Project Overview: This project is an enhanced LED blinking circuit that goes beyond a simple 555 timer-based design. It incorporates additional features such as random blinking patterns, speed control, and a start/stop function. The project utilizes a microcontroller, such as an Arduino or Raspberry Pi, to control the blinking patterns, speed, and start/stop functionality. LED Blinking: The board features a total of 8 LEDs that blink in various random patterns. When the board is powered on, even before user interaction, the LEDs start blinking randomly, creating an eye-catching display. Each LED has its own current-limiting resistor to ensure proper current flow and prevent damage. The microcontroller is programmed to generate random blinking patterns for the LEDs, ensuring that the LEDs do not blink in a predictable or sequential order. This random blinking adds an element of unpredictability and visual interest to the project. Speed Control: The board includes two speed control buttons that allow the user to adjust the blinking speed of the LEDs. Button 1 is designated as the "fast" button, increasing the blinking speed when pressed, while Button 2 is designated as the "slow" button, decreasing the blinking speed when pressed. The speed control provides a range of blinking speeds, from a slow, gradual blink to a rapid, strobe-like effect. The microcontroller monitors the state of the speed control buttons and adjusts the blinking speed accordingly. Start/Stop Functionality: A third button serves as a start/stop control. When pressed, it toggles the blinking of the LEDs on or off. This allows the user to freeze the blinking pattern at any desired moment or resume the blinking when desired. The microcontroller handles the start/stop functionality by turning the LEDs on or off based on the state of the start/stop button. Manual Speed Adjustment: In addition to the speed control buttons, the board includes a potentiometer or variable resistor. This component allows the user to manually adjust the blinking speed of the LEDs by turning the knob or sliding the control. The manual speed adjustment provides more precise and customizable control over the blinking speed compared to the preset speeds of the buttons. The microcontroller reads the analog value from the potentiometer and adjusts the blinking speed accordingly. Power and Connectivity: The board is powered through a USB-C or USB-micro B connector, allowing it to be easily connected to a power source such as a computer or wall adapter. A voltage regulator may be included to ensure a stable and appropriate voltage supply to the components. A power switch is incorporated to conveniently turn the board on or off.

IMPORTANT NOTICE: Hey, I opened editing permissions and this doc is broken, see the frozen version here: https://www.flux.ai/markwuflux/on-air-markwu2001-remix-r1-backup-freeze-0b49 R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C.

This circuit drives 10 LEDs making them flash to the rhythm of the music (using a TIP31C transistor to act as a voltage-controlled switch) Credit: https://www.youtube.com/watch?v=3qZ3uA8hDmE

This is a very simple timer circuit. When you push down to turn on the S1, this will turn on the LED and it also will charge the C1 Capacitor. Then upon releasing the push button switch, the LED will stay lit for couple of seconds until C1 is completely discharged.

Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C.

Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C.

R2 w Thread changes: -Moving to Letter Modules for ease of design -Adding MGM210L for Matter on Thread On/Off and intensity control -Shifted A and R letters closer to fix Kerning -Optional: Add unpopulated AA Battery Holder for battery option R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C. #template #arduino-matter

This circuit drives 10 LEDs making them flash to the rhythm of the music (using a TIP31C transistor to act as a voltage-controlled switch) Credit: https://www.youtube.com/watch?v=3qZ3uA8hDmE

This circuit drives 10 LEDs making them flash to the rhythm of the music (using a TIP31C transistor to act as a voltage-controlled switch) Credit: https://www.youtube.com/watch?v=3qZ3uA8hDmE

This circuit drives 10 LEDs making them flash to the rhythm of the music (using a TIP31C transistor to act as a voltage-controlled switch) Credit: https://www.youtube.com/watch?v=3qZ3uA8hDmE

R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C.

