An Electronic Lead Screw controller using a Teensy 4.1

[WobblyHand]

I finally figured out how to import an older (no longer supported) DigiKey KiCAD V5.0 library and it's foot prints to KiCAD V6. Now that I have symbols and footprints for the Teensy 4.1, a bog standard 2N2222A, and an old school DIP20 74LVC245AN, I have a shot at making a board. I'll still have to fiddle around for some headers and connector things, but at least I can now create a schematic and start a PCB layout.

I did get a copy of Eagle, but didn't get very far with it. If I recall, it wasn't fully featured, but my memory may be ragged on that.

My biggest issue with KiCAD was the struggle to get the symbols and foot prints. (Oh, and the lack of documentation that matches the released version!) At least today, the symbol and foot print problem is solved for my board. Tomorrow, I will work on my schematic. It will be a new learning adventure.

I really want to have my boards made. I don't want to etch them myself. Did that in the old days. I want real plated through holes and power planes, because I remember how bad the "good old days" really were. Eyelets for vias were awful!

 

[devils4ever]

I'm trying to learn PCB design again. I did stuff like that in the 80's. The free tools sure have a steep learning curve. Mostly know what to do, but not how to do it with the existing software. Makes it frustrating to get started. Perhaps not strangely the documentation for the latest version hasn't been written. The old docs are wrong for the new version. I don't know why they released it if the docs aren't there at all. It means only power users or experts can use the software and no one else. A lot of the good free PCB tools are crippled to small numbers of components or layers. The completely free tools have incomplete libraries making it hard to get going. Going to have to soldier on through to get it done. Or hack something together. Rather have a board than a rats nest of wiring, but that's me.

I use Kicad for PCB design (it been a few years since I used it last). Like all CAD tools, it has a steep learning curve. I've done 2-sided PCBs with it and they came out great. It seems I spend more time creating parts/libraries than anything though.

 

[WobblyHand]

I use Kicad for PCB design (it been a few years since I used it last). Like all CAD tools, it has a steep learning curve. I've done 2-sided PCBs with it and they came out great. It seems I spend more time creating parts/libraries than anything though.

Having done PCB work in ancient times, we had parts librarians and people who did nothing but manage and create libraries and footprints, so I can understand that getting this data into the tool is and always will be a significant effort.

Had a minor break through last night in figuring out how to import some older libraries. The new libs have new parts which can be hard to acquire. Was able to successfully get libraries and footprints for the parts I have in my electronic scrap box. Started the schematic. Like CAD, it forces you to think about what it should look like before you start. And of course, I didn't do that!

The default settings are odd for a 4 layer board, it said that the stack up was 4.7mm, that's really thick for a board. I was expecting about 1.6mm or so.

I still don't know how to import a board outline with mounting holes and stuff. Can I do that in FreeCAD and import it? How are keep outs done?

 

[WobblyHand]

Schematic is entered! Having a little trouble with finding the header type connectors and footprints. Used some Molex ones, but they don't look right for what I want. The 14 pin connector is giving a warning that pin 15 isn't connected! I'm looking for something out of a Samtec catalog - dumb and simple. I am guessing I want a board thickness of 1.6mm, about 1/16th inch. Copper finish: Immersion tin ok? Just looking for something cheap.

How the heck do I enter the board physical constraints, like mounting holes and stuff, like for my display? Dang, going to have to read the docs, because it sure isn't obvious from the software itself. Been poking every button and looking through the menus... I don't even know how to get the tool to route. Or how to specify that I have power planes, and where they are... Tough learning curve.

Ran the electrical rules checker - it is complaining about input power pins not being driven, but they are connected to +3.3V and GND. I'll have to search the docs for that quirk. Fortunately, after marking all the NC pins, those are the only errors, which isn't too bad!

 

[WobblyHand]

I get this error when implementing the instructions for KiCAD.


Except the schematic is not complete... Beats me how to get KiCAD to behave. @devils4ever do you know how to fix this?

Here's a screenshot of my current schematic.

All I am trying to do is to power U2 from U1 (the Teensy 4.1). Teensy has a 3.3V output that I have used exactly the way the schematic is shown. How to get KiCAD to pass the electrical rules check?

 

[devils4ever]

Go into the Symbol Library Editor on U1-46 and change the Electrical Type to Power input. You must have it set to Output which is causing the ERC failure.

Same goes for U1-47. You have it set to Output, not Power input.

 

[WobblyHand]

Go into the Symbol Library Editor on U1-46 and change the Electrical Type to Power input. You must have it set to Output which is causing the ERC failure.

Same goes for U1-47. You have it set to Output, not Power input.

Actually, there's an on board regulator on the Teensy creating +3.3V for use of peripherals. Technically that pin is an output, as it is the output of a regulator. Teensy uses much lower voltages internally and 3.3V for I/O. What to do about ground? It's an input from the USB cable and a common for everything on the PCB.

Didn't know one could edit the pins that way, that is good to know.

By any chance do you know how to build footprints in KiCad? How do you add pads and plated through holes? For that matter, how about mounting holes? I need to make a footprint for the 3.2" display that includes the mechanical mounting holes. That way the part could be moved without messing up the board.

 

[WobblyHand]

No need to be sad, just me trying to learn new things and getting tripped up on beginners stuff. Most of the times I eventually get it. My learning style requires understanding the concepts, once I get that usually I can apply them. Understanding the concepts is what takes time for me.

 

[devils4ever]

Actually, there's an on board regulator on the Teensy creating +3.3V for use of peripherals. Technically that pin is an output, as it is the output of a regulator. Teensy uses much lower voltages internally and 3.3V for I/O. What to do about ground? It's an input from the USB cable and a common for everything on the PCB.

Didn't know one could edit the pins that way, that is good to know.

By any chance do you know how to build footprints in KiCad? How do you add pads and plated through holes? For that matter, how about mounting holes? I need to make a footprint for the 3.2" display that includes the mechanical mounting holes. That way the part could be moved without messing up the board.

I would recommend watching some YT videos on KiCad. There are a bunch that go through the entire process. Plus, there's the Kicad forum where you can look for answers or ask questions.

 

[WobblyHand]

I would recommend watching some YT videos on KiCad. There are a bunch that go through the entire process. Plus, there's the Kicad forum where you can look for answers or ask questions.

Can you recommend any? I found a series, but honestly, learning how to do stuff on an older version leaves me wanting, since the controls are different.

It's the baggage of the old version. As a new user, it isn't super useful to know how it was done two major releases ago. Just want to know how to do it today. If it worked that way back when, that's a bonus, but not relevant to me as a new user. I remember in the Mentor Graphics PCB design days (Unix 1980's) there were 8 ways to do the same thing. I really didn't care to learn all 8 ways, just one, maybe two ways that always worked. The rest was just junk cluttering my already full head.