Questions tagged [protection]
Ancillary circuitry that protects the main circuitry in case of a fault. Examples of faults protected against are: overvoltage, ESD, overheating, and overloading (too high of a current draw). In some cases the protection circuitry is sacrificial, being destroyed or degraded in the act of protecting.
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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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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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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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Overvoltage protection circuitry choice
I need to design a input overvoltage protection for a 45 W DC-DC converter rated for a 9-24 V wall wart input (so, 45W/9V = 5 A input current at max). So far I've seen two approaches (schematics below)...
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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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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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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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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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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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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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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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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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Power input 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 guide ...
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How to connect LED strip to be powered by charger and batteries [closed]
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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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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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 3 kHz 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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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? ...
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evaluating ESD protection for 3.3V i2c
Even though there are questions about ESD protection for i2c bus already in this forum, I wanted to ask how to suppress the clamping voltage of a TVS diode to a safe level. As an example, the ...
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16A Relay controlled with PWM
I am not very experienced with relays but I need to control the state of a relay with a PWM signal such that if the microcontroller is damaged and the controlling pin gets stuck in a high or low state ...
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What is the maximum charge current and discharge current of R5460 Series IC?
I am using "R5460N214AF" IC for 2 cell Li-Ion battery protection. According to datasheet, excess discharge current threshold is 0.2 V and excess charge current threshold is -0.2 V.
I would like to ...
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Transfering configuration to IEDs using IEC 61850
Sorry if this is a dumb question, but since I don't have much experience with IEC 61850 compliant devices, I am having trouble creating the "big picture" of how the whole system is being configured in ...
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Current loop protection from wrong connection of the wires
I have built a current loop protection circuit based on the topic Using a microcontroller ADC to measure a 4-20mA sensor
It works good. The next step is I want to protect the input of the circuit ...
user188731
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Is this resistor necessary for protection?
I would like to incorporate this circuit in my design so that I could use a low current capacity slide switch to control the 2A current of a Li-poly.
Now, I understand the purpose of having two PMOS ...
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Battery protection circuit
I’m trying to design a battery protection circuit for this 300mAh 3.7V LiPo battery.
I’m an EE student which is designing his first pcb. Please forgive questions with obvious answers.
My questions:
...
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Why does this LTC1440 Comparator switch so slowly?
I am trying to build an undervoltage protector for a 6S LIPO battery. My idea was to use a comparator to switch off an NMOSFET when the battery fell below a preset voltage, 20V:
R20, R21 and C20 ...
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What kind of protection do these Ethernet "surge protection" diodes provide?
I was considering a network run outside of my home, and purchased a super-cheap "Ethernet Lightning Protector" because there was little to lose, and I wanted to understand its workings.
Below you can ...
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How do protection circuits deal with instantaneous voltage?
For protection components such as Varistors and Diodes, when an instantaneous fault voltage is applied - how to do these devices protection before the device has time to conduct. For example, a ...
user160063