Red LED Blinker Circuit Design

B

bryan

Make a circuit that blinks a red LED once per second.
Power it with a 9V block battery through an on/off switch.
Use components that are easy to hand-solder.

flux

I’ll build a hand-solderable 1 Hz red LED blinker using a 555 astable circuit, a 9V battery input, and an on/off switch. I’ll select through-hole parts, wire the datasheet-standard support capacitors, calculate the timing values, then run checks.

flux

Built the 9V hand-solderable 555 LED blinker schematic and documented the design in Project Specification. It uses a DIP-8 NE555P, 9V battery holder, SPST switch, 5mm red LED, through-hole resistors, timing cap, pin-5 bypass, and supply decoupling/bulk caps; calculated blink rate is about 1.06 Hz.
Validation found no remaining schematic/ERC issues; the only unresolved review items are PCB airwires, which are expected because placement/routing has not started yet. Ready to move to PCB layout when you confirm.
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Files

Schematic

Layout

3D View

R1 P2 - R2 P1
SW1 P3 - U1 VCC
R3 P1 - U1 OUT
GND
GND
R3 P1 - U1 OUT
C2
Capacitance
10nF
GND
U1 CONT - C2 P1
GND
GND
R2 P2 - U1 THRES
R3 P2 - LED1 A
R1 P2 - R2 P1
R2 P2 - U1 THRES
SW1 P3 - U1 VCC
SW1 P3 - U1 VCC
GND
U1 CONT - C2 P1
SW1 P3 - U1 VCC
BT1 + - SW1 P1
BT1 + - SW1 P1
SW1 P3 - U1 VCC
R2 P2 - U1 THRES
R2 P2 - U1 THRES
C3
Capacitance
100nF
R1 P2 - R2 P1
GND
SW1 P3 - U1 VCC
R3 P2 - LED1 A
C1
Capacitance
1uF
C4
Capacitance
10uF
R3
Resistance
1.5kΩ
LED1
U1
R2
Resistance
680kΩ
SW1
BT1
R1
Resistance
1kΩ
Project Specification: 9V Hand-Solder 555 Blinker
Requirements
  • Blink one red LED approximately once per second.
  • Power source: 9V block battery.
  • Include an on/off switch in series with the battery positive lead.
  • Use components that are easy to hand-solder, prioritizing through-hole packages.
Circuit Architecture
  • U1: NE555P in DIP-8 package, configured as a standard astable oscillator.
  • BT1: 9V battery holder/input.
  • SW1: SPST on/off switch between battery positive and the switched 9V rail.
  • LED1: 5mm through-hole red LED with series current-limit resistor.
555 Astable Timing
Standard astable topology:
  • R1 from switched 9V rail to DISCH.
  • R2 from DISCH to the TRIG/THRES timing node.
  • C1 from TRIG/THRES timing node to GND.
  • RESET tied to switched 9V rail.
  • CONTROL bypassed to GND.
Selected values:
  • R1 = 1kΩ
  • R2 = 680kΩ
  • C1 = 1uF
Calculated timing:
  • Frequency ≈ 1.06Hz
  • Period ≈ 0.94s
  • High time ≈ 0.472s
  • Low time ≈ 0.471s
LED Current Limit
  • LED forward voltage from LTL-307EE datasheet: approximately 2.0V typical at test current.
  • R3 = 1.5kΩ gives about 4.7mA from a 9V rail, suitable for visible blinking with reduced 9V battery drain.
Required 555 Support Components
  • C2 = 10nF from CONTROL pin to GND.
  • C3 = 100nF from switched 9V rail to GND near U1.
  • C4 = 10uF bulk capacitor from switched 9V rail to GND.
Nets
  • BAT_9V_RAW: battery positive before switch.
  • VCC_SW_9V: switched 9V rail after on/off switch.
  • GND: battery negative and common return.
  • DISCHARGE: 555 discharge node between R1, R2, and DISCH pin.
  • TIMING_NODE: 555 TRIG/THRES node with timing capacitor.
  • CONTROL_BYPASS: 555 CONTROL pin bypass node.
  • LED_DRIVE: 555 output to LED current-limit resistor.
  • LED_ANODE: current-limit resistor to LED anode.
Validation Notes
  • All NE555 power, ground, reset, timing, control, and output pins are connected.
  • The schematic includes required NE555 pin 5 bypass and supply decoupling/bulk capacitors.
  • Remaining DRC airwires are expected before PCB placement and routing; they will be resolved during the layout/routing phase after user confirmation.

  • Requirements

  • Circuit Architecture

  • 555 Astable Timing

  • LED Current Limit

  • Required 555 Support Components

  • Nets

  • Validation Notes