LED Blinker Circuit Design

flux

Done — here’s the updated PCB layout PDF:
Download 9v-555-led-blinker.pdf
Note: the PCB layout still has unrouted airwires, so this PDF reflects the current layout state, not a finished routed PCB.
L

ltembedded

Route the remaining airwires and then regenerate the PCB layout PDF.

flux

I’ll route the remaining PCB airwires, verify the routing, then regenerate the PCB layout PDF.

flux

Routed the remaining airwires successfully — 58 routing nodes were added, and the follow-up DRC check shows no open airwire, overlap, dangling trace, missing-footprint, or invalid-layer issues.
Download the regenerated PCB layout PDF
L

ltembedded

Generate a STEP model for mechanical review.

flux

I’ll generate the STEP model from the current routed PCB layout for mechanical review.

flux

Done — the routed PCB passed the key pre-export checks, and I generated the STEP model for mechanical review:

3D Model (STEP)

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Assembly drawing
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Files

Schematic

Layout

Preview

U1
Project Specification
Purpose
Hand-solderable red LED blinker powered by a 9V block battery through an on/off switch.
Circuit Topology
  • NE555P in PDIP-8 through-hole package configured as an astable oscillator.
  • 9V battery positive enters J1, passes through S1, then powers the switched 9V rail.
  • Red 5mm LED is driven from the 555 output through a 680Ω current-limiting resistor.
Timing Calculation
Astable frequency formula:
f = 1.44 / ((R1 + 2 * R2) * C1)
Selected values:
  • R1 = 1kΩ
  • R2 = 680kΩ
  • C1 = 1uF
Calculated result:
  • Frequency ≈ 1.06Hz
  • Period ≈ 0.94s
This meets the requested “once per second” blink rate within normal through-hole passive tolerances.
Required 555 Support Components
  • C2 = 10nF from CONTROL pin to GND.
  • C3 = 100nF from VCC to GND near U1.
  • C4 = 10uF bulk capacitor from switched 9V rail to GND.
  • RESET pin tied to switched 9V rail.
Power Budget
Estimated load:
  • NE555 operating current: approximately several mA typical.
  • LED current through 680Ω: roughly 8–10mA depending on NE555 output voltage and LED forward voltage.
  • Total expected operating current: about 15–25mA peak.
Battery connector and switch are rated far above this low-current load.
Hand-Soldering Choices
  • NE555P PDIP-8 package.
  • Through-hole 5mm red LED.
  • Through-hole axial resistors.
  • Through-hole disc/radial capacitors.
  • Through-hole battery snap and toggle switch.
Validation Notes
ERC was run after wiring and returned no open electrical errors or warnings. DRC airwires remain expected because the PCB layout has not been placed or routed yet.

  • Purpose

  • Circuit Topology

  • Timing Calculation

  • Required 555 Support Components

  • Power Budget

  • Hand-Soldering Choices

  • Validation Notes