Ask Electronics

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?

Trying to trouble shoot a cheaper wireless meat thermometer. It was working find when put away last year.

Now won't turn on or respond when put on charge.

The lithium pouch cell looks fine and reads 3.5v at the battery tabs. No voltage read on the output of the small circuit board attached to the pouch cell. A bit of googling has lead me to believe it is some kind of "battery protection circuit" or possibly a BMS or charge controller. I have found many similar ones but no exact match on AliExpress. It reads QLD-3036.

If anyone is familiar with those little boards can they let me know

If there would be any reason it would be stopping power getting from the battery to the main unit?

If there is some easy way to reset the board?

If the small board modifies the voltage of the battery at all and if not would it be ok to bypass the small board and supply dc to the main board where the red and black wires connect for testing purposes? I have a variable power supply and would have no issue with converting this unit to run connected to a power supply permanently.

This is what's known as a Master 4 module in a LHM550 Liebherr harbour crane.

Earlier this week it was hit by lightning causing the module to output a combined 8 volts out on the can line 3 circuit.

The rest of the module works fine, all functions work except anything related to can line 3.

Can line 3 output is the 2nd white plug port on the top left of the photo.

I know it's probably a long shot but does anyone have any familiarity with these kinds of things?

I have added a couple more photos in the comments.

I couldn't visually see any sort of obvious fail point.

I recently acquired an old electro-cautery unit. Think it is from 1910s or 1920s. Has a big old multi tapped torodial transformer running to a couple of connectors/poles. It is by F. Geiger of Philadelphia. Wood case is labeled 110V. 60 CY. and 4V. 100A. Seriously old school cool and a little horrifying.

Insulation on power cord was brittle as was insulation from secondary to pole. Both have been replaced. I used crimp connections on the primary wires (didn't measure gauge but it's on the order of 20 AWG). I was in a hurry to test and will eventually solder it properly. I added a switch to the new power cord.

It works with output voltage varying from 0.1V to 4V. It gets a woodburning tip glowing orange at setting 4 (2 volts or so). Should make a great woodburner and be useful if I ever need to interrogate someone.

There isn't really a way to ground it and the screw on the control knob is electrically connected to the secondary. I have a gfci adapter that I could plug it into. Basically, if the transformer shorts, 110V could be exposed on the face.

There are two holes on the face plate, the power cord is running through the largest and the other is empty. It may have had a foot pedal.

I want to add a RGB indicator light for voltage level using the small hole. It's a little tricky to tell when the tap is lined up and you're getting voltage. A green - yellow -red fade and maybe white for NC. I have a spare Arduino Nano clone, but am not sure what circuit to rectify the AC with for the ADC. Maybe an Op amp follower? Power supply would be a 110-5v usb charger board. I would prefer to avoid a dual rail supply or higher than 5v.

Thoughts and suggestions appreciated!

Is this feasible at all?

My idea is to have a battery of 112 Li Ion cells in series, ending up with a nominal voltage of about 414V. This is apparently how car batteries are configured as well and it's the easiest for an EGS002 inverter.

Charging however is quite difficult as stepping up to those voltages is not trivial.

The idea is to have a charge pump circuit on every single cell. 2 mosfets for charging, a capacitor, 2 mosfets for discharging. The capacitor would charge from a 4.2V supply and discharge into the battery.

The mosfets on the battery side can be controlled with optocouplers. The gate voltage is provided by cells further up in the chain so the gate always has at least 12V on it.

Is this a bad idea? Things that come to mind are the mosfet losses. Essentially the on resistance counts 4 times per cell but usually the rDS on is in the 20 mOhm range, so 80 mOhm per cell.

Balancing is much easier this way.

Perhaps a compromise that charges several cells in series and watches the balancing could work too if efficiency is the biggest reason against this.

I'm aware of the safety considerations.

Can anyone help me identify this touch sensor module from a UK home bathroom light switch?

The IC is a QT113 charge transfer touch sensor, the only writing on the board is SAT 02.

I'd like to know enough about it to order replacements.

https://sopuli.xyz/pictrs/image/256ab3e9-90b3-4e38-affe-5c716332cbc3.webp

Hey!

I have made a 24v supercapacitor bank which is made of 12 2.7v 20F supercapacitors, balancing resistors, charge resistor and a diode to bypass the charge resistor when in discharge mode.

The mistake was made when it was connected to a mean well LRS-100-24 which is a 24v 100W supply. When I powered it up the other control board was starting and stopping - the power supply was current limiting. Im not sure what voltage would have been applied to the supercapacitors but I think it wasn't high as the microprocessor on the other board was constantly resetting so the supercaps were not charged.

This happened for a maximum of 60s until I realised what was wrong and disconnected the caps.

My question is - will the capacitors be damaged from this event? Any help is very much appreciated.

Thanks

So far I have been using RCY connectors to connect some low power fans for a custom thingy (fursuit head, this will be relevant later (space limitations)). They have a fairly low power draw, so around 5v 0.1A.

This has worked for around a year, but as there is a lot of movement where I use it, the power leads have ripped right at the connector. It looks like this is caused by the lack of any strain relief as the connector is crimped and does not have the usual stress relief thingies, which are often seen at other stuff like psu cables, usb etc.

So I'm looking to upgrade / replace that with a different connector. I'm looking for one which has:

• stress relief against bending
• is twistable / unidirectional (so something more like a barrel jack / headphone jack)
• is small / slim (I have very limited room that's why I initially used RCY). The size is mostly limited in thickness, not length.
• is able to carry the very low voltage and current of 5v 0.1-0.2A (so basically anything will do that)
• available in germany (most likely most things should be)

Things I have already considered:

• 5.5mm 2.5mm (/2.1mm) barrel type connector --> too thick sadly
• trying to protect the RCY plug with stuff like shrink tubes --> doesn't work, just slips off
• thinner barrel type connectors --> can't find a matching set of cable with plug and cable with receptacle

Rn my best bet seems to be 2.5mm headphone jacks. I do have the feeling that there might be something better out there, so that's why I'm asking here.

