Parts:
Red LightsLEDs
Color | Forward Voltage | Link |
|---|---|---|
Red | 2.2V | |
Amber |
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2.9V | https://www.digikey.com/product-detail/en/cree-inc/XPEBWT-L1-0000-00EE2/XPEBWT-L1-0000-00EE2CT-ND/ |
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Note: white lights have a forward voltage of 2.9V unlike red and amber lights, which have a forward voltage of 2.2V.
Drivers:
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Note: Lights Links should be double checked to give us the best binning possible (within reasonable price).
Drivers:
Driver | Topology | Applications | Link |
|---|---|---|---|
TPS61165 | Boost | DRLs only | https://www.digikey.ca/product-detail/en/texas-instruments/TPS61165DBVR/296-27597-1-ND/2340765 |
Heat sink:
Calculations:
maximum temperature of Rev3 Lights PCB = 50 C
ambient temperature (generous estimate) = 35 C
power dissipation (red or amber lights) = 2.2V * 6 LEDs * 0.35 A = 4.62 W
power dissipation (white lights) = 2.9V * 6 LEDs * 0.35 A = 6.09 W
Required thermal resistance (red or amber) = (50-35)/4.62 = 3.24 C/W
Required thermal resistance (white) = (50-35)/6.09 = 2.46 C/W
LM3406 | Buck | All except DRLs |
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LM3429 | Buck-Boost | All |
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PWM:
There is a PWM generator in the first versions of the design. It uses a 555 timer and a potentiometer to vary the duty cycle of the PWM signal.
I believe it is based off of this page here: https://www.electroschematics.com/pulse-generator-with-555/
We should adjust the values of the resistors and the potentiometers in order to be able to adjust the current limit of the LED driver from 50mA to 500mA.
Heat sink:
See thermal calculations here: Lights Thermal Calculations
Mechanical:
NOTE: Some of the pictures of the mechanical lights layout are no longer valid.
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, however this is to show that we are very constrained for our lights board layouts.
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Design
Optimizing PCB thermal performance:
https://www.cree.com/led-components/media/documents/XLamp_PCB_Thermal.pdf
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