ATmega328-Based Wall Outlet Offers Soft Start and Output Options

Electronic technician Yannick Turcotte has designed a wall outlet that offers a soft starter for table saws, as well as a second outlet that can engage with the first, or be used as a delay, shutting off the power after a specific time limit. Soft starters are great devices that temporarily reduce load and torque in the power train of electrical motors, thus reducing current surge during start-ups. These units are perfect for use with power tools and are great at lowering mechanical stress inflicted on their motors, which will extend their lifespan.

Turcotte designed his Table Saw Soft Starter around an ATmega328 microcontroller, a linear power supply with bridge regulator, an H11AA1 optocoupler, and a CSE187L current-sensing module. The electronics were soldered to a homebrew 1-layer PCB outfitted with transformers, and a pair of LEDs, all packed into a pair of electrical boxes coupled together.

Rounding out Turcotte’s build is a pair of outlets wired together, with one for a soft/hard start, and the other for engaging a delayed shutdown, with both connected to the board and controlled by the ATmega328. Turcotte coded his Table Saw Soft Starter with Atmel Studio and used Zadig to upload the code via USBasp or USBtiny. His project is an excellent build that won’t break the bank, and could save a few fingers down the road.