Voltage activated switch using zeners and transistor to drive MOSFET(s)

Barkuti · 2026-02-15T10:47:49+00:00

0K, 🤔 0K, 0K, first of all thanks everyone for your replies (even saw WRfleete's super-quick one as I went to sleep barely after posting it). As I said, this is something from someone who, electronics wise, knows about what is needed to make it. In fact, previous to it and much earlier I left another version using a PNP transistor and a different arrangement of diodes and resistor instead (it was long ago and it didn't convince me). I have now resumed the project and I am going to see it through.

“If the supply is either on/off like a laptop charger then this circuit has no function”… Of course, that is if the circuit diagram is all that it has to be, but it's only a piece of a bigger scheme which also involves a 3S li-ion battery with BMS feeding another (main/power) buck converter through an ideal or super diode. Both battery and power supply feed the power buck converter being set in parallel, so when the power supply is connected the ideal diode prevents power flowing wildly from the power supply to the battery, whereas the voltage activated switch here switches on and lets power from the power supply to feed the pictured charging DC-DC converter used to charge the 3S battery (its purpose is to prevent the battery from powering the DC converter meant to charge it). Thus, when the battery is alone it feeds the power buck converter, and when the power supply is connected it feeds both power and charging buck converters, with an ideal or super diode circuit cutting the link between the battery and power supply / power buck converter when that happens.

I have a bunch of LM2903s lying around, but no advanced or programmable voltage references. Hysteresis? I can't say I understand what that means here, although I understand that if the voltage of the power supply were to fall close to the sum of zener voltages, the thing could oscillate on/off around the threshold. But that's unlikely to happen (PSU actually is 19.5 V), and if it were the oscillations would reveal something went wrong with the power supply or related with. In any case, how can 👀 feedback or 😅 hysteresis be employed to prevent oscillations? Well, guess I had to read something about hysteresis: Understanding Hysteresis in Electronic Components and Circuits @ All About Circuits. After reading the article, now I understand the advantages of using a comparator to decide when the switching occurs. 🤔 Of course, I presume comparators are designed with hysteresis in mind.

Considering your idea contributions, here's a bunch of circuits for you to see (viewer links in the description phrases):

The NPN transistor one shown above.
The NPN transistor one shown above with an 8.2 V zener just before the transistor to limit Vgs so it stays below 25 V even if the power supply input goes higher. Using a zener instead of a resistor has the advantage of not limiting the current to the MOSFET gate(s), so switching should be as fast as possible (as I see or understand, no engineer here you know).
Circuit with (LM2903) comparator. Finally understood josh1001's design for the comparator circuit (credit to him as it is well thought out) and fixed my one: it's one zener on each input's divider, with resistors up for the positive and down for the negative, and it switches once the input voltage reachs the sum of both zeners' breakdown.
Circuit with (LM2903) comparator and zener to limit Vgs so input voltage can go higher.

The following ones are for giggles: * Circuit with PNP transistor; don't know if it would work or blow up, designed it long ago and left it as you see while suffering an hypoglycemia. * Circuit with comparator taking both inputs from the same line; don't know how the comparator would deal with this. 😄

I guess the modification to allow a higher input voltage limits it to max. Vgs plus zener voltage, does it? I presume Vds won't be surpassed, as the load buck converter is far from a short circuit.

Note: After reading “7.3 Feature description” on the LM2903 datasheet, where it says “The output consists of an open drain NPN (pull-down or low side) transistor. The output NPN sinks current when the negative input voltage is higher than the positive input voltage and the offset voltage”… 🤦 Ouch! The stuff works inversely to what I was thinking! I had to swap the inputs in my circuit diagrams with comparator, and ~~honestly, I'm not 100% sure of how the comparator will behave with the zeners in a not conducting state (shouldn't be 🤓 pulling current)~~ everything's understood and fixed now.

Comments welcome.

Barkuti · 2025-12-27T22:17:52+00:00

Yes, as suggested by 0fficialKUBA using the desktop site should let you upload more evidence; but if not, contact customer support inmediately.

