There’s a lot of in-depth overview random basic RF information. With that said I don’t mind getting into the details because this information will help keep me safe while I perform experiments in the future.
A magnetron generates large amounts of RF energy and emits that energy as an antenna pumped through a wave guide. Most microwaves transmit/operate at 2.45GHz. Unless something is wrong with your microwave or you have taken it apart like I will be doing the RF energy, 2.45GHz, transmission is contained within your microwave using a Faraday cage. On your right is an example of a crude Faraday cage. While crude this mesh size would probably be safe to use for 2.4GHz.
A microwave oven works by pumping a lot of RF energy into an enclosure where it bombards the molecules of food or whatever you have put in your microwave. This RF energy is not in a straight line but is guided through a wave guide then and then bounced off the metal walls of the inside of the microwave. The RF energy then vibrates the molecules which creates heat. This is like when you rub your hands together (friction) and they get warm but on a molecular level. What I don’t want is my molecules to get vibrated.
The Faraday cage is made up of the mesh in the window as well as the metal case which share a chassis ground. The mesh in the window blocks the the RF because the mesh size is smaller than the wavelength of 2.45GHz/2450MHz/2450000000Hz. If the mesh size is lower than the nominal wavelength the mesh should be effective. Look at the list below to see what the wavelengths in size is. For this project I plan on using the RF blocking glass that I obtained samples of from Viracon which is way different than a Faraday cage but same principle. You can see the article I linked to but I also included an image here.
Full Wavelength = 12.23643cm/122.3643mm = 0.1223643m
Half Wavelength = 6.118215cm/61.18215mm
Quarter Wavelength = 3.0591cm/30.591075mm
You can calculate the wavelength using the formula 𝜆 = c/𝑓 or 0.1223640816326531 = 299792000/2450000000
𝑓 = frequency in hz, c = speed of light in mps 299792000, 𝜆 = Wavelength in meters
N5JLC is my math right?
So basically if my mesh is smaller than 30mm, if I’m right, I should be protected. I plan to use the glass but if needed I will use hardware cloth.
In order to protect myself and nearby electronics I want to monitor external and internal RF to ensure there is not leakage. RF Meters in general are not that difficult to build but ones that cover the 2.4GHz range require a bit more than a germanium diode and multimeter. In short you’ll probably see a 2.4GHz RF Meter project coming soon. Below are some RF Meter projects but if you know of any please let me know.
Normally I throw together a project with rough notes, research along the way, then after half attempts/failures I get around to cooking that down to a post on here. This time you will get everything. With this project I will be posting my ideas, planning, results of research and the project in stages. Here’s my initial idea written out and some really rough ideas thrown on paper. This has been a project I’ve been wanting to do for some time now and have been talking about it forever.
Roughed together a drawing of my ideas and what I think will work for this project. No measurements in mind while throwing ideas on paper.
What I want is a chamber with viewing windows to see the plasma when it’s created. In addition to the view windows and enclosure I will need a power supply to drive this thing.
Took my drawing and opened SketchUp with considerations for what measurements I do have. As I type this staring at my digital drawing already considering separating the power supply making it usable for other projects in the future. It would be cool to have a high voltage isolation transformer for things like a Jacobs Ladder or an arc furnace.
Regardless of the power supply what I have in mind here is the plasma chamber with viewing windows which are 12 inches square. I plan to have a microcontroller monitor and remotely turn on or more importantly off the chamber.
The main chamber will have the magnetron from a microwave mounted inside of it with a metal housing around it and it’s electronics to protect them. The antenna portion of the magnetron will rest inside a waveguide (horn) that points at the center of the chamber. This directed energy will excite particles creating plasma. I probably need to consider a way to draw a vacuum inside the chamber for later experiments.
I plan to use parts of the original microwave casing and sheet metal for the housing. If I need more material I might scrap old PC cases. To help minimize RF leakage I am considering using aluminum duct tape and angled aluminum.
Need to look at the manufacturer specifications and double check my work but I think this how the magnetron wiring is done minus the existing controls.
