Hand-solderable 9V battery powered 555 timer circuit that blinks a red LED once per second through an on/off switch.

Through-hole 9 V battery powered 555 timer circuit that blinks a red LED once per second using an on/off switch.

Hand-solderable 9V 555 timer circuit that blinks a red LED once per second through an on/off switch.

9V battery-powered NE555 astable blinker that flashes a through-hole red LED at roughly 1 Hz through an on/off switch.

9V battery-powered NE555 astable blinker that flashes a through-hole red LED at roughly 1 Hz through an on/off switch.

9V battery-powered 1 Hz red LED blinker using a through-hole 555 astable timer, on/off switch, and hand-solderable components.

Through-hole 9V NE555 red LED blinker circuit with on/off switch

9V battery-powered 555 astable timer circuit that blinks a through-hole red LED at about 1 Hz through an on/off switch.

Through-hole 1 Hz red LED blinker powered by a 9V battery through an on/off switch, using an NE555 astable oscillator on a 50 mm x 50 mm 2-layer PCB.

Hand-solderable NE555 astable LED blinker powered from a 9 V battery with an on/off switch and approximately 1 Hz blink rate.

Simple hand-solderable 9V battery LED blinker using a NE555 astable oscillator, on/off switch, battery snap connector, supply decoupling, and a red status LED blinking at approximately 1 Hz.

9V battery-powered 555 timer LED blinker with on/off switch and hand-solderable through-hole parts. Uses a DIP-8 LM555 in astable mode with 47k/47k/10uF timing for about a 1 second blink interval, a 100nF decoupling capacitor, and a red 5mm LED with 680 ohm series resistor.

Simple 9V battery-powered NE555 astable LED blinker with on/off switch, red indicator LED, and hand-solder-friendly through-hole components.

9V battery-powered NE555 astable LED blinker (~1 Hz) with on/off switch; through-hole hand-solderable parts.

Wearable health device prototype schematic with ECG sensing via AD8232, motion sensing via BNO085 or BMI270 IMU breakout, on-board processing using TI TM4C123G LaunchPad or MSPM0G3507 LaunchPad, optional ESP8266 Wi-Fi, LiPo battery charging with MCP73831, regulated 3.3 V power from TPS63031 buck-boost or AP2112 LDO prototype option, and user interfaces including electrode connector, JST battery connector, programming header, and optional on/off switch.

Battery-powered 555 timer LED flasher with on/off switch, timing network, and indicator LED output for simple oscillator testing and demonstration.

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

Hand-solderable 9V battery-powered red LED blinker using a 555 timer astable oscillator with an on/off slide switch.

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

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 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

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

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