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Feynman Path Integral Perspectives

YouTube can get eerie at times. Tonight it came up with Feynman’s Infinite Quantum Paths | Space Time and Math vs Physics – Numberphile. Both get into Feynman’s insight into quantum mechanics but one is from the viewpoint of a physicist and the other from the viewpoint of a mathematician.

Of course, there are a lot of lectures on YouTube about path integrals including Feynman’s own. So maybe it isn’t so odd to have two of them, two new ones come up at nearly the same time.

What happens when you open-source a soldering iron

The TS100 soldering iron (Amazon) has been getting a lot of buzz. It’s on github and both software and hardware specifications are open. It runs off 12 to 24 volts DC so a battery pack from a power tool or laptop will run it. A laptop power supply is a common resource for it as well. By all reports, the iron works well. It heats up fast and will hold its heat under heavy load.

Having the source code available and making it easy to upgrade the iron’s firmware is an invitation for some. Elliot Williams on Hacakday reports that there is now Tetris on a soldering iron.

Our commenteers have all said good things about the open-source TS100 soldering iron pencil: things like “it solders well”. But we’ve all got soldering irons that solder well. What possible extra value does having open-source firmware on a soldering iron bring? [Joric] answered that question for us — it can play Tetris. (Video embedded below.)

While that’s cool and all, it wasn’t until we were reading through the README over at GitHub that the funniest part of this hack hit us. Every time you lose a game, the iron tip temperature increases by 10 degrees.

OK. 

The latest firmware version goal was to make it possible to change settings without having to resort to the USB port. I don’t think the games capabilities are being offered as a standard item, though. Firmware upgrades are simply a file transfer to a USB drive. The iron uses a PIC 32 bit microcontroller and an OLED display. It includes an accellerometer so it can tell when it is not in use and automatically go into standby. Price runs around $60.

‘Old’ People v Tech

Linus got himself in a bit of hot water at YouTube with Old People are the WORST at Technology – Then vs. Now Ep3. Yes, he’s poking fun at stereotypes. The likes to dislikes runs at 25k to 4k so there are are a lot who don’t see the point.

The fact is that a real problem is highlighted. A good example of where the problems he illustrates can have a negative impact on organizations is with the WBCCI, an Airstream RV owners group. Those problems run from a failure to adhere to commonly accepted good business practice in communications to a failure to understand the level of financial and professional support needed in an online presence.

It isn’t ignorance that is the underlying issue. It is the resistance to learning and change. That expressed dissonance that is often surfaces in asocial ways. 

As Linus points out, safety and security may be at stake. Falls are a significant hazard for the elderly. One lady even had a kitchen wall phone mounted near the floor after a fall experience where she could not reach a phone. Now the issue is about resistance to having a cell phone and about not carrying it at all times. This can be even a simple flip phone with big buttons but it could also be a smart phone with an app that will detect when a fall and call for help automatically or respond, via Alexa, Sira, or Cortana to a plea for help.

Linus highlights a number of areas between the inane to critical where technology could make life better – if allowed to. From social interactions to mental stimulation, there are many ways that technology can enhance vitality and lifestyle that should cause those who get into arguments with the youngsters in their life should keep in mind.

Soldering tutorials

Hackaday says the key to soldering is to pace yourself. “When writing my last article, I came upon something I thought had been lost to the seven seas of YouTube: the old-school “Basic Soldering Lesson” series from Pace Worldwide.”

Speaking of which, we’ve seen many things designed to educate, but one size certainly does not fit all. Do y’all know of any well-made sources that teach foundational topics that are as accessible as this series? If so, let us know in the comments.

there’s some good stuff out there if you can find it.

Nostalgia – a learning motivation?

Retro Radio: W8CDX Takes Field Day Back to its Roots – “Some younger radio amateurs may not realize that ARRL Field Day has been a staple operating event for more than 80 years.”

“We had a lot of fun putting up another 1930s-style station for Field Day 2017,” said Eric Tichansky, NO3M, the trustee of W8CDX, the Karns City Amateur Radio Club station. The transmitter was based on an August 1934 QST article, “A Medium-Powered Phone-C.W. Transmitter with Pentode Power Tubes,” the receiver on a May 1934 QST article, “A De Luxe Crystal Type S.S. Receiver.” Tichansky has documented the receiver project from start to finish.

Just recently helped a neighbor put together a RetroPie and learned a bit about the current state of emulation for some of the computing machines of the 80’s. Now, it’s about radios with vacuum tubes and homebrew nearly everything in the station.  

Then there’s Mr Carlson’s Lab on YouTube. His latest teardown and refurb effort was a ca 1940 device to switch between two inputs so as to to provide dual channel capability to a single input oscilloscope. He reverse engineered the circuit and explained some of the peculiarities of the circuit and the components in the switch. The switch and an old Heathkit oscilloscope are part of the ‘retro bench’ he’s putting together to show how radio repair used to be back in the ‘good old days.’

