First KiCad Project and New User Introduction

Projects
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Hello Everyone,
Name is Robert and I am a new KiCad user and fairly new to electronics design. My current designs have stemmed from a direct need of a solution, ‘I need to research what components will work to solve this issue or accomplish this goal’ as opposed to ‘I want to learn electronics’. I have worked with bread boarding, done basic projects and have a basic understanding of all the major components and their functions as well as the basics of voltage, amperage, and impedance. I also have basic understanding of programming and have programmed several micro controllers to do basic tasks.

I am also an automotive technician, specializing in restoration, retro-mods, road racing, engine building and performance and occasionally general repair with 30+ years of experience. I am not looking to become an electrical engineer, but I do need to know how to create custom solutions when the need arises. I typically don’t have tinker time and have to lean on the community for help with getting me pointed in the right direction in finding a solution. My apology if that intro was a bit lengthy.

Ok, so my first project is…a simple controller to trigger the negative side of a relay coil that triggers a relay which in turn controls a cold start valve on a diesel engine injection pump. I am using an buck converter from Adafruit based on the MPM3610 chipset to regulate voltage from system 12v to 5v to power up the OPA347 single OpAmp set-up in a voltage comparison circuit as well as power up our voltage divider circuit for the comparison. I am using a 680/220 ohm split to pull down the 5v to 1.23v. The CTS (coolant temp sensor) is high (up to 3.3v) when cold and the voltage drops lower as the temperature goes up. In this case, 60C (140F) is the 1.23v mark, as long as the voltage is above the 1.23 mark the OpAmp will output a 5v signal which drives a IRLZ44N Mosfet. This is turn drives the ground side of the drive coil for the power solenoid that powers up the relay that in turn powers the cold start solenoid of the injection pump. Once the voltage signal on the CTS reference line drops below 1.23v, the OpAmp shuts off the 5v drive output to the gate circuit of the Mosfet and is pulled to ground via a 10k resistor.

So I have already spent a few hours on the schematic editor building a schematic, it looks clean and readable to me, but perhaps it can be further cleaned up. Now I have already built this and tested it on a breadboard and have put it into an enclosure. I want to use this as a learning project before moving on the larger glow plug controller which I have already built but its hand drawn schematics and very hackishly soldered on to perf board, but that is for another day.

Today I have been delving into the PCB editor and oof, I am totally unfamiliar and am pretty lost from the get go. I will dive into some videos to try to get some clarification and direction. I can see right away I am going to have to create a custom footprint for the buck converter as right now its just setup on a standard TO-220 footprint and the pins are reversed. I can temporarily fix this by flipping the part upside down to the bottom of the PCB but this is not a correct fix. In addition the OPA347 OpAmp is going to need to be custom built into the symbol library(?) as I am just using a generic DIP-8 package footprint and get pin errors when I go from schematic to pcb editor.

Any comments on the project are welcome, and I am aware this is pretty off topic in some ways but I wanted to introduce myself but did not see specific place to do that. I figured I might get some slack on my first post, hopefully the mods don’t roast me too bad here.

Thanks and I look forward to being an active member.

inj-pump-relay_control.
inj-pump-relay_control.3300×2550 188 KB

PXL_20231208_213219761
PXL_20231208_2132197611908×2544 343 KB

PXL_20231209_030034433
PXL_20231209_0300344331908×2544 323 KB

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My comment is your best strategy is to post specific questions that you need answered about an aspect of KiCad. For example: How do I display all the pads that this net connects, rather than Please critique my project and tell me how to improve it. Such open-ended queries often cause the topic to diverge in multiple directions and it becomes difficult to stay focussed.

Do not be afraid to create as many topics as needed to answer a simple question in each topic.

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Hello and welcome @electroman

The documents listed on https://docs.kicad.org/ are a great way to learn, in particular the “Getting Started”.
There are also some possible answers to questions in the FAQ at the top of this forum.

If you are intending to use videos, check before hand for their age. Some on the internet are a bit dated and of not great help.

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For the schematic, draw it in such a way that higher voltages are on the top, and lower voltages at the bottom. Have a horizontal wire that is clearly marked as the GND reference. Also draw it that signals (mostly) go from left to right.

