9
votes
Accepted
Is it possible to make an MCU hang by messing with its power?
Very possible, if supply, and especially supply decoupling, is insufficient.. It's even been used extensively in breaking into and reverse engineering electronics: It's one way of glitching the ...
- 100k
7
votes
Accepted
What is the science behind percussive maintenance?
Re: how this happens in the first place, or how it happens again soon after "fixing" it-
Heat expansion. Power on your device, and everything heats up, and expands slightly. Power it off again, the ...
- 86
7
votes
Is it possible to make an MCU hang by messing with its power?
Regarding code getting stuck in a while loop, it’s always wise to specify an iteration limit, if only to generate some indication that something has gone terminally wrong. Regarding power ...
- 7,855
6
votes
Difference in current transformers conection for ground fault detection
There are (at least) five ways to measure the earth fault current (zero sequence current) on a system.
Residual or "Holmgreen" connection of the A, B, and C phase CT's.
This physically implements ...
- 9,071
5
votes
What causes a faulty Linear Voltage regulator to output wrong voltage
LM/KA78xx regulators are almost impossible to get to oscillate (unlike many other types such as LM1117, LM7905 etc). Others are either repeating folklore or are much (un)luckier in this regard than I ...
5
votes
Accepted
Amplifier Repair - How can I find a replacement transformer?
Sometimes transformers have a thermal fuse underneath the black tape wrapped around the coils. You could carefully remove the tape and replace the thermal fuse if there is one. For example - http://...
- 4,050
5
votes
Accepted
Why does AC input have a parallel resistor and capacitor?
The HTCC capacitor is used for filtering and interference suppression of high frequencies as well as the L1/L2 is used for common mode rejection. The resistor is used to discharge a possible load at ...
- 511
5
votes
Is it possible to make an MCU hang by messing with its power?
Does your MCU have a "brownout" reset vector?
By default, most BSPs define this vector as an endless loop, so an instability in the power supply or an unclean power cycle will make the CPU ...
- 12.8k
5
votes
Accepted
Do I need to ground the thermal pad on the MAX8808?
Do I need to ground the thermal pad on the MAX8808?
Read the data sheet page 5: -
It is likely that this chip isn't working because the pad isn't
connected to Gnd?
Impossible to say because the ...
- 473k
5
votes
Troubleshooting a new PCB
The 2N7000 MOSFETs are not quite rated for logic level applications, especially for LSTTL. They may be getting into linear mode and dissipating enough power to cause excessive current. But the 1k pull-...
- 7,645
5
votes
Accepted
Ground fault detection on an ROV
To detect a grounding fault it is, perhaps counter-intuitively, necessary to create a deliberate connection to ground.
simulate this circuit – Schematic created using CircuitLab
Figure 1. ...
- 180k
4
votes
Can hair short an electrical circuit?
No, not at this voltage. But it could 'open' the circuit and change the impedance of the circuit in the case of a CPU socket. If hair got in between one of the pins and the contacts there could be a ...
- 88.8k
4
votes
Class A amplifier asymmetric distortion mystery
You got it confused.
Class A simply means that the output devices do not switch off when processing a signal below rated power.
Class A can be implemented single-ended (with one power transistor ...
- 81.7k
4
votes
Accepted
Fault current indicator - what should I do?
Yellow indicator here indicates there was a difference between live and neutral current and the difference is suspected going somewhere it shouldn't.
The fault may be not only in some appliance, but ...
- 9,686
4
votes
Would ground fault cause breaker to trip if neutral not bonded to ground in main panel?
simulate this circuit – Schematic created using CircuitLab
Figure 1. The OP's setup.
Will current flow through the breaker?
Yes. A current will flow through ground back to the utility supply ...
- 180k
4
votes
Is it possible to make an MCU hang by messing with its power?
Yes, this is very well possible.
I've faced a similar issue on an ATmega AVR MCU where power sequencing at the start causes some devices to hang on bootup.
And the only place in the code it could be ...
- 3,842
4
votes
Do you think the output voltage is caused by an old capacitor?
If the capacitors are original they are almost certainly bad. If they've dried out you'll get a lot of ripple and low average DC voltage. Old tube equipment that hasn't been used in a long time should ...
- 27.9k
4
votes
Ground fault detection on an ROV
This is a variation of the other answer, but uses strings of a red LED, 7.5 V zener diode and series resistor, instead of lamps. This also doesn't switch the supply off in the event of a fault.
The ...
- 7,163
3
votes
What causes a faulty Linear Voltage regulator to output wrong voltage
All these linear regulators require capacitors around them to keep them stable.
If you do not include those, the device will not operate as you expect.
See this answer for more information.
- 47k
3
votes
Class A amplifier asymmetric distortion mystery
So, I'm back with an update! Thanks again for all the answers and hints, I managed to repair it! I'll post the solution here, in case anyone is interested or someone else encounters the same problem.
...
- 171
3
votes
Accepted
What's the use of the ground socket of an ungrounded GFCI receptacle?
Despite its name, a GFCI does not look at ground current - it only looks for a difference between the line and neutral currents passing through it. If it finds a difference of 5 mA or so (maybe 15 mA?...
- 60.7k
3
votes
Accepted
What types of fault protection is recommended for low voltage power supplies?
You should consider:
Fusing on the AC side of the power supply to protect for possible transformer primary shorts and secondary current overload.
Crowbar over voltage detection on the output that is ...
- 57.9k
3
votes
Why does one of my HiFi speakers only start working after several minutes?
no, I just checked and they are fine. Headphones also disable the speaker-out on this model, probably that's obvious
Ok, here's the service manual with circuit diagrams. Power amps at pages 39-40 ...
- 7,152
3
votes
Accepted
X2 capacitor. Test if failed open
There's a reasonable chance the surge killed the zener, and it's gone short.
Your measurement of 0.9V across the series resistor (perhaps 50 or 100 ohms?) indicates that current is flowing (assuming ...
3
votes
Accepted
Can a ground fault be caused by something outside the home?
A GCFI (or RTD) works along these principles: -
It monitors hot (live) and neutral wires and if it sees a current flowing down one wire that isn't flowing in the other wire (called a differential ...
- 473k
3
votes
Searching for 'ground fault' on DC power supply, 0VDC to ground
simulate this circuit – Schematic created using CircuitLab
Figure 1. Earth fault tester.
Try wiring two 120 V lamps as shown in Figure 1. If the system is floating both lamps will light at ...
- 180k
3
votes
STM32F4 HardFault_Handler
First of all put a hard fault handler that will give you the information about program counter and stack pointer.
Example: https://mcuoneclipse.com/2012/11/24/debugging-hard-faults-on-arm-cortex-m/
...
- 9,096
3
votes
Can an electronic system be built with absolutely no single point of failure?
Theoretically, it would be possible if somehow we could detect every possible fault (which we cannot - see next paragraph).
The primary problem is complexity; every time we add a component, we add ...
- 22.6k
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