8-way temperature sensor

Fig.1: schematics. A boost-converter generates 3.3 V for the MCU (V_OUT), LED-currents are sinked (sunk?) by the MCU using a shared series-resistor, and light-intensity is obtained by measuring how long it takes to charge a cap (V_LDR).

Fig.2: PCB-layout, as seen in Kicad. Red traces are on the front; the back only has a battery-holder. The blue circle on the upper left is the LDR; the big IC is the MCU, and the SOT23-5 is the DC/DC converter. The 3 pads on either side are ISP-signals for programming and debugging.

Introduction

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General operation

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Have fun -- Michai