PreRelease Late Night Edit – Remember how I said I’d share everything? Well do you see where on the capacitor I have an element leading to an X? I think I already screwed up and that is supposed to be a diode going to chassis ground.
I also have this crazy idea in the back of my head thinking of using pulse width modulation to have greater control of the RF output. That may be total non-sense but the implications could maybe be cool.
RF meters will be needed to monitor interior and exterior RF levels. I plan to build at least 2 of them and will post that project soon. I will post more about the RF energy in my next post of this project.
This is a project in the works but what the hey here’s sort of a preview. The plan is to use 2x 400MHz transceivers via 2x arduinos to control the motors on this RC car. I’ve already taken the original controller board out of the car and made room for the new components.
So I was sitting here setting up a SainSmart L293D Motor Driver using specs and guidance from Adafruit and either I missed something or the information is wrong. At 3.5vdc it works but could be pushed so I grabbed an 18vdc drill battery thinking it would be fine because the circuit as quoted from Adafruit below states that it is rated to 25vdc.
25vdc my foot cause as soon as I set it up smoke popped and I smell burning on both the arduino and motor controller. It still seems to work but surely problems will rear their head.
Just ordered better motor controllers (same as the one used in my R2D2) and 18650 battery holders. Wouldn’t be so bad but I think the arduino board is fried.
My wife, MrsRedBeard, made some glow in the dark heads for Halloween decorations. They glowed but very dim and not for very long so why not kick it it up with UV lights. But why stop there when there’s an Arduino laying around?
Cut the half circles to give room for the neck. Magnets hold the spheres together. Put the half spheres together and mark evenly spaced marks around on both spheres to recess 2 sets of magnets total into each side. Don’t do like me and try and use E6000 cause it melts styrofoam, use hot glue just don’t let it get real hot.
Next for the mouth and ears. Use the paper DeadMau5 Mouth template, cut slits into the paper to get the templates to lay evenly and flat onto the surface of the sphere and tape it. Mark lines lightly with a pencil then cut using the hot knife in a well ventilated area. Be careful because the foam melts easy. Use the paper DeadMau5 Ear template to mark and cut the foam for the ears. Note that you will have to cut a curve into the base of the ears to get it to lay flush.
Now for the eyes. Take the 2 Dollar Store Touch Lights apart. You are wanting the dome that acts as a light diffuser. If you get lucky you might be able to use the leds. There will be lip around the outside edge of the dome that will need to be cut off and we used a hot knife for this.
Trace where the ears will be mounted on the sphere then cut/push a recess. Use black hot glue to fix the ears to the sphere. Paint the sphere and ears using acrylic paint. We applied 2 coats to get a good black color applied. Now take the domes you cut out and trace where you want the eyes. Cut/push in the outlines to better recess the domes. In the center of these eye traces you will want to make holes just smaller than the LED you acquired. Hot glue with black glue sticks the eyes. Make Xs on the eyes using electrical tape. Trace the mouth onto the fabric using the DeadMau5 Mouth template tracing slightly larger than the original. Using the black hot glue attach the fabric inside the mouth.
Now it’s time to wire up the LEDs for the eyes. This is pretty simple so I’m not going to post additional info unless asked. Amazon failed to deliver the Red El Wire on time for Halloween but we plan to add that soon. The Red El Wire will outline the ears and mouth.
There’s a trend of bluetooth speakers built into suitcases, ammo cans and other unconventional containers. These things sell for $300 or more which is quite a bit more than what it costs to build them. I will break down the parts, sources and their prices. This project was very easy and very affordable.
If you want a custom speaker built just contact us!
The amp is rated at 50 watts per channel and the speaker is rated at 100 watts. This build only uses one speaker so I bridged the amp to output 100 watts. This amp will run off 12vdc so a portable version would be an easy build.
Speaker mounted and working. It can get pretty loud and sounds great.
