Let's safely disassemble this one I found abandoned at the side of the road and harvest anything useful.

⚠️ Safety warning

Taking apart a microwave can be dangerous. These operate at very high voltages and you should never attempt to repair or disassemble one while it's plugged in or switched on.

Even after it's been unplugged, some components inside can still store a potentially lethal charge, while others, like the ceramic insulators on the magnetron, can be hazardous if crushed or damaged.

If at any point you feel uncomfortable, stop and do another project. It's just not worth the risk!

What's inside?

The first step is to remove all of the screws around the outside holding the outer casing in place - you’ll likely need some Torx security bits for a few of these. Once these are gone the casing should just lift straight off to reveal the internal components.

The exact layout might vary slightly depending on the make and model, but all microwaves have the same fundamental parts:

• Microwave Oven Transformer (MOT)
• High voltage capacitor
• Cooling fan
• Magnetron
• Main PCB

Discharging the capacitor

Before doing anything else, we need to discharge that capacitor. These can store thousands of volts in them even after the microwave’s been unplugged, enough to stop your heart. Modern capacitors often include an internal resistor that’s designed to safely discharge them over time, but these can fail, so you should always assume that the capacitor is charged until confirmed otherwise.

The safest way to do this is with a suitable high power resistor to short the capacitor in a more controlled manner. But if you don’t have one of these, you can take a pair of pliers that are well insulated, and bridge the two contacts together for a short amount of time. It’s best to do this while the capacitor is still in place if you can, and whilst wearing thick insulating gloves.

Be prepared to see a flash or hear a pop if there’s still a charge - again it’s better to do this in a more controlled manner if possible, as this can damage both the capacitor and the tool you’re using.

Once it’s discharged, it can be safely removed it from the microwave.

Magnetron myth-busting

Next let’s turn to the magnetron. This is what generates the microwaves that cook your food, though there’s no risk of radiation now it’s powered off. Carefully unscrew this from its housing and remove it.

It’s a common myth that the white or pink ceramic insulators at the side of the magnetron are made from beryllium oxide, which is extremely harmful if crushed as the dust is carcinogenic and can lead to an incurable lung disease if inhaled.

Unless the microwave is very old, this is far more likely to be made of the cheaper, less dangerous aluminium oxide instead. The pink colour just indicates it’s been doped with chromium oxide, which makes the ceramic pink for the same reason rubies are red!

That being said, neither material is good for your health if you breathe it in; so like the capacitor, treat this with respect, and never cut or damage it.

Dismantling the magnetron

Providing you're confident you won't damage the ceramic material, the magnetron contains two large magnets inside that can be salvaged. These aren’t as powerful as neodymium magnets, but they are quite strong.

The top plate can be levered free with a pair of pliers and a large flat-head screwdriver. From there you can remove the top magnet, which might take a bit of force.

Then you can do the same at the other side: lever apart the bottom plate, cut the tube free, and then you can remove it from its housing and get to the bottom magnet.

Again, be careful when you do this, as you don’t want to damage the ceramic insulator.

Removing everything else

Now we can safely take the rest of the microwave apart. The most valuable piece we can salvage is the high voltage transformer inside, which will probably be near the bottom as it’s very heavy.

These can often be reused in projects that require high current, such as homemade spot welders. The original high-voltage winding is replaced with a low-voltage, high-current one. Or they can be simply sold for scrap.

After that it’s just a case of going through and unscrewing everything left and removing the parts. Don’t forget to flip the microwave over and remove the turntable motor at the bottom, this can be reused or stripped apart for the coil inside.

Once finished you should have an array of parts you can reuse in other projects.

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Parts

Most of the parts you need can be salvaged from junk electronics or bought cheaply online.

• An old computer mouse
• 2 1.5V DC motors
• Wire
• Paperclips
• 2 AAA batteries
• AAA battery holder

Optional:

• Craft wire
• Switch

Step 1: Disassemble the Mouse

The first step is to take the mouse apart so you can use it as its body. You don’t have to use a mouse for this, you could simply use the battery holder as its body or anything else you can scavenge.

