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Questions tagged [switches]

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

19
votes
3answers
9k views

How can I design a circuit that will turn on when a wire is cut?

I'm trying to build my own cable lock alarm (for science!) and am having trouble figuring out a way to detect that a wire has been cut. The circuit has to Use no power at idle (or at least, very ...
4
votes
4answers
6k views

Current over ethernet?

It seems that the voltage over ethernet ranges from 2 to 3 volts. How much current typically runs through the wires? I tried Googling with no success. I ask this because I'm looking for components ...
10
votes
2answers
1k views

What's the difference between small signal bipolar junction transistors (BJTs) marketed as switches vs. amplifiers?

For instance, the MMBT3904 and MMBT3906 BJTs are listed as NPN/PNP Switching Transistors, and the datasheets mention the switching times, while the BC846 and BC856 BJTs are listed as NPN/PNP general ...
34
votes
2answers
3k views

What's the difference between field-effect transistors (FETs) marketed as switches vs. amplifiers?

For instance, the J108 JFET is listed as "N-Channel Switch", and the datasheet mentions the RDS on resistance, while the J201 JFET is listed as "N-Channel General Purpose Amplifier" (and the on-...
-1
votes
1answer
700 views

switching DAC output to multiple inputs

I am currently using a DAC (mcp4922) and want to send the output voltage (0 to 5V) to 1 of many (14) inputs on an Arduino Mega. I am currently using some VN2222 fets for switching (because I had them ...
6
votes
3answers
2k views

pushbutton switch that twists to lock

I'm sure I've seen something like this before, but I can't find it now, or even find any appropriate names to call it to search for it. I'm looking for a small momentary pushbutton switch similar to ...
1
vote
1answer
1k views

Diagram validatation for two motors connected with On-Off-On Switch

I want to connect two motors on an On-Off-On switch. On position 1, I want motor 1 to me active, on position 2, I want motor 1 and 2 active. Here is the diagram I was thinking of implementing My ...
2
votes
2answers
307 views

Do Fixed Bias BJT 's have a cut in voltage?

I am doing a DC analysis of a Fixed bias BJT and am trying to calculate its collector current. So far I have these following values. I am using a MMUN2211LT1 bias resistor transistor network. My ...
5
votes
3answers
3k views

How is oil-filled switchgear possible?

I can't find any definitive description of how oil-filled switchgear uses the oil and manages to keep it from ignition and boiling. For example, the Wikipedia article says Oil circuit breakers rely ...
4
votes
1answer
440 views

How can I use a transistor as a switch?

I'm trying to drive a DC motor using an external voltage source and control it using a transistor switch. It doesn't seem to be working during the simulation though. I know I must be doing something ...
3
votes
2answers
2k views

Using a MOSFET as a switch

I would like to use the smallest component to control the power of a component (nano motor). I have seen on the web two main possibilities: DC converter : LTC3127 for example, I change the value of ...
2
votes
2answers
12k views

What does these switch rating mean?

Current rating: 3A @ 125 VAC, 1A @ 250 VAC What can I read to understand this ratings better? What exactly does it mean? They're used to rate this Momentary N.O. Raised Push Button Switch.
3
votes
3answers
2k views

How can I convert a 2 prong connector to USB?

I'd like to convert this: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=060-640&utm_source=googleps to a USB? An ideal solution for me because of cost would be to use an existing usb ...
13
votes
4answers
7k views

How to switch power of microcontroller by button?

I have a microcontroller device with battery power. Currently I toggle power by simple on/off switch. I want to toggle power by one pushbutton with minimal modification of the schematic (and ...
2
votes
2answers
5k views

How to drive a transistor with an active low output from a switch?

I have a set (3) of switches (bell pushes) that are a considerable number of years old. They are connected up to a four core cable, one for each switch and one common. The common side of the switches ...
4
votes
1answer
944 views

How do I switch small AC signal on/off electrically?

