Quinn
Quinn is a six-channel Pulse-Width Modulation driver controlled via the Internet. Quinn’s design was motivated by a desire to control strings of RGB LED tape lights, which draw considerable power. The board is powered by the 12V supply typically used by RGB lights, and is capable of providing 5A spread over its six channels.
Far from being limited to driving RGB tape lights, Quinn’s design is excellently suited for many applications — other lighting devices such as color temperature LED fixtures, simple on/off switching of high-current DC devices, or servo control. Quinn’s design also includes catch diodes (marked DNS, D2-D7), which allow the board to be used to drive and control inductive loads such as motors without damaging the FETs.
Quinn’s overall design is quite simple. The board is powered with a 12V DC supply (included in BoM). Diode D1 provides reverse-voltage protection by blocking ground return current in the event that reverse voltage is applied. The TPS62172 buck regulator is used to provide a reliable 3.3V supply for the imp and the required ATSHA204 ID chip.
Each of the imp001’s six user-available pins is used to control a single channel; each line runs to the gate of a DMN2075U FET. This FET has excellent current handling (4.2A each), low threshold voltage (max 1V), very low RDS-on, and high maximum drain-source voltage (20V). Connecting Quinn to RGB tape lights as shown, the 12V supply is routed out to the anode of the LEDs, and the FETs are connected to the cathodes for low-side drive. By regulating the duty cycle of a pulse-width modulated signal to each channel, the relative brightness of each color can be controlled, allowing the user to select any specific color.
Device Firmware and Example Code
Revision-controlled example firmware for the Quinn board is available on the Electric Imp GitHub examples page.