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.

Filter by
Sorted by
Tagged with
73
votes
8answers
68k views

When is a MOSFET more appropriate as a switch than a BJT?

In my experimentation, I've used only BJTs as switches (for turning on and off things like LEDs and such) for my MCU outputs. I've been repeatedly told, however, that N-channel enhancement-mode ...
19
votes
5answers
2k views

What are some ways to improve a voltage multiplier?

I am working on a Nixie power supply, but I would like to improve it. I have 4x9V batteries in series for a total of 36V to be switched across a multiplier. A (TTL) 555 timer is running astable from ...
18
votes
8answers
4k views

Ribbon Cable Cross Talk - Is there a fix after the fact?

I'm involved in a project where the customer defined pins in a ribbon cable, without considering possible cross-talk issues. The signals are 1 MHz data signals with no ground wire separating them. I'...
17
votes
3answers
3k views

Light bulb burns out — why there is an arc in the switch?

I use light bulbs (common incandescent) in the room and they burn out periodically, ca. one bulb in 4 months burns out. Very often, exactly at the moment when it happens, I see an arc (blueish light ...
16
votes
6answers
3k views

Help me understand this circuit - unexpected LED behaviour

I'm well out of my depth here – please be kind! My kids and I have set up the circuit below and the LED is lighting up unexpectedly. When the switch is off, so is the motor BUT the LED is on. But when ...
15
votes
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 ...
15
votes
2answers
3k views

Why do BLDC motor (1 kW) controllers have so many MOSFETs?

I have a 1 kW three-phase BLDC motor from China, and I was developing the controller myself. At 48 Vdc, the maximum current should be about 25 Amps and a peak current of 50 Amps for short durations. ...
14
votes
3answers
3k views

Is it good practice to run large amounts of current through a MOSFET?

I have been looking for a good way to control the flow of a lot of current in my project. This may at some points be 40-50 amperes at 12-15 V. While relays are a good choice, they are mechanical ...
12
votes
9answers
79k views

Why to disconnect the negative/ground terminal, not positive?

To break off any circuit, the common way is to disconnect the negative and or ground terminal. I rarely see people disconnecting the positive and if so, they're not well educated in electrical ...
10
votes
1answer
381 views

Connect two different sources with two Digital Ouptuts using an Adam 4055

I would like to operate an Adam 4055 module to control two different applications having their own power supply. Adam 4055 is Digital Input/Output control module over RS-485, I use only the DO part ...
9
votes
3answers
10k views

Use BJT transistor as a switch without inverting the signal

I know I can use a transistor as a switch like this: simulate this circuit – Schematic created using CircuitLab Can I use only one transistor that will output the same signal (not inverted)? I ...
8
votes
2answers
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 ...
8
votes
4answers
8k views

How to increase mosfet switching speed, and decrease switching losses?

I hope this is not a too broad question, but what are the best practices to achieve fast switching on a MOSFET driven by a PWM signal? My current knowledge tells me I can do two things: 1 - To use ...
8
votes
1answer
2k views

How does a “speed up capacitor” work in Schmitt trigger?

Hello I'm trying to understand how adding a capacitor across R2 in below circuit increases the switching speed. I don't see how C2 supplies charge to C1. With the additional capacitor C2, it seems ...
7
votes
2answers
7k views

Under what conditions does an optocoupler work fastest?

I want to use the optocoupler FODM452R2 in my design. I want this optocoupler to run as fast as it can (i.e.; work with minimum propagation delay and least rise/fall times). What is the optimum R1, R2 ...
7
votes
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 ...
7
votes
4answers
12k views

Switching between battery and USB using diode OR logic

I have a Raspberry Pi that is powered by a USB cable from a Samsung charger. Now since my college has frequent power cuts, I designed a basic switch to automatically switch between a portable mobile ...
7
votes
3answers
22k views

How fast can a transistor switch?

