PCB Forum - Recent Threads

Logic Gate Output Changes When Nearby Relay Activates

eva_402 — Mon, 27 Apr 2026 08:08:51 GMT

Hi,
I’m using a few AND/OR logic gates to generate enable signals before they enter a microcontroller. The logic works normally, but sometimes outputs change briefly when a nearby relay switches.

The relay and logic ICs are on the same board.

Questions:

Is this more likely EMI coupling or supply disturbance?
Should I add more decoupling or flyback suppression first?
On the PCB, is physical separation between relay components and logic ICs usually enough?

How to Position an SMT Stencil at Home

pvit — Wed, 15 Apr 2026 06:49:24 GMT

This is a positioning method that wasn't obvious to me until I'd tried a few other approaches. Sharing it in case it saves someone time.

The basic idea: use needles and fiducial holes to fix the stencil and PCB to a silicone mat. It's far more accurate and practical than building a makeshift frame with tape.

Use case

- Hobby use — assembling a few boards occasionally
- Open source projects where reproducibility matters (many people will build it)

What's out there

SMT stencil printers (full-size) — large, require dedicated space. Fine for production runs, overkill at home. Also needs a larger stencil, which drives up cost and shipping.
Compact stencil printers — appeared only recently. Much better suited for hobby use. Still somewhat large — might make sense for a dozen boards, but overkill for 1–2.
Fiducial hole positioning — has its nuances, but nearly ideal for hobby use. Unbeatable on price.

Hobby boards typically don't exceed 100×100 mm. In that case a steel stencil runs about $3. The question "solder by hand or use paste?" pretty much answers itself.

Worth noting: in "proper" stencil use the stencil doesn't touch the board — it snaps off during squeegee travel. With fiducial positioning the stencil lies directly on the board. In theory that's worse, but the results are good enough not to worry about.

How to do it

"Use needles and fiducial holes" sounds simple. In practice there are subtleties — needles come in different diameters, and repeatability matters.

For a long time I used AWG 22 steel wire with 0.7 mm holes:

Total offset no more than 0.1 mm
Sufficient for 0.5 mm pitch components

Downsides:

Still need to source the wire
Wire deforms when clipped, so zero clearance is impossible

On recent boards I tried something different. It turns out there are "location pins" at 1 mm diameter and smaller. At one well-known three-letter Chinese fab you can order them for pennies along with the boards. As shown in the photo, each location area has 4 holes — 0.6, 0.65, 1.0, and 1.05 mm — for 0.6 and 1.0 mm pins.

I went with 1.0 mm pins. Very happy with the results:

Pins drop straight into the board — no pushing into the mat
Zero play
Prints are even more precise. Multiple squeegee passes don't smear anything
Result does not depend on user experience

It's too early to call it 100% reproducible, but I've ordered boards this way three times with no issues. For extra safety you could add 1.05 mm holes next to the 1.0 mm ones, but I've never needed them.

If you know other convenient methods — share them.

Thermal profile methodology for DIY reflow — what I know, what I'm missing

pvit — Mon, 13 Apr 2026 00:22:40 GMT

Hi everyone. I built a compact reflow micro-table for hassle-free PCB assembly at home: Reflow Micro Table: Compact USB PD Reflow Table with Browser Control

I'd like to write a general guide on setting up thermal profiles, but I lack the practical experience to make something solid. I'm not talking about production-line requirements — more about "reasonably good" for advanced DIY.

What I know so far as hard constraints:

For RoHS/leaded: TAL no more than 60 seconds. For LTS — I'm not sure.
Ramp rate: 1–2°C/sec (except the start)
Cooling rate: ~4°C/sec; passive air cooling is acceptable (not sure about LTS).

Everything else seems to depend on the specific paste and equipment — recommendations vary widely. The bigger frustration is that datasheets give you a profile to follow but don't explain how much the parameters can actually vary. It's like the difference between a datasheet and a reference manual :)

A colleague with hands-on production experience described this simplified approach to me — I'd be curious whether it holds up in practice:

Ramp linearly at 1–2°C/sec
Wait until paste visibly melts across all components
Turn off immediately and let it cool

I'm keeping the scope to LTS and leaded — RoHS/SAC peak temperatures and tighter process windows are an unnecessary complication for beginners.

Questions

How important is a soaking plateau, and how does it depend on the paste type?
How long can components and the board stay above a given temperature before damage becomes a concern?
Is there a minimum time above liquidus required for proper intermetallic formation?
How critical is cooling rate — does the solidification speed affect joint quality, and what is generally preferable?
and so on...

