The usual drill… A problem that can be solved by a bit of circuitry. In this case the gals in the lab were having trouble controlling the mix of gas to their cultures. They needed to feed much less CO2 to the mix, where the off-the-shelf flow gauges and needle valves became difficult to use much under one liter-per-minute.
Simple solution… Build a gas modulator, something that could turn on the gas some percent of the time, allowing easy control of small amounts of CO2 to the mix. A timer and a gas solenoid… Easy.
There is nothing particularly interesting about the circuitry. A seven segment display, a few switches, and a power transistor to control an external solenoid. All very basic. It is the controller that is new, at least for me. An Arduino provides the programmable part of this project.
Living with active volcanoes about is made a bit easier if they are properly monitored. The entire island of Hawai‘i is liberally equipped with sensors of various types… Seismographs, tiltmeters, GPS stations, cameras, and gas monitors.
I came across one of these last instruments on a recent visit to Hawai‘i Volcanoes National Park, the new Kahuku Unit at the south end of the island. While walking in the gorgeous natural scenery of the park, this engineer was instantly attracted to a spindly frame of tubes standing in an old corral.
The Kahuku Cross Fence station is part of the NPS maintained Hawaii SO2 Network with stations throughout the park. The data is provided to rangers and posted on the park website to advise visitors of volcanic gas hazards while visiting the volcanoes.
Some equipment around the observatory is thirty or more years old. As you would expect, keeping it running can be a challenge.
There are two ways of dealing with this old equipment… Replacing it with something new is the preferred way. When it becomes difficult to locate spare parts, when it breaks down too often, just replace it with new gear. For much of the equipment this is the usual answer and is often a major part of the job.
Some equipment is not so easily replaced. When replacement would require wholesale redesign of a system it becomes more of a challenge. Sometimes the only choice is to keep that old gear running.
This is the case with our servo amplifiers. Twelve amplifiers supply the power that drives the telescope, one amplifier for each motor. Eight amplifiers and motors drive azimuth, four drive elevation. Three hundred and seventy tons moved by twelve relatively small DC motors. While much of the telescope control system was recently replaced, it was decided to keep the old servo amplifiers.
You might notice that these servo amplifiers are just a wee bit critical.
There is always something broken. It is just a rule on boats. Usually is is more than one thing, you have a list. Just so long as nothing on the list is truly critical.
Our journey south along the Inside Passage has been documented by adding things to the list, and crossing a few off as they get fixed. Washdown pump not working? Bad crimp in the power connection. The defrost vents on the bridge… Fixed. The anchor light atop the mast? Fixed… That took some work and dismantling half the ceiling. Door latch on a galley cabinet… Fixed.
Still, the list does not seem to get any shorter.
Nothing really critical… Until we noticed the batteries were not charging.
Hmmm… That might be a problem.
I spend a few minutes poking about in the engine room. The battery circuits are fairly simple, everything is just bolted to the forward bulkhead and fairly easy to get at. There is some complication in that we also have a battery charger that runs off AC power, that adds a few more wires, circuit breakers, and other electrical boxes to the setup.
Yeah… The alternator is dead. It is putting out 2.9 volts, not 12 to 13 volts..
Hmmm… That is a problem.
Fortunately we can charge our batteries. We have to run the generator and use the battery charger. We can keep cruising, with no redundancy. Lose the gen-set or the battery charger and we will soon be dead in the water when the batteries give out.
Of course this happens in the middle of a rather large bit of wilderness, a long ways from any substantial port that would have the needed parts.
So we run the gen-set for a few hours each morning, and a few hours each evening charging the batteries. The nights are punctuated by getting up to check the battery voltages, on the panel just outside my cabin door.
Those few days of cruising allow us to get to Shearwater. This little port serves the cruisers coming up from Vancouver and transiting the Inside Passage. Shearwater offers a fairly good marine supply house and a small boatyard.
Of course they do not have an alternator for a Cummins diesel in stock. They can however fly one in the next day from Vancouver. Just $400 for the alternator and another $90 to have it couriered to the airport. The final bill is $515… Ouch. Only somewhat softened by the conversion rate to $US.
We spend the night in a very pretty little cove a few miles from Shearwater. In no hurry to run back to dock I take a couple hours to kayak around a saltwater lagoon playing tag with a family of otters. One nice result of the breakdown.
