Kerry D. Wong

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.
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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.
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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.
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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.
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I bought a Sony A6000 mirrorless digital camera last year to replace my Cannon PowerShot Elph 300 HS point and shoot camera for my YouTube videos. While its fast auto focusing capabilities is great for my teardown and project videos, the A6000 also has some drawbacks. Namely, you cannot shoot video while the camera is hooked to the charger or computer via the USB port. And because of this limitation, continuous shooting could be a challenge as the battery would be depleted rather quickly.
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A flat bed scanner typically uses three rows of CCD sensors (RGB) to capture images placed directly on top of the glass bed. When the CCD array scans from one end of the image to the other, the digitized color image is formed. So with a similar approach, we could use just one photosensitive device to capture the entire image one pixel at a time via raster scanning. Now that I have an HP 7044A X-Y recorder I could use it’s X/Y servo mechanism with a suitable sensor to build a single pixel scanner.
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I just bought an ESD mat for my workbench. ESD mat is great when working with sensitive electronics components as it safely dissipates any charge built-up to the ground via its dissipative surface through the attached grounding wire.
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I had wanted to make a spot welder for a while. Most of the DIY spot welders use a momentary switch the primary side of the microwave oven transformer (MOT). Due to the simplicity of this design, it is very simple to make. This design however, has some inherent safety issues as the momentary switch is typically within reaching distance of the operator (unless a foot switch is used) and inadequate insulation could increase electric shock risk. Further more, the current flowing through the primary winding can significantly exceed the current rating of the switch and cause the switch to fail. Due to the inductive nature of the winding, the switch can sometimes arc over and pose significant risk to the operator.
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I recently upgraded my home phone system and thus was left with a couple of old Uniden DCT648-2 handsets. Most of the components inside are probably not salvageable but these handsets use 3×16 character LCDs, so it would be nice if I could reuse them in my other projects.
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I got a Wavetek 395 arbitrary waveform generator (AWG) last year. Unlike my other equipment (such as HP 8566B, HP 5350B, HP 8642B and Racal Dana 1992) which all came with high stability ovenized crystal oscillators, the Wavetek 395 only comes with a 100ppm crystal. While the stock timebase is perfectly fine for all but the most serious measurements, I decided to upgrade it to an oven controlled crystal oscillator (OCXO) as I happen to have a Vectron CO-717B58N lying around.
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I picked up an HP 7044A X-Y recorder on eBay recently. This one was made in the early 1980’s and by today’s technology standard it is rather ancient. And because of this, it is very easy to interface with as the input is completely analog. My plan was to do some experiments down the road using the X-Y movements capability of this HP recorder.
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Till recently, I have been using custom circuitry whenever I needed to backup some firmware. But the process was rather tedious as for each kind of EPROM or EEPROM I needed to study the protocol and timing requirements and then come up with the required circuitry on a breadboard. And wiring can easily become an issue with a high pin-count chip. So I finally got myself a proper EPROM programmer (it’s a TL866A) along with a $15 generic UV EPROM eraser so I could program EPROM/EEPROM’s quickly. While it was fun to build a programmer circuit each time, I think the effort can be put into something more useful.
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I got this broken Beats Solo2 BT wireless headphone from one of my colleagues. In fact, it was broken once before around two years ago and I fixed it for him back then. The issue was because of a broken signal wire due to repeated flexing of the collapsible headphone band. This time around though, I am not going to fix it although I suspect that the cause remains the same. In fact, quite a few of my friends with the same Beats headphones had experienced similar problems. So I wanted to take it apart and take a closer look inside. A video of this teardown can be found towards the end of this post.
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In my previous blog posts, I did a teardown of the Symmetricom/Datum 8040 Rubidium frequency standard and modified the 1PPS output by expanding the pulse width from just around 10µs to roughly 50% duty cycle. There were some questions regarding the clock jitter introduced by the 555 monostable circuit. So let’s take a more detailed look in this post.
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Last time, I did a teardown of the Datum 8040 Rudidium standard. As I discussed, the 8040 has a 1PPS output but the pulse width is very short, at around 20µs. In this blog post, let us take a look at how to extend this 20µs pulse to make the 1PPS output symmetrical. As usual, a video is included towards the end.
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