Suppose I have an audio signal source. I want to connect and disconnect it to amplifier electrically (for example controlled by another source, like microcontroller, sensor, 555, etc). I don't want ...
5
votes
2answers
449 views

Switching a Large Current with a Tiny Switch

I have a SPDT switch that can switch .3A @ 5V. I would like to use it to switch 1A @ 9V which will then be fed into a 7805 linear regulator. This is the design that I have come up with. I have run ...
3
votes
1answer
419 views

RC PWM video switch

I'm currently working on a quadcopter that I'm equipping with several video cameras of various sizes/quality (i.e. one high quality, forward facing camera, then three or four cheap micro cameras ...
5
votes
2answers
2k views

Smallest water detector / switch

I am looking for a small simple switch. But it has certain restrictions because I want to use it for salt water aquarium and copper exposure is lethal to some fauna, as well as some plastics. Looking ...
1
vote
1answer
2k views

Difference between Switch-Disconnector and Disconnecting Switch?

I'm an electrical engineering student doing an intership at the moment and I was hoping that some of you might be able to help me out with some things I'm having trouble with: Is a switch- ...
1
vote
1answer
654 views

How to make on/off switch for popcorn maker?

I have a popcorn maker that when you plug it in it just starts working. Theres no on/off switch and it's kind of annoying. When you unplug it you always get a big blue spark which seems kind of ...
8
votes
7answers
17k views

How can I turn on and off a switch every 20 minutes?

I want to make the above switch which will stay on for 20 minutes and then off for 20 minutes. This should be continuous. Actually, I want to place this switch for my air conditioner which I do not ...
5
votes
2answers
30k views

Add on/off indicator LED to circuit

I'm working on my first small electronics project; building a small LM317 based power supply. I've built the circuit as shown in the data sheet (black part of the circuit diagram below) on a perfboard....
2
votes
2answers
324 views

How does a large electric switch different from small?

Why do some electric appliances require to have a large electric switch to turn them on or off? If I use a small switch where a large switch is required, would there be potential possibility of ...
4
votes
2answers
3k views

Digital Switching for Audio

I want to be able to digitally switch the input of a line-level preamplifier. I was considering using relays to physically connect or disconnect each source to the input of the amp, which would be ...
1
vote
1answer
457 views

How can I matrix switch multiple lines, including power?

I have devices with several similar boards, all of which are basic computers (with CPU, RAM and ROMs etc.). They all interface to the I/O unit via a standard connector, although the connectors aren't ...
6
votes
3answers
3k views

Implement MicroController Power Switch and re-use the button for other features

This is similar to other questions, but I feel it is different because of the reuse of the "power" button. I want a "latching" Momentary Power button. Behavior: User Pushes momentary button, holds ...
2
votes
2answers
12k views

Common vs Ground in DC Circuit

I am trying to wire up a DSP controller. It has 2 limit switches, and the instructions say to connect the "COM" on both switches together and the "NO" to y- and x-. There is an indicator light on the ...
0
votes
3answers
796 views

Switch at output of operational amplifier

I'm currently designing an active filter which has to pass an analog signal between two cables (PLC). I'd however like to not let it pass in case the signal is already present (up to a certain ...
11
votes
3answers
162k views

Can you clarify what an 1NO1NC switch is?

I've come across multiple mentions of switches described as 1NO1NC. They often described as having 2 options: ON/(OFF) and (ON)/OFF and from what I gather they have 3 terminals for wires: a NO ...
3
votes
1answer
338 views

What is the name for this rotary switch scheme?

I am trying to figure out just exactly how this rotary switch works and what it's called (so that I can research it). There are usually 6-8 pads which are shorted to a common pad through fingers. That'...
1
vote
1answer
2k views

Arduino to act as a switch for a remote

I have a wireless remote control for a light. It runs with a 12V battery. It has two mini Omron type B3F momentary ON switches (mini push-button switches). One button is for Light ON, the other for ...
4
votes
3answers
14k views

Using a momentary push button as a latching on-off toggle switch

Please check the schematic here> Here is the circuit that I have developed. I am not very sure about the design. Here is what I want it to do. When the user presses the push button S2 the TPS_EN ...
22
votes
5answers
66k views

How do I fix an Omron d2fc-f-7n microswitch from unwanted clicks?

