r/AskElectronics

GIGABYTE B550M DS3H AC R2

I was replacing a cpu cooler and in the process of moving the backplate I managed to dislodge this component. The damage looks like it's behind the end of the pcie slot. I have no microsoldering ability so fixing this is out of the question and the board is out of warranty. I figured I should ask before I decide to yolo an entire system. Would it be safe to use a gpu or is the pcie slot effectively gimped?

started doing some smd soldering looking for tips and overall opinion my my first work (unsoldeing and soldering back) some caps and resisitors (soldering station used if asked is geeboon tc22) im learing so looking for ways to improve

Could someone confirm if this is oxidation and if so how I could prevent it in the future? I was also wondering if I can find a replacement for the part (bottom one) you twist open before so the tip gets loose. Appreciate it.

Hi guys! Im an electronic student and I want to know what went wrong on my pcb etching when I ironed it

Im creating a regulated power supply for my project

What happened is I scrubbed the copper with steel wool then I cleaned it with acetone. And then I placed the paper and maximize the heat on the iron and pressed it with the paper. After 10 min, i put it in lukewarm water, and waited 20 min before rising the pcb . But the thing is that everytime i put it in water, pockets start to appear and it would fail.

I have this for 3 times and the result is always the same.

The reason I print it on a magazine paper is because there is no available heat toner transfer papers locally in my area. Also when I buy online. Its always folded or curled and so printer shops in my area wont accept it.

Any advice how I do it. Should I redesign it?

Hey r/AskElectronics,

I recently got my hands on a Tektronix 7704A oscilloscope system. It came with the logic analyzer plugins of DF1, 7D01, & 7D10. I don't know anything about logic analyzing - never had to do it yet. I was wondering if it would be smart to purchase the probes for the plugins (2* P6451s - could get both for $150 max) to have a logic analyzer on my bench for when the time comes, or if I should instead save the money and invest in newer logic analyzing equipment when I need it if this system is too outdated. I know that active probes come with a pretty big price tag, so I figured it was worth an ask. Let me know any thoughts, and thank you for your time & knowledge:).

I'm trying to design a circuit to select a power input for my CM4002008. It should use VBAT only if the USB is unpowered.

I've set the circuit up to use a p-type MOSFET to let the USB source whenever it's powered. The voltage drop created by D1 should allow the USB to take priority when both are powered, while also preventing backflow.

Based on the FET symbol I think I oriented the FET correctly, but what has me scratching my head is that the Drain of the FET is connected to the USB source, while the source of the FET is connected to the drain, which seems wrong. Am I right in thinking the arrows on the FET symbol indicate the direction of current? It seems like the FET symbol contradicts itself.

First symptom: converter not starting and eating about 110 mA of input current. Further research showed that the left LT8930 chip, the one closer to the input terminals, does not start. At the VIN input (pin 7) there is a voltage, the same as at the module input. At the intvcc output (pin 8) there is no 5 V voltage. Then I found that the circuit from pin 8 is shorted to GND, and the current of 110 mA is the internal limitation of the 5 V regulator in the LT8930 chip. I found that one more small chip is powered from this output (most likely it is an LM358) and there are ceramic capacitors near both chips, these elements were desoldered and checked, they are OK, and the short circuit remained on the board. What other parts of the circuit are powered from this output, what else should I check?

ok, I could use some help. I’ve watched 1000 YouTube videos on this and I can’t figure out what I’m doing wrong. I’m trying to learn this so I can help teach my son because he’s 8 and builds crazy contraptions out of cardboard and I want to support his desire to “level up”

I have 4 LED yellow lights. I wired them in parallel to a push button momentary on switch or a rocker switch and 6 AA batteries. (pic is a recreation.)

now each battery is 1.5v and the voltage range for the lights is 9v-12v. so this puts it right at 9v

why do the battery packs get hot / smoke / pop eventually? this is the first one to pop and leak black shit, but the others have gotten hot before we pulled the battery’s out.

specs for the lights :

color : yellow

voltage range : 9v-12v

maximum current : 20mA

anode : yellow wire

cathode : black wire.

Anyone know why speed control wouldn’t work but my motor turns on and runs???

Hi everyone,

I'm working on a device for calibrating an electric motor driving a 1.5-meter auger (single or dual-axis rotor mechanics). The sensors are mounted on the mechanics, while the motor itself could be located somewhat away from them (on top, bottom, or side of the assembly).

The environment isn't some heavy industrial setup with tons of high-power cables. The wires just run from the main control box to the mechanics. Still, I want my hardware design to be as robust as possible to avoid any unexpected EMI issues from the motor. I'd love a sanity check before I build it.

(attached the schematic image to this post).

The Setup:

- MCU: ESP32-C3 Super Mini.

- Sensors: 2x GY-BMI160 modules (addresses 0x68 and 0x69).

- Power: Will be powered by an 18650 battery or through the usb, completely isolated from the motor's power supply.

My approach to extending I2C (~1.5 meters):

- Capacitance buffering: The ESP32 is connected to two PCA9515DP I2C repeaters to physically isolate the bus capacitance.

- Cabling: I'm using ~1.5m of FTP (shielded twisted pair) cable for each sensor.

- Pair mapping: To avoid crosstalk, the pairs are strictly mapped:

Pair 1: SDA + GND

Pair 2: SCL + GND

Pair 3: 3V3 + GND

Pair 4: 3V3 + GND

Shielding: The FTP shield is grounded only at the MCU end to prevent ground loops.

Pull-ups: 3.3kOhm pull-up resistors on the ESP32 side, and another set of 3.3kOhm pull-ups after the repeaters (currently placed near the repeaters, but I'm not sure if I should moving them to the far end near the sensors or place two more pull-ups near accelerometers).

Tachometer (KY-003 Hall Sensor):

There is also a KY-003 sensor reading the RPM. To prevent false triggers from any occasional electrical noise on the 1.5m wire, I'm adding a hardware RC filter: a 10nF capacitor between the GPIO and GND, placed right near the ESP32 pin.

My Questions:

- Is this setup robust enough for this kind of application?

- Are the 3.3kOhm pull-ups sufficient for this cable length, or should I lower them to ~2.2kΩ(by adding 3.3kOhm pull-ups at the end of the cable near both accelerometers)?

- Does my approach with the 10nF capacitor on the Hall sensor line look correct?

Any feedback or suggestions for improvement would be greatly appreciated!

I'm not an electronics engineer but we did control theory so I tried making this analog PID servo mechanism made using op amps. The issue is Im only able to get 180 degress of rotation about the centre from the sensor potentiometer. The rotation near the ends seems to be non existant even tho Im turning the setpoint potentiometer near its end (shown in the video). All potentiometers are 10k, op amps are TL072cp, power amplifier at the end is made of tip120 (npn) and tip127 (pnp). The images of schematic are in the comments below.

Hello everyone,

I'm really struggling to understand how polarized capacitors work in AC circuits.

Here is an example taken from Practical Electronics for Inventors.

My understanding of the circuit:

- During the negative half-cycle (positive on the bottom wire), C1 is charged respecting its polarity.

- During the positive half-cycle (positive on the top wire), C1 acts like a battery in series with the generator, thereby doubling (more or less) the voltage.

- C2 is only there to smooth out the charge.

But what happens if the circuit starts with a positive half-cycle? The polarized capacitor will charge "backwards," right? Do we assume this isn't an issue because the load has a high resistance and will therefore draw little current (so low risk for C1)? But then what if the AC frequency is low and C1 has enough time to charge fully?

Thanks a lot!

My motorcycle has a switched 12V feed to a satnav cradle. When I crank the engine the feed is temporarily cut, and my cheap Android Auto satnav reboots instantly, forcing it to reconnect to my phone - which causes a delay.

The satnav unit probably needs no more than a couple of amps for up to 5 seconds.
Edit: Satnav apparently needs up to 1A at 12V, and let's say for up to 2 seconds.

Dome light delay timers are available - e.g. https://www.ebay.co.uk/itm/280645125423 - but these are bulky and designed for switched earth circuits. I have reasonable soldering skills but don't understand electronics, so if someone could please point me towards a wiring diagram that provides clarity about which capacitor(s), diode(s) and resistor(s) would achieve what I want I'd be really interested to have a go making my own.

I'd then appreciate some advice about how to seal these components in some sort of waterproof material (resin? silicone?) to protect them please. If this could all be achieved within a black device no bigger than my little finger that would be ideal.

Thanks in advance!

(Apologies if this has been asked and answered a million times - I've Googled a lot and haven't found anything.)

Hey everyone, looking for suggestions on what could be wrong with this current circuit and ways to diagnose what is wrong

i get nothing when plugged in with the usb c from the breakout

Running an RPi Pico with GP2040-CE to a usb c 24 pin breakout.

I’ve verified the pico is working as intended when the micro usb is plugged directly into the pc. confirmed the cable I cut up worked directly as well before hand.

Based on the pin out diagram I’ve added two 5.1k ohm resistors between CC1 and GND and CC2 and GND.

- Red to B4 - VBUS

- Black to B12 - GND

- Green to B6 - D+

- White to B7 - D-

First real electronics project so not sure how to test what the issue is.

I’ve already tried multiple different usb c cables and both orientation.

I've also tried swapping D+ and D-

I will have access to a multimeter shortly to test connections