Vivarium controller MKIII  

The basic prototype using veroboard had been running without any issues for around 5 years, however it only records the hot spot temperature, and shows no other data. I really needed to read the humidity in the enclosures so started playing with AM2302 sensors with a view of adding these in addition to the DS18b20's used to monitor and control the heaters. After a few posts on the PicBasic Pro forum, a member (Ken) in Texas contacted me and in a joint venture we produced a library file for these range of sensors. Ken would write the code, and I would test it in the real world, and the provide feedback and suggestions until the code was ready for publication.

So now I had the hot spot temperature, low spot temperature and humidity for all four enclosures to display, along with time and set points. There was no way this would fit on a normal 4 x 20 LCD display, so I looked at using a 128 x 64 graphics screen, and to make things simple used a serial module that already contained built in fonts and graphics.

After lots of late nights (well early mornings as Ken was 6 hours behind us in the UK) we also modified the communications between the PC software and the controller. The original prototype used normal serial communications via a long cable, but I wanted to add some form of wireless capability, and to keep it simple chose Blue tooth. An HC-05 module and back board was purchased from E-bay for less than £5. The hardware was easy to implement as it used the standard TX and RX pins from the PIC, and simply replaced the wire, with the PIC code hardly needing any modification. But the PC application proved more troublesome, partly down to how it was originally written. Again Ken came to my aid as he had lots of experience with Visual Basic, and Liberty Basic that I was using is very similar. In the end a good 50% of the code that handled the communications was re-written.

Once I had the project running on the breadboard for several days I started designing the schematic and producing the board layout. I opted for splitting the output stage and main board into two as this means I now have a general SSR driver board that can be used in future projects, especially as the PCB house in China has a minimum of 5 of each boards. Each outlet is also fused by a quick blow 2A fuse.

This MKIII unit has now been running since October 2015, and it's performing very well. The blue tooth coms is a life saver as it saves so much time when setting up the controller

 

Single Channel Controller

 

I've also built a single channel version. It does everything the four channel version does, but just as a single channel pulse proprtional stat rather than four stats.