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.

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.