I think I understand now. I’ve taught intro to electronics for years, and I’d recommend you start out experimenting with resistor networks and measurement techniques. In that case you really don’t need to spend much. All you need is:

• breadboards, plural
• a resistor kit
• some battery holders or clips
• jumper wire, just get the cheap bundles with only plugs and no sockets.
• pliers and sidecutters. Spend more than 3usd on the sidecutters, and do not use them for anything but thin wire and component leads.
• a decent entry level multimeter, a unitrend ut33a can be had for about 20usd plus shipping on ebay, and is fine for starting out.

Try designing networks of resistors with pen and paper, calculate voltages across the individual resistors to get familiar with Ohm’s law and Kirchhoff’s circuit laws (BTW don’t attempt to understand Kirchoff using Wikipedia, someone wanted to flex their brain when writing that article). Build more and more advanced circuits, start out with series, then parallel, and finally mix series and parallel resistors. Try to work out the power draw of each resistor, and just once try to blow one up… On purpose, that is :)

When you’ve sorta got the hang of it, you can progress on to adding capacitance and inductance in you circuits, or digital logics, or what ever you like. But getting the hang on basic circuit theory? well, that can take some time.

I don’t understand the list, the first don’t have a question mark, but then they do. Does that mean that the first items are already in your possession and you imagine needing the rest?

If you have all the stuff on your list, I get a book. Practical Electronics for Inventors by Paul Scherz is a terrific resource. With that in hand you can start dreaming up projects and realizing them.

If the question mark is the stuff you expect to need, I’d say that a lab power supply is almost a must have. Nothing fancy, something that’ll do 20 or 30V and a few amps, if you’re looking for something a bit more, then same specs but with current limiting. Something like this https://www.reichelt.de/de/en/laboratory-power-supply-0-30-v-0-3-a-risu-compliant-mcp-lbn-303-p324544.html but see if there’s a second hand market for this stuff in your area.

Some basic components kits like a resistor and a capacitor kit. Maybe assorted diodes and transistors. Maybe get some voltage regulators, 7805 7809 and 7812, they can come in handy, when you’ve only got a single output on the psu and need different voltages.

That should be enough for a few months of fun. Next you’ll maybe play with timing and triggers. So a pc scope opamps and some 555s.

I may be a simpleton, but I’ve always thought that MELF was just old school SMD, where the shape hadn’t evolved yet from the though hole package.

My thought was based on all the old junk I’ve repaired, where the older it was the more likely MELF seemed to be.

I haven’t designed with MELF before, but wouldn’t it make sense for assembly operations to add a MELF fee?

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It’s made to rotate. It isn’t made to be pulled sideways because the adapter and cable is too short to reach the ground on the way from the wall socket.

Power connectors have been the number one preventable laptop killer in my experience.

The thing that kills the power connector is physical stress. As in force being applied sideways to the plug. If the plug is angled, make sure the cable isn’t pulling on the plug. And if it’s straight make sure the cable isn’t dragged sideways.

The problem with the connector breaking is that it’s either

1. soldered to the motherboard, in which case you need to find someone who can solder (which is when I come in the picture) and can find a footprint compatible part, or
2. part of an assembly with a cable, in which case you need to find the exact part on ebay.

Either way it’s a PITA if the connector breaks.

60/40 baby! https://www.esr.co.uk/shop/contents/en-uk/p32410_100g_0.7mm_(22SWG)_60_40_Solder_(RoHS_Exempt).html Not from this shop, but the hqproducts label is the same.

Word came down from on high, that I wasn’t to use 60/40 for teaching anymore. Usually went through about 1kg annually, and I had just stocked up. I think I had just gotten 8kg, or something like that, because of the bulk rebate, about a year before. And what was I to do? We weren’t allowed to have the solder on premises anymore.

So anyway, 60/40 for 1.0 and 0.7mm and some sn/pb/ag for 0.25mm. And no, I don’t have ventilation for my workspace, but I do have enough solder to last a couple of lifetimes.

