The solar panel needs to be used with a charge controller. Connecting it directly to a battery will overcharge and damage the battery. Charge controllers typically don’t like the battery being disconnected while the solar panel is still connected, so don’t connect it to a switched outlet.

A power supply is something that a lot of hobbyists will build themselves. It’s very easy to build one with an LM317.

I’ve seen a lot of single board computers with removable eMMC memory. Many of the Orange Pi boards have eMMC modules.

A .22lr fits in some 3AG fuse holders. They do produce an audible alert when they blow. I’m not sure what the current rating is though.

That’s a lot to fit in a watch. The PCB layout will be difficult and the requirements for it will likely exceed what the usual prototype PCB manufacturers can produce.

The RP2040 is a power hog. It takes 180µA in its lowest power sleep mode. There are other microcontrollers that can be in run mode and use less power than a sleeping RP2040. I would suggest looking into some of the STM32L series microcontrollers. They can get down into the nanoamp range in sleep mode and run less than 100µA/MHz.

You will have a hard enough time just finding a SOC that you can get documentation for without signing and NDA and promising to buy massive quantities of them.

You can put a thin, soft cloth on the keyboard when closing the lid. On many of the super slim laptops, the screen can touch the keyboard when closed. That eventually leaves permanent rub marks on the screen.

Fans and vents should be blown out occasionally. Hold the fan blades still when blowing them out. Spinning them up to high speed with compressed air can damage them. If you have pets, you will need to clean the hair out more frequently.

A cooling pad can help if it gets excessively hot, but often just propping up the back so it can get more air flow will help out a lot.

Only having one ADC can be an issue when you need readings to be in phase, but for reading any sort of human interface device it doesn’t matter at all. Just cycle through your inputs one at a time. Some microcontrollers even have hardware to scan through multiple inputs automatically. You can use DMA to read the ADC and send data out over whatever communication peripherals your microcontroller has without using much CPU time.

If you are using USB HID, you are limited to a 1000 Hz update rate and that’s really overkill already. You can have up to 8 analog axis in a USB HID game controller plus lots of buttons.

There are simple testers like this. It’s rather overpriced for what it is, but it would be trivial to make one yourself. That will only do a continuity check though. If you want to know what the current or speed ratings are, you will need to read the chip in the cable.

The MOSFETs are in series, but in opposite polarities. Two MOSFETs are needed to block current in both directions.

The DW01 uses the voltage drop across the MOSFETS to measure the current. The overcurrent threshold voltage is fixed at 150mV. Using a larger MOSFET that has a lower RDS(on) will increase the current limit.

The drains in the 8205 MOSFET are connected together internally. In a DW01 circuit, they are not connected to anything else.
One MOSFET stops the battery from charging and the other stops it from discharging.

For something that’s not switching at a high frequency, slow rise and fall times are fine as long as you are staying within the safe operating area of your MOSFET. A 10K gate resistor could certainly work, but it will depend on your MOSFET and load.

MELF stands for Metal Electrode Leadless Face although anyone who has had the pleasure of working with them will tell you it stands for Most End up Lying on the Floor.

No, there’s no fuse here. From top to bottom, there is an electrolytic capacitor, zener diode, and a 4MHz resonator.

The flash chip is a common 16 MiB SPI NOR flash. An easy way to read or write it would be to use flashrom on a single board computer like a Raspberry Pi.

Unfortunately, that router is not supported by OpenWrt or DD-WRT, so you probably won’t be able to do much with it.

No, moving a ferrite core through a coil won’t generate a voltage. You would need to move a magnet to generate a voltage.

Look for a vibration switch like one of these. If you want more control, you could use an accelerometer and a microcontroller to trigger it from a specific amount of movement.

You might be able to increase the voltage 10-20% by changing the feedback, but you will not be able to double it without changing the transformer.

Try adding a large, low ESR capacitor across the power rails on your board. Preferably a polymer electrolytic if you have some.

You can get small project enclosures to put them in. Some PVC pipe and end caps could also work.
I would probably just use some good quality, adhesive heat shrink if they are out of the way though.

I’ve had good results discharging a 450V 1kJ capacitor bank through several turns of 10 AWG wire. If you don’t have a capacitor bank laying around, one of those magnetizers will work just as well.