PoopBlocker 3000 — A humane, IoT-enabled ultrasonic deterrent system that keeps cats away from your garden, without harming them or bothering humans.
My parents' garden became a regular bathroom spot for neighborhood cats. As an electrical engineer, I was given a clear mission: build a humane, effective, and non-invasive solution.
Cats hear up to ~60 kHz, while humans top out at ~20 kHz. By generating an ultrasonic signal around 40 kHz, the system creates a highly unpleasant environment for cats — completely inaudible to humans.
The key challenges:
- Cover an 8×4 m garden without false triggers from wind or leaves
- Hide the sensor inside a plastic enclosure (radar waves must pass through, but not concrete walls)
- Enable remote on/off and scheduling via smartphone
| Component | Role |
|---|---|
| ESP8266 (NodeMCU) | Main controller + WiFi + Blynk IoT |
| TC4427 MOSFET Driver | Differential drive for efficient piezo excitation |
| Piezo Ultrasonic Transducers | 40 kHz resonant speakers |
| HLK-LD2420 Radar Sensor | Precise motion detection, ignores wind/leaves |
| Push Button | Local toggle (on/off) |
| Status LED | System state feedback |
| Pin | GPIO | Function |
|---|---|---|
| D1 | GPIO5 | Ultrasonic A (TC4427 IN+) |
| D2 | GPIO4 | Ultrasonic B (TC4427 IN-, inverted) |
| D5 | GPIO14 | Motion input (HLK-LD2420) |
| D6 | GPIO12 | Button input (INPUT_PULLUP) |
| D7 | GPIO13 | Status LED |
| Pin | Direction | Description |
|---|---|---|
| V0 | Write | Remote enable/disable |
| V1 | Write | Frequency slider (1000-35000 Hz) |
| V2 | Read | Motion status LED |
| V3 | Read | Speaker active LED |
Measured output on Keysight MSO-X 4024A:
| Parameter | Value |
|---|---|
| Frequency | 41.322 kHz |
| Amplitude | 10.313 Vpp |
| Waveform | Square wave (differential) |
Clone: https://github.com/asafdabush/POOPCAT.git
Copy secrets_template.h to secrets.h and fill in your WiFi SSIDs, passwords, and Blynk token.
- ESP8266WiFi (via ESP8266 board package)
- BlynkSimpleEsp8266 (via Library Manager)
Select NodeMCU 1.0 (ESP-12E Module), upload, done.
Asaf Refael Dabush Electrical & Electronics Engineering - Ariel University, 2026
Released under the MIT License.