Background Story: Recently, while helping my friend in building his Automatic Cleaning filter, I designed driver circuit for Solenoid Valves and DC Motor. You can easily find enormous amount of How-To, tutorials, circuits on google. But they are specific with those applications. Simply they referred other designs and decided to use them in theirs. Most of them do not discuss about calculation involved for designing driver circuit according to power rating of the solenoids/relay/DC Motor. Depending upon the power rating of your Relay,Solenoid and DC Motor; selection of driver circuit is done. This post to address those issues, How to choose right driving element like Power Transistor, Power MOSFET etc. ? How to calculate sink or source current needed? How to safeguard your microcontroller from notorious back EMF of Relays and Solenoids? [Note: Principle involved in driving Solenoids and Relays are same, so covering Relays also] So...
My Adventures and Expereinces in Electronics Design & Developments,Open Source Hardware. Enjoy life by making, building, creating, designing, developing, Hacking and Innovating.