https://community.element14.com/products/pcbprototyping/Join members as we design, prototype and fabricate printed circuit boards, for fun and for practicality!en-USTelligent Community 12https://community.element14.com/products/pcbprototyping/f/forum/56880/logic-gate-output-changes-when-nearby-relay-activates/235248Thu, 30 Apr 2026 20:54:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:cc267f10-ad80-4576-98f1-845f77eb6db9DABNever underestimate the value of metal shielding. Also, ferrite cores can be very useful in reducing induced spikes.https://community.element14.com/products/pcbprototyping/f/forum/56880/logic-gate-output-changes-when-nearby-relay-activates/235197Tue, 28 Apr 2026 12:52:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:cdde6fe5-04e8-45d5-a226-6ee55e57361ccolporteurI've experienced the interference from relays in digital electronics. The components don't even have to be on the same board. Mostly working with Arduino's and raspberry pi. My fix was to code to simulate key bounce. relay contacts under heavy load do tend to generate emf. Its never seems to be good for the contacts and the surround environment. I can give you empathy but not a practical solution.https://community.element14.com/products/pcbprototyping/f/forum/56880/logic-gate-output-changes-when-nearby-relay-activates/235173Mon, 27 Apr 2026 13:05:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:41d78de0-634b-431c-a9a0-1cb7f5102b14robogaryDepends. Is the relay switching an inductive load ? If possible, you could remove the relay's load and cycle to see if that is related to misoperation. Relay coils should have a flyback diode (or a shottkey double back diode tvs) unless it effects any critical timing. Larger coils should also have RC suppression. If your relay switches an inductive load like a motor or solenoid, that load should also have suppression. The suppression will also ensure the relay contact life.https://community.element14.com/products/pcbprototyping/f/forum/56880/logic-gate-output-changes-when-nearby-relay-activates/235167Mon, 27 Apr 2026 08:21:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a6e4deea-29a9-465b-ad91-03268fd8d8c7acdc90is the gates powered on 5volts is the relays on 5v or 12v does the relay have diode across coil can we have a circuit ?https://community.element14.com/products/pcbprototyping/f/forum/56880/logic-gate-output-changes-when-nearby-relay-activatesMon, 27 Apr 2026 08:08:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:e2289307-38fd-4dcc-b623-03221cc79360eva_402Hi, 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?https://community.element14.com/products/pcbprototyping/f/forum/56848/thermal-profile-methodology-for-diy-reflow-what-i-know-what-i-m-missing/235000Thu, 16 Apr 2026 16:53:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:3b594d19-2920-4c7a-8935-b9fcb6774b6dBigGAn idea I had (needs effort to explore practical implications) is to place a layer of densely packed steel wool between the plate and the board to allow for warping and to provide a more even heat distribution. The thermal conductivity of steel wool will certainly be better than air but not as good as a solid metal plate.https://community.element14.com/products/pcbprototyping/f/forum/56849/how-to-position-an-smt-stencil-at-home/234987Wed, 15 Apr 2026 11:06:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:49018fa8-b848-43ea-be65-f011210363b3pvitI just imagine squeegee path and keep pins aside. There are 4 corners. 2 pins required. Usually enough variants to select from. From my experience, the only real problem is to position SMT stencil with ease and high precision. Everything else is not a big deal. Also, dry paste (high viscosity) is a bit more convenient, but difference is not fatal.https://community.element14.com/products/pcbprototyping/f/forum/56849/how-to-position-an-smt-stencil-at-home/234984Wed, 15 Apr 2026 10:02:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:ead28991-0245-4b2f-a1eb-93d3166de26aBigGGood idea. I'm just wondering whether these pins will impinge on the solder application process. You typically apply solder paste on the stencil and then scrape across with a card etc.https://community.element14.com/products/pcbprototyping/f/forum/56849/how-to-position-an-smt-stencil-at-home/234983Wed, 15 Apr 2026 09:32:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:19f67220-44be-42d6-9126-23006a8e1fe7Andrew JI just tape the PCB down to a board along as much of all 4 edges as possible so that it doesn’t move. With the stencil, I place a long piece of tape along one side. The stencil is positioned on the PCB so it is properly aligned then the stencil’s tape is pressed down onto the board (not PCB) and that allows the stencil to (a) not move whilst scraping paste across it; and (b) provides a hinge for lifting it off without disturbing paste. It also allows the stencil to be lowered back down if you’ve missed some paste or could do with more on some