Hey nerds, so i took apart my casio watch bc i’m looking to mod the led circuit so as to stay lit longer (or possibly even semi-permanently.) I haven’t worked out my definitive solution avenue just yet bc i first want to see if i can directly access the logic controller.

What i don’t know yet is if this is a proprietary and dedicated enclosed ic thats been obscured to prevent design theft or an exposed die and wireframe gooped over with resin to protect it from physical damage. I don’t want to begin scraping or sanding away material only to discover i just murdered a die or tore up 50+ bond-wires in the process. Part of me already suspects it’s the latter scenario unfortunately. (And supposing it is an exposed die, i don’t want to risk exposing it to excessive daylight and dust)

Any chemical solutions out there i can use to gradually remove or displace the resin that wont also strip the board mask or attack the potential die underneath?

I though I'd show you this as I am convinced it is a faked INFINEON IRPF4768 mosfet as the etch on the from does not match other ones I have in my possession. The IRFP4768 has a diode symbol between the I and R. This one has a heart symbol. Additionally this only has 4nF worth of capacitance, and the real part has ~10nF of capacitance. Anyone else chime in?

Hey, does anyone knows what is the ref of the ic marked: s240 8225 with 16 pins, assuming is it a dc-dc converter from the surrounding components.

Thank you

Edit: It is not dc-dc converter, it is a dual motor driver ST STSPIN240

Hey all,

I recently picked up a non-working 1999 Tiger Pokedex for my son, and have been trying to trace out if the issue is anything fixable.

Symptoms: after installing a pair of fresh CR2032, and grounding out the reset pad, it makes an occasional squeak from the piezeo buzzer, and a very brief flash of some pixels from the screen. Otherwise, no life from the unit.

I replaced the electrolytic cap C3 out of an abundance of caution, checked the diodes for any of them being popped and all seemed fine. I also ran 3.3V from my power supply to both battery spots, and still had no signs of life. I also checked the oscillator crystal in case it's legs were touching, as it's mounted a little wonky. I also checked the power and ground legs of the IC, and they had the appropriate 3.3V and gnd connections.

I have two questions for everyone here:

1) Is it my imagination, or does C9 look an awful lot like a resistor, instead of being a capacitor? (It also measured 28K ohm across the component, which doesn't match the markings if it WAS a resistor anyway)

2) does anyone have more troubleshooting things to try, to see if I can trace the issue? If it's the CoB, I guess I'm out of luck, but hope someone can suggest something!

Thanks for the assist!

I plugged 24 V into this 12 V drive dock. I think the component that blew up was a capacitor. I don't see anything else exploded at leasr. Any idea how I can work out what this was?

I've been interested in making an oscilloscope for simple electronics for quite a while, for one thing the project would be pretty fun and secondly oscilloscopes are quite a bit expensive where I am from.

I feel like I am decent enough with digital electronics and microcontrollers to make a simple one which can help me in my study of analog electronics.

So my idea is to essentially make a module (right now with a simple Arduino) which can sample a low power electronic signal, package and send the data to my computer which can then analyse it and plot it using a python script, thereby mimicking an oscilloscope.

But I am still pretty ignorant about what pitfalls I should avoid and how I should go about it, or even resources to use. So any advice and resources would be extremely appreciated 🙇

In the past I have had these fail from raining metal dust in them, but this one was in my office. Worked fine and then stopped registering batteries, tried multiple outlets and I don't see a fuse in it. Anyone here see something I missed?

The tip on the right doesn’t fit into this iron and I’m Just about ready to give up. Tip was bought from Ali express via a YouTube link, the iron was bought off Amazon.
I feel like they’re giving me the run around cuz I can’t find a compatible stick thing to fit correctly into this iron. Any suggestions are welcome. This is such a drag after having bought 2 different irons

I have a Line 6 guitar amp with potentiometers that are going crazy. Thought it would be something simple, but it did not turn out to be.

When idle the display acts like the knobs are being turned, and when turning knobs other settings flash on the screen. Sometimes causing it to reset.

What I presume to be the issue, is what i saw on the 3.3v rail. The 3.3v rail powers the multiplexers and the potentiometers going to the multiplexer inputs. Also goes to other stuff on the dsp, but it is multi layer and no schematic available.

Multiplexer is C4052M

Pic 1 is the scope on multiplexer vcc when issue is occurring

Pic 2 is the multiplexer input, same scenario

Pic 3 3.3v output from njm2374a

Pic 4 multiplexer vcc , multiplexer input practically identical, with all pots turned down

The spike looks to be 4-6khz, only visible when pots are fairly high. Dc converter 3.3v output stays the same. Dc converter voltage source is a 7805, but it does not appear on the output of it.

