I'm just designing an easy to build thermometer kit based on the Russian IN-9 bargraph Nixie tube.
My intention to do such a thing was a photo I've found on the internet:
Now the very first prototype is ready. The goal was to use only easy to understand analogue technique, no pic and no processor. So measurement can only done with a multimeter.
The thermometer is powered via 5V from one or two USB ports (depending on the PC's power capacity, sometimes a power Y-cable is needed) or from a cheap external USB loader.
See here a video from this prototype and also some photos
Thanks to the big size of the base I can used "hrugged" electronic parts which are not as filigree as used in my clocks. So assembling the kit is very easy.
Prices and availability - The kit will cost 79 EUR plus shipping (10 EUR for overseas) fully completed incl. case, scale, IN-9 tube and USB-cable and I hope that I can deliver the first kits at the beginning of April.
The termometer has a second input, but actual the circuity isn't able to display temperatures lower than 2°C.
The measurement range of this input is actual +30°...+60°C and can be used e.g. to monitor the processor temperature of the PC.
But I can do a redesign for an extended temperature range on the second input, displayed on the left scale, let's say -20°...+40°C
Hhm, it seems that I have to redesign the step up converter (5V --> 125V). It generates heat, not too much for a Nixie clock but too much for a thermometer with build in temperatur sensor. So the displayed temperature will be around 3°C too much when powered on for a while.
These modifications will also lower or disable the switching noise generated by the inductor...
The transforming of the sensor's output voltage (100 mV @ °C, eg. 200mV @ 20°C) to the display graph lenght however is extrem exact
Jürgen sent me this work-in-progress photo a few days ago. But, I'm bad about posting things quickly
"For a full length bargraph now the circuity draws only around 300mA @5V --> 1.5VA and this creates 10mA @ 120V --> 1.2VA (only 0.3VA losses); but I must also connect the MC34063A to the voltage doubler circuity (the flying IC "ICL7660" with the two diodes and the two capacitors) and not only the new BC639/640 driver stage for the MosFet...as the converter will shut down when the supply voltage is lower than exact 5V and it should normally just work at 4V."