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Questions tagged [circuit-protection]

A device, components, or safety measure designed to protect circuits from overvoltage, overcurrent, a combination of these; or the theory of same.

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52 views

How to protect against line transients?

I am designing a circuit that can detect if a cable is connected to mains voltage (e.g. via an external relay or switch). The device will be installed in electric cabinets. The circuit is tested and ...
3
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1answer
426 views

Dimensioning SCR crowbar circuit

I need to dimension an SCR crowbar circuit to reach a certain level of protection against overvoltage, without increasing much the complexity of the circuit of my control card. The need is to protect ...
3
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1answer
289 views

Opto-coupled EIA-422 receiver (understanding suggested circuits)

I am looking at a standard for communication of marine electronics (NMEA). The standard is electrically essentially EIA-422 but it prescribes opto-coupled differential receiver pins without connection ...
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2answers
36 views

Both fuse and circuit breaker operated

Is there a reason that both a fuse and a circuit breaker would operate? From my understanding, the fuse should blow first and kill any current flowing through it leaving the breaker intact. So why ...
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3answers
34 views

Voltage isolation at IC pin when Vcc=0V

I recently started a project that utilizes a piezo sensor to sense vibrations. The piezo signal is fed to a uC in order to detect vibrations above a certain threshold. However, the piezo's high ...
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2answers
71 views

Protection Against High/Negative Voltage for Arduino

I am currently on a student project where I have to create a portable device that allows the output of sensors connected to it to be displayed on a 16x2 LCD screen using an Arduino Uno R3. One of ...
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1answer
105 views

Whats the cheapest protection circuit for this test equipment?

I am designing a piece of test equipment that has a DAC output. The test equipment might be used to troubleshoot UUTs that are damaged or malfunctioning. Therefore I want to add a protection circuit ...
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2answers
60 views

Powering 5 fans with a LTC 3780 : should I protect it against induction effect?

I want to power 5 fans in parallel (12V 0.80A, each) using a adjustable power supply (DIY, made with an LTC 3780 connected to a 24V 15A PSU and mini Voltmetre). I read that a fan could destroy the ...
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2answers
984 views

Overcurrent / short circuit protection for back to back mosfet ac switch

I'm trying to come up with a way to do overcurrent protection for the following circuit: My first thought here was to monitor the increase in voltage drop over one of the mosfets (M1) and via a zener ...
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0answers
57 views

How the oscilloscope input voltage rating is independent from attenuator setting

Since I'm taking part in a quite interesting educational project that incorporates the design and testing of the analog front-end of a relatively high speed ADC (up to 200 MSps) I've been studying the ...
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1answer
104 views

In a DC circuit, are there any reasons for wiring overcurrent protection such as fuse or pptc PHYSICALLY near the load?

In a DC circuit, are there any reasons for wiring overcurrent protection such as fuse, pptc, etc.... PHYSICALLY near the load(or inside it)? By wiring "physically near", I mean in the power wire going ...
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26 views

Seperate protection circuit for charger and system for Li-ion battery

I'm thinking of using the BQ2971x for battery protection. http://www.ti.com/lit/ds/symlink/bq2971.pdf One thing that anoys me is that most batterys (18650 Li-ions) usually have a lot higher ...
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1answer
45 views

PTC thermister value

I am trying to find out specifications of a thermister on which "10P" is printed. Its resistance at room temp. is 18 Ohms when the circuit is power off. How can I find out its specifications? This is ...
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0answers
61 views

Dual diode connection for return path

I want to use the following dual diode for the return path with a fuse. The diode is dual with each diode rated 25A, the cathode is the same, which means I have to connect it like in the figure? Do I ...
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4answers
1k views

What is the best practice for 2 inputs triggering one device

I am loving this site with so much knowledge. I have a slightly different request and from the notes, i have seen i am still a little confused. My project is I have a 24V source that when switched ...
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1answer
46 views

Recommendation for series protection resistors on CAN bus?

When implementing an RS-485 interface, I tend to follow TI's recommendation in the SN65HVD75 datasheet to include \$10 \Omega\$ series resistors on the A and B lines. The TVS diodes I'm using clamp ...
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2answers
133 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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1answer
94 views

cheap charge management + protection circuit or fuel gauge + protection circuit

I would like to know if it is possible to have in the same package a fuel gauge ic + a protection circuit for lipo battery, or a charge management + protection circuit, in the same package. I have a ...
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4answers
3k views

Interfacing a button to a microcontroller (and PC) with a 50 m long cable

I am designing a board that will be plugged into a computer and will read the status of a button ~50 m away in an office environment (it's actually a lot closer, but the cable is long). I think ...
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2answers
68 views

Understanding STEVAL-ILM001V1 DALI transceiver schematic + adding protections

I'm working on implementing a DALI bus interface circuit. DALI has a few specifics that make this tricky: The device should draw at most 2mA when receiving, it transmits by shorting the bus (250mA is ...
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1answer
138 views

Circuit Board Design…Getting Rid Of A Relay and Adding a Choke and Capacitor Filter?

simulate this circuit – Schematic created using CircuitLab Figure 1. Original Schematic Is there any way to get rid of the relay in this circuit? And would it be wise to add in a power ...
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1answer
100 views

I need help to design a circuit to suppress amp peaks

First: im new here and this is my first question so if you think that I should ask or behave in a different way, feel free to tell me. The (My) Problem: We run LEDs on a test stand with ~5V,2.3A and ...
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2answers
9k views

How can I use two TP4056 with two li-ion batteries, but single load?

