Upside down electrical outlets

Does your workshop or garage have outlets along the wall, are they “normal” aka upside right with the ground pin at the bottom of each outlet?

protect outlets with the ground pin up
protect outlets with the ground pin up

I was initially confused when my electrician wired the outlets along the walls in my shop. Hi installed the outlets with the ground out at the top of each outlet.

I thought this was a mistake and asked “why”.

He installs the ground pin at the top in the case something metal might fall over on a cord plugged into the outlet. Rather than the metal contacting the two live prongs, it harmlessly hits the grounding pin.

While it’s not a 100% guarantee to prevent electrical shorts, it does provide a much better margin of safety!

A trick for taper a cutting

A well equipped wood shop will have a cutting jig for those cases where a piece of wood need to have taper – a common example is a tapered leg on an end table.

If you don’t have a taper cutting jig, there is an easy solution.

tape scraps to the working piece of wood
tape scraps to the working piece of wood

Take a piece of scrap wood longer than the piece you need to cut. Also take a small piece of scrap wood that is narrower than the taper you need to cut – for example, if you will cut a 3″ leg with a 1″ taper, the small piece of wood will be less than 1″ wide. This narrow piece will be a spacer block.

Rest the long scrap against your table saw fence. Rest your piece of work against this scrap. Slide the narrow scrap between the two pieces of work from the far end, creating an angle between the scrap and the piece of work. Adjust the location of the spacer to get the angle you need. The easiest method of getting the correct angle is to mark the work piece where the taper will start and where it will end. Now slide the fence over until the end-mark aligns with the saw blade. Slide the three pieces of wood together along the fence to the start-mark. Adjust the spacer block until the mark aligns with the blade. Now tape everything together.

Cut the taper by running the taped up part as one piece of work.

Air management firefighter training

Dodge Ball helps firefighters tain with breathing apparatus

Dodge Ball helps firefighters tain with breathing apparatus

“Mister Firefighter” – can you explain a bit about what air management is and some of the situations where it is critical?

Air management, simply put, is the air in my tank, on my back, is only good for 30 min., and 30 min. is measured in a “resting state”. So, managing your air under duress is critical to getting the most out of your bottle. Cardio, among other things exercise is the start to getting the most out of your body, thus your bottle. Which is why a lot of guys run to keep cardio up, to better manage their air.

Here, with dodge ball, you get a number of good things out of it. Obviously good body mechanics and cardio, perhaps the two best are stress relief and use of spastic muscles, which is what tends to be used he most during fire suppression activities. Only thing left out is weight training.

In a trainkng exercise like the video, what might the duration of a tank be for a highly cardio trained firefighter vs someone like who is a couch potato?

20 minutes for good cardio, probably 5-10 for the couch potato.

Thanks for your answers. It’s easy to see, when in a burning building for a room by room search – 10 minutes doesnt leave much time and the additional 10 minutes is very significant.

Graphic Designer … when it’s called for

the Stratux logo

the Stratux logo

I like working in design teams for two reasons. First, collaboration will provide better results than working in a vacuum. Second, we can call upon our collective strengths.

I’m not a great visual designer. I usually describe myself as “graduating with a 3rd grade art degree in crayon” … and I hope I’ve not offended any 3rd grade prodigies.

In a pinch, I can manage but there are far more talented people than me when it comes to artistic style and tenor.

So, without immediate access to a better option, the logo for the Stratux project fell to me. It gets used for the slash screen, desktop icon, and it’s even been used in a couple of the 3D printed cases.

I think it’s holding up well.

I’ll have a Stratux with Everything! (a DIY ADS-B receiver)

As an excuse to learn some new skills, I’ve been volunteering code to the Stratux open source project on GitHub. My contribution is the mobile web app used to setup the device and to verify everything is functioning properly.

This post isn’t about the user interface or the code. It’s about the hardware.

my Stratux with Everything (SWE)
my Stratux with Everything (SWE)

In order to do the development and test my code, I needed to build one of these devices. They are not hard to build and there are three levels of equipment to choose from. The good news is you can build the entry level version and just add parts to get to the second and third levels.

I started with the basic Stratux which is a Raspberry Pi 2, an SD memory card, a wifi USB adapter, one SDR, and a USB battery. For people new to the Raspberry Pi, the easiest solution is to get the starter kit because it includes the right wifi adapter, the SD card and a convenient case for the Raspberry Pi. If you don’t mind the “slow boat from China” for delivery you can save some money by getting the same SDR in different packaging – just make sure any SDR our buy uses the newer R820T2 chip. Most sellers are making it very clear in their description.

I had some of the parts on hand including a bigger version of the battery, but more about that later.

Initial assembly was easy. All I did was follow the instructions from the sticky post in the reddit subgroup.

Once I checked that it all worked I started adding to it.

To get together second level of a Stratux you just plug in another SDR and edit the config file to say it’s available. (Yeah, not a great user experience and the first hint I might want to get involved.)