Are we talking a handheld flashlight? Or is it something a bit more hefty?

Reason I’m asking is the bearings in the fan and motors. A handheld flashlight is going to take a beating, and the bearings can easily be knocked out of alignment.

As others have said, increasing the output by 5/6 is unrealistic. And even it would work, it’d only be for a short while. Best case is that it works and you’re home and awake when it catches fire.

Better buy a dedicated powersupply. How expensive something is, is in the eye of the beholder, but it is worth it. Most of the ones on this list can be adjusted 10 or 15% and that should get you there from 24V. And they’re actually meant to do it. https://dk.rs-online.com/web/c/stromforsyninger-og-transformere/stromforsyninger/switch-mode-stromforsyninger-smps/?pn=1&rpp=100&sortBy=P_breakPrice1&sortType=ASC&applied-dimensions=4294965650,4290297838,4291523693,4294965001,4293335399,4293589165,4294472088,4294478231,4294273800

Definitely better conduction than the paint. Just make sure that the tape isn’t coated where it has to make a connection to the pads.

Do you have a multimeter? Or other way of gauging the resistance of the new traces?

I don’t know the specific product you’ve used, and my experience with conductive paints and glues is almost nonexistent. But what I remember is that it was neither useful as a glue or a conductor. So I suspect that the resistance of the trace is too great to be used for traces going into the 100s of mm.

If my suspicion is correct, then maybe you can fix it by using the paint to attach something with little resistance in parallel to the paint traces. Maybe stripping a multicore wire and using a single strand of copper, lay it down on the trace and paint over it? Or cutting the traces out of tinfoil and gluing them down to the existing traces with some of the paint?

If it’s just a matter of getting a larger voltage, then you already got 400V. No need for new windings, unless the insulation on the primary can’t handle 400V.

which I found rather neat

I concur, what a great post. Special software for the layout? Please! I’ve got a photoshop license, it’ll have to do.

The rest of us get our calculators at staples, this guy buys the components at the chemical supply store.

This range is a usable - there is no visible flickering even at very low duty cycles.

Before deciding on the frequency, and then mounting the strip in a position where the LEDs are directly observable, you should try moving the LEDs fast relative to your eyes. Eg. take the end of the strip and wave it from side to side. You may notice flicker at frequencies below 200Hz.

Are the changes in pitch alone, or does the amplitude change as well?

What happens if you set the frequency to something extremely low? I know that 50Hz is unusable, it will flicker, but does something still hum at 50Hz? What about if you increase the frequency in steps until you approach 200Hz?

Your multimeter couldn’t measure anything when you went to 25kHz? That may be an issue of the microcontroller not supplying enough current to charge the gate capacitance on the mosfet in time, or not drain it fast enough to turn it off. If you disconnect the esp from the rest of the circuit, can you measure something then?

If yes, then you’ll want to use a push pull pair for driving the mosfet. Or get a mosfet driver, but a bc547/bc549 pair and a bit of passives will be fine, available in through hole, and considerably cheaper.

If no, then either the esp can’t go that fast in this implementation (was it a software PWM?) or your multimeter doesn’t work in that range.

IDK about setting clockspeed in an Arduino, but with a raw atmega328 it’s definitely something you’d do. IIRC the atmegas uses fusebits which has to be set during programming. I suspect that you’d at least need to access the ICSP pins instead of programming over USB. At which point you could just build the needed part of the Arduino on perf board and ditch the atmega16u4 and LDO.

If you don’t mind 4MHz @ 3V, then the datasheet claims that will draw 1.5mA https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-7810-Automotive-Microcontrollers-ATmega328P_Datasheet.pdf but if you refer to section 28 in the datasheet you’ll see that you can go as low as 2.7V.

