A little bit about light

I’ve been giving myself a crash course refresher on light over the last new months. It started when I picked up a used Laser Cutter and wanted to figure out how it cuts with light. What I’ve written here is my understanding of things. I may be wrong, if so, please let me know in the comments.

My simplification of a CO2 laser is that it’s a poorly designed Neon light that gets way too hot and produces a heat ray that we can manipulate with mirrors to vaporize things. Magnifying lens on a sunny day style. I fear if I ever find an ant in my laser cutter whatever project I was working on will be a total loss as I will be chasing the ant with my laser beam. https://en.wikipedia.org/wiki/Carbon_dioxide_laser

So I now have this really sharp cut thing that I can’t see the blade on. A CO2 laser beam is invisible. If you see a red dot on a laser cutter, that is a separate cat-toy style red laser put in place so we can guess about where the actual invisible laser will do it’s thing.

Deep Infrared thermal image of laser cutting fabric
The heat line produced by laser cutting some fabric in a laser cutter
laser cutting fabric
The laser cut fabric. You can see where it has cut the fabric using focused invisible light.

My laser cutter’s light is 9.4-10.6 micron wavelength. This is the same wavelength that Humans glow in the dark. Well, everything room temperature glows at this light frequency or ‘color’.

Deep Infrared

A thermal camera can see light in this ‘Deep Infrared’ zone. I have a Seek Thermal camera that plugs into my cell phone which allows me to see effectively heat. I can walk around and find things that are plugged in that are doing a bad job of being off, and give off heat because they are still on. I can tell the temperature of anything, just by looking at it with my cell phone. I can also look for things that are supposed to help keep me warm and are failing at their job like doors and windows.

A Deep Infrared image of a Kurig Coffee Machine
A Kurig Coffee Machine that wasn’t told to ‘power save’. It’s been heating up since it was plugged in.

Except nothing is ever that simple. Materials have a property called ‘emissivity’. This is how well they emit light at a certain wavelength. Things that emit light well, tend to absorb light well. Things that don’t emit well tend to be reflective in nature.

Humans have a pretty high emissivity about .98 (with 1 being perfectly emissive and 0 being perfectly not-emissive) so we need clothes to stay warm as we would glow all of our heat away without them. But because we are highly emissive, we can absorb heat well too, so this is why you can feel heat being given off by things like hot pans, light bulbs, and turtle heat lamps, and sitting in a sunny spot.

You can see here that I glow. My clothes hold in some of my heat and my glasses block the Deep Infrared light.
You can see here that I glow. My clothes hold in some of my heat and my glasses block the Deep Infrared light.

Things such as shiny metals have a low emissivity, so they tend to reflect heat like a mirror. This is how camping space blankets work. The thermal ‘glow’ that us humans have gets reflected back at us. We absorb a lot of this reflected heat, so space blankets feel warm to us. Because, you know, science and stuff.

But, what this means, is that my fancy thermal camera can’t take accurate temperatures of shiny metal things. What I am really taking the temperature of is the things reflected on these ‘heat mirrors’. To do a good job using thermal imaging for temperature reading the more expensive equipment has material tables that you can assign to spots that have a lookup to a emissivity table so it can calculate the proper temperature based on what it sees.

I am going to carry some electrical tape which has a pretty high emissivity number around .96 and just stick that on things I want a proper temperature of. Because, you know, lazy and stuff.

Materials have some pretty funny ideas about what is ‘clear’ and what is ‘opaque’ at wavelengths other than what we can see with our eyes. Thin plastic bags that we can’t see through are transparent to deep infrared. Stick your hand in a bag, you can see your fingers as clearly as if the bag wasn’t there. Windows, glasses, things that we see through all the time are as black as night to thermal. “Low E” windows are not only black to thermal, they are reflective as well, so you can see your heat reflection in a ‘good’ modern window. CLICK. OH, that’s why “Low E” windows are better, they reflect heat. I get it now.

Near Infrared

Another portion of light, called Near Infrared, has some interesting properties as well. First off, things that aren’t metallic (reflective) are rather transparent. Things look kinda like jello at these wavelengths, the light can see into them a ways. A couple of centimeters often times.

