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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. Examples of faults protected against are: Overvoltage, ESD, overheating, Overloading (too high of a current draw) amongst others.

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±12V protection for MIDI output

TLDR; how to make a MIDI output withstand shorting it to \$\pm12\$V? I'm designing a MIDI output in a eurorack modular synth module on a TRS jack (this is a semi-standard non-standard way to save ...
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39 views

MCP73871 Battery Under Voltage Protection

I want to use MCP73871. Is there a battery under voltage protection in this charger IC? or may I use a battery protection IC? Answer for @Bimpelrekkie I decide to use my power architecture as ...
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Cause of high failure rate in SC189 buck regulator

I have a small board that uses the SC189C buck regulator to take 5 V down to 3.3 V. For whatever reason somewhere between 25% and 50% of these boards have had the voltage regulator fail at some point, ...
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What is the difference between these two protection circuits?

I have seen both protection circuits used in various designs. The first just back to back diodes clamping a line, the other clamping the line to the system voltage rails. Whats the difference between ...
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1answer
35 views

Mosfet Gate-Source Zener

I want to confirm this circuit is going to work and ask how to calculate the zener voltage. The load is going to be driven by 30 volts, and the gate voltage is the same 30v, through an optocoupler.
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42 views

Op Amp input protection

I was looking for an Op Amp input protection circuit and the most common I found looks like this. When the voltage at Input Signal goes above/below Op-Amp's supply ...
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1answer
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Need help finding an under-voltage protection IC for 2-4 cells [closed]

I've been looking for the last few days but I just can't find one. I've found a ton of single cell protection IC's but I can't find one that does the same for up to 4 cells. A stackable single cell IC ...
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39 views

Mains AC overvoltage protection using a TRIAC

I am trying to design a circuit that protects 127V appliances if plugged in a 220V socket (in Brazil 127 and 220V sockets have the same shape and it's easy to plug a 127V appliances in a 220V socket ...
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43 views

Input protection on a DC jack

I am designing an battery powered instrument with around 20-40Ah 3S li-ion batteries in it along with a 10A 3S(12.6v) external charger. Due to ease of availability and the current capacity I have ...
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1answer
38 views

How do I choose appropriate fuse for my circuit?

I am currently using a AC-DC adaptor with specs: AC-I: 100-2040V~50/60Hz 1.6A DC-O: 12V 5A Which is powering up 8 DC motors, 4× 12V 6W 4× 12V (wattage not specified, the motor is meant to be ...
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105 views

How does diode clamp protection work?

I am not able to understand how diode clamp protection works. Considering the diode clamp protection as shown in Figure 1: When the input voltage (Vin) becomes more than power supply voltage (Vss = ...
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Power Consumptions of GFCI Outlets and GFCI Breakers

Due to my applications, I need to know the ballpark power consumption of the internal circuit of a GFCI receptacle and GFCI breaker. Has anyone measured them? Could they reach above 5w or 7w?
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Protecting analog pin from ESD strike

After reading some relevant questions on ESD here, I have come up with the following approach to protect some ADC GPIO pins on my lipo battery operated board that are open to external input, thus ...
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1answer
39 views

Circuit protection component arrangement

I was reading this thread and decided that in general it's better to place the reverse polarity protection diode D2 after the TVS rather than before it, and to instead use a bidirectional TVS for D1 (...
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GFCI contacts with two solenoids

I've finally understood the purpose of the second solenoid in the above GFCI. How it works is when Reset was pressed. The contacts come to the top (attracted by the top solenoid). And in the second ...
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Low Side Mosfet protection circuit

I build a current limiting circuit, which clamps the current to lets say 4A. Id like to add a mosfet protection, which copletelly turns off the power mosfet, if Drain - Source is higher than 6V. In ...
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1answer
68 views

Voltage sampling from 220vac to 5vdc

I made a 1 phase to 3 phase inverter using arduino and IR2104 to control the speed of an induction motor and it is working perfectly. To complete the protection scheme, I need to monitor voltage of ...
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1answer
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Leviton GFCIs constantly trip on shaded pole motors

Update: I consulted with other electrical engineers. Here is a plausible mechanism. Again refer to the circuit diagram of this GFCI: Look at the board layout. There is a long trace from where C3 is ...
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1answer
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Reverse Polarity Protection with parallel P-MOS transistors

There is a well-known reverse polarity protection technique using a P-channel MOSFET like so: simulate this circuit – Schematic created using CircuitLab If I use the common BSS84 for this task,...
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39 views

How to charge Lithium Ion with protection circuitry

I am trying to build a charger for the Ctr 003 battery for the Nintendo DS. This battery has 3 outputs, which I call +, 0, and - for simplicity. When I measure voltage from + to -, or from + to 0, I ...
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IT characteristic implementation of motor protection circuit

I am trying to implement The IT - characteristic feature for motor protection device.There are 2C,5C,10C curve feature . can someone suggest me how it can be implemented in C code. Is there any ...
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3answers
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Fuse 125V/4A can be replaced with 250V/4A?

I want to replace a blowed fuse 125V/4A but it is rare to find them. Can I use instead a 250V/4A ? I read at https://www.mojotone.com/support/Knowledge-Base/Is-it-ok-to-replace-125v-glass-fuses-with-...
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1answer
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help understanding this reverse polarity protection circuit

Going through LT4363 evaluation kit DC2062A-B (schematic here), I came across a reverse protection circuitry that protects downstream components from reverse transients and reverse DC voltage: In ...
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derive Equation between time and current in motor protection device

I am trying to imperilment The IT - characteristic feature for motor protection device.There are 2C,5C,10C curve feature . can someone suggest me how it can be implemented in C code. Is there any ...
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2answers
231 views

Reverse voltage protection for Analog Devices’ family of protection controllers

After going through several datasheets for devices from "Analog Devices’ family of high voltage surge stoppers, overvoltage protection, overcurrent protection, and circuit breaker ICs", I found that ...
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Can water condensation appear on PCB in IP67 enclosure box?

Does IP67 box protect PCB from moisture? If not, is it OK to have an outdoor air humidity sensor soldered on PCB in IP67 housing? Also if it doesn't block moisture, is there any reason to use IP65/...
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1answer
52 views

Reducing the start-up voltage of a low voltage cut-off circuit

I just built this circuit, with the intent to use it as a low-voltage cut-off switch for a single li-ion cell. It works great, but once it's triggered it needs about 7 volts to turn back on, so I ...
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1answer
49 views

TVS diodes for Ethernet/PoE?

I am getting confused in selecting TVS diode for Ethernet Interface. Should I connect one bidirectional TVS diode across a ...
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0answers
39 views

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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34 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
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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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36 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
199 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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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
35 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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134 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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2answers
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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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1answer
54 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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77 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
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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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1answer
110 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
107 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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52 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
57 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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99 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
114 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
118 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
44 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
76 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
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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 ...