We continue on our temperature related adventures with a whopping 64 channel DS18B20 datalogger…
This is another 100% in-house build(except for the chinese DS18b20 sensors of course).
The basic idea is that these 1-wire sensors can be addressed by a 64 Byte GUID which allows you to hook up as many as you’d like to a single gpio pin. We decided to stop at 2×32 channels for the sake of our sanity.
Apart from measuring temperature, this puppy also has a LEM Hall effect current sensor that is good for -250A to +250A. This is the blue loopy thing and the white box below it contains a 12 bit SPI ADC and a 0.1% initial accuracy 3v3 reference(MCP1501) so you can have a rather long cable run from the MCU to the Hall Sensor(of course, an i2c ADC would’ve been nicer but it’s all we had at hand).
In addition to the current sensor we also gave it a 0-100V DC voltage sense input.
Now, obviously, the smartphone app starts to get a bit crowded with the (now 32) number of sensors this thing can put out. That’s why we built a PC app for logging and graphing which we’ll cover in a different write-up.
Oh, and it all runs off an STM32F103.

Some pictures of the lovely beast.