The Near Infrared has another interesting ability. Oils, fats, sugars, alcohols, and proteins absorb certain frequencies of light – they have colors (for lack of a better word) in this range. Click here to Geek Out on Near Infrared. This means that a camera that uses Near Infrared is very useful around the house. We can look at something, and judging by it’s ‘color’ in Near Infrared, we can make a good guess as to what is made of, or at least major components of it. We can’t see near infrared, so we tend not to manipulate the colors in that range.

There is a gadget that takes advantage of these useful properties. The SCiO which is a Near Infrared ‘scanner’.

This little device is even cooler than the thermal camera. It’s small, and can tell you the interesting bits about your food like how many calories and of what type (fats, carbs, protein) are in it. You don’t have to guess at a restaurant if you are tracking your diet anymore.

This doesn’t work like a camera, it is instead a spectrograph. It doesn’t take a picture of stuff, it instead looks at all the colors that are present like how a prism works. You scan something with a SCiO and it breaks apart the intensities/brightness of different wavelengths of light (those would be the colors if this was visible light) and looks up what it sees against a database of stuff that it knows about and when it finds a match, tells you what it is looking at.
If we were to present only pure substances it would be able to tell us what things are easily. However, we don’t have much of anything that is truly pure. Table salt, sugar, baking soda, for the most part tap water are about all I can think of commonly around the house. Most of the stuff we interact with is made up of a variety of things.

This is where we get clever with the SCiO. Instead of needing to extract out the stuff into individual bits (imaging taking a baked cake and separate it back out to it’s flour, sugar, eggs, milk, water, etc) we just capture what a thing looks like in different bits of Near Infrared light and correlate it to things we’ve told the SCiO what they are previously.

The thing that makes this work is that we LIMIT THE DOMAIN of what things are so the SCiO has a chance at making a reasonable guess. For example, there are a lot of things that are Red. Lego, fancy cars, strawberries, some apples, etc. If we showed you a particular shade of red, and asked you what was that color, you can come up with a lot of wrong answers that are that exact shade of red. But if we said we have a berry that is this particular color, you would be able to tell very easily what it is most of the time. Especially if you can look back against other color samples and compare what you have now with what you have seen in the past.

So for the SCiO to work well, we need to train it. We get together a bunch of things that we want to tell apart if it’s not properly labeled. We then teach the SCiO this thing is X, that thing is Y. We can than ask SCiO what is this stuff, it’s something that belongs to this group that we trained it on.

An example could be clear liquids. Clean water, vodka, strong vodka, watered down vodka, rubbing alcohol, denatured alcohol, clear soda, vinegar. These things all look similar to our eyes. They will all look different from each other in Near Infrared. We can train the SCiO about all of these clear liquids, and when we find a glass of one and we don’t know what it is, we can check with the SCiO.

Amazing!

There are some ways in which the SCiO can fail.

  • Shiny mirror like surfaces tend to reflect all light, regardless of the wavelength. Metals for example. We also see this in Visible light as well as Deep Infrared.
  • Things that are black – they absorb light – tend to absorb all frequencies of light including Near Infrared. Things that have been colored black will likely be black to the SCiO as well, and it can’t get a good read on them.
  • Only the major components of something can be read by a SCiO. If there isn’t enough of something to make a strong ‘color’ influence, it simply can’t be read. A SCiO can ‘see’ stuff that is more than 1% or so of the overall item.

 

Understanding how a fancy new tool works ‘under the hood’ helps me manage my expectations of what the tool can and can’t do well. I can ‘hack around the edges’ of it’s capabilities because I understand what the edges of capabilities are and why they exist.

Internet of Things Phone Smart Charger

I pre-ordered one of the Samsung Galaxy Note7 phones. The ones in the news recently for being an explosion hazard.

I love the new phone – pocket computer really, the way I use it. I wasn’t about to give it up over some silly thing like spontaneous combustion.

I had read that Tesla runs their car batteries between 40%-80% for normal use to maximize the lifetime of their very expensive car batteries. I figured that cell phone batteries would benefit from similar treatment. A bit of research generally confirmed this, with http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries being the most concise write-up. The first half basically demonstrates that you can get the same amount of total power to flow through the battery regardless of how much you charge it – summed over the total life of the power draw in the data tables. The 2nd half is more interesting. It says that high voltage charges and heat shorten the overall lifespan of the battery.

