I'm tinkering with the ATtiny 2 series (ATtiny 3224). I'm also starting to teach myself about switch mode power and surface mount design. I'm planning to drive two Toshiba SSM6K804R MOSFETs. They are logic level MOSFETs with a 4.5V drive. They have a gate capacitance of 1110pF (1nF).

Even though these are logic level MOSFETs, I think I still need an external gate drive for them for crisp switching above a few kHz. I don't need to try and charge the gate directly with the ATtiny as I would need a 2-300ohm resistor in series to protect the microcontroller and that will slow everything down. Also need a pulldown for the gate.

Can someone please recommend a simple IC or maybe a packaged transistor pair that I can slam the gates with?

Questions/comments/advice greatly appreciated!!

I'm currently repairing a device and I'm trying to understand what this circuit board does and how, and whether it is causing the malfunction. While doing that I stumbled upon this resistor whose color code does not agree with my multimeter. I'm measuring 152.1Ω, but the way I'm reading the colors it should be the very common value of 69.1MΩ. If I reverse the order, I get 1.51Ω/15.1GΩ/151GΩ, depending on whether the second color from the left is silver, grey or white. Black would give me 151Ω, but it definitely is not black.

The device this circuit board is from is pretty old. I don't know how old, but there is exactly one IC on it, with a datasheet published in April 1974. The relay in the background has 1979 written on it; I'm not sure if that is supposed to be a year.

Any ideas? Am I reading the colors wrong? Do I trust the multimeter or the markings regarding the intended value of this resistor? Have you seen resistors whose color codes have changed over decades of use?

This cute little monster has chewed a single earbud from not 1, not 2, but 4 🫣 pairs of Shokz Openfit 2+ earbuds. I really don't want to buy a 5th pair.

So, I have 4 unchewed earbuds, evenly split between left and right, but none of them connect to each other. They each also connect to a different charging case.

Question 1: Does anyone have a clue how these things connect to one another? Is there any chance that I could pair them without having to open them up?

Question 2: If 1 isn't possible, is anyone willing to get on a video call with me and see whether you can guide me through switching out parts to repair one of the chewed earbuds? I have no experience with this kind of thing. I have some ifixit tools from opening up an iMac once, and even a (never used) solder. Whether these will suffice ¯\(ツ)/¯

I'm repairing an old TV with corrosion on the board. I'm having trouble reading the schematic from the manual. Here's the relevant section: I have two questions:

Do the thick bars on one side of the capacitor and the base of the transistor indicate those are connected together? I'd tone it out but the board is heavily corroded and I'm unsure if they should be connected. I've also seen these bars on other parts of the board, but the components there are not rated anywhere near as high as C451. I feel like that risks high voltage backfeeding through the other parts of the circuit.

What kind of capacitor is C451, and should it be polarised? The BOM lists it as a pp cap which I understand to be non-polarised, but I can't find any key that tells me what the dot on the symbol means. Let me know if I can provide any further information. Thanks

From the service manual for the Yamaha DX-100 FM synthesiser. The way this looks to me, both the 12v DC power supply, and 9v DC battery power get routed through exactly the same voltage regulator.

So it should be possible to just straight replace the 6x C-cells with 3x 18650s without needing to make any other changes, right?

I know exactly enough electronics to be dangerous, which is why I'm double checking here in case I've failed to account for something.

I'm aware that fresh 18650s put out a little over 4v, but I seriously doubt the vReg tops out at exactly 12v. I can disassemble the unit and check part numbers etc if necessary but I was really hoping to avoid that as it's quite a chore.

Hi Sparkies

I have hit a fibre network conduit in the garden but luckily the fibre isn't damaged. There is an old, redundant copper landline cable in there that I damaged.

My question is, can I patch the PVC pipe and walk away leaving some residual moisture trapped Inside? Or will the whole section need replacing and sealed up?

I have opened a support ticket with the provider and awaiting the official report on repairs.

I replaced my fridge ice maker a few years ago because part of the circuitry burned out. The replacement has also now burned out (though not nearly as badly). For reference, the burned part is supposed to hold onto the end of a copper peg that leads to the heating element (which melts the ice slightly so it can be popped out of the mold).

It seems silly to spend $60 on a new one when it's just $0.05 worth of copper that needs replacing. Is there a safe way to fix this? Unfortunately, I can't just solder the connection because it is enclosed when assembled. For reference, those tabs aren't just fouled, they are burned completely through. My first thought is to pull out the whole trace, solder on new tabs (not sure where I'd get the material), and put the trace back in.

could i follow some soldering guide or is this beyond repair

I've got a vintage HP digital counter, model HP-5216A. It was working, right up until the moment that it fell and broke two of the tubes' glass envelopes.

I really don't know where to source Nixie tubes. I see a few people who are making clocks with them, but not selling individual parts.

It's apparently an HP-1970-0025, which is a rebranded Burroughs B-5560.

Don't imagine this is the right place to find them, but I'm hoping it's the right place to find someone to tell me the right place to find them.