I have two TP4056 modules (with protection circuit), which I am using to charge two batteries respectively, off a single power line. The modules are the ones that have charge output (B+/B-), and ...
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0answers
76 views

Impedance of Bus Bar vs Wire

My question was simply. If a meter of wire has impedance of 1 uH. What is the impedance of a meter of bus bar? yesterday: To make it simpler. The longer the leads of SPDs (Surge Protector Device) ...
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0answers
61 views

Protection against ESD/EFT/Surges

One of my project architectures looks like this: GPIO / 595 output / 12 VDC wire lengths will not exceed 25 cm. I have faced MCU lockup issues due to EFT in the past and want to make sure this ...
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0answers
20 views

Lion Battery Shutdown Mode and Wake on Charge

I'm currently designing a BMS that doesn't rely on a TI bq-series IC for gas gauging, protections, etc. So far, I have analog circuitry handling over and under-voltage cutoff, overcurrent cutoff, ...
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2answers
56 views

±12V protection for MIDI input

TLDR; how to make a MIDI input withstand shorting to \$\pm12V\$? This is a counterpart to this question, I'm asking this as I was inspired by the great answer I got there. I'm designing a MIDI input ...
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2answers
124 views

±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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1answer
75 views

Use of internal PCB ground plane as ESD baseplate/EMC reference plane of product in plastic enclosure

I am designing an electronic product which will be housed in a plastic (non-conductive) enclosure. There are a number of, mostly shielded, I/O cables (Copper 10/100/1000Mb/s Ethernet, USB 2.0, RS232, ...
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1answer
64 views

How can I simplify my design for a Surge Protection Device (SPD)?

I have found a basic design for a SPD and I would like to simplify it. However, I have little experience designing SPD circuits. This is my parallel type SPD circuit with embeded LED indicator: In ...
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2answers
56 views

Selection of External Current Transformer

simulate this circuit – Schematic created using CircuitLab I am designing a product for motor protection circuit. where I want to use customized external CT for application which gives me ...
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2answers
134 views

RS485 line protection diodes

Can anyone confirm the correctness of D27, D28 diode polarities or should they be in opposite direction? Please suggest an which diode is suitable for this purpose OR is it better to use a zener diode ...
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1answer
203 views

Calculating energy of transient/surge handled by metal oxide varistors (MOV) or surge suppressors?

As I get to know more about the MOV operation, there are more things needed to understand. My MOV (V420La20AP) has Varistor voltage of 680 Vrms (10%) at 1 mA, and maximum clamping voltage of 1120 V ...
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1answer
138 views

oscillation in overcurrent shutdown circuit

I've tried to design an overcurrent shutdown circuit, what turned out to be more complicated than I thought. The specifications: PSU from 5V to 40V Shut down at currents >= 1A At most a Watt or so ...
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2answers
127 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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0answers
45 views

DMX protection circuit (diode clipper)

TL;DR I’m building a board that bridges the common types of DMX connector (various forms of XLR, RJ45, tails and product-specific terminals). There is a possibility that someone could accidentally ...
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2answers
72 views

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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0answers
36 views

US/Can - Maximum current in a single circuit in a 100A panel

I hope this is the right sub... I have a 100A pony-panel in the garage. I'd like to have someone add a wall plug for EV charging, ideally a 14-50, but I'd settle for a 14-30 if need be. I seem to ...
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2answers
132 views

shorting behavior of isolation transformer

I have a very expensive 500va 1:1 toroid transformer with to isolate workbench from ground. But I'm afraid to use it for fear the winding may burn up when something shorted. I'd like to know what is ...
2
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1answer
49 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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1answer
118 views

Rs-485 isolation

Hi, I have RS485 communication circuit as shown in figure. But it has no isolation, only SM712 is used for ESD protection. Now, i think it will be better to isolate the it.So, how can i isolate it? ...
3
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3answers
680 views

Does an overvoltage TVS for USB hot-plugging connect to shield ground?

I am designing a keyboard which will connect to the computer via usb-miniB to charge a LiPo battery. The datasheet for the charging IC I am using specifies overvoltage protection on the USB power ...
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3answers
886 views

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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0answers
56 views

chances of A4988 motor driver creating back current through the STEP and DIR pins

I am trying to drive 2 stepper motors using A4988 motordrivers and I am using the following circuit diagram as shown in the image Only change from the above circuit diagram is that I have not ...
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2answers
10k views

Determine if two outlets are on the same circuit without breaker access [closed]

I live in an apartment and do not have access to the circuit breaker panel. In the summer I run two AC units, and have inadvertently tripped the breaker before while running my vacuum cleaner. This ...
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1answer
56 views

TPS26601 Industrial eFUSE Circuit Design

I have been designing a circuit for various Power protections like overcurrent, overvoltage, ...
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2answers
281 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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1answer
61 views

Can a ground fault be caused by something outside the home?

Yesterday afternoon, I had a GFCI switch trip. It would not reset. I figured I had a ground fault. I left the home for a few hours and after I returned I was able to successfully reset the GFCI. The ...
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1answer
37 views

Opto-coupler to convert current into voltage

I am using TPS26601 for my next design. There is a pin IMON which outputs current proportional to current flowing throwing the output pin. The gain ranges from 72 ...
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2answers
545 views

LM78xx Reverse Polarity and Reverse Bias

I'm building a circuit that will use a LM7805 and LM7812 to produce 5VDC and 12VDC respectively, with the input power being ~16VDC from an external wall wart. I already fried one of each regulator ...