Tuesday, December 21, 2010

Housing and heat

First purchases were a cheap aluminium brew pot, some timber and hot water element.

I wanted a stainless steel pot, but could not find one I liked of the right size locally. I will order one online, but to get me started I will use the aluminium pot.

Here I'm using a Home Depot pre made 30A drier lead on a hot water system 240V 3500W element. I got a small galvanized electrical connection box, and did a cut-n-shut to make it smaller. I miss my MIG welder, I'm justing using a small MAPP gas torch to braze the two parts together here.

I tapped some M3 threads in the outer part of the element to mount the gal box.

Here you can see the inside of the pot. The long loop is the heating element. I have a 1" stainless steel socket holding in it place. I will cut it in half (the line marked) and silver solder this into my stainless steel brew pot when I get it. The other half I may eventually solder into our 8-gallon brew pot for mounting an element there.

Above that you can see the stainless steel thermowell. I also plan to silver solder a socket in for that.

The main housing is made out of 3/4" hardwood ply. Here you can see some ball bearing draw slides mounted on the back of it. On this will run another piece of ply for the crane part of the bag lifting piece. These are rated to 75lbs.

You will notice I didn't mount them both on the same side. This is so that neither of them has to take all the weight at full extension.

The crane slide works well enough.

I will be using a wiper motor and some 3/8" threaded rod as a lead screw to move it.

You can just make out the micro switches at the limits of the slide.

The power electrics are nearly done. Pretty straight forward. Two sturdy gal power boxes brazed together to form one bigger box.

One 40A SSR in line with the element mounted inside the lid. The 3500W element should only be drawing 15A, so hopefully the SSR can handle it. The only issue is power dissipation. SSRs can drop 1.6V, which will mean 24W of heat to dissipate. I have chunky PC CPU heatsink/fan combo to go on there which it why I mounted it inside the lid. And probably won't be running the element at 100% duty cycle.

The main black box is just a 240V 30A socket. The lead plugged into it a 30A pre-made one that goes straight to the pot.

You can just make out a black bot inside the gal box. That is a $10 12V 6A ebay LCD power supply. This will be used for running the motors and the main CPU.

Starting to put together the electronics.
The breadboard is soldered to a header that plugs directly into the board. Unfortunately that does not give enough I/O pins, so I have the flying lead down to other header on the bottom of the board.

Next will be to populate some driver transistors and connectors.

There is a DS1820 dangling that I have used to bring up the code for talking to that.

I'm hoping to get a free wifi adapter as part of the design contest. It plugs into the header just left of the breadboard which is why I didn't touch that connector.

I'm sure many of you can see where I'm going with the design. Essentially Brew-In-A-Bag. A simple crane for automated lift-and-move of a pot with main holes in it (the "bag"). A mash stirrer will run on top of this "bag".

I initially started with a design of the pot moving from out under the "bag", but I think the off the shelf ball bearing draw slides makes viable the crane part moving.

The real challenge for me is that I'm away from my usual tools and home workshop. I'm slowly building up a new set of tools here, but am particularly missing my MIG welder, grinder and drill press.

I'm still not sure where to mount the CPU board yet as the LCD needs to visible, and yet out of the way of steam/water. The hop dropper could also be tricky to place. It needs to not interfere with the crane and bag.

Next I really need to get a hold of some wiper motors to do the lifting and moving.

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