• The CrowBox v.3 : 3D Printing, ESP32-C3 Deep Sleep, and 280 Days of Battery Life

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pa...@freemail.ch

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Jun 27, 2026, 10:23:10 AM (10 days ago) Jun 27

to Crow Box Kit

This project is based on the CrowBox v.3 , which is provided completely free by Josh at thecrowbox.com. All the original design files and build instructions are linked from his site and YouTube videos. A massive thanks to Josh for sharing all the details—the engineering, documentation, and step-by-step video instructions are excellent!

I’ve made two videos: one showing how smart these crows areinteracting with the box (and how much they enjoy a challenge)
https://youtube.com/shorts/5fcoVyiHyOs

and another showing this modified, 3D-printed version of the box.
https://www.youtube.com/shorts/xl7p5AO39es

### 🛠️ The Modifications

I started with Josh’s 3rd-generation CrowBox design but made a few key changes to fit my specific setup:

* **3D Printed Chassis:** The original plans are designed mainly for DXF laser-cut acrylic. To use my 3D printer instead, I imported and extruded the parts by 3mm in CAD, increasing the tab-hole clearances by about 0.2mm to make the printed parts fit together reliably.

* **Power Optimization:** I wanted the box to be as power-efficient as possible. I swapped the controller for an ESP32-C3 SuperMini. It can be safely powered by 4 NiMH cells—meaning no LiPo handling, no complicated cutoff circuits, and near zero battery safety concerns outdoors.

* **Servo Control:** I replaced the stock servo with a smaller TowerPro MG90S, which has plenty of torque for this hatch and uses less power. Crucially, the servo's power is fully switched off via hardware when not in use.

### 🔋 The Battery Math (Theoretical vs. Real-World)

In deep sleep, the ESP32-C3 circuit pulls just **~70 microamps**as measured in this project. Based on a conservative estimate of 250mA draw for the MG90S during its 15-second hatch cycle:

* **Per Cycle:** 250 mA × 15s / 3600 = **~1.04 mAh**

* **Daily Servo Draw (5 activations/day):** 1.04 mAh × 5 = **~5.2 mAh**

* **Daily Deep Sleep Draw:** 0.07 mA × 24h = **~1.68 mAh**

* **Total Estimated Daily Use:** **~6.9 mAh/day**

With four 1950 mAh Eneloop NiMH cells in series (pack capacity remains 1950 mAh), the rough theoretical runtime is:

> **1950 mAh / 6.9 mAh/day = ~280 days of runtime.**

*(In real use, cold weather, NiMH self-discharge, and WiFi calibration will lower this, but it easily runs for months between charges!)*

### ✨ Current Features Added

* ESP32-C3 low-power controller & 4-cell NiMH battery power

* MG90S servo hatch with isolated hardware power-off during sleep

* **WiFi AP Configuration Page:** Long-pressing the physical maintenance button launches a captive portal (`CrowBox-Config` at `192.168.4.1`)

* **Web Portal Controls:** Read battery voltage (calibrated), manually open/close/nudge the hatch, test switches, adjust opening/closing speeds, adjust hold-open time, and toggle landing/coin switches for different training levels.

* **Maintenance Mode:** A short press opens the hatch and keeps it open so I can clean the tray or remove the rail mechanism.

### 🔮 Future Ideas

1. **ESP-NOW Remote Notification:** Sending a fast, low-power message to a second ESP32 inside the house (a small desk gadget or wearable receiver) that flashes or rings the second a crow triggers the box.

2. **ESP32-CAM Integration:** To snap a photo the moment a bird lands or drops a coin.

The wiring inside is still total development-stage spaghetti while I finish testing functions, but the core system is rock solid.