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Questions tagged [protection]

Ancillary circuitry added to a design that provides protection of the main circuitry to enable the main circuits continuing functioning. In some cases the protection circuitry is sacrificial, being destroyed or degraded in the act of protecting. But not all protection circuits may do this. ...

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Sense coil based leakage current meter (with LCD display)

This is the circuit diagram of the previous Leviton GFCI receptable without auto-monitoring self test. Do you (or others) know whether the current coming out of the sense transformer or sense coil is ...
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28 views

Testing the presence of GFCI Auto-monitoring Self Test circuit

This is the GFCI IC used: Does it have auto-maintain self test? Here are the internal parts of it. Anyone recognize if it has an auto-monitoring self test IC (or circuit pattern) or something? ...
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2answers
87 views

Can a thermal fuse of a higher rated current be used safely?

I want to replace a 115°C 250V 2A thermal fuse used in a fan motor. The only fuses available locally are 115°C 277V 15A. Can I use the higher current rated thermal fuse? Since it is a thermal fuse, I ...
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34 views

Resetable fuse leakage

I'm planning to use Resetable fuse PTC for cable protection of a sensor's cable. The sensor will not draw more than 40mA. So considering that PTC is not accurate and its affected by temperature I ...
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1answer
133 views

TVS bidirectional diode not working

10x bidirectional diodes 1.5KE400CA in series, balanced, then the chain in parallel for DC line protection. Breakdown voltage 400V per diode. Still got 10kV+ voltage spikes (picture below, x100000 ...
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20 views

Li-Ion protection IC starts in overdischarge mode

I have a problem with my Li-Ion protection IC. When connecting a charged battery with a 3-4V voltage I expect that the IC will start working (there is no problem with the voltage levels). For some ...
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2answers
33 views

Protecting a relay/SSR when driving AC window cover motor

I'm having trouble switching an AC motor. Relays spark and glue contacts, and SSRs start to flicker and not pass the full input after a while. The motor has 3 terminals for 230VAC mains. One is ...
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1answer
33 views

74LVC and similar… can a logic 1 output sink current?

Say I am running my 74LVC125 at 2.5V. At the A input I have a logic 1 and at the nOE input, I have a logic 0, so the device should be driving a logic 1 onto the Y output. With no load connected to ...
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74 views

Overvoltage protection circuitry choice

I need to design a input overvoltage protection for a 45W DC-DC converter rated for a 9-24V wall wart input (so, 45W / 9V = 5A input current at max). So far I've seen two approaches (schematics below):...
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1answer
103 views

High-side vs low-side reverse polarity protection

I need to make a reverse polarity and over-voltage protection for a fairly powerful device (45W @ 12V input) and after some research I noticed a weird peculiarity. A typical reverse polarity ...
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64 views

High voltage protection for UART

I need to create a high voltage protection module (up to 50 V constant voltage) for UART line with speed of 56.7 kB/s connecting an STM32 with external devices. I was considering darlington arrays, ...
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1answer
52 views

Protecting opamp inputs when powered down

I'm designing a circuit with an opamp buffer at the input, which runs of batteries. As the input does what it likes, the input of the opamp can see voltage even when the opamp is powered down. As the ...
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56 views

Overcurrent shutdown circuit

This circuit mainly consists of a high side current sensing circuit, a current mirror, an op amp, U1, working as a comparator, and a controlling PMOS, M3, to control the current through the load. Here'...
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1answer
25 views

How to add the TVS protection?

I'm still busy with my DMX splitter (soldered everything), however, I made a mistake with my TVS protection diode. I put it in series with 220 V AC, and nothing happens (no current flows). I expect I ...
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1answer
50 views

How build a practical AC over voltage protection circuit for the input of an arduino board

The input signal to my board is an AC signal. My board will process this signal. My board can handle 3.1Vpk-pk maximum without any damage occurring. In the event that my input signal exceeds that I ...
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1answer
95 views

Automatic Self-Test Circuit in GFCI outlet

What kind of self-test circuits or method do they used in the GFCI outlets generally? Is it just firmware or is there a physical addition (and what it is usually?) This is because after 2015, it is ...
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45 views