You are also missing some decoupling and buffer capacitors. With analog circuits it’s not as critical as with digital stuff, but it still improves reliability.

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Read it first:

I suggest to show your project at some electronic forum to discuss electronic aspects.
You use OpAmp in application where the comparator would be natural first choice.
Do the relay have integrated diode to protect your Q1 against voltage pulses generated by relay coil inductance when switched off.

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Thank You for the tips on schematic layout, I went back in last night and cleaned things up some more, updated a couple things, realized my connector was backwards once I was able to see it in 3d view, etc

In regard to the capacitors, there are 2 22uF caps built into the mpm3610 buck board for power filtering. Where you referring to using one on the IRLZ44N mosfet between the source and drain as a buffer or perhaps on the OpAmp circuit?

Still learning so forgive me if that is incorrect thinking.

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I was unaware there was a difference between an OpAmp and a comparator since I am using the OpAmp in a fixed voltage divider reference circuit to compare a variable to a fixed source?

And yes, the relay does have an integrated flyback diode built in, I ordered the relays specifically to have the feature integrated. Thanks for bringing that to light as it would have been easy enough to integrate a diode into the gate circuit of Q1.

I appreciate the input.

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I highly recommend watching Dave’s video on schematic layout and best practices. It’s long but well worth it. Good to have the basic correct from the start.

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That is just juch. I can tolerate and maybe even appreciate the yellow bodies of IC’s that Kicad settled on, but putting them around circuit sections is detrimental to readability. It just makes the schematic crowded. Re-arranging, redrawing & re-aligning such boxes during revisions over the lifetime of a circuit is also a silent but huge time waster. A bit of whitespace is both sufficient and easier on the eye for separation of parts.

Having titles of sections in a big fat font is a good thing though. That easily and quickly identifies different circuit sections.

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One hour and 25 minutes? Really? I wouldn’t spend that much time on a subject that could be covered in 5 minutes.
Apart from that, Dave’s eevblog forum is the best around at this time.

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From the screenshot of Dave’s video it seems he’s using a style of schematic drawing which uses labels for connections between sections of the schematic. I find the extreme examples of this style irritating. The worst have even a single IC as a whole section. I prefer to use wires and buses most of the time, resorting to labels for the odd connection. But you’ll have to discover your preferred style somewhere on the spectrum between wires and labels.

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This is my 10 minute version of the OPs schematic.

ksnip_20231212-120448
ksnip_20231212-120448895×438 22.2 KB

All the experts please criticize away! :smiley:

@electroman Because this is a simple schematic, it can be arranged such that it reads much like a book page: left to right, top to bottom.

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Your grid is annoying. Otherwise I’m with you.

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A little better? :grin:

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I have been on there a number of times. Too much noise = bad advice.

Much better schematic. But the design…it might work for a while but it needs a bunch of tweaks.

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Story of my life. :neutral_face:

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Thankyou :slightly_smiling_face:

Mine was an example of “artistic flair” :rofl:

Only a bunch? Mine is a case of a complete rebuild… for quite some time! :slightly_frowning_face:

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LOL, I am glad everyone is enjoying my thread. I have watched quite a few of Daves videos in the past, quite an entertaining fellow and quite informative. I am sure some well trained EE experts might disagree with some of his content, but for the new guy and the hobbyist I think he is pretty great.

Just got your PM, thanks!

Thank you for this updated design style, I will take it under consideration. I think that I should go back and look at some of the manufactures wiring diagrams for some inspiration as well. I always enjoyed the earlier 80-90’s BMW schematics and found them easy to follow, Toyota’s weren’t too bad either. But then again I am used to looking at automotive wiring diagrams which are different from electronics diagrams and so I think there will always be a disconnect between how I might see them as opposed to how a EE might see them.

Thanks again for all the comments, I am glad everyone seems to be enjoying the thread.

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This forum is not supposed to focus on circuit design, so I sent you a PM (private message) touching on some areas…

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@electroman

You can find @BobZ s private message by checking your avatar at the top of your forum page.
Click on the green circle enclosing an envelope.