You might be wondering why there a large 130 written on my stove and why it keeps changing
back and forth.
Well, I wanted to make a non-contact thermometer that can probe the temperature of something
on the stove.
Not just non-contact like your ordinary pointy device that can measure temperatures but one
that also projects the temperatures of the thing it's measuring.
And uuh that was kinda easy, let's see what are the temperatures of something else like
the stove itself, if I take that off, or the average pan of this bacon right here.
So all of this is actually done with this projector that lives on top.
Inside, it has a non-contact thermometer right there and if you can see it, a lens that focuses
the circuit board, and it's all inside this nice little box with this little slidey thing
on the front (printed this on the mill) so that it can uuh change the focus of the number
down below.
Time to flip.
whoo.
Anyway, all of this works together form this nice little 5V supply over here to project
the average temperature of this little pan right here onto the stove.
Let's see how I made it.
You can see a little clearer here.
On the surface here is the non contact thermometer which is pointed at a pretty heft offset and
the actual lens.
And, down below is a circuit board.
All of this is able to be refocused.
Oh and some magnets to make it stick to my hood here.
So, uuh let's take off the front here and see what's underneath.
Oh, one of the other neat things is the non-contact thermometer actually comes around back so
it can slide forward and backward without breaking the wires.
Down below in here is a small boost power supply in order to take the voltage that's
coming off of the 5V supply and boost it up enough in order to have three of those amber
LEDs in series.
Each digit is made out of three LEDs instead of just one and uuh does it all in series
so we can use less current.
The supply also makes it so it doesn't matter what voltage is coming in, we can control
the voltage going to the LEDs on the board all the same.
Let's see how that little purple circuit board in there was made.
Initially I strapped a bunch of LEDs and some digital controllers to this circuit board
here.
It was a little too big though.
They were too large and it just didn't project.
So, I had to go smaller yet, from 0805 LEDs to 0402s.
Can't seem to get those quite in focus, but I guess you'll see over the next few clips
how this all goes together.
So, I started by getting an osh park board.
These things are really high quality.
Then I just gooped some solder paste down.
This is bismuth solder paste.
It's some amazing stuff.
It reflows at a much lower temperature than most solder pastes.
You can see just for size comparison, that's a little itty bitty QFN chip.
Some of these LEDs here are the 0402 LEDs.
They're incredibly small.
And I can just barely see them.
And I guess some of the other neat things you can see going on here is you can see some
of the itty bitty beads that are inside the solder paste.
Solder paste is actually this kind of flux material with a whole bunch of suspended microscopic
balls inside of it.
Any rate, I put the paste down with a toothpick and I put the LEDs just kinda manually using
a pair of tweezers.
Tried to get as many as I could, tried to get the orientation correct.
I really just couldn't see them but I could kinda see when something was wrong.
Just gotta get all the little LEDs placed right and uuh then I could move on.
Well, it's time to go into the toaster oven.
For comparison there is my finger.
Look at that.
Look at that wonderful cooking those circuit boards to perfection.
When I use the solder paste like this and just goop it everywhere.
I get tons of solder bridges on all of my parts including these QFNs right here which
are well, I used to think they are a pain till I found out you dab a little bit of flux
on.
Take a soldering iron, just rub it across the chip there a couple times.
Maybe need to clean off your tip and it pulls the bridges right out.
Look at that!
Perfect!
I uhh also wanted to clean up some of the other aspects of the circuit board here, so
you can see under the microscope that when I put on some flux and I take the soldering
iron up against the pads you can just pull out all the little inaccuracies.
All these little annoyances here.
And, I also needed to go in so I could clean up the LEDs and make them more well better
aligned with where they needed to be.
It looks like it operates the same.
I'm putting my hand here to warm it up a little bit and letting it go.
Let's see what happens when I hook it up to some optics.
It's much smaller and more readable at a distance.
In fact, I think it's probably good enough - whoof, let's see if I can get this back
in the field of view here.
I think it probably is good enough to make the rest of this project and put it in a container.
Mmmmmmmm almost crispy bacon.