Linear power supply and mains filtering and protection

I'm designing my first linear power supply for my project which needs dual rail 12V (the regulation from 15V to 12V is on another board, 7812 and 7912). The +12V (+15V) rail will draw about 250mA, the ...
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1answer
49 views

Protect signal from noise in Arduino

I am trying to send a signal from the Arduino to a relay to open a switch. My problem is that my Arduino will be near the AC power lines. I searched for how to prevent the noise to ruin the signal ...
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65 views

power surge protection

I've seen power protection that uses: MOV (metal-oxide varistor) Inductor TVS diode Application Note: Transient Voltage Suppressors (TVS Diode) Applications Overview I didn't see any design ...
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3answers
58 views

How to connect LED strip to be powered by charger and batteries

I plan on using it mostly plugged in, batteries are there just for extra mobility and won't be used most of the time. Don't know lot about batteries so in first scheme I added a switch (pos. 1 ...
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2answers
87 views

How to measure output voltage of this Li-Ion battery circuit?

I've designed an AtTiny85 based Lithium-Ion battery protection/boost circuit that monitors the battery voltage and cuts the battery power to the external powered circuit when the battery dips below a ...
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1answer
35 views

De-rating / Re-rating criteria/theory for frequency in circuit breakers

I'm trying to spec a circuit breaker for a system that will be performing in the 3kHz range, and am not finding much info on how to calculate a new rating based on frequencies in this range (where ...
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1answer
53 views

Supercap overvoltage protection

I'm building a circuit where a supercapacitor will be charged over wireless energy transfer (basically two coils near each other). This means I can not guarantee the voltage feeding the supercap is ...
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2answers
455 views

How can I compare a TVS diode with a varistor?

For a 120Vac line protection element, comparing this TVS diode: With this varistor: The immediate differences I see are: The varistor is marginally cheaper The varistor specifies a maximum working ...
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1answer
122 views

Is the ESD and overvoltage protection for my ADC circuit sufficient?

I am currently building a data logging device for monitoring battery packs which contain 8 Lithium cells. The device will periodically log the voltages of all 8 cells, as well as log temperatures ...
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1answer
53 views

Exceeding Vmax rating of PTC Fuse

I am adding over-voltage, over-current protection in my circuit. My circuit/PCB has many DC-DC converters and these converters ...
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1answer
49 views

Safety Relay Circuit

I am looking for a way to add a relay-based safety feature to my BLDC controller. In case of an emergency the user must be able to push an e-stop (probably consisting of an NC contacts) completely ...
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97 views

Activated carbon face mask for protection against solder fumes?

What do you think about using a activated carbon face mask for protection against solder fumes as an alternative to using a fume extractor?
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1answer
41 views

Reasonable Li-Po Battery Protection Circuit?

I'm designing a circuit to monitor the voltage of a Li-Po battery (single cell 3.7v, 2500mAh, 25A) and switch off the battery when the voltage drops to a certain threshold. The Circuit will also ...
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3answers
104 views

thermal fuse as electrical fuse

I am trying to understand the spec of a Datasheet of a thermal fuse. for example the one below : https://nl.farnell.com/panasonic-electronic-components/eyp2bn134/fuse-thermal-cut-off-2a/dp/1832031 ...
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6answers
2k views

USB device with 2 ports - how to protect against user plugging in both

I've got a Full speed USB device which I want to provide 2 ports for - one each on opposite ends of the enclosure. This is so the cable can be connected wherever is most convenient. My MCU (atmega32u4)...
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0answers
24 views

Vector Shift for Islanding

I am looking to know how angle difference is accurately measured? Also why vector shift may cause issues with regard to loss of mains protection in distribution networks. Thanks
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2answers
127 views

Protecting yourself with latex gloves

Would wearing white latex gloves(doctor gloves) protects you from getting shocked when repairing electronics? And is there a reason why you seldom see anyone wearing gloves when dealing with ...
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40 views

Is there a Single Component/Chip for Performing Low Voltage Cut-Off for a NiMH Battery?