This circuit is an ultrasonic distance meter based on an ATTiny2313 microcontroller. It uses an HC-SR04 ultrasonic sensor to measure distance and displays the results on an OLED display. The power supply is constructed using a Boost converter (TPS613222A) and a 2-cell AA battery. Additionally, it also includes ISP for programming, RESET and START switches, and LED indicators. #project #Template #projectTemplate #ultrasonic #OLED #arduino #attiny2313 #TPS613222A #ISP #referenceDesign #simple-embedded #microchip #template #reference-design .

Typical Application Circuit for RT6150B-33GQW, 1 Positive Fixed Output 3.3V 800mA. Input voltage 6V max. With JST connectors(Vin and +3V3) and with block terminal connectors(Vin and +3V3) #project-template #voltageregulator #switchingregulator #BuckBoost #project

This circuit is an ultrasonic distance meter based on an ATTiny2313 microcontroller. It uses an HC-SR04 ultrasonic sensor to measure distance and displays the results on an OLED display. The power supply is constructed using a Boost converter (TPS613222A) and a 2-cell AA battery. Additionally, it also includes ISP for programming, RESET and START switches, and LED indicators. #project #Template #projectTemplate #ultrasonic #OLED #arduino #attiny2313 #TPS613222A #ISP #referenceDesign #simple-embedded #microchip #template #reference-design

A circuit that uses a high/low signal to route a separate PWM signal to one of two outputs.

Welcome to your new project. Imagine what you can build here.

Welcome to your new project. Imagine what you can build here.

Touch Sensor Schematic

Welcome to your new project. Imagine what you can build here.

The analog car design is a self-running electric car that avoids obstacle in the left-right region. The design is mainly supported with 5 circuit components. The 9 V to 5 V converted for voltage-current manipulations. The push-button delay circuit (kill switch) for users to temporarily be able to stop the car motors benefiting from RC circuit, MOSFET transistors, and 74HC14 Hex Schmitt Trigger Inverters. The motor speed controller using potentiometers, inverters, and generic diodes. As well as the HC-SR04 Ultrasonic Sensor circuit to sense the proximity of objects in a field of view.

A momentary or non-latching switch which causes a temporary change in the state of an electrical circuit only while the switch is physically actuated.

A momentary or non-latching switch which causes a temporary change in the state of an electrical circuit only while the switch is physically actuated.

A momentary or non-latching switch which causes a temporary change in the state of an electrical circuit only while the switch is physically actuated.

A momentary or non-latching switch which causes a temporary change in the state of an electrical circuit only while the switch is physically actuated.

Circuit using HK016K HK016K is a chip for on/off switch with auto-turn-off

Welcome to your new project. Imagine what you can build here.

Welcome to your new project. Imagine what you can build here.

Welcome to your new project. Imagine what you can build here.

Welcome to your new project. Imagine what you can build here.

This project is an RF-ID lock circuit, complete with microcontroller (MCU). It features an RC522 RFID reader for identification, controlled by an STM32F103C8T6 MCU. The structure also includes an OLED display, lock circuit, and user interface switches. Designed to operate with a AAA battery power source. #MCU #referenceDesign #simple-embedded #stm #project #STM32 #lock #OLED #template #reference-design

This project is an RF-ID lock circuit, complete with microcontroller (MCU). It features an RC522 RFID reader for identification, controlled by an STM32F103C8T6 MCU. The structure also includes an OLED display, lock circuit, and user interface switches. Designed to operate with a AAA battery power source. #MCU #referenceDesign #simple-embedded #stm #project #STM32 #lock #OLED #template #reference-design

This project is an RFID lock circuit, complete with microcontroller (MCU). It features an RC522 RFID reader for identification, controlled by an STM32F103C8T6 MCU. The structure also includes an OLED display, lock circuit, and user interface switches. Designed to operate with a AAA battery power source. #MCU #referenceDesign #simpleEmbedded #stm #project #STM32 #lock #OLED #template #reference-design

This project is an RF-ID lock circuit, complete with microcontroller (MCU). It features an RC522 RFID reader for identification, controlled by an STM32F103C8T6 MCU. The structure also includes an OLED display, lock circuit, and user interface switches. Designed to operate with a AAA battery power source. #MCU #referenceDesign #simple-embedded #stm #project #STM32 #lock #OLED #template #reference-design

