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.
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…
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!