Detector for meeting our hedgehogs, when they leave the nest under the firewood shed.
Fixing the electronics.
To the left is the waterproof ultrasonic radar with 433MHz wireless link. It has an "activity led" that we moved from the front to the back, so it wouldn't disturb the hedgehogs.
This is the placement of the radar sensor.
They seemed to be able to hear the ultrasound a bit, but were not bothered about it.
Long-range repeater in the firewood shed, built into a scrapped transistor radio..
433MHz regenerative receiver and 462MHz 500mW transmitter, using the D-cell battery compartment.
Those big batteries were sufficient for two weeks of continuous operation.
Alarm receiver inside the house.
Modified for 5V USB supply.