Dave Jones hosts Shahriar Shahramian and the discussion is something else.

It’s a geekfest. Shahriar Shahramian from The Signal Path met up with Dave Jones of EEVblog and discussion is well worth some time. It’s broken up into three videos each with their own focus.

1. Youtube & Bell Labs

2. Science, Debunking & Education

3. about the millimeter wave electronics and 5th generation RF

These two are been there, done that communications and electronics engineers who have created successful YouTube channels that provide a no holds barred education to improve technical and scientific literacy. 

CI-V simplified by modern tech for Icom radio control

There’s a simple eighth inch jack on the back of most Icom radios that provides a communication interface for control purposes. If you look around for how to tie this into a computer, most of what you’ll find is about converting to a standard RS-232 serial port. That is soooo old tech! I like what Guy Dickinson says about this.

Googling around, we found lots of level converters for RS-232 serial ports, but very little with USB in mind. In addition, most of the circuit designs for homebrew cable assemblies were quite complicated, and generally speaking, published in about 1992.

It turns out that the Icom CI-V interface is TTL-based, with the TX/RX cables bridged together, with a ground reference on the sleeve of the 3.5mm connector. Given the popularity of Arduino and similar chipsets that require a TTL serial interface to program and operate, we figured we could do better with a prefabricated USB-TTL cable like the TTL-232R-5V from FTDI. It turns out the resulting build is stupid-easy.

Prefab USB to serial cables are available for under $5. They sport a popular chip like the Prolific PL-2303HX Edition (Chip Rev D) USB to Serial Bridge Controller or the Silicon Labs CP2102/9 sinlge chip USB to UART bridge. See below – gpsd and finding the GPS via USB for using one of the cables with a GPS module.

As Guy notes, this is a “stupid-easy” method using cables originally intended for the maker crowd to program their microcontrollers. It is also ‘stupid-cheap’ and it is also open ended with the ability to add PTT or whatnot. If isolation is a concern, you can add an optoisolator or other protections. This is right down the maker alley and there are inexpensive breakout boards for optoisolators, relays, and whatnot. It’s be easy to make your own super duper rig control with, say, a small usb hub, usb to audio dongle, and some other modules.

CO detectors

The attraction of a First Alert model CO1210 was the promise of a ten year life on battery. It was installed on 1 May 2015 and declared defeat on 26 March 2017. That was a disappointment. The battery is a cr17335 Manganese Dioxide-Li/Organic Electrolyte (Maxell Datasheet) for 3 volts and 1.75 Ah. The Sanyo (datasheet catalog) indicates a ten year life at 23C at 20 microAmps with a final voltage of 2.5 volts. The battery on this detector after almost 2 years was down to 1.7 volts so something was wrong (overnight it recovered to 2.1 volts after being pulled from circuit despite the device being turned off). Here’s the disassembled detector:

First Alert CO1210 innards

and a closer view of the circuit board:

co detector circuit board

The brown AA sized thing in the picture is a Figaro TGS5042 is the CO detector (datasheet). It generates 1.2~2.4nA/ppm CO and you have to be careful not to apply anything more than 10 mV to avoid damage to the sensor.

The big chip is a PIC16LF1937. It’s an 8-Bit CMOS Microcontroller with LCD Driver and nanoWatt XLP Technology. To its left is is the RE46C107 for driving a piezoelectric horn. The op amp to get the nanoVolt signal up to the microcontroller’s ADC levels looks to be a MCP6V01.

So, it’s a straightforward microcontroller with sensor, display, and noise maker. The special thing about it is the use of low power components. In this area, the CO detector is the key item. The operating principles describes it this way:

Figaro Electrochemical-type gas sensors are amperometric fuel cells with two electrodes. The basic components of two electrode gas sensors are a working (sensing) electrode, a counter electrode, and an ion conductor in between them. When toxic gas such as carbon monoxide (CO) comes in contact with the working electrode, oxidation of CO gas will occur on the working electrode through chemical reaction with water molecules in the air (see Equation 1).

Two other types are also available. These are the MOS and Catalytic types. The Electrochemical-type is very low power but that means a very weak signal. Now the question is whether or not to put in another battery or just replace the device. 

 

Complicating decisions about small computing for low power stand alone devices

The Raspberry Pi Zero W was announced on the fifth anniversary of the original RPi. TechRepublic has the story — Raspberry Pi Zero W: The smart person’s guide. “This comprehensive guide covers everything you need to know about the $10 Raspberry Pi Zero W, the latest tiny computer from the Raspberry Pi Foundation.”

