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It is weird to recall that at one point I was actively collecting vintage computers, with one goal to have an example of every Apple computer. Over time my enthusian waned and I downsized the collection, in conjunction with looking to buy a house.

Then for over a decade the remaining items sat untouched at my parent’s (with only the occasional prompt to do something about them) until the middle of 2013 when I brought over of the Apple IIgs related items. This was my childhood computer and my first step in getting it running again was to replace the power supply with something modern. I tinkered with this for a while, getting a GBS-8220 for converting the display output and picking up a CFFA3000 for more convenient drive emulation.

Skip forward to the middle of 2024 and I set myself the goal of sorting through what was left of the collection and having it all gone from my parents house by the end of the year.

That goal has been achieved three months early.

I would have liked to gift items to people that I know would use it (this is what I am doing with one system) but I decided to to see how things would go in eBay, in one sense returning the items back to where I got them from. I started with a few of the smaller items that could be easily posted then progressing to the heaver items. As I was more interested in finding homes that in making money I started almost all the listings at $9.99, some sold for that starting price while others went for quite a lot more.

It was good to see that there were a variety of people bidding, some I could see also had ebay stores so would be buying to flip, while others (mainly those that I spoke to when they collected items in person) were actually interested in collecting and restoring vintage computers.

I am not going to update my computer collection pages, but because I took updated photos for the ebay listings, I have put those photos up in an album on Flickr: Vintage Apple for eBay.

Going through these images one last time did make me feel nostalgic, but only for the act of collecting. Better that they are in the hands of people that wanted them enough to bid for them, instead of just taking up space…

A month ago I was able to compare four months of usage between last year and this year. I have received my electricity bill for August which means I can extend that comparison out to six months.

The numbers from 2023:

Gas:

Electricity:

For this six month period in 2023 my total energy cost was $2,078.65.

Then for 2024:

Gas:

Electricity:

These two additional months are the middle of winter so the usage is what I expected, but you cannot argue that $449.31 is a lot less than $2,078.65

I also was able to update my view of my consumption:

Something I noticed with the additional data is that for July I both consumed more electricity and my solar generated less, this aligns with it being a cold and dark month. August had more than normal sunny and warm days, which can be seen in lower comsumption and higher solar generation.

This is all I have to say about this update, I think the next update I give with this amount of detail will be at the end of year when I will be able to see how the numbers go over spring and the start of summer.

Although I should wait until I have a full year’s worth of usage data (or possibly wait for multiple year’s worth) I realised that I could make a comparison of the last four months against the same four months last year. Why four months? Because that is a period of time since my solar was fully set up and that aligns with the two monthly cycle for the gas bills.

Let’s start with some numbers from 2023:

Gas:

Electricity:

This means that for this four month period in 2023 my total energy cost was $1200.95. (it is a coincidence that this is almost a round number…)

So how about 2024:

Gas:

Electricity:

So the total amount I was charged for these four months in 2024 was $258.86. This is a lot less than the same period in 2023, around 80% less which is quite nice.

However this is only one perspective of my usage, the amount of energy fed in or out as seen by the smart meter. How much energy am I consuming? For that I can go to the monitoring for my solar panels:

The first thing that I noticed was that the Enphase Envoy is consistently measuring values that are about 10% lower than what my smart meter is measuring. For the purposes of this comparison I have adjusted the Enphase consumption value up by 10%.

This has given a result I did not quite expect.

• When I had gas heating and resistive hot water in 2023, my electricity consumption for these four months was 1896kWh.
• Then in 2024 with heat pumps for heating/cooling rooms and heating hot water, the electricity consumption for the four months was 1561kWh.

So even without taking into account the gas usage, I am now using 335kWh less electricity? This is a good overall result.

I also need to ask, what would I have paid if had only changed the heating and hot water? The daily charge would have remained and if I assume the same 22.6c/kWh rate my overall bill would have been $483.50. This is only slightly lower than what I had paid for electricity in 2023, so not having a $738 for gas really stands out, and based on how the gas rates were increasing, that would have been nearer $1000 in 2024.

I think I could make the following conclusions:

1. Switching away from gas is worth it and gives the biggest difference of not having that $738 bill, even if you only take into account the financial aspect
2. Adding solar panels gives a decent financial benefit, in this case reducing the cost by half from $483 to $258.
3. Moving to heat pump for hot water gave a smaller, my previous estimates were that it halved the electricity needed, so from $100 to $50 for the four months

I did mention that gas prices were already going up, and my electricity rate increased at the start of August from 22.6c/kWh to 27.7c/kWh. This is combined with my feed-in rate already dropping from 5.4c/kWh to 5.0c/kWh at the start of July. I need to think about more/better ways to self-consume my solar generation, and if this trend continues I might consider batteries sooner than later…

Ever since I first heard about 3D printers I was intrigued, but not interested enough to delve into that low level of hardware tinkering. Over the years I have noticed that they have shifted from being a project in themselves, to being a tool to use for other projects. However it is only in the last six months or so that I have seriously considered getting one as a way to improve my home automation projects.

