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3 votes

Is the wiring of this STM32 minimal system acceptable?

I'd call the differences between the top and bottom half routing rather cosmetical and irrelevant. What matters here would be two things: Conceptional fitness for your purpose Signal quality and EMI ...
Marcus Müller's user avatar
1 vote

RF Microstrip trace polygon

Whatever you do, make sure you pay attention to the geometry of the stackup. If you put a plane above and a plane below, the transmission line changes from a microstrip to a stripline. Notice the ...
Voltage Spike's user avatar
  • 84.6k
1 vote
Accepted

RF Microstrip trace polygon

do I need to apply a ground polygon on the top layer side of the PCB or not? To make a microstrip transmission line, you do not. And if you do, you should keep the top layer ground region well away ...
The Photon's user avatar
  • 131k
10 votes

Pattern on a PCB

According to this NXP document, PCB spark gaps have an approximate breakdown voltage of V = 3000pd + 1350 where p is the pressure in atmospheres and d is the gap in mm. So a 0.5mm spark gap would have ...
Spehro Pefhany's user avatar
9 votes

Pattern on a PCB

Those are spark gaps. You sometimes see them on things like mains inputs on power supplies. Usually under the mains input common mode choke. In this picture they also seem to be under the common mode ...
Justme's user avatar
  • 157k
12 votes

Pattern on a PCB

That looks like an area with two pairs of pointy “teeth” with a small air gap between them, and no solder mask over that area. Most likely this is part of the board’s EMC protection, providing a place ...
MarkU's user avatar
  • 14.9k
29 votes
Accepted

Pattern on a PCB

The pattern is a pair of spark gaps, a kind of low-cost voltage limiter. The closely-spaced pointy conductors favor the formation of a spark, and the soldermask is removed (the tan rectangular area) ...
Dave Tweed's user avatar
  • 175k
11 votes

Need help identifying component with 'T4 G4' markings

It's likely a Diodes Inc. BAV16W or 1N4148W fast switching diode in a SOD123 package. The following marking information is shown in the datasheet. The horizontal T4...
Tom Carpenter's user avatar
0 votes

Could I use a linkstyle momentary dpdt switch?

You either need the PCB or at least wire the switch correctly the way the PCB does. Look at the copper wiring on PCB. The RED wire is switched between the BLUE and BLACK(?) wires. When RED and BLUE ...
Justme's user avatar
  • 157k
1 vote

PCB Silkscreen Marking

No one checks designators, there's no like universal regulatory process or anything -- at most, in-house standards apply, or only what is dictated by contract terms. There are standards, such as ANSI-...
Tim Williams's user avatar
  • 39.1k
0 votes

How do I generate a trigger signal from a periodic analog signal having varying amplitude

I would use the following: Since you want a threshold relative to the signal's amplitude, first decide if this is RMS, average, or peak amplitude, and use the corresponding detector on the signal to ...
bobflux's user avatar
  • 79.5k
0 votes

How do I generate a trigger signal from a periodic analog signal having varying amplitude

Of course, it's impossible to have the circuit trigger as some point on the rising edge of its own cycle, since you can't know what the peak amplitude is until you reach it. You could sample the ...
vir's user avatar
  • 20.2k
0 votes

How do I generate a trigger signal from a periodic analog signal having varying amplitude

With edge triggering, you generally have two main levels: the arming level and the firing level. When your signal passes the arming level (e.g., a 0V DC offset sinusoid rises above 0V), your system ...
Kiwi's user avatar
  • 13
8 votes
Accepted

Why does IPC 2221 require so much more spacing at elevation?

It comes from the Paschen's Law. The following graph is a Paschen curve taken from this research. The graph may look a bit awkward to make a conclusion as "required clearance increases with ...
Rohat Kılıç's user avatar
4 votes

Why does IPC 2221 require so much more spacing at elevation?

It's more of a one (or two, in this case) size fits all strategy. If you don't want to deal with calculating the exact factor for the altitude at which you'll be operating, then the values given will ...
vir's user avatar
  • 20.2k
1 vote

Will such a scheme work correctly with ATmega328PB?

The accepted answer provides general suggestions on styling and common norms on PCB design but never point out the mistakes on the schematic. I see at least two mistakes. CC1 and CC2 on Type C USB ...
hcheung's user avatar
  • 301
5 votes

Attaching foam to the bottom of a PCB

PCB pillars are a purpose designed tool for the job: While the foam that comes on them is self adhesive, if you don't remove the backing paper they're quite usable as a movable soft contact with the ...
user1908704's user avatar
0 votes

custom PCB design for UART-TTL to STM32

If you want to interface TTL-level UART signals to the STM32, you can connect them directly to the STM32's UART RX and TX pins. If you have RS-232 level signals you will need an RS-232<->TTL ...
Peter Bennett's user avatar
2 votes

custom PCB design for UART-TTL to STM32

Yes there are many errors. First error is that the chip does not even have USB data wires connected to the connector, and there is not even a single bypass capacitor for the supplies. Just look at the ...
Justme's user avatar
  • 157k
3 votes

Attaching foam to the bottom of a PCB

Unless the desk is perfectly flat with nothing on it, and you carve out bits of the foam where the through-hole component legs are, a layer of foam across the whole board is unlikely to sit flat on a ...
Tom Carpenter's user avatar
2 votes

Attaching foam to the bottom of a PCB

My answer would be very much the one of GodJihyo, except it you get your PCB manufactured industrially, you might give a try at getting a 2nd "PCB", except with just holes for standoffs/...
user1532080's user avatar
4 votes

Attaching foam to the bottom of a PCB

You might look at using something like hobby wood, thin wood sheets typically made of basswood. You could have mounting holes in each corner of your circuit boards and maybe one or two in the middle, ...
GodJihyo's user avatar
  • 24.7k
1 vote

74HC595 behaves randomly, need help with my circuit

Each time I start it, the output values are all random until it settles on a number It sounds like you are seeing the register powering up in an undefined state, which is normal. There's no guarantee ...
Simon Fitch's user avatar
  • 38.3k
2 votes

Attaching foam to the bottom of a PCB

Maybe consider 3D printing a board holder that protects the bottom and keeps things from getting scratched. I do that sometimes when a board is going to be handled a lot (e.g. for firmware or HDL ...
Spehro Pefhany's user avatar
0 votes
Accepted

74HC595 behaves randomly, need help with my circuit

I would like to thank all of those who tried helping me troubleshoot this problem. Unfortunately, none of the answers worked. I therefore used the remaining pins of the ESP32 to drive the K155NA1 ...
TakeHere's user avatar
7 votes

Attaching foam to the bottom of a PCB

Unless there are heat producing or high power devices that are counting on airflow for heat rejection, a closed-cell flame-retardant, adhesive-backed foam would work. Knowing students however, ...
vir's user avatar
  • 20.2k
0 votes
Accepted

PCB design review (Altium)

The quality of the schematics image is not great, therefore I can't read part numbers, but: Check that there is no required pull-up on NRST. All the part on the same side is easier to build. Check ...
Blup1980's user avatar
  • 6,481
2 votes

74HC595 behaves randomly, need help with my circuit

Actually it's the other way around, I would not expect the breadboard prototype to work well either. The breadboard even connects LEDs directly to HC595 output pins which may lead to burnt-up LEDs or ...
Justme's user avatar
  • 157k
0 votes

74HC595 behaves randomly, need help with my circuit

I see two possible issues here: You should have at least 100nF (0.1uF) capacitors between the positive supply pins of 74HC595 and K155NA1, and their GND pins. They shoud be as close as possible to ...
Edin Fifić's user avatar
  • 5,481
4 votes
Accepted

Will such a scheme work correctly with ATmega328PB?

Firstly, I suggest working on your diagram. A hard-to-read diagram will almost inevitably have mistakes. Specifically about the circuit: Where are the decoupling caps? How does ...
jonathanjo's user avatar
  • 14.9k
2 votes
Accepted

Source impedance-trace impedance - load termination impedance confusion

Normally, Zsource = Zline = Zload is required in impedance equalization situations to avoid reflection on the line. You don't need the source to match the characteristic impedance of the line. The ...
Andy aka's user avatar
  • 464k
1 vote

Source impedance-trace impedance - load termination impedance confusion

No, the transmission line, if considered lossless, has zero resistance. Therefore it does not divide voltage, when you drive it with 0 ohms. So for a 3.3V waveform going into a PCB trace, will travel ...
Justme's user avatar
  • 157k
0 votes

Source impedance-trace impedance - load termination impedance confusion

The normal condition you suggest is the double-termination condition. This tends to maximize bandwidth (an idealized simulation won't show anything, but a more realistic lossy and dispersive model may)...
Tim Williams's user avatar
  • 39.1k
2 votes

Can heat sinks and/or heat pipes be retrofitted onto an existing electronic device?

I guess you'd have to do a bit of reverse engineering on that hub. Say it's a board in a small plastic enclosure. Plastic doesn't conduct heat very well, and there isn't much air convection in a tiny ...
bobflux's user avatar
  • 79.5k
2 votes

Testing to find polarity of PCB power connector

The M in front of Ω means million. So you read very high resistance values here and they will not tell you anything useful. A negative resistance value should tell you, that this measurement method ...
Jens's user avatar
  • 7,297
1 vote
Accepted

Testing to find polarity of PCB power connector

On the big electrolytic capacitors, there should be some indication of polarity (often only - is marked). Put your multi-meter in continuity mode, and check if the pads from the capacitor show ...
Sandro's user avatar
  • 7,697
1 vote

What are top and bottom copper types in KiCAD used for?

It's pretty much just a label to help you organize; as far as I know, KiCad itself doesn't do anything with it. Some add-on programs might use it for something, but I've never touched it.
vir's user avatar
  • 20.2k
3 votes
Accepted

Help identifying hollow spring / inverted header sockets

Digikey sells them: https://www.digikey.com/short/wnjj5m37 Their Digikey catalog section for this is: Connectors, Interconnects -> Terminals -> PC Pin Receptacles, Socket Connectors Mill-Max is ...
Davide Andrea's user avatar
2 votes
Accepted

Request for Review: First PCB Design - Feedback on Potential Issues or Missing Elements

Misc review remarks: Depending on your BoM budget I'd use something more modern than SN65HVD232, although that might force you to also include a 5V regulator. I've used the one you've specified quite ...
Lundin's user avatar
  • 21.1k
0 votes

Matlab simulation of PCB IFA

The y axis of these graphs appears to be multiplied by 10e-3 and is in dB. Therefore, it basically is equivalent to being 0 dB across the entire bandwidth, which is pure reflection, so neither of ...
Matthew Kunkle's user avatar
2 votes
Accepted

Unknown SMD Component LP 27 L#

should be a P6SMB27A diode in SMB package from FAGOR No picture found but the following diagram shows the typical marking: The logo of FAGOR is visible when zooming in your picture (not a # but a F)....
vivier's user avatar
  • 1,083
0 votes

Altium annotation - no changes were made

You want to try and have it look for more changes than just comments and library reference. Altium will only generate changes on what you tell it to check. That goes for ECOs and DRC checks.
Voltage Spike's user avatar
  • 84.6k
6 votes
Accepted

SEPIC DC-DC converter

Does this help you understand: -
Andy aka's user avatar
  • 464k
2 votes
Accepted

What should I do when clearance boundaries overlap with SMD pins?

Datasheet: https://www.ti.com/lit/ds/symlink/tps62136.pdf?ts=1719417594079 The pad pitch is 0.5mm (p.42): IPC-7351 describes solder joint geometry and terms. This is identified as a flat no-lead ...
Tim Williams's user avatar
  • 39.1k
1 vote

Choosing trace width and spacing

Conductor spacing as a function of voltage and device type is given in the IPC-2221 standard. The Saturn PCB design toolkit has a calculator for the spacing: Conductor widths are also listed in the ...
C. Dunn's user avatar
  • 1,329
0 votes

Is solder mask expansion overlap legal?

IPC actually recommends a 1:1 Soldermask to Pad Size ratio, and just letting the Manufacturer decide the Soldermask Swell required.
Alexander Quilty's user avatar
3 votes

Cadance to Altium Conversion - Is it Hard?

I have performed this very conversion on multiple occasions. The conversion is the easy part, and Altium is able to pull in the design within a matter of minutes. The tedious part, however, is ...
DerStrom8's user avatar
  • 21.4k
3 votes

How do I modulate the output power of a laser diode at 1 kHz?

I've taken this graph from the specification sheet linked to on this page and added the green box: - The green box represents where the laser actually produces a laser light output. Point to note: ...
Andy aka's user avatar
  • 464k
2 votes

How do I modulate the output power of a laser diode at 1 kHz?

You should drive the diode with a variable current source circuit. The laser has a monitor diode mounted to the back side of the emitter in order to monitor output power. You can connect the monitor ...
John D's user avatar
  • 24.1k
1 vote
Accepted

Ground plane for SMPS EMI-Filter?

A ground plane is a reference plane. Anywhere the reference changes, a new ground plane is appropriate, as well as decoupling or isolation between any planes that should share connections. Here is an ...
Tim Williams's user avatar
  • 39.1k

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