Written by Charles Banuelos MFG DM-updated 11/29/2017
The schematic below is for a hedge following shield that will connect directly to the 3DoT board. The hedge following shield will connect to the 3DoT board using the same 6 pin header that is used for the 3DoT IR shield. The design follows Thomas Forman’s designs from EE444. The color sensor being used is the BH1745NUC-E2CT-ND color sensor because this color sensor allows for two different I2C addresses to be used. The hardware is designed to have the I2C addresses (0x038) and (0x39) in HEX. The LEDs chosen were chosen due to the fact that they were able to fulfill the specs needed such as light transmission, package size and current. The LEDs are used to light up the areas for the color sensors to detect the hedges. The mosfet in the schematics is used to control the LEDs which are protected by resistors. There are protection 10k resistors placed at the address pins to ensure protection of the color sensor.
The schematics below do not contain any form of reverse polarity protection. It should be stated then that when inserting the PCB in the 3DoT header that the orientation should be carefully monitored as to not accidentally flip power and ground. This could cause catastrophic damage to the circuit. It should also be noted that future color sensors should include a diode on the power line right after the header to protect from this. This design chose not to go with this at the time due dimension requirements of the PCB.