Step 2: Mount the Switches

Next, cut out a space at the front to mount the switches. They should be positioned at an angle, with the two NC contacts closest together. They need to be able to take a knock, so secure them in place with some hot glue.

When a switch is triggered, it reverses the motor’s direction.

Step 3: Attach the Motors

Now make some holes either side for the motors. The angle of the motors is up to you, but the more spread out they are, the faster the robot will move.

Once you’re happy with the angle, fix them in place with some more hot glue.

You could also put a little dab on the end of the motor shaft to give it some grip, or use some heat shrink tubing.

Step 4: Fit the Batteries

Fit the battery holder in place with some hot glue. If there's no room for a battery holder you could use some battery contacts on their own instead - or experiment with two 9V batteries if you’re feeling adventurous!

Step 5: (Optional) Add a Rear Wheel

To stop the back from dragging, your robot might need a rear wheel. I fashioned one from the scroll wheel that came with the mouse and some metal tubes I found in my parts bin.

I wanted to reuse as much of the mouse as possible, but this could be as simple as a paperclip with a small bead inside, hot-glued to the back of the body.

Step 6: Wire It Up

Start by soldering the the two NC contacts together on the switches, then take a piece of wire or paperclip and solder the two NO connections together as well.

Then solder the [+] tag of one motor to the remaining C connection on the switch, and do the same with the [-] connector of the other motor to the other switch. If you want to add a power switch, these are the two connections you need to interrupt.

Now connect the remaining motor tags together using a wire across the middle.

Solder a wire from the positive output of the batteries to the NC connection on the switches. Then connect the negative output to the NO contacts soldered together earlier.

The final connection is the third wire from the battery holder, connected to the shared positive/negative end. Connect this wire to the joined motor tags.

Step 7: Add Whiskers

To trigger the switches reliably, we need to give the robot some whiskers. Bend some paperclips or craft wire into shape, and attach them to the switches with solder or spade connectors for something more robust.

Step 8: Test It Out!

Now everything's in place you can insert some batteries and test it out. It should scoot along pretty quickly and be able to avoid obstacles you put in its way.

If it’s not moving fast enough, try adjusting the angle of the motors and make sure you’re using fresh batteries.

Step 9: (Optional) Add a Switch

To finish off, you could add a switch to so you don’t have to keep removing the batteries to turn it off.

To disable the robot completely, we need to interrupt the connections to both motors using a DPDT switch, between the motor tag and C terminal on each side (see schematic in step 6).

A SPDT switch on the shared battery contact will stop it from moving forwards, but the motors will still activate in reverse when a switch is triggered - good enough if left on a desk, but if something accidentally triggers a switch, it will shoot backwards.

By tracing out the circuit we can see why this is the case. Only one battery is used to power both motors for each direction, and when one side is in reverse, both batteries are in use.

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Tidying it up

Before I could do anything, I needed turn my setup into something more permanent. I housed the buck converter and USB PD trigger board in a cheap plastic project box and fed the wires through a hole drilled through the back of the phone.

Being a budget phone, the back cover is plastic and there are no magnets or wireless charging coils in the way.

At this point I also added a Schottky diode to the output of the buck converter; that way I can still use the Pixel's USB port for data access without the worry of it attempting to charge the buck converter. A 1N5822 would be ideal, but as I only had a 1N5819 in stock I used that instead.

Optimising the software

I could put this to use straight away, but I wanted to turn my attention to the software. If this is going to be left running 24/7, I want it to draw as little power as possible. Phone's are already very power-efficient, but I could do without any of the apps and background services running that I no longer need.

The easiest way to debloat my phone was to install a custom ROM. I went with LineageOS, which is designed to be clean and customisable. I also rooted the phone with Magisk, which will allow me to customise things further, should I need it.

Once installed I went through and disabled all of the apps and services I don't need. I also installed a firewall to block access to the internet by default, but allow something like a weather widget through should it need it.