pads. Never had an issue with this approach.https://community.element14.com/products/pcbprototyping/f/forum/56849/how-to-position-an-smt-stencil-at-homeWed, 15 Apr 2026 06:49:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:da8f061a-942a-40f2-8897-db23057a68b6pvitThis 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.reflowsolderingstencilhttps://community.element14.com/products/pcbprototyping/b/pcb-blogs/posts/kicad-10-and-spice-practical-tips-for-working-with-circuit-simulationsTue, 14 Apr 2026 19:28:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:8d6fc18b-7319-460a-a78a-87edf803c52bshabazTable of Contents Introduction What is SPICE and How it is Used with KiCad? Simulations and PCB Design with One Schematic Sharing Circuit Simulations Easier-to-Read Charts Summary Introduction KiCad software enables the user to create circuit schematics and convert those into printed circuit board (PCB) layouts, all ready for manufacturing, whether that’s for hobby or commercial use. A lesser-used feature of KiCad is its SPICE circuit simulation capability. I explored it a while back (+) KiCad 8: Working with Circuit Simulations! - element14 Community however I felt it is useful enough that it was worth retrying it with the recent KiCad 10 software release. In particular, I wanted to see if I could now figure out some methods (perhaps not best practices - I don't know!), to make simulations more usable and accessible. In particular, I wanted to be able to easily share simulations with others, and to be able to create circuit boards from the same schematic that was being simulated. This blog post discusses how to do that, and also how to obtain slightly easier-to-read charts from simulation results. What is SPICE and How it is Used with KiCad? SPICE is a circuit simulation engine that KiCad uses. For more information, please refer to (+) SPICE Circuit Simulation: A Simple Explanation! - element14 Community and then to see how to use it specifically with KiCad, the earlier version 8 blog post can be used, it is still relevant: (+) KiCad 8: Working with Circuit Simulations! - element14 Community Simulations and PCB Design with One Schematic Often, just a subcircuit is simulated, rather than the entire project. A separate project or a separate schematic file could be created in KiCad, with just the parts you wish to simulate copied across from your real project that you wish to eventually construct with a real circuit board. Another approach is described in the earlier version 8 blog post (in particular in the comments section there), where the entire schematic is split up into sheets, and the top level sheet is not simulated, but any of the lower-level sheets can be simulated if desired. Yet another approach is to mark some components as excluded from simulation. With KiCad 10, that approach leaves boxes drawn around those components, which looks ugly. There may be a solution to that, but I have worked around it for now, by simply assigning benign “fake” SPICE models to the components that I do not wish to be simulated (usually connectors). Here’s a SPICE model example, which I called AUDIOJACK_STEREO.lib, which was intended for a 3.5 mm audio connector with three pins called SHIELD, RING and TIP: .SUBCKT AUDIOJACK_STEREO SHIELD RING TIP R1 SHIELD RING 1e12 R2 SHIELD TIP 1e12 .ENDS AUDIOJACK_STEREO All it does is simulate two very high resistance (1e12 ohms) between the shield and the other pins. Another problem that needs to be resolved, is that you might not want the SPICE-related stuff to clutter the schematic. To keep it clean, I rely on signal labels to attach connections to SPICE elements, and that way there’s no wires visually cluttering things. I can then push off all the SPICE related stuff into a corner of the schematic sheet. See the example screenshot below. You’ll also notice a very small resistance of 0.000001 ohms present in the circuit! I used that to tie the SPICE ‘ 0 ’ symbol to the 0V rail in the circuit. Don’t connect the signals directly, because that causes KiCad to swallow the 0V connections, and then if your PCB layout had a 0V ground plane, it would disappear. A very low value resistor solves the problem. The resistor must not appear in the PCB since it’s just there for simulation purposes, so right-click on it and select Attributes->Exclude from Board , and Exclude from BoM . Sharing Circuit Simulations If you give someone else your KiCad project folder, they will not be able to easily simulate themselves, because the SPICE libraries are not local to a project. Their PC likely won’t have the SPICE libraries that you downloaded. Technically it is possible to 'embed' the SPICE model within KiCad symbols, but there are some limitations (not easy to view the model, and it gets dynamically saved I believe, with a mangled filename which is inconvenient, plus there's a KiCad 10 issue currently that can make you lose the embedded model). The only reasonably solution I could come up with so far, is to create a folder within the project folder, called say spice_lib , and then copy the SPICE libraries that were used into that folder, and then change each component in the schematic to point to the relevant model in that local folder, rather than wherever one normally stores models. That can get tedious to do manually, so I used AI to help write a spice_lib_local graphical tool to automate things. Here's a 4-minute video explanation: https://youtu.be/VLH2petuyxM When run, the user can select their project folder, then select the schematic, and click Analyze to see what SPICE models are present inside that schematic. Another button-click will automatically copy those models into the local spice_lib folder, and then by clicking on the Make Instances Local button, the tool will modify the schematic file to point to the local SPICE models. After that, the project folder can be shared with others, and they will be able to run the simulations. Easier-to-Read Charts Personally, I don’t like the charts that KiCad generates from simulations; the values on the axes are tiny, and not easy to read. One solution is to use some other charting application, because the results can be exported from KiCad in a CSV format. For TRAN and AC analyses (i.e. time-domain and frequency response simulations), I wrote a couple of simply Python scripts called plot_tran.py and plot_ac.py to show the results better. They could be tweaked to suit needs. The screenshots below show how to run the scripts, and example output. Summary Simulations run well in KiCad 10, but you may need to consider how to best draw the schematic if you want to separate out the things that need simulating, from the parts that are not to be simulated. Some techniques for that were discussed, and a simple way for smaller circuits could be to use SPICE models that do nothing (with very high resistances) for things like connectors. For connecting a ground net to the “0” symbol that is used by SPICE in KiCad, a very low value resistor can be used. To share circuits with others, it is worthwhile to store SPICE models locally within the project folder (or a sub-folder, say called spice_lib) so that they are available to anyone else who receives the project folder. An automated tool to perform the copy operation, and to modify the schematic file to use the new path to the models was discussed. KiCad supports SPICE results export in CSV format, and that can be used to plot results with custom or third party tools. Thanks for reading!kicad 8kicadsimulationspicekicad 9kicad 10https://community.element14.com/products/pcbprototyping/f/forum/56848/thermal-profile-methodology-for-diy-reflow-what-i-know-what-i-m-missing/234970Mon, 13 Apr 2026 18:51:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a73a218c-0109-4257-bea4-09f56b340695pvitYeah. Thin plate => bad heat distribution. Fat plate => slow cooling. I use Pi5 fan to blow from the bottom. It improves cooling speed 2x-3x until melting point reached . But that's still 1°C/sec. Something more serious will not fit device size. The cheat is to end profile graph on melting point instead of room temp, lol :).https://community.element14.com/products/pcbprototyping/f/forum/56848/thermal-profile-methodology-for-diy-reflow-what-i-know-what-i-m-missing/234969Mon, 13 Apr 2026 17:19:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:b615fcad-a1fb-40e9-a0af-a7e116cee40cwolfgangfriedrich[quote userid="121623" url="~/products/pcbprototyping/f/forum/56848/thermal-profile-methodology-for-diy-reflow-what-i-know-what-i-m-missing/234961"]Using a hotplate like this is very much affected by the heat transfer between plate and board. It is necessary to press the board down on the hotplate since it will almost certainly warp as it heats up.[/quote] This is probably the most important point to make a hot-plate work, at least when frying larger boards.https://community.element14.com/products/pcbprototyping/f/forum/56848/thermal-profile-methodology-for-diy-reflow-what-i-know-what-i-m-missing/234968Mon, 13 Apr 2026 17:12:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:b126004c-c175-4872-b608-0ff9049d7185wolfgangfriedrichWhen I did have my DIY hot plate, I recorded some temperature profiles. With just turning of and convection cooling, the down ramp was never as steep a decline as the required profile. And the up-ramp was basically linear if there is not enough power or too much mass to heat. (+) Arduino Hot Plate (2) - What's for dessert? - element14 Communityhttps://community.element14.com/products/pcbprototyping/f/forum/56848/thermal-profile-methodology-for-diy-reflow-what-i-know-what-i-m-missing/234965Mon, 13 Apr 2026 14:36:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:eca3137d-7e25-45f7-92e5-1156844cdc20pvitIn current configuration the ramp up is ~ 1°C/sec in high point. Cool down ~ 1°C/sec until go below TAL, then become slower and very slow at room temp.