A cautionary tale in two photos: beeper removal and GF problems

I have an AC that's triggered with an IR remote. Each time you do an action: it beeps. I also automated the AC with an IR transmitter and an ESP32. I wanted the AC to turn off at temp, and turn back on when it's over temp. But that would mean beeps at 3AM?? I hate that so I used pliers to rip it off. No more beep, yay!

This wasn't an issue until my girlfriend turned on the AC with the remote. She complained that there was no feedback for the button presses. (Ok, she actually said, "I don't like that it doesn't beep!" which is complaining about no feedback.)

So I, intrepid hardware modder that I am (I just search a bunch,) I decided to have an artificial beep from speakers (They still aren't installed). So I took apart the split AC again, and soldered to the leads of the buzzer I ripped off. That goes though various resistors and a optocoupler until it gets to an ESP32. That reports a beep was done.

Optocoupler was stolen from an old cheap USB power supply. (THIS is why you should horde old PSU's and other PCBs)

Except... no voltage from the beeper. Or, really, I was getting a ton of it. Or none? It's been a while, but I was on a goose chase because of the two leads off of the buzzer remains. (Also using the wrong AC ground rather than the DC ground) I hunted around, trying to find what controlled the buzzer, thinking I found it i ripped off the component... that provides 5V to the board. (You can see it re-soldered on there, second photo.)

Good news: I DID find the pad that controlled the buzzer. It's on the micro controller that's above the buzzer there. Bad news: too small to solder to when I'm standing on a desk reaching up to the split AC's mainboard that's still screwed in.

After an hour I finally realized: The buzzer must be the problem, I pull off the plastic remains... and one of the leads was disconnected from the board from when I snapped it off with pliers. I was trying to trace the leads to find the mosfet that controlled it, and learned some more things about PCBs... but I could have just soldered directly to the pads of the PCB.

So, now I have a place in Home Assistant for when I finally DO install the speaker in the room, there will be a chime when my GF turns on the AC manually, and no chime when the AC turns off/on automatically via the IR ESP32. Except it's redundant because none of the code has found a use for the beep function (It just caused more problems,) I'm going to move the IR transmitter to this ESP32 installed inside the AC itself, so I won't need confirmation... and the next project is a custom AC controller for the GF that will make this extra redundant. (I can have a chime still... but it would directly trigger from her pressing the buttons, not from the AC itself.)

Also I made this post because someone else asked a question showing off their fail and deleted their post, and I wanted them to know they aren't alone with their hate of beepers and doing dumb things to boards. (Ok but stabbing the beeper with a soldering iron is a step too far! Use pliers like a civilized man.)

Behold: My first major project that isn't just big electric components or basic relay logic.

This is a WiFi servo controller that I'm building to control a homemade automatic power transfer switch for our home's backup generator.

Two large main servos are powered by the large buck converter module, and a third auxiliary servo is run off of a 3.3V regulator. A second regulator powers the ESP-01S WiFi control module to avoid voltage fluctuations when the small servo is powered.

The ESP-01S handles the signals for controlling the servos, and is connected to my Home Assistant home automation system via Tasmota.

It's DEFINITELY not pretty, and I still have a lot to learn about soldering, but it DOES work.

...For about 3 seconds until it sent the full 12V supply voltage into one of the servos and destroyed it...

I'm guessing the 3.3v regulator I used to power the small auxiliary servo just isn't up to the job. That means this whole thing has to go back to the drawing board. :(

Purchased AD SSM2019 amplifier from DigiKey, only 1 unit. Got 26… :)

So I made those PCBs at home. Those are adapters from SOP to DIP so prototyping is easier. Took me like a day

I think you already know, but since July 1st a tax of €3 per ARTICLES is now mandatory. (they say it’s by categories but in reality, no)

For €30 of electronic components, I have +€50 of taxes. For a person who has started to be interested in electronics recently, it hurts.

So I come to try to find alternatives to aliexpress, with similar prices if possible… If the delivery lasts 6 months but there are no taxes I DONT CARE, I need the components at an affordable price.

Thanks, and I hope that the aliexpress sellers will quickly find a solution for us

Don't ask me, ts is on another whole level of abstract

Ignore the rock drawer I didn't have a better place for my cool rocks.

I have a couple of these receivers I got in a pile of old stuff and by default they're USB but I wanted to use them with my microcontrollers, so I ripped one apart with a simple pry tool then removed the pressed on RF shield to expose the goodies.

Looking at the USB to serial transceiver, I see it's a PL-2303HX and looking at the datasheet, pin 1 is serial TX and pin 5 is serial RX, so I traced them to two open solder bridges.

Closing those to solder bridges with questionable soldering using an oversized tip resulted in the two unused pins now making connection

I decided to use the existing cabling so I used a small pry tool to lift up the plastic tab holding the green and white USB data wires and pulled them out and inserting them into their new homes

After snipping off the USB connector, red to +5v, black to negative, and the two serial lines to my ESP32 pins,

I started streaming NMEA datagrams over uart ❤️

NOTE: the default speed for this receiver is 4800bps

Here's some animations I made of transistors turning on and off. In order, we have an NPN BJT, n-channel MOSFET, and finally an n-channel JFET. The red and blue dots represent electrons and holes, and white flashes are recombination events. The density of dots is proportional to the actual density of charge carriers.

In the first set of animations, the velocity of the dots is equal to the velocity obtained by summing the diffusion and drift currents and dividing by the charge density, but diffusion is not explicitly shown. In the second set of animations, the dots undergo diffusion and drift, and this makes it a more correct depiction of carrier motion. The drawback is of course that the jiggling makes it more visually confusing.

I made these with my semiconductor simulator (https://brandonli.net/semisim/). I also have higher quality versions of the animations here.

Very simple circuit - i had a bunch of these charger/booster modules laying around and decided to learn about the dangers of bare 18650 batteries. Excited to do more.

I wanted to modify my PS3 controller to USB-C, but it used a through hole connector. Not a problem!

Nice and simple two transistor flasher, with a red and blue LED.
I kind of wish I had opted for warm white LED behind the colored lens, and that would have given a more natural halogen look.

I accidentally selected the wrong resistor value for this board, but I still wanted to test whether the circuit worked. The original footprint was 0201 imperial — 0603 metric, and I needed a resistance of 17 kΩ.

Since I did not have a 17 kΩ resistor in 0201 size, I improvised with three larger 0402 resistors connected in series: 15 kΩ + 1 kΩ + 1 kΩ

I soldered them together as a small bridge directly onto the original 0201 pads.

The entire repair was done by hand with a soldering iron and tweezers, without using a microscope. I only used the microscope afterwards to take the close-up photo.

It may not be the most elegant solution, but it measured correctly and allowed me to continue testing the board. The second photo includes an M3 screw for scale.

What do you think?

Hi everyone! I'm looking to connect with other women in the electronics field to share projects and support each other. I actually started a community specifically for this at r/HardwareWomen. If you're interested in joining a dedicated space for women in tech/electronics, we'd love to have you!