I had an ECU for an air seeder blow up, so I'm rebuilding it from scratch using a Pi and other hardware. I got the shaft sensors reading fine, set up the relays and other switches and lights, but this one has stumped me. The markings give me nothing to go off of (Trison 91779847 Rev C gives me nothing useful), but I still have the borked board that I can trace out. The sensor is fed 12V and ground, and has a white wire that is marked for airspeed input on the wiring diagram of the ECU.

When I trace the white wire on this, it looks like it's conditioned by some diodes (two diodes, in opposite directions to ground) and a capacitor, with a pulldown resistor. The trace then goes to an opamp (TLC2272) inverted input via what looks like a voltage divider, and from there maybe feeds into the processor the board uses. Kind of hard to see from that point on.

I scoped it and if there's data there, it's in the 1-2mV range if I reference from ground, which makes the opamp make sense. But I don't have a very good scope where I am, I do have a Rigol at home that I could get.

I have built a very crude estimate of the airspeed just from the current draw of the hotwire using an ADC and shunt resistors, but I assume I can get a better reading from this sense wire if I can figure out how the hell it's working, via a reference circuit to help me understand. If you know this sensor or a similiar sensor that I can crib the circuit from, that would be awesome.

So I’ve been using an old repurposed tractor lamp as my bedside lamp. I wired it up to mains (EU 230V) with a well isolated alternative bulb and bulb holder (the original bulbs are impossible to find). This has all been grounded and done the best we could. Now comes the problem, we reused the original switch (as it looks good) which it turns out, does not really appreciate having to switch 230V instead of the 12V (or 24V?) it was designed for. I believe I can patch up the switch to work as designed, however I do want a better solution to switching the lamp on and off.

Do relays exist that provide their own low voltage power that I can hook up the switch to? There’s not a lot of space available in the lamp, so I was hoping for a compact, drop in solution.

Other ideas are welcome as wel. I’ve thought of converting everything to 12V, but that would mean finding a new bulb holder, and having a transformer to put somewhere.

I have to design a programmable frequency/clock divider circuit using the 4029 IC. Theoretically, the circuit should start to count down backwards from a given number and when it reaches 0, the 4029 should load the data from the ABCD pins.

The issue is that the countdown stops at 0 and PE doesn't get back to the LOW state. It loads the number, but the SR latch never changes its state so the IC can start counting again. I tried everything and nothing fixes the issue. What can be done in this case? Thanks 🍻

Hello everyone, We have a problem with a circuit we built. The circuit seems to work properly with a green laser diode (130mA, lower voltage). With the red laser (higher voltage) on the other hand, the circuit delivers only 60mA max of the 130mA it should be giving the laser.

The problem seems to be the transistor's resistance because it works properly if we bypass the transitor and give +5V to the LM317.

Is it this assumption correct?

We tried a few transistors (BC241, BC236, TIP41C and TIP41) but with no luck. Is there a way to find a drop-in replacement for the transistor? MOSFET seem to have lower resistance but require an external driver with Arduino.

We need to use the Arduino PWM with these drivers, so at least 980hz switching frequency is needed.

Thanks in advance

Link to the schematics

I'm wondering how practical it would be to drill and tap terminals to add posts to batteries like this: https://batteryhookup.com/products/2x-sunwoda-lf314-314ah-lfp-prismatic-cells-grade-a-qualified-rohs-certified-ultra-long-life-10-000-cycles

The description says that you can only drill 5mm at most. Anybody do something like this before? I do have a shitty Harbor Freight drill press and couple hand tap wrenches.

Recently acquired my first oscilloscope (Siglent SDS804x HD with license key "hack" applied) and I've been playing around viewing various waveforms with it. I have a simple microcrontroller circuit generating a 900Hz rectified sine wave, and it passes through a capacitor to remove DC bias.

I'm confused about what I'm looking at when I plug it into my scope. It seems like my audio signal is somehow being represented in the "negative space" of these traces. As I change my code (different freq, different wave, etc) the negative space changes to match. What I expected to see was something akin to this image: A series of square-ish pulses of different width.

What I would eventually like to figure a way to demodulate the audio wave and display it on my scope as its own trace, then play around by analyzing it independently of the PWM. I'm sure that somewhere in all the math functions on this scope, there's a way to achieve that, but I haven't found it yet.

So a while ago i got my hands on a old sewing machine sadly the foot pedal blew up on me and i also noticed that the machine made my fingers tingle (more on that in this old post here: https://sh.itjust.works/post/35395330 ).

After that i didnt touch the thing for a while but now i needed to sew something so i got myself a new motor and pedal for it online.

The motor fits neat to the machine and the pedal works. But after the last time i was a bit afraid to just touch it, decided to better do a voltage check first.

So i grabbed a Multi meter and connected one side to main earth, and the other side to the metal body of the machine.

And apparently there are 30-32V AC on the metal body of the machine :( Then i tested the current and it was 4.1uA.