The LS3018N, manufactured by iSion, is an N-Channel Enhancement Mode MOSFET designed for low voltage drive applications, making it ideal for portable equipment. Available in a compact SOT-323 package, this MOSFET features low on-resistance and fast switching speeds, facilitating easy drive circuit design and parallel configurations. The device operates with a gate-source voltage as low as 2.5V and can handle a continuous drain current of up to 100mA, with a peak drain current of 400mA. The LS3018N supports a maximum drain-source voltage of 60V and a gate-source voltage of +20V. It offers robust thermal performance with a junction-to-ambient thermal resistance of 833°C/W and is compliant with RoHS standards. Key electrical characteristics include a drain-source breakdown voltage of 60V, a gate threshold voltage range of 0.8V to 1.5V, and a static drain-source on-resistance as low as 3.0Ω at VGS of 4V. The component also features minimal input capacitance, making it suitable for high-speed switching applications.

The AO3422 from Alpha & Omega Semiconductor is a high-performance, N-Channel Enhancement Mode Field Effect Transistor (FET) that leverages advanced trench technology to achieve outstanding RDS(ON) and low gate charge. Designed for efficient power conversion and load switching applications, this component operates effectively across a wide gate drive range of 2.5V to 12V. The AO3422 is characterized by a drain-source voltage (VDS) of 55V and a continuous drain current (ID) of 2.1A at a gate-source voltage (VGS) of 4.5V. Its RDS(ON) is impressively low, coming in at less than 160mΩ at VGS of 4.5V, making it suitable for a variety of power management tasks. The device is encapsulated in a compact SOT23 package, offering a robust solution for space-constrained applications. Additional features include a maximum junction temperature of 150°C, high forward transconductance, and fast switching characteristics that support efficient and reliable operation in high-performance circuit designs.

R2 changes: -Moving to Letter Modules for ease of design -Adding ESP32 for WiFi On/Off and intensity control -Optional: Add unpopulated AA Battery Holder for battery option R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C. #template

Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C.

R2 changes: -Moving to Letter Modules for ease of design -Adding ESP32 for WiFi On/Off and intensity control -Optional: Add unpopulated AA Battery Holder for battery option R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C. #template

R2 changes: -Moving to Letter Modules for ease of design -Adding ESP32 for WiFi On/Off and intensity control -Optional: Add unpopulated AA Battery Holder for battery option R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C. #template

This document provides a detailed guide to building a relay circuit that uses a Raspberry Pi to control a buzzer. The relay acts as a switch, allowing the Raspberry Pi to turn the buzzer ON and OFF through GPIO pins.

R2 w Thread changes: -Moving to Letter Modules for ease of design -Adding MGM210L for Matter on Thread On/Off and intensity control -Shifted A and R letters closer to fix Kerning -Optional: Add unpopulated AA Battery Holder for battery option R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C. #template #arduino-matter

R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C.

IMPORTANT NOTICE: Hey, I opened editing permissions and this doc is broken, see the frozen version here: https://www.flux.ai/markwuflux/on-air-markwu2001-remix-r1-backup-freeze-0b49 R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C.

Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C.

