Questions tagged [switching]

Switching can be defined as the change in state whether it be an analog, digital, or mechanical device. For digital devices, switching can be defined as a transition from HIGH to LOW or vice versa. For analog devices, switching can be defined as a change of operation within a transistor. Mechanical device examples include physical light switches or button switches. Ultimately, switching interrupts current from going into another conductor path.

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1answer
79 views

Best way to switch electronically between different voltage sources for measurement

I am trying to make a circuit that can measure voltage between three different terminals. The Voltage under measurement can range upto 0 to 1500V. As you can see in the circuit, I want to Measure the ...
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1answer
231 views

High Voltage Switching with Mosfets

I am currently working on a prototype that is going to generate a burst of pulse of high voltages (e.g. 1KV). To do this, I first made a voltage multiplier and feed the mains voltage (230Vrms) ...
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202 views

SPDT mechanical relay: do NO and NC pins short between each other as pole switches

I have a mechanical SPDT relay (Digi-Key PN 281-6348-ND, I am only using one of the two channels). I also have a sensitive circuit downstream of the relay. (Image source) While a mechanical relay is ...
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2answers
205 views

Diode capacitance vs diode speed

I have some difficulties to understand what are the fatest diodes. Schottky diode are known for being the fatest diode (at least according to my knowledge) nevertheless their diode capacitance is ...
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0answers
86 views

How to separate high voltage and low voltage side of a circuit?

I want to design an ATS for a single phase. Here, I have added two sources and also control circuits. But I need to separate the high voltage and low voltage side of the circuit. In order to do that, ...
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177 views

TRIAC driver circuit behavior when switching low current loads

I'm doing a project that involves switching different kinds of loads (edit: by that I mean loads that go from just a couple mA, up to 5A or so) using the usual TRIAC + opto-isolator combo (in my case, ...
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1answer
71 views

Why won't this chip switch?

So I have a problem with The UC382x Family of chips from TI. Here is the datasheet that I'm working off UC382x, I had some confusion already with datasheets seems there's a few floating around but TI ...
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2answers
880 views

Art of Electronics 2.5 - Transistor saturation

With reference to the image below the text says When the switch is closed, the base rises to 0.6 V (base– emitter diode is in forward conduction). The drop across the base resistor is 9.4 V, so the ...
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51 views

Filtering out Switching Noise

I'm designing a custom current limiting circuit designed for electric bikes and small electric vehicles. It's purpose is to limit battery current to "dumb" motor controllers so that you can ...
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37 views

Switching load with changing polarity

From a bespoke board I'm receiving 18vdc that I need to switch. This 18vdc will usually be +18vdc but at times can be -18vdc. The load is .35A. The polarity is being changed via a H-Bridge and ...
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5answers
265 views

Keep circuit on after momentary trigger

I want to keep my circuit on after a push button is pressed and released. Trying to do this I stumbled upon soft latch circuits, but they are too complex and I don't need the turning off feature. What ...
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0answers
55 views

Switching between power sources with microcontroller

I need a way to switch a load(a high power LED) between two different power sources(50v and 100v) using a logic signal, quickly(<500us) and repeatably. I was going to use an n-channel high side ...
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1answer
90 views

Why might an N MOSFET switch output flip with no change in gate voltage (and then stick)?

In lots of places, we use a simple N-FET switch to turn on/off 24V outputs. We use a 30V rated part and stay well under the power/current limits. We've started to see recently however a couple of ...
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749 views

Why is my IRL540 slow to turn off?

