84

Fans of that type have induction motors with two windings with a capacitor in series with one of the windings. For every individual motor design there is a certain capacitor value that allows the motor to develop maximum torque and operate at the maximum corresponding speed. Smaller capacitor values are used to reduce the torque so that the load overcomes ...


73

I'm going to put David Tweed's comment into an answer, which it deserves. The dual shorted pins allow inexpensive single-sided boards to be used for X-Y matrices of switches without requiring jumpers. Here (from an NKK datasheet) are a couple examples of such layouts: X-Y matrix (This would typically be scanned by a microcontroller or ASIC): Common ...


65

Using a regulated current source to light them, wire the LEDs in series and short out the segment which you want to be dark. simulate this circuit – Schematic created using CircuitLab You can possibly use a buck-boost converter to make the 30V if you don't already have a suitable voltage. Here's a simple way to build one using a LM2596S module: ...


52

Mechanical relays won't last long if forced to switch at 5 Hz, but solid state devices (thyristors, triacs or transistors) are perfect for your task. Instead of coming up with your own thyristor/transistor circuit, I suggest that you use a solid state relay. It's easier and safer. They consist of an optocoupler (for electrical isolation of the logic level ...


51

The 10k\$\Omega\$ resistor is there to pull down the gate when the input is floating (thus avoiding an undefined/uncontrolled gate voltage). On the other hand, the 100\$\Omega\$ resistor is there to limit gate charging/discharging current (due to the presence of gate capacitance) and to prevent oscillations. But, as you have already detected, both resistors ...


32

Delivery costs many times more than the items themselves Even from eBay? Whereabouts do you live? One way you can get spares is to smash open another mouse that's broken for some other reason. Perhaps a friend has a broken one? It may be possible to repair them. Those little switches have a snap fit cover, and can be opened up. carefully pull on the ...


31

Three major issues here. The first is that you don't seem to be aware that you're effectively building a dimmer circuit when you start using electronic switching. If you Google "theatre light dimmer schematic" you'll find a few useful links, including an old ePanorama article about different types. You may find useful links on the Everyday Practical ...


30

Firstly, forget the 100 Ω resistor for now. It's not required for the working of the button, it's just there as a protection in case you would make a programming error. If the button is pressed P2 will be directly connected to +5 V, so that will be seen as a high level, being "1". If the button is released the +5 V doesn't count anymore, there's ...


29

The answer depends on what you want the "default" configuration to be. For example, say you have a down-stream N-channel MOSFET, and you want it default off. Then you would use a pull-down resistor to ensure this behavior if the input becomes high impedance. simulate this circuit – Schematic created using CircuitLab On the other hand, suppose you ...


28

A "3-way" switch is SPDT. A "4-way" switch is DPDT inside. They're used like this: simulate this circuit – Schematic created using CircuitLab The 4-way switch is simply crossing the connections, or connecting them straight through — sort of an XOR function. If you only need two switches, just connect SW1 and SW2 directly to each other. If you ...


26

Quick disconnect terminals. They are good for permanent attachment too. The blades under the switch were intended for this type of terminal, so they should have a correct width and thickness. (page where the picture came from)


26

"Pull-up" is used more often in circuit design than "push-up". But I would imagine anyone would understand you either way. The pull-up resistor isn't increasing the voltage. It's simply connecting the 5V supply that already exists to the digital input pin of the Arduino. Digital input pins are designed to have very high internal resistance, so extremely ...


25

NO = Normally open (open = open circuit = not creating a path for the current) NC = Normally closed (closed = short circuit = creating a path for the current) C = Common (The drawings show the state in the absence of force.) When you press a normally-open pushbutton, you provide a path for the current. When you press a normally-closed pushbutton, you ...


25

A simple circuit to do this would use a single transistor, one resistor and a buzzer. Connect two 1.5 volt batteries in series to get 3 volts. Connect one end of a 10 kilohm resistor to the positive terminal of the batteries and the other end to the base of a general purpose NPN transistor (2N2222, 2N3904, etc.). Connect the negative end of the battery to ...


25

Of course there is a difference, else there wouldn't be two different methods with different names. If the load is floating, like a motor or solenoid for example, then high or low side switching makes no difference to the load. That is because, by definition of floating, the node only "sees" the differential voltage accross it and doesn't react to the ...