I also disabled cosmetic things like the navigation bar and battery indicator too.

Wait, why is the battery level dropping?

Curiously, despite the voltage staying constant, Android gets a little confused and still reports the battery level dropping. Why is this, if this setup can power it indefinitely?

It seems the way Android calculates battery life is quite simple - it measures the rate of discharge and subtracts it from its pre-programmed battery capacity. It takes battery voltage into account when it boots up to get an initial reading, then either doesn't realise or doesn't care that it stays constant and doesn't tally up with its calculations.

In my experience it seems to drop to 1% and doesn’t cause the phone to shut down, but this may vary depending on the manufacturer.

Energy usage

I was curious as to how much power this is drawing after my modifications, so I used a charger doctor to measure the current flowing. It jumps around a lot, but at 50% brightness it draws well under 1W at idle - not bad!

At current UK prices of electricity, this would cost a little over £2 a year to run if kept on 24/7.

Designing the setup

Now it’s ready to be put to use, I set about designing my setup. I took inspiration from the new-ish standby mode on iOS devices - I could put a lot of information on here, but I want something simple and readable at a glance.

I waded through a lot of junk on the Play Store, but in the end I used Nova Launcher, and this selection of widgets:

• Analog Scribble Clock Widget
• Event Flow Calendar Widget
• KWGT Kustom Widget Maker
• Today Weather: Radar & Alerts

Result

After some tweaking, I was quite happy with the result! Set on a stand from AliExpress, I think it looks quite nice, and I have a couple of designs to choose from.

I can still pick it up and use it as a timelapse camera, or any other idea that may come to me in the future.

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There’s one problem: unless you like a spicy pillow, leaving an old phone plugged in 24/7 probably isn’t the greatest idea. The battery on this phone has nearly 2400 cycles on it and would have died by the time you finish reading this sentence; I don’t trust it. Let’s see if we can remove it and power it straight from USB.

Disassembly

The first step is to disassemble the phone, which I found surprisingly easy. The iFixit guide I followed rates it as “difficult”, but if you have some experience taking things apart then you should be fine. With the phone being so old, the glue around the screen had dried up and was easy to remove without any additional heat.

Heat wasn’t required to remove the battery either, as Google in their mercy used two stretch-release adhesive strips to hold it in place. Give these a pull and the battery should come free.

Sorry, "should" come free. In practice, I found these quite fragile and I ended up snapping one of them. It took quite a while and a lot of force to pry the battery away afterwards. Given how many cycles are on this battery (and the force needed to remove it) I was quite surprised to find it in physically such a good condition, there was no sign of swelling at all.

At this point I reassembled everything and tried plugging in a charger to see if it’d boot straight from that. As I expected, there was no sign of life. A long shot, but worth a try.

Planning

The battery consists of two parts: the bare cell; and a long, thin circuit board that protects and monitors it. This board expects to see a voltage roughly between 3V to 4.2V depending on the state of charge. By removing the cell and supplying my own power source within this range, I should be able to get the phone to boot.

My original plan was to use a cheap USB cable to provide 5V and drop it down using a buck converter that was small enough to fit in the void left by the missing battery, but I wasn’t convinced that would be able to provide enough power to the phone. When under heavy loads, a phone can draw bursts of current very quickly, something a lithium battery can happily handle.

Then I remembered a feature made popular with USB-C: Power Delivery, a universal standard that allows devices to negotiate the exact amount of power needed (as long as the supply can provide it).

I used a USB Power Delivery trigger module to request 9V from a compatible supply, and fed that to a beefy buck converter (XL4015) that should be able to sustain up to 3A comfortably, with spikes up to 5A.

The Power Delivery board might not be strictly necessary, but a higher voltage will give the buck converter some more headroom, and it provides a convenient USB-C port to plug into.

Result

Back at the workbench I soldered everything together and plugged it into my power bank.

It works! The phone boots without an issue, seems quite happy under load too.

