This is actually the second revision of my USB thermometer (the first one is not listed on Tindie, there is a couple of words about it on my web page The main thought for this revision was to add h...Read More…
This is actually the second revision of my USB thermometer (the first one is not listed on Tindie, there is a couple of words about it on my web page
The main thought for this revision was to add humidity measurement so instead of using Maxim's DS18B20 temperature sensor I decided to use a cheap relative humidity sensor DHT22 which also has a temperature sensor. I drew a new board in Eagle based on the same Seedstudio's template for DP8049 acrylic case. The device is based on PIC16F88 running with internal oscilator and MAX7219 driver for 7 segment display. Firmware switches between temperauture and humidity display every 10 sec.
If you wish to change the firmware, there is a place for ICSP connector, reset button, and a few of the IO pins are available. Initially I planned to put the sensor on the board (top right corner, and to span over the edge of the board) but in that position temperature readings were about two degrees higher so I decided to put it on the separate board. Power is supplied over the mini USB connector but there are also a few power pins on the board available. In this revision I also added acrylic "legs" so the device can stand on the table (well, it should be standing...)
The device is available for purchase in four colours: white, blue, yellow and red. The power supply adapter is not included.
Mauro | Nov. 18, 2014
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