It just seems wrong to take a nice stainless steel urn and drill a hole in the bottom of it. There is an old adage amongst carpentry to measure twice and cut once, so we made sure the hole was going to be in the right place ...

The hole is actually the drain point from the kettle into the pump for dough-in and recirculation - this is the path from the kettle into the mash tun which will sit above the kettle. We want the kettle to sit neatly on top of a pressure fitting, and simply connect to the pump by putting it in place. For this to work, things have to be solid and in the right place.

Once the top board of the control box was cut to size, we worked out exactly where we wanted the kettle to be in relation to the pump. After some checking and double-checking, the hole was drilled and filed out, and the fitting installed. The photo shows the under side of the kettle. with fitting coupled to its mate.

We worked out the right height for the connector below the kettle, and added a block of timber to keep it solidly in place.

The photo below shows the two nearly coming together. The 'O' ring on the top connector fits snugly into the bottom connector and the kettle weight holds it in place.

We have yet to test it, but we're confident it will work ok without leaking. The connectors are standard brass garden hose fittings available in Australia. The locking part was removed from the bottom connector by removing a circlip.

The next few things on our hardware do list are:

• fit the pressure sensor into the bottom of the kettle
• connect the kettle to the pump inlet
• install mash tun supports and hang the mash tun on them
• connect the pump outlet to the line running up the kettle to the mash tun

The next few things on our electronics do list are:

• finalise the controller schematic, etch and build the board
• finalise the mash tun connector board, etch and build it

And on the coding list:

• code some simple manual control routines to get the machine running

With a couple of brews safely fermenting away in the background, we've had some time recently to return to the HERMLET project.

A lot has happened in the odd spare minute over the last few weeks. I have been going over the notes that sparked the machine idea and weeding out some of the complexity (as per the Simplicity Cycle). Some coding pressure has helped speed up this review, because I needed to work out detailed control procedures - which means making decisions about which features the machine would end up with.

Having gotten that far, it was time to make something.

We re-gathered the various bits and laid them out on a portable work horse to see things in 3D. From there some of the parts were put into place, like the float switch as shown below. This switch will make sure the heater cannot operate unless it is covered with liquid.

We then made a plan to visit the local Trash 'n' Treasure market to look for a suitable stand for the machine. It needed to have wheels for portability and stand about 600 mm (2 feet) tall. Impatience got the better of us though, and we paid a visit to the local hardware warehouse first.

There we discovered a suitable tool chest with wheels and great storage for all things brewing. The chest will be home to brew water chemicals, yeast nutrient and tools like our digital scales and refractometer.

Once this was assembled, it was back to imagining where all the bits might be...

The photo above shows some spacers that will form a frame for the control gear. The photo below shows a rough location of the power supply on the left and the pump towards the rear. The plastic tray underneath the pump will be our simple leak detector.

The leak tray is there for a good reason (it is not because we don't think we can put in plumbing that does not leak ;-). One of the key design features is to make the machine easy for Leah to use. She has restricted use of one arm so we will be installing an easy connect/disconnect system for the kettle. The kettle stands immediately above the leak tray as per the photo below. Because the pump and recirculating path is low pressure, we think we will be able to use simple brass garden hose connectors (see bottom photo) as press fittings between kettle and pump. 

This means that the connection will hold through the weight of the kettle and an 'O' ring only. A transparent leak tray will provide an early warning in case things go awry.