TECHNICAL ASSIGNMENT AND DESIGN GUIDE Active Three-Way Crossover on NE5532 Powered by AM4T-4815DZ and Amplifiers TPA3255 (Updated Version) 1. GENERAL PURPOSE OF THE DEVICE The goal of the development is to create an active three-way audio crossover for one channel of a loudspeaker system, working with the following drivers: LF: VISATON W250 MF: VISATON MR130 HF: Morel MDT-12 Each frequency range is amplified by a separate power amplifier: LF: TPA3255 in PBTL mode (mono) MF + HF: second TPA3255 in stereo mode (one channel for MF, the other for HF) The crossover accepts a single linear audio signal (mono) and divides it into three frequency bands: Range Frequency Range LF 0 – 650 Hz MF 650 – 2500 Hz HF 2500 Hz and above Filter type: Linkwitz–Riley 4th order (24 dB/oct) at each crossover point (650 Hz and 2500 Hz). The crossover must provide: minimal self-noise; no audible distortion in the audible range; stable operation with NE5532 at ±15 V power supply; easy adjustment of the level for each band, as well as the overall level (via the input buffer). 2. FILTER TYPES AND BASIC OPERATING PRINCIPLES Each filter is implemented as two cascaded Sallen–Key 2nd order (Butterworth) stages, resulting in a final 4th order LR4 filter. Topology: non-inverting Sallen–Key, optimal for NE5532. For all stages: Cascade gain: K ≈ 1.586 This provides a Q factor of 0.707 (Butterworth), which in combination gives a Linkwitz–Riley 4th order. 3. COMPONENT VALUES FOR FILTERS 3.1 Universal Parameters RC chain capacitors: 10 nF, film capacitors, tolerance ≤ 5% Resistors: metal-film, tolerance ≤ 1% The gain of each stage is set by feedback resistors: Rf = 5.9 kΩ Rg = 10 kΩ K ≈ 1 + (Rf / Rg) ≈ 1.59 The circuit should allow for the installation of a small capacitor (10–47 pF) in parallel with Rf (footprint provided) for possible stability correction (not mandatory to install in the first revision). 3.2 650 Hz Filters (Low-frequency boundary for MF) These are used for the division between W250 and MR130. LP650 — Low-frequency Filter 2nd Order R1 = 24.9 kΩ R2 = 24.9 kΩ C1 = 10 nF C2 = 10 nF Two stages: LP650 #1 and LP650 #2. HP650 — MF High-frequency Filter 2nd Order Same values: R1 = 24.9 kΩ R2 = 24.9 kΩ C1 = 10 nF C2 = 10 nF Two stages: HP650 #1 and HP650 #2. 3.3 2500 Hz Filters (Upper boundary for MF) These are used for the division between MR130 → MDT-12. LP2500 — High-pass MF Filter R1 = 6.34 kΩ R2 = 6.34 kΩ C1 = 10 nF C2 = 10 nF Two stages: LP2500 #1 and LP2500 #2. HP2500 — High-frequency Filter Same values: R1 = 6.34 kΩ R2 = 6.34 kΩ C1 = 10 nF C2 = 10 nF Two stages: HP2500 #1 and HP2500 #2. 4. OPERATIONAL AMPLIFIERS The NE5532 (dual op-amp, DIP-8 or SOIC-8) is used. A minimum of 4 packages (8 channels) for filters: NE5532 Function U1A, U1B LP650 #1, LP650 #2 (LF) U2A, U2B HP650 #1, HP650 #2 (Lower MF cut-off) U3A, U3B LP2500 #1, LP2500 #2 (Upper MF cut-off) U4A, U4B HP2500 #1, HP2500 #2 (HF) Additionally: U5 — input buffer / preamplifier (both channels) If necessary, an additional NE5532 (U6) for the balanced input (see section 6.2). All NE5532 should have local decoupling for power supply (see section 5.1). 5. CROSSOVER POWER SUPPLY AM4T-4815DZ DC/DC module is used: Input: 36–72 V, connected to the 48 V power supply for TPA3255 amplifiers. Output: +15 V / –15 V, up to 0.133 A per side. Maximum output capacitance: ≤ 47 µF per side (according to the datasheet). 5.1 Power Filtering Input (48 V): RC variant (simpler, acceptable for the first revision): R = 1–2 Ω / 1–2 W C = 47–100 µF (for 63 V or higher) LC variant (preferred for improved noise immunity): L = 10–22 µH C = 47–100 µF The developer may implement LC if confident in choosing the inductance and its parameters. Output +15 V and –15 V (general filtering): Electrolytic capacitor 10–22 µF per side 100 nF (X7R) per side to GND Local decoupling for NE5532 (REQUIRED): For each NE5532 package: 100 nF between +15 V and GND 100 nF between –15 V and GND Place as close as possible to the op-amp power pins (short traces). Additional local filtering for power lines: For each NE5532, decouple from the ±15 V main rails: Either 4.7–10 Ω resistor in series with +15 V and –15 V, Or ferrite bead in each rail. After this component, place local capacitors (100 nF + 1–4.7 µF) to ground. 