the centre is the liquid crystal display which will provide the main interface for the user.  This module is a common HD47780 ($2.40) which is easy to interface with digital circuits – indeed arduino has a library specifically written to do just that, you simply need to specify which pins you have connected each of the LCD terminals to and away it goes.  I soldered some header pins on so that I can easily disconnect it from the rest of the controller wiring, should I need to.  I will need to work out how to protect the screen from knocks and liquid splashes, but that’s a challenge for another day.

Beneath the LCD sit four control buttons.  These provide the navigation inputs to allow the user to control the LCD.  I chose waterproof buttons, which don’t seem to be widely available cheaply so these ended up being close to $5 each!  Feels a little unreasonable but cannot be helped.

To the immediate right of the LCD are two LED indicators.  These will serve to provide a visual indication of the state of each output relay (ie whether or not the pump or heating element is switched on).  This might prove important in avoiding accidentally leaving the heating element on while the brew vessel is empty.

On the left side of the box is a power transformer to provide a 12V DC source for the arduino and buzzer to run off.  Again, this common 1A supply was quite cheap at only $7.50 delivered.

On the right side of the box is an IEC power socket to provide mains power to both the transformer and the heating and pump SSRs.  This socket was free because I simply unscrewed it from an old PC power supply – I can’t imagine why anyone would ever buy these new!

Finally, here’s a look at the front panel…

lowbrau - front panel hardware

I think the layout is looking fairly clean and functional.  It has to be said that there’s isn’t much room for variation because the inside of the control box, once all the components are in, is going to be very tight for space.  The navigation buttons might look a little cramped but they’re entirely usable, line up nicely with the LCD and free up plenty of space on either side for more components inside the box (for example the transformer sits under the blank space to the right of the LCD and buttons in this photo).

I certainly find cutting the holes a bit of a chore.  All the circular components are a dream, but the square holes of the LCD, SSRs and IEC connector all involve a disgraceful amount of filing to get them right.  I’m sure there must be a more efficient way, but I have yet to discover it!


LowBrau – Solid State Relays

March 4, 2013

Work has commenced on the LowBrau controller with the installation of a pair of solid state relays (SSR) into a polycarbonate waterproof electrical box.

lowbrau - ssrs

As the name suggests a solid state relay works very much like a standard electromechanical relay – using a low voltage, low current signal to switch a high voltage, high current on and off.  Where a mechanical relay uses an electromagnet to physically make and break the contact of a switch a SSR acts more like a transistor to achieve the same outcome without any moving parts.

lowbrau - SSR circuit

Inside an SSR there is a light operated switch consisting of an LED operated by the signal and a thyristor switching the load.  This arrangement has some excellent advantages.

First, the LED side is low current and TTL which means that the SSR can be connected directly to the arduino without any need for transistors, resistors or any other components.

Second, the SSR can be switched incredibly quickly (milliseconds to microseconds) which means that pulse width modulation (PWM) allows for not only an on or off state, but also to vary the effective output level of the load by rapidly oscillating and varying the gaps of ‘off’ between the spikes of ‘on’ – in my case this will allow me to tail off the heat of the element to avoid overshoots.

Third, the SSR is fully opto-isolated (meaning that there physically is no connection between the low voltage circuitry of the controller and the household supply) and does not suffer from any of the back-EMF noise issues of electromechanical relays.

Lastly, my SSRs were quite cheap (~$3 each) so I bought two: one to modulate the heating element and the other to switch the pump.

Unlike a standard mechanical relay, though, SSRs do produce a fair amount of heat.  This will be particularly so for the SSR controlling the heating element because it will be performing rapid switching on a 2.4kW load!  To deal with this the SSRs have been mounted to a large aluminium heatsink which covers the back side of the controller box.  Thermal grease between the SSRs and the heatsink ensure good transfer.

lowbrau - heatsink

It is also worth noting the importance of properly earthing the heatsink (along with anything else conductive on the outside surface of the control box) as a loose connection could easily turn the aluminium heatsink into a dangerous conductor.


Biscuit tin guitar: attaching body to neck

February 26, 2013

When Mary’s found-by-the-side-of-the-road guitar fell apart, I thought it time to give it a third lease on life.  I’ve seen a few people make oil-can banjos, so I thought I’d have a go at a biscuit tin guitar.

A tin does not have the structural rigidity to take the tension between either end of the guitar caused by tuning the strings up to pitch.  My solution was to lengthen the neck of the guitar by adding a wooden spine.  The tin would then float over this.

The other consideration is ‘scale length’.  This is the distance between the nut and the bridge of the guitar, and is important because it can vary from instrument to instrument and each of the frets has been specifically calculated as a subdivision of this overall length.  This should be measured before you hack up the donor guitar, but if that’s not available you can measure the distance from the nut to the 12th fret and double it.  Once you know the scale length (mine was 25.5″) then you can start thinking about what sort of size can you will need to allow for the right scale length and a little extra so the bridge isn’t right on the edge of the can.

