An international parts order is too complex for such a small thing. I’m not in the USA or China. So no TP5000 for me, got to work with what I have.

I agree, no charging at 4.2 volts. The current charger I built seems to work well enough. I ran some tests and it charges within spec. The reason I turn off the charger to measure cell voltage is because otherwise I’ll mainly be measuring SMPS noise.

Anyway it beats the charger available in the local market, which is clearly unsafe, no matter how much they assure me that it’s ‘totally OK’.

No worries! I appreciate that you were just trying to assist!

Battery University is indeed a great resource!

However this is not a lithium polymer battery, and as it’s a 32700, it is not a prismatic or pouch cell either. It is a lithium iron phosphate (LiFePO4) cylindrical battery in metal housing. Battery University does have them listed in their table of chemistries (in case you’re curious), but they don’t seem to have much detailed information. Enough to build a charger though :)

https://batteryuniversity.com/article/bu-216-summary-table-of-lithium-based-batteries

Also some more detailed information here:

https://batteryuniversity.com/article/bu-205-types-of-lithium-ion

Anyway, thanks for your reference in any case! I’m not responding to criticize you, only to improve the utility of this conversation in case someone else finds it on search :)

Makes sense!

I’d order online if there was a LiFePO4 charger on the market. However, in my country I’ve been unable to find one, and importing (excise & duties, paperwork) is more work than building it myself. I’ll also likely need a design that I can cheaply include on custom PCBs for manufacture (not for sale to end-users, but for internal use by maintenance technicians).

I gave it a test on a cell today and it seems to charge fine and at a reasonable rate – but in a sudden flash of brilliance, I forgot to physically connect the ADC pin to the battery, so it couldn’t shut off. Well, that’s what testing is for I guess.

Anyway after fixing this, it looks like I can call this a win and move on. If it undergoes destructive optimization, I’ll report back here with a warning to others.

No, that won’t work.

A vibration switch will work.

If that’s not sensitive enough, another option is using a piezo element coupled to the case to detect vibration, with an op-amp or hex inverter to buffer + trigger the 555. However if you couple it too closely with e.g. the floor or furniture it will pick up nearby footsteps or cars. Might be good depending on the situation.

That sounds even better!

Hm, that reminds me! If you’re designing your own PCB, some manufacturers will make the PCB out of aluminum for you instead of FR4. This is commonly used for high-intensity LED lights to help keep them cool.

Here’s some random info about them so you can see what I mean:

https://www.pcbgogo.com/Article/An_Introduction_to_Aluminum_PCBs_by_PCBGOGO.html

An alternative would be copper-clad polyimide adhered to the body. That also has better thermal properties than FR4.

In seconds? Wow. I think you’re right, you might need more than a small fan!

It might be worth exploring heat pipes or peltier effect coolers. The latter makes the problem worse (they are inefficient and generate a lot of heat) but your LED can be locally cooler if you can e.g. move all that extra heat into a big heatsink (also condensation can be problematic).

One cheap source of heat pipes for testing could be old graphics cards – they often outperform simple copper heat sinks. Use thermal epoxy to stick your LED to it and see if the performance is acceptable. On the exotic end of things, you could also water/oil cool it, or (carefully) make your own thermal grease from industrial diamond powder for a small boost in thermal conductivity.

Also even at 95% efficiency, it sounds like your boost converter has some heat to dump too!

Hah! I totally didn’t notice that. Good catch.

These are the smallest fans that I know of: https://www.mouser.com/new/sunon/sunon-mighty-mini-fan/

They go down to 9mm x 9mm x 3mm.

If this is to cool some component in the flashlight, have you considered a heatsink instead?

The most important thing is to tackle projects frequently and get yourself involved with other people doing the same. Learn by doing! I found books, videos, and so on of limited utility by comparison. I’ll include an unreasonable quantity of my notes below.

Some useful resources:

1. Learning Python – a decent programming language to start with since it’s flexible and enforces some good habits : https://python.swaroopch.com/
2. Your local hackerspace, makerspace, or fablab: https://wiki.hackerspaces.org/List_of_Hacker_Spaces
3. Websites with details on other people’s cool projects: hackaday.com
4. You should also learn C / C++ (unless you are an assembly-language degenerate like me)
5. KiCAD is fantastic these days (and free!): https://www.kicad.org/
6. I’ll point out that Microchip Studio is awful and buggy but for some microcontrollers you’re stuck with it. Everyone working with embedded systems gets stuck with some lousy manufacturer-supplied software sometimes.

List of initial things to learn:

1. How to read component datasheets (you will be doing this a lot). Actually I think a lot of my electronics knowledge was picked up from just absorbing datasheets like a weird sponge of some sort.

2. How to order from Mouser / Digikey / RS Components / Arrow / McMaster (these are also a great source of datasheets)

3. Basic laws of electricity and magnetism (any freshman university physics textbook is OK – these pop up used all the time, and even an old one is OK). Just do all the problems in each chapter and you’ll be fine. Or you can tackle “The Art of Electronics” if you like.

