Detecting Voltage Threshold (~14V) using Comparator (LM393) – Need Guidance

Blog entries Blog details
Hi everyone,

I want to design a simple circuit to detect voltage levels in a vehicle power line and generate a digital ON/OFF signal based on a threshold.

Requirement:
  • Input voltage range: ~12V to 14.5V
  • Condition:
    • Above ~14V → Output HIGH (Ignition ON)
    • Below ~14V → Output LOW (Ignition OFF)
What I Want to Do:
  • Use a comparator like LM393
  • Power the circuit directly from the same 12–14V line
  • Use a voltage divider to scale input
  • Generate a clean digital output
My Questions:
  1. What is the best way to set an accurate threshold around 14V using LM393?
  2. How should I design the voltage divider for both input and reference?
  3. Do I need hysteresis to avoid flickering due to voltage fluctuations?
  4. Is LM393 the best choice, or is there a better comparator for automotive use?
  5. Any protection components recommended for long-term reliability (noise, spikes, etc.)?
Goal:
  • Simple circuit
  • Reliable switching
  • Stable output (no flicker)
  • Works directly from vehicle supply
Would appreciate if someone can share a working circuit or recommended design approach
Top