I would like to build a circuit that uses a single Ni-MH AA Battery. My circuit can work well with the 1.2v that the battery supplies most of its discharging time, and I would like my circuit to stop ...
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1answer
29 views

Protecting voltage sources against pushing or shorting into each other

I am designing a PCB where there is a load with peak power of 15 Watts to be powered from a user selectable voltage source. There are a 35V and a 24V sources and it should be only one of the voltage ...
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1answer
51 views

Measuring input voltage with 3.3V ADC MCU

I am designing my very first DC motor driver circuit. Right at the start, I want to be able to measure the input voltage to the system. The system supposed to work with external DC power supply from ...
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1answer
78 views

USB Broken problem

I have a problem with a device that I’ve built: It contains a LPC4300 microcontroller and it's supplied with 24V DC. I’ve noticed a strange problem when I connect it to a USB port. The device is used ...
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0answers
38 views

Chip(s) or solution to protect DC circuit with wide input voltage

I am looking for a solution to protect a DC motor control circuit with an input voltage of 12-55VDC from overvoltage, undervoltage, reverse polarity and overcurrent. Now, there are ICs doing just ...
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1answer
49 views

What will happen when taps at secondary side of auto-transformer are connected together (short-circuited)?

In case of Auto-transformer, there is only one winding, having three lead wires (1 for primary/input, 1 for secondary/output, and 1 common between both). At the secondary side (the output side), there ...
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1answer
28 views

Connecting a polyfuse (PTC / resettable fuse) without soldering

I want to connect up a polyfuse to protect a potentially flammable USB cable and a Raspberry Pi Zero in the circuit below. However it seems that most Polyfuses are supposed to be soldered and I'd much ...
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1answer
118 views

Full Load Amps vs General Purpose Amps

http://www.carlingtech.com/sites/default/files/documents/M-Series_Details_%26_COS_021114.pdf This circuit breaker have two different current ratings, depending on amperage range: Full Load Amps and ...
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1answer
54 views

Can high power USB destroy older devices? [duplicate]

My brand new pair of bluetooth headphones stopped working after charging them with a 2.1 Amps USB outlet. I can't turn it ON anymore. I do see the LED battery Green then I charge it though. I noticed ...
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0answers
62 views

High power / high current clamping circuit

I am looking for ideas on how to clamp high energy surges in the input of a high current / high power system. The input to the system is 24V. During steady state, the system sources 85A of current ...
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1answer
49 views

Proper Flyback Current Protection Circuit for Variable Voltage Solenoid Driver

I am using a darlington buffered op-amp to drive a solenoid motor at variable voltages (for variable speeds of actuation). Here is my circuit as it is now: I am wondering which of the two flyback ...
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1answer
50 views

Car 12V Supplied device - Requirements

I am currently designing a device that is intended to be used outside the car and supplied by car 12V socket (also during the drive). The question is: Are there any specific requirements for example ...
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1answer
35 views

How to determine the right trip point of thermal cutoff for 1/4 hp 3A 115V single phase ac motor

The Thermal fuse blew in my Ryobi DP102L drill press motor, while I was drum sanding. There were no markings on the fuse. The single phase induction motor is 1/4hp 3A (no load) 1750rpm on 115V AC, ...
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1answer
54 views

A lot of questions regarding lithium ion power supplies and power regulation with safeguards

Per a members request I am making a post compressing multiple possible posts into one and providing additional info. I am making a 18650 powered portable electronics workstation that will have many ...
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2answers
70 views

What would be the safest method to power a laptop (IdeaPad 510 15isk) from a 14.8v battery pack?

Looking at my existing power jack and measuring it crudely with a cm ruler it looks like 3mm diameter x 1 cm length. The laptop bottom and charging adapter both say 20v @ 3.25 A max. What would be ...
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0answers
75 views

What fan could I use to extract hot air from an oven?

I am making an reflow oven. I've decided to use the picoReflow to do the job and monitor it. The oven is originally a lab oven, and it doesn't cool quickly at all. It has a vent at the top which I'd ...
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1answer
56 views

A question about lightning protection for a sensor mounted outdoors

There is an ultrasonic-windsensor which will be mounted on a bridge in winter. Maybe several of them. It seems like for outdoor use this device should be earth grounded(probably through mains earth? ...