I did the same thing for the motor spindle an and the results where even worse >.< 173V AC on the spindle and 43uA when i short it to main earth over the multi meter.

Now my question is:

Is this normal?

Is it maybe just some parasitic currents from the Motor windings acting as antenna and inducting voltage into the metal body of the machine?

Will it kill me if i touch it?

Should i ground the machine to earth using a second plug?

Should i isolate the motor from the metal machine body?

Here are some more pictures from my measurements and measurement setup:

Going to try my hand at sniffing the data driving a WS2812 chain for some future projects, and I'm wondering if anyone has tried this or knows of any existing resources for doing this. I'm fairly confident I can implement it with some RP2040 PIO since I have some pi pico boards laying around. Web searches for the topic aren't turning up much of use, just a billion tutorials for driving the bus.

My only concern that might pose a problem is if the GPIO pins introduce noise or create other issues on the bus I'm trying to observe.

I bought the linked a/c→d/c PSU 2nd hand. I did not look at the connector (assumed it was barrel) and just focused on power attributes. Then when I got home I noticed it has 4-pins. Luckily there is a diagram on the sticker, which says:

P1,2=+12v P3,4=gnd

So I imagine P1 and P3 could supply 12v to a 12v device, and same for P2 with P4. Correct? I’m a bit surprised pins 3 and 4 are labeled ground and not negative. It’s a round connector, so I wonder if the outer ring is actually made to be negative. The a/c input is 3 pin (i.e. grounded).

I wonder if I am misunderstanding because I don’t get the point in 4 pins in this context. If the original appliance (LCD or whatever it is) needs two 12V supplies, why wouldn’t it simply be a 2 conductor barrel considering the appliance could internally wire two circuits in parallel?

I bought it to drive a device that needs a barrel. I’m not really happy to cut the connector off b/c I might one day end up with a 4-pin device, but I guess it’s not worthwhile to try to track down a 4-pin female tip locally to rig it up non-destructively.

To be clear, the appliance needs 12v 5A, which is how the 4-pin PSU is labeled. I hope it’s not a case where each of the 14v pins have 2.5A max.

Or would it need to have 1gpu for every 2 screens, meaning a 2gpu setup? Subsequently, would I also need to be running them on like a threadripper motherboard to avoid pcie down scaling each gpu to x8 each instead of x16?

All hypothetical so i apologive for not being able to provide actual specs. Im helping someone setup a mid-tier racing sim with 1 monitor so providing the actual specs Im using would be obsolete. We were just speculating what it would take to build a god-tier racing sim.

Also, I apologize if this isnt the correct community for this post. I didnt find anything when I tried searching different iterations of 'AskTechSupport.'

I saw it is basically superseeded by the vc-5080 and vc-5081, but I am not finding any good comparisons and don't know enough about this to understand the difference myself.

My usecases are basically checking whether my soldering is connected, whether some switch is working, whether a cable is broken (thus why I am looking for a analog ones: easier to see the needle changing) and sometimes some simple voltage and resistance checking. So as far as I can guess I can I don't need the precision which I would lack with a analog multimeter like that.

I saw an offer for a used vc-5070 for 25€ around where I live. It has the features I need: continuity-sound, exchangable Messleitungen/wires (I need clamps very often).

Good idea for my use case? Is a cheap new one better? Do older models have some quirks that make them difficult/dangerous to use for beginners like me?

I don't need much more than 100Mhz but I'd like to have serial/CAN decoding. I could probably get away with a 2 channel, but it seems like a lot of the extra features like wifi control and digital channels only come on the 4 channels like the 1204X-E, plus it has some waveform generation (though maybe that's an addon?).

Anyone have a budget model they'd recommend? The DS1504 seems like it's getting a bit long in the tooth and the price point doesn't really seem competitive with better scopes.

I tried to push that plastic tab part but it just snapped off. 🫠

I'm looking for a nice, one night project for a stem youth group I work with and the Cataractapult would be a nice change of pace. But...

1. I don't support his politics or views.
2. 15 USD a piece is too expensive for just bare pcbs.
3. They aren't available anymore anyway.

If I had the files, I could just get a small pile of them made, have one for every kid and have enough left over for the club sell for fund raising.

For reference, this is what the Cataractapult is.

https://aveworkshop.myshopify.com/products/cataractapult-model-9000-retina-remover

https://www.youtube.com/watch?v=SSkLVv8q_rs

I have a HDMI breakout board for a cheap and cheerful projector in a Hush box with some automations (turn of fans, dim the lights and the like). This was great, as whenever we turned on the media player - magic!

However due to new HDCP requirements from my partner's favourite app, this solution will no longer work. I have found a HDMI splitter that sorts out the HDCP issue, but CEC traffic isn't passed through and I am at a bit of a loss. I had 2 thoughts:

• Open the splitter and wire the CEC lanes
• Listen to some of the other pins for Video output

I have no idea if either of those would work, has anyone had any experience with this, or got any advice?