The Freshening Part 3

Parts have arrived, the week has been booked off, so let's get things moving for real. We'll start by yeeting the HRV up my shiny new attic ladder.

But because this will be a long post, not until after the break. Click through to continue reading.

Feet Pics

In a previous blog post I introduced the function generator that I recently picked up. Having been formerly used in a rack mount setup, it didn't have any feet, and so was sitting directly on its bare chassis on the overhead shelf of my workbench.

This isn't especially ideal given that there's cooling vents on the bottom of the unit, so I ordered up some feet to lift it back up to its proper height.

They just snap into the trio of holes on the bottom of the unit.

And now the function generator is sitting much nicer on the shelf with plenty of air space underneath.

I'm still contemplating one other upgrade for this unit, but that will have to wait for a future blog post, depending on how things work out.

The Freshening Part 2

If I'm going to bring fresh air into my house, I want it to be actually fresh, and that means I'll be filtering out all the pollen and pollution that tends to be mixed with the outside air. To do this, I'll need a filter and, more importantly, a plenum to install the filter into.

So it's back to the sheet metal grind to use up the other ~3/4 of the metal I cut up last week. A basic box is a good place to start.

As we can see this is sized precisely to fit a 12x20x1 filter diagonally inside the 1 inch flange. Coincidentally, the size of plenum needed for this fit is 12x20.

Go figure.

Anyway, the removable fingers of the box and pan brake are really coming in handy here, especially when it comes to the double-fold on the door panel.

It's actually going to fit folded side out to the front of the plenum so that the flat panel sits up against the side of the filter, otherwise the air would just blow right around it through the gap.

And we can also see the rails in this picture that the filter will slide into.

Those rails get riveted to a set of corner panels, and a pair of braces goes lengthwise between them to support the filter and block the air from going around the edges.

And the whole assembly will look roughly like this.

But that's going to need a lot of rivets, so before we get there let's take a quick newt break.

And refreshed from that, I'll add the cross breaks to the panels. I had initially contemplated not adding them as some of the panels were slightly too large to fit into my brake diagonally, but in the end I decided to go for it and employed the other method for adding cross breaks: using a window screen roller.

Which works surprisingly well, all things considered.

Then, about a hundred rivets later, everything is secured together nicely.

Was it actually 100? I don't know, feel free to count up the stems and let me know.

I do still need to attach the door to the plenum. I already have the hinges and latches, but I want to get the weather stripping first so I can space things out correctly.

Noise No More

An achilles heel of the Casio CZ-101 (and the electrically identical CZ-1000) is the amount of noise and interference it produces on its headphone port, which is curiously not present on the line out port. In this video I explain why it happens and present a fix that dramatically reduces the noise by just swapping the values of a few passive components.

This fix really improves the usability of this synth, and it's honestly kind of embarrassing that Casio let this system out the door with such a boneheaded design fault.

The Freshening Part 1

This week I have embarked on the final house project of the winter season: adding an ERV to my house. For those of you unfamiliar, an ERV is kind of like an exhaust fan for stale inside air, but it also brings in an equal amount of fresh air and exchanges the heat and humidity between them so you don't waste all your energy by venting nicely conditioned air into the great outdoors.

To start this off, I'm going to do a little prep work before the main event happens a little later this month, starting with making some ductwork accessories. To make those, of course, I'm going to need some sheet metal.

I originally intended to just get a 4ft by 4ft sheet, as I'd managed to lay out everything to fit, but I figured I'd rather not make two trips just in case I messed up, and I'll have another use for the rest later, so I went 4x8.

And by "lay out everything to fit", I really mean "to fit".

So let's get these parts cut out, which starts by getting the sheet marked up. I've tried a number of products that are supposed to mark well on sheet metal, but so far they've all failed miserably. Instead of all that rot, I'm going to scribe the marks using a utility knife.

First, though, I figure out where to scribe it.

Holding a steel ruler down with these welding magnets works surprisingly well.

Then comes the scribing.

This leaves a surprisingly visible and very accurate mark, and as a bonus the shears seem to naturally follow the score line, making cutting straight a breeze.

I do quite enjoy these offset shears.

They make quick work of these cuts, though admittedly at the cost of a bit of a forearm workout. But an hour or two later, everything is chopped up and I didn't need to stray into the other half of the sheet.

In the meantime the ERV showed up, but unfortunately it looks like it was shipped through a war zone.

This corner was bashed in far enough to jam one of the fans, and the collar on the other side was pretty solidly dented.

And oh wait, I guess it was shipped through a war zone.

