Yesterday we completed our prototype control panel for the HERMLET project. Rather than build a final unit to put on the machine, we decided to iron out design issues by building a prototype as a step to a final product.

This was a good idea, because it allowed us to test and learn about a few things such as:

• the best way to attach panel artwork without destroying it
• how important it is to select the right components to simplify construction
• how easy it is to use a laminator for toner transfer compared to using a household iron.

Panel artwork

We laminated the artwork and glued it to the panel. We used forstner drill bits to cut 12.5mm holes for the switches and it seemed logical to use these to cut the holes on the artwork as well. We found that the artwork had a tendency to tear rather than cut neatly. A work around might be to glue the print to the laminate prior to laminating - but this seems messy. Another idea is to simply use paper, glue it to the panel and hopefully the glue will prevent tear-out. Yesterday we used a scalpel knife to cut out the larger holes. The 3mm holes for the LEDs remain a problem - how do we do that neatly?

(Maybe we need to find a leather punch of the right size ...)

Component selection

The switches we used were ones we already had. This seemed like a good idea. In earlier construction we soldered fly-leads from switches to circuit boards until I had the bright idea that we could direct solder to make things easier. The switches were designed with lugs rather than going through PCB holes - so the next bright idea was to solder them to the copper side. This might have been reasonable, except that it got to be a complex process dismantling the switches, soldering the tags onto the board at once, then reassembling spring and contact components and panel all at once. Not only was this difficult to do in terms of space, it means it is nearly impossible to solder the LEDs in place - something that really needs the panel in place first to set soldering depth.

We persisted despite these complications. We do not need to install the LEDs at this point, but the switch panel is now complete and operating as designed.

Laminator toner transfer

Yesterday we also visited our local Jaycar electronics shop and found some cheap and neat coloured switches that are true PCB mount. We even redesigned the circuit board and tested out the laminator process to transfer the toner onto the board. (See recent blog on PCB making for details). It was so simple to use that I don't think we will use an iron again.

Switch Panel Circuit

The circuit uses a resistive ladder to give a different output voltage for each panel switch. This means that a single ADC input on the microprocessor is all that is needed to decode a large number of switches.

For a good article and circuit diagram on this, see ADC keypad article.

Next steps

With the panel ready for work, a simple LCD setup and a breadboard circuit using our picaxe 28x1 means we can begin writing and testing the control circuit for HERMLET.

It's all about the beer ...

The Dortmunder export lager has been cold conditioning for a week now and was very promising out of the fermenter. The Munich Helles that we brewed a week ago is also coming along nicely. Our next brew will be a North German pilsner. We need to stock up on our lagers for the warmer weather ...

Once the HERMLET concept gelled, it was hard to believe how simple the machine design is.
(Note to self - must test the idea in real life)

Description

The blue rectangle represents a single vessel (or tun), and in our case it will be a regular 20 litre stainless steel urn. We picked this up at a Trash 'n' Treasure market for about $20.

The grey rectangle labelled 'Mash Tun' is a second stainless steel container that sits inside the urn. This is a 12 litre cheap Chinese import stainless steel cooking pot. We picked ours up at the local cheap import shop for $7.50. Think of this configuration as a double boiler. When mashing, there is liquor both inside the mash tun and outside the mash tun. The outside liquor helps to keep the inside liquor warm.

The plumbing is kept as simple as possible. We intend for HERMLET to be a recirculating system because we like the temperature control we get this way. An even simpler system could be made without the pump and recirculation plumbing, but this would limit the flexibility, particularly with step mashing.

The liquor comes into the urn at the top left on our machine (simply because the urn already had a ready made hole for our plumbing). There is a single valve that allows the wort to be drained into a fermenter located at the bottom of the urn. Configure this valve as you would for a kettle drain valve.

Process

With the mash tun in place, the urn is filled with sufficient liquor to mix with the grains. This liquor is then heated to strike temperature. Grains are then poured into the mash tun and mixed with the liquor (dough-in).

Liquor is recirculated through the grains to regulate mash temperature. Liquor temperature is controlled with the urn heating element. Liquor at the bottom of the urn is pumped back into the top of the mash tun, draining slowly back through the grain, out through the false bottom and back into the urn. (The false bottom is depicted in the picture as a black arc).

Step temperature mashing is easy with this method as per HERMS and RIMS configurations.

Once the mash is complete, the mash tun is slowly lifted out of the urn and the remaining mash liquor is allowed to drain into the urn. Our machine will have some kind of gantry and winch system to allow easy lifting at this stage. The larger the brewing system, the more weight will need to be handled. Because this rig is small, we anticipate lifting no more than 6-8 kg of soggy grain.

The urn now contains wort that is diluted to the required volume and then boiled with hops added when needed.

Pros and Cons

Advantages

• The mash tun does not need to be an insulated vessel.
• The outer vessel acts as both hot liquor tun and kettle
• Only one heating source is needed
• Simpler requirements for controls
• No need to heat separate hot liquor for sparging
• Plumbing is very simple - 1 inlet, 1 outlet, 1 closed loop

Disadvantages

• Lifting the mash tun may pose problems, particularly in larger systems
• The system is (likely to be) less efficient than a three tun configuration
• Topping up the kettle with liquor prior to boil is likely to increase the time to reach boil

Other design notes

The origins of this design are manifold. There is the inspiration from the "brew in a bag" movement on the Aussie Home Brewer web site, and PistolPatch needs a special mention.

Then there is the "no chill" movement on the same web site who believe that there are many advantages to dropping hot wort into a storage container without flash chilling. As we face even tougher water restrictions in Melbourne for the summer ahead, this seems like a really good idea.

Then there are other cool inventors such as Gerd who built a most beautiful and intricate brew rig before even making any beer. He provided the inspiration to move from "brew in a bag" to this system with a mash tun inside a kettle. Gerd's brewing machine

Then there is my brew-buddy Leah, who through losing most of the function of her left arm has caused me to think about simple ways to make beer without all the heavy lifting and cleaning that comes with 50 litre kegs.

One of the features of the mash tun will be a tilt mechanism so that once it is lifted mechanically, the grains can easily be removed from the vessel as well.

Oh, and I'd like to thank my Dad who was also a keen maker - I now understand why he spent so much time in the workshop. I wish he had access to the tools and equipment that I have.

Conclusion

OK, it may be pushing things a little to claim this as a one vessel system, but it is pretty close to it. Anyway, as a maker who carries the curse of "What if I just add this extra bit of functionality/complexity...", I'm really happy to have finally designed something that in its essence is so very simple.

The proof is in the beer tasting ...

Oh, and we intend to do a "Race against the machine" brew-off between HERMAN and HERMLET when both machines are functional. S W E E E E T!