Any help would be very appreciated. Thanks in advance!

Edit: Thanks for the suggestions so far, I forgot to add it to the list of the requirements that, the plug needs to be round, as one of the issues I had is that the 90° edges of the plug can get caught in the fabric. So I'm really looking for something round, so something without sharp hooks and release mechanisms.

All the fridge repair videos I have seen demonstrate how a fridge with a damper works -- in which case all the cooling happens in the freezer and a vent with configurable damper diverts some cold air to the fridge. Perhaps that is a US design.

European fridges are apparently different. The fridge and freezer are separate with no interconnecting vent. No fans either. The freezer is surrounded with coils embedded in the surface panels. The fridge has a plate with embedded tube for coolant. I am surprised that a plate the size of a large dinner plate/platter is big enough to cool the whole fridge.

The plate also has a tube in a loop of tubing that is not embedded into the plate but against it. The two ends of the tube join into a molding with 3 wires going to the thermostat (one of which is a ground wire). What is that thing?

There is a separate wire that goes to the thermostat. I think that is the probe that actually reacts to the temp.

I couldn’t easily send pics because the plate does not come off. I can barely pry it to get an eyeball behind it. I think everytime I bend the plate to see behind it I probably bend the tubes carrying coolant (not good).

Hey I'm not sure if this is the right community for this but it seemed applicable, let me know if I need to delete!

I am seeking anyone with a Square brand magstripe reader (not contactless, magstripe specifically) willing to run a quick test for me. It's just:

• Connect Square to computer
• Open any text editor
• run any card's magstripe (except a chipped payment card. Costco, non-chipped card, gas station rewards card, etc will work fine) through
• Does it type out the data from two or three tracks in the text editor, the way traditional USB readers do?

Thank you for your time reading this, and double thanks for anyone willing to test. This is as close as I can get to trying before buying lol.

I am wiring this up, and I would like to limit the current being drawn from 18v DC/DC converter.

What would be the simplest way of doing this?

cross-posted from: https://slrpnk.net/post/26897688

Either the relay is broken or the thermostat. I know this because I could force the fridge to run by hotwiring 220V across the common and run pins then briefly jumping the start pin to the run pin (thus sending 220V through the start winding for a split second).

The thermostat assembly has too many wires to know what to measure resistance on. But I figure that the thermostat can be black-box tested simply by checking whether it sends 220v to the relay switch. There are THREE wires involved (in addition to ground). With the relay removed (thus compressor disconnected), I plugged the fridge into mains. Got these measurements:

common pin to run: 220v
common pin to start pin: 20v

I’m tempted to conclude that the start winding /can/ accept 220v (proven by hotwiring), but 20v is also sufficient to cause enough motor movement to get it started. Does that sound reasonable? Can I conclude that the thermostat works and the relay is toast?

It’s hard to be confident without a service manual, particularly when the relay¹ has continuity. The common pin goes through a cylinder marked “Klixon MRP342LZ-32Q1”, which as 0.5 Ω. The start and run pins go through what seems to be a ceramic disc having 45 Ω. Is that reasonable?

I am ½ tempted to attach the relay, bypass the thermostat, and wire the relay to mains with start-run jumped persistently. Is that crazy? I assume the relay would internally disconnect the start winding. The fridge has no fans AFAICT, so no need for anything else to have power in this test.

¹ The relay I have has part № “A 3B7 8100” printed on it, which I cannot find online. But it looks exactly like this one.

Update

I hot-wired the relay. It was non-trivial because the relay has /3/ inputs. After studying it closely, I realised that one of the inputs (apparently for the start winding) is phony. The spade connector that attaches to it ultimately goes nowhere. When connecting the remaining 2 pins to load and neutral for the house mains, the fridge started and ran just fine.

Thus I have to conclude that the thermostat went bad. And replacements are not sold. However, Amazon has what’s claimed to be a universal fridge thermostat. It’s cheap, but I boycott Amazon. I think I will wait until someone throws out their fridge. Perhaps I can just take any thermostat and make it work.

Hello everyone. totally nob here but very enthusiastic. I'm trying to repair an old SA610 pioneer amp that is shorted. I remove the power transformer and it's ok, generating 64 volts between red and orange as 32 volts between any of these and the white wire.

So, the short lies elsewhere, but I'm having a little trouble trying to find it ou. Can anyone help me?

I have an older electrical device which I would like to switch to charging with a USB C cable and a standard USB power supply. The device's power supply unit supplies 14V and 400 mA, so 5.6 W. The device documentation certifies it for 12V with 2 Ah.

I found a useful answer on stackexchange about the Source Power Rule for USB 3.1. This implies to me that my device is not compatible with 3.1 because at a power draw below 15W, PD 3.1 defaults to 5V.

According to Wikipedia, a USB4 DFP is required to supply at least 7.5W Type-C current, which is above the power requirements for my device.

Based on this, it seems to me that the power supply of my device is too non-standard to be supplied by a standard USB power supply. Have I understood this correctly?

Thank you for your help.

I recently got a bunch of old 80's crts which I cant find any information about online.
I do have the service manual tho link
Looks like standart composite with external Horizontal and Vertical Sync to me but I'm not 100% sure and I dont want to fry anything

Thanks,
Oha

(Electrical Discharge Machining)
In terms of current, voltage, frequency, rise time, etc. What makes this one special for switching topologies?