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Simple Voltage Switch For Car Sensors

This Simple Voltage Switch can be used anywhere you want a relay to switch when a voltage reaches a preset level. It has lots of applications in cars but can be used in any application where you have 12V DC available. Having switched the relay on, it will then switch if off as the voltage being monitored drops below the preset level.

Design by John Clarke

Main Features

  • Adjustable switching level between 0V and 16V at input
  • DPDT 5A relay
  • Configurable to switch on rising or falling voltage
  • Adjustable hysteresis
  • High input impedance – won’t load down sensors
  • Suggested Uses For the Voltage Switch

  • Intercooler water spray control (from air-flow meter, throttle position sensor or oxygen sensor signals)
  • Anti-lag turbo wastegate control (operating a wastegate disconnect solenoid triggered from the air-flow meter signal)
  • Nitrous oxide switching (from throttle position sensor signal)
  • Intercooler fan control (from air-flow meter signal)
  • Dashboard monitoring LED (eg, oxygen sensor output signal)
  • Switching in and out engine management and auto transmission control modifications (from air-flow meter, throttle position sensor or oxygen sensor signals)
  • Low battery voltage warning and/or disconnect

  • In car applications, many engine sensors have variable voltage outputs and these can be used for relay switching. For example, if your car has an air-flow meter with a voltage output (most cars have), then you can use that as an engine load signal to switch things on and off.

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