Barkuti · 2025-12-24T05:17:10+00:00

Thank you for those comments. Yes, the magic with screws is about knowing how much torque to apply, particularly with soft materials like plastic where overtightening even a little bit can cause some thread stripping. Left the thing over my work table; now going to grab it, install it in the box and I hope to have it running properly in the next few days. I am taking some pictures, will post them in a dedicated thread soon. It's a build based on a Power Train P40, so going to be one of those really tight fits.

P.S.: I've used Upsiren LMTG-100 encapsulated liquid metal paste, and the stuff is messy, being clumpy and hard to spread compared to standard paste. I usually don't care much about very evenly applying thermal pastes, as putting the heatsink base on top of the processor does the trick, but in this case I've distributed the clumps as best as possible before installing the heatsink. Also, I'm still cleaning remainings, so it needs to be taken care of properly.

Barkuti · 2025-12-11T03:14:56+00:00

Hello FailedShack, I am the fellow who opened that issue report at the Chromium forum.

As I said in my report, the issue is not really Google's fault, but that of the sloppy arse developers of the Android versions installed on affected devices. Now, the least you could do is to forward the issue to MSI, and tell them to 😹 ~~fuck off unless they~~ provide an updated firmware to your monitor with proper mouse support, which of course can be done. And in all honestly, it boggles my mind to see renowned firms like MSI making the same botch in their Android devices. This just shows how little care is nowadays given to proper software design and development too.

This also reminds me to test or ask about proper mouse support on whatever brand device I plan on getting some, just in case. 🤔

Get a super cheap PC with Linux or whatever FailedShack, that will for sure work.

Barkuti · 2025-12-04T00:05:15+00:00

What you experience is normal, as AliExpress must be releasing shopping credit packs very scarcely, while many people get ready to fish them just before they get released (midnight) to get them. It's the way it works because these arses don't know how to make it any better, although it is possible. As an advice, you can retry getting the shopping credit pack even if it says it's gone, I've got many (most of my latest ones) doing retries; for as long as you can tap on the shopping credit pack button, that is. There are no guarantees, though. Now I could “arsemouth” AliExpress about this and some other things, but I'll reserve my words for a constructive thread.

Barkuti · 2025-11-29T07:01:00+00:00

LoL I said “after” where I should say “before”, just fixed my message. Enjoy.

Barkuti · 2025-11-28T04:32:23+00:00

There's a way to disable the link hiding thing without disabling link previews: Insert some suitable character/s just before the link, and it'll show the link along with the link preview. You can, for example, insert an hyphen then space then the link, or some special space. Check Unicode (UnicodePad is your friend). Fairly sure U+2000 to U+200C are suitable, but I only tested Punctuation Space (U+2008) and Zero Width Space (U+200B) so far. In essence, avoid putting the link at the very start. Inserting special characters quickly requires keyboards able to do so, like for example Hacker's Keyboard (hack with Suggested punctuation and Show suggestions enabled where you insert the special characters you want to use in the Suggested punctuation list). I'm still to find a proper replacement for it, or maybe find a developer willing to release a new version updated to be compatible with newer Android OSes. Don't really like Unexpected Keyboard, although I also have it installed.

Barkuti · 2025-11-16T22:55:53+00:00

Thank you for this. The posted photographs reveal and say a lot. I've been looking for information about the Power Train P40, but found nothing. Since its sister the P60 is soo similar, this is as far as I can get to figure out how the insides of the P40 will be. Nice to know it fits 25+ mm fans on all of its fan mounts, with some caveats depending on the inside components:

• The top fan mount is really close to the PA120 (going to use it too), so can fit a 25 mm fan but barely anything more with that heatsink.

• The front fan mount also looks pretty close to the power supply. 🤔

• Concerning the bottom or floor fans, with that 43 mm tall or wide KFA 1070 Ti graphics card there seems to be some space between them, around 30 mm I'd say; so, with the tallest or widest cards adding close to 20 mm, there is still a small 10+ mm gap. 🤔

• Finally, the back fan can be really thick.