The price is getting down to where it fades into the noise for onesy projects. There are competitors like the C.H.I.P. that promise a bit more for a bit less but these currently suffer availability and support. This is full scale modern computing getting into the price range of the microcontrollers that generally have 80’s era computing capabilities plus special hardware capabilities.

A complimentary trend is that many sensors now have internal processing to convert some physical phenomena to a measurement that can be communicated via I2C or SPI or other established protocol. The RPi is well suited for this sort of thing. The microcontrollers maintain the lead when the ADC comes into play to convert analog voltages to a digital measurement. They also lead when it comes to very low power capabilities. EEVBlog has a discussion about Everything including the Kitchen sink under $1.

Another difference is about real time response in a known time frame. This could be important in a device like the NTP Stratum 1 server based on a GPS pulse per second signal in order to assure the best possible accuracy. The small computers often run Linux which is not a real time operating system and that means that there could be some latency between a PPS signal and the computer’s doing something with it. The issues are described on the Free RTOS page. The ESP8266 is a microcontroller that uses RTOS in order to multitask its WiFi radio needs and allow other processes to get done as well. The clock rate on modern devices reduce the real time issues even though higher clock rates usually mean higher power draws. The ESP8266 runs at about 80 MHZ and the RPi at 1 GHz. Contrast that to digital audio where the highest sampling rate is under 100 KHz. Even the ESP8266 can get in 800 instructions between audio data chunks.

Memory is another factor. It determines the programming for the device and impacts power draw. The ESP8266 depends upon external memory which was a major factor in its popularity. It’s internal memory for running programs is rather limited. Most microcontrollers use internal memory and that is often well under a MB in size. The small computers need a half GB for software plus external memory that often runs into multiple GB size. 

User input and output can be another issue. Microcontrollers are usually quite limited in this area as they are intended for special use devices. Computers are more generic and have more memory for user interface software. Video in this graphical interface era can be a major factor as well as it needs a lot of memory and a lot of processing capabilities.

The things you can do! That’s perhaps the biggest problem is that of trying to figure out what to do.

GPS and time

What time is it? and Where am I? – two seemingly simple questions but just look what happens when you start to explore the depths of the questions.

Mario Corchero is doing a talk on It’s time for datetime at PyCon coming up in May. “We will also speak about different standards of time, time zones, Daylight Saving Times, leap seconds, serialization and datetime arithmetics.”

Working with time is not a trivial challenge. Python includes a native module in the standard library to work with it but datetime keeps being together with unicode a common source of errors. This often leads to the widespread of many other libraries in the attempt of easing the work of working with datetime. Datetime is one of those API that looks easy to use but given the many concepts around time, is it easy to get backfired if the developer has not solid knowledge about the them.

Those are the issues at the bottom of an NTP stratum server based on GPS time. Fortunately most of the shenanigans can be left to the client so the server part can be simplified.

Another case where these issues got interesting is trying to put together a standalone clock with a Picaxe board and a clock chip. Setting the clock was a challenge for human interface ideas. Automatic DST adjustments were another can of worms entirely.

On the ‘where am I’ front is Chris Rizos And Donald Grant with How GPS keeps up with a continent in constant motion. How can you keep GPS and the map copacetic?

The Australian continent, perched on the planet’s fastest moving tectonic plate, is drifting at about seven centimetres a year to the northeast. This is taking features marked on our maps out of line with the global navigation satellite systems (GNSS) such as GPS.

These reference points and their coordinate system of latitudes, longitudes and heights are called a geodetic datum. Every country has its own datum, and the one Australia has used to date is called the Geocentric Datum of Australia 1994, or GDA94.

Satellite positioning systems – such as GPS, the Russian GLONASS, the European Union’s Galileo and China’s BeiDou – give coordinates based on a datum that is not fixed to any continent, but rather the average of all continents. So the coordinates of fixed features on the Earth’s surface, such as the Australian continent, are always changing, like slow-moving ships at sea.

Historically, coordinate differences of a metre or so have not been an issue, because positioning systems have not been accurate enough for users to notice. When GDA94 was first introduced, the GPS locations were only accurate to around 100 metres and sometimes much worse.

But two important things have happened since then. Australia has moved about 1.6 metres northeast, effectively moving the location of mapped features and their associated GDA94 coordinates.

At the same time, positioning technology has evolved considerably.

There are really two issues here. One is a model for the shape of the earth for an accurate location coordinate and the other is a map of features on that earth. Most GPS systems use a fairly simple sea level datum but allow you to choose from among the most common.See Wikipedia on Geodetic Datum. The math can be rather interesting at it is trying to model complex shapes in three dimensions and those shapes have a lot of interesting important features.

Chasing Australia as it moves northeast presents another challenge. Rather than update maps on a regular basis, the GDA94 datum might be updated instead. See Esri Australia Technical Blog Australia is on the move GDA2020.

Fasten your seatbelts!