The Note7 is a sealed phone wihtout a replaceable battery. I can’t pull my usual trick of replacing the battery after a year of abusing it.

Heat seams to be the trigger for the phone explosions. So I can make my phone more safe, and make it last longer by managing the top voltage and heat in the battery.

I can do this.

I bought a wireless Qi charger to charge the phone because it charges slower. The fast charger can charge the phone crazy fast, but it gets HOT when it does this. Hot is bad. Thus, slow is good. The wireless charger will also reduce wear on the USB C port. A nice side benefit. No phone explosions while I sleep and burn the house down – this is a good thing.

I bought a Belkin WEMO wifi controlled outlet. It is If-This-Than-That (IFTTT.com) capable so I can control it from my phone. There are other smart plugs available that will work, this is simply the one I could find in a store that I could verify would work with IFTTT.

I configured IFTTT to have 2 different actions. One for turning the WeMo on, the other off. I set these up as Maker Channel triggered recipes. There are other triggers that you can use such as email or SMS, but I am a web developer, so web-based triggers are a natural fit for me.

Image of The Rules set up in IFTTT
The Rules set up in IFTTT
Photo of the IFTTT Off rule
The OFF rule in IFTTT. It uses the Maker Chanel for the trigger, which means a web request will trigger this. It turns off the WeMo controlling the wireless phone charger.

I installed Tasker on the phone and configured it to monitor charge state and battery temperature.

I created 3 tasks, one to turn the charger on, and two to turn it off.

photo of Tasker rules
The rules in Tasker to control the phone charging.

The ON trigger looks for the battery to be below 80% charged, and below 35 degrees Celsius. This will make a request to the IFTTT.com Maker Chanel URL for ON.

One OFF trigger looks at the battery temperature. 35.1 degrees or higher. The other OFF trigger looks for the battery charge to be 90% or higher. These two both make a web request to the IFTTT.com Maker Chanel OFF URL I set up.

So now as the phone battery heats up or gets close to full, the phone tells the charger to turn off. I let the phone have a 10% charge window so I am not toggling the switch and charger on and off all night long.

Tasker with both OFF rules turned on. The phone is both charged to 90% or more as well as running hotter than I would like.
Tasker with both OFF rules turned on. The phone is both charged to 90% or more as well as running hotter than I would like.

I also programed the WeMo to turn itself on a little while before my alarm is set to go off. This is to let the battery be closer to 90% charged rather than 80% charged when I wake up. I haven’t found the right time for this yet. I still need to play with it a bit.

I know there are other ways to make a smart phone charger. This is what I came up with. I will be getting an additional smart plug and building one for at the office so I don’t over-charge my phone when at work. I will try a different brand likely to see if I can come up with a cheaper way.

I recently picked up a used CNC Router

It's a big machine for the hobby side of things. I think they call it a 60150. It will hold a 2 foot by 4 foot piece. 220v water cooled spindle. It's a solid machine.

It had been suffering from disuse – not neglect, just simple not getting used enough. Rust pitting on the important bits and some rusting on the threaded rods. A couple of years in an unheated garage without being used to re-coat all the parts in oil will do this.

Not too much work to clean it up. It took a couple of evenings over a couple of weeks. Last night I got the electrical stuff all sorted and got it to move!

So I dug up a bucket, and connected water and electricity to the same spot on the machine. This is generally a bad idea in my experience.

It cuts! A little bit of tweaking, and it cuts correctly!

About an hour into running it, it gave an error and shut down. Not really sure why, but I think it's because the controller got hot. There was a reading of 75c on the screen when I was pushing buttons. I think I found why the controller box was open.

Next project is to improve the airflow in the controller box. I have a plan for this. I will install rubber grommets around the holes the wires poke through too.

I also need to learn about "Speeds and Feeds". CNC Routers have an ideal window where they work well for a given material. The 3D printing methodology of slowing down, sorting things out, then speeding back up does NOT apply to CNC Routing it appears.

Lots of photos in the album. Each one is captioned.

