I have been spending way too much time playing with the new 3D printer, so have to get back to some electronics. Since the next CWTD.ORG episode is coming up, I decided to build another ‘Test Gadget’. This time it is a Signal Generator based on the SI5351 clock generator. I had purchased a couple Chinese versions of the Adafruit 5351 module when I was working on the ‘Sweeperino Jr. ‘ and wanted to see how well they worked.
The picture shows the completed DCVM test gadget in 4 channel mode measuring the 3 voltages present on the headers used to connect the individual test gadgets. I was running this off of the PC without the 12 volts connected for external power, so I kept the range down to 5 volts.
I have been following a series of podcasts from ‘Chatting with the Designers’ CWTD.ORG that cover building simple Arduino based test equipment. I decided that this would make a nice way to get into development with the ESP32. The CWTD ‘Test Gadget’ is basically an Arduino Nano with a 2 line LCD display, and a breadboard area where small modules can be plugged in to make different types of instruments. My version will use the ESP32 and the TFT display. I am also replacing their rotary encoder with a joystick for the user interface device. I am bringing all the pins from the ESP32 module out to two pairs of female headers, that should allow me to plug in two small modules at the same time.
Testing the TPS61092 boost converter from LuckyResistor:
For my current project I searched for a good boost power converter which is able to deliver continuous 400mA power for various sensors.
There are an endless number of good boost converters around, but not many can be hand soldered to a board. I would really like to see some like the TPS61092 with SOIC or similar packages. The biggest problem seems to be the heat transport, why most chips have to be mounted flat on the board.
Before using the chip in my project, I created a small test board. Using this board I can test various things. First I liked to test the performance under load. Next I tested if the chip can be hand soldered and finally I tested the final board layout I will use in my project.
Finding 3-phase is difficult, convincing the owner of the said supply to test some home made hardware is even more so. After building a 3-phase energy monitor my testing options for it appeared very limited. So I set about making my own low-cost 3-phase energy monitor calibration system.
Inspired by an old article from sparkfun and some tests I conducted myself I came up with a PCB that holds the pogopinholders and an lasercut acrylic fixture for the PCB on top. Using the dirt(y)cheap services from dirtypcbs.com the cost for this jig, including pogopins and their holders is about 45 USD. As an advantage you receive 5 lasercut acrylic and 10 PCBS which allows you to make 3-4 jigs in total!
To design the PCB that holds the pogopins I started with a 10×10 PCB with M3 mounting holes and imported the to be programmed PCB (File, Import, Eagle drawing) and place this in the centre (not mandatory, but looks prettier).
Here’s a test rig for the ADB-USB Wombat board: my first-ever project whose sole purpose is to facilitate testing of another project. It uses spring-loaded pogo pins to create a bed of nails that fit into test points on the Wombat board. I can drop a new Wombat board onto the tester, clamp it in, and then program and test it with just a few button clicks. This is a huge improvement over my old manual testing method, which involved multiple cable connections and disconnections, and hand-verified keyboard/mouse emulation on two separate computers. That sort of test process is fine for building a few units, but something faster and easier is needed to support higher volume assembly.
Pogo pins contain tiny internal springs. When a Wombat board is pushed down onto the bed of pins, they compress a few millimeters in length. This helps to create a reliable electrical contact for each pin, even if the uncompressed lengths of the pogo pins are slightly different or they’re not perfectly aligned.
When I was in China last year I sourced a couple of small E-ink displays (GDEH0124S01) through Taobao. They were simple ones with 8 14 segment characters. After some searching on the Chinese website from the manufacturer I found the datasheet. It was by all means not complete and a lot info was missing. After a bit more searching I found the controller used is DM130120 and its datasheet tells a bit more…
I made a PCB quite some time ago, but due to personal matters, I hadn’t the time to solder them up and write some code for it. A couple of days ago I soldered the PCB and fired up the compiler. After struggling through both of the chinglish manuals I converted their pseudo code into something the compiler and the micro understands.
Today came in a new batch of PCBs from DirtyPCB.com, of which one is a new revision of the BlackMagicProbe. This revision is almost the same except it has a polyfuse in its powersupply to the target, a dedicated voltage regulator instead of P-FET, its programming header on the 90 degree on the side and a jumper for entering DFU mode. All this goodness is contained in less 5×2 cm PCB space, so quite a bit of PCB estate is left for other purposes and I used panelizing in EAGLE to try another brainfart of mine.
In most DIY projects where pogo pins are used people solder them directly to a wire or pad on a PCB. Despite it looks like it is the way to go, it isn’t. Pogo pins tend to wear out relative quickly as they are only rated for a couple of hundred ‘compressions’, also solder can sip into the pin and ruin its spring.
If you need to test rockets, missiles, or ejection-seat systems, your first instinct would be to shoot them up in the air and see what happens. But if you want data, film footage, or the ability to simply walk away from a test, you might consider running your experiment on a rocket sled.
The Holloman High Speed Test Track is a 15 km long stretch of meticulously straight railroad track located in the middle of the New Mexico desert, and bristling with measurement equipment. Today’s Retrotechtacular video (embedded below) gives you the guided tour. And by the way, the elderly colonel who narrates? He doesn’t just run the joint — he was one of the human test subjects put on a rocket sled to test the effects of high acceleration on humans. You can see him survive a run around 1:00 in.
The video isn’t all that long, but it’s slow-paced. High points include the water braking system in the first few minutes. The “momentum exchange technique” is secret code for filling the space between the tracks with water and ramming a scoop into it, throwing water forwards and thus slowing the sled down.
At 10:40, there’s an almost bizarre transition to dream-like slow motion sequences of various rockets making their runs. Great stuff. In between, there’s a lot of detail about the multiple cameras, light-break sensors, and other instrumentation that was state of the art in the 1960s.
Holloman is still in use today, as far as we know, which makes this Retrotechtacular a bit more contemporary than usual. The fastest run took place in 2003 at Mach 8.6. Not bad for some strips of metal dating back to 1949.