I'd really appreciate input from people with real PCB assembly experience to help systematize the practical nuances — the goal is to put together beginner-friendly guidance on building reflow profiles from scratch.

I've also tried to document my limited experience with LTS pastes here: github.com/.../soldering_paste.md — feedback on what could be improved there would be much appreciated as well.

Protoboard Templates

Tekkromancer — Thu, 09 Apr 2026 00:26:50 GMT

Hi all! I'm fairly new to electronics. To aid in my journey, I created some printable templates to help me plan out my circuits on protoboards on good old pencil and paper. So far, I just have two, but I'll certainly add more as I continue.

I'm happy to share them with the community in the hope that others will find them useful.

https://drive.google.com/file/d/1D_SknoozM5y2BAGld1N10K4CS7UIFK_e/view?usp=drive_link

Cheers!

Kicad 10 review

colporteur — Tue, 24 Mar 2026 17:54:49 GMT

Review shows promise for kicad playing with the bigger boys.

techexplorations.com/.../kicad-10-review-new-features-high-speed-tuning-variants-and-more

MP2172 step down switcher. Anyone have experience getting one going please?

davebullockmbe — Thu, 19 Feb 2026 17:11:56 GMT

Hi everyone,

I am struggling with a Monolithic Power MP2172 'buck' switching IC design.

The manufacturer's data sheet (page 15) shows a 'recommended' pcb layout but it is confusing as the picture has 'vias' that appear to be going nowhere?

It looks as though the layout is a double sided board as there are a couple of (coloured blue) tracks that must be on the bottom.
However there are 'vias' under the IC that appear to go nowhere unless there is a ground plane or other layer?
There are also 3 'vias' at the top of the OUT copper that don't make sense either, if there is no plane beneath.
So:-
I generated my own layout which was being added to a double sided board with a top and bottom side ground plane.

The 'switcher is to generate 2V dc from a single LiPo battery, I calculated the correct values for the FB divider and had my board made.
Sadly when populated the switching converter only produced 0.5V.
A quick 'scope around the IC found a 4 step staircase waveform on the SW pin, as though the IC was trying to start and failing.
Further investigation revealed my supply input decoupling was only 4.7uF instead of the recommended 2 x 10uF...doooh!
I replaced the capacitor with a 22uF and a 100nF in parallel which improved the situation by now producing 1.3V and a much larger 25 step staircase switching waveform.
However still not getting up to full operation.
I then tried drilling extra via holes next to the grounded end of the input decoupling capacitors and 'pinned' this point with a through wire to the GND plane on the bottom
layer, Thinking I had a high impedance GND or ground loop.
This stopped the switching completely!

I have since reworked my layout (below) making it as close to the recommended one, and, pared back the bottom layer ground plane from beneath the switcher.
But before I get a new board made I could do with advice from someone who has experience with this family of switching IC's and in particular the MP2172.

Please help if you can..:-)
Thanks in anticipation

Dave

Circuit Studio License recovery

ICBend — Wed, 11 Feb 2026 09:50:17 GMT

My PC died, I have installed Circuit Studio on my new PC but need to recover my stand alone license.

Can anyone tell me how to recover this

ESP32 works on breadboard but not on custom PCB

Oliver2003 — Tue, 13 Jan 2026 04:48:26 GMT

Hey everyone! I’ve run into a bit of a mystery with an ESP32 project. :// It runs perfectly while I’m prototyping on a breadboard, but as soon as I move everything over to a custom PCB, it starts acting up.... Sometimes it just refuses to boot, and other times I have to keep hitting the reset button or cycling the USB power just to get it to kick in. I’ve already double checked the schematic and continuity, so I’m starting to suspect that the issue might be hidden in my layout. I’m not 100% confident about my decoupling capacitor placement, or if my pull-ups on the EN and BOOT pins are quite right. I’m also wondering if I’ve got some noise or grounding issues around the USB UART interface that are messing with the startup sequence.

Has anyone else dealt with this works on breadboard but not on PCB headache with the ESP32?? I’d really appreciate any tips on common layout pitfalls or things I should double check before I order amother revision of the board. I’m more than happy to upload my schematic or PCB screenshots if anyone is willing to take a look. thanks in advance for the help!"

