We have introduce LED signal module in previous. Today, we are talking about the LED Traffic Signal Module.
The electrical design of an LED traffic signal module would be completely different from an incandescent traffic signal head, but would use the same traffic signal controller. The incandescent design would use a 12ov ac-compatible lamp driven by a mechanical or a solid state relay. The LED design would probably incorporate an ac-to-dc circuit, because LED lamps are designed to operate from dc voltages with some type of external current limiting circuit.
A block diagram of a potential LED traffic signal circuit is shown to us, which designed to replace the incandescent lamp using the existing traffic signal controller. First, the 120v ac is full-wave rectified and filtered. The rectifier circuit produces an unregulated dc voltage of approximately 150v. The traffic signal module consists of an array of LED lamps mounted on a printed circuit board. Although it may be possible to drive the LED lamp printed circuit board. Although it may be possible to drive the LED lamp array directly from the ac line, such an approach leads to severe forward current variations and has the potential to subject the LED lamps to damaging electrical transients.
The design of the traffic signal module LED lamp array should consider several factors.
First, the forward current through the LED lamps should be regulated so as not to cause noticeable luminous intensity variations within the traffic signal module due to the effects of variations in ac line voltage, ambient temperature, and forward voltage of the LED lamps themselves.
Second, the circuit should be designed to minimize luminous intensity variations of the traffic signal module due to the effects of ac line voltage, ambient temperature, and LED electrical characteristic parametric variations.
