When i saw the LM358 dual op-amp I considered that it might be for current feedback to the boost chip, but sadly it's just for the charge status LEDs and the current regulation relies entirely on whatever the chip can handle when running at full tilt, as it will not receive any feedback signal until the battery is charged and the internal protection circuitry found on these jack-charged clones, ends the charge.

Not sure what the reliability of these units will be, as they are pushing the little chip hard for potentially several hours at a time, and it gets hot fast.

They could have added just a few components to the circuitry to lower the charge current in a controlled manner by providing feedback to the boost chip. They could even have used one of the op-amps for that purpose to keep the value of the sense resistor low.

While these are novel and have their uses, I don't totally recommend them. But if you want to play around with one, then here's a link to the item on AliExpress (not a sponsor).
This is an affiliate link, but that will not affect the price you pay.
If you view this item or add it to your cart it may appear in the bundle deal section.
https://s.click.aliexpress.com/e/_c3e3na0n
Guide price around £1.50

With suitable resistor tweaking these can also be used as fixed voltage boosters for other uses.

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This unit has a couple more tricks up its sleeve though. Aside from the interesting aluminium shrouds to limit the amount of UVC light that can escape the unit, it also has a set of titanium dioxide coated baffles designed to cause air turbulence. Titanium dioxide is commonly used as a very white pigment in paints, but also has the unusual characteristic of exhibiting a photocatalytic reaction on its surface when exposed to UV light. That results in the formation of hydroxyl radicals (a molecule composed of one atom of hydrogen and one of oxygen) which is a very short lived but highly reactive molecule that reverts back to a more stable form almost instantly, but can oxidise airborne contaminants in the process. This unit also uses an unusual UVC tube that has two types of quartz/uviol glass that are spliced together. The long section only passes 254nm UVC and the short section also passes the 184nm wavelength giving a small extra output of ozone for increased effect throughout the space it's in.

It's quite odd that a unit that has been in use long enough for the tube to have failed completely, still has immaculately white titanium dioxide baffles. It may be a self-cleaning effect associated with photocatalysis.

Now for the medical stuff. Contrary to popular belief, UVC poses a low risk of skin cancer. It got that reputation because it will cause very serious surface irritation of skin and eyes. But in reality the wavelength is so short that it can't penetrate deep enough into the skin to reach the critical layers. UVA and UVB both pose a much higher risk of causing subdermal damage.

Always remember not to look at a lit UVC bulb or its reflection from shiny surfaces. It will rapidly cause surface damage to skin and eyes, leading to sunburn effects. The eyes will not react immediately, but after some time they will feel like they are filled with sand. This effect will quickly wear off depending on the exposure level. It may be possible to get anesthetic eye drops to help with the discomfort if needed. It's so unpleasant that you will not want to risk it again.

Almost every plastic and glass will block UVC light, so standard safety goggles will usually protect your eyes. You can get phosphor coated UVC test cards to check that.

Titanium dioxide has been used as a paint pigment and food colourant for a long time, but there are now concerns that nanoparticles of TiO2 (titanium dioxide) could pass through the blood-brain barrier and pose health problems in some situations. Most of the research in this area has been done on lab animals consuming the pigment, and it's not known if it poses the same risk to humans.
As a food additive (E171) it has been banned in Europe and many other countries for several years, but is still used in the UK and USA. In this application there is no significant risk as it is not being ingested.

I got this unit secondhand on eBay, and it still commanded a respectable price. This one was £45 in a well-used condition and with a dead fluorescent tube. It uses a 2G7 lamp holder, and I ended up retrofitting a different one so that it could use a cheap 9W PLS aquarium UVC tube, which lacks the ozone section.

UVC tubes gradually degrade their quartz/uviol glass over time, and although they may seem just as bright as usual, this can greatly reduce the amount of UVC light emitted. As such, they should be changed every year or 10,000 hours of use. The degradation of the quartz on this tube was visible.

Mercury vapour tubes are still the cheapest, most reliable and most efficient source of UVC light for applications like this. LED sources of UVC are not currently viable for this application.