I'm trying to switch 12V with an IRL540 from a 5V micro. Right now I have it a 1k resistor between 12V and the drain, the source to ground, and the gate has a 100kHz 5V square wave on it. That's the ...
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1answer
326 views

RCD “Clamp/Snubber”

I am attempting to figure out this "RCD Snubber" as seen below: The Eval Sheet says "The resistor capacitor diode (RCD) snubber for the two synchronous rectifiers consists of R3, C29, and D4 for one ...
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2answers
335 views

Utilization of MOSFETs as switches, design methodology

Let's say I want to use an nMos FET in a low side switching circuit as follows: simulate this circuit – Schematic created using CircuitLab Datasheet for IRF530 here. Now, during my education ...
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0answers
53 views

switching a buck converter with transistor

I've got a bunch of shape memory valves (SMV) that require 1.2V @ 0.25A and I'd like to use a single buck converter and DIO signals from an Arduino to switch these shape memory valves on and off. I'...
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3answers
179 views

Capacitor does not hold charge when switching power

I'm trying to create a power source switch using a relay. This's supposedly will be used for my Raspberry Pi. So what I want to do here is : Create a backup power source with battery that will ...
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2answers
81 views

How can I trigger an AC output ON when an AC input is OFF?

I have a low power 24V AC circuit powering some motorised ball valves for switching water on and off. Several of the valves are 2-wire auto-return meaning that presence of an AC signal will open the ...
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1answer
139 views

Switch 12V loads with MCU and BDW93C darlington or IRF630N

Task is to switch 2 loads with an MCU (3.3V 10mA max) and few IRF630N, BDW93C and sample pack of S901x transistors (of switch relevant components). 12V loads, likely important context for question: ...
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1answer
46 views

Adding Parallel Diodes to a load

This question is based on my previous question - Measuring voltage drop across a diode in a switched circuit I have started a bounty on that question. At the same time, I am trying to understand why ...
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2answers
73 views

How does a “mains priority circuit work”?

Dometic makes a series of DC refrigerators and one capability is to hook the fridge up to both DC and AC and it uses a "mains priority circuit" to prefer the AC source to the DC source, if both are ...
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1answer
248 views

36x LED 5730 in series: diodes burnt when LED driver (based on BP9833A or MT7854BD) powered up

Background: I have 18W, 36 LED lamp fixture which I cannot change. Originally it has 2x parallel 18off 5730 LEDs and 300mA driver. It works for some time, but diodes starts burning. I thought that ...
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10answers
7k views

When does a transistor act as a switch, and when as an amplifier?

I'm a beginner with electronics, anyway I'm experimenting a lot with it. I still don't understand how you can use the same transistor for example to amplify an audio signal, or to act as a switch for ...
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2answers
342 views

Switch Power Supply at 24V using MOSFETs

As title, here's a schematics: simulate this circuit – Schematic created using CircuitLab Is this a correct way to create a power switch or can this schematic be improved? Board will sink at ...
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1answer
314 views

Generator to Main changeover issue RCCB not moving up

RCCB not moving to up position while DG to EB ( generator to mains) changeover. I live in a community where we have almost 1200 apartments in India which will serve power through generators when the ...
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1answer
67 views

Auto disconnect the load while charging the battery

Here is a tentative schematic that would use the battery (3.7V, 3500mAh single 18650 battery) to power the load under normal circumstances. The charger is disconnected at this point. When the AC-DC ...
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1answer
89 views

Best way to switch USB power

I'm looking for a way to switch an USB device's power (a mini waterpump) digitally. I've found some solutions, however I'm not sure what are the advantages/disadvantages of the different approaches, ...
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2answers
186 views

Understanding flyback diodes in an H-Bridge

I am able to understand the use of flyback diodes when a basic low side unidirectional motor switching is done with an N channel MOSFET for example. I also understand the working of H-Bridge ...
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5answers
7k views

In which region should a MOSFET be operated as a switch?

I have a question about MOSFET switching operation. According to an article: In order to operate a MOSFET as a switch, it must be operated in cut-off and linear (or triode) region. According to ...
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2answers
573 views

P-channel MOSFET high side switching, Arduino 5V pin and Vcc connection

In this tutorial, The author makes this weird(to me apparently) connection of 5V pin of arduino to 12 V power supply, and explains itself by: You need to have two power sources - one for the ...
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0answers
40 views

Making aysnchronous sequential circuits hazard free

The problem I am stuck at requires me design a hazard free asynchronous sequential circuit for a given problem description. I have followed the routine steps as follows: I have obtained the primitive ...
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0answers
31 views

How to detect charger connected to cut off battery and use externall power

I'm working on project which is supposed to be user friendly. It will usually run on battery and highest expected current draw is around 6A, but usually around 2A. I will probably use Li-On battery, ...
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0answers
21 views

Manually selecting which of three ethernet output ports should transmit signal from a single ethernet input, using MCU and transistors?