If you really have your heart set on the PP3 battery then sure, but I’d probably see if I could use 3xAA instead. I just spent 10s googling, so my research may be lacking. An energizer PP3 lithium ultimate claims 750mAh, if we, for the sake of the argument, don’t care about discharge voltage curves and just use the nominal voltage, that makes 6750mWh. Varta has a 2900mAh AA, and 3 of those then become 13050mWh. I know that it’s a crude comparison, and you may not get twice the capacity, but still.

If you went for the AAs then your buck will be more efficient as well. Buck converters become less efficient the higher your input voltage https://electronics.stackexchange.com/questions/528284/why-does-converters-efficiency-degrade-with-higher-v-in so you can double the capacity and increase efficiency with AAs.

Having been walloped by 230VAC, which is far more dangerous, I’m not too worried.

Well hello there Mr Edison, I didn’t realize the calendar read the 1880s again, please refrain from elephant ownership 😀 First off if you’ve got 300V I don’t care what form it’s in, I ain’t sticking my fingers anywhere near it! Secondly at least AC alternates, giving your muscles a break and possibly a chance to let go of the wire, DC isn’t that forgiving. The reason 230V AC is so dangerous is because it’s usually referenced to ground, meaning that if you touch a single wire, you’ll be drawing a current from that point and to your feet.

But that is all theoretical, because while 300V is stored, and the current may become quite high, it’s only backed by 100nF. Still, I’d want it discharged before poking about though.

The battery is a good precaution. Some of my co-students in university made an EKG apparatus. Our lecturer demanded that anything connected to the electrodes was to be powered by a single battery.

I’d be far more worried about using lead solder TBH (love my Sn100Ni+).

I may be a boomer in this regard, and I’m sorry for the rant I’m about to go on (that last part of the sentence was tagged on after writing the following). I prefer my Sn60Pb40 of which I got several kg from when it was outlawed, maybe throw in a little Ag in there for the 0.3mm SMD solder. TBH my love of lead solder may stem from the fact that I have more, in various diameters, than I’ll ever use.

The first couple of lead free solder brands I got just didn’t flow right. It didn’t help that the solder stations it was to be used with at work, by students, was old school Weller stations that just delivers a constant 24V AC to the iron, and the tips set the temp. All the tips we had were at a temp comfortable for lead solder.

But I digress… if you just wash your hands after soldering (and maybe use a bit of ventilation) then your absorption of lead is harmless https://www.ehs.harvard.edu/sites/default/files/soldering_safety_guidelines.pdf

400? I guess that’s in the ballpark I expected it to be.

I haven’t studied the BOM for the DIY solution, but something tells me that you’ll only be able to keep the cost lower than 400, if you value your time at close to zero.

With all that negativity out of the way, I’d definitely want to build it myself too. Although my anxiety level is exponentially correlated to the working DC voltage and at 300VDC I’m definitely well in the thick rubbergloves territory. Be careful with the build!

Easy, you import this puppy https://www.ebay.com/itm/305042665748 and set up your own business offering calibration services to recoup the cost. Then you can apply for the calibration engineer position at Minerva.

Jokes aside, have you contacted a calibration lab? I don’t know what it’s going to cost, but I can’t think of another way, if you’re not going to built the sources yourself. There’s one in the Netherlands https://www.minerva-calibration.com/calibration-service/

It would seem from a quick google that I’m not alone in my conclusion. But at least I have found an article explaining the build of the sources you need http://wolfalex.bplaced.net/electronics/cal/calibrator.htm

I’m not saying that your LDOs are fried. What I am saying is that some LDOs don’t take too kindly on not having the company of some nice caps.

What just caught my eye is that the datasheet specifies ceramic non-polar caps. That seems a bit weird. Just drawing a non-polar would have made sense, but specifying that it is a ceramic is strange. Using a ceramic makes sense, I mean there are 5 times the ceramic 1uF caps on digikey than there are electrolytics, but it should be technologically agnostic… I’d probably try to get some 1uF ceramics for testing.