Loss of a 240v Voltage Leg of an Electric Dryer What happens when a loose connection at the junction box or terminal block on an electric dryer causes one of your line voltages to drop out? Here are the equivalent circuits and how to test for this loss. Figure 1 is a simplified equivalent circuit […]
How Linear and Switching Power Supplies Work Linear and Switching Power Supplies (SMPS – switched mode power supply) are the two primary types of supplies found in Appliances, Televisions, and HVAC units., The respective design and operation of Linear vs. Switching Power Supplies is quite different. Figure 1 shows an actual linear power supply for […]
Intro – Resistor Voltages and Currents – The Basics Reading schematics can sometimes be confusing for Appliance and HVAC technicians. Particularly determining voltages across or current through components. These voltages and currents are well defined by Ohm’s Law though. No matter how a network of components are arranged in a circuit, there is a formula […]
What Does Line Voltage Look Like? Appliance and HVAC technicians frequently deal with residential line voltage. Failures in appliances and HVAC systems are sometimes caused by mis-wired, loose, or disconnected components. Understanding the behavior of voltages when they are missing or mis-wired can aid in troubleshooting. A 60Hz, 120V RMS voltage is determined by multiplying […]
Intro to Reading Schematics – A Basic Whirlpool Electric Dryer This article will schematically show where voltages appear in a Whirlpool Dryer circuit for different operating modes and failure states. This information can be useful to technicians that want to use voltage checks in addition to their other troubleshooting methods. Please note that this article […]
Important Note This blog is intended for experienced or supervised technicians. Always take appropriate safety precautions when dealing with live circuits. For informational purposes only. Never attempt to repair circuit boards in appliances or HVAC systems unless you are directly supervised by a professional engineer and doing so under approved ISO and UL processes. Alphabetical […]
Using voltage drops in addition to static resistance checks and dynamic current flow measurements can greatly improve your ability to effectively troubleshoot HVAC and Appliance issues. Don’t forget:“Diverting 10 min/day of social media time towards learning something new, is 5 hours of newfound monthly knowledge.” – SM To DONATE to the Tech Circuit – CLICK HEREAlphabetical […]
Introduction: PWM, or Pulse Width Modulation, aside from being the preferred method for controlling LED lighting, is a common way to control DC motors as compared to simple varied DC voltage. This is because with PWM, the motor still receives full power in the form of pulses, while at the same time, varied average power […]
Intro – What is a Relay Driver or Relay Control Circuit? A relay driver circuit acts as a buffer between the control board´s intelligence and the relatively high current drawn from the relay coil. A microcontroller typically will output a high or low logic level (3.3 or 5v for a high, and 0 volts for […]
Welcome to The Tech Circuit, where the focus is: “Electronics for Field Techs”. The Tech Circuit is all about electronic troubleshooting, theory, circuits, reading schematics, and every other electric or electronics topic as it applies to Appliances, HVAC, and other Field-Tech disciplines. The purpose is to help field technicians better understand the underlying electrical/electronic reasons […]