What are the control methods of automotive circuits?
4 Answers
Automotive circuit control methods include: 1. Power circuit: Also known as the charging circuit, it consists of the battery, generator, regulator, and charging indicator device; 2. Starting circuit: Composed of the starter, relay, starting switch, and starting protection circuit; 3. Lighting and light signal device circuit: Includes headlights, fog lights, clearance lights, turn signals, brake lights, reverse lights, interior lighting, and related control relays and switches; 4. Ignition circuit: Consists of the ignition coil, distributor, electronic ignition controller, spark plugs, and ignition switch; 5. Instrument information system circuit: Made up of instruments and their sensors, various warning indicators, and controllers; 6. Electronic control system circuit: Comprises the engine control system, automatic transmission and cruise control system, anti-lock braking system, and airbag control system.
The evolution of automotive circuit control methods is quite fascinating. In the early days, mechanical switches were used for direct control, like in my family's Santana from the 1990s, where the turn signal switch would creak and was prone to poor contact. The introduction of relay control was much smarter—the switch only needed to control a low-current coil, while the relay contacts handled high-current devices, protecting the switch and extending its lifespan. Modern cars mostly rely on electronic modules. For example, pressing a window button sends a signal to the body control module, which then drives the motor to raise or lower the window. In recent years, new-energy vehicle manufacturers have taken it even further, with domain controllers capable of managing multiple systems uniformly, and OTA updates allowing remote rewriting of control logic. While control methods are becoming increasingly intelligent, the simplicity and reliability of traditional relays remain practical in emergency situations.
When it comes to automotive circuit control, I believe it can be mainly divided into three levels. The most basic is hard-wired control, where switches are directly connected to electrical devices, like the old-style cigarette lighter that powers on as soon as it's plugged in. The intermediate version uses relays as intermediaries—for example, the headlight switch controls the relay contacts to turn on or off, preventing high current from damaging the switch. The most advanced is network control, where modern mainstream vehicles rely on CAN bus systems. The body control module receives sensor data and sends commands, which is how functions like braking and throttle control during autonomous driving are achieved. Different systems also employ different control methods: the engine control unit manages fuel injection, while the body control module handles windows, doors, and wipers. As control logic becomes increasingly complex, using a diagnostic tool to read fault codes has become essential for reliable vehicle repairs.
I've researched circuit control when modifying car lights. Regular bulbs can light up by directly connecting to a switch, but LEDs require a driver module to stabilize the current. Common control methods include mechanical switches for simple devices directly, relays for high-power equipment to protect circuits, and controller area network communication protocols for control. For example, automatic headlights work by the light sensor sending signals to the body computer, which then controls the relay to turn on or off. High-end cars also use multiplexing technology to reduce wiring harnesses, such as BMW using a single wire to transmit multiple signals to control windows and mirrors. Different control methods result in different fault manifestations, with fuse blowouts mostly occurring in direct control circuits.
