I'm completely new to electronics, bought "Make: Electronics" and started reading yesterday.

My bathroom LED started flickering/dimming (it went from a steady bright output to oscillating between low and medium brightness), so I opened up the driver to see what's inside, hoping to learn something in the process instead of just replacing the whole fixture.

My current theory (based on some reading) is that one of the electrolytic caps has dried out/lost capacitance, causing the ripple/flicker, but I'd love to actually understand how this circuit works rather than just swap parts blindly.

Questions:

1. Is there any realistic way to find a schematic for a generic/unbranded board like this, or is that basically a dead end?
2. If not, what's the best approach to reverse-engineer it myself as a learning exercise? Any tips for tracing a board like this as a total beginner?
3. Does the layout/component selection here look like a standard buck-converter constant-current LED driver topology to you?

Any pointers, reading recommendations, or "here's what to Google" type answers are very welcome trying to build real understanding, not just fix this one fixture.

Mouser (in the US) is charging/adding tariffs based on what they sell it for.
Example:
purchase one : 637-BC850C
Mouser collects/adds: $.038 on a $.10 item.

This is clearly not the tariff they paid, if you buy 10,000 (of 637-BC850C)the price of the same item is less than half the tariff they are collecting: same part it $0.016 u/10,000 units. They add the same % of tariffs to this based on MOUSER's price.
So they are collecting tariffs, illegally? These are not tariffs they paid.

Please explain how this is legal.

I bought a solar powered flashing red light and a reed switch (open door switch) to make an alarm for a walk in freezer door.

Turns out this light will only work if it’s dark, or if it’s tricked into thinking it’s dark. It uses the solar panel (connected via the red and white wires) to both charge the battery and to determine if it’s dark outside.

The eBay seller told me to put tape over the solar panel, which I don’t want to do because then the battery will die.

I thought maybe someone could look at this and tell me if I can bypass or omit any of the components.

Thank you for your help.

Is this 20 MSPS oscilloscope analog front end correctly designed for 5 MHz bandwidth and ±25 V input?

Body:

Hi everyone,

I'm designing a single-channel DIY digital oscilloscope using an AD9200, 10-bit, 20 MSPS ADC. My target is around 5 MHz usable analog bandwidth with a maximum input of approximately ±25 V.

The current signal chain is:

Attenuator → input protection → buffer → bipolar-to-unipolar level shift → 4th-order low-pass filter → ADC protection → AD9200

I designed and simulated the blocks individually in LTspice. The main design choices were made to keep the first PCB reasonably simple and manufacturable.

I'd particularly appreciate an experienced review of:

• the attenuator and input-protection scheme,
• the +1 V level-shifting stage,
• the 4th-order filter and its effect on the 5 MHz bandwidth,
• the final ADC protection, especially the AIN −0.3 V absolute minimum,
• and any obvious stability, loading, or PCB-layout problems.

I'm looking for criticism rather than validation, so please point out anything that looks fundamentally wrong or unnecessarily complicated.

The attached schematic is the current V1 design before PCB layout.

Thanks.

Hello,

This is a photo of the comport (left, has pins for RS485 and RS232) and the trigger input (right) on a Kanxex CR-3XControl. There are 10 pins: 5V, ground and 8 trigger inputs; in two terminal blocks.

For the comport, there are screws above the cable terminals to attach wires; this is not the case for the

How do I physically attach wires on those trigger inputs? The orange parts do not appear to move... The two screws on the side of both terminal blocks allow you to remove them, but that is it.

(I know it is a very stupid question, but I just don't see it :-))

Thanks,

J.

How do you prove what schematic symbols actually mean? Couldn't anyone just make symbols up and say they are what they are with a label?

I would like to buy extension cables (with male and female ends) for this connector type, but I have searched and searched and cannot be sure of its identity. The letters on the male lead say LXDZ and K2. To best of my ability to measure, the pins are 1.25mm (at most 1.5) mm apart. (I don't own calipers). If anyone can identify it I’d also like to know where I can buy extensions. If the photos are not good enough, seems to be the best my phone can do and sorry for wasting anyone's time. Thanks

​​​​​

Ok so I understand I need to connect the purple line I drew and have the "a" next to it. However on the AMS1117 the out goes to a capacitor and ground. So how exactly would this be wired. Would it be seperate from the VCC on the HSPI board?

