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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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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
70 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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2answers
56 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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1answer
104 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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56 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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0answers
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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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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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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1answer
45 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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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
64 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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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
71 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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2answers
126 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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2answers
55 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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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
126 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
71 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
131 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 ...
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1answer
47 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
112 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? ...
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3answers
876 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
54 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
130 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
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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2answers
271 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
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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1answer
55 views

TPS26601 Industrial eFUSE Circuit Design

I have been designing a circuit for various Power protections like overcurrent, overvoltage, ...
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1answer
50 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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3answers
78 views

Single Cell Battery Protection ICs

I'm designing a product that will be powered by a single 18650 cell. Specifically, I am basing my numbers off this cell in particular: Samsung INR18650-25R It has a typical full voltage of 4.2V ...
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1answer
60 views

high power - overvoltage protection

I am designing a circuit to protect a load from over-voltage. The voltage at the load must be around 380VDC and the current consumption will be around 2A. In normal operation the Power Supply must ...
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3answers
476 views

Best way to protect a MOSFET from overcurrent

I'm trying to build the circuit in picture above. unfortunately the load on high side of the step up transformer is unpredictable and the input impedance of transformer is very low so I'm guessing the ...
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2answers
45 views

Battery powered circuit protection

I’m just curious what kind of protection you would typically expect to see on a battery powered circuit. Circuit in question is a simple 24v dc relay controlled motor. Main power source would be 2x ...
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1answer
50 views

Reverse polarity protection for symmetrical input

I have a symmetrical voltage input I need to protect agains reverse polarity, and over-voltage. Here is the reverse polarity protection I designed. Is it correct ? I can't find much information about ...
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1answer
76 views

How these two diodes used in the ciruit protect from the voltage spikes?

I'm playing around with a simple DIY project, and after about three days of googling and reading stuff I still can't wrap my brain around two Schottkys below: From the project page: The two ...
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0answers
47 views

Testing eurorack input protection

I'm building a eurorack synth module, and I'm about to do the final tests on the design to make sure that the module cannot be destroyed (electronically, using what's available in the rack, so ...
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2answers
130 views

ESD diode selection based on VCC of the IC

I have a question about TVS diode selection. This kind of question is already discussed in previous questions. ESD Diode - GPIO Microcontroller Selecting a TVS for ESD protection For protecting vcc ...
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1answer
103 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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1answer
92 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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7answers
2k views

Opinions on what I've come up with for a 12 V-to-5 V automotive circuit?

Is this a solid solution for an automotive 12 V-to-5 V circuit to power an ATtiny? I've been trying to come up with a solution for my needs that can handle the automotive environment that is so scary ...
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3answers
117 views

How long do I have before my sensitive components get fried?

I'm using this IC (https://www2.mouser.com/datasheet/2/609/ADM1270-878589.pdf) to control the current and the voltage on some of the outputs of a PCB that controls the power to other PCBs, which have ...