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Questions tagged [switches]

Devices to interrupt or route a signal or power one of several ways.

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3answers
2k views

What the purpose of a diode in parallel with a power switch

I've come across a circuit that has a diode in parallel with a power switch that's controlling a BLDC motor circuit. I was told that it's a flyback diode to prevent voltage spikes from an inductive ...
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1answer
52 views

Looking for a three state relay or switch

I need to control the link between three wires: Nothing touches == State 1 == Light is off Red touches brown == State 2 == Light is on Red touches grey == State 3 == Light blinks A little drawing: ...
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2answers
38 views

Transistor for USB Hub power control

I'm trying to add power control to a USB hub based on the Terminus Tech FE1.1s hub chip. From the datasheet, I know the chip supports ganged power control, so all ports share a single switch. That's ...
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2answers
181 views

How to turn a coffee machine on/off with a microcontroller? [on hold]

So the thing is, I'm a computer science major and working on an IoT project which is a coffee machine powered by a Particle Photon and controlled with an Amazon Alexa skill. The problem is I have ...
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2answers
161 views

Where are all the multiplexers?

I am trying to implement a circuit where 2 SPI drives (basically two masters) speak to 1 slave. Both operate on a 3 wire SPI. Keeping that in mind I was going to have the CLK and MOSI of both as ...
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1answer
666 views

Op Amp as a simple switch

I want to build a little voltage switch that switches on a buzzer and a relay when a certain voltage is reached. Please have a look at the schematic. I use a trim potentiometer to set up the switch ...
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3answers
527 views

Alternating between two LEDS using BJTs and SPST Switch

I made a circuit based on this post, Alternating between two LEDS using BJTs. It seems to work in the simulation just fine but when I'm connecting it with real components, I get funny behavior. Here'...
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1answer
49 views

Reset Switch Wiring on STM32

I want to wire a reset switch for my STM32F0 microcontroller. The datasheet suggests the following external circuity to do so: Connected to the NRST pin is a 0.1uF capacitor and the reset switch. A ...
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4answers
109 views

How can I control 2 lights with a SPDT switch?

Note: After some careful thought, I've opted to rather just abandon this question, see the chosen answer for more info. I current have a 220V AC lamp with two light bulbs wired with a single on-off ...
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0answers
5 views

How to replace a manual timer by a simple on/off switch on a home appliance [migrated]

Case On a simple 220v home appliance equiped qith a maual timer switch ( a knock that you can turn clockwise up to the desired position -time- and will then automatically turn counterclockwise for ...
2
votes
1answer
330 views

Digital equivalent of a double-throw switch?

I'm designing a circuit that would switch between stereo-jack inputs. Source audio would be plugged into one end, and on the other two ends, two different audio outputs. I want to be able to switch ...
0
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0answers
42 views

High current and voltage DPDT switch

I have two different voltage sources that can supply a LR load. I need a mechanical DPDT switch that can be used to choose the voltage source. When used properly the switching between sources would ...
2
votes
2answers
94 views

Best way of switching between different resistor/capacitor values in a layout?

In my project I would like to switch between different resistors/capacitors on the fly, preferably without having to open the containing box around the PCB. Therefore, one idea was to use a jumper (...
0
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1answer
64 views

Use one 12V 30A timer for two separate 12V inputs?

I'd like to use the following timer, rated 12V 30A, but for switching two different 12V inputs at the same time and not having to buy and program two timers. But the timer only have one channel. One ...
0
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1answer
124 views

NPN common emitter transistor as a switch switches off as the current draw in collector falls

I am trying to switch power to a Pi Zero using an NPN transistor (2N2222) as a switch, as in the following diagram. simulate this circuit – Schematic created using CircuitLab The Ib is around ...
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0answers
47 views

Alternatives to common collector transistor switch?

