Another 'Round Tuit' Off the Pile

Not a bad speed for me - parts purchased near the end of Spring finally assembled last weekend. What was it? Just a controller for the under gravel heating for my Lithops (Living Stones). They live in my unheated conservatory where it can go below freezing in the depths of Winter. Last year I had a simple system which was difficult to set to the temperature I wanted. I found an excellent bit of electronics on eBay which would be versatile and easy to set. This is the front panel I made for the new set up:



On the left is the new electronics showing three temperatures. In the centre, in red, is the actual temperature next to the plants. Either side are the temperatures which can be chosen using the small buttons below each display. At the moment it is set to switch on the under gravel heating pad when the temperature drops to / below 8C and to switch it off when the temperature has been raised to / above 12C. The other display (in blue) just shows the voltage being used by the display.

There is little else inside the box:


Besides the aforementioned displays the block in the centre of the box is a solid state relay. Basically a switch with no  moving parts. With it the low DC voltage from the temperature controller can safely switch the mains voltage which goes to a couple of sockets mounted on top:


No. The displays haven't gone haywire. They are multiplexed, each number is lit in turn but very rapidly so to the the human eye they appear lit all the time. The camera shutter is so fast it only sees the bits that are illuminated at the moment a still photo is taken. How then did I get the first photo? I took a short video. Each frame is taken much more slowly so catches everything. I just grabbed one frame from that.