Schematic Review Request: Smart Blinds Control - Page 1
Forum section: electronics / projects

author: lemm
author_rank: Contributor
timestamp: April 14, 2025, 08:27:33 am
content: Edit: I removed the +5V label as suggested in the comments and CI1 and CI2 are now in parallel. If someone finds another mistake, I'd be very happy to get it reported. ThanksHi everyone,I'm working on a controller board for smart blinds based on an ESP32-WROOM-32E and would really appreciate it if someone could take a look at my schematic before I move on to the PCB layout phase. I'm new to PCB design and generally schematics, so any feedback is welcome. I already run an ERC and it couldn't find any errors.Project Overview:Goal: Control a stepper motor for smart blinds.MCU: ESP32-WROOM-32EMotor Driver: TMC2209 (using UART control)Position Sensing: AS5600 rotary encoder (connected externally via I2C)Power: Takes VIN (7.4v battery), regulates down to 5V (for TMC2209 VS), then further regulates down to 3.3V (for ESP32, TMC2209 VCC_IO, AS5600). Includes reverse polarity protection and a fuse (planning 2A Slow-Blow).Motor: Bipolar stepper, 0.8A RMS, powered by the 5V rail.Key Features: Uses TMC2209 StallGuard for end-stop detection (via DIAG pin), AS5600 for position feedback (via I2C).I would greatly appreciate it if anyone could take a look at the complete schematic and let me know if they spot any potential issues, errors (connections, component values, etc.), omissions, or have any suggestions for improvement regarding reliability or functionality.Thanks in advance for your time and expertise!

author: xvr
author_rank: Frequent Contributor
timestamp: April 14, 2025, 12:46:26 pm
content: C11 and C12 are connected in series, but should be parallel.The +5V network mark on the right side of R01 and R02 is very suspicious - it should not be there.

author: SteveThackery
author_rank: Super Contributor
timestamp: April 14, 2025, 01:05:03 pm
content: Quote from: xvr on April 14, 2025, 12:46:26 pmThey look to be in parallel to me. Very confusing schematic.Ah, you mean CI1 and CI2! I agree.This schematic is pretty dreadful for readibility. It's got grounds going up, down, left and right. The way R12 and R13 are laid out is amusing. It really needs completely redrawing.

author: SteveThackery
author_rank: Super Contributor
timestamp: April 14, 2025, 01:10:46 pm
content: Quote from: xvr on April 14, 2025, 12:46:26 pmAlso agreed. It'll be a bit under 1V at that point.

author: PartialDischarge
author_rank: Super Contributor
timestamp: April 14, 2025, 01:19:04 pm
content: Add TVS diodes, with series resistors if possible, to any terminal that goes connected with cables outside the board. Real life is full of EMI and spikes and microcontrollers get crazy when spikes get into any pin.The best protection is to enclose evertyhing sensitive in a shield, but is more expensive...

author: lemm
author_rank: Contributor
timestamp: April 17, 2025, 07:04:18 pm
content: Quote from: xvr on April 14, 2025, 12:46:26 pmThank you very much for helping meI just want to ask if you think I can go ahead with the PCB design or if there are any other major errors?I really appreciate it

author: Analog Kid
author_rank: Super Contributor
timestamp: April 17, 2025, 07:26:10 pm
content: Quote from: SteveThackery on April 14, 2025, 01:05:03 pmWhat do you mean,CI1andCI2?I see no such components there.C11andC12are obviously in parallel, as they should be.Maybe a nonstandard way of positioning them, sure, but still looks legit to me.

author: lemm
author_rank: Contributor
timestamp: April 17, 2025, 07:29:57 pm
content: Quote from: Analog Kid on April 17, 2025, 07:26:10 pmI'm sorry about that, it's a bit confusing. CI1 and CI2 are right under the vsense pin of U4. In the image they're still in series.

author: SteveThackery
author_rank: Super Contributor
timestamp: April 17, 2025, 07:31:17 pm
content: Quote from: Analog Kid on April 17, 2025, 07:26:10 pmC11 and C12 are top left. CI1 and CI2 are top right. I congratulate the OP on the ultimate in confusing component numbering. CI1 and CI2 are definitely in series - we agree. C11 and C12 are in parallel.

author: Analog Kid
author_rank: Super Contributor
timestamp: April 17, 2025, 07:35:19 pm
content: Quote from: lemm on April 17, 2025, 07:29:57 pmNo problemo, I see them now.They should definitely be in parallel, not series.I totally agree that this is a very bad way to draw a schematic. You're obviously still learning, though, so no harm, no foul.Maybe take a look at other legit schematics to learn how they should be drawn.It's not rocket surgery: things should be organized and oriented to make it easy to follow.You'll get it.

author: hve
author_rank: Regular Contributor
timestamp: April 17, 2025, 08:55:18 pm
content: Maybe some comments:- If I remember correctly the TMC2209 can detect the endstops using back emc.Maybe you could save on the rotary encoder.- The esp32 takes quite a bit of power, it will be quite a challenge to get a decent operating time on a battery charge..I am not sure but you might also check the power dissipation of the step down converter...

author: phil from seattle
author_rank: Super Contributor
timestamp: April 17, 2025, 11:57:04 pm
content: Along with all the other comments.- Are you using electrolytics? I would move to ceramic SMDs. Up to 22 uF are cheap as dirt and will last longer than electrolytics.- The Vin label on the TPS54331 circuit is kind of hidden. I would redraw the symbol to allow input power on one side and output on the other.- Take a look at the TPS54331 datasheet. The typical application schematic on page 14 is much clearer than yours. There is no shame in cribbing it straight out the datasheet for your schematic. For what it's worth, I don't think you need quite as beefy a regulator. Bet you would be fine with a 1A buck regulator.- Repeating about grounds and positioning. Put all your grounds at the bottom (or at least pointing down), all voltage rails at the top (pointing up). At least for a given subcircuit.- Keep your symbol naming consistent. C vs CI? serves only to confuse, as half this thread demonstrates.

author: lemm
author_rank: Contributor
timestamp: April 18, 2025, 08:04:28 am
content: Thank you hve and phil from seattle for your detailed feedback. I will try to implement it.

author: pcprogrammer
author_rank: Super Contributor
timestamp: April 18, 2025, 12:31:10 pm
content: Seeing that you are a beginner, I would also advise you to post your PCB layout here when you made it. There is a part in this circuit that requires a good layout. This is the step down converter and you best check the datasheet for guidance on it.As others have pointed out, your schematic is a bad example on how to properly draw one, but at least you used wires to make the connections.(Edit, on most of the connections that is)The naming of the components also stretches to the resistors. Don't use confusing names. Best stick to R1, R2, etc. Makes the silk screen on the PCB also better readable. Long names take up a lot of PCB space.

author: SteveThackery
author_rank: Super Contributor
timestamp: April 18, 2025, 05:46:28 pm
content: Quote from: Analog Kid on April 17, 2025, 07:35:19 pmHey, a delightful mixed metaphor! I believe the "correct" phrases are:"It's not rocket science.""It's not brain surgery."Surgeons don't normally have rockets in their operating theatre.

author: pcprogrammer
author_rank: Super Contributor
timestamp: April 18, 2025, 06:34:59 pm
content: Quote from: SteveThackery on April 18, 2025, 05:46:28 pmIt is a fancy name for someone who works on the internals of a rocket.Rocket surgeon and hence rocket surgery.

author: Analog Kid
author_rank: Super Contributor
timestamp: April 18, 2025, 07:14:37 pm
content: Quote from: pcprogrammer on April 18, 2025, 06:34:59 pmUgh.Once you have to explain a joke it takes all the juice out of it.That would be a big bomb in front of the stand-up audience.

author: phil from seattle
author_rank: Super Contributor
timestamp: April 18, 2025, 09:21:21 pm
content: Quote from: Analog Kid on April 18, 2025, 07:14:37 pmI totally agree. Is the bear the catholic?

author: Analog Kid
author_rank: Super Contributor
timestamp: April 18, 2025, 09:23:47 pm
content: Quote from: phil from seattle on April 18, 2025, 09:21:21 pmI thought you were going to go with "does the Pope shit in the woods?".

author: TimFox
author_rank: Super Contributor
timestamp: April 18, 2025, 09:28:25 pm
content: Methodist Sunday-school children sing, “Gladly, the cross-eyed bear”.

author: Analog Kid
author_rank: Super Contributor
timestamp: April 19, 2025, 09:20:12 pm
content: Quote from: TimFox on April 18, 2025, 09:28:25 pmOy, this thread is devolving (how did we get onto misheard lyrics from mixed metaphors?):"There' s a bathroom on the right""'Scuse me while I kiss this guy""José, can you see?""the donzerly light"And of course, the classic:"They have slain the Earl Amurray, and Lady Mondegreen".

author: phil from seattle
author_rank: Super Contributor
timestamp: April 19, 2025, 11:09:29 pm
content: Go big or go home!Let's not forget the original stalker from the Bible. Shirley, good Mrs Murphy, shall follow me all the days of my life.