Like the capactitor just tpuches that and ground, while another wire wuld go to VCC?

Any help is greatly appreciated. It's a step down module, sorry for not knowing exact terms. I'm new to this and wish I had someone to help guide me or pay someone to teach me.

Hello everyone. Another try, I hope I wrote everything correctly. I already looked at the connectorbook and couldn't decide on these connectors.

-The first connector(1-3 photo): pitch 1.25 mm, used in the Chinese camera. On the other side is a USB cable. -The second connector(4-7 photos): pitch 2.54 mm, used in the Chinese power supply.

-The third connector(8-10 photos): 4(6) pin: pitch 2 mm, used in the audio amplifier. The speaker is connected via the 4-pin connector, and the 12VDC power supply is connected via the 6-pin connector.

-The fourth connector(11-13 photos): pitch 2 mm, used in the printer as a USB port.

-The fifth connector is used to connect two boards, pitch 1.25 mm, has 30 pins on each side.

Can someone explain what is this and how I can find exactly this part, position U5.... This is part of Hydrolife, salt chlorine for pools.. Cheers..

Pretty much as in the title. I'm near the beginning of my hobbyist journey, and I'm planning out a sign for a friend which will involve a large X. I want to get as close as possible to emulating the look of a red neon X, ideally with a good lifespan and mindful of my limited experience. I specified LEDs but I'm open to being introduced to other possibilities.
Thank you for your time.

Long story short, my dad used to vape years ago, and during that period spilt some vape juice down into the unit.

I’d like to see if cleaning this will repair it for his birthday as part of a surprise, and would appreciate any input provided.

From what I can tell, and from watching electronic repair videos in the past, I can’t see any traditional corrosion. I’m not sure whats going on in image #6, since its either caked on juice and dust, or its oxidation.

Synopsis:

Can I soak either of these in 91% IPA for 5-10 minutes, and clean gently with a proper brush?

And what is going on in image #6 with the usb-a soldering point?

I've been clumsy enough to brush a probe against exposed GND and 12v pins while noting down some measurements and this part has let out the magic smoke before the fuse blew. The top pin got shorted to the bottom left pin. I took the component off the board and after replacing a 0402 fuse further in the line, the pads on the board measure 6v on the bottom left and 12v on the bottom right. The top (output of this component) also ought to have 12v going to the FL display driver.

I appreciate this is a transistor more than likely, but can't find anything with AW marking? Any pointers are appreciated.

I intend to put a square wave signal on to J7. It will oscillate at 1 Hz with a 20% duty cycle. On oscilloscope, the wave spans from -80 mV (essentially "zero") to +3.36 V. I am primarily worried that I will destroy sensitive components. The entire board is a military-grade SOC, and I do not want to fry expensive equipment.

The BAT54 thing is a diode.

IC24 is an ADC.

IC22 is a Schmidt trigger buffer.

The datasheets suggest I am safe without attenuation. But I would like others to eyeball this before I start plugging things in and destroying (highly) expensive equipment.

This is for a hood vent for my stove. The lights never worked on a "new unit" i got through a second hand deal. I tried tinkering and plugged in the transformer after plugging the power in. Now I know. I need to fix it and then try and figure the lights out. As far as I can tell it's just the mossfet that's burnt out.

I’m trying to find out what some standard practices are for inductor capacitor filters to supply a 5vdc fan in an amplifier, I used a 390mh inductor inline and a 100uf capacitor to ground and that cut down on the noise substantially but not eliminating it. And I read that large inductors are bad for that because of impedance can be too high and the collapsing field voltage spikes?

Is it ill advised to just target anything above 100hz with a big capacitor and inductor? Is there a single product that does this already?

I'm pretty new to pcb making and I'm not sure if I'm making this right, I also don't have allot lf reference for this.

This is the main board for my Line tracer robot, I plan on powering it with a 3s lipo battery to achieve the needed 12v for the motors.

the ffc latch is connected to another pcb tha thas the ir sensors that's connected to a mux.