Sharing: EAGLE CAD Library for Raspberry Pi 5 (40-Pin Header)

alfadar — Sun, 28 Dec 2025 19:54:49 GMT

I’m sharing a custom EAGLE CAD (.lbr) library for the Raspberry Pi 5 40-pin GPIO header.

This library includes:

Schematic symbol with clean GPIO pin names (GPIO2, GPIO3, etc.)
Through-hole package (2×20, 2.54 mm header)
Fully mapped device (1:1 pin-to-pad mapping)
Clear pin-1 marking
Power pins split (3V3_1 / 3V3_2, 5V_1 / 5V_2, GND_1…GND_8) to avoid ambiguity in EAGLE

Notes

Compatible with Raspberry Pi 2 / 3 / 4 / 5 (standard 40-pin header)
GPIO aliases (I2C, SPI, UART) are documented in the symbol description
Intended for HATs, shields and educational projects

link - https://github.com/alfadar-cmd/xpto/blob/main/eagle/raspberry_pi_5_40pin_eagle.lbr

Get the CE mark for your open source project - we just made it a lot easier for makers.

mayermakes — Thu, 18 Dec 2025 16:48:09 GMT

We are launching the first Round of our group certification programm exklusively for #opensource Hardware!

apply with your project until january 31st! the more projects join, the lower the costs get for everyone. you can pull out until the very last minute , no application fees or any other shenanigans. We collect projects and calculate the price based on the actual work that need to be done to take advantage of the group approach , benefiting everybody!

Info page: early.smander.com/.../

Press release(EN/DE) here: early.smander.com/.../

this would not be possible without the support of the element14 community and our early maker, startup and business customers and the #maker community!

how to get a schematic and footprint of the RK3576

evo — Wed, 08 Oct 2025 17:33:51 GMT

hi, i am trying to get a schematic from lcsc to kicad but tools like easyeda2kicad doesn't work

KiCAD Schematic embed?

cstanton — Thu, 18 Sep 2025 14:49:48 GMT

https://kicanvas.org/embedding/

We're considering allowing support for KiCAD schematics on the community - interested?

Though we will wait until it's a bit more oven-cooked, we wouldn't want to open up to vulnerabilities:

[Please visit the site to access the poll]

Led applique murale 230v

sebdewouters — Thu, 11 Sep 2025 12:10:31 GMT

Bonjour,

Je dois réaliser un schéma et PCB pour un prototype d’une applique murale qui alimentera 2 x 15 Led’s avec une tension d’entrée en 230v.

Le modèle d’applique que je dessine en 3D ne me permet d’y placer un driver « tout fait » par manque de place.

Comme je souhaite un éclairage « fort », je compte me diriger vers des Led’s 5050 en 4000k.

Ma première question est : Est-ce le bon choix sachant que je n’ai pas beaucoup de place pour loger l’électronique et que je lis que les Led5050 chauffe beaucoup ?

Quelles Led utiliserez-vous ?

Le type de Led que je vais utiliser déterminera les valeurs des résistance/condensateurs, …

Merci pour votre aide

Luc

Existing old type LM324 based automatic voltage stabilizer circuit evaluation

hasan2015 — Mon, 11 Aug 2025 08:33:41 GMT

Hi there,
I wanted to build up a voltage stabilizer to study its performance.
I got a simple circuit diagram from online, perhaps someone design it without understanding the LM324 op-amp action.
This has made me curious because I wanted to know it works or not.

Take a look below.

The most obscure part is transformer TR1.
The main winding (taps A … E) is most likely a specific, commercial part; but without knowing the expected voltages (or turns ratios) of that winding and taps AND the smaller, isolated one (possibly another 18V, like TR2?), it simply cannot be fully functional.

The three relay drivers on the left side almost beg to be modelled as identical subsections, easily done with the information shown. Same with the High/Low cutout circuit on the right side.

I was trying to simulate this circuit in LTspice, here is the image. Kindly help me to match with the upper one.

Lets calculate the op-amp gain, and fault.

I will be waiting for your response and guidance and comment. Your similar suggestions are appreciable.

NB: DONT comment something that you are not sure about it, I might be silly for you.

Look for KiCAD symbol and footprint resource for an LoRa module

colporteur — Sun, 10 Aug 2025 01:29:52 GMT

A friend has asked me to design a PCB that uses this module.

I used the capitalized word that begins with F, to voice my frustration on having to create the symbol and footprint for the beast. I need to blow off my notes from two versions of KiCAD ago. Then I thought, maybe someone in the E14 community had done it already and is willing to share.

Anyone have KiCAD 8 resources for this module?

Questions about via-in-pad technology

Twilight-peng — Tue, 22 Jul 2025 08:17:05 GMT

Hello!

I'm new member of this community. Recently, I'm designing a compact RF module with a fine-pitch BGA. Thinking of using via-in-pad for space reasons, especially since some PCB manufacturers now offers it for free. So I want get some advice about it. Does anyone have experience with this? Are there any performance or DFM issues I should watch out for?

Thanks for any help

LED_matrix_mosfet_driver_10x10

user_476 — Mon, 21 Jul 2025 06:43:48 GMT

idea for a mosfet driver to control a powerful 10 x 10 LED matrix or led strips, implemented with IRLML6344 and IRLML6402 transistors
LED_matrix_mosfet_driver_10x10

The project is basic, for development who wants to develop it.The idea was dictated by the fact that there is a missing of such drivers on the market
Here is a version with added resistors

LED_matrix_mosfet_driver_10x10._with_resistors

KiCAD always crashes

FWissman — Sun, 20 Jul 2025 01:31:04 GMT

I’m trying to move from Eagle 9.6.2 to KiCAD 7.0.11 on my MACBook Pro (mid 2012), with Intel Core i7, running Catalina 10.15.7. I installed KiCAD using MacPorts and that seemed to work although it took hours. The terminal log doesn’t show any errors, exceptions, or failures.

I can only get this far: I have a folder with name.sch, name.brd, name.kicad_pro, and when I tried the PCB editor, ~name.brd.lck was made.

Everytime I try to either edit the schematic or PCB, KiCAD crashes as soon as I lift the button on my mouse.

I’m open for ideas. I am hoping I don’t need a new computer once I found MacPorts.

Thanks!

How to manage symbols with KiCad?

embeddedguy — Tue, 06 May 2025 07:48:21 GMT

I am using KiCad version 8.0 and use it to design PCB.

One of the questions that I could not find answer yet on the online documentation is how to manage symbols of the components that I am using in KiCad?

For example, if I am using 10 different components and I have .kicad_sym file for each of them, can I put them all at one place in a folder and just add (once) that folder to the path?

Currently, I do not see this for symbols. Though it is working for footprints.

For example, here is the list of symbols that Kicad has by default in one folder. Each one of them is added individually in Kicad.

Though some of these .kicad_sym has more than one symbols within them.

That's some (de)soldering skills

stanto — Wed, 23 Apr 2025 18:05:28 GMT

I didn't realise you can get literal solder balls?

https://youtu.be/aC0CI7pTptU

Not to mention upgrading a laptop GPU.

Prototyping PCB for Aftermarket Car HUD Display – Thermal and Noise Considerations?

ariajames_121 — Mon, 07 Apr 2025 18:32:15 GMT

Hi everyone, I'm working on an aftermarket Head-Up Display (HUD) system for vehicles, which taps into the OBD-II port and displays speed, RPM, and basic alerts on a transparent screen using a small projector. I'm currently prototyping the control PCB, which handles CAN communication, basic data filtering, and driving a compact display module. Since this will be installed on the dashboard area, I'm trying to factor in exposure to sunlight (heat), electrical noise from the vehicle, and the need for a compact layout. Has anyone here prototyped PCBs for in-car use, especially around noise filtering and thermal design? Any recommendations for layout techniques or materials at the prototyping stage would be a huge help.

Question LCD display storage

cloudff7 — Mon, 07 Apr 2025 12:46:21 GMT

Will long-term storage of years on a 3.5" IPS LCD display cause disorganization, confusion and slowness in the liquid crystals, dead pixels and loss of brightness and performance in the backlight LEDs?

PCB Design: Exploring New Ideas and Exciting Challenges

ariajames_121 — Sun, 16 Mar 2025 02:49:00 GMT

As someone passionate about electronics and embedded systems, I’m always looking for new ways to push the boundaries of PCB design. Whether it's creating compact, high-performance circuits or optimizing power distribution for efficient operation, each project brings unique challenges and learning opportunities.

Right now, I’m excited to work on a new PCB project integrating multiple sensors and wireless communication modules while keeping the design compact and power-efficient. The goal is to build a reliable and scalable solution that can be used for IoT applications, automation, and real-time data processing.

One of the most intriguing aspects of this project is refining the layout to reduce noise and interference while maintaining signal integrity. The use of dedicated ground planes, proper trace routing, and decoupling capacitors plays a critical role in ensuring stable performance. I’m also experimenting with different design software to see which offers the best balance between usability and advanced features.

Another key area I’m focusing on is thermal management. With increasing circuit complexity, managing heat dissipation effectively is crucial. Exploring techniques such as thermal vias, copper pours, and strategic component placement has been an exciting learning experience.

If you’re also into PCB design, I’d love to hear your thoughts! What are some of the biggest challenges you've faced, and what innovative solutions have worked for you? Let’s share ideas and push the limits of what we can create!

Autodesk Fusion has added Avnet's Free Reference Schematics and Supply chain insights.

e14phil — Sun, 09 Mar 2025 16:10:03 GMT

NEWS from Avnet and Autodesk Fusion

The Avnet Add-in for Autodesk Fusion Delivers Free Reference Schematics and Live Supply Chain Insights

Transform your engineering design process and maximize project efficiency. The app is an add-in to the Autodesk Fusion that transforms the engineering workflow by offering the tools needed to make informed decisions about designs and components in one place.

The app provides direct access to reference designs and schematics within the design environment. It ensures function, cost, and availability are aligned throughout the product lifecycle. It also provides design engineers with inventory access and expert engineering support to bring designs to life.

“With Avnet’s App, engineers gain unmatched efficiency—accessing schematics, optimizing workflows, and making component decisions in as little as three clicks,” said Chris Jackson, VP, Digital Strategy & Innovation, Avnet.

Enhance and streamline the engineering workflow with these three key capabilities:

A library of more than 1,500 curated reference designs, complete with schematics and block diagrams. The designs are downloadable and ready to integrate into Fusion projects. The library also includes symbols for key products, as well as the typical circuit that surrounds them. It is ideal for jumpstarting, refining or customizing designs. By leveraging these pre-designed resources, engineers can save time, reduce complexity and focus on innovation.

Cost and availability features that provide instant access to pricing and availability for components. These include BOM optimization tools powered by advanced algorithms to evaluate price, lead time, and lifecycle constraints. In addition, design engineers can collaborate directly with Avnet representatives to explore competitive pricing options and supply chain efficiencies. This ultimately ensures engineers can optimize budgets, reduce lead times, and select the best components for their needs.

Parametric search which simplifies component selection with advanced search capabilities. The app allows design engineers to find alternates and swap them with existing devices in their schematics. They can also compare components based on price, availability, and lead time with easy access to datasheets, symbols and footprints. With these tools, engineers can streamline workflows, make informed decisions, and deliver high-quality results efficiently.

For more than 100 years, Avnet has supported its customers and suppliers worldwide to activate the transformative possibilities of technology. Avnet moves customers from idea to product and product to market—and when it comes to taking users from design to manufacture. Avnet is the perfect partner for Autodesk Fusion.

To learn more about Autodesk Fusion or to sign-up for access to the plugin/app, please visit: https://www.autodesk.com/partners/design-manufacturing/avnet

What other features do you think should be added to AutoDesk Fusion?

Who uses Autodesk Fusion? Avnet have a free add-on for you to test!

cstanton — Fri, 22 Nov 2024 17:26:06 GMT

If you are familiar with common ECAD tools, you will have heard of Autodesk Fusion, aka Fusion 360.

The software is touted as "your entire manufacturing process by integrating CAD, CAM, CAE and PCB into a single solution allowing you to design and make anything."

It is also free for personal use.

Avnet would like you to test and give feedback for the Sourcing and Logistics Add-In for Autodesk Fusion, here's a quick run-down of the software introduced by our sibling community Hackster.io with Alex Glow:

www.youtube.com/watch

You can find the Avnet App for download on the Autodesk App Store.

There's also help documentation available.

General Usage Instructions - How to create a BOM quote:

Open the Schematic from the Projects tab.
Under AVNET TOOLS tab, click on COST & AVAILABILITY.
Click "Cost and Availability Analysis"
Click "Project Actions"
Then hit "Quote BOM"
Enter the required "PROTOTYPE QTY" and optional EAU QTYs
Hit SUBMIT
A list of Matched Parts appears with a detailed overview of each part number.

Feedback can be sent via e-mail to onlinesupport@avnet.com or I will collect comments on this thread and feed them back internally.

Note: This thread has intentionally been posted in two locations on the website due to how members sign up for groups. You may interact with either thread.