watonomous.github.io
[ Electrical Division : Autonomous Blue Light ]
Created by [ Rowan Dempster], last modified by [ Eric Li] on Mar 29, 2020
A flashing blue light is mounted on the top of the car, and is required to turn on when in autonomous mode and off when the car is in manual control. In order to control this light, a CAN bus signal (in need of a wiki link) is sent to an Arduino board, which then turns on an NMOS responsible for providing power to the blue light.
Although the package of the NMOS is quite small, it has been found to be adequate for the power draw of the blue light. According to tests where the blue light circuit has been running for >= 30 minutes, there is little to no increase in temperature of the NMOS body. The blue light circuit is sufficient to use without a heatsink or active cooling.
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Blue Light: Peak current (found empirically): 180 mA, Input voltage: 12V, Power draw: 2.16 W.
NMOS: LU024N [datasheet]. Max voltage: 55V, Max current: 17 A, Max power dissipation: 45 W.
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Old Documentation:
(The following information is outdated. The current blue light uses a different microcontroller and NMOS, but some of this info might still be useful)
A flashing blue light is mounted on the top of the car, and is required to turn on when in autonomous mode and off when the car is in manual control. In order to control this light, we will be using an ESP8266 that toggles on and off the power to the external light. The rugged will be able to communicate with the ESP8266 over WiFi, and a ROS node will keep track of specific topics that are present when in and out of autonomous mode. This node will send commands to the ESP8266 to turn on or off the light based on whether the car is on autonomous mode or not.
List of Parts:
ESP8266
Voltage Regulator
(https://www.mouser.ca/ProductDetail/AVX/F971D105MAAHT3?qs=sGAEpiMZZMsh%252B1woXyUXjwFoy9mQt0SS13hGPcnu%2Fd4=)
- This is needed since the ESP8266 runs on 3.3V but the car supplies 12V
12V Blue Light
N-MOSFET rated for > 12V Vds and 2.5V < Vgs < 4V
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Attachments:
blue_light_schematic.brd
(application/octet-stream)
blue_light_schematic.sch
(application/octet-stream)\
Document generated by Confluence on Nov 28, 2021 22:40