6. INPUT TRACT: INPUTS, BUFFER, ADJUSTMENT 6.1 Unbalanced Input (RCA / Jack / Linear) The main mode is the unbalanced linear input, for example, RCA. Input tract structure: RF-filter and protection: Signal → series resistor Rin_series = 100–220 Ω After resistor — capacitor Cin_RF = 470–1000 pF to GND This forms a low-level RF filter and reduces high-frequency noise. DC-block (low-pass HP-filter): Capacitor Cin_DC = 2.2–4.7 µF film in series Resistor to ground Rin_to_GND = 47–100 kΩ Cut-off frequency — negligible in the audio range but removes DC. Input buffer / preamplifier (NE5532, U5): Non-inverting configuration. Input — after DC-block. Gain: adjustable, e.g., Rg_fixed = 10 kΩ (to GND through trimmer) Rf = 10–20 kΩ + footprint for trimmer (e.g., 20 kΩ) The gain should be in the range of 0 dB to +10…+12 dB. Possible configuration: Rg = 10 kΩ fixed Rf = 10 kΩ + 10 kΩ trimmer in series. This allows adjusting the overall level of the crossover according to the source and amplifier levels. Buffer output: A low-impedance output (after NE5532) This signal is simultaneously fed to the inputs of all filters: LP650 (LF) HP650 → LP2500 (MF) HP2500 (HF) 6.2 Balanced Input (XLR / TRS) — Optional, but laid out on the board The board should allow for a balanced input, even if it’s not used in the first revision. Implementation requirements: XLR/TRS connector (L, R, GND) or separate 3-pin header. Simple differential receiver on NE5532 (extra U6 package or use one channel of U5 if sufficient). Circuit: classic instrumentation amplifier or differential amplifier: Inputs: IN+ and IN– Output — single-ended signal of the same level (or slightly amplified), fed to DC-block and buffer (or directly to the buffer if integrated). Switching between balanced/unbalanced mode: Implement using jumpers / bridges or adapters: Either switch before the buffer, Or use two separate pads, one of which is unused. All balanced input grounds must be connected to the same AGND point as the unbalanced input to avoid ground loops. 7. LEVEL ADJUSTMENT OF BANDS (BEST METHOD) The level adjustment of each band (LOW, MID, HIGH) is required to match the sensitivity of the speakers and amplifiers. Recommended method: After each full filter (after LP650×2, MID-chain HP650×2 → LP2500×2, HP2500×2), install: A passive attenuator: Series: Rseries (0–10 kΩ, adjustable) Shunt: Rshunt to GND (10–22 kΩ, fixed or adjustable) For simplicity and reliability: Implementation on the board: For each band (LOW, MID, HIGH) provide: Pad for multi-turn trimmer 10–20 kΩ as a divider (between signal and ground) in the "level adjustment" configuration. If adjustment is not needed — install a fixed divider (two resistors) or simply use a jumper. It is preferable to use: For setup: multi-turn trimmers 10–20 kΩ, available on the top side of the board. Nominals for the initial configuration can be selected through measurements, but the PCB should have flexibility. This provides: Accurate balancing of band volumes without interfering with the filters; Flexibility for fine-tuning to the specific characteristics of the speakers. 8. INPUTS AND OUTPUTS OF THE CROSSOVER (FINAL) 8.1 Inputs 1× Unbalanced linear input (RCA or 3-pin header) 1× Balanced input (XLR/TRS or 3-pin header) — optional, but space must be provided on the board. Input impedance (unbalanced after RF-filter): 22–50 kΩ. The input tract must be implemented using shielded cables. 8.2 Outputs Outputs to amplifiers: Output Signal LOW OUT After LP650×2 (LF) MID OUT After HP650×2 → LP2500×2 (MF) HIGH OUT After HP2500×2 (HF) Each output: Series resistor 100–220 Ω (prevents possible oscillations and simplifies cable management). A nearby own AGND pad (ground output), so the signal pair SIG+GND runs together. Outputs should be compactly placed on 2-pin connectors (SIG+GND) or 3-pin (SIG+GND+reserve). 9. PCB DESIGN REQUIREMENTS 9.1 Board Number of layers: 2 layers Bottom layer: solid analog ground (AGND). 