CNC Router Refurb
27 new photos · Album by Mike Creuzer

I got a mosquito hammock this week for $30 from woot

This is pretty cheap. After I ordered it, I realized how short it was – it's six inches shorter than the one I already have. Short hammocks and tall people make for an uncomfortable night's sleep. So I decided to try to cheat the length a bit. I converted it to a Mini bridge hammock. Some amsteel rope dogbones, a pair of spreader bars, and it's a non-damaging modification. I think it worked. I slept in it as it came, and after the modification and I like the mod. It's much more comfortable. Not perfect, I find my feet tend to rest against the netting.

Next project. Down underquilt.

In album Miniature Bridge Hammock modification

My girls hanging out in my new Yukon Outfitters Mosquito Hammock

It’s a clear tarp for me for the hammocks. Window winterizing film, duck tape & patience to make one.

This is how the hammock came. A rope (which stretches a lot the first night you use it) fed through the channel and closed on itself. Here, I’ve had to run it back up to the metal connector so tighten the hammock at 3 am so I wasn’t dragging on the ground anymore. Notice how tightly it bunches the end of the hammock up. The thin line is the stretch cord for holding up the bug net part of the hammock.

This is a miniature bridge hammock. The idea is to make the ends wider so it squeezes against the shoulders less. It is also supposed to reduce the tightness up the center under the legs that can cause discomfort.

I made 4 amsteel dogbones. These are just short ropes with eyes on both ends. I sized these so they are short as they can be and have the right length bury that nearly touches in the center.

Try to make all 4 the same length.

The amsteel dogbone is fed through the hole in the wood, fed through the hammock and  the loop slipped over the end of the wood. Do this from each side.

It’s easier to pull the new rope through as you are pulling the old rope out. (trust me  I know)

But it’s easier to untie if you put the old rope to the new, and not the new rope to the old. Oohps.

The hammock is clipped into the rope that it hangs from.

The offset in the carabiner can be used to advantage in counteracting any differences in the length of the amsteel dogbones.

This is with the original mounting method.

This is the girls swinging in the new method. Notice how the end of the hammock forms a gentile curve.

The hanging hardware that came with the hammock – both sides.

The new hanging hardware weighs 2 grams more. Now, this is a cheating weight, as it doesn’t include the carabiners.

I picked up a new 'backpack' this weekend

227 grams, without the two dinky water bottles it came with.

It's going to be challenging to get a 3 day trek into this itty bitty waist bag. Warm weather trips only.

My last weekend trek last fall, water became a problem, so this is probably a bit water-focused.

I am making 2 leather pouches for the Sawyer Squeeze Mini water filter and the cleaning syringe. One tucked into each side next to the water bottles. I cut the 'straw' down so it fits inside the back of the syringe handle. The squeeze bag fits inside the pack.

The kids are getting the half liter water bottles that came with this bag. I am replacing them with larger bottles. The silver bottle pictured will likely be my Berky Sports bottle once I find it. The green bottle in the black sleeve has a soup can it is nested with for a cook pot.

I am making a new 8.5' square tarp out of a window insulation kit. This will eat up the bulk of the pack. Cordage to pitch the tarp are 25' and 10 foot pieces of Amsteel Blue (silver colored) wrapped around the outside of the pack and held on with a soft shackle. Also will have several lengths of braided mason line.

Other items include:
A SOL 1-2 person space blanket or two for sleeping.
A disposable clear rain poncho in case it rains.
A bug head net.
2 citronella tea light candles.
My new LED headlamp with the 3d printed red lens.
A norwex towl (my wife can't stand the feeling of them).
A long sleeve polyester shirt.

I need to make a 'repair kit' with neosporin, tape, a needle and thread, a bit of wire and the like. Stuff to keep me and my gear walking.

Sticking it all on a scale at the moment, 1610g or 3.5 lbs.

What am I missing for packing out my new 'bag'?

In album 2014-05-26

My new waist bag. I like the color and that it can hold 2 water bottles. I have some amsteel rope wrapped around it. I am making a pair of leather pouches for holding the Sawyer Squeeze Mini water filter parts.

The leather pouch on the right side will be added and a mate to it on the other side.