Circuit schematics.
Version 1.5.
I've released an updated version of this project.
Analog temperature sensor updated to a more accurate DS18B20 digital sensor.
Now supports barometric pressure logging with a MPL3115A2 digital barometer.
Improved beat amplifier performance.
A battery charger circuit that will charge NiCad or NiMh batteries.
A low battery warning and low battery shutdown option.
A switch or jumper to select low or high gain for the beat amplifier.
Schematics for previous versions.
there were two schematics for the initial version.
Below are the schematics for the initial version.
Standard schematic.
Better accuracy with the optical sensor.
More sensitivity to pick up beats from quiet ticking clocks. Only needed with sound or vibration sensors.
Download parts list for the initial version.
Questions or comments? Email me: