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

Through-hole 9V NE555 astable timer circuit that blinks a red LED about once per second using a battery and on/off switch.

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