One thing I did have to do was add an extra wire from the negative tag of the battery PCB and ground it to the chassis of the phone (in this case I tucked it under the screw holding the USB-C port in place). I'm not sure why this was necessary, but without it, the phone wouldn't boot.

I also noticed that although I’m supplying a constant voltage that could theoretically power this indefinitely, Android is a little confused and still reports the battery level dropping. Thankfully this stops at 1% and doesn’t seem to cause it to shut down. Phew!

Now to find a use for it! This would make a good timelapse camera, security monitor, digital photo frame - we’ll see…

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No doubt one of the easiest ways to do this is by using the lost wax method: a process that involves making a wax model of the desired object, encasing it in a material such as clay, plaster, or silicone, and then melting out the wax to leave a hollow shape into which the metal - usually pewter - can be poured.

Making the model

Naturally, consuming a lot of cheese is the first step in this process. Not only does this put you in a good mood for the long, tedious process of forming your model, the outer wax provides the perfect material to work with.

I found it useful to allow the wax to cool for a while in the fridge if it was getting too soft from the heat of my hands, and to use toothpicks to help with some of the fine details.

An unhealthy amount of Babybels later, I was able to make this little model rabbit.

The cone shape at the bottom is called as a sprue. This is necessary to produce a channel in the mould through which to pour in the metal (remember the cavity will be a negative of this shape), and also acts as a reservoir of extra metal while the casting cools and potentially contracts.

Mixing the mould

For the mould itself I used a high-temperature two-part silicone that's designed for use with metal casting. Although a bit pricey compared to plaster or clay, it sets much faster and can be reused multiple times. As I don't have a vacuum chamber, I had to take extra care when mixing to introduce as little bubbles as possible.

I found a suitable container to pour this into (the sacrifices I have to make for this project), taking care to avoid introducing air bubbles by pouring slowly in a single stream into a corner, rather than directly over the wax model inside.

By the morning the silicone had fully cured and I could start removing the wax. Traditionally this would be melted out in a low-temperature oven, but instead I cut the mould open in a zig-zag pattern and removed it by hand. Because the silicone is semi-flexible, the two parts fitted back together easily afterwards. It also meant I wouldn’t need to cut the mould open again later to remove the finished casting and risk scratching it in the process.

Casting

With the wax removed and the mould firmly taped back together, I broke out my portable gas stove and melted down a cheap pewter tankard I found in a charity shop.

Modern pewter is an alloy made of tin and small amounts of antimony and copper, but it's worth being cautious with older, unmarked pieces as they may contain lead. I did this outside and in a saucepan I don't use for, say, cheese sauce.

Pewter is often used for metal casting because of its low melting point (around 170–230°C), so melting this tankard didn't take long at all.

I quickly poured this into the mould and allowed it to cool. It was fairly well behaved, there was no bubbling or spitting, and I had plenty left over for future casts.

Within a few moments the pewter had set solid, and after dousing with cold water it was cool enough to take apart the mould and tidy up the cast.

Not bad! I cut off the sprue with a small hacksaw and glued on a small dark-purple rhinestone for each eye. It's far from perfect - the body is very rough (probably on account of bubbles in the mould) and it's missing a leg, but in a way I think this just adds to its charm.

Conclusions

I think if I were to do this again I would cast something slightly larger; making such a small model was very finicky and the pewter was too viscous to reach into the extremities of its thin legs. Perhaps adding some venting holes or pouring channels would have helped with this.

Although the silicone I used was advertised as not requiring a vacuum chamber, having one would have been very beneficial. No matter how carefully you mix the two parts together, you're bound to introduce pockets of air into the mould and cause an uneven appearance on the finished piece.

I also had a small amount of silicone leftover, which I left to set in a glass as a practical joke.

Rather effective I think!

Setup

As I didn't have a dedicated camera or any special equipment, I couldn't set up anything permanent. I simply marked out a rectangle on my window using masking tape and placed my phone within it every day to take a picture.