I’ve been wanting to make a Donnie Darko Frank the Bunny mask for some time now and finally got around to doing before this last Halloween. Disclaimer I’m no sculptor and have no experience with this. Definitely not perfect and I’m going to retry for something better later but I’ll share anyways.
I used a combination of paper mache and paper mache clay to make this mask. Paper mache clay is awesome!! I started with a styrofoam form and a blank plastic mask (that was too small).
Cara Brookins has a write up on paper mache clay. Cara is an author and super mom who I hope to interview after reading a few more of her books. I had the pleasure of meeting Cara a few years ago at River City Comic Con.
As you browse through the progress you’ll notice I started off with an uneven form and it never got better. I thought I’d fill in the lower jaw area to make the mask fill the outline of the printed mask but then removed it with haste. I also found out late that the paper mache clay needs to be kneaded and worked for a while before it becomes pliable. The mask ended up being a bit small but weighed a ton like hurt your neck ton.
I learned a lot from this project. I’m open to any tips you might have for the paper mache clay and sculpting in general.
I’ve been toying around with playing music using simple tones on the Arduino. I’m no composer or musician so looking around for sheet music I eventually stumbled across MXL files on a few sites like MuseScore.com. Below I have posted a sample of the Arduino playing the Stranger Things theme song.
MXL is a compressed XML file that contains the Sheet Music data, Credits, Parts, Voice Definitions, Notes, Tempo and Durations along with other information. Basically a universal format designed for composing music, project sharing and several additional applications.
Ok so MXL files, what I keyed in on was that the MXL file contained the Notes and their Durations. This is perfect because you can create a simple Arduino code to play notes if you have this information. Sorting through these files is very daunting and time consuming so I decided to create a simple app to parse this information to use it more easily.
This app was banged out pretty quickly so please forgive possible errors. Because some MXL files are compressed and others are not I built in the code necessary to unpackage the XML before parsing. The app allows me to separate the notes by voice with their durations. In addition I placed a numeric control that limits the amount of notes that get parsed. A screenshot example is on the left.
Huge thanks to Shvelo who’s Ruby code got me pointed in the right direction.
Playing the Stranger Things theme song on the Arduino was a bit tricky tweaking the tempo to make it sound right but way easier without having to manually extract the notes and durations. To the left is the simple Arduino setup using piezo from a walkie talkie wired to pin 8 and ground on the controller. Ignore the other wires because they’re not used here.
A follow up to yesterdays article “Oh Reddit how you hurt my brain” highlighting awesome physics talks on Reddit. This is a mind expanding nugget PBS Space Time that started out as a suggestion from Mick who never fails to deliver.
This is just a highlight and only one of the PBS Space Time videos on YouTube “Is Gravity An Illusion?” If you’re interested it would be a good idea to watch the entire series in order and some videos more than once. The videos build upon one another increasing the amount of knowledge you will have and understand.
It’s amazing how a simple question can open a pandora’s box. Mick shared this Reddit thread and I just had to share with you guys because this is exactly the kinds of conversations we have together on regular basis but mainly from the perspective that we want to know and are seeking answers.
A lot of questions are quickly given a simple answer only to followed by a more complicated and drawn out answers that only lead to more questions followed by more answers and only more questions until people I start to drool and fall over.
For example Hey Ash how did you get the Avocado Mustache? Then the answer would follow as Well you see….. Starting at the beginning giving background but that only leads to more questions and WTH’s. mickred.com/ash #AvocadoHalf
RobusEtCeleritas – Even though changes in the gravitational field propagate at finite speed (c), and it takes about 8 minutes for signals from the sun to reach Earth, the Earth accelerates toward where the sun is now rather than where it was 8 minutes ago.
Totitiganiisuntgunoi – The slightly more exact answer is that the Earth accelerates towards where the Sun was 8 minutes ago extrapolated to where it would have moved based on its velocity and acceleration 8 minutes ago. The fact that the position is not quite the same as the “instantaneous position” (ignoring complications due to relativistic fu$%ery), is the very reason why the Earth-Sun system spits out gravitational waves.