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When I was young and got my own flat, I didn't have a television, because I was working long hours and spending all my free time writing software and building gadgets in my workshop.
Then the "letters" started coming.... Really nasty letters that implied that if I had ANYTHING at all that could receive a TV signal then I needed to pay for a licence. Then came the visits from "inspectors", who demanded access to my flat so they could search it for an unlawful TV.
(It turns out that the "inspectors" are just employees with as much right to enter your home as Ronald McDonald.)

In the end, the continuous threats and intimidation got to me and I paid for a licence even though I had no TV.

Imagine if a loan company sent a debt collector after everyone in the hope that people would be bullied into paying for a loan they never had. That's Capita. And because it's a "government thing" they seem to be unaccountable.

I've looked at one of these modules before and the circuitry is similar, but whereas I mistakenly thought that the small unmarked transistor was a programmable unijunction type, this one uses a marked PNP transistor.

The circuitry is quite clever in that it has used the main switching MOSFET as a part of the timing circuitry. That gives the circuit a very low component count.

Note that for some LED loads you may need a 1000 ohm resistor across the load to give the flasher its full voltage for stable timing. The single electrolytic capacitor on the PCB can be changed for a higher value for a slower flashing range.

If you want one of these very cheap modules to experiment with, then here's a link to the item on AliExpress (not a sponsor).
This is an affiliate link, but that will not affect the price you pay.
https://s.click.aliexpress.com/e/_c3bO2Iz9
Cost should be about £2 or less.

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These videos are not sponsored by AliExpress. I buy all these items myself.

Note that the Fakita battery powered light and USB power supply actually has a 12V output on what I thought was a charging port. Very handy for 12V lighting in props and other applications.

Here are some links to the items. These are affiliate links, but that will not affect the price you pay.
Keep in mind that these products may not meet your country's standards.
Some listings may not work for some countries and some may just be sold out or disappear.

When paying on AliExpress, let the transaction complete before leaving the purchase page as otherwise the purchase may not go through.

The crazy little video walkie talkies! These apparently use their own 2.4GHz WiFi link:-
https://s.click.aliexpress.com/e/_c4mqsuFj

The branded Gledopto WiFi WLED addressable LED controller:-
https://s.click.aliexpress.com/e/_c3x6hhlx

Pre-filled iodine swabs. Also available with isopropyl alcohol:-
https://s.click.aliexpress.com/e/_c3foQ8C9

60mm diameter RGB arcade pushbutton:-
https://s.click.aliexpress.com/e/_c4EvIe6v

Thermal receipt erasing pen:-
https://s.click.aliexpress.com/e/_c3u8SIW1

Motorbike style mini LED headlights:-
https://s.click.aliexpress.com/e/_c3udogX7
Shop around for the best price with this.

Square 12V 16 LED mini floodlight:-
https://s.click.aliexpress.com/e/_c36YWSn3

Small "wind power" generator with LED:-
https://s.click.aliexpress.com/e/_c3I9fPOd

Flat paper clip applicator and refills:-
https://s.click.aliexpress.com/e/_c4Dz5Tut

Various colours of 3V LED filaments:-
https://s.click.aliexpress.com/e/_c3ptf6pP

Plug-in voltage display in various colours - it claims a voltage range of 50 to 500V AC, but I'd rate it for 100 to 250V AC :-
https://s.click.aliexpress.com/e/_c3VdGloD

Focusable red dot laser 3-5V - good for aligning things:-
https://s.click.aliexpress.com/e/_c3mH0alf

The Makita style Fakita light and very capable USB charger:-
https://s.click.aliexpress.com/e/_c3ZwWI9R
The USB section can supply up to 4A.
The jack socket on the side is actually a 12V output which seems to deliver around 1.5A before the voltage starts to drop significantly.
The outputs need a load current of about 200mA to stay awake.