To get together third and final level of Stratux you add a GPS module.

the RY835AI GPS / AHRS module
the RY835AI GPS / AHRS module

The actual module is the RY835AI available on eBay. It’s compact and surprisingly capable. It’s not only a GPS receiver but also an AHRS (attitude and heading reference system). What this means is it contains both a solid state magnetic compass and the ability to sense left/right and fore/aft tilting (in an airplane we call these pitch and roll).

I followed the instructions sprinkled through the reddit subgroup to get the GPS connected. Then editing the stratux.conf file to enable it.

With all the parts connected and working I wanted to hide all of the wires and parts in a case. I tried a few ideas with things I had in boxes or closets or forgotten in the shop. None were quite right. I finally settled on a case from Serpac, the A-42 enclosure. As one person put it, it has “just the right amount of retro 56k modem” feel.

The two major constructions made it all work. First, I had to un-case the battery and folding one set of cells on top of and offset from the other set of cells. Second, I had to fabricate a tiny dual USB cable.

dual USB cable flips USB ports 180 degrees
dual USB cable flips USB ports 180 degrees

I received a few questions so I thought I’d include the answers in this post.

“Can you show the inside?”

I had already noted things were right inside the case. This should explain just how tight.

inside the Stratux with Everything
inside the Stratux with Everything

“What about heat?”

Using the mobile web app I’ve been developing, I can see I both the Raspberry Pi CPU temp – typically around 53c – and the temp sensor on the AHRS – around 44C. But those number go up somewhat when the Statux is in direct sun, such as on the glare shield under the bubble canopy of the airplane. Fortunately, the light grey case minimizes solar heat saturation.

“I noticed the CanaKit WiFi adapter in the pic. Did you compile their drivers into the software?”

The Stratux project uses an Edimax wifi adapter. For some unknown reason, my original wifi dongle went wonky. I had the CanaKit dongle sitting on my desk so I did a one time build of hostapd 2.4. Now I just copy it over if/when I flash the SD card.

“Which antenna are you using with the SWE ?”

I’m playing with a few different antennas. Next up will be an antenna design and sold from a Reddit member. I will also make the j-pole and try that as well. The nice bit is the BNC connector allows me to use common antenna connections.

“Is the SD card accessible?”

The SD card is only accessed by opening up the cover. It’s not ideal but new releases is Stratux are slowing down and I think it will stabilize in the near future. Most of time, I use the Ethernet port and rsync new source onto the SWE and rebuild.

“Are you passing through power while charging the battery?”

That’s an Interesting question. I wondered why all of the USB batteries I’ve seen charge or power. But not both at once. I figured it out when I cut open the battery pack.

These batteries are built as two “banks” with each bank generating 3.7V. The charging circuit feeds these banks in parallel. This works because the 5V charge voltage is greater than the 3.7V. The two banks are run in series through the regulator circuit. This works because the 7.4V is greater than the 5V output.

It would be much more complicated to charge the battery while also having the battery discharge to a device.

While it would be possible to feed the battery and feed the RPi, it would be messy since it would require a diode to prevent back feed into the battery.

Besides, at 20800MAH, the battery will power a fully loaded Stratux for 9-12 hours. It requires up to 20hrs to fully charge.

Perhaps the most important question was not asked. “If you did it again, what would you do differently?”

I’d change two (or three) things. I’d use a smaller battery solution. The 20800mah is overkill and the interior is very tight. I’d trade some capacity in favor of some room there are newer batteries that are in the 10,000mah range which are very compact.

By changing batteries I’d also end up changing the availability of “output power”. That would mean building another custom USB cable. I’d have only one output available. This would free up some space on the end panel. It would also give me more options for placement of the parts.

A friend picked up a low cost 2-line text screen. I’d love to integrate it to display status. In order to add this screen to the case, I’d have to do #1 first.

I posted more pictures to imgur. interior: exterior:

Marketing Warning: USB Batteries Capacities are Misleading (but not lying)

If you’ve bought a USB charger battery you are familiar with how they are all advertised using a “MAH” (milliamperes hour) rating. You will see small units at 3200MAH, mid range units at 6000MAH and 8000MAH, and big / ultra sized units at 10,000MAH and up. 

As someone with a modicum of electrical understanding I know that USB is a 5V solution. So, this leads me to believe the advertised description of these units to mean deliver the 5V output with the rated MAH.


I’ve gone back and read many of the product descriptions very carefully and none of them make that last claim. That’s a good thing since they don’t. What the manufacturers do is place the MAH rating in the name of the product and then describe the product with the phrase “capacity”. They are careful (or clever or lucky) to no combine the capacity with the USB voltage.

How can I be sure?

I have used one of the ultra sized 20800mah USB batteries – the Anker E6 – for almost a year. Don’t get me wrong, it’s a great battery and I would recommend Anker to anyone who asks. It just happens that it was one of their batteries which exposed the marketing of these batteries. 

The other day I did something no one is likely to do – I cut my Anker E6 open. I know it voided the warranty.

What I found was eight LGDBB41865 batteries. These are 3.7V @ 2600mah. They are wired as two sets of four. The result is 7.4V @ 10400mah. Circuitry then create the stable 5V USB source.

The marketing for this battery *implies* it provides 5V @ 20800mah. It does not. The marketing claims “20800mah capacity” which is accurate.