Going by car the highway with your high-beam headlights can actually increase your visibility, but can be a blinding hazard for other drivers. This easy circuit can be connected into your headlight swap to provide automatic swaping between high and reduced beam headlights when there is oncoming traffic. It does this by feeling the lights of that traffic. In this way, you can propel securely with your high-beams on without blinding other drivers.
Automatic Headlight Brightness Switch Circuit Diagram
- Q1 should me mounted in such a way so it points toward the front of the car with a clear line of site.
- Suitable places are on the dashboard, in the front grill, etc.
- Adjust all the pots for proper response by testing on a deserted road.
- S1 enables and disables the circuit.B1 is, obviously, in the car already.
- Before you try to connect this circuit, get a wiring diagram for your car.
- Some auto manufacturers do weird things with wiring.
- Connection A goes to the high beam circuit, B goes to the headlight switch common and C connects to the low beam circuit.
| R1 | 1 | 5K 1/4W Resistor | |
| R2, R3, R4 | 3 | 5K Pot | |
| Q1 | 1 | NPN Phototransistor | |
| Q2 | 1 | 2N3906 PNP Transistor | |
| K1 | 1 | Low Current 12V SPST Relay | |
| K2 | 1 | High Current 12V SPDT Relay | |
| S1 | 1 | SPST Switch | |
| B1 | 1 | Car Battery | |
| MISC | 1 | Case, wire, board, knobs for pots |