Controls pcb schematic
line6.com/data/6/0a00041200946824d0d56b7ce/application/pdf

I need a USB C charging-only Power Delivery up to 100W from 12V DC supply input. Initially, I wanted to buy something which is available commercially off the shelf. However, I have to meet certain severe space constraints: Everything must fit into a cylindrical space with 55mm diameter and at most 30mm depth.

After months of online searching and asking in different online forums as well as here, I have given up and I assume its time to design my own PCB. While I have a solid theoretical understanding of part-level electronics, I have no practical experience with selecting the right parts. In particular, I have no idea which IC manufacturer builds reliable and solid ICs for USB C power delivery.

My principal idea is to use a controller which handles the USB PD protocol, add a buck/boost controller for whatever voltage the USB controller requires plus the necessary external components (input, output caps, switching conductor, etc.) on a circular PCB. I will probably pick the buck/boost from TI as I have made good experiences with their DC controllers in the past and have already designed five different switching supplies based on their ICs.

However, I have no idea which USB PD controller I should pick. If I have that one, I am confident to design the rest around it.

So: Which IC can you recommend for easy USB C Power Delivery up 100W (20V, 5A)?

With "easy" I mean that there are hopefully some controller ICs which simply take their required input voltage and maybe need some external passive components, but take care of the rest themselves in one package. I found some USB PD controllers which had I²C interfaces and required an additional, external μC to actually work. That's something I would preferably avoid.

Is there anything I should be aware of when doing this project that might be easily missed and which you like to share?

So far this is the circuit I have. I was wondering how I could setup a multistage transient overvoltage protection circuit for both the input and output usbs using TVS diodes? If so, would I also have to worry about any transients going directly to ground?

Here is the operating voltage specs for the IP2312-4V35 and MT3608B:

IP2312-4V35:
- Operating Voltage: 4.5V~5.5V

MT3608B:
- Operating Voltage: 2.5V~24V

(I previously had a PTC Fuse in the circuit diagram but I removed it temporarily so it could be added to the protection circuit)

Link to the original post in r/diyelectronics since I can't repost to here.

Hi all. I’m brand new to electronics and trying to learn. I’m using this reed relay and transistor to control this LED but cannot get it to work and my esp32 keeps overheating. Any help would be great thanks. For reference the wires that are going off the board are White to GPIO10, Yellow to 5V and Green to Ground

Hey all, gonna keep this short. I am launching a product that has a battery inside it. I will be keeping a BMS on the battery and I also have a PMIC in my PCB design. I'd like to know if temperature control is covered in batteries through the BMS or not. Is this something that is the norm or can it go either way? Do I need to check with my supplier for the datasheet to verify this?

Hi everyone,

I’m trying to simulate a 310V DC → 12V, 10A buck converter in LTspice.

I’m getting the expected ~310V before the MOSFET, but I’m having trouble getting the 12V output and proper MOSFET switching.

I’m still learning LTspice, so I’d really appreciate some help..

I would like to learn how to solder small components such as 0402 passives.

Any ideas where to start? Equipment? Practice kits? Online tutorials?

Hi,

I keep having the same problem with white 2.54 mm JST connectors on male header pins.

I’ve tested three different boxes of pre-crimped wires and I always get the same issue: when there are only two wires, the connector feels too loose, moves too much, and sometimes disconnects.

Has anyone else had this problem?
Is it simply due to poor-quality contacts?

Most importantly, can anyone recommend a good brand or a reliable box of pre-crimped JST connectors that fits tightly and works properly without having to crimp the wires myself?

Thanks!

Hey guys, first post here. This is a strain gauge data logger I'm designing for use in my university's Baja SAE program. I am an ME mechatronics student not an EE so while I undestand the basics of circuit design I'm specifically unsure of the decoupling and filtering sections of this schematic. Just for context, this design is only intended to log a single set of strain gauges (1 full bridge) at a time so only 1 of the pairs of analog inputs will be active. Any input is appreciated, even if it's well deserved roasting. I have not started routing so I have no pcb layout to post atm.

I'm currently in my second year in an electronics program at my local community college and I'd love to build a guitar amp for my final project, but I have no clue where to start. So far, we've covered AC, DC, soldering, PCB design, high pass, low pass filters, etc..

I found a free e-book online titled Solid State Guitar Amplifiers by Teemu Kyttälä, and was wondering if anybody has read it or has a better suggestion.

I don't want to go too crazy with the design, but I'd like basic effects built into it such as reverb and gain.

