Christmas tree water sensor gets an upgrade and a fancy new box


[Eric Ayars] has a nice cast iron Christmas tree stand at home, but the only drawback is that the stand makes it hard to see just how much water is available to the tree. Last year we covered a small gadget he created to help keep tabs on the water level, but as several of you predicted, the system eventually failed.

His previous solution used copper plated proto board to sense how much water was in the stand, but the leads corroded in about a week’s time. With Christmas just around the corner, he decided to give things another try.

His revamped water level sensor relies on measuring capacitance changes in a copper strip board when under water rather than detecting a complete circuit like the previous model. To protect his sensor this time around he coated the board with polyurethane, which should provide a decent corrosion barrier.

Using the Arduino CapSense library, the sensor can detect the presence of water, signaling an alarm if the base needs refilling. One of our readers suggested that he use the tree itself as a low water indicator, which is just what [Eric] did this year. If the water is somewhat low, the Arduino-controlled relay powering the tree is switched off and then on again, every 5 seconds. If the base is nearly dry, the tree asks for water by blinking the word “Water” repeatedly in Morse code.

We think that this year’s solution is pretty clever, and we’re glad to see that [Eric] didn’t give up after last year’s setback!

Proto-board Z80 computer


We’ve seen  Z80 processor based computers before but they usually use a printed circuit board to easily and reliably connect all the components. [Marton] sent us his Z80 based computer from a while back that is built entirely on prototyping board. He made his own video board that utilizes a TV as the monitor and his own mainboard incorporating a keyboard controller. The system runs at 4 MHz, has 32k of ram, and runs [Marton's] own system software which he has posted. Its quite impressive and we love the protoboard porn with thousands of grey wires running everywhere.

[Marton] used the resources on [Hans Summers'] site for his project. Make sure to check it out if you’re interested in a broader background concerning DIY Zilog Z80 computers.