An NPN transistor can be made a switch by applying some power to the base. Is there a limit to how fast I can switch the transistor on and off, or I can switch it on and off as fast as I can turn the ...
7
votes
2answers
11k views

minority carrier life time? Why is it important for devices' switching speed. Why not majority carriers?

I am trying to get my head around why would a silicon engineer care about the minority life time carrier and how does the minority carrier affect the switching speed of PN junction. Why is it so much ...
7
votes
2answers
3k views

Optocoupler high side vs low side switch

I have a NPN Darlington Optocoupler that I have been using for low side switching. I was wondering if it would be okay to also use as a high side switch? Optocoupler Datasheet simulate this circuit &...
6
votes
5answers
6k views

Is this a sensbile way to switch a 12V line with 3.3V logic

I am just starting to learn about making electronic things, so this may be a foolish question. I think this is adequately different to similar questions here. As a first project I am working on ...
6
votes
2answers
3k views

Why is my power MOSFET heating up when on?

I'm switching a 12V 500mA resistive load (LED strip) with a IRF540 MOSFET and it's getting very hot when it's on and conducting. This confuses me as MOSFETs are ...
6
votes
2answers
883 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 ...
6
votes
2answers
6k views

Why load in NPN transistor switch are located in collector circuit?

I make a simple transistor switch. I read the theory and in many sources I saw that load (with NPN transistor as a switch) are connected to collector circuit, not an emitter circuit (pic.1, for ...
6
votes
3answers
881 views

Soft latching power switch

I have stumbled upon a soft power switch with low part count on EEVBlog, which I found very interesting for my hobbyist projects: https://www.youtube.com/watch?v=Foc9R0dC2iI Since it uses a PMOS and ...
6
votes
2answers
3k views

P CHANNEL MOSFET gate directly GPIO

I'm currently using this circuit to control my load from MCU logic HIGH why just not do like this ? circuit ? It's safe for my MCU ? I use NDP6020P is a Vgs(th) max -1V my VCC is 3.7V. I know in ...
6
votes
1answer
2k views

How to choose the correct TVS diode and how to size it?

So I was thinking about transient suppression and I found TVS diodes. I was wondering how to choose the correct TVS diode since they have 3 voltage parameters: Vc --> clamping voltage, voltage I ...
5
votes
5answers
1k views

Device to power either a red LED or a green LED

I have a green LED and a red LED. I want a sort of switch to turn either the red LED or the green LED on. For example: Where if the switch is off, the red LED is on but if the switch is on, the green ...
5
votes
2answers
532 views

Add a status LED to an existing device

I'm currently converting an old MP3-player (a Creative Zen Stone) to a standalone music player for my children. One of the things I'd like to do is to add an LED which shows whether the device is ...
5
votes
3answers
714 views

CE-compliant Schuko mains power switch: do I need to switch both poles?

I am currently revising a plug-in power meter (i.e. a power meter that you plug into mains, then plug the DUT into it) for CE compliance. It features power switching using a latching relay, only on ...
5
votes
2answers
11k views

Is it possible to turn an audio signal ON/OFF using a solid state relay?

I'm thinking about controlling an audio signal (turning it ON/OFF) using a solid state relay switch? Is that even possible? If not, is there a different or easier way to do this? I'm a noob in the ...
5
votes
2answers
480 views

Switch from one battery to another when one is discharged/disconnected?

I'm trying to figure out how to switch source power from one battery to another when one is dead or disconnected. the circuit needs to be able detect the loss of power on the jettisoned battery and ...
5
votes
1answer
161 views

Output capacitance of MOSFET

I have read in several application notes that there exists a region called the Miller plateau where the current into the Cgd is large such that almost no current enters Cgs holding the Gate voltage ...
5
votes
1answer
906 views

Noise problems in current sensing

I have the following circuit: simulate this circuit – Schematic created using CircuitLab I am using a motor from an electric bike, as a generator and I am rotating it using a drill, to test ...
4
votes
5answers
941 views

Is there any pitfall to using resistors in series AND parallel for an LED array?

