Kerry D. Wong

In this blog post, let’s take a look at what’s inside an Extech 380460 miliohm meter.
Read more…

I bought a used RegVolt ATVR-1000D automatic AC voltage regulator (the model I got has long been discontinued, but you can find a current production model here) off eBay last week. This regulator was produced for the 110V market, but I suspect that with some adjustments I could get it to output 120V instead.
Read more…

As mentioned in my previous post, besides the broken LCD there was also an issue with the power supply portion of the unit and the output voltage was clamped at around 10 to 11V. The digital circuitry portion however seemed to be intact. Unfortunately since an identical LCD is virtually unobtanium, I thought I’d reverse engineer the LCD protocol so once the power supply is fixed I can fix the display by hooking up a different LCD.
Read more…

I recently picked up a BK Precision 1696 programmable switching power supply off eBay. Unlike many of the vintage test equipment I did teardowns with in the past, this model is still in production today. The one I got was sold with a damaged LCD screen and thus I paid very little for it. Of course, a brand new one would cost around $300.
Read more…

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.
Read more…

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?
Read more…

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.
Read more…

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.
Read more…

During the past couple of weeks I have been busy making a large battery bank using the eighty 32650 LiFePO4 cells I bought on eBay. The battery bank I am building is a 12V (13.2V nominal) 4S/20P one. With each cell rated at 5.5Ah the battery bank has a capacity of 110Ah, which is just under 1.5kWh.
Read more…

For those who are following my YouTube channel, you would know that I am in the process of building a high capacity battery bank. When this project is done, I plan to use it with a 12V inverter as my backup generator in the event of a power failure. For the battery bank, I used eighty 3.2V 5.5Ah 32650 lithium iron phosphate (LiFePO4) batteries. These are arranged into 4 groups in series and each group consists of 20 cells paralleled together forming a 12.6V 110Ah battery bank.
Read more…

I got a couple of Microsemi’s C900502 10.525 GHz X-band Doppler radar motion sensors a while ago. This batch was made in UK and had “UK patents 2243495 and/or 2253108 apply” printed on the case. I have seen a teardown of an HB100 Doppler radar module before and was wondering if I this one is any different inside.
Read more…

I bought six Philips dimmable LED bulbs for my dinning room chandelier last year. These are 45W incandescent equivalent (7W, 450 lm 2700K) and are supposed to provide years of trouble-free illuminations. Over the course of a year of light use however, they all exhibited the same failure mode at some point of time. Two months in, the first bulb failed. The bulb would initially turn on, but after a few minutes it would turn off by itself. If the power is recycled the light can be turned back on again but only for a short period of time, and the cycle continues.
Read more…

I have an old Keithley 1301 temperature probe. This probe is an accessory to the Keithley 130A/131 multimeter and is capable of measuring temperatures between -55°C to 150 °C. Since it outputs an analog voltage linearly proportional to the temperature (1mV/°C), it can be used with any multimeter that has a mV range.
Read more…

In my previous post, I did a review and teardown of a cheap BSide ACM03 Plus clamp meter and concluded that it was a surprisingly good meter despite a few minor annoyances.
Read more…

I recently purchased a BSide ACM03 Plus clamp meter so that I could do some high current measurements for my tab welder project. This meter can be bought on eBay for around $25, which makes it one of the cheapest Hall effect clamp meters on the market that is capable of measuring both AC and DC current.
Read more…