First PCB for a beginner, where to start? - Page 1
Forum section: electronics / beginners

author: JLynch
author_rank: Contributor
timestamp: July 26, 2021, 01:36:38 pm
content: Hello, looking to make my first PCB and not sure where to start. I’d appreciate any guidance on what might be the best PCB design package for a beginner.I’ve have things hobbled together on a breadboard and while things are pretty much working many questions remain including how to properly layout the circuit, selecting components the PCB manufacture has available and what’s the best software to use.Thanks.

author: MarkF
author_rank: Super Contributor
timestamp: July 26, 2021, 02:57:10 pm
content: What operating system are you using?For Windows, I have found that DipTrace is very intuitive to me.Download 'Freeware' here.You can enter your circuit into the 'Schematic Editor' and then from the File menu 'Convert to PCB' to layout your PCB.Or you can just insert components directly into an empty PCB from the 'PCB Layout Editor'. The PCB Layout Editor can also display a 3D-View of your PCB so you can get an overview of space usage. (I get extra 3D models from3D ContentCentral. You will need to create an account, which is also free.)The 'free' version can do two layer PCBs and 300 pins. I was able to layout my first PCB in one afternoon.A lot of people on the forum likeKiCAD. I've never been a big fan of it.These are the two most popular free software tools.

author: TheAmmoniacal
author_rank: Unknown
timestamp: July 26, 2021, 03:18:28 pm
content: EasyEDA is quite nice for getting started, also Fritzing if you can find a free download now (they want 8 euros now).DipTrace is quite intuitive if you're on Windows and more powerful than the two mentioned above.

author: JLynch
author_rank: Contributor
timestamp: July 26, 2021, 04:24:16 pm
content: Thanks for the suggestions, and have both Windows 8.1 and Windows 10 available.I'll give them a try and see how things go, thanks again.

author: tooki
author_rank: Super Contributor
timestamp: July 26, 2021, 04:52:06 pm
content: Another vote for EasyEDA. It's surprisingly capable and speedy for a web-based tool (an offline version is also available), and it really is easy to use.

author: JLynch
author_rank: Contributor
timestamp: July 26, 2021, 06:14:58 pm
content: I created an account in EasyEDA and started to layout my design and it does seem to be quite easy to use. However being new to all of this I’ve sort of run into another stumbling block.My circuit is quite simple with only a handful a main components. Power comes from a USB type-B connector going to a 3.3v regulator. Then there’s a Bluetooth module and an H-Bridge driving a brushed DC micro motor.When prototyping and stuffing components into my breadboard I find myself making use of these tiny little pre-built modules instead of individual chips. Now that I’m looking to build a PCB I need to ditch these modules along with all there supporting components - caps, resisters, diodes and whatever.In prototyping I used a DRV8833 H-Bridge module, picture below, and it has a couple supporting components on the board - caps and resistors and such. What I don’t see is any back EMF protection for the motors.Reading the DRV8833 datasheet it talks about a lot of protection but nothing specific to EMF.“Internal shutdown functions with a fault output pin are provided for overcurrent protection, short-circuitprotection, undervoltage lockout, and overtemperature.”I’m not sure if the overcurrent protection mentioned in the datasheet includes back EMF or not, does anyone know if I need to add flyback diodes in my circuit when using the DRV8833.Also included a simplified block diagram of my circuit and once I’ve got the circuit drawn in EasyEDA I’ll share that as well.

author: tooki
author_rank: Super Contributor
timestamp: July 26, 2021, 06:36:56 pm
content: The little Chinese modules tend to have the most absolute bare-bones implementation that will work, not one compliant with manufacturer recommendations. (So they may not be as resilient or reliable as they could be.)That IC happens to be a TI part, and TI is great about having EVMs (evaluation modules) for which they also provide the schematics, and reference designs (for products) that show the parts integrated as systems with other parts, for which they provide schematics and often PCB design files, etc. Take a look at the EVM for the part and do what it does, or if the part data sheet has a recommended PCB layout, follow it (as it will often have real-world values).In the case of the DRV8833, the datasheet doesn't mention back EMF diodes, nor does the EMV schematic include them (and the EMVs tend to be balls-to-the-wall designs to let you push the component to its limits, so they include everything up to the kitchen sink), so I'd say it conclusively does not need them.

author: JLynch
author_rank: Contributor
timestamp: July 26, 2021, 08:50:35 pm
content: Tooki, thanks for the help with the EMF question and also for the great advise on TI’s evaluation modules. Nothing beats being able to see examples of chips used in real circuits from the manufacturer.

author: james_s
author_rank: Super Contributor
timestamp: July 26, 2021, 09:34:07 pm
content: KiCad is pretty much the standard these days for the hobby and pro-sumer market, it's free and quite powerful. There is a bit of a learning curve but it isn't that hard, most EDAs use more or less the same workflow. Draw the schematic, create a netlist, lay out the PCB.

author: JLynch
author_rank: Contributor
timestamp: July 27, 2021, 01:52:16 am
content: While drawing schematics in EasyEDA seems quite straightforward I’ve found selecting components rather confusing, perhaps I’m going about it the wrong way.I’m looking for a complete solution where I can send out my design and have completed PCB’s returned with all it’s components soldered in place yet a vast majority of parts I’ve searched for in the EasyEDA library seem to be out of stock or unavailable for JLCPCB production.Is there a way to use / configure the parts library to only show what’s in stock and available?

author: themadhippy
author_rank: Super Contributor
timestamp: July 27, 2021, 02:02:16 am
content: QuoteOr treat the module as a component and make a footprint for it and use suitable headers to join your pcb to the module.

author: james_s
author_rank: Super Contributor
timestamp: July 27, 2021, 05:20:41 am
content: There are a lot of component shortages going on right now, you're likely to have a lot more problems with parts being out of stock than would be normal.

author: tooki
author_rank: Super Contributor
timestamp: July 27, 2021, 03:35:40 pm
content: Quote from: JLynch on July 27, 2021, 01:52:16 amIt has the double-edged sword of user-created component symbols/footprints. On the one hand, it often makes it a lot quicker to find what you need, especially for the components favored by hobbyists. The downside is that the symbols/footprints may not be well drawn. (Though errors happen on manufacturer-provided in symbols/footprints, too.)I strongly suggest learning to make your own footprints, as it's often faster than hunting down the right one and carefully verifying its correctness. EasyEDA's symbols will be fine for jellybean parts, though, and their SMD footprints are well-made and follow a careful naming system, so even if you have to make your own symbol, for most things you can use an existing footprint.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 27, 2021, 03:49:46 pm
content: Here are two sources of footprints:https://www.snapeda.com/https://www.ultralibrarian.com/I believe EasyEDA can import from several of the other programs named.BTW: I have used one of those programs to get an idea on occasion, but always use either the Eagle footprint or draw my own. In Eagle, one can set the grid to facilitate getting things in the right place. I assume Easy EDA has the same capability.

author: fourfathom
author_rank: Super Contributor
timestamp: July 27, 2021, 04:08:56 pm
content: Quote from: jpanhalt on July 27, 2021, 03:49:46 pmYou can also set the grid and measurement units in KiCad -- both for component footprint creation and for board layout. In fact, you can switch back and forth as you like during the process.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 27, 2021, 04:22:47 pm
content: Likewise on Eagle. It's a little cumbersome using dropdowns, but I set up hotkeys to facilitate it -- named "Toggle Grid" (F6) and "Grid Setting" (F5) on my keyboard.

author: james_s
author_rank: Super Contributor
timestamp: July 28, 2021, 01:10:02 am
content: Unless you already know Eagle and use it, there's no point in learning it IMHO, ever since going subscription it is effectively dead, the hobbyist/maker community abandoned it en-masse.

author: admiralk
author_rank: Regular Contributor
timestamp: July 28, 2021, 02:00:18 am
content: Quote from: tooki on July 27, 2021, 03:35:40 pmIt might seem a pain at first, but after making a couple you will stop looking past the datasheet for new measurements. The same can be said for components. The pins on ICs always need to be in a different place every time I use them in a schematic. Sometimes even for the same IC in the same schematic.

author: perieanuo
author_rank: Frequent Contributor
timestamp: July 28, 2021, 06:00:58 am
content: diptrace is fine, they give also non-bussines licenses if you ask them, eagle is fine too (on library side, you can find anything for beginner-level components for eagle and altium for example)kicad etaetera, those are toys. i even manufactured 2-sided boards with eagle pro license, for quick projects altium is overkill to learn, but if you wanna go pro, start with something simple like i mentioned, then move to altium

author: tooki
author_rank: Super Contributor
timestamp: July 28, 2021, 07:42:32 pm
content: Quote from: admiralk on July 28, 2021, 02:00:18 amI don’t understand what you mean.Quote from: admiralk on July 28, 2021, 02:00:18 amHuh? You redraw IC symbols for each schematic?

author: admiralk
author_rank: Regular Contributor
timestamp: July 29, 2021, 11:29:10 pm
content: Well you have standard packages, so you do not have to make new footprints for everything. Datasheets give a recommended footprint and once you have done a couple, it is usually quicker to just get the measurements from the datasheet than it is to find one that is correct, and works in whatever program you are using.It just takes a couple seconds to redraw a symbol. Just move the pins where you want them and adjust the outline, if needed. For example, in the attachment, I flipped the top and bottom pins on one of he 74LS373 so I could stack them and not have wires running all over the place. It is much neater to move a couple pins than have wires crossing.

author: tooki
author_rank: Super Contributor
timestamp: July 30, 2021, 03:12:29 pm
content: Quote from: admiralk on July 29, 2021, 11:29:10 pmWell yes, but the thing that confuses me is you saying “…looking past the datasheet for measurements.” Getting footprints elsewhere is one thing, but I don’t know where else other than the datasheet one would searchfor measurements.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 30, 2021, 03:27:21 pm
content: Quote from: tooki on July 30, 2021, 03:12:29 pmThe whole phrase is, "you will stop looking past the datasheet for new measurements." That means to me, stop at the datesheet and don't look elsewhere for measurements.I might add that some manufacturers, e.g, Microchip, put their recommended footprints in a standalone catalog,https://www.microchip.com/en-us/support/package-drawings.

author: tooki
author_rank: Super Contributor
timestamp: July 30, 2021, 04:43:21 pm
content: Quote from: jpanhalt on July 30, 2021, 03:27:21 pmYes, I understand the words, but I’m puzzled at what the alternative to the datasheet (or official manufacturer document like the one you mention) would be. To me, using the datasheet for measurements is obvious, so you need to spell out for me what the alternative to be avoided is, because I can’t think of any.

author: fourfathom
author_rank: Super Contributor
timestamp: July 30, 2021, 08:47:23 pm
content: Quote from: tooki on July 30, 2021, 04:43:21 pmAlternatives:The KiCad libraries, SnapEDA.com, Ultralibrary.com, mouser.com/electronic-cad-symbols-models/, etc, etc.If I use one of these sources I still need to check the dimensions. I do build my own footprints from time to time, using the datasheet measurements.

author: admiralk
author_rank: Regular Contributor
timestamp: July 30, 2021, 09:49:38 pm
content: @tooki - Now I understand your confusion. I think two thoughts were running trough my head when I typed that. It should have been simply,QuoteAnd as fourfathom pointed out, the alternative is to search for prebuilt patterns.

author: JLynch
author_rank: Contributor
timestamp: July 31, 2021, 12:32:14 am
content: About ready to place my order and I was able to locate all but three components for my board and taking some of the advice from above I created my own footprint for one of the parts.One of the three I couldn’t locate is a through-hole part while the other two are surface mount. One of the two surface mount parts has large pads and shouldn’t be a problem soldering, same goes for the through-hole part. Only the one surface mount with very tiny pads is going to be a challenge.Question, in laying out traces I started with the Auto Route function and then cleaned up / adjusted everything by hand. I’m using a USB Type-B connector for power which has 4 circuit related pins and two larger ones for securing it to the board. The Auto Route function created an isolated trace (connected to nothing else) between these two ‘fastening’ pins and the software gets mad when it’s removed.I assumed that the metal ‘shell’ of the USB connector should be grounded but when doing so it seems to conflict or interfere with this isolated trace created by Auto Route resulting in a DRC error.So not sure why Auto Route created this trace and why it’s causing a DRC error when replaced with a ground connection. So now I’m questioning whether or not to ground the ‘fastening’ pins of the USB connector of just leave the original Auto Route trace alone.

author: fourfathom
author_rank: Super Contributor
timestamp: July 31, 2021, 03:57:06 am
content: I have the shell of my USB-C connector tied to the groundplane, and the schematic symbol includes these shell pins. Most of the groundplane around the connector and transient suppression diodes has isolation "no-fill" groundplane cutouts, to keep transient spike current local to the connector and not spreading out into the rest of the board.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 31, 2021, 10:54:46 am
content: Quote from: JLynch on July 31, 2021, 12:32:14 amI use Eagle, but assume the same will apply to your situation. As previously stated by fourfathom, there may be an assumption they are connected to ground. That should be evident in the component drawing.If you want them independent of ground and each other, one way is to rename them in the component so they are not connected (assuming you are using something equivalent to the Eagle "pad") to solder to. A more complicated way would be a plated slot (assuming that is the correct geometry). In Eagle, doing that more complicated. I believe with your program, it is relatively easy, and the procedure is described on the vendor's site.If they are not "ground" and there is a ground pour, there will be an isolation ring around them.Here's an example of a similar application in which I use the USB for power :Note, they are included in the ground pour.

author: fourfathom
author_rank: Super Contributor
timestamp: July 31, 2021, 05:26:33 pm
content: Here's the USB-C layout (KiCad) I mentioned above:

author: JLynch
author_rank: Contributor
timestamp: July 31, 2021, 06:28:43 pm
content: Thanks for the help with the grounding question and the pictures you guys sent. Kind of figured the USB shell should be grounded just didn’t understand why EastEDA was complaining and honestly still confused about how it handled things.There was just no way to clear the DRC error when adding USB grounds to the PCB and keep the rest of the layout work I had done. No matter what I did EasyEDA wouldn’t allow any traces to be added / connected between the metal USB shell and ground. The only way to clear the DRC errors was to scrap the PCB layout and regenerate it from an updated schematic with grounds already added to the USB shell.

author: admiralk
author_rank: Regular Contributor
timestamp: July 31, 2021, 06:37:29 pm
content: No option to just update from schematic?

author: jpanhalt
author_rank: Super Contributor
timestamp: July 31, 2021, 08:02:58 pm
content: @JLynchIf your are sure everything is ok, but EasyEDA still puts a track where you don't want it, with Eagle, you can rip the track up (i.e., convert to airwire) and make your Gerbers. I don't think airwires are included. If worried, just hide the airwire layer.

author: JLynch
author_rank: Contributor
timestamp: July 31, 2021, 10:26:56 pm
content: Way new to all of this but couldn’t find any option to ‘Renew’ layout from the schematic, sure does sound like a nice feature to have though. As for deleting or turning the unwanted trace into ‘airwire’ wasn’t really the problem. EasyEDA appeared to have created a rule that prohibited a trace from being connected to the USB shell and any attempts to do so were blocked. So while deleting the unwanted trace worked it brought up the DRC error, and trying to lay down a new trace was impossible. Again first time out with all of this so there’s a ton of stuff I could be missing or simply don’t understand.Schematic and PCB are done and sent off to JLCPCB, 5 boards, 2 assembled including shipping $34.00. Right now waiting for design approval and the estimate says I should have them in 4-7 business days.Actually the $34 dollars was a second round go at submitting the PCB, the first try was closer to 50 bucks which is when I learned the importance of using ‘basic’ parts whenever possible. Swapping out a couple of the Extended items brought the price down considerably.

author: tooki
author_rank: Super Contributor
timestamp: July 31, 2021, 11:41:20 pm
content: Quote from: fourfathom on July 30, 2021, 08:47:23 pmThose are sources forfootprints, notmeasurements.And this much earlier reply of mine clearly makes obvious that I understand the concept of (and pitfalls of) premade footprints:Quote from: tooki on July 27, 2021, 03:35:40 pmMy question was “what sources ofmeasurements(not footprints!)are there other than the datasheet?”, since the claim as written was to stop looking “beyond the datasheetfor measurements”. (It wasn’t “stop looking beyond the datasheet for footprints.”)

author: tooki
author_rank: Super Contributor
timestamp: July 31, 2021, 11:44:54 pm
content: Quote from: admiralk on July 30, 2021, 09:49:38 pmIf, as it seems, you mean simply “I always draw my own footprints from the dimensions in the datasheets instead of using premade footprints”, why not just say “I always draw my own footprints from the dimensions in the datasheets instead of using premade footprints”?!?So with that in mind, I remain just as puzzled by your original reply to me as in the beginning. I said I recommend drawing your own. You replied that I should “stop looking beyond the datasheet for measurements”. If you meant I should stop looking beyond datasheets forfootprints, isn’t that just repeating what I said, except using the wrong terminology?!? (So why admonish me to do what I’m already doing?) And if that’snotwhat you meant, then my question stands: what sources exist for measurements (NOT PREMADE FOOTPRINTS) other than datasheets?!?As Ms. Swan from MadTV always said: “say what you mean and mean what you say!”