I've seen a lot on LEDs and series vs parallel resistor usage, but found nothing regarding the combination of both, so here goes. I am working on a watch of sorts, that will work similar to a 7-...
4
votes
2answers
745 views

Reversed DIP Switch

Simple question, why does the LED lights up when the switch is off
4
votes
5answers
2k views

Pressing a physical button, but digitally using an Arduino in an existing circuit

I have a pair of speakers that by default select their input as bluetooth and I have to press a physical button (every time I power them up) to switch their input to auxiliary. So I'm thinking of a ...
4
votes
2answers
3k views

How can a Switching diode act as a level shifter?

I am following a schematic about a one-way logic 3.3->2.8 level shifting circuit. The hardware in question is a MCU output that drives 3.3V and the input of the UART interface of a SIM800 GSM Module....
4
votes
3answers
675 views

Using mosfets to switch between two thermistors

I've got an Atmel ATmega328P and I'm trying to run two thermistors into one analog pin (TEMP_M5), using a digital pin to select which thermistor is active (TEMP_SEL_M5). I thought the circuit below ...
4
votes
2answers
6k views

How to Use Diode Oring to Switch between Two Power Sources? [duplicate]

I want to switch Power Between a AC/DC adapter which is supplying power to the circuit when AC power is On and when power loss power the circuit using 12V 7Ah Battery. AC/DC adapter is rated 12V 1Ah. ...
4
votes
3answers
5k views

How to switch between two input lines based on a digital pulse

How can I switch between two inputs based on a digital signal. I would like to have the Input 1 connected to the Output for the duration of the pulse and Input 2 connected to Output when the signal ...
4
votes
3answers
1k views

Using a transistor as a switch between RX and TX

I have a microcontroller(arduino) connected via its serial output(RX/TX) to a bluetooth module. i want to be able to program the microcontroller when the two are still connected but unless i ...
4
votes
1answer
316 views

Is it possible to use a NPN BJT as switch, from single power source?

I'm attempting to build the following circuit to better understand how to use a NPN BJT as a switch. What I've Tried I'm calculating the current across the LED (in order to light it up) as: ...
4
votes
1answer
263 views

DC/DC Switching Converters: Is it possible to run a current-mode converter in voltage-mode only?

DC/DC Switching Converters: Is it possible to run a current-mode converter in voltage-mode only? If so, is there an example using a buck converter? In particular, I'd like to use UC3843 (LT1243) in ...
4
votes
2answers
432 views

Does a transistor/FET dissipate more power with a freewheel diode?

My question is: Does the transistor dissipate more power because of the freewheel diode? Ifso, why? simulate this circuit – Schematic created using CircuitLab
4
votes
2answers
13k views

What's the difference between virtual circuit switching and circuit switching? [closed]

Circuit switching's packets take the same route as virtual circuit switching's do. So, how do I distinguish between virtual circuit switching and circuit switching?
4
votes
2answers
186 views

How does this signal chopping circuit work?

There is a project online that was posted a few years ago that I want to explore. Unfortunately the progress was never updated so I will have to design it myself from the information that was given. ...
4
votes
3answers
3k views

Switching transistor off when current is supplied to it's base

Is it possible to switch off a LED when current is applied to base of a transistor? I am using the circuit below but when current is applied to the base, the LED is ON. I need the LED to be off when ...
4
votes
2answers
143 views

Circuit for choosing one power supply from several of them

I have a load and four different voltage sources. I want to change the voltage on the load by using four different enable signal as seen in the schematic below. Note that, all of the "Enable" signals ...
4
votes
3answers
333 views

UVLO for Energy Harvester circuit

A good background on the problem can be found in the document: (Under Voltage Lock-Out Design Rules for Proper Start-Up of Energy Autonomous Systems Powered by Supercapacitors). The above document ...

1
2 3 4 5
16