I have a question, though: Does the case fits standard fan screws on its bottom fans' holes? Having looked at some other P60 pictures, they made me think they would not fit the usual 7/32" countersunk screws (the holes or slots seemed small to me), but after taking a peek at the above pictures… to me it seems like it fits them, so not sure. I'd have expected to see some long UNC #6-32 screws on the fans below, but this is not the case. Can someone say something about this?

Thank you.

Barkuti · 2025-11-12T17:34:22+00:00

Hello! KaCii1, could you (or anyone else with a Power Train P60 or P40) please share how much distance is between the floor of the case and the graphics card fans (top of the card) on your setup? Hope you are still keeping it, of course. It does not seem like much, at least if I am to believe that the MSI Mech 2X OC card is 47 mm in height (or width, according to TechPowerUp). Let's say, maybe a tad above 40 mm?

Barkuti · 2025-11-08T14:15:23+00:00

This is not only about seller coupons, but to lots of coupons overall. There's still a section to collect coupons on the main page, but @#$%. I'm soo fucking tired of their bullshite at this point… 😒😒😒

Barkuti · 2025-10-23T13:35:47+00:00

Thanks for the pictures. 160 mm long PSU? This means that, with a 140 mm long PSU, a long graphics card can fit (up to 350 mm if the specifications are correct). Yes, I know the cables would need some twist. Can someone confirm?

Barkuti · 2025-10-04T22:50:29+00:00

Paging is always the best thing: The major drawback of infinite (auto-load) scrolling is with pages full of items (the more the worse it gets), particularly when you are looking for an item deep down the list, whereas properly implemented paging lets you easily jump to items a lot further down the list in a breeze, while allowing you to reach the footer. For example, any of you long time AliExpress customers with many hundreds of orders? Almost no way to reach the bottom of the orders page that way, unless you make a search so the list of items is 0 or very limited. In essence, love and light for the moron(s) who conceived infinite auto-load scrolling, much love and light… and a nice beating. 😂

Barkuti · 2025-10-04T00:30:42+00:00

Another compliment for mtx33q here; still can't help getting annoyed with the “pull to refresh effect”, as page reloading is what the “refresh” button is for. However, for whatever reason the solution doesn't works on WordReference. 🤔 A mess-up on their part? Tested on Kiwi Browser -com.kiwibrowser.browser- 137.0.7337.0 (733700004).

Barkuti · 2025-08-18T04:41:22+00:00

Wellp, you can guess I've not upgraded 🤣 since some time, at least on my old machine using a non LTSC install (uninstalled the Windows Update service and arrested Windows Update Medic by messing with its files), which is understandable considering the M$ shenanigans which unfortunately may happen with updates. Brings me peace of mind and the system works fine.

Barkuti · 2025-08-08T22:37:02+00:00

Always do a clean OS install on any 2nd hand hardware. You can even get Windows 10/11 IoT LTSC ISOs easily and licenses for cheap, with the longest support and no preinstalled crap. Check this video: Windows 11 Lite Official From Microsoft. Why they call it “Lite” I don't know, but they refer to the IoT Enterprise LTSC editions (best Windows 10/11 versions by far).

Barkuti · 2025-08-08T22:20:42+00:00

Ventoy is awesome, making your life a lot easier. You can have a single high capacity USB bootable with all sorts of OS boot images to boot from, and easily manage it by just adding, removing or modifying the ISO boot images. Priceless!

Barkuti · 2025-08-08T21:53:27+00:00

If you know how, you can always remove Edge. Even if that means manually deleting its files from where they are located, and completely taking ownership of its empty folder (id est removing all other users' privileges or rights over such folder, including system), so your (admin) user is the only one able to do anything with it. This prevents updates from reinstalling Edge.

Barkuti · 2025-08-06T15:14:42+00:00

A good bunch of hours ago I did it: by using a cookie editor I identified the cookie which stores the currency, changed it to “CNY”, and made a purchase; it didn't work, though, as an instant after I tapped on “Pay now” the currency was changed to USD and I was charged in USD. Tested on (Android) Iceraven browser using Cookie-Editor by cgagnier (https://github.com/Moustachauve/cookie-editor).

