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The lights boards will contain the lights themselves, the hardware necessary to keep them running in a stable manner, and components for heat dissipation. They will be controlled by rear power distribution and front power distribution.
Regulations:
https://www.worldsolarchallenge.org/files/2272_2019_bwsc_regulations_release_version_3.pdf
http://americansolarchallenge.org/ASC/wp-content/uploads/2019/02/ASC2020-Regs-EXTERNAL-RELEASE-A.pdf
WSC:
2.24.1 Solar cars must be fitted with:
- two rear stop lamps
- one central stop lamp
- left and right front direction indicator lamps
- left and right-side direction indicator lamps
- left and right rear direction indicator lamps.
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Stop lamps must emit red light. Direction indicator lamps must emit amber light.
2.24.3 Lamps must be compliant with UNECE Regulations 6, 7 and 37, or the SAE/DOT equivalents. Teams must demonstrate compliance by either:
- the presence of compliance markings on the lamps, or
- detailed documentation that demonstrates compliance with the photometric requirements of the UNECE or SAE/DOT regulations, confirmed by the certifying engineer. Lamps approved for motorcycles may not meet these requirements.
2.24.4 Solar cars must have the correct type of lamp in each position. For example, side marker lamps may not be used as stop lamps. Lamps must be mounted with the correct orientation so that the photometric requirements of UNECE Regulations 6, 7 and 37, or the SAE/DOT equivalents, are met. Lamp position and visibility requirements are based on UNECE Regulation 48.
2.24.5 Rear stop lamps must be within 400 mm of the extreme outer edge of the solar car on each side, at least 600 mm apart (at least 400 mm apart if the solar car is less than 1300 mm wide), and at least 350 mm above the ground. The entire apparent surface must be visible 15° up, 5° down and 45° to the left and right.The “apparent surface” of a lamp includes all parts of the lamp surface that emit light and are not obscured by other parts of the light-emitting surface.
2.24.6 A central stop lamp is required. Viewed from behind the solar car, the lateral position of the lamp must coincide with the visual centre of the solar car (see the examples in the following diagram). The lamp must be higher than a point 150 mm below the rear windscreen or canopy, and the bottom of the lamp must be higher than the top of the rear stop lamps. The entire apparent surface must be visible 10° up, 5° down and 10° to the left and right.
2.24.7 Front and rear direction indicator lamps must be within 400 mm of the extreme outer edge of the solar car on each side, at least 600 mm apart (at least 400 mm apart if the solar car is less than 1300 mm wide), and at least 350 mm above the ground.
2.24.8 Side direction indicator lamps must be less than 1800 mm behind the front most part of the solar car and within 400 mm of the extreme outer edge of the solar car on each side.
2.24.9 The entire apparent surface of direction indicator lamps must be visible 15° up and 5° down. Minimum horizontal visibility requirements (of the right direction indicator lamps) are shown in the following diagram.
Direction indicators for the front of the vehicle:
Category 1:For use at a distance not less than 40 mm from the dipped-beam headlamp and/or the front fog lamp;
Category 1a:For use at a distance greater than 20 mm but less than 40 mm from the dipped-beam headlamp and/or the front fog lamp;
Category 1b: For use at a distance less than or equal to 20 mm from the dipped-beam headlamp and/or the front fog lamp.
Categories 2a and 2b: Direction indicators for the rear of the vehicle.
Category 2a:Rear direction indicator lamps with steady luminous intensity.
Category 2b:Rear direction indicator lamps with variable luminous intensity.
Categories 5 and 6: Supplementary side direction indicators for use on a vehicle also equipped with categories 1, 1a or 1b and 2a or 2b direction indicators
https://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2015/R006r6e.pdf
https://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2015/R007r6e.pdf
https://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/R037r7e.pdf
ASC:
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Must be red. It is permissible to have one set of lights per side of the car which operate as both the brake lights and turn indicators. The turn indicator operation has the priority in operation.
Note that this is not permissible by WSC standards.
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All lights must be clearly visible and at least as bright as the reference standard from 30m away.
The reference standard lights are:
TruFLEX
20 LED (Length 3.35 in)
Item TF20 from Custom Dynamics
Red lights are Red LED with Red lens
Amber lights are Amber LED with Amber lens
(www.CustomDynamics.com 1-800-382-1388)
White lights are TF6WC for the BPS Fault Indicator Light and Daytime Running Lights/Headlights
The reference standard lights will be used in the following manner:
Lights shall be powered by a 12 volt power source
Light shall be centered on a flat surface with a matte white finish of 11” x 8.5”.
Separate light boards shall be used for each color type as the standard reference.
Reference standard light boards shall be set aside of car to compare during inspections.
Parts:
Red Lights
Amber Lights
White Lights
Optimizing PCB thermal performance:
https://www.cree.com/led-components/media/documents/XLamp_PCB_Thermal.pdf
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Design
Drivers:
https://www.digikey.ca/product-detail/en/texas-instruments/TPS61165DBVR/296-27597-1-ND/2340765
Prototype Rev 1:
3 LEDs in series with no additional parts. Lights were sufficiently bright and stable, but became very hot (around 80 C) very quickly.
Prototype Rev 2:
6 LEDs in series driven by a boost converter. PWM signal provided by 555 timer. Potentiometer included in 555 timer circuit to allow experimentation with duty cycles. LEDs and current sense resistors are kept on a separate board to account for the physical constraints of the car.
List of issues:
- Lack of decoupling capacitors
- Incorrect capacitor value for 555 timer (which set the incorrect frequency for the CTRL pin on the driver).
- Pins configured incorrectly
- Lack of ground pour for stability
- Inductor was not placed close enough to the potentiometer (no boost was measured).
Further Testing for Rev 2:
- Measure current at the connectors on startup to determine whether additional capacitors are required at the connectors.
- Measure power dissipation and efficiency of the driver.
Next Steps for Rev 3:
- Fix the obvious mistakes
- Determine whether heat dissipation for the LEDs is done through electrical ground (move current sense resistors to the main board if it is not).
- Calculate expected power dissipation of the driver, and determine expected temperature from it.
- Determine what voltage is required to replace the potentiometer and set the duty cycle of the PWM signal.
General Testing for Lights:
- Measure brightness of the LEDs.
- Ensure that the driver is boosting the voltage properly.
- Ensure that temperature is within safe limits (<100 C).
- Measure the stability of the LEDs by using a varying voltage.
- Measure the current and voltage on startup at the connectors.