4. If you’re into analog, this is a classic (and free!) text : https://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf

5. Soldering is actually pretty easy, just buy some resistors and some prototyping board and get some practice in. You’ll need to learn surface mount soldering to get access to good and cheap parts later on, but thankfully, it is way easier than it looks. Like, really a lot easier than people make it look.

6. How to order manufactured circuit boards from a factory using a design in KiCAD (this is actually pretty easy and cheap!)

7. These days, a lot of components can be purchased on pre-built ‘modules’ that fufill a certain objective. For example, a temperator sensing module might have a sensor and all the supporting components on a little board, so you just connect power+ground and data. These are made specifically with learning in mind and are made in Asia at a very reasonable price – do note though that reading the actual datasheet of the parts in question will give you much deeper knowledge over time.

Tools to buy:

1. A soldering station. Some people suggest fancy expensive stuff, but frankly, some brands of Chinese tools have gotten quite good. Yihua is a good and affordable brand of soldering station. You can get a soldering-iron-only version if you need to save money, but I’d recommend a model that also includes a hot air rework tool. This makes fixing mistakes on boards way easier, lets you salvage components more easily from junk and failed projects, and also adds a lot of flexibility later on.
2. A multimeter / parts tester. Should measure voltage, current, capacitance, resistance and diodes. Pro’s Kit is an OK brand from Asia.
3. Eventually you will need an oscilloscope, but not at the start. Hantek, Rigol, and Unit-T make good entry level ones. Siglent is midrange. Tektronix is for rich kids. An old used scope is fine but often shipping is expensive if it’s one of the heavy ones.
4. Tweezers, wire cutters and strippers. Lots of protoboard and solder.
5. If you’re really into low-level microcontroller stuff, an AVR-ICE will be pretty cool to have a few years down the line :)

Platforms and Communities to Consider:

1. Arduino – largest friendliest community with the most tutorials, but as such has a ton of beginners and students looking to copy/paste code without understanding. So sometimes it’s hard to find someone knowledgeable, and if you do, they might be sort of exhausted. It’s probably the best place to start these days overall.
2. AVR Freaks – the opposite of Arduino. Hostile, but super knowledgeable. I’ve learned so much by searching their forums, I’ve never needed to ask a question! They are great too, but really not a place for beginners to ask questions. It is a good forum to read if you want to learn assembly / C for microcontrollers, but has a steep learning curve – I’d save it for later :D
3. Raspberry Pi – makes everything super easy, generally at the cost of being horribly inefficient and somewhat expensive. It can be a good place to start, but be careful not to learn bad habits here – e.g. using a whole computer system with Linux to blink an LED. You’ll end up having to unlearn a lot to make reasonable battery-powered devices later on. Awesome where processing power is actually needed – machine vision, some robotics, and AI. The raspberry Pi Pico has fewer of these problems (and you can code in Python!) – it’s pretty fantastic and I would personally choose it as my first microcontroller.

Other Stuff:

1. Avoid playing with mains power / high voltage until you know what you are doing.
2. Avoid selling things until you know what FCC / CE is. You can teach courses on what you’ve learned to fund your studies though! I bootstrapped this way.
3. Lithium batteries can be sort of tricky / hazardous. When starting out with them, use the metal cylindrical cells at first. The TP4056 is an OK charge controller to use, and pre-built modules are like a dollar in bulk.
4. I own a prototyping company in Asia, this introduces some bias on my tool recommendations: low cost, high value – but only ‘good enough’ performance and convenience. I also hate solderless breadboards and consider them more trouble than they are worth – some people disagree with me and they are also correct. I also find surface-mount soldering way easier and more reliable than through-hole (most people disagree with me but it’s worth thinking about). Finally, I’m a 700 year old Taoist immortal that still uses a slide rule and writes poetry in Assembly language. So I’m part of an older engineering tradition and it’s worth keeping that in mind when weighing my advice.

Ping me if you get stuck or have questions :)

Plain old static HTML is fine, and you can host it on a potato! Here are some design tips to keep it easy to read. None of them are objectively correct, and you are already doing some of them. They are just some suggestions as you move forward:

1. Don’t use dark-on-dark fonts. Use near-black on off-white or at least something high contrast.
2. Break up content using horizontal rules <hr> and various headers <h1> You can style both of them in css. This keeps things easy to find and read.
3. Generally, do not center-align text if it is more than one line. If you need to display blocks of text side-by-side, put each in a container then left-align the text within those containers.
4. Use a bigger font than you think is strictly necessary.
5. My preference is to use sans-serif fonts. Google makes some good free ones. Sometimes I’ll go back and make titles serif only.
6. Resize and compress your images. A bit higher resolution than you need but with lower quality is usually better than the reverse (for jpegs)</h1>