Very quickly I realised this was a stupid idea; even if I managed to align it perfectly each day, my phone's camera was always making tiny adjustments to stabilise the image. Granted, they were only slightly off - but when compounded 365 times, I began to wonder if I was even in the same room when I took some of the photos.

Still, I had already started by this point, so I resigned myself to fixing it in post.

Editing

Towards the end of the year, I opened up Affinity Designer and began the arduous process of aligning the photos. This was something I wish I'd done as I went along, I now had hundreds of them that all needed to be manually straightened, cropped, and aligned.

Once I got them reasonably consistent, I stitched them all together in iMovie to make my timelapse.

When played back at high speed the pictures still looked woefully uneven, so I used iMovie's built-in stabilisation feature which was just good enough to finish the job.

Result

Below is the finished timelapse, although I missed 37 days. Seeing things sped-up is always fascinating, there are so many details we miss living in real-time!

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After many years, I finally got my wish.

Lying at the side of a road was a beautiful speckled wood butterfly - and in reasonably good condition too, considering it had definitely kicked the bucket.

Unfortunately, I was out walking and a long way from home, cars, civilisation, or anything else that might spare it from hitching a ride back for several miles in my sweaty, cupped palms. I received more than a few odd looks from passersby.

Once I got home and got over my initial excitement, I realised I was surprisingly clueless about what to do next, given how many years I've wanted to do this. I had none of the equipment or materials to frame it and hang it on my wall immediately, so I needed a way to preserve it whilst I did some research.

Thankfully, this is quite simple. You can simply place the specimen in the freezer for as long as required. In fact, this has the added bonus of killing any pests and mould spores.

Preparation

To pin the butterfly, it first needs to be in a relaxed, pliable state. Once it dies, the body stiffens and the wings can no longer be moved into position without risking damage.

I placed it in a sealed container with a moistened paper towel (using equal parts water and isopropyl alcohol to prevent mould growth) and left it for 48 hours. The moisture from the paper towel creates a humid environment that softens the wings and make them pliable.

Before moving on, I checked its progress by gently moving one of the antennae. Once it can be moved with ease, the butterfly is ready to be pinned.

Pinning

I made an improvised pinning board out of some polystyrene. The important thing is to have a groove in the centre to allow the butterfly's body to sit lower than its wings, letting them rest naturally flat.

I then secured the specimen using entomology pins, placing one carefully through the centre of its thorax (the middle section of the body between the head and abdomen).

The wings can be gently manoeuvred into position and held down with strips of tracing paper pinned to the board (not through the wings!). Tracing paper is used as it's smooth and less likely to damage its delicate scales. Most guides recommend using forceps to gently grab the top vein and pull them into place, making sure the bottom part of the forewing is perpendicular to the body.

Needless to say the wings are very delicate; I used some tweezers and foolishly tore the top part of the wing. I was more careful with the hindwings, and adjusted the body and antennae so they sat straight.

Once finished, I left it undisturbed for a few days to dry and then removed the pins and tracing paper.

Framing

To display the butterfly I used a simple 3D box frame and made a small identification label to go with it, showing the common name, species name, and date collected.

To secure it to the back of the frame I cut a thin rectangular piece from a hot glue stick and superglued it to the butterfly's body, then fixed the other side to the frame backing. I'm sure lots of things could be used for this, but the glue stick was easy to cut into shape and conveniently transparent.

Kept like this in a dry environment and away from direct sunlight, the butterfly can last for centuries!

Update - 28/10/24

I knew it, I just knew I shouldn't have ended a post like that. I'd forgotton to account for Sod's law: after a couple of years, there's a fluffy white mould growing on my butterfly.

I wiped off as much as I could with a paintbrush, then sealed the whole thing in a bag and placed it in the freezer for 48 hours to kill the spores.

Thankfully, that seems to have done the trick. I lined the bottom of the frame with packets of silica gel and diligently sealed the back with duct tape to hopefully prevent it from returning.