# Spatial Metal Field Display Mini ## Description Breadboard-only schematic for an ESP32-based LC electromagnetic response visualizer using a handmade coil oscillator, LM339 comparator, GPIO27 frequency input, SSD1306 I2C OLED, and calibration button. No PCB layout is included. ## Project Details - **Owner:** ezexa - **Created:** 6/7/2026 - **Last Updated:** 6/7/2026 - **Visibility:** Public ## Key Components ### Q1 — [BC547](https://www.flux.ai/adrian95/bc547~ejc.md) - Role: Oscillator transistor - Manufacturer Name: onsemi - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Transistor - Datasheet URL: https://media.digikey.com/pdf/Data%20Sheets/ON%20Semiconductor%20PDFs/BC546-50.pdf - Role Details: BC547 NPN in LC oscillator stage - Manufacturer Part Number: BC547 **Pins:** - B [pin 2] - C [pin 1] - E [pin 3] ### RE — [Generic Resistor](https://www.flux.ai/vasyl/generic-resistor~opd.md) - Role: Emitter resistor - Resistance: 1kΩ - Part Type: Resistor - Package: SMD_0603_1608Metric - Role Details: Q1 emitter to GND **Pins:** - P1 [pin 1] - P2 [pin 2] ### SW1 — [6x6mm micro tactile switch](https://www.flux.ai/jecstronic/6x6mm-micro-tactile-switch~igw.md) - Purchase Url: https://shopee.ph/20Pcs-Micro-Tactile-Switch-Momentary-Tact-DIP-Switch-2Pin-6-X-6mm-Micro-Touch-Push-Button-Switch-High-5mm-6mm-7mm-8mm-9mm-i.1018846655.22773354064?sp_atk=2b55ff5c-bbfc-4967-b7e3-adb8c93c34e2&xptdk=2b55ff5c-bbfc-4967-b7e3-adb8c93c34e2&is_from_login=true - Role: Calibration button - Part Type: Switch - Role Details: GPIO14 to GND momentary switch; ESP32 internal pull-up in firmware **Pins:** - P1 [pin 1] - P2 [pin 2] ### U1 — [ESP32-DEVKITC-VE](https://www.flux.ai/adrian95/esp32-devkitc-ve~ezx.md) - Role: Microcontroller module - Datasheet URL: https://docs.espressif.com/projects/esp-idf/en/latest/esp32/hw-reference/esp32/get-started-devkitc.html - Part Type: Development Boards - Digi-Key Part Number: 1965-ESP32-DEVKITC-VE-ND - Role Details: ESP32 DevKit for breadboard prototype - Manufacturer Part Number: ESP32-DEVKITC-VE - Package or Case Code: ESP32DEVKITCVE - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Name: Espressif Systems **Pins:** - 3V3 [pin 1] - 5V [pin 19] - CLK [pin 20] - CMD [pin 18] - D0 [pin 21] - D1 [pin 22] - D2 [pin 16] - D3 [pin 17] - EN [pin 2] - GND_1 [pin 14] - GND_2 [pin 32] - GND_3 [pin 38] - IO0 [pin 25] - IO12 [pin 13] - IO13 [pin 15] - IO14 [pin 12] - IO15 [pin 23] - IO16 [pin 27] - IO17 [pin 28] - IO18 [pin 30] - IO19 [pin 31] - IO2 [pin 24] - IO21 [pin 33] - IO22 [pin 36] - IO23 [pin 37] - IO25 [pin 9] - IO26 [pin 10] - IO27 [pin 11] - IO32 [pin 7] - IO33 [pin 8] - IO34 [pin 5] - IO35 [pin 6] - IO4 [pin 26] - IO5 [pin 29] - RX [pin 34] - TX [pin 35] - VN [pin 4] - VP [pin 3] ### U3 — [LM339AN](https://www.flux.ai/jecstronic/lm339an~5u1.md) - Part Type: Integrated Circuit - Manufacturer Part Number: LM339AN - Role: Comparator - Role Details: Channel 1 compares SIG_IN to VREF; open collector output pulled up to +3V3 - Manufacturer Name: Texas Instruments - Datasheet URL: https://www.ti.com/lit/ds/symlink/lm339.pdf - License: https://creativecommons.org/licenses/by/4.0/ **Pins:** - INVERTING_INPUT1 [pin 4] - INVERTING_INPUT2 [pin 6] - INVERTING_INPUT3 [pin 8] - INVERTING_INPUT4 [pin 10] - NON-INVERTING_INPUT_1 [pin 5] - NON-INVERTING_INPUT_3 [pin 9] - NON-INVERTING_INPUT2 [pin 7] - NON-INVERTING_INPUT4 [pin 11] - OUTPUT1 [pin 2] - OUTPUT2 [pin 1] - OUTPUT3 [pin 14] - OUTPUT4 [pin 13] - VCC- [pin 12] - VCC+ [pin 3] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/ezexa/spatial-metal-field-display-mini~up](https://www.flux.ai/ezexa/spatial-metal-field-display-mini~up).* --- *Generated from [https://www.flux.ai/ezexa/spatial-metal-field-display-mini~up](https://www.flux.ai/ezexa/spatial-metal-field-display-mini~up)*