I have a TV-bench containing three different computer units that all use Ethernet. Although, I only have one measly ethernet output coming out of the wall closest to the bench. Not wanting to clutter ...
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1answer
65 views

Negative Half of Sine Wave Passes Through Off MOSFET

I'm trying to design a MOSFET based switch which allows a sinewave through, however I noticed that when I was simulating it in LTSpice, whenever I try to turn off the FET the negative half of the ...
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1answer
137 views

LM2678 PCB Layout question / review

After my initial question about switching regulators I had decided on trying to use an LM2678 for an adjustable/variable voltage form 5-24V and 5A max with an input of ~30VDC. The application will be ...
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2answers
122 views

LTSpice simulation issue

I am studying a circuit which will charge a capacitor till using a voltage doubler till it reaches a specified voltage value. Then it will discharge through a resistor. An SPDT switch is realised for ...
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1answer
48 views

switching 11 250mA shape memory valves from arduino

I am trying to switch 11 shape memory valves (SMV), which are effectively valves that open by heating a (shape memory) wire by passing a current through it. The SMV require 250mA, and have a ...
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0answers
250 views

Can I use an optocoupler to switch an analog signal?

I have this setup to select 1 of 4 signals, pass it through a sensor, then output it to its own output line. It must also maintain all the signals at the output at all times, using optocouplers as ...
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1answer
24 views

Remaining circuit 220Vac

I am newbie, I am looking for a circuit that remaining power for about 5 minutes after switch off the main switch of a 25W fan at 220Vac. Thank you in advance.
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1answer
90 views

Open collector / drain question

I'm trying to to find the best way to force an inverting amplifier to postive saturation with a gate input, but otherwise leave the function of the op-amp intact. I've come up with a few ways to do ...
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1answer
88 views

Why the voltage across MOSFET (VDS) is increasing even when the voltage at the gate (VGS) is constant?

Following is the screenshot schematic for Buck-derived half-bridge isolated DC-DC converter in LTSpice. In the following plot it can be seen that when the lower switch is turned off the voltage ...
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7answers
480 views

What is the spark, caused by opening/closing a circuit, dependent on?

I have a DC circuit that runs 1 A current in it when it is closed. When I close the circuit, i notice that there is a spark between the terminals of connection when they're brought close enough, just ...
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1answer
325 views

Turn On Relay by Phone Line Power

I have two corded phone lines that I want to connect both of them to one telephone device. The phone must be connected to line 1 by default, and it switches to line 2 when it rings. I made a simple ...
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3answers
45 views

Switching between multiple high voltage outputs

I need to verify 15 outputs from a product. All of the outputs are 230V. I want to automate this test so my idea is to connect all outputs to a PCB and then connect a multimeter and an electronic load ...
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4answers
147 views

How to switch 1000w AC load with minimal heat?

I am trying to heat a 1000w heating element with 120VAC. I am currently using a thermocouple and SSR to regulate the temperature, but the SSR is getting too hot at full power even with a heatsink. In ...
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0answers
24 views

Switching between power source

I'm making this speaker where I have 2 12v batteries in series giving 24v an amp. and a PSU giving 24v to the same amp. I wanna make a circuit that switches off the batterie link between each other ...
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2answers
56 views

Manually Change from one Power Source to Another

Apologies, this has surely been answered but not in language I can understand. I have a cooling fan, connected to a Niles AC3 (a voltage triggered power strip), which is connected to the 12V turn on ...
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1answer
283 views

Circuit to switch between direct USB and Bluetooth/battery charging

I am planning to modify a wired keyboard to use a wireless connection, using the HID Relay project (YT, GitHub) as the communication method, along with a LiPo battery, with accompanying charger and ...
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2answers
47 views

Inductor Current Equation

i recently came across an exercise involving solving for the energy released in a freewheeling diode. This is the circuit: The problem is that i'm not understanding the current equations for the ...

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