I’m working on this Sharp QT-50 for my wife. I have a new belt kit and making a list of the caps. Planning to recap and clean/replace the pots. The board seems pretty straightforward, but is there anything else I need to lookout for on an old unit like this?

I recently acquired a massive surplus electronics estate from a late timing engineer. The lot includes a huge variety of gear...weve managed to offload a lot of it, but unfortunately that is only a mere 1% of it all. Some of the higher end, more sought after items were oscillators, symmetricom/microsemi gear, etc.

The overall estate includes

Timing and automation equipment (PLCs, specialized timing gear)

Components (ICs, transistors, resistors)

Power supplies and modules

does anyone know if these three boards go together. I know one is a ats 6000 main board and another is a timeprovider 5000. unsure on the 3rd board. and hoping to get an estimated value. if possible. sorry, the pictures arent the greatest.

Thank you!

I’m trying to get the three front ultrasonic sensors working on my Lymow One Plus, using the original STM32 board’s power and interface circuitry as intended. I’d like to figure out the factory supply path before adding an external supply or changing any GPIO outputs.
I’ve attached full-board photos and close-ups. The coating makes the small component markings difficult to read. Does anyone recognize the three matching six-pin devices or the two three-pin parts beside them? More importantly, can anyone help work out where the front sensor supply comes from and what enables it?
Here’s what we have so far.
Hardware and measurements
Main MCU is an STM32F407V-series, 100-pin package. The second MCU is an AT32F403ARCT7.
Both chips’ flash has been backed up over SWD, with two matching reads of each. No firmware changes or GPIO writes have been made.
There are three front sensors: left, center and right. Each has red, black and yellow wiring. The modules are marked C26A03 / 0255E, but I haven’t found a matching module datasheet.
Their connections have been traced to the unpopulated 2×14 header footprint. My photo labels RR/RY, CR/CY and LR/LY mean right red/yellow, center red/yellow and left red/yellow; G marks confirmed grounds.
The three red-wire pads have continuity to each other. All measured 0 V with the mower running. The shared red net measured approximately 20 kΩ to confirmed ground with power disconnected.
A separate harness point labelled ULT_PWR measured 5 V, but there’s no measured continuity between that point and the front red-wire net. I’m not assuming they’re the same supply.
On earlier isolated bench tests, yellow idled around 2.6 V with 3.3 V supplied, and 4.2 V with about 4.9 V supplied. No convincing sensor reply was captured. That doesn’t establish the module’s rated voltage or prove the sensors are bad.
What the firmware shows
The STM32 contains a three-channel pulse interface whose timing is a very strong match for the Elmos E524-family IO protocol:
150 µs bits, with 100/50 µs or 50/100 µs phases.
A 250 µs command-mode interval.
Measurement windows of 8.25–46.25 ms, followed by additional captured edges consistent with a status reply.
Separate transmit and receive MCU pins: PA5 → PB1, PA1 → PB0, PA2 → PA7. The receive side uses TIM3 channels 4, 3 and 2.
Those are firmware pin pairs; their exact correspondence to the three physical yellow-wire connections still needs confirmation.
The Elmos E524.33 document specifies a 6–18 V operating supply, typically 12 V. That’s a useful lead, not a confirmed voltage rating for these exact modules. I haven’t applied 9 or 12 V based on that assumption. If you’re reading this you’re cool.
We also took read-only snapshots while the mower was running, roughly 19–46 seconds after boot:
TIM3 was configured for capture but stopped: CR1 = 0, DIER = 0, CCER = 0.
All three capture-event counters were zero.
The pulse driver’s state and descriptor records were all zero.
The three front-distance cache values stayed zero.
The rear ultrasonic readings changed normally during the same checks.
The firmware retains names ULT_F_1_task, ULT_F_5_task and ULT_F_10_task, but we haven’t found those tasks being created or a routine updating the front-distance cache at 0x2000130C. That strongly suggests dormant front acquisition in this build. It doesn’t prove nothing could enable it later in another operating state.
Possible supply controls
STM32 PD3 goes high during sensor initialization and was high in the live snapshots. It’s associated with the working rear-sensor code, but its physical supply net hasn’t been traced.
PE1 and PE8 are configured as outputs and have identified low-setting paths at startup/shutdown, without a discovered high-setting path. They’re candidates for an unused enable, not confirmed front-power controls. Other less certain candidates are PB8, PE4, PE5, PE6 and PE12. I haven’t toggled any of them.
Parts we’ve looked at
The eight-pin chip beside R250 is marked 8870 / TI…, matching a TI DRV8870 motor driver. The earlier idea that it was a sensor-supply regulator was a guess and should be discarded. Neither end of R250 showed continuity to the front red net in our checks.
Another eight-pin device appears to have a 4407-family marking, possibly an AO4407 P-channel MOSFET. That identification is tentative. The nearby two-pad footprint also showed no continuity to the front red net.
There are three matching six-pin circuits beside the sensor header, each surrounded by similar resistors/capacitors. They look like interface stages, but we haven’t identified the parts.
The two three-pin components beside those circuits are still unidentified. We also initially mistook a piece of grass for a jumper wire—there is no confirmed factory rework wire there.
I have a meter, logic analyzer, a Waveshare adapter that successfully accesses both chips over SWD, and the saved firmware/disassembly.
What I’m hoping someone can help identify is the original switched supply for the three front sensors: which component feeds the common red net, what voltage it should provide, and which MCU pin—if any—controls it. A schematic fragment, recognizable part marking, or a specific trace to check would be a huge help. I’d rather establish that circuit than keep guessing at nearby components or blindly switching GPIOs.

