Samsung Galaxy S-Pen Waveform Capture

I was quite intrigued by the S-Pen that came with my Samsung Galaxy Note 4. According to the specifications listed on Samsung’s site, the S-Pen supplied with Samsung Galaxy Note 4 he S-Pen supports 11 bits (2048 levels) of pressure levels and can be detected at a 15 mm hovering distance from the phone surface.
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Keithley 614 Electrometer Teardown

In this blog post, we will take a look inside a 1980 vintage Keithley 614 Electrometer. While it was designed and built more than three decades ago, its performance is still pretty impressive (10 fA current resolution) even compared with today’s modern standards. Its performance was only rivaled by Keithley 617 in its days.
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Turn Your Android Phone into a Wireless Touchpad

In this blog post, I will show you a simple way of turning your Android phone into a wireless touchpad. For this to work all you need is your Android phone, an Arduino board and a HC-06 (or HC-05) bluetooth module based on BC417. A short demonstration video is included towards the end of the post.
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Reverse Engineering a Beseler PM2L Color Analyzer

I recently acquired an old Beseler PM2L color analyzer. This kind of color analyzer was designed to analyze the color or exposure of film negatives at a certain location by comparing the intensity of the filtered light of each color channel (CMY and white). The PM2L model was made in the 70’s through early 80’s and has long become obsolete. But since it has a 931A photomultiplier tube (PMT) inside, you can easily repurpose it for other uses. And the good news is, these old color analyzers are cheap on eBay. You can usually grab one for a price cheaper than a bare PMT itself.
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Wavetek 1045 RF Power Meter Teardown

I bought a Wavetek 1045 RF power meter off eBay a few weeks ago. It came with a 13787 detector which is capable of measuring RF power between -50 dBm to 10 dBm with a frequency range of 1 MHz to 18 GHz.
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How to Drive a Latching Relay

Latching relay (a.k.a. impulse relay) can be turned on and off by momentarily applying a voltage across the relay coil. The relay would maintain in its last switched state without the need to maintain the coil current. In this post, I will show a simple circuit which can be used to drive such relays. In the video towards the end, I also included more explanations and some demonstrations.
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T is for TWT

Traveling-wave tube (TWT) is mainly used to amplify signals in the microwave frequency range. Unlike most vacuum tubes, which had largely given way to their more elegant semiconductor counterparts many decades ago, TWT is still being widely used today in many areas, especially in places where low noise and high output power is needed. I had always wanted to get my hands on one so when I saw an old HP 493A microwave amplifier for sale for peanuts, I simply could not resist snatching it.
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Visualizing Comparator and Op Amp Hysteresis

Hysteresis can be added to a comparator circuit to improve its stability, especially when the input signal is noisy. In this post, we will examine the hysteresis characteristics of some common comparator and Op Amps using an oscilloscope.
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Testing an RTL-SDR Spectrum Analyzer

Using software defined radio such as the popular RTL-SDR (1, 2) as a spectrum analyzer is nothing new (examples can be found on HackADay and EDN). In this blog post, we will discuss some of the do’s and don’ts when using SDR as a spectrum analyzer and look at some measurements I took using the popular NooElec SDR based on Realtek‘s RTL2832U DVB-T demodulator chip and Rafael Micro‘s R820T tuner chip.
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Keithley 197 Battery Option Build

I have been quite happy with my fixed-up Keithley 197 5 ½ digit bench meter purchased from eBay (you can find the teardown pictures here) earlier this year. Keithley 197 has a battery pack option (Model 1978), and this option allows it to run on battery power for 5 hours without having to plug into the mains. While it is far from being a truly portable meter, its performance easily surpasses most hand-held multimeters. So I decided to build the battery option myself and hopefully I would be able to use the meter more often in places where power outlets are not available.
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Using Arduino Due’s True Random Number Generator

Arduino Due uses an Atmel SAM3X8E ARM Cortex-M3 CPU, which has a native hardware based True Random Number Generator (TRNG). In this post, we will take a brief look at how to use it in the Arduino environment and take a look at some of its statistical characteristics.
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Building And Characterizing A DIY RF Power Sensor

Ever since I got my HP 436A power meter, I have been looking around hoping that I could obtain a compatible power sensor (e.g. 8484A) at a reasonable price to go with it. But these power sensors are quite expensive on the second-hand markets and even a non-functional unit can cost more than a hundred dollars. Since like most hobbyists, my requirements for a power sensor is not that high, I decided to build a simple RF power detector myself.
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On Arduino Due PWM Frequency

I just got myself a couple of Arduino Due boards. While they were released almost two years ago, I have not really got a chance to look at these until quite recently. Arduino Due is based on Atmel’s ATSAM3x8E 32-bit ARM Cortext-M3 processor. The processor core runs at 84 MHz, which is significantly faster than its 8-bit AVR counterpart ATmega328p which runs at 16 MHz. For an ATmega328p, the highest achievable PWM frequency is 8Mhz (square wave), so we should be able to generate much higher frequency signals on an Arduino Due. But how high can we go? Let’s find out.
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HP 8642B Teardown Pictures

In my last post, I showed my LED backlight mod of the HP 8642B synthesized signal generator. And during the process, I also showed some pictures of the A1 (keyboard and LCD) module and A2 (modulator) module alone with an intriguing Easter egg message in the firmware. In today’s post, I will do a full teardown of each module and take a closer look at what’s inside.
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HP 8642B Backlight Mod

If you take a look at the picture below, you may recognize immediately that it is a picture of an HP 8642B synthesized signal generator. But if you take a closer look, you probably will notice something different if you have ever used an HP 8642B before.
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