Electronics

If you are on the lookout for a sub $30 Multimeter (or $15 on eBay) for working with low voltages, the best one right now in my opinion is the cute and tiny Aneng AN8008 TrueRMS Multimeter or the newer model, the Aneng AN8009 with NCV and temperature measurement. They have a lot of functions and can measure µA current, and both are a 9999-count meter. The continuity tester is reasonably fast, but there is one little problem that bothered me. It takes 5 to 10 seconds for it to settle on a correct voltage reading. When it finally ends, it’s spot on, but the waiting is annoying. But fortunately, there is a simple fix for this problem. ...

Easy Way To Calibrate a Bryman BM869s Multimeter After replacing my lost Fluke 87V multimeter with a new Brymen BM869s (rebranded Greenlee in the US) about a year ago, I’ve been delighted with the multimeter. It has every possible function I could ask for and then some. It’s been my go-to meter when working on electronics projects. I do have a Siglent SDM3055 DMM that is very good, but due to its startup time, I usually reach for my Brymen BM869s when I need to measure something, and it has higher resolution. But after getting a broken HP/Agilent 34401A DMM from eBay, fixing it up and replacing all the capacitors, I now have a better reference. I’ve compared it to my friend’s calibrated 6 ½-digit multimeter, and it’s still within spec, so naturally, I want my Brymen to be as close to my HP 34401A as possible. Turns out that calibrating and adjusting the Brymen is quite easy. Here’s how to do it. ...

When you make your own NTP server, you probably spend a lot of time trying to get it as accurate and stable as possible. To get good results, you need to connect your server to a good time reference, like an atomic clock, GPS or a GPSDO to get the PPS (Pulse Per Second) to sync your server with the reference clock. In both Linux and BSD, there is kernel support to slave the very inaccurate CPU clock crystal to the PPS signal, continually adjusting the frequency, because the crystals of computers continuously drift due to temperature and barometric pressure differences. So most of the work is to get a crappy crystal to behave. What if you just jumped over that step, so the CPU clock gets synchronized with the same lab reference that the PPS signal uses, using a SI5351C Clock Generator? Read on to see a simple way of doing it and get an extremely accurate NTP server for under $200. ...

So you need to replace the soldering iron on your Atten 8502D Soldering Station. You could just buy the heating element, but you can find a complete soldering iron with cable for less than $12 on eBay. So It’s easier just to replace the whole thing. It Doesn’t Work! I have ordered replacement irons before (I’m very rough with my soldering station) just to find out that they don’t work. You get the dreaded S-E or H-E message on display and, obviously, something is wrong. What do you do now? Read on to find out. ...

How to add an I2C interface to a Sonoff WiFi Smart Switch. The Sonoff brand is a whole series os IOT devices that use the esp8266 WiFi processor internally. The devices are easily hacked and are cheap. The Sonoff WiFi Smart Switch is the most straightforward device, which can turn on or off 110/220 Volt 10 Ampere remotely. That means you can have your ceiling fan, lamp or anything else connected t mains power remotely controlled by your phone or computer. But the software that comes with it isn’t very flexible and cannot be integrated into a home control system like NodeRED, OpenHAB or any other home automation system. Firmware The Sonoff devices are easy to hack, so you can put a better firmware like ESPEasy on it and integrate the device with any system. ESPEasy has an extensive list of extra modules that you can connect, like temperature, barometric pressure, humidity, light sensors, PIR sensors and a long list of other things. But most modules connect with I2C, which is a serial interface for interconnecting ICs using a clock and a data line. The Sonoff Switch only have one extra pin available, making it impossible to connect more advanced sensors. But there is a way of fixing that. Here’s how to add that to add an I2C connector to your $5 Sonoff and open up a whole field of stuff you can do. ...

What kind of impedance does this coax cable have? Sometimes you dig around in your parts bin, desperately searching for a bit of coax cable to make a new connector to your fantastic whizzbang widget. If you find a piece of cable without markings, how do you know if it’s 75Ω, 50Ω or some other impedance? Well, here are two easy ways of finding out. ...

A friend of mine bought a new amplifier, but he wasn’t pleased with the sound. So he called me and asked if I could recommend a good old amplifier that could drive smaller speakers because he likes the aesthetic of older things. And the venerable NAD 3020B was the first one that came to mind. When I was young, this was the first affordable amplifier that sounded good. It’s not a powerhouse by any means, putting out (a very conservative estimate) 2 x 20 watts. But the phono stage accepts both MM and MC pickups which is excellent, and the sound quality is exceptional. So he scoured the used market and finally found a NAD 3020B. Unfortunately, when he got it home, there was a loud hum from the output. So I told him to send it to me so I could fix it. ...

[caption id=“attachment_4974” align=“alignright” width=“400”] Raspberry Pi 3 Overclocking Case Enclosure[/caption] The results are in: I’ve been very busy with different projects, and one of them requires a custom enclosure. So I thought it would be an excellent excuse to learn Fusion 360. When the Raspberry Pi 3 came out, I did some overclocking experiments. But I settled with just passive cooling with some small aluminum heatsinks. But after seeing some tests done with a more massive copper heatsink combined with a cooling fan, I decided that I wanted to build a case with a silent fan with enough room for a large heatsink. I need it for my NTP server at ntp.jacken.se to get better performance. ...

I wanted to get a distribution amplifier for my 10 MHz lab reference signal from my GPSDO to feed my equipment, like my timer/frequency counter, signal generator, and other stuff. I also needed a way to distribute a 1 PPS signal from my Trimble GPSDO to my NTP servers and other clocks and monitoring systems. The Trimble only got two 10 MHz outputs and one 1 PPS signal output, so I needed to add more, especially for experimentation. I saw this video by Gerry Sweeney where he modifies an Extron 300MX video distributions amplifier, adding a rubidium reference standard and was intrigued. But I changed the modifications to fit my needs and here is the result. ...

Upgrading a Philips-Fluke PM6665 Frequency Counter with an Oven Controlled Crystal Oscillator - Up and Running! I needed a frequency counter for my little lab at home. Naturally, I wanted an HP Agilent 53132A or similar, but it’s way too expensive for my modest use. So I browsed around eBay and found an old Philips-Fluke PM6665 frequency counter with the optional 1.3GHz add-on board. With a 10 second gate time, I can get down to 0.1 Hz at 10 MHz, so that’s more than I need. It didn’t have the option of a better crystal, unfortunately. When I tested the PM6665 against my Trimble 10 MHz GPSDO reference, the unit was off by 200.1 Hz. Without a calibration sticker on the instrument, I’d say that’s pretty good for a device manufactured in the late 80s. I tried to trim it, but it uses an adjustable capacitor, and you only needed to look at it for it to change settings. ...