9.2 Component Placement Key principles: RC chains of each filter (R1, R2, C1, C2, Rf, Rg) should form a compact "island" around the corresponding op-amp. If elements are placed too far apart, the filter will not work correctly (calculated frequency and Q will shift). Feedback tracks (Rf and Rg) should be as short and direct as possible. The AM4T-4815DZ module should be placed: Far from the input buffer, Far from the first filter stages, If necessary, make a "cutout" in the ground under it to limit noise propagation. Place the input connector, RF-filter, and buffer on one side of the board, and the output connectors on the opposite side. 9.3 Ground The entire audio circuit uses one analog ground: AGND. Connect AGND to the power ground (48 V and amplifiers) at one point ("star"). The star should be implemented as: One point/pad where: The ground of the input, The ground of the filters, The ground of the outputs, The ground of the DC/DC. Avoid long narrow "ground" jumpers — use wide polygons with a single connection point. 9.4 Placement of Output Connectors Group LOW/MID/HIGH compactly. Each should have its own GND pad nearby. Route the SIG+GND pairs as signal pairs, avoiding large loops. 10. ADDITIONAL ELEMENTS: PROTECTION, TEST POINTS 10.1 Test Points (TP) Be sure to provide test points (pads): TP_IN — crossover input (after buffer) TP_LOW — LF filter output TP_MID — MF filter output TP_HIGH — HF filter output TP_+15, TP_–15, TP_GND — power control This greatly simplifies debugging with an oscilloscope. 10.2 Power Protection On the 48 V input — it is advisable to provide: Diode/scheme for reverse polarity protection (if possible), TVS diode or varistor for voltage spikes (optional). 10.3 Possible Stability Correction Pads for small capacitors (10–47 pF) in parallel with Rf in buffers and, if necessary, in some stages — in case of stability issues (this can be not installed in the first revision, but footprints should be provided). 11. BILL OF MATERIALS (BOM) Operational Amplifiers: NE5532 — 4 pcs (filters) NE5532 — 1–2 pcs (input buffer and balanced input) Total: 5–6 NE5532 packages. Resistors (1%, metal-film): 24.9 kΩ — 8 pcs 6.34 kΩ — 8 pcs 10 kΩ — ≥ 12 pcs (feedback, buffers, etc.) 5.9 kΩ — 8 pcs 22 kΩ — 1–2 pcs (input, auxiliary chains) 47–100 kΩ — several pcs (DC-block, input) 100 kΩ — 1 pc (if needed) 100–220 Ω — 4–6 pcs (outputs, RF, protection) 4.7–10 Ω — 2 pcs for each op-amp or group of op-amps (power filtering) — quantity to be clarified during routing. Trimmer Resistors: 10–20 kΩ multi-turn — one for each band (LOW, MID, HIGH) 10–20 kΩ — 1–2 pcs for the input buffer (overall gain adjustment). Capacitors: 10 nF film — 16 pcs (RC filters) 2.2–4.7 µF film — 1–2 pcs (input DC-block) 10–22 µF electrolytic — 2–4 pcs (DC/DC outputs) 1–4.7 µF (X7R / tantalum) — 1 pc for local power filtering (optional). 100 nF ceramic X7R — 10–20 pcs (local decoupling for each op-amp) 470–1000 pF — 1–2 pcs (RF filter on the input) 10–47 pF — optional for stability correction (Rf). Power Supply: AM4T-4815DZ — 1 pc Inductor 10–22 µH (if LC filter) — 1 pc R 1–2 Ω / 1–2 W — 1 pc (if RC filter). Connectors: Input (RCA + 3-pin for internal input) Balanced (XLR/TRS or 3-pin header) Outputs LOW/MID/HIGH — 2-pin/3-pin connectors. 12. TESTING RECOMMENDATIONS 12.1 First Power-up Apply ±15 V without installed op-amps. Check with a multimeter: +15 V –15 V No short circuits in the power supply. Install the op-amps (NE5532). Apply a sine wave of 100–200 mV RMS (signal generator). Check with an oscilloscope at TP: LP650 — should pass LF and roll off everything above 650 Hz. HP650 — should roll off LF, pass everything above 650 Hz. LP2500 — should roll off above 2500 Hz. **HP250 0** — should pass everything above 2500 Hz. 12.2 Phase Check The Linkwitz–Riley 4th order should give a flat frequency response when summed at the crossover points. This can be verified with REW/Arta. 12.3 Noise Check If there is noticeable "shshsh" or whistling: Check: Grounding layout (star) Placement and filtering of AM4T-4815DZ Presence and proper installation of all 100 nF and local filters. 13. FINAL RECOMMENDATIONS FOR BEGINNERS Do not rush, build the circuit step by step: input → buffer → one filter → test, then continue. Check component values at least twice before soldering. Filters should be routed as compact "islands" around the op-amp, do not stretch R and C across the board. Always remember the rule: "The feedback trace should be as short as physically possible." Before ordering the PCB, make a "paper prototype": print at 1:1, cut it out, place real components to check everything fits.

Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C. R2 changes: -Moving to Letter Modules for ease of design -Adding ESP32 for WiFi On/Off and intensity control -Optional: Add unpopulated AA Battery Holder for battery option R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: Adjustable Brightness, 85-90% Drive Efficiency <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC

Create a schematic diagram of an electric fence controller using the NE556 dual timer IC. The circuit must include all components with clear electronic symbols (resistors, capacitors, transistors, diode, relay) connected by lines as in a real circuit diagram. Specifications: 1. Power supply: - Vcc = +12V connected to pin 14 of the NE556. - Pin 1 of the NE556 to ground. 2. Timer A (active 10 seconds): - Pin 2 (Trigger A) receives a pulse from transistor Q2 (contact detector). - Pin 6 (Threshold A) connected to Pin 7 (Discharge A). - R1 = 1 MΩ between Pin 7 and +12V. - C1 = 10 µF between Pin 6 and ground. - Pin 3 (Out A) goes through a 4.7 kΩ resistor to the base of Q1 (BC547 NPN transistor). - Pin 3 also connected via a 100 nF capacitor to Pin 13 (Trigger B of Timer B). 3. Timer B (rest 10 seconds): - Pin 9 (Discharge B) and Pin 8 (Threshold B) connected together. - R2 = 1 MΩ between Pin 9 and +12V. - C2 = 10 µF between Pin 8 and ground. - Pin 12 (Out B) can be optionally used to block retrigger of Timer A. 4. Relay driver stage: - Q1 = BC547 NPN transistor. - Base connected through 4.7 kΩ resistor to Pin 3 (Out A). - Emitter to ground. - Collector connected to one side of the relay coil. - Other side of relay coil connected to +12V. - A diode 1N4007 placed in parallel with the relay coil (cathode to +12V, anode to collector of Q1). - Relay contacts switch the +12V supply to the electric fence energizer. 5. Contact detector: - Shunt resistor ≈0.1 Ω placed in series with the fence output. - Q2 = BC547 NPN transistor, base connected to the shunt, emitter to ground, collector to Pin 2 (Trigger A). - When current flows through the shunt, Q2 provides a trigger pulse to Timer A. Please draw the schematic in a standard style with components connected by straight lines, not in block diagrams. Show clear pin numbers of the NE556 and all external components.

