LED Blinker Circuit Design

flux

What I added (through-hole, hand-solderable)

Table

FunctionComponent
555 timerU1
Timing resistorsR1, R2
Timing capacitorC1
Decoupling + bulkC2, C3
LED + current limitLED1, R3
9V battery inputBT1
On/off switchSW1
Reverse polarity protectionD1
Light load / bleederR4
How it’s wired (functional astable blinker)
  • Power path: BT1 -> SW1 -> D1 -> U1 VCC
  • 555 astable: R2, R1, C1 (TR/THR tied together)
  • LED drive: U1 OUT -> R3 -> LED1 -> GND
  • Decoupling: C2 across VCC/GND, C3 at power entry
Verified sizing (LED resistor)
  • R3 = 700 ohm gives about 10 mA assuming Vf ~2 V.
  • Power in R3 at 10 mA is about 0.07 W, so a typical 1/4 W axial resistor is fine.
Status of checks (what still fails)
  • The circuit is connected, but ERC/DRC is NOT clean yet:
    • ERC Missing Power still flags U1.
    • DRC Manufacturer Part Number flags all Generic passives: R1, R2, R3, R4, C1, C2, C3.
These two issues prevent me from claiming the “ERC/DRC shows no errors” success criterion yet.
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