And back to the crazy little video walkie talkies! These apparently use their own 2.4GHz WiFi link:-
https://s.click.aliexpress.com/e/_c4mqsuFj

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The circuitry is slightly bizarre. It uses multiple linear current regulators for the LEDs and also to provide current flow evenly over the full sinewave, possibly for dimmer compatibility or to give the illusion of better power factor.

The wires that connect from the lamp to the PCB do not take solder well. That's maybe why the lamp failed. It's pretty common for similar lamps to use square pins on the PCB with the wires tightly wrapped around them to avoid issues like this.

I'm wondering if the failure of the capacitor was caused by electrical noise caused by the arcing. It's generously rated, so should have been OK with the LEDs going open circuit. But the arcing could have caused high pulses of current.

I've still not worked out what the mystery component in series with the LEDs is.

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This unit has a generous multiplier and unusual aspects to its design. It's a real ionizer - not an ozone generator, although very tiny amounts of ozone and other short lived active air molecules will be generated in use. Well below the level that occurs in natural outdoor air.

It can be improved greatly by plugging one or more carbon fibre tufts onto the emitter needles so they stick up above the case.

It looks like they were hedging their bets with the design, as there is a space in the base for a resin potted ionizer module. Maybe for use in 120V countries where the multiplier is less practical.

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It's probably the most basic thing you could mount onto a pole outside and call a street light. But I'm not convinced that it's truly water resilient, and the complete lack of an earth/ground connection is unfortunately standard for this style of light.

There's a commonly spouted piece of misinformation that "electricity takes the path of least resistance", and that is WRONG! Electricity takes ALL paths of resistance, and while the most current will flow in the path of least resistance, enough can flow through other resistance paths to kill you.

Simply assuming a metal pole stuck in the ground is an acceptable "grounding" is not correct. In the event of a fault, the pole can become live, and while some current will flow to ground it may not be enough to trip a breaker. That would mean the pole was still live and touching it could result in you becoming another current path with fatal results.

A rather horrible example of that in the UK is a council worker who was fatally electrocuted while working on a street light where he or someone else had used ground as the neutral due to the proper neutral connection being damaged underground. That is VERY taboo, as a broken ground connection then makes all the associated metalwork on that section live with respect to ambient ground.

This is where I'll have my obligatory rant about the one day G39 slideshow that is often used in the UK to facilitate the use of lower wage labour to do work in one of the most dangerous electrical working environments possible. (lots of exposed metalwork and wet ground). It's a very unpleasant example of the Dunning Kruger effect, where an individual will be over confident in doing electrical work because they have been given an "electrical qualification".

I'd rather all workers in that industry got a deeper education so they understood the hazards of what they were working with. Especially when things are not "normal".

If you choose to use one of these lights, be aware that it DOES need an earth/ground connection added to avoid associated metalwork becoming live in the event of leakage to ground.

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They should work fine on 120V, albeit at a lower intensity.

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This voltage transient shunting device was sent by Frankhe for our exploration. He also sent some candy and some combined metal oxide varistor and gas discharge tube devices.

I'm used to seeing surge protection devices that have a thermal safety device, as the varistor disks gradually break down and can start to pass current continually at lower voltages, resulting in heat.

The internal construction makes me wonder if the MOV/VDR disk was supposed to be sandwiched between the two copper electrodes. Or if those electrodes were designed to go into a ceramic ring to act as a spark gap.

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The normal approach to fixing this is to provide an air buffer in a pipe or pressure vessel. This device does exactly that in a miniature form. Traditionally a stub of pipe with a cap on the end was used as a crude air reservoir, but there is a belief that the air gets absorbed into the water. I was under the impression that the tiny bubbles of air that often occur in the water supply would refill the air pocket. The piston or diaphragm in dedicated units ensures that the air can't get depleted.

Did you spot me repeatedly mixing up air and water during the video? That's the peril of doing live-take recording with a one-way trip into the device being explored.

I fitted a similar style of unit to try and resolve an issue when my washing machine (laundry washer) is cycling its main solenoid valve, but while it helped, it couldn't cure the decades of random plumbing modifications and unsecured pipes under the floor.