author: tooki
author_rank: Super Contributor
timestamp: August 01, 2021, 12:07:47 am
content: Quote from: JLynch on July 31, 2021, 10:26:56 pmOf course it has it, that being a fundamental feature of an EDA program.If you’re in the schematic, it’sDesign > Update PCB(Alt+U)If you’re in the PCB, it’sDesign > Import Changes(Alt+I)

author: fourfathom
author_rank: Super Contributor
timestamp: August 01, 2021, 01:45:19 am
content: Quote from: tooki on July 31, 2021, 11:41:20 pmI checked back a few posts, and you were responding to a question about footprints, and admiralk mentioned measurements -- meaning measurements of the footprint dimensions. You then asked about potential sources for measurements. I, and apparently everyone else, assumed you were still talking about footprint measurements.If you want package dimensions, some of those sources I mentioned also have 3-D models, and sometimes these are quite accurate. Sometimes they are more generic.

author: jpanhalt
author_rank: Super Contributor
timestamp: August 01, 2021, 09:36:06 am
content: Footprint versus measurements seems almost a distinction without a difference. When in the "footprint" (aka package in Eagle) editing mode, every line, pad, or feature will have the coordinates and usually dimensions available (e.g., dimensions of a pad are given as well as its coordinates).It is really quite simple to convert those coordinates back to dimensions; however, when I edit or draw a footprint, I often use the coordinates for accurate positioning. For example, assume you have several pads to place symmetrically around a chip. It is easy to do with the grid or by coordinates as the coordinates are to the center of each pad. Moreover, when one imports a "footprint" as a DXF file, you can align it using the grid or in a single step using the coordinates and a command line.In fact, there was a recent thread here asking why used dimensions at all:https://www.eevblog.com/forum/chat/do-tables-of-xy-coordinates-tarnish-the-souls-of-engineers/msg3487310/#msg3487310

author: fourfathom
author_rank: Super Contributor
timestamp: August 01, 2021, 03:16:30 pm
content: Since tooki was getting all frustrated with our replies, I suppose that he/she was actually asking about package dimensions. Yes, the terms are fairly non-specific.

author: tooki
author_rank: Super Contributor
timestamp: August 01, 2021, 08:13:08 pm
content: To me, measurements or dimensions means the sizes and distances and positions of things (in units like mm or inches), as typically foundinthe package drawing in a datasheet.To me, in the context of EDA software (which this is) the “footprint” means the complete digital representation, in the EDA program, of the PCB features (pads, holes, etc) needed to mount the part.One would use the measurements/dimensions/datasheet drawing to create the footprint in the EDA software.The footprint is linked to the component’s schematic symbol so the software knows which signal goes to which physical pin.My frustration with your (plural) replies is indeed because you both seem to be very, very, very sloppy with your terminology (and happy to be sloppy). Many terms actuallyarespecific, which is why it’s confusing to others when you use them in a nonstandard way. (I worked for years as a technical writer, and one key thing in technical writing is to use terminology consistently and precisely. That means not using multiple terms to refer to the same thing, and not using the same term to refer to multiple things. This discussion is a textbook example of why this is a cardinal rule in technical writing.)

author: jpanhalt
author_rank: Super Contributor
timestamp: August 01, 2021, 08:26:29 pm
content: @tookiTroll. I refuse to address it further.

author: admiralk
author_rank: Regular Contributor
timestamp: August 01, 2021, 09:22:45 pm
content: Quote from: tooki on July 31, 2021, 11:44:54 pmI was not replying to you. I was seconding what you said, and trying to add a little to it.

author: tooki
author_rank: Super Contributor
timestamp: August 02, 2021, 02:14:00 pm
content: Quote from: admiralk on August 01, 2021, 09:22:45 pmOh. But youdidreply to me, by quoting what I said.In such cases, it’s wise to preface the reply with “I concur: …” or similar to make it clear you’re expanding on it. In context, it did not appear to be in agreement.Quote from: jpanhalt on August 01, 2021, 08:26:29 pmIt’s your prerogative to not discuss it further. However, “trolling” has a specific meaning, and even heated discussion doesnotconstitute trolling. Trolling means to be deliberately offensive and provocative, for the purpose of creating artificial discord. Frustration at a very real misunderstanding doesnotconstitute trolling, so it’s unfair to make such a false accusation.