Archive for October 2017

Teardown of a Watts Up? Pro ES Power Meter

Power meters for measuring power consumption of consumer electronics have been around for at least a decade. The most popular ones are argubly P3 International‘s power meters and many of its clones. I have a later version of the P4400 which was based on a COB design. Some earlier manufactured P4400’s used off-the-shelf ICs. The Watts Up? power meters were first seen roughly around the same time as P3’s Kill A Watt meters. However, they never became as ubiquitous as the Kill A Watt due to their high prices. But compared to Kill A Watt power meters, Watts Up? meters do seem to offer better functionalities. The Pro series for example are equipped with USB interfaces and thus allow easy data logging and data analysis on computers. Continue reading ‘Teardown of a Watts Up? Pro ES Power Meter’ »

Diode Equation and Forward Current Measurement

We are all familiar with the I/V characteristics of a diode. The main characteristics of a typical diode is that when forward biased, it starts to conduct as the voltage applied approaches the threshold voltage of the diode and the current increases exponentially as the forward voltage increases. This behavior can be modeled by the Shockley diode equation. A question frequently asked is that what happens when the applied forward voltage is very small, say just a few millivolts? Continue reading ‘Diode Equation and Forward Current Measurement’ »

Modifying a Computer ATX Power Supply For Higher Output Voltage

To charge the 110Ah battery bank I built, I need a power supply that can provide at least 10A at 14.6V. Since I have many old ATX power supplies lying around and the 12V rails of these power supplies are more than capable of providing 10A, I decided to modify one such power supply for using as a 4S LiFePO4 battery charger. Continue reading ‘Modifying a Computer ATX Power Supply For Higher Output Voltage’ »

Teardown and Testing of an 800W PureSine Inverter

The last ingredient for my backup power project is an inverter. Since the battery bank I built is a 12V 1.5kWh one, an inverter that can handle a load between 500W and 1000W would be a suitable choice. In theory, all the lights and the refrigerator in my house consume just around 500W. So the 1.5kWh battery bank should be able to power all the essentials for at least a couple of hours in the event of a power failure. Continue reading ‘Teardown and Testing of an 800W PureSine Inverter’ »