Panplex Thermometer
So I picked up two of these nice panplex display from the WEEE bin at uni, sadly out of the two I got, one had had its nipple knocked off leading to the gas escaping. So I origiunaly decided to build a panplex watch. I managed to get hold two BECKMAN DD700 driver chips which I over payed for & seems to be the last of the supply as I have not seen one on eBay since. PS one of the chips suvied being sucked up the vacume cleaner & was only found when looking for something else.
Anyway I built all of it into a little testing mudual, obtained a mini nixie driver & used a 8 switch dip switch to send the BCD codes to the DD700 driver chips. From the four photos you can see it was a success & the setup worked. I just needed to do the Arduino code first.
After meany years, workshop rebuilds & moves. I finaly soldered an Arduino to it & started to get a proof of consept working. I even designed a PCB & then got my partner to cut it out with his CNC machine.
But for a good part of the prototyping the Aduino was done on a breeadboard.
The Code
The code was actualy pretty simple> defined the array that would be refrenced to show the digits on each number. I also created functions that outputted them to the BCD outputs themselves. This code was partialy nicked & modifyed from my Bubble LED test code. Those ended up being used in my Acorn System 1.
The next part was getting the code to interface with the DHT11 sensor. Turned out to be super easy as it had libarys, Getting the display code to interface with the DHT11 was nice & easy.
Once that was done things started to get a little more tricky. First was the timing as I wanted to use blink without delay. The example code is not really writtin out to well & is quite hard to follow. Luckily someone on line had written out a better for easy to follow version. Sometimes the Arduino versions try & explain to much or put to much into the examples.
The next challenge was getting the buttons to work properly. Turned out after much trobble shooting, one of the old good practises came in to bite my ass. Don't forget the pullup/pulldown resistors. Once that was done the buttons were working perfectly with on noise interference. I did try doing the pullup/pulldown in software, it did not work.
Once the all importat 10K SMD resistors were added I had a spare button that did not do anything. So rather than have it do nothing, I made it display 69 when pressed for about the same amout of time it would display the humidity when the other button was pressed.
The Panplex Display in its final state, showing the temprature in *C. It is reading quite high as I built the device in the heat wave the UK was having in the summer of 2022. It was insainly hot. The heatwave was part of what inspired me to built the thing in the first place.