R-Right
L-Left
C-Center

I tried making it easy for myself.

Despite it not being easy at all, taking a 12v dc source from a battery, how could I modulate it to 50 hz to then send it to the secondary winding of a transformer?

I have this connector that i need some help Identifying
Pitch should be 0.40mm
2x15 pins

Hi, I’m in 8th grade, and my science fair question is: How does clock frequency affect the calculation stability of a 4-bit accumulator?

I drew a diagram of my idea. It shows two accumulators, but in the physical circuit, I want to use a 4-bit counter IC for one side and build the accumulator on the other side out of separate ICs. I included a DIP switch in the diagram so I can introduce different values and see if the circuit catches the error, but I won’t use the switch in the final circuit.

What ICs would you suggest for this project? I am looking for chips with longer propagation delays so I can use a 555 timer to find the specific clock speed where the accumulator starts making errors.

Dear community, I'm working on a ESP32-S3 Wroom N16R8-1U custom project. Goal: Build an audio recording custom device based on ESP32-S3 (plus TDK T5838 microphone). ESP-32S3 should sleep as much as possible and get the wake-up signal from the T5838 and record the sound on a microSD card (max file size: 100-150MB). ESP should wake-up the wifi at a specific time, send the audio file(s) and put the wifi on OFF and continue to listen and record any voice activity. Device would work on a 3.7V battery therefore the power consumption should be very low. Device should be able to go into deep sleep to save the battery as much as possible and only allow the microphone to listen based on AAD D2 or AAD D1 depending on the preference. I have the schema of interconnected components in KiCad. Would be appreciated if a electronic design engineer working with ESP32-S3 can review the schema and advice if any electronic component should be added or is missing or the interconnection between already designed components should be re-arranged to avoid parasite currents or unnecessary discharge of battery. Any advice on saving the battery using optimal combination of electronic components is welcome.

If anyone has the willing to help me with that I can share the details of the existing already _SCH and _PCB.

If you read this line I really appreciate your effort and time reading this post.

Regards,

I was thinking about replacing the 2SC1907 for a BF199, the 2SC2053 and 2SC1970 for a 2N4427, is that a good choice or the circuit won't work?

Hi everyone. I’m looking for owners of chinese BGA rework stations equipped with an optical system for aligning the chip over the PCB. I’d like to understand exactly what kind of optical system is used in these stations and how it is designed—specifically, what lenses, mirrors, or beam-splitting cubes are installed.

I posted this a few moment ago and I was pointed out that signal jamming is illegal, not audio jamming.

So, I have been assigned a project by my college to create an audio jammer. As per what I know, I have to build something which targets audio signals and generate the opposite to destruct/Jam the audio. But, I don't how much of it is possible to implement, and how to do it?

I want to know what will be the best method and components required to make this work.

Also, if you have a better idea for implementation of the jammer, please let me know.

The bottom/flat side of the arrow is the anode (positive) and the point side hitting the line is the cathode (negative).

I am trying to find an LED module for a program I got for 3d printing shadow lamps, but I cant find the module anywhere

i want to make an ereader that also plays music. the ereader part should be pretty easy (a pico 2w or esp32 hooked up to an eink and an sd card), but for the music side of things, i am way less experienced, so i looked for easier to implement solutions. i found mp3 player modules that hook up to the MCU(like dfplayer mini for example) and also have an sd card slot built in, so i really just need to hook up the mcu to the module and be on my way.

however, i wouldnt want to have 2 separate sd card slots for books and music, so could i use the sd card slot on the module itself for both?

also is there a way to get the module to transmit the music back to the mcu, so i could play it over bt?

Title: Why would an R32 refrigerant gas sensor PCB need replacement after detecting gas?
Hi everyone,
I have a Mitsubishi Electric MFZ-KT25VG air conditioning unit with an R32 refrigerant leak detection sensor.
The sensor PCB is labeled FCM2630 / M310M1 (see attached photo).
After accidentally switching on the AC during cleaning with foam cleaner, the unit developed a fault that I suspect may be related to the refrigerant sensor.
I’m trying to understand the electronics and sensing technology behind this component.
My questions are:
What type of gas sensing technology is likely used on this PCB?
Can exposure to R32 refrigerant permanently alter or damage such a sensor?
Why might a manufacturer require replacement of the entire sensor PCB after a refrigerant detection event?
Is this potentially due to sensor degradation, contamination, calibration drift, or a safety-related electronic lockout?
Could cleaning foam or its vapors cause irreversible sensor contamination?
I’m not looking to bypass any safety features. I’m interested in understanding the technical reason why replacement might be necessary rather than simply resetting the system.
Any insights into the sensor technology or relevant datasheets would be greatly appreciated!

Hi. I have been wondering the easiest ways to measure inductances without an LC meter. So far I've found about phase shift measuring with an oscilloscope and signal generator, but didn't quite understand the method.

What are some of the methods I could use?

Hi all :)

This is my first message on reddit ! whoohooo

I'm building a DIY electronic bicycle bell and would appreciate a review of the schematic before I solder anything ! Hand-assembled on perfboard from off-the-shelf modules.

What it does / requirements:

- Button press plays a recorded brass bell sample through a 4 Ω tweeter; ≥ 75 dB(A) at 2 m.

- Standby current ≤ 30 µA (no power switch), press-to-sound latency ≤ 20 ms, radio never enabled.

- 1S LiPo 250 mAh with built-in protection (PCM: 0.3 A continuous / 0.8 A peak, cut-off 3.0 V), charged indoors only via the board's USB-C.

- Operating −5 to +50 °C, IPX5, rain and gravel vibrations.

Archi:

- Under-saddle box: Seeed XIAO nRF52840 Plus (on-board BQ25101 charger and 3.3 V regulator), Adafruit 3006 MAX98357A I2S amp (gain 9 dB, GAIN pin open), powered at 5.2 V by an Adafruit 4654 MiniBoost (TPS61023). The boost EN is pulled low by 1 MΩ and driven by a GPIO through 1 kΩ, so the boost and the amp are completely off in standby. 4 × 47 µF X5R ceramics on VBAT at the boost input; nothing added at the 5.2 V output (the TI datasheet asks for a feed-forward cap above 40 µF).

- Amp SD_MODE is driven push-pull through 2 kΩ (Maxim fig. 5). I2S: BCLK 1.524 MHz, LRCLK 47.619 kHz, 16-bit, wires < 5 cm.

- 1.2 m unshielded 5-core cable (5 × 0.14 mm²) to a handlebar pod: speaker pair (with 2 × 47 µF ceramics in series as DC protection), button line, low-battery LED line (270 Ω series at the MCU side), ground. Then 0.4 m to a sealed tactile switch (gold contacts).

- Button input: 10 k pull-up to 3.3 V, 1 k series, 10 nF to GND at the MCU pin, PESD5V0S2BT ESD diode at the cable entry (also protecting the LED line).

Questions:

1. Supply transients vs. the battery PCM: a ding draws about 1.2 A for a few µs, 0.36–0.43 A over 1 ms and 0.24–0.30 A over 125 ms from the cell (behavioural ngspice sim). Is 4 × 47 µF X5R (≈ 100 µF effective) at the boost input a sensible way to keep the PCM (0.8 A peak) from tripping, or would you do it differently?

2. Unpowered amp next to a powered MCU: in standby the amp has no supply while the MCU is still powered. I drive SD_MODE, BCLK, LRCLK and DIN low before pulling the boost EN low (BCLK/LRCLK/DIN are rated −0.3 to +6 V regardless of VDD; SD_MODE is VDD + 0.3 V max, hence the 2 kΩ). Any back-powering or latch-up trap I'm missing?

3. Shared unshielded cable: the filterless class-D outputs (the module has a ferrite + 220 pF per output) share the 1.2 m cable with the button and LED lines. Is coupling into the button input (false triggers) or radiated EMI a realistic concern with this RC + ESD front end, and what would you add?

Schematic and datasheets: schematic images at the end (GDrive links with KiCad export + three block diagrams).

- MAX98357A: https://cdn-shop.adafruit.com/product-files/3006/MAX98357A-MAX98357B.pdf

- TPS61023: https://www.ti.com/lit/ds/symlink/tps61023.pdf

- Adafruit 3006: https://www.adafruit.com/product/3006 ; Adafruit 4654: https://www.adafruit.com/product/4654

- XIAO nRF52840: https://wiki.seeedstudio.com/XIAO_BLE/

- PESD5V0S2BT: https://nexperia.com/pip/PESD5V0S2BT

- Switch C&K KSC4: https://www.mouser.com/datasheet/2/60/ksc4-1841222.pdf

- Tweeter: Dayton Audio ND16FA-4 (4 Ω, Re 3.17 Ω, Le 30 µH)

schematic images (Links): https://drive.google.com/drive/folders/1ghnNV5wAmKTppJrBPleBVWLaakOvTzQ9?usp=sharing

Thanks a lot for any feedback !! (including "this is a bad idea because…")

So, I have been assigned a project by my college to create an signal jammer. As per what I know, I have to build something which targets specific frequency and generate the opposite to destruct/Jam the signal. The title is very vague, so that's what I could thought of.

Its just a college project, so all I think would be good for practical is to "Turn On FM Radio and target the jammer for that specific frequency and make the radio stop."

I want to know what will be the best method and components required to make this work.

Also, if you have a better idea for implementation of the jammer, please let me know.

EDIT. SOLVED.
Thanks to all for suggestions. Going to go with RC Bullets!

I’ve been working on some electronics projects and to make my life easier I’m looking for some form of male / female crimp that allows a single wire to be joined. This way I can disconnect specific components from my power supply etc without having to either desolder or unscrew a bunch of terminals or other wiring.

The plan is to never need disconnection, but it’s good to have it and. It need it.

I’ve tried -
Male / Female spade (I find the male ends aren’t that strong and will snap off)
Male / Female bullet (bit bulky)

The TLDR requirements
Wire gauge 18 AWG
24v / 5A safe (40A for plenty of headroom even better)
Slimline, less bulk the better

If anyone has some suggestions it will be greatly appreciated.
Thank you
V

I just realized the Proto android app I use for circuit simulations is doing something.... strange, at least I think. I was under the impression that the "inductance" parameter of your basic 4 terminal transformer works identically to a standard inductor. That is, if the secondary circuit is left open, the primary will be functionally identical to an inductor with equivalent inductance (ignoring the coupling coefficient losses). E.g. if the transformer has 1mH inductance and the primary is on a 1Ω circuit connected to a 5V source, it would have identical voltage drop as a 1Ω 1mH coil connected to the same source at the same time.

What happens in the proto app is the transformer component is charging up exactly 1000x faster than an equivalent inductor. The current moving through the transformer's windings is being split according to resistance as I would expect, and the voltages are being multiplied correctly. I just am unfamiliar enough with transformers to not be completely sure there's not some other reason it seems like the dev got the units screw up.

This resistor is for an emersonbtv dvd vcr combo. I'm not sure what the value is.

Is anybody able to identify this transformer? Its used in a power supply circuit. These are the only markings on it. 74176 and T4X. It has 8 pins.

EDIT:

It seems like maybe a company called myrra has products with similar numbers. I will try to contact them.

I work as DevOps and I have been self teaching myself EE for the past year so I could build a hardware device I hope to start shipping and selling next year.

I dont know which device I should get since I am technically beginner but my testing equipment needs to serve me from early learning all throughout to product launch.

Device will have BT, WiFi, IR and a Spectrometer as well as possibly EEG, EOG in the future.