At 1:30pm the water taxi arrives from Bella-Bella with our alternator aboard. Good, this will take 20 minutes… Not.
A broken 1/2″ ratchet… Run up to the marine supply for a 1/2″ breaker bar. $20 later we can get the serpentine belt off.
We do not have a socket big enough to get the pulley off the old alternator. Run up to the boatyard where the mechanic quickly swaps the pulleys with an air ratchet. We slide him enough loonies for a round of beer.
Done. The batteries are now charging! We head south towards Queen Charlotte and a open ocean crossing with all systems good to go. Everything critical at least.
The ongoing collapse of the summit caldera on Kilauea has been generating a daily five point something earthquake. While not powerful enough to damage the facility, these events do show up in the data each night, bumping the telescope, disturbing the tracking, and occasionally ruining an exposure.
This phone call had a number I knew all too well, even without the caller ID showing the name… K1 Remote Operations. A this time of night it would be a problem, a serious problem. This particular problem would have me on the road back to the summit an hour later.
Midnight runs to the summit are not common, but they do occur in my life. Usually we can work remotely, the night attendant serving as our remote eyes and hands. Just press the right button, flip the correct switch, done. Not this time. We tried, for over an hour we tried.
I really did not want to head back up. I had just gotten down a few hours ago, having spent the day on the summit working on the usual long list of things that need to get done. Days on the summit, in the thin air of nearly 14,000ft elevation are physically draining.
The irony of this malfunction is that I had seen it before. The dome had tripped out inexplicably on previous occasions. The problem would occur then disappear. Once it vanished you could not troubleshoot it. Unlike most of our other systems there are no logs from the shutter drive, nothing records what was going wrong.
The Friday before this it had happened to me again. But this time was different, I had a maintenance computer attached to the PLC serial port. This time I saw the error, something in the code labeled speed mismatch. No idea what this was, or how it worked. Again the error disappeared, and I could not troubleshoot further as the weather was getting worse. No opening the shutters again.
I needed a chance to figure out what this fault was… Later that day I read through the code, figured out this feature was a speed check to insure that both sides of the shutter are driven evenly. A check to compare the right and left sides of the shutter and to fault if the difference is too large. Two words of memory were compared, if the difference was too large it faulted the shutter drive.
The Keck domes can be controlled three ways… From a set of manual controls on a panel at the base of the dome, via computer control when observing, and from a radio controller that you can use from anyplace in the dome. This radio controller has long been called Capt. Marvel around Keck, the original versions looked like a prop from a 1930’s sci-fi serial movie.
The radio controller is actually a crane controller, a standard unit you can buy that can safely control large machinery, including enormous factory or dockyard cranes. Being a standard unit it has a number of safety and security features built-in… Fail-safe operation, coded communications, and more insure reliable operation.
The unit is standard, the panel is custom. When buying the transmitter you need to specify the front panel layout including the switches and labels for your application. Thus our transmitter has a panel arranged to our specification with switches for dome rotation and opening the shutters. In the middle is a bright red-emergency stop switch to insure you can immediately stop everything if something goes wrong.
Another little problem around the house that can use a little creative circuitry to make it better. Do I really have to do it? No. I do it because I can, and because it is fun!
This time it is the electric back up heater for my solar hot water heater.
In Waikoloa solar hot water is an obvious addition to the house, we had it installed within a couple months of moving in. Considering electric power is about $0.40/kWh on the island, and tropical sunlight is quite intense, the use of solar to heat our water has been good money saving move… Long, hot showers with no guilt!
Once or twice a year we will get a period of heavy clouds and the water temperatures will fall to the point we need to turn on the electric back-up heating element in order to have that hot shower. Like most solar setups the storage tank has a electric element that will heat the water when needed.
With the Keck Observatory open house approaching I am helping get one of the most popular activities ready. At the last two open houses we have made flasher pins, we will do so again this year.
Flashers? These are a simple circuit built on a PCB that flashes a pair of LED’s. Nothing serious, just a bit of electronics fun. The activity allows folks to learn a little electronics and soldering.
The PCB is configured as a pin or badge, with a brooch pin soldered to the back that also serves as a switch to turn on the LED’s.
The original design came from John Maute at SAO. The circuit is based around the venerable LM555 timer IC configured as an astable multivibrator. The LM555 timing circuit is simple enough to solder together in a few minutes, complex enough to look cool and provide a real introduction to an electronic circuit.