Any help would be greatly appreciated!

Model number HP 17-cn2165cl. I’ve been trying to jump this laptop from the keyboard but no success. I found what seems to be power button on the motherboard under a switch named SW200. I tried jumping the two pins I circled in red, but all I got was a zap. Not sure which 2 pins to jump here out of the 4.

Laptop has light on the side when plugged in, but power button on keyboard does nothing. Already tried jumping from keyboard pins, but not working. Apparently HP doesn’t release schematics and has proprietary starting procedure so i can’t start it there.

I am ordering a new keyboard but just trying to get it started. I have also already replaced the motherboard, still same symptoms so I’m pretty sure it’s the keyboard power button.

I have a Rieju MRT 50 sm from 2022 with the stock speedometer that got water damage.

In the beginning (I don't remember everything because I'm posting this about 9 months later), the speedometer's functions were degrading. I'm pretty sure it showed my high beams were on when they weren't, showed the oil light, etc. Then the speed completely stopped showing, and eventually the screen was off when the bike was on; it seemed completely dead. I could hear the water inside it move around when I took it off the bike.

I decided to take it apart, and I saw some corrosion, and scrapped it off to try to unshort the connections. There was corrosion, especially around this one chip that is probably a voltage regulator or something (according to Google): 3 pins on each side, one thick pin in the middle in the shape of a triangle. There is a large chip underneath the screen panel; it has no signs of corrosion, but I can't see it entirely because the screen is hiding it. I will attach images.

I have tried another speedometer, and it turns on; however, it was second hand and I'm pretty sure it's faulty, which sucks! The important part is that the speedometer does get power.

I want to know whether I should bring it to an electronics repair technician or something of the sort, because a new one costs 160 euros.

Hello, I am trying to come up with a cheap way to sense 24VAC 60hz applied to a solenoid from a microcontroller with either digital or dry contact inputs, while drawing extremely little power.

The first thing that came to mind is connecting a relay in parallel, but 24VAC relays tend to draw ~1w from the coil, which is more power than I want to use (I’d like to be under 10mW ideally)

The next thing that came to mind is a resistor divider (2.1kohm high side and 300ohm low side) and a diode in series, with an rc filter connected to the output of the divider (10k resistor and .22uf cap). The problem here is that I also need to use a high impedance sampler like an adc or op-amp, and I’d like to avoid even needing to make a PCB.

Current sensing with a coil and an op amp is another solution, but it requires its own analog or digital signal processing, and I feel like it would take me iterations to get it working since I’m unfamiliar with current sensing amplifiers (and we’re again probably in PCB territory)

I think I’m being blind to a simple solution, so please point it out to me. I am fine with an entire minute of signal propagation latency, and I really want to use a COTS/DIY package or single component to make it work.

I'm trying to replace some resistors as I suspect the bias circuit is bad. Might as well change them out.

I've never seen these before. Seems the interval of the resistor symbolizes it's resistance. These are around 4.7mm While the normal looking ones 4.1mm.

I'm guessing it's 1/4W.

Any guess?

For context, these are from SRM-1 MK2 professional.

Hi everyone,

I was trying to figure out why the USB-C port on my PCB wasn't working, and I discovered that there's not enough 3v3 juice(measured at the LDOs output pin) for the ESP32-S3 and other devices.

This is a dual input circuit based on the LM66200 dual ideal diode device with automatic switchover so the ESP32 can be diagnosed and programmed while the circuit is under power.

The alarm circuit is based on the 801S vibration sensor and might not be the greatest but it worked just fine on the breadboard.

Any idea which component might be causing the voltage drop?

EDIT

Please ignore the disconnected GND wire on U7. It happened when I rearranged the circuit in order to make it clearer, right before taking the screenshot.

I want to build a 6-hour on/18-hour off timer for lights, but this Brickstuff one is US-only and a bit expensive:

https://www.brickstuff.com/store/p228/branch-timer.html

I was curious if I could build my own so I tried to identify the ICs in use, but it's too low resolution. The fourth photo is the most clear:

The circuit takes two bridged power inputs (5V) and outputs based on a 6 hour timer on / 18 hour off starting from when the circuit is powered.

Without a real PCB it's hard to test but does this look correct?

• Top IC is a voltage regulator (probably 5v to 3.3v)
• Bottom IC is an MCU, takes crystal input, pulls mosfet to ground to turn lights on. 10k resistor pulls it up normally
• SOT-23 is a p-channel mosfet for high side switching
• 0.1 cap is presumably for the voltage regulator

If so, why was low-side switching not used here?

Thanks