Every two weeks at work we have someone give a presentation on something that interests them, it does not have to be work related so there have been all sorts of talks. Earlier in the year I gave an update on my home automation, but last Friday the topic was how to get started with 3D printing.

That night I placed an order, the printer arrived on Thursday and within an hour I had my first Benchy:

In that talk and other places (blog posts, youtube videos) there were essentially two brands to get started with: Creality or Bambu Lab

At first I was leaning towards a Creality Ender-3 as I liked the open source design and the flexibility that would give. However the large number of different models was a bit overwhelming and while I could tinker with the setup and software, I was leaning towards wanting the printer to be a tool…

This means that despite the closed source design and the default printing flow using a cloud service, I opted for their cheapest and smallest option which is the Bambu Lab A1 mini. The print bed might be small, but it should be big enough for anything I have planned (brackets to mount sensors, small cases for projects) and I did not get the AMS as I do not plan to print in multiple colours (and that almost doubled the price…).

In the end I paid $428 to get the printer and three spools of filament. Obviously this is a price I was happy with, now that the printer has arrived I appreciate how compact it is and how it fits down the end of my desk.

So far I have played around with printing a few widgets from designs available online:

I have only encountered two issues while printing these, one maintenance and one design.

For the later prints I found that the print would fail to adhere to the plate and a blob of plastic would form around the print head as it continued to print further away from the print bed. I have only been using one side of the plate and I have not cleaned it. So the solution might be as simple as following the instructions to clean the plate using dish soap and a microfibre cloth. I should also keep an eye on the print at the beginning to make sure it starts ok.

The design issue is that when the prints complete the print head is raised up away from the print, but due to how the filament tube is mounted this also draws filament off the spool. Then once the next print starts the is excess slack in the filament and it has been slipping off the side, then later jamming. One of the suggested mods I have seen is to print a handle that also doubles as a spool relocation. With the spool up higher the filament tube is in a different location that does not move with the print head, so it would not cause this excess slack. I don’t know if I will do this, or if I will try to remember to check that the filament will come off the spool ok.

My next step is to start learning how to design objects to print, with my first project being brackets to mount microswitches to the track of my garage door opener. I have had the software side of that ready for a long long time, but I was stuck at attaching the hardware.

Over the last week I also designed and ordered my first custom PCB (more on that later), these two techniques open up a number of possibilities…

Today is the winter solstice and over the last few days it has been quite clear that winter has set in in Melbourne with headlines such as “Melbourne shivers through coldest winter day in four years…” so it seems appropriate I give some updates on how my solar, AC and heat pump hot water system are going.

A big question I asked myself was whether I made a mistake in getting my gas disconnected. Previously I would have the central heating on a schedule that I didn’t think about and my entire house would be warm at the times that I was awake. The AC units in my study (during the day while I am working and then in the evening) and bedroom (a bit in the morning for when I wake up and then a bit in the evening before I go to sleep) do a good job if I close the doors to those rooms, which means the other rooms (kitchen, bathroom, lounge) are cold.

It isn’t actually that bad, but it is noticeable when I move from room to room. Thanks to my monitoring I could also track that when I was in my study that the CO₂ would climb to 1500ppm and at times I do feel a bit sluggish. My mitigation so far has been to get up every hour and go get a drink or go to the bathroom, this lets enough fresh air in to drop the CO₂ down to around 600ppm from where it will start to climb again. The alternative is to leave the door open (like I used to do) but then the AC unit is trying to heat my entire house which is not efficient.

With the shorter and cloudier days there has been a noticeable drop in how much my solar panels are generating. At the peak of summer they would generate almost 30kWh over the day, but the best I have seen recently is 17kWh on a day that was sunny all day, but that is the difference between 13 hours of sun high in the sky versus about 8 hours of sun that is lower. Though even on a day that rained all the way through the panels managed to produce around 3kWh which was about a third of my consumption for that day.

I could also notice a pattern of the solar generation being best in the early afternoon, the day would start out cloudy and the clear up for a bit. To better take advantage of this I changed the schedule on my heat pump hot water from 10am to 1pm with the intent to run it both from solar that I am generating and also to be in a warmer part of the day so it should run a bit more efficiently. I don’t have a way to actually measure this, but it seems like the right thing to do. What I can also see is that where it would run for just over an hour when the ambient temperature was above 20°C, but now when the ambient temperature is below 10°C it is running for a bit over two hours.

All of this is just the detail, what really matters is the long term so it won’t be until the start of next year that I can sit down with the data and compare 2023 with gas heating and no solar against 2024 with solar and three heat pumps…