u/RohitRojo

I just soldered some usb c connectors and ESP32s onto my PCB and almost every pin got shorted. I used a toaster oven for reflow soldering with some lead free solder paste and I even used a stencil albeit the solder paste ended up pretty messy on the board.

Could I use a soldering iron and some solder on the bottom of the ESP32 to solder it? FYI the esp32 I ordered does not have any exposed pins. Would it properly solder if I just placed it on the pcb with solid solder on the pads of the esp32 and placed it in the oven?

Also, do you guys have any tips on soldering the tiny pins of a usb C connector?

I’ve done three orders with OshPark so far. The first one, using the “Prototype” service (2 layer, purple, 1oz/sqft), was good apart from my own design errors.

The second order (different board), using the 2oz service, was good for the most part. One of the IC pads meant for high current had extra solder mask on it, meaning it wouldn’t be able to output a high enough current. Sure, no big deal, I can scratch it off or maybe I’ll request a remake.

The third order (3 different layouts), using the after dark service (very ugly on a board filled with copper pours btw), had drill issues with it. Drills between 10-12mils were not drilled (hence vias are not connected). I didn’t notice this until after I soldered the boards, so now I’ll have to reorder some parts.

Are these fab issues common with OshPark, or did I just end up very unlucky?

I just imported a resistor 2.2kOhm with 22 datasheets. This begs the question, how many datasheets are enough? I used to think that 1 datasheet is good enough, but now I'm realizing that I can get more of the same information with multiple datasheets. How many datasheets do you guys usually import?

I'm designing a battery charger for my 12.6V (3s Li-ion) battery pack. I've decided to use my laptop charger that provides 20V 6.5A. The next best option is to use standard 12V 1.5A USB Chargers plus a boost converter to charge to 12.6V.

Anyways, most sink ICs say things like 20V 3A or 20V 5A. My laptop charger (Dell 130W USB C) provides either 5V 1A or 20V 6.5A (an older version of the one I linked). Do I need a USB C PD IC that specifically allows 20V 6.5A? Or will a USB C PD sink IC that allow 20V 3A or 20V 5A work fine? I.e. will the laptop charger allow 20V 5A or 20V 3A? Or will it disconnect or supply 5V since the since IC cannot handle 6.5A?

I'm designing a battery charger for my 12.6V (3s Li-ion) battery pack. I've decided to use my laptop charger that provides 20V 6.5A. The next best option is to use standard 12V 1.5A USB Chargers plus a boost converter to charge to 12.6V.

Anyways, most sink ICs say things like 20V 3A or 20V 5A. My laptop charger (Dell 130W USB C) provides either 5V 1A or 20V 6.5A (an older version of the one I linked). Do I need a USB C PD IC that specifically allows 20V 6.5A? Or will a USB C PD sink IC that allow 20V 3A or 20V 5A work fine? I.e. will the laptop charger allow 20V 5A or 20V 3A? Or will it disconnect or supply 5V since the since IC cannot handle 6.5A?

I'm creating Bluetooth modules for the Atari 2600 Console and its controller using an ESP32-C3. 1 module per controller, and 1 module per input port on the Atari Console. This PCB will plug into the console using the 9-pin D-Sub connector.

I will program the ESP32 through a USB-C connector using the USB data lines. This ESP32 will receive data from the paired controller over Bluetooth and feed it to the console through the D-Sub connector.

This review request is mainly a sanity check. It's not the prettiest board, but it should get the job done.

One concern I had - the Atari was not meant to power two ESP32s through each controller port. Will the ESP32 draw too much current for this simple application? Or should they be externally powered through the USB C port? I guess it wouldn't be too difficult to find out during testing with a multimeter.

Schematic

https://preview.redd.it/i1y0hkaecgeh1.png?width=2814&format=png&auto=webp&s=cdfb9b269ddb2660bf8ea79ba5895dcf32b68908

Top layer (red)

https://preview.redd.it/1ky8i7cgcgeh1.png?width=1728&format=png&auto=webp&s=7f150fc46c6882e905d9a9342e63e2d609d5d94b

Bottom layer (blue)

https://preview.redd.it/c1plnxeicgeh1.png?width=1798&format=png&auto=webp&s=dcddddc1b7ade15f0819ecf496d71411a768ad2c

3D View

https://preview.redd.it/4w3ofukkcgeh1.png?width=1996&format=png&auto=webp&s=0fd4ee3577c789b0777a7ea1ee810ce818016902

Thanks!

I have three LEDs powered by 3.3V - red, amber, and blue. One is connected to GND, and the other two are connected to separate pushbuttons to ground (with 3.3V pullups). Can I use a single 100 Ohm resistor between 3.3V and the LEDs? Would each LED have the same forward voltage? Or is it possible for the forward voltage of one LED to exceed its maximum? I.e. green and amber can handle 2.6V, but that would be too much for the red LED (2.4V max).

LEDs Circuit

LEDs circuit

Pushbutton circuit (ditto for EN)

Pushbutton circuit - ditto for EN net

Red LED forward voltage (minimum, typical, maximum voltages)

https://preview.redd.it/qpc6boefpaeh1.png?width=1812&format=png&auto=webp&s=00561a121b34b1b883d8573a6b94bfb11ed7ee49

Amber LED forward voltage (minimum, typical, maximum voltages)

https://preview.redd.it/mi7tvxpqpaeh1.png?width=1780&format=png&auto=webp&s=bc3243d2ecad73f80f63f304e672f489440d8e8d

I think I'm missing an in-depth understanding about LEDs -- what causes differing voltage drops under the same current? How can an LED have a minimum and maximum forward voltage?

I'm using ESP32's schematics for my PCB design. They have TVS diodes, shown below. What are their purpose? Are they required?

https://preview.redd.it/8i0h7ae0caeh1.png?width=1638&format=png&auto=webp&s=9ebd6a8ae97b5a46884c13cec33076617003537b

They also have (bypass?) capacitors for the reset/boot buttons. What are their purpose? Are they required?

https://preview.redd.it/u94eq987caeh1.png?width=1566&format=png&auto=webp&s=633880ed04940dc82729d04ba5377929a073a3b1

I am designing a battery pack for an RC Car. It uses 3 18650 Lithium ion cells to produce a max voltage of 12.6V. I'm using a BQ7791508 BMS. The RC Car will probably consume 5-12A of current, so I calculated for a 14A Overcurrent protection. I'm using battery terminals for the PCB since I don't have a spot welding setup at home. I'm separating all the systems of the RC Car into separate PCBs so that it's easier to debug. Therefore, the charger circuit will be a separate PCB that I'll design soon.

My main concerns for this PCB are related to it's performance. I used polygon pours to maximize current, but I want some verification/assurance that my polygon pours and vias are big enough to carry 12A. With a 1oz/sqft copper weight, I need ~208mil trace widths for 12A. I created polygon pours that are at least that size in length/width. If someone can verify that this will be enough, that would be very helpful. I'll probably order 2 oz/sqft boards just to be safe.

Another concern was the placement of my thermistor. I'm using an SMT thermistor placed between two of the batteries. Will that be sufficient for overtemperature detection?

Any other recommendations related to maximizing current are appreciated.

TLDR Questions:

1. Are my polygon pours and vias sufficient to carry 12A? (1oz/sqft copper weight, maybe 2oz/sqft)
2. Is my thermistor placed properly (RT1, between the top and middle battery)
3. Any other recommendations for high current PCBs

Color guide:

• Red is BAT+
• Green is BT1
• Orange is BT2
• Blue is GND (battery negative)
• Purple is between R3 and Q1
• Pink is between Q1 and Q2
• Gray is PACK- (negative output)

Thanks!

Top Layer with Color

Bottom Layer wth Color

Top Layer, no color

Bottom Layer, no color

3D View

Schematic

I'm designing my own RC Car as a learning project over the summer. I hope to learn more about PCB design, electronics, and power through the process. I've designed some PCBs before and did some PCB projects for classes and my design team. This was a relatively simple board for me to design since there are very few components.

After my previous PCB failed in ways that I'm unable to comprehend, I decided to split the system into multiple parts and connect them with wires, hopefully making the debugging process simpler. Plus, if a single part/board fails, it'll be easier to replace that part rather than the whole system. At the end, I (might) design a singular PCB for the whole system.

This Motor Driver Dev board uses the MP6551 motor driver to drive two spare motors I have. I believe my motors are the PAN14 motors. The MP6551 outputs 5A, which should work well since the motors are rated for 4.8A and I expect a small amount of power loss. I will use the Molex Mini-fit connectors and the respective headers to power the board and transfer power from the board to the motors. I used the recommended PCB layout in the datasheet of the motor driver to guide the layout of my board.

The motor driver will be controlled using an Arduino Nano (RP2040 Connect) or an ESP32 C3 (official Dev Module) through header pins and DuPont wires. The header pins also have current measurement pins as outputs to be read by the MCU.

The board and motors will be powered by a 2s Li-ion battery (7.2V nominal). I used 8.4V for current/resistance calculations for the LEDs.

The board also has two mounting holes for M6 screws on one side, and testpoints for each motor output. They're not labelled on the board.

The board is about 2 x 1 inches, so it's relatively small. I'm not opposed to making it larger if necessary.

Since I have a bit of experience but lots to learn, I am open to all levels of feedback. I do not plan to pursue a career in PCB design, but I want to master PCB design so that I can guide my peers better.

https://preview.redd.it/35hhuug43k9h1.png?width=3836&format=png&auto=webp&s=554977e98ac360aa843cf3e119b5326564380ae6

https://preview.redd.it/r3ry0vg43k9h1.png?width=3840&format=png&auto=webp&s=9f214c59787207cbe70c50064071cd40041aeff5

https://preview.redd.it/bdkqrvg43k9h1.png?width=3836&format=png&auto=webp&s=a59272abb69646718d69355a8ea2009e1987e590

https://preview.redd.it/rviilug43k9h1.png?width=1892&format=png&auto=webp&s=036590d3fbac3e60a03c47d4eb4af2932ddfc436

Thanks for taking a look!

Note: The reference designators don't all start at one since there's another schematic+PCB in this project

I'm using a VNH5200 motor driver for my RC Car. The datasheet provides a typical application circuit shown below. Underneath, it includes a note about a large blocking capacitor.

The circuit shows three symbols I don't understand. The one circled in red seems like it would be the large blocking capacitor, but why are there multiple connections to it? The capacitor circled in blue is a capacitor too, but that might just be a bypass capacitor. Can someone also confirm that the capacitor circled in blue should be connected to ground? Lastly, what is the component circled in green?

Edit: muC circled in red is the MCU

Edit 2: I'm confused by the purpose of the pull up resistors for the DIAG/EN pins -- are they not supposed to be controlled by the MCU? Are they connected to the MCU only for detecting a fault?

Also, 500uF is very large. Would an electrolytic capacitor suffice?

https://preview.redd.it/jpkhnj03wx8h1.png?width=1656&format=png&auto=webp&s=5cd7cec1c155326647bdfa22cba6e3b196e0ac98

I was reported for not picking up a delivery. I couldn’t figure out which delivery I was reported for, but I have a suspicion that I was reported for a courier service delivery (they took too long to figure out payment, they wouldn’t give me the package until they were paid, and I had another order in the car; i ended up cancelling after waiting 10+ minutes). Do I need to be worried about this singular report? Will it affect my future orders/payments?

I'm designing an RC Car with an Arduino Nano, DRV8421 motor controller, and some spare parts from an RC helicopter (motors and 8.4V battery pack). When the Arduino drives the motor controller, the motor just produces a whining noise and doesn't spin. I removed the motors to measure the voltage and current. Without the motor attached, I'm getting 8.3V and 2A from the output of the motor driver. When I connect the motor, the current drops to 2mA. Why does this happen? I've tested these motors with an L293D, and they were able to run fine. I designed my PCB for the DRV8421 since it conducts higher currents.

Here's the Altium design. Note that my printed+assembled PCB looks slightly different since I updated the design -- The motor OUT connections don't have vias on and the traces are 15mils instead of 20mils on fabricated.

I ordered some JST 02HR-6S-P-N connectors from DigiKey. I thought it would be convenient that I can order the crimp connector and receptacle at once. However, I can't figure out how to crimp it since the crimp connector is already in the receptacle. Am I supposed to be able to pluck the crimp connector out with tweezers, crimp the wire, and then put it back in?