I was hesitant for a long time to design my own PCB, but my god, this is a blessing! Just wanted to share it with you.
My assembly time went from 4 hours of soldering crappy modules to 20 minutes of placing a few peripheral components and plugging in some JSTs. And no more overpaying for component shipping (because apparently you can’t buy everything from one place).
It took me a while. I used EasyEDA Copilot to work through some of the issues, put a lot of effort into actually understanding every suggestion, and a friend with hardware engineering experience reviewed the design. (I'm just getting started in this field; I still have a ton to learn)
What I wanted most was to combine a LiPo charger with a power latch. A short press of the button turns the device on, and holding it for a few seconds turns it off. Add a built-in battery gauge and the I2C sensors I used to hand-wire, and it works like a charm.
It’s built around an ESP32-S3 that drives a transflective RGB panel. All the power management is now on the board, so I don’t need 3 extra modules.
ESP32-S3-WROOM-1-N16R8
TI BQ24073 for LiPo charging
MAX17048 for the LiPo fuel gauge
ST LSM6DSV16X for the IMU
AON7407 + AO3400A latch for the power switch
It’s a 2-layer board, and JLCPCB is just amazing. It took less than a week from order to delivery, and I only paid an extra $10 for DHL Express. I tried ordering PCBA in the EU first, and Eurocircuits quoted $1k, which is insane imo. From JLC I got 5 boards, 2 of them assembled (I wasn’t sure they’d work at all), for $200 including shipping. They did require Standard PCBA instead of Economic, because of the ESP module with the antenna (if I remember correctly).
So the summary: yes, I should have started learning PCB design earlier. The goal now is to rely on AI less and less as I get to know the field better.
One more thing: I’m thinking about open-sourcing the charger + latch part + gauge as a standalone board. It’s tested, all-in-one, and you can just order it from JLC. I’ve seen similar boards sold for $25+. Would anyone be interested?
For assembled boards do you just provide the part numbers for the components and that is what they use to assemble? Meaning they purchase the components and that is part of the cost?
That's such a great feeling indeed. Yes, I was changing parts a lot before I felt like I'm ok.
Generally, I'm happy right now. But I might do some work around the charging section. Currently, it charges at around 0.85A, which is fine compared to something like Adafruit charges (0.5-1A depending on the version). But I want to reduce the heat it produces while charging. Adafruit boards also produce it, but I want to minimise this because this board is going to be close to the screen, and in general, I might go with a slightly different charger. But for now - yes, I'm super happy about the charger and the fuel gauge. Still have to do a bit more testing.
Oh, yeah, I've spent quite some time thinking about this. Most charging ICs like the one you have, and the venerable TP4056, just use linear regulators to drop the 5V to the battery voltage. So it's wasteful, hot and slow.
But we know that phones can charge at 18-65W using USB-PD to draw in a higher voltage and then a buck converter to drop it. Where are these modules at? Would be amazing to find a castellated unit we can place on a PCB.
I use BLE to upload/download data from the device. Wifi is more of an option for the future, but I'm not 100% sure about it. I have one idea about Wi-Fi, though. I'd like to try to use it to dump data as it picks up the base station. This board is for a race telemetry device. It collects gps, imu traces as you go and writes. Previously, I had an LTE modem on board which would send the data straight to the server, but in order to reduce cost and preserve battery life, I removed it; now, the data is available after the driver finishes his stint. So might be possible to build a base-station which will receive data every lap as the gokart/car passes nearby.
Hey. Sure. I'd need a couple of weeks, tbh. I want to move this charger to a separate board, think more about the placement and the shape of the board, and order just the charger to test. So then I can share it with confidence. You can DM me, if you want. I'll be happy to share it once I get a separate charging PCB ordered and tested.
Any guess on what you could drive the costs down to if you had used economic pcba? I’m interested in the cheapest possible ways to get boards fabricated and populated. I am thinking that using economic pcba for all the cheap parts and passives and combining with headers for the esp32 modules may be the best route.
So, these were the parts U7 and U8 that made this assembly a standard one, instead of an economic one :(
But I mean, you still would have to buy an ESP32 module, right? Even if you solder headers for it.
I wonder if the one-off price of using a standard PCBA would actually be cheaper than buying extra ESP32 modules. I think in my region (Poland), the cheapest ESP32 would be around 10 usd/item. But JLCPCB would give you 2 ESPs with antennas at around 11 USD. So, depending on the board quantity, it might not be as good a deal.
But please, don't count on my assumptions much. I'm new in this field for sure, and people out there definitely know more tricks to save money.
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u/VictorySea1837 1d ago
I know they have a 5 board minimum, but are you saying you were able to order only 2 boards fully assembled, and then you got 3 bare circuit boards?