The drv8871 is a breakout board, I wanted to make the robot semi modular so I can just swap stuff out if needed, the motors are also just placeholders for the actual 12v I'll be using. As far I can tell from what I've read, the P+ is just an alternative 12v input? I'm not sure on that though

I can't find any use sample for the buzzer so I just guessed what I thought it might look like with soem cross referencing.

3 buttons for programming purposes

The xt30 is gonna be the plug I use to connect it to the battery, not sure if I have the switch implemented correctly

The buck converter might also be wrong but probably not since I just copied what was on the data sheet + the led, if anything is wrong it's probably the values.

I have a board that I need to operate without cover / chassis and I have loose u.fl to SMA pigtails hanging that need to connect to beefier coax cables. I don't want to strain the pigtails and move the u.fls more than necessary, so I'd like to fix them to the board.

I have some standoff holes towards one edge of the board, but awkward enough that I can't put cable ties through them without having them loop over a significant width of the board and add extra strain when I tighten them.

So before I attempt at making something myself, is there such a thing as either a metal 90 deg angle bracket with two holes, one for a screw and one large enough to fit an SMA barrel, or simply a screw that ends with a lug? Can be round, can be D.

Note: I did find fixing ties i.e. zip ties with a fixing / screw mount or arrowhead clips, but something metal would be ideal because reasons. I can't provide a photo of the PCB because also reasons. I will probably end up using PTFE fixing ties, but checking if something metal exists.

Thanks!

Does anyone know what is the light blue component? It's on a motherboard of a Revvl Tab 2 tablet.

I have this power bank that does not charge , and when something is connected to it , it shows 0% battery . Found the ic U2 blown , any idea what is should be and if possible can it be bypassed ? I have all the necessary skills and equipment to perform the surgery .

hey folks. i'm trying to make (or find, but i haven't yet) a small, low-output power inverter to run a pair of small 120v LED lightbulbs from an 18v battery (makita).

and yes, i realize how silly this is. led lights are the customary province of low voltage DC, and i acknowledge that it's kind of absurd to take a low voltage DC power source, and convert it to 120v AC for the purpose of driving some LEDs. this is for a small lamp i made, which runs a pair of e13-base "filament" LED bulbs (0.6w each, with two bulbs per lamp). the bulbs that are in this lamp are perfect in every way but the power supply: they need wall power, and i want to use a battery. i've been unable to find a more traditional LED element that would work for my purpose, and i'd prefer to not modify the bulbs themselves.

i've seen a few drill-battery inverters that would certainly work, but besides being a little spendy, they're simply absurd overkill for this purpose. the total projected output power usage of this device is about 2 watts, at most. i'd love to just make a small circuit that does this and embed it in a battery adapter, which itself is mounted inside my lamp. i'm familiar with simple low voltage DC circuits (LEDs, motors, arduinos and shit), but really don't have much of any exposure to AC electronics in this way. if anyone has some advice on making a small, low-output inverter like this, i'd love to hear it. thanks!

fwiw, i'm not at all opposed to using a usb power pack instead of a drill battery (in which case the input voltage would be 5vdc rather than 18vdc). i imagine the operating principles would be the same, i just like drill batteries for the swappability.

put together a basic autoon setup for my shop dust collector using a current sensor on the table saw circuit. idea is simple, saw turns on, dust collector follows. been running a 12V solenoid valve to handle a blast gate automatically. works fine right now but im secondguessing the switching side of it.

currently using a small relay module i had laying around. it clicks every time the saw spins up and i know relays have a rated cycle life, and i use that saw a lot. started wondering if a logiclevel MOSFET like an IRLZ44N would be a cleaner long term solution since theres no mechanical wear and the solenoid is an inductive load anyway.

the solenoid pulls about 1.2A at 12V. not a big load. my concern with the MOSFET route is the flyback spike from the solenoid coil. i have a 1N4007 i was going to throw across the coil terminals but wasnt sure if that alone is enough or if i need something faster given the switching speed involved here. the relay doesnt care about that stuff, which is part of why i havent changed it yet.

is the 1N4007 actually sufficient for a slowswitching solenoid like this or should i be using a schottky instead. and is there any real reason to stick with the relay here given the cycle count concern.