Circuit Overview The circuit you're describing is a digital counter that uses an LDR (Light-Dependent Resistor) and a transistor to detect wheel rotations. The counter's output is then displayed on a seven-segment LED display. Here's a breakdown of the components and their roles: 1. Wheel Rotation Detection (LDR and Transistor) * LDR: The LDR acts as a sensor to detect changes in light intensity. You can mount it on the wheel' or near it, with a reflective or non-reflective surface attached to the wheel. As the wheel rotates, the LDR will be exposed to alternating light and dark conditions, causing its resistance to change. * Transistor: The transistor (e.g., a 2N2222 NPN BJT) is used as a switch or amplifier. The changing resistance of the LDR is used to control the base current of the transistor. When the LDR's resistance drops (more light), the transistor turns on, and when the resistance increases (less light), the transistor turns off. This converts the analog change in light into a digital ON/OFF signal (a pulse). 2. Counter (7490) * 7490 IC: This is a decade counter, meaning it can count from 0 to 9. The output of the transistor (the pulses) is fed into the clock input of the 7490. Each pulse represents one rotation of the wheel, and the 7490 increments its count accordingly. The 7490 has four outputs (Q0, Q1, Q2, Q3) that represent the BCD (Binary-Coded Decimal) equivalent of the count. 3. BCD to Seven-Segment Decoder (7446) * 7446 IC: The 7446 is a BCD-to-seven-segment decoder/driver. Its job is to take the 4-bit BCD output from the 7490 and convert it into a signal that can drive a seven-segment LED display. It has seven outputs (a, b, c, d, e, f, g), each corresponding to a segment of the LED display. 4. Seven-Segment LED Display * Seven-Segment Display: This display is used to show the count. The 7446's outputs are connected to the corresponding segments of the display. 5. Power Supply and Other Components * Power Supply: A regulated DC power supply (e.g., 5V) is needed to power all the ICs and components. * Resistors: Resistors are used for current limiting (e.g., for the LDR and the LED display) and biasing the transistor. * Capacitors: A capacitor might be used for debouncing the signal from the transistor to prevent multiple counts for a single rotation. Conceptual Connections Here is a step-by-step breakdown of how the components would be connected: * LDR and Transistor: * The LDR and a current-limiting resistor are connected in series across the power supply. * The junction between the LDR and the resistor is connected to the base of the NPN transistor. * The emitter of the transistor is connected to ground. * The collector of the transistor, with a pull-up resistor, becomes the output for the pulse signal. * Transistor to 7490: * The output from the transistor's collector is connected to the clock input of the 7490 IC. * The 7490's reset pins (MR and MS) should be connected to ground for normal counting operation. * 7490 to 7446: * The BCD outputs of the 7490 (Q0, Q1, Q2, Q3) are connected to the BCD inputs of the 7446 (A, B, C, D). * 7446 to Seven-Segment Display: * The outputs of the 7446 (a, b, c, d, e, f, g) are connected to the corresponding segments of the seven-segment display. * Crucially, you need to use current-limiting resistors (e.g., 330Ω) in series with each segment to protect the LEDs from high current. * The common terminal of the seven-segment display is connected to the power supply (for a common anode display) or ground (for a common cathode display). This setup creates a chain reaction: wheel rotation changes light, which changes LDR resistance, which turns the transistor on/off, generating a pulse. This pulse increments the 7490, and the 7490's output is decoded by the 7446, which then displays the count on the seven-segment LED.

R2 w Thread changes: -Moving to Letter Modules for ease of design -Adding MGM210L for Matter on Thread On/Off and intensity control -Shifted A and R letters closer to fix Kerning -Optional: Add unpopulated AA Battery Holder for battery option R1 changes: -Changed LED part to Red LEDs -adjusted resistor value of buck converter -Changed source for USB-C Connector -Removed exposed soldermask on buck converter with negative soldermask expansion -Order with black soldermask Modified by markwu2001: - Adjustable Brightness, - 85-90% Drive Efficiency - <5W Operation (Can use 5V 1A Plug) This project can be purchased from LCSC Original Description: Daddy's second circuit board. A sign to let my wife know when I'm on a call. Activates with a slide switch and is powered by USB-C. #template #arduino-matter