I am trying to connect a Raspberry Pi / Arduino to a coffee machine. The coffee machine has a simple function, with a single button (momentary switch, on a DC cicuit) to dispense a coffee. I'm trying ...
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0answers
29 views

Switching between two power sources (LiPo cells) [duplicate]

I'm building a circuit with a 2S or 3S LiPo as power supply. If a 2S LiPo is connected the circuit should be powered with 2S (7,2V). If a 3S LiPo is connected the circuit should be powered with the ...
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2answers
150 views

Proximity Sensor Switch Circuit

My goal is to build a proximity sensor switch circuit that can turn an LED on OR off. If I wave my hand, the light will turn on. Similarly, the light will turn off if I wave my hand the second time. I ...
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2answers
45 views

Switch current rating label: 0.1GPA

I feel like this ought to be a FAQ, but because of the abundance of articles on Grade Point Average coming out of the US, it's extremely difficult to search for. I have a micro switch with rather ...
0
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1answer
145 views

Find the transfer function of the circuit if current I is the measured output

So there's this problem I am trying to solve: Consider a series RL circuit corrected to a DC voltage source and an on-off switch. Assume R = 2 ohms, and L = 1H, and applied voltage V = 10 volts. ...
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1answer
136 views

Bypassing refrigerator door alarm piezoelectric buzzer

My appliances keep beeping at me. How can I deactivate or bypass this refrigerator door alarm buzzer without affecting the rest of the circuit? I thought I could just cut/connect the wires at the ...
0
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1answer
229 views

How to analyze RL circuit with sequential switching?

I am trying to solve this question: However, I am having difficulties solving as I only have come across circuits which are initially closed then opened, not vice versa as is the case here. ...
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1answer
151 views

Finding total energy for RC discharged capacitor at t = ∞?

Most Rc circuits are not as severely difficult as this kind of circuit. I'm trying to solve for both the time constant and the voltage V2 across the R2 resistor, both of which will hold the necessary ...
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1answer
176 views

Latching power circuit with short-to-ground switch

I'm trying to build a circuit around an existing switch that allows another component to override the switch state. (Our component is a computer and the feature we're trying to build is remote-...
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0answers
33 views

How to make a solid state SPDT switch?

I'd like to make an analog SPDT switch along the same lines as FSA2259UMX or similar chips, but out of simple discrete components. This is partly for learning, and partly because I'm redesigning a ...
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1answer
33 views

NMOS Switch, Drain Source Location

I just have a bit of confusion about which way to orient MOSFETs in IC switches for sample and hold circuits Which one is it? Or does it not matter?, since the Source and Drain potentials will be ...
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3answers
2k views

Bjt base current calculation

In a bjt transistor that is used as a switch (maximum saturation, Vce minimum as possible), what is the minimum base current that is required for a corresponding desirable collector current?
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1answer
31 views

Help reading DP4T slide switch schematic

I am having trouble reading the schematic for the C&K L204011MS02Q DP4T slide switch (datasheet here). In particular, I am trying to identify the "common" pins so that I can wire this switch up ...
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1answer
56 views

Replacing switch without transistors

I have a little keyfob style remote that I want to mod. It runs on a 3 volt button cell. I want to control the three switches with an ESP8266. The switches are connected to ground, and directly to a ...
2
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1answer
57 views

Safety switch “breaking capacity” vs. voltage

In the context of safety switch rating (fuses, circuit breakers, etc.), the concept of breaking capacity refers to the maximum electric current which can be safely interrupted by a tripping safety ...
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4answers
2k views

Is there a more efficient alternative to pull down resistors?

I am building a LED spinner circuit and I am at the point of optimizing it. The whole circuit itself only draws about 10-20mA max. I was today looking at this part of the circuit: Now as you can see, ...
0
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1answer
41 views

Need help for using N-Mosfets to switch on either one battery or the other

I'd like to add a second battery (36V Li-ion) to an ebike to increase its range. My goal is to use one battery at a time, not using both in parallel with e.g. ideal diodes or something. I'd like to ...
0
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1answer
193 views

Simulink “ideal switch” block changes output unexpectedly

I am attempting to simulate a DC motor circuit on Simulink. I have built the block diagram mainly according to a tutorial, and am confused about an aspect of it. The main circuit has a DC power source ...
0
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1answer
80 views

Can I turn on an LED, only if the switch has been closed for a desired amount of time?

