Electronics-2

I haven’t had time to update the blog because I’ve been busy designing a new headphone amplifier. There’s been a lot of development when it comes to operational amplifiers and I was curious about how well I can get an amplifier to measure using the latest technology. The op amp I’m using still hasn’t got a development board, so I make one myself. The op amps are 5x5mm in PVQFN-20, so you need to use an SMD soldering gun or oven to be able to solder them. I simulated the circuit with both LTSpice and TINA90, but left biasing resistors and some other stuff in good old fashion though-hole components for easy testing. ...

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. ...

Speeding up your SPI MAX7219 LED displays when using Arduino and LedControl Library In preparation for the arrival of my GPSDO[1], I’m doing a quick build of an “Atomic Clock” display to have above my lab equipment. I’m using a cheap, small eight digit red LED SPI-controlled display. It uses the MAX7219 controller that I got from eBay for next to nothing. I plan to parse the RS232 information from the GPSDO unit and display the exact time. I’ll also post error messages if the GPS signal lock gets lost. I’ve done a quick prototype using an Arduino Uno, but I plan to try to get an Attiny85 to work as the controller when I’ve finished the parser and the rest of the software. After doing some research, naturally, there was a library available to connect to my LED display called LedControl. It’s part of the standard Arduino libraries (in the download section). But when I checked the code, it uses the Arduino routines to shift out the SPI data to the display. It’s great if you want to be able to use any pins to connect to the screen, but using Arduino’s bit manipulation tools for “bit-banging” the display is slow. ...

I’ve finished the OCXO upgrade. Read about it here While browsing on eBay for my new lab at home (I’m getting into electronics again), I came across a Philips PM6665 Frequency Counter, an old but functional unit so I couldn’t resist, I had to buy it. So I downloaded the Users Manual and Service Manual for the frequency counter and started to check the schematic. As usual the unit, when new, could be bought with several options. One of them was a better crystal oscillator, an MTCXO that can be automatically calibrated using a 10 MHz external reference, giving an accuracy of 3*10-8 but my unit doesn’t have that option, unfortunately. This will be fixed though. But it does have a 70 MHz to 1.3 GHz optional input! So here’s what I plan to do… ...

I got myself a four channel 50MHz oscilloscope to be able to do some measurements. The Rigol DS1054Z. It’s expensive in Sweden if you buy it from a local retailer, but I ordered mine from Batronix in Germany and thanks to being part of the EU, there’s no customs and extra taxes added to the price. The oscilloscope is easily hacked to 100MHz and a lot of other functions like serial protocol decoding and also more memory depth. RS232/UART, I2C and SPI decoding, advanced trigger functions like RS232/UART, I2C, SPI, Runt, Windows, Nth edge, Delay and Timeout trigger. Search for “Rigol DS1054Z hack,” and you’re on your way to transform your scope to a much more expensive version. But don’t enable the 500µV option. The oscilloscope doesn’t support it in hardware, so you will run into bugs if enabled. I’ve been delighted with my purchase, except for the occasional bug. But today it went into a total haywire mode. When trying to start it up, it hangs on boot. Either by just showing the Rigol boot screen, or show the standard display but remain immune to any input from the controls. Panic! But thankfully I found a solution to my problem. ...

“Mapping WiFi Signals in 3 Dimensions” 3D wifi plot image Adam Fabio, Hackaday: [Charles] is on a quest to complete ever more jaw-dropping hacks with the popular low-cost ESP8266 WiFi modules. This week’s project is plotting WiFi received signal strength in 3D space. While the ESP8266 is capable of providing a Received Signal Strength Indication (RSSI), [Charles] didn’t directly use it. He wrote a simple C program on his laptop to ping the ESP8266 at around 500Hz. The laptop would then translate the RSSI from the ping replies to a color value, which it would then send to the ESP8266. Since the ESP8266 was running [Charles’] custom firmware (as seen in his WiFi cup project), it could directly display the color on a WS2812 RGB LED. A great hack. It’s amazing to actually be able to see the reception of the Wi-Fi signal mapped as a 3D object. Shows that just moving a router/receiver a small amount can have an impact on reception. ...

Adafruit TRINKET – Mini Microcontroller – 3.3V and 5.5V versions: It’s a tiny microcontroller board, built around the Atmel ATtiny85, a little chip with a lot of power. A cool cheap little Arduino compatible board for smaller projects. The 3.3V version runs at 8MHz and the 5V version can run at 8 or 16MHz. It has five I/O pins available and comes with 8kb of memory. It can be programmed with AVRDude or the Arduino IDE after some small modifications. Looks great!

Crystal cMoy Freeform Headphone Amp: Very cool transparent cMoy headphone amplifier, made using clear casting resin. This is something I have to try. Via 0pachira

My twelve year old son want’s to learn how to program. My first idea was to teach him Ruby or Python, but I decided to go with Arduino. It’s C-based so that’s a good start I think. Were currently planning a couple of projects but so far he’s managed to get some LED’s blinking. A good start.