The pressure vessel diaphragm failure I mentioned is fairly common. The usual failure mode is for the diaphragm to perforate, and water to displace the air that was there. If a very brief press on the schrader valve stem results in a squirt of water, then your pressure vessel needs replaced. Some manufacturers recommend checking the pressure from time to time and adding more air if needed.

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As I took the switch out of its packaging I spotted an obvious problem immediately - an incorrect wiring diagram. There may also be an issue with the striping on one of the wires in the diagram potentially causing confusion with the striped earth wire.

Other than that, the switch seems to have no other obvious issues, so they were probably just clearing out stock to a less fussy customer base.

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This is probably why they were being sold off cheaply, but it seems strange that they spent so much time and effort designing the product without having a failure during testing.

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These fuse are only for low voltage use, but equivalent circuitry exists for higher voltage use.

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In a previous video I bought one, but discovered that the accountants had visited and reduced the meat content to a box ticking slurry. It appears they have addressed this issue.

These tinned pies have been a British tradition since I was a kid. It was a family treat to share one of these alongside a selection of vegetables.

The tins also often ended up in workshops filled with random screws, washers, and springs.

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I also show how to put the chain and chain-bar onto the unit and adjust the chain tension. The arborist-experts can weigh in on the way I did that. Real chain oil is quite viscous, so I'm not sure how well it would pump through the simple oiling system.

For the cost it's staggering. It hints the premium brand tools are probably made around the same price point and marked up to a price that suits the brand image.

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When a cell does not maintain its voltage after charging (allowing for a slight settling of voltage) then it's time to let it self discharge completely and recycle it. The losing of charge usually indicates a damaged separator between the electrode layers.

Odd circuitry though. They seem to have gone a different charging direction than usual, with the charge MOSFET drive being level shifted to switch a MOSFET on the other supply rail.
I'd guess that the charge MOSFET output is active at all times, except when an end of charge state is detected, by one of the cells in the battery reaching 4.2V.

The moral of this story is to ensure that all power tool batteries are given a top-up charge every so often. Especially the ones that don't get used for long periods of time.

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In this case, an extra auto adjusting component has been added that then scales the LED current down to match the reduced charging of the main capacitor by detecting excessive ripple current.

I'm not sure what the chip in this circuit actually is. It has a code that suggests it is batch marked for a bulb manufacturer.

My apologies for the sound and filming background. I'm trying to make content in different work-accommodation that has no good "studio" area.

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There's an advantage to using at least two in series, in that the classic gallium nitride LEDs often fail with a shunt resistance. So using two in series gives redundancy to still get light and allow the NiMH cell to charge up.

I'm not sure if the chip has a deliberate shunt circuit to protect it from high open circuit voltage, or if the transistor itself starts shunting at higher voltages. The cap voltage is high enough that the circuit could be used to drive 5V microcontroller circuitry. That would require the addition of a 1N4147 diode and a small capacitor (100nF) to provide smooth DC though.

I also added a socket to allow the LEDs to be swapped, but past experience has shown that the contacts need well greased to avoid moisture causing surface corrosion. The grease (or lacquer) can also be applied to the PCB to protect it from moisture, and as always the switch should be bridged with a blob of solder one the light is in use, as they often fail open circuit.

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It's described as an explosion proof tester - but that doesn't mean it can be used in high risk explosive environments. It just means it has a series load option that prevents faulty devices exploding, by limiting the current through them.

As with all these Chinese factory test boxes, they take a rather slack attitude to electrical safety, and the lack of polarity, exposed bulb threads and misuse of speaker connectors for 220V (China's supply voltage) means that the unit poses a shock risk to the unwary.

Still better than the two nails in a bench I've seen being used to test bulbs in some factory videos.

I suppose that one of the screw-in ceramic vivarium heaters could be used as a safety load too if the tungsten bulb it's designed for is hard to get.

These units are sold on AliExpress as LED bulb testers. But I really can't recommend them for safety reasons.

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