Typically all car turn signal lamps are around 12 to 20 watt rated which are traditionally incandescent bulb types and produce much lower light intensities compared to LED lights. Here we learn how these lamps can be replaced with high efficiency, high intensity car LED bulbs.
LED Car Bulb Design
The image below shows what could be a car LED lamp directly replaceable over the existing holder.
It shows a decent looking arrangement of flat, tiny SMD LEds in a circular pattern for enabling optimal distribution of light via the enclosed hind reflector.
The LED used here are the 3020 SMD LEDs, these tiny light emitting diodes are identical to the ordinary 5mm LEDs with their specs, however if we compare their light intensities, the witnessed difference appears to be huge, where the 3020 easily wins by an outstanding margin, that's why these LEDs are much preferred in place of the ordinary 5mm LEds nowadays.
Technical Specifications of the 3020 LEDs are:
- Forward voltage: 3 to 3.2V
- Forward current: 30mA optimal
- Luminous Efficiency: 100-110lm/w
- Size: 3.0x2.0x1.3mm
- Lifetime: 50,000hrs
In the above image, we can see the LEDs assembled over pcs of PCB strips, tiled in a particular calculated manner.
The vertical PCBs are 7 in numbers, and have 4 LEDs on each strips.
One circular PCB consisting of 22 LEDs can be seen positioned over the vertical PCB structure.
The vertical PCBs thus include 7 x 4 = 28 nos of 3020 LEDs, while the circular PCB mount 22 nos of LEds, giving a total of 28 + 22 = 50 LEDs
These 50 LEDs are connected to form 12 strings of 4 LEDs each, and a single string of 2 LEds.
Each of the 12 strings must have their own individual series resistor (SMD) whose value could be around 55 ohms 1/4 watt.
The single 2 LED string must associate a separate 250 ohm, 1/4 watt resistor.
These resistors act like current limiters for safeguarding the LEds from car alternator voltage fluctuations and also help to keep the illumination level across all the LED groups as uniform as possible.
The resistors can be installed at the rear side of the PCB strips.
The circuit diagram for the proposed simple car LED lamp is shown below: