Ask Electronics

7 Year old monitor started to have panel issues today, no initiating event. Did the normal trouble shooting, shut every component down, disconnected, swapped cables, updated firmware, changed resolutions, etc... issue persisted.

Took it apart to have a looksie

Getting all the plastic snaps off the back of the monitor was the single longest part of this... very annoying. I miss easy to repair devices.

The PSU has shorts!!

the other side of the pcb is a transformer

some other leaking seen as well

both sides of the PSU in full

the logic board looks fine

I'm tempted to just fix the shorted pads and test the voltages... I probably should replace the transformer

Lots of chatter on youtube about the thunderbolt ports dying on this monitor, but I don't think that is applicable to me. At least the PSU shouldn't look like this even if its not the core problem.

Any insights or suggestions from those you have rescued erstwhile monitors? This is the first monitor that has ever fully died on me. I melted a laptop screen sitting too close to a fire.. heh, but it was still usable.

I bought a 2nd-hand 12v 2A power supply without branding. I intend to use it on a DVD player. Coming from the street market makes it dicey because anything in that market could be from someone’s dumpster dive. To ensure it’s useable I used a DMM to measure the volts. It started at 18v but continued to gradually climb. When it passed the 20v scale on the DMM, it quit reading. So it would probably go even higher in the next scale.

I expect the voltage to be higher than rated because the 12v rating is expected to be a measurement under load. But my whole point is to check whether it is safe /before/ driving the appliance. Seems strange how the volt reading kept increasing. Is that expected? Is there another test I should do?

My drip maker shuts off. This is very frustrating, since no human should attempt the consumption of six cups of coffee within thirty minutes.

I'd like to get rid of this timer, but I can't see anything obvious on the board. Is it most likely to be in that little processor at the top left of the coated side?

lmao some of these replies are exactly the sort of thing you'd expect from reddit in like, 2011. For reference, even mildly scalded coffee tastes better than that instant shite, and I'm not drinking ut for taste.

I got a used ultrasonic cleaner with liquid damage for almost nothing and I am trying to repair it. So far I've confirmed that the board has a short circuit between live and neutral somewhere after the relay. Also, while reverse engineering it, I noticed something that seems weird. When the relay closes, it adds C3 in parallel to C2, both feeding the logic circuitry.

I am helping a friend to repair her amplifier. A different friend took a look at it, and they were able to identify the circled part as being the one to blame. However, apparently this is a part that was made specifically for this amplifier and is no longer made, so my task is to figure out what to do. I have some electronics expertise, but mostly I was recruited because I am good at finding things.

However, it would be a good start if I knew what this component was. I've not been able to find it in any of my reference materials, so I was wondering if y'all might be able to help. The person who identified this part is not able to help clarify, as she's off the grid for the next 3-4 months.

(On the off chance that someone here has some specific expertise on this particular amp, it's the Kenwood KA-3020SE)

Edit: Now that I know it's a potentiometer, the biggest challenge is understanding what 200KBH what is necessary to replace the part. It's a 200kΩ one, that's straightforward enough. It also seems that the "B" means linear response (found by checking my electronics reference book section on potentiometers, and cross referencing with other balance control pots for other amps, which specifies linear). I'm puzzling about what the H could mean though.

The big challenge, I'm told, is finding a part that will physically fit. There are 6 contacts on the part, which means it's a dual ganged potentiometer. However, most that I can find online have the pins in a 2*3 arrangement, like this, whereas this one is 1x6, like this.

I recently got a nice office chair for Christmas with heated massage functionality and it uses a barrel plug to power it but I have to be super careful to not pull it or damage the barrel connector in any way. I wish there was a magnet conector for these things in case of a yank pull and was wondering if anyone had heard of some adapter like the one I pictured above.

So I have an idea of a habit builder (also I think it would be fun to build)

Essentially, one piece tracks the habit, and one piece unlocks doors (small, in a grid) based on habit trend. Inside each door would be a "prize".

My question is about the small doors.

• Is there an example of small unlocking like this I can use to expand to multiple doors?

• The idea is there might be more doors than pins on the microcontroller. Is there a board I could put inbetween, or a special technique since they are on a grid, to accomplish this?

I have a Roxim Z3EK bicycle headlight. This light is supposed to have a low and high beam function, but I can only get the low beam to work. So far, I have tried:

• grounding the green wire
• sending 12V+ to green
• sending 12V- to green
• bridging the green and black wires
• bridging the green and white wires

I emailed the manufacturer asking for a wiring diagram, but no response.

I appreciate any guidance y'all might have. Thanks!

I could really use some help getting oriented on a project that is intended to be used as part of a Christmas / White Elephant gift tomorrow.

The idea behind my project is essentially that when a wire is cut, music plays from one of these “singing card” programmable speaker module. The one I have uses a 4V lithium battery cell.

I already have the programmable speaker module configured to immediately play music as soon as its power switch is moved to the "on" position.

In exploring possible ways to go about this, I realized that what I am effectively doing is building a tripwire circuit.

The examples I found were very simple, involving an NPN transistor (2n2222), 10KΩ resistor, battery, and DC Piezo speaker.

In my case, there’s no piezo - I'm trying to handle the entire load that would otherwise be running through the on/off switch.

With my initial attempt, I wired +4V from the switch to the transistor's collector and then separated the collector from the base with a resistor. I connected the emitter to the pin that, when the switch is engaged, would send 4V through and power the module.

Initially, all I got with the “Tripwire” disconnected was rapid clicking from the module's speaker as it cycled on and off. I reduced the resistor to 1KΩ and then 510Ω to get longer runtime, but it was still restarting. I jumped down to 22Ω and that stopped the restarting while introducing a new concern: that resistor quickly climbed up past 100C while the “tripwire” was connected. Without the tripwire, the I don’t want to start a fire, nor do I want the battery to die while this all sits in a box.

Someone suggested that what I actually needed was a MOSFET, so I ordered a hobby kit with various FETs that would get here in time and am now running into a new issue - I can't get the MOSFETs I have to turn fully on and let current through.

I have the resistor connected between Gate and Drain, +4V going to drain, and the load from the module on Source.

With an RFP30N06LE, I get about 2V output to Source. With an IRF840N, I'm only getting 0.9V.

In my photos, the orange wire is +4V, brown connectors the the circuit that ultimately powers the module, and blue is the “tripwire” that pulls down to GND.

I've attached a couple of the diagrams I have been referencing, as well as one I quickly drew outlining my particular application.

I'm starting to feel like this circuit design isn't actually applicable in this context and that what I am going to end up needing is something far more complex that involves parts I don't have on hand. At the same time, I'm worried that I'm about to give up when I'm only a small adjustment away from success.

EDIT / Update:

So far, I have been trying to place the load (full speaker module) after the emitter or source, depending on component used - mostly a limitation of trying to set up the circuit to bypass the on/off switch.

I shifted my attention to just the speaker itself. The good news is that I had success with both NPN and MOSFET, however the audio quality gets so degraded that this approach is not viable.

Update 2: Went back to the NPN Transistor, found a sweet spot at 330Ω where the speaker module does not reset. Resistor seems to stabilize at 40C. Probably going to roll with this and see what happens, try to plug in batteries just before delivery so I can avoid the situation where the battery has died before the right time.

Hi,

I am thinking about the best way to transmit 5 single ended signals from one board to another as well as ground and 2 power rails. I was thinking cat5e cable with a standard rj45 plug but as cat5e is twisted pair I'm concerned about crosstalk.

The cable between the two boards would be a maximum of 50cm. 3 of the signals are addresses for a multiplexer that would change at a maximum speed of 2ms per change. One of the other signals is a 20khz pwm signal. The final signal is a zc detector for mains so max Freq of 100/120hz.

There may be high current switches at ac line frequency (50/60hz) near by.

Would single ended transmission with cat5e cable be okay for this or would I need differential signalling? If I need differential signalling, what sort of cable/connector could I use?

Any help is appreciated

Thanks

Hello guys,

I am planning to build a weather station as an electronics project. It is supposed to be a couple sensors (temperature, humidity, air quality for example) connected to a microcontroller (probably via I²C, because I'm currently interested in that and picked this project as an excuse to do something with it), and a basic LCD display to show the current data.

For this I want a small microcontroller that can collect the stats from the sensors and show them on the screen, so nothing too fancy. I want to actually deploy this on my balcony, so I don't wanna sacrifice a Pi or something along those lines. Ideally something with a sleep mode so I can run it off a button cell. In order to use I²C and an LCD screen I would need around 9-13 pins, depending on the LCD. Plus some additional pins for buttons, means something with at least 16 GPIO pins would be desirable.

I was eyeing out something from the ATtiny family. Ideally it would be a through-hole-mounted chip as I want to use it on a breadboard first (and probably permanently). The only DIP chips are fairly old tho so I'm not sure if they're easy to use nowadays. We used an ATtiny461A in university and had to program it via a Windows XP VM, which is an experience I would not like to relive.

I'm not afraid to get my hands dirty writing raw C code without an stdlib.

While the WiFi functionality of the ESP32 is appealing, I don't know if I want to condemn one of them to a life on the balcony. I would rather use them for one-off projects instead and use something simpler for a long-term deployment.

The following are some ideas I have that I might want to add to my project later, but they're just optional features and I don't necessarily pick the microcontroller based on them:

• Tracking/Logging sensor data over time, e.g. hourly. This would require some fairly accurate timing in order not to drift
• Networking, so I can access the data via my local network

If there exist microcontrollers that fit my criteria I'd be happy to hear about them! I'm not an absolute beginner to electronics, but I've never shopped for microcontrollers before.

Im working on a board for controlling a few linear actuators. They will at full load draw something like 10A, and will be powered by a 24V (or so) LiPo pack.

I have a few H-bridges and as expected when the power is cut off, there is an inductive kickback of about 10A. No PWM, they will be turned on and off occasionally only.

I havent been able to fibd anything on if a LiPo pack would be able to take this reverse current, or if it needs some sort of protection. It also lasts for quite a short time but I'm new to batteries so I want to be sure its not a problem.

Would apprecaite any help :)

cross-posted from: https://beehaw.org/post/23519524

Working on a project where I essentially need a sizable monochrome display - basically a clock display.

Any ideas where I could source a sizable one for fairly cheap, including a control module?

UPDATE: the commenters' verdict is unanimous: this is not a good idea, because it will damage the iron tip of the soldering iron. Thanks everyone!

These sort of sponges are sold for cleaning the tip of soldering irons:

Now, maybe it's an odd question -- but is there any reason not to use one of these kitchen scrubby things instead?

They are way easier to get, plus they are cheaper.

I'm wondering mainly:

• can you think of a reason why it could be dangerous to use the stainless steel one? (like, poisonous fumes or something)
• would it hurt the soldering iron tip?

I'm always struggling to desolder high heat circuit boards like pc motherboards because they used high heat solder. Sometimes I can get it hot enough that I can mix in some lower temp solder but it's always a pain. I've also used my rework hot air at 500* plus the soldering iron at 500* and gotten it, but that's a pain as I only have two hands. Right now I'm replacing the Nec/Tonkin caps on a ps3. Fortunately removal is simple with a chisel, but getting the pads ready for soldering is a huge pita.

Given the endless problems with attempting to properly initialise ALSA with the qualcomm chipset in my device, I've resorted to the idea that I'll be designing a larger case, with a larger screen (and hopefully no shitty curvy corners) and an integrated DAC with probably a small headphone amplifier.

Ideally, I would like this to be addressable, and have the facility to run an equaliser on-board that can be configured via the USB connection, although I'll settle for bluetooth if the former is too complicated. It will also need to fit inside the phone housing (which will likely be around 9-10mm). I plan on an aluminium frame, so heatsink facilities should be easily manageable. The USB connection will, of course, need to be a passthrough connection to facilitate charging the phone - having a separate USB-C socket on the board is fine, I can probably adjust for this.

Am I setting my aspirations too high, or are there components available that meet these specifications?

This is from a section on why decoupling capacitors should be attached to CMOS chips. It shows current spikes during transitions. Which then because of the inductance of traces connecting power to the chip, will cause the power rail voltage to droop.

But why is the ground voltage also shown to rise? What does it even mean for ground voltage to rise when ground is what voltage is measured against?

I bought a nest gen 2 thermostat to play with a open source project that revives old nest thermostats (https://nolongerevil.com/). Since I don't want to install it into the home, because it will be a toy. I was thinking of building a test rig using a arduino or esp32 to simulate a HVAC and indoor temperature. I'm IT guy, not a HVAC guy, I think this would be a good learning project. Any suggestions?

Two questions

1. But would you trust a repaired board?
2. What makes a triac short out like this?

In the linked picture there are two power supplies from two 400V electrical heaters. Brandname ADAX, model clea. The thermostats have been removed.

The heaters are supplied with two phases only, no third phase and no neutral.

The terminals on triac in the power supply on the right shorted out during the night, luckily the occupant of the room was awake, because this happened in a bedroom. The power supply on the left was pulled from a functioning heater for reference.

I'm fairly certain that only the resistor, triac and board have been damaged. And I'm also fairly certain that I can fix it.

The burned heater is only 1200W, but there's a lot of vias stitching the two layers together. So while it's only 3A, and the board is housed in fire resistant plastic, inside a metal and glass casing, it's also 400V and I don't know if I want to trust the solution. Even if I can get all the parts, including shipping, for a tenth the cost of a new heater.

If I decide to repair the board I'm going to be replacing the triac, R8, R9, C9, and the varistor.

So my late uncle was working at Siemens and had a "little" home workshop/lab with resistors, capacitors, ICs, switches, soldering boards, wires and what there is. He learned something regarding radio (german: Nachrichtentechniker I think). Among others there was a self built radio clock (that got quite warm, plugged it out bc of safety concerns)

Now I am getting into microelectronics and roughly know what there is. But I only know that I should not use the leaded soldering tin (bc lead) - is there anything else that is unsafe because of old standards or aging? What should be safe to use?

cross-posted from: https://lemmy.dbzer0.com/post/57424638

The thermostat is dead in my strange¹ fridge with no replacement parts. I posted about the mystery component before.

There is a metal plate that appears to sandwich a single small loop of refrigerant (guessing!). Mounted attached to the backside is a coil with a ground and two wires marked to handle 220v. One of the leads connects to the LOAD wire on house mains and the other to the (now broken) thermostat.

I can only imagine that it’s a heating element for defrosting (as suggested). But I struggle a bit with that theory because I’m surprised the fridge would ever get cold enough to justify defrosting.

Anyway, I wired the mystery coil directly to mains and left it for 10 min or so. The temp of the metal plate did not feel any different. Is that expected? Metal is naturally cold at room temp and that did not change.

I would like to understand it because I cannabalised a simpler t-stat from another fridge. The t-stat has no connector for whatever the mystery component is.. it’s just a switch that connects two wires. I don’t know if I should just omit the mystery component, or if I should wire it in series with the new t-stat, or keep it attached to the old broken t-stat and wire that in parallel to the new t-stat.

¹ I say strange because there is no freezer-fridge vent. So the fridge is independently cooled.

As my collection of small components grows, it is becoming... messy. And it is not even large yet, I have only done a handful of hobby projects.

Recently I had the realization that I can make use of Chinese 'Sample Books' to keep the smaller reel components well organized. I have ordered 0402, 0603, the 0805, and two empty books to use these as the basis of my organization:

What made me originally select the strategy of keeping the original packaging that the components came and stuffing them into project-specific bags is the labeling. My first attempt at organization was to to use small storage boxes for sorting, but when I tried to keep single labeled components per box I ran out of boxes very quickly... When I mix multiple components in a box (like different photodiodes, for example), then it is difficult to label them separately without using too much space.

I am curious about what methods others use for keeping a component library organized and easy to search.

I’m trying to simulate a NAND gate using MOSFETs in QUCS, but I’m having trouble getting it to work. Could someone help me figure out what’s going wrong?

All the resistors are set to 1 kΩ, the supply voltage is 1 V, and the square wave generator has a period of 1 ms and 2 ms with a 10 ns switching time. When I draw the same circuit in Voltsim on my phone, it works as expected.

I’m replacing a trivial pcb in a battery pack for a small fan. It’s 6V (4xAA) with a SPST top left and a USB socket top right. But why on earth would the power line on the pcb follow that curved path? There are no other components, just the 2 ends of the battery pack and a plastic housing.

Maybe just ‘because you can’?

So I am working on an Arduino project and have trouble communicating over UART.

I have a SIM7600G-H 4G Module from Waveshare and hooked it up to an Arduino Nano ESP32. The connections are as follows:

SIM7600<->Nano ESP32

TXD<->RX0

RXD<->TX0

VIN<->VUSB

GND<->GND

CTS<->D3

RTS<->D12

It mostly works, I can send AT commands and receive responds. However sometimes I only receive parts and chunks are missing or being send to the next command. I strongly suspect RSPs ("unsolicited result code") to be the reason behind it. As documented in the manual RSPs are being send without an implicit action and happens for example if the module receives a call or SMS.

I have read about hardware flow control which seems to theoretically solve the problem of those module talking over each other and have connected the CTS and RTS pins to generic digital pins. According the manual the SIM Module it has hardware flow control enabled as an default.

On the Arduino side of things I have added these lines in hopes of enabling it, however I do not see a change, they do not return any error but I still see data missing. I have also tried swapping CTS and RTS just for fun, but without any luck.

Serial0.setPins(-1,-1,12,3);
Serial0.setHwFlowCtrlMode(UART_HW_FLOWCTRL_CTS_RTS);

Here are the logs which shows some responds being cut off.

20:57:47.991 -> Send AT command: AT
20:57:47.991 -> Response: AT
20:57:47.991 -> OK
20:57:47.991 -> 
20:57:47.992 -> Send AT command: AT+CPIN=1234
20:57:47.992 -> Response: AT+CPIN=1234      <- This responds ending is cut off
20:57:47.992 -> Send AT command: AT+CSQ
20:57:48.025 -> Response:                    <- This responds start is cut off
20:57:48.025 -> OK
20:57:48.025 -> 
20:57:48.025 -> Send AT command: AT+CREG=1
20:57:48.059 -> Response: AT+CREG=1
20:57:48.059 -> OK
20:57:48.059 -> 

And this is my function to send those commands.

char* SIMClass::send(const char* command) {
  // Clear buffer
  while (Serial0.available() > 0) Serial0.read();
  Serial.print("Send AT command: ");
  Serial.println(command);

  unsigned long timeout = millis() + 10000;
  char* response = (char*)malloc(1024 * sizeof(char));
  uint16_t index = 0;

  Serial0.print(command);
  Serial0.print("\r");


  while (Serial0.available() == 0) {
    if (millis() > timeout) {
      response[index] = '\0';
      return response;
    }
  }

  while (Serial0.available() > 0) {
    response[index++] = Serial0.read();
    timeout = millis() + 1000;
  }
  response[index] = '\0';
  Serial.print("Response: ");
  Serial.println(response);
  return response;
}

After enabling hardware flow control unsing Serial0.setHwFlowCtrlMode(UART_HW_FLOWCTRL_CTS_RTS) I expected Serial0.print(message) to wait until the SIM module is not busy and vice versa. Am I wrong in that assumption? Am I missing something else or is it maybe recommend to implement the hardware flow yourself?