Well anyway, they're sending out a replacement for free which should be here on Monday, so hopefully this one won't be bombarded by Putin's airstrikes.

In the meantime, let's take a little reservoir break before getting back to work.

Now that's refreshing!

So the first thing on the menu is going to be a ceiling duct boot, 10"x10" nominal (9-7/8" actual so it fits in a 10"x10" hole). The sides are going to be the most complicated part to cut and bend, so I'll call on the services of Bender Bending Rodrigues to help me out.

There's both box bends and some counter-bent flanges to deal with, and luckily a box-and-pan brake has features to accommodate both.

The main 1" flange here is to join to the top of the box, while the 1/4" counter-bent flange is just to stiffen up the edges and seat more nicely against the ceiling. The movable bending teeth give the main flange a place to go when this side bend is folded up, while the notch in the bed and bending leaf gives the counter-bent flange some clearance.

The two side pieces come together like this, and then we put a few break-bends in the top for reinforcement and pop it into place with some clecos to check how things are looking.

And next come the rivets to secure everything together without leaving those stabby sheet metal screw points on the inside.

Fun fact: if you don't deliberately rock the rivet gun backwards after each shot, it can jam up with rivet stems and then you have to pull everything apart to clear out the jam.

Anyway, I need two of these so it's second verse same as the first.

And that's the boots done. I'll cut the 5 inch holes for the collars later when I actually have the collars to verify the measurements. These will be going into my bathroom ceilings to replace the loud and obnoxious exhaust fans, which is why I chose to make them 10"x10". (One of the fans is unfortunately 12"x12" so I'll have to do some drywall work to patch around it, but there was no way to get a 12"x12" boot out of the sheet metal I got without cutting into the remaining 4x4 sheet, so I figured I'd go for consistency).

So that's the first prep week's work done, but there's plenty more to come so stay tuned for that.

Generating Functions

Ok it's not actually generating functions, but instead a function generator.

I picked up an HP 8904A off of FleaBay because I really don't like my cheap Chinese function generator. The latter has a shitty UI, and despite having two channels it's incapable of modulating one with the other. It does have outputs on the front, though, which this one curiously lacks.

But if we peek around back, there they are.

Routing the IO on the back of an instrument is quite common in rack mounted setups where you arrange a bunch of instruments in a fixed configuration, but for more ad-hoc usage it's really a pain. Luckily, the connectors are just routed inside pretty simply with a pair of coax leads.

So it's just a matter of unscrewing them from the back and screwing them in at the front.

And of course we'll transfer the blanking plugs to the rear, though I had to heat them up with my hot air station to get the little plastic catches to stretch back into place after decades of being compressed.

But with everything back together, we get a lovely 1kHz sine wave at 1v peak-to-peak.

Which is, of course, configurable for amplitude, frequency, and so on, as are the many other wave shapes it can generate.

What we don't get, though, is modulation. You see, that's an option that you have to pay HP to enable, and whoever owned this instrument in the past never paid HP to enable it, which means the HP tech never came out and pressed the power button (on), shift, service, shift, f4, 092448, shift, service, next, next, next, f1, 3ffc, f2, ff, f4, f4, power button (off), which would have allowed the instrument to perform amplitude modulation like this.

Or frequency modulation like this.

Or many other types of more complex modulations.

What a shame, I guess I'll have to just live without.

Carbonation

I've had a nonstick Ikea frying pan for ages now, and it's been serving me well. It's quite large though, and this makes things awkward when I want to make myself an omelette since having too much space just lets the egg spread out too thin. So it was about time I bought myself a smaller pan.

Since everyone is freaking out about PFAS these days I decided to go with carbon steel. It's basically identical in function to cast iron, but much thinner and lighter. As such, it needs seasoning.

I decided to use salad-grade olive oil for this task, just to trigger all the seasoning fetishists out there.

After things start to get smoky, the excess is poured off so that the remainder can form a nice thin layer and polymerize onto the surface of the pan. I actually left just a teensy bit too much in here though, which made the seasoning slightly too thick in a few spots.

This lead to the seasoning getting a bit bubbly in these spots, which is not ideal. The thick spots also have a tendency to flake off. It's not a big deal though, and 95% of the seasoning is perfectly solid.

I sanded down some of the lumpy spots and gave it a second blast of seasoning.

And then I cooked myself an omelette.

And the pan came out unscathed, with just a few small spots being a bit sticky.

But those spots will season up over time.

All in all, I'm quite pleased with this pan. It seems to be just the right size for a 2 egg omelette, which is exactly what I intend to use it for.