Omron d2fc-f-7n microswitches are used in computer mice all around, and they eventually start clicking several times per hit. AFAIK there is a flexible metal plate that wears out due to metal fatigue, ...
7
votes
2answers
2k views

How to connect external switches to this circuit board

I am circuit bending a walkie-talkie to move some of the switches around and embed it in a shoe. One part I'm not sure about is how to replace some momentary switches on the front with external ...
0
votes
3answers
2k views

Converting an NO reed switch to a NC with lowest leakage current

When the switch is closed I need the pin on the microcontroller to be high impedance, when the switch is open I need it connected to the ground. I need the leakage current to be minimal. What should I ...
0
votes
2answers
351 views

Multiple-microphones and mic-switcher

Trying to make a round-robin (time-slice based) array of microphones, which feed to the microphone input of a PC. There are 2 things I am looking for some ideas / pointers on:- The distance between ...
0
votes
2answers
660 views

Which float switch to use for my A/C unit?

This is my A/C unit in the attic. These are the two switches I've found. But the specs don't really match up with that document. Switch 1 I can't post 3 links due to lack of reputation but here ...
0
votes
1answer
239 views

What is this kind of switch called?

Please take a look at this video http://www.youtube.com/watch?v=6HKQTuVD2ac and tell me what's the LITTLE BLACK switch called where he changes the challenges (1 to 10) with. I guess technically it's a ...
5
votes
2answers
555 views

What are some cheap, reliable methods of water-proofing switches and buttons?

I'm working on a project to put together a custom bike light from some LED flashers and a battery pack. I'm looking at two different options, one which comes with a built-in switch, and another where ...
0
votes
0answers
46 views

Digitally programmable switch using minimum space (without relays) [duplicate]

Possible Duplicate: How to short two nodes electronically I want to make a pcb containing about 32 switches (that do a physical connection between wires) each can be programmed digitally from an ...
0
votes
2answers
2k views

Switching RCA composite video, under uC control - circuit ideas & suggestions

Trying to use Arduino TV-Out to switch feed to a TV set, s.a. ones found in Clinics, to display some information, s.a. next patient, expected delays etc. The TV is normally playing regular programming ...
0
votes
1answer
169 views

Finger movement detection devices

Let's consider a device such as a game controller or a standard remote control, but which is not controlled by "standard" keys. Instead, the idea is to minimize finger movement, such as in a keyer. ...
0
votes
2answers
172 views

Electrical Contact to Digital Signal

I am not normally into electrical projects or engineering so forgive my ignorance... I am working on a project that would involve a couple dozen electrical contact switches. I want all these ...
0
votes
1answer
670 views

how to design switching regulator in battery operated device?

My device consists of ATMega, GPRS modem and sensors. Modem occasionally hangs and I need to reset it from mcu. The whole system is powered from li-ion battery. I can't find any switching DC-DC ...
3
votes
1answer
4k views

How do I make a switch on the Arduino?

I have the Freetronics Eleven, which is 100% compatible with Arduino Uno. Ultimately, I want to make a foot pedal switch that connects to a digital pin on the arduino so that a LOW is read when the ...
4
votes
2answers
815 views

replace 20A switch with 16A switch

On a space heater, I replaced a 20A DPST switch with a 16A one I found at radio shack. I am unsure about the amperage of the circuit itself (how to find this?) but I'm assuming it's 20A or else the ...
0
votes
3answers
895 views

Question concerning n-MOSFET switching

I am wanting for safety a uC to determine a few environmental checks before a device is allowed to be activated, it is a relatively low voltage (2V) however high current (4A) load (powered by a beefy ...
5
votes
3answers
6k views

specifying a non-momentary switch?

If I say something like "SPDT switch" it's assumed to be a non-momentary switch. Is there standard nomenclature for unambiguously specifying a non-momentary switch?
2
votes
4answers
1k views

Are vacuums tubes suitable for switching high current (~30amps) at high frequencies (~K-Mhz)?

I was looking to build a system for high currents (say ~30 amps) and a friend suggested vacuum tubes. In theory, vacuum tubes seemed more robust for high current applications, but after looking around,...