I'm trying to use a ball switch and an Arduino to turn on an LED. I only want the LED to turn on if the ball switch is closed for 20 seconds. Does anyone know how to do this? Thanks.
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2answers
297 views

Options to read an 8x8 switch matrix?

I have a project (pinball machine) that will have a decent number of microswitches that will be connected in an 8x8 switch matrix. I'm trying to determine what my options are for reading this matrix ...
3
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2answers
2k views

Why do switches have a current and voltage limit?

I want to attach a switch to a 5 Volt battery pack to be able to turn it on and off. The batteries will power 4 DC motors. The current draw will be about 1 Amp. The switch I have is like the one here. ...
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1answer
31 views

Wiring 4+ 12v led ring switches from one 12v supply

I am new to electronics and general electronic circuits. I have 4+ led ring switches (from here: follow link) The website says that the rating of the switch contacts is 5A 250VAC with an ...
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2answers
30 views

How to use reed switch to change operating modes?

I have a circuit of LEDs - say L1-L10. My requirements: No visible switch Illuminate the LEDs successively (only ever one at a time) every time the user passes a magnetic "wand" over the switch. (...
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2answers
38 views

How to bypass on/off momentary switch? [on hold]

I have a Bluetooth receiver and was wondering if there was a way to have it turn on when power is plugged in without having to press the on switch? the middle button is the on/off switch.
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0answers
81 views

Easiest way to short 50 pairs of wires together

I have a serial keyboard that has 24 pins and works via one of the top 11 pins shorting to one of the bottom 13 pins when you press a button (top and bottom membranes touch) and this is picked up by ...
0
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3answers
205 views

RC / Airsoft Battery Switch [On-Off-On]

Morning all, I am toying with the idea of wiring up a small On-Off-On rocker switch which will control which battery will be active in my Airsoft setup. Below is a brief diagram of how I expect this ...
0
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1answer
51 views

Alternatives to a sliding switch and relay?

There is a sliding switch on my board to select two different cases. A key like this: From sparkfun.com You know its equivalent schamtic is as below: From sparkfun.com I am designing ...
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1answer
123 views

CD4011BPWR Button Press Logic NAND IC

During testing on my pcb I am running into a couple of problems the first issue is with either my momentary switch or my MOSFET Q4 – PMV30XPEA. For my switch design, I have implemented Fig. 5 on ...
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0answers
48 views

PMOS Load Switch Circuit issue

I'm working on a load switch circuit that drives a capacitive load of 1000 uF and a GaN transistor in parallel. The schematic of the circuit is attached. The input voltage is 50 V and the ...
3
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2answers
262 views

electronic switch, understanding on-resistance measurements

I'm trying to understand from the datasheet, how much on-resistance I will get from this electronic switch: DG411 datasheet: https://datasheets.maximintegrated.com/en/ds/DG411-DG413.pdf given this ...
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0answers
35 views

Automotive High Side Switch vs. E-Fuse

I've been looking for a solution to provide solid-state overcurrent protection for automotive loads such as small water pumps (0.6A continuous), fans (3.5A continuous) and fuel pump (8A continuous). ...
0
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1answer
203 views

Hamlin Reed Relays for Audio: Sink or Source?

I'm building a small stripboard audio switchbox using some hamlin 5v reed relays (HE3621A0550, mouser link here). A small SPST momentary switch activates the relay. Wondering if the best practice is ...
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0answers
8 views

Garage door hard-wired wall button doesn't work after adding wireless controller dongle in parallel [migrated]

I have a standard garage door controller (Chamberlain HD900D) with a wired button inside the garage, and wireless clickers that all work properly. I purchased a GoControl/Linear GD00Z-4 ZWave Garage ...
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0answers
18 views

Legrand switch invert light [migrated]

Here are two photos of the switch I need help. So basically I want to change the left light to the right one and the right to the left but I don't understand the brown cables. Which ones do I need to ...
1
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1answer
44 views

What sensitivity of reed switch should I use?

For my GCSE Engineering project, I am building a device which attaches to the frame of a bike, and uses a magnet (Attached to the wheel) to detect 1 turn of the wheel (I have also compensated for ...