The first step (after liberating the neck from the old guitar body) was to cut some lengths of wood for the new spine.  An L-shaped notch is made the length of the can so that the top surface (soundboard) of the can will not touch the spine underneath and therefore be free to vibrate.

tintar - spine

I then glued the three lengths together to build up the thickness.  I also radiused the front edge where the can meets the fretboard, because my can has a rounded end.

tintar - spine laminations

Next the spine is glued to the fretboard.  This connection is going to need to be able to take quite some stress so I epoxied it and added a couple of screws.

tintar - fretboard

Then the tin goes on.  A hole is needed on the front edge for the spine to slot through.  If it is cut in such a way that it creates flaps that fold in not only will those flaps centre the spine in the hole but a screw through one of those flaps will also hold it in place.  When you’re happy that the fretboard sits parallel to the surface of the soundboard screw the end of the spine to the end of the tin can.

tintar - tin mounting

Coming up… tail piece, bridge, strings, music!


LowBrau – Concept

February 6, 2013

I have been toying for some time with the idea of shrinking my brew rig.  Don’t get me wrong, it’s a fantastic setup and it produces excellent beer – but I am conscious of the fact that it takes up an awful lot of room.  At the moment that isn’t such an issue as it lives on its wheelable frame in the carport, but what if I were to move?  That would spell the end of my brewing.

Then last weekend I went to check out an new piece of gear that a friend has just bought – a Braumeister.  This device is a single-vessel brewing system that is electrically heated and has a programmable control box which allows for a highly automated brewing experience.  It can be programmed to step the mash through 5 temperature points, alerts the brewer when various key stages are completed and keeps track of hop addition timings.  It produces 20L batches to a max OG of 1.057 and can quite happily brew indoors (for example on the kitchen counter!)

lowbrau - BM

This little beauty does come at a price though – $2500 (AUD).  Ouch.

So after seeing how it works I got thinking… The basic principle is that of a pot-in-pot design, where the inner pot (or malt pipe, as Speidel call it) is filled with grain.  The top of the inner pot is open and covered with a mesh and retainer.  The bottom of the inner pot is also open (hence tube) and covered by mesh but it seals to the bottom of the outer pot.  This allows a pump to suck wort from the outer pot and inject it to the bottom of the inner pot, pushing wort through the grain bed and letting it overflow out the top back into the outer pot.  In the gap between the outer and inner pot walls is a low density heating element and temperature probe.  And that’s basically it.  Once the mash is complete the malt pipe is raised to drain and removed then the heat is ramped up to commence the boil.

lowbrau - BM cutaway

None of this is particularly complex in either operation or construction.  And this makes me think that I could produce my own, low-cost homage to the Braumeister – the LowBrau!

Here are some of my design aims:

  • built using cheap, easy to source components
  • no welding required
  • same or greater capacity – both finished volume and OG
  • use arduino for control
  • facility for step mashes and general hands-off brew automation

What I don’t plan to do, however, is make a slavish clone of the Braumeister.  I want to make something out of the materials that I can source, that doesn’t require sophisticated or high tolerance machining and can provide the functionality/performance I require to suit my brewing style.  I think that the Braumeister is an excellent blueprint for not only what is possible but also what works for them – and as such will serve as an excellent point of reference when producing my system.


Counter-Pressure Bottle Filler

January 25, 2013

The latest addition to the brew gear is a counter-pressure bottle filler.  Sure, kegs drastically reduce the workload when compared with bottling a whole batch – but it does mean a sacrifice in portability.  Plenty of people hear of all these wonderful brews that are on tap 24 hours a day at my house, but unless I’m prepared to lug a keg around to their afternoon BBQ (which does happen on occasion) these things remain folklore.  This bottle filler allows small runs of beer to be filled off a keg and into bottles.  Also, because the beer is already carbonated it avoids the need for a secondary fermentation in the bottle – totally avoiding sedimentation and giving complete control over carbonation levels.

bottle_filler_labelled

It works by pressurising the bottle to be filled with carbon dioxide at the same pressure as the keg.  Then beer is allowed to flow into the bottle by allowing a small amount of gas to escape from the bottle – ie as the gas very slowly leaks out of the bottle it is replaced with beer.  During this whole time the pressure level is maintained in the bottle so that the carbon dioxide in the beer cannot come out of solution and the beer start foaming.  The filler rig is removed and the bottle capped.  As the beer is cold, the gas lost from the beer during this stage is minimal.

As you can see from the photo above the amount of head formed during filling is essentially non-existant.  It doesn’t take much imagination to picture what the bottle would look like if I simply tried to fill it from a beer tap or gun – it would be at least 50:50 foam to liquid!

The process is really simple.  First the valve at the top points towards the gas side.  This allows gas into the bottle and I purge the air inside by allowing a small amount to leak through the pressure relief valve.  The valve then gets turned to the liquid side and beer starts flowing into the bottle.  The PRV gets adjusted so that beer flows into the bottle at a sensible rate.  As the beer nears the top of the bottle the valve gets turned to the middle (off) position.  The PRV is opened to release the pressure, the filler removed and the bottle cap swiftly put in place.  All this can be done quite comfortably from a chair by one person, with empty bottles on one side and full ones on the other.

The filler itself is full stainless steel in its construction and at $50 I think it’s a bit of gear that every kegger should have in their arsenal.  Clean-up is very easy too – I just blow the excess beer out of the beer line, pass some water through it from a water tap and give the rest of it a clean in the sink.

One last word of warning: I always use my bottle filler wearing safety glasses.  On the one hand the filler should be putting the bottles under less pressure than a secondary fermentation and should too much pressure occur the filler should pop out of the top of the bottle neck, but for the sake of a simple pair of safety specs it seems an easy and unobtrusive way to protect against what would be a total disaster.  Imagine a small flaw causing a glass bottle to totally let go in your face!