We have a council-supported “man cave” - with a couple of funded workshop technicians and lots of unpaid volunteer specialist engineers, mechanics, DIY’ers etc. Plus a very well equipped multi-discipline workshop. So you could take those bits of kit there and someone would give you a hand setting them up, teaching you how to use them, repairing them/maintaining them as needed. Even getting them calibration certificates (thanks to one of the volunteers who has access to calibration equipment). If you don’t have one locally - wouldn’t the technician at a local school/college/university help? Is there a local community online group that you could join and ask for help?
The standard countryside yokel reply when asked for directions applies, " Arrh, If you need to get to there, I wouldn't be starting from here".
For battery powered LED lighting - you shouldn't be using 12v LED strips. You should be using bare LEDs and a constant current supply. Converting cell voltage to 12v, only to use (probably) resistors to limit LED current isn't the way to go.
You will lose far more, efficiency wise, starting from there, than you are worrying about losing in the series or parallel considerations.
But then, you'd design the required power source and then the charger associated with it - not start with a charger, which then constrains your battery pack topology.
DuPont connectors equates to logic level signals. There may even be a 3.3 v <>5v link selector on the adapter.
Whereas DB9 equates to "RS232" level signals. Generally, at least the capability to accept those voltage levels, even if not necessarily producing them.
My first step tends to be to connect tx to rx and see if characters typed in a terminal/emulator get echoed.
An RS232 breakout box is pretty much a given necessity, when it comes to sorting out what's happening on all those pins and sorting out what to connect to what.
Wear trainers not sling backs. Molten solder and your tootsie don't go well together.
I turn the printed circuit board component side down and wave a hot air gun over the flip side, whilst tapping the board against the edge of work bench. The result is usually a cascade of components (and blobs of molten solder).
Very therapeutic. When I'm stuck trying to work out how to do something, when everything I have tried has failed miserably, I deconstruct something electronic. No, I keep well away from psychiatrists.
You (I anticipate) won't be doing this 9 hours a day, 7 days a week - most of the nasties are long term exposure ones, so a one-off should be fine. If anything ever irritates your eyes or throat, get out of there and ventilate the place.
That is pretty much exactly a conventional momentary switch. It just happens to be packaged for use controlling something a little different.
It should be fine for your application.
One thing to note - the contacts will probably "bounce" as the switch is closed. Produce a string of momentary connections and disconnections for, oh, say the first few thousandths of a second. That's perfectly normal for a mechanical switch.
That won't matter in its intended application. But if you are using it with electronics, say counting the number of times the switch is operated - the results can be unexpected.
You can look up "debounce" to see how this can be worked-around.
You can make your own current-limited power supply, probably from bits and pieces you already have. Let's say that you have a 5v dc power supply and a hand full of rectifier diodes and resistors (various values and sizes).
Put a series chain of forward biased rectifier diodes and resistor(s) across your 6v supply. Choose enough diodes to give you a 3v output. Now choose a combination of series/parallel resistors to give you a 2v drop with a current of, say 100mA. You need 20 ohms - so that could be 5 x 100 ohm resistors in parallel.
The most current that can put out is the full 5v across 20 ohms - but at that point the output voltage will be near zero.
Bench supplies, well reasonable ones, allow you to set a current limit as well as an output voltage. At loads below that current limit - it operates as a constant voltage supply. At loads above - it operates as a "constant current" supply. You would set the output current limit to 100mA and that's the most that it will output.
Now the rectifier diodes plus resistor would allow the current to increase above 100mA, up to 250mA when the output voltage will be near zero (short circuited) - if you want better than that, then you can add a transistor and a few other components.