25

Glass is clean, dimensionally stable and very strong, doesn't outgas at the operating pressures in the interior of the capsule, won't react with the fill gas in the capsule, and doesn't soften under soldering temperatures. Here's a beautiful link.


25

It sounds like you have two problems. First, reed switches are delicate and shouldn't be used to switch a lot of current. When the switch opens (and, to a lesser extent, closes) a small arc is generated between the contacts. This can cause The contacts to eventually weld together, so that it won't open correctly, or A buildup of non-conductive junk between ...


24

N/C magnetic switches are unfortunately nearly useless for security. Since their "unalarmed" state is for them to be open, if the cable going to them is cut then the alarm will not trigger, and of course not be triggerable anymore. With a N/O magnetic switch the circuit is closed in the unalarmed state, and cutting the cable will trigger the alarm.


24

Each of your "lanes" is a "pole" in switch terminology. 1P (or SP), 2P (or DP), 3P, 4P... The number of ways you can connect those to outputs is a "throw" (T) - Single being ST, double being DT and after that, numbers. 3T, 4T... Some switches add "center-off." Single-throw switches are "off" one way and "on" the other, while DT are always on in one ...


24

How can this work without any multiplexer? It doesn't. The keypad board seems to have just switches, with maybe some diodes we can't see. However, the left board looks like it has a processor on it. Almost certainly, multiplexing is being done in firmware. The multiplexing algorithm works something like this: Drive one row high, the others low. Enable ...


24

I believe the search term you need is "double action". Example https://www.ckswitches.com/media/1897/kxt2.pdf


23

Digikey: Off-Mom = Continuous OFF momentary ON SPST Off-Mom-Mom = Continuous OFF two momentary ONs SPDT On-Mom = Continuous ON momentary SPST Mom-On-Off = Momentary ON continuous ON and continupus OFF SPDT Off-On: = Toggle ON/OFF SPST On-Off: Toggle = ON/OFF SPST On-Off, Off-On: = Toggle ON/OFF DPST inverted poles On-On-On-...


23

NO. The AC ratings of a switch don't translate well to DC. The critical rating of a switch is the current it can interrupt, not the current it can carry. When you open a switch, any arc that forms across the contacts erodes them. With AC, the current goes through zero many times per second, helping the arc to extinguish. With DC, the current is persistent. ...


22

The transistor shown is a P-channel MOSFET acting as a "high-side switch". More commonly, an N-channel MOSFET low-side switch is used, but what you have will work as long once you add something to the drain such as in this image of P-Channel MOSFET switch from http://www.electronics-tutorials.ws/transistor/tran_7.html: When the control goes "HI" the MOSFET ...


22

Your best bet is probably to use SSRs (solid state relays) which include drive and isolation circuitry in one package. They also include a thyristor and usually a heat spreader to interface with a heat sink, if necessary, that is electrically isolated. The mechanical relays are unsuitable, they will be noisy and wear out very quickly. Keep in mind that ...


21

There are various choices that can be made in the design of transistors, with some tradeoffs being better for switching applications and others for "linear" applications. Switches are intended to spend most of their time fully on or fully off. The on and off states are therefore important with the response curve of the in-between states being not too ...


21

Partial answer - could get very long - may add more later: Choices in this context are usually bipolar or MOSFET. Once you get to JFET you may also wish to think about SCR/TRIAC, IGBT, ... . You may wish to throw bipolar-Darlington into the mix. Short: Goes something like - Small bipolars up to say 500 mA and 30 Volt load voltage are low cost, can be ...


20

You could use a single FET, but there are several advantages to using a load switch IC. Voltages higher than the micro voltage can be switched. (That can also be done by using 2 transistors. ) The load switch has inrush current limiting built in. This can be done with discrete components as well, but requires more engineering. More often than not, load ...


19

You could use a SIP switch instead of a DIP. The saving in board area would give you the space for your I2C interface (or a simpler interface like a shift register with input latch): The picture shows it horizontal but it actually mounts vertically.


19

It is a gate with an inverted and a normal output. The idea is that the two outputs switch exactly at the same time. There is hardly any delay between them. The symbol as shown in your diagram is rather awkwardly made. More often the following symbol is used for a combined buffer + inverted like that: You will find these used with differential line ...


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