Kerry D. Wong

Not all cables have proper strain relief built to the connector ends. This is particularity true for some of the iPhone 6 USB to Lightning™ cables. Take this Anker branded iPhone cable for example, after several months’ normal use the cable towards the USB end started to show signs of excessive strain (see image below). The internal wiring would soon be damaged if the strain on this area continues. Continue reading ‘Adding Strain Relief to an Existing cable’ »

I have received quite a bit of positive feedback since I wrote about the hacks on DTM0660L based multimeters last time. So I went ahead and translated the original Chinese datasheet into English and the PDF datasheet is linked below: Continue reading ‘DTM0660 Datasheet Translated’ »

A couple of months ago, I converted my EP200Mmd monochromator into a scanning monochromator and tested the spectrums of quite a few light sources. This time, I will take take a look at the spectrums of three cheap eBay laser pointers using the same technique. Continue reading ‘The Spectrums of Three Cheap Laser Pointers’ »

You can generate some pretty amazing patterns by shining a laser onto a mirror mounted on a vibrating speaker cone, a lot of people have experimented with this kind of laser show. But how about building a true laser oscilloscope that is capable of displaying signals? In this post, I will show you just that. For those who are impatient, I included a video towards the end. Continue reading ‘Building A Laser Oscilloscope’ »

I recently bought a few old power transistors from eBay. These are PNP Tung-Sol germanium transistors. According to the date code (6326) these transistors were made back in 1963, long before I was born. The last time I actually used a germanium transistor was more than twenty years ago when I was learning to make transistor radios. Continue reading ‘An Old Tung-Sol Germanium Transistor’ »

I just moved my site from my own server to linode‘s VPS hosting. So you should see some pretty significant performance improvement down the road. Continue reading ‘Server Moved to Linode’ »

I bought a couple of Peltier cooler modules on eBay a while ago for some experiments. Of course, as I expected the quality of those cheap modules were pretty poor. After a couple of hours of continuous operation, both modules failed. So I decided to take a look to see if they could be repaired. Continue reading ‘Peltier Cooler Module Repair’ »

I wrote a tutorial a while ago on how to hand solder fine pitched LGA/QFN chips using perfboards. While The technique illustrated works well with low pin count chips, for many people it is still a rather daunting task to solder these tiny chips that way. Also, as the pin count increases hand soldering without using a board with proper footprint becomes much harder. Continue reading ‘QFN Soldering Using SchmartBoard’ »

My seven year old 24 inch LCD monitor (Westinghouse L2410NM) started to flicker recently, so I decided to take a look inside to see what was wrong. Even before I opened it up, I had a pretty good idea of what might be the culprit. These older LCDs use CCFLs for back-lighting. CCFLs are typically quite robust. While it is not totally impossible, it is rather rare to see a failed CCFL. So most likely the issue is related to the power supply module. Continue reading ‘Westinghouse L2410NM LCD Power Supply Repair’ »

I bought an old Tektronix 2445 150 Mhz oscilloscope on eBay the other day. It was listed under “For Parts/Not Working” condition. Since the pictures in the auction listing suggested that the scope powers up and shows traces on all channels, I thought I would get it and fix it up. Continue reading ‘Tektronix 2445 Teardown’ »

The current sourcing/sinking capability of the I/O pins on Raspberry Pi is quite limited. According to the Wiki page, the current limit for each I/O block (e.g. GPIO0 through GPIO27 combined) comes at only 26 mA maximum, which is only capable of driving a couple of LEDs at a time. Also the I/O pins are 3.3V only, and going beyond the current or voltage limit could result in permanently damages to the chip. Continue reading ‘A Bidirectional Level-Shifting Buffer for Raspberry Pi’ »

I got a used BK Precision 4011 5MHz function generator recently. The 4011 model is rather old and this particular unit was manufactured back in 1996. But BK precision still makes a similar model (4011A) which is identical to the older 4011 spec-wise except for the inclusion of an additional INV button for inverting the output waveform. Continue reading ‘BK 4011 Function Generator Teardown’ »

I got myself a Raspberry Pi (Model B V2) last month. After having played with it for a while, I have to say that I really like this tiny single-board computer. Since it runs on Linux, you can compile and run your C/C++ code on it. Most popular applications have already been adapted to the ARM architecture and can be run readily on Pi. Unlike some other SBCs, Pi allows easy access to GPIO ports which makes it equally attractive for people who are interested in hardware. Continue reading ‘Adding a Barrel Jack And a Switch to Raspberry Pi’ »

It is well understood that resistors are typically binned in such a way that for a given tolerance the actual resistance values are distributed within the specified tolerance but are outside the range of the next tighter tolerance specification. So for instance, when you buy a bunch of 5% 100K resistor, you can expect the values to be between 95K and 99K or between 101K and 105K. Values between 99K and 101K will be missing as they are binned as 1% resistors. Continue reading ‘100K 5% Carbon Film Resistor Value Distribution’ »

I have been mainly using perf-boards for my electronics projects. Since most of the stuff I build are not very complicated and are one-offs, using perf-boards has been more than adequate. With that said, I did find wiring the headers in my Arduino projects to be a big pain and depending on the number of break-out pins needed to be wired this could be quite time consuming and error-prone as well. Since I have heard many good things about Seeed Studio‘s Fusion PCB Service, I decided to give it a try. Continue reading ‘Arduino Dev PCB Using Seeed Fusion PCB Service’ »