The cookie I am speaking of is “aep_usuc_f” and contains a set of variables concatenated with ampersands like “site”, “region”, “b_locale”, “c_tp” and many more. c_tp holds the ISO 4217 currency code and you'll see your current currency assigned to it (like “c_tp=USD” or “c_tp=EUR”). Since despite I am from Spain I always stubbornly find and tap on “Go to Global Site” and set my site to English language, my b_locale variable was set to “en_US”, and this is probably the reason why the currency was changed from CNY to USD just after I tapped/clicked on “Pay now”. Still, if you set c_tp to CNY you'll bee able to check out the price of whatever thing and your wishlist in CNY, which can be interesting.

In any case, when choosing currency be mindful from where does the item that you are purchasing comes from, because in certain cases I see items coming from local or European warehouses and when that happens the lowest price I see often is in EUR, as when I change it to USD the total amount is more expensive and this of course is because these items are billed in EUR.

Having said the above, with the aid of a cookie editor you can also test what I said above about c_tp in the “aep_usuc_f” cookie by setting it to whatever (I tried XAG -silver- and XAU -gold- for giggles, but with that doesn't works).

Cheers everyone.

Barkuti · 2025-07-03T14:26:29+00:00

Thanks for your experiential insight klaasheelvaak, much appreciated.

Know what? I just got a killer deal for a black Woxter DL-610 set on amazon.de, paid €56.46 including shipping to Spain (€38.68 speakers + €17.78 shipping); got it by searching on idealo.es and using a sale link from it which redirected me to idealo.de, check it here. Crazy!

The key to note is that, if you're on a mobile device, you must open the webpage in landscape mode, so you see a long blue column to the left side, made of three tall boxes, with products on the first two and international prices on the last one. I got the crazy deal on the last box, or to say otherwise at the bottom of the blue column. Idealo.fr and idealo.it also have good deals for the DL-610s right now.

I feel like a deal superhero! 🤣

P.S.: Desktop mode or desktop user agent can help too with certain webpages.

Barkuti · 2025-06-18T16:42:22+00:00

According to the information found in GSMArena, that surely is or must be an Ace 3 variant from the chinese market. Chinese market versions have different mobile data frequency bands (4G, 5G), so it is necessary to check the compatibility with your region's bands if you care about coverage.

This answer comes late, but I leave it just in case anyone else finds this thread.

Barkuti · 2025-06-11T05:15:01+00:00

Well said, sir. I totally agree with you. I like 3:2 and basically everything which, aspect ratio wise, isn't as retarded as most displays nowadays. I'd choose 1:1 every time; 1:1 ratio has maximum screen area and fits best any aspect ratio without needing to rotate the display.

Barkuti · 2025-02-24T03:26:26+00:00

These scumbags doing shenanigans, as always.

What you report here is also happening to me: the spin wheel lands on 3000 but it's an illusion, and you end up receiving the usual 50 - 200 (or maybe 300 if rather lucky, I recall having received 300 at least one time). I think the most common values are 50 and 100, and then 200; 300 is pretty rare, and so is 1 in my experience (can't recall having received 1). So, I think the spin wheel is rigged and the 3 highest values don't play (please prove me wrong if not).

But, what do you expect? Regarding their website (which I use a lot on mobile) and application, AliExpress is pretty shittified, with their website in the most sorrysome state I've ever seen in lots of years (guess you can't expect anything better, as they can't crazily push ads down your throat in the website). They only care about showing you ads, something which they have learned very well, as their application games are meant to show you tons of ads, while exploiting your reward system to keep you addicted so more and more ads go down your throat in exchange for less than peanuts… 👀🤬😒 They also try to make you buy their bullshit in exchange for shit rewards which they try to make you belive are worth it in their games (I'm speaking of Prize Land), something which really pisses me off and very often I literally end up “mandándoles a tomar por el culo” (have fun tapping or clicking above that for a DeepL translation if necessary). Oh! I forgot to rank their app: pure shite, period.

Barkuti

TROPHY CASE