And Bam! Another question
WiggleBooks – How is that possible? How is that information (velocity of the mass) encoded in the gravitational field?
See the internet is not pointless and full of hate…. But it gets deeper real quick. This guy has a grasp on the topic that I do not possess and yet it goes back a few times to re-explain and get his answer straight.
Erremermberderrnit – I don’t know how, but for relativity to work, it has to be that way. Because of relativity, even though the whole solar system is moving through the galaxy very quickly, all the parts behave as if the system were stationary. If the earth was attracted to where the sun was 8 minutes ago relative to its position in the galaxy, we’d be orbiting a point roughly 110,000km away from the center of the sun.
EDIT: Oh hey, I just thought of a good way to explain how it works, and it’s actually pretty simple. Just imagine a ball moving through space emitting pulses. The pulses are traveling outward from the ball, but they’re also moving in the same direction as the ball and at the same speed. If the ball suddenly stops moving, the pulses that were emitted when the ball was moving will still be traveling along at the same speed.
I guess when gravity waves are created, they inherit the velocity of the thing that created them.
EDIT2: I crossed out the last part because it occurred to me that, since light doesn’t carry the inertia of the body it comes from, then gravity waves probably don’t either. So I was trying to understand it, and I found something that seems like a paradox. Let’s say you have a ship moving through space and it emits two beams of light, beam A in the direction it’s traveling, and beam B in the opposite direction where it came from. If an observer on that ship measured how far the light had traveled after a certain amount of time, he would see that both beams had traveled the same distance. But, if you had a stationary observer, he would see that the ship is closer to beam A than beam B since it’s traveling toward A. So how can both of these scenarios coexist? What am I missing here?
EDIT3: OK, so thanks to some explanations, I understand this a little better now. Back to the metaphor with the ball, to the stationary observer, the pulses don’t travel along with the movement of the ball, they just travel directly outward from where they started. BUT, from the perspective of an observer on the ball, the pulses, as far as he can tell, ARE traveling along with the ball. If he were aware of the experiment going on and knew that he was moving relative to the stationary observer, and saw that the pulses stayed centered around the ball, he might conclude that the pulses inherit the balls velocity, even though it’s really an illusion.
So, if there were an object orbiting that ball, and you wanted make calculations about it, you would calculate as if the pulses were moving along with the ball, even though they aren’t, because from the ball’s frame of reference, they essentially are.
On a related note, I suppose that, even though we see the sun as it was eight minutes ago, it appears to us to be where it would have traveled to eight minutes later. So even though there’s a delay in the light, we still see it in its current location.
I think so anyway. If this is true, would the same thing apply to distant galaxies? If we look at a galaxy a billion light years away, we see it as it was a billion years ago, but does it also appear to be in the location it would have traveled after a billion years? Or does it appear to be where it was when the light was emitted? Would we have to be moving along at the same speed as that galaxy to notice any strange effects like that?
Holy crap that is a lot to take in. It was right about this point where I had to shake my head just to get another perspective. I’m feeling like I might have an insight then danggit
Invisibowl – Hm, so does the Doppler effect apply to gravitational waves?
This goes on and on for a while but isn’t even the entire thread. In fact another sub thread hits a real simple answer.
DouglasPR – In my understanding, the gravity connection between the sun and earth is not “pulsative”, like one sphere is “not there anymore” on the next pulse or cycle. To me its more like a string (a eight light minutes long string) connecting the two spheres, the bigger pulling the smaller around the galaxy. So earth is always being pulled towards where the sun is now, but the “string” is slightly “bent”, because its that long.
With further simplification
Wake_and_Poi – This is my understanding of it. It may take 8 minutes for information to travel along the tether, but it is still a tether.
I feel like this should be taught to everyone in the primary schools because I feel like I’m being taught something new every time I go down the road of (whatever flavor of) physics. To be honest these threads, PBS Space Time, Scott Manley and KSP are the equivalent of a college degree when you finally break through the threshold of understanding turn around and can explain this yourself.