I’ve been holding onto some trinkets from a work event some time ago, in anticipation of finding a proper use for them. The other day I decided the most befitting use would be to incorporate them into an award to be passed around the team at work recognizing the individual who is most deserving that week.
I took a bit of 2×4 wood, sanded and stained it, mounted the trinkets to it, and stamped a brass plaque on the front.
I think the newly created Lotus Appreciation Award came out pretty well.
I’ve had an older HP 10544A ovenized crystal oscillator laying around for some time now, waiting for a good project to be put to use. It’s a high precision frequency source that fell out of spec and was pulled from other test equipment.
The first question if I was going to re-use this part, is why it fell out of spec to begin with. These crystals are inside an insulated case with a heater that keeps the crystal at a constant, hot temperature. The problem could lie with the crystal itself, the circuitry supporting the crystal, or with the oven maintaining a stable temperature for the crystal. In this case, hooking it up, and doing some quick measurements showed that the oven wasn’t turning on properly, and if the crystal never gets warm, it will never be at the specified frequency.
After opening it up and doing some digging around, it became clear that the thermistor, which measures the temperature to control the heater, had gone bad, and always read that the oven was very hot, so the heater would never turn on.
After replacing the thermistor, the heater started working again as expected, so I was ready to use the crystal as the oscillator for a homebrew GPSDO.
A GPSDO or GPS Disciplined Oscillator, is a combination of a local oscillator like this crystal, and a high quality GPS receiver, which allows you to combine the best timekeeping aspects of both. The crystal will be very stable over the short term, but over longer time periods may drift, whereas the GPS may hunt around a bit in the short term, but over the long term, GPS is incredibly accurate, as it’s sourced by atomic clocks on the ground and on the satellites. Combining the two lets you take the short term stability of the crystal, and use the long term stability of the GPS to “push” the crystal to stay on target and avoid the drift.
I set to work gathering together the components I’d need to build the overall device, a power supply, the GPS, the Crystal, and a processor to measure the crystal and GPS, then adjust accordingly.
I used an Arduino Due to handle all the measurement and processing, as it has some very fast, and capable timing functions, and packaged everything up into an aluminum box I grabbed from the local electronics hobby store and painted.
I’m still working on the code, and doing some final tweaks to the hardware to get everything just the way I want it to be, but now it’s just a matter of *time* till it’s done.
As mentioned in my last post, I’ve been working on building a small HF amplifier. I’d like to use it to build a standalone WSPR station that can run on its own, and transmit with a couple hundred milliwatts.
I don’t have the transmit portion completed, though I do have the code to run it done, so I don’t have a working model yet, however I did get some time to get the amplifier put together. It’s capable of about 250mW output, with 10mW input without generating too much heat.
I designed the board to be able to accommodate up to four transistors in parallel, so with more heatsinking, I could use the same board on a higher output power model.
I’ve recently been working on a small HF amplifier project, using common TO-92 style transistors. I needed some heatsinking capability to keep the transistors at a reasonable temperature, so I whipped a couple small aluminum heatsinks up on the lathe.
They’re really simple, starting with some ~1/2″ round bar, drilled out the middle, parted off the section, then drilled and tapped the set screw hole.
They’ve got a really good loose contact fit with a TO-92, and a little bit of thermal paste goes a long way in making them as effective as possible.
I’ve recently been playing with the Electric Imp platform of Internet of Things devices. They’re fairly inexpensive, and very easy to use, so when SparkFun recently was having a sale, I picked up their Weather Shield, and Sensors.
With some slight modifications for power savings, and hooking up the Arduino shield pins to the appropriate pins on the Electric Imp, then it came down to coding it up so the Imp would sleep for five minutes, wake up, take a reading, connects to the wifi and send the data to my logging server, then sleep again.
I packaged the whole thing up in a mason jar for weatherproofing.
The power source is a lithium primary battery, which should last a number of years with the low power consumption the Imp uses while sleeping.
My logging server collects all the data, and generates graphs for easy consumption.
