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New answers tagged switches

1 vote

Component Placement Strategy for Regulator and Controller

A couple of notes to add to the existing answers, in no particular order -- Paralleling transistors can be troublesome. You get extra congestion routing the gate, and the inductance to each ...
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Component Placement Strategy for Regulator and Controller

Assuming the input cap will handle most of the HF current, the two current paths (switch on/red, off/blue) differ only in these two parts of the loop: So your problems will be proportional to the ...
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1 vote

Component Placement Strategy for Regulator and Controller

The inductor should stay close to the switch node because: Besides the primary objective of minimizing magnetic interference due to high-dI/dt loop size, the secondary objective is to minimize ...
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16A AC rated switch contacts welding with 36V battery and capacitor. Can a series inductor fix this?

I think a good, practical solution to this problem would be to use a PMOS device with an ON resistance of 20 mOhms or so, and a continuous current rating of 74 amps, such as the IRF4905. They are ...

16A AC rated switch contacts welding with 36V battery and capacitor. Can a series inductor fix this?

The low DCR motor inductance is best regulated with a ramp up in frequency of constant pulse width such that the desired I impulse dI= V/(Ldt) where V reduces from rising back EMF RPM. The time to ...
1 vote

16A AC rated switch contacts welding with 36V battery and capacitor. Can a series inductor fix this?

Perhaps the problem is the input capacitor on your PWM controller. Essentially a capacitive (dis)charge welder. You may be able to replace it with a beefy TVS rated for more than than 36V but well ...
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Relay Open and close switch button Automatically

I don't fully understand the "after 2 seconds" portion, but essentially I think you're asking for a latching relay? https://en.wikipedia.org/wiki/Relay#Latching_relay This essentially ...

Looking for a simple circuit to switch power to IR LED's at night (2A @ 12 volts)

You would need an optical IR blocking filter to view daylight with a Light sensor chip and suppress the IR emitter spectrum then a comparator or transistor switch with the resistor load gain to go ...

Controlling ADC (on/off) with microcontroller

Sounds like a generally bad ideas; don't switch the power to something that you can even simpler put into a power-down mode. In power down, your adc uses 400nA typically; the whole support logic you'...
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Powering two loads from either one or two sources

Here's another way, using two Schottky diodes. Two microcontroller - driven electromagnetic relays or solid state switches may be used instead of the toggle switches. Since either of the power ...
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Running 15 amps through a 10 amp switch to power a 13 amp circuit?

Is the switch I was given able to handle the current? It will work well for a while, then the contacts will die or weld themselves shorted. Do I have to find a way to reduce the current, so the ...
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Running 15 amps through a 10 amp switch to power a 13 amp circuit?

A DC power supply often see a capacitive 0 charge on switching. Thus the ESR of the load cap and supply can be much less than <<0.1 Ohm and the switch must handle this contact turn on current ...

Running 15 amps through a 10 amp switch to power a 13 amp circuit?

You need a better switch to handle the 13A. That doesn't mean you can't also use the switch you are given. If for example it is the only one that fits on the front panel of your device (and fits ...
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Running 15 amps through a 10 amp switch to power a 13 amp circuit?

No. Switch is rated for 10A, not 13A. The load takes 13A at 24V. It might not work properly if you limit current to 10A. Depending on what the load is, it may not be possible to reduce current. If ...
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Running 15 amps through a 10 amp switch to power a 13 amp circuit?

1: No. The switch says 10 amps; 10 amps is less than 13 amps. 2: It's hard to "reduce the current" going through the switch. It's not so much putting a flow restrictor washer in your ...
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Control AC load via relay with DC trigger?

Standard 12 V DC automotive relays would do. Two would be required, one to switch on the headlight and the other to select 'high' or 'low' beam.
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Control AC load via relay with DC trigger?

Use a DC relay for this with enough current rating for the lamp, like those used in cars. The trigger source defines the coil, not the load.
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How are switch ratings determined?

Switch ratings are related to the designed breaking capacity: it's much more difficult to break a circuit while current is flowing than it is to simply not impede flowing current while the circuit's ...
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How are switch ratings determined?

Switches as relay contacts can become complicated. They are rated according to the electrical and mechanical characteristics. This includes such things as contact material, contact spacing and of ...
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How are switch ratings determined?

no a switch isn't like a small resistor. A mechanical switch does not consume power. Think about, a switch is an open circuit when the interrupter is open, and is a short circuit when is closed. A ...
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How are switch ratings determined?

When closed, up to 3 A can flow through the switch. When open, up to 250 V can be blocked by the switch. You cannot multiply these two numbers because they describe different cases. When used with 12 ...
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Bi-directional current source based on MOSFET or IGBT

Your requirements are working against the physical reality of the inductor. I'll provide you this approach based on energy concepts. An inductor in which the current is $i$ will hold an amount of ...

Bi-directional current source based on MOSFET or IGBT

As demonstrated by Andy, you need a very large supply voltage in order to switch on the current fast enough for your design goal. With some magnetic engineering you can get away with a lower supply ...
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Detect multiple switches in series individually

You may use this answer if you replace the LEDs by solid state relays. You may have to adapt the resistor values to meet the selected SSR's specs.
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Bi-directional current source based on MOSFET or IGBT

EE&O ... For your information, here is what happens with such "load". NB: rise time (50us for the first 2 pulses and 100us for the other 2) is included in the generator. Note the ...
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Bi-directional current source based on MOSFET or IGBT

my target is to switch on/off a 10mH inductive load with 3.5A in an extremely short time (<50us), the inductive load will generate a large emf inverse voltage due to large dI/dt. When "...
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1 vote
Accepted

What is the MCU-Pinmode equivalent of a button-press to ground in this scenario?

Yes for simulating a button you must have a low output to ground it or high-impedance input (no pull-up or pull-down) to let the pin float. For driving the transistor, you can just have an output that ...
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1 vote
Accepted

How to detect welded contacts of a redundant relay? (for reliable high-current e-Stop)

Interesting question. Although DPDTs are challenging to find in the VDC and current ratings you require, automotive SPDTs are readily available. With those, you can do the following: simulate this ...
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Transistor in pull-down "switch" application

If we call the potential you use to control your switch "IN", and the node to be pulled down "OUT", any of these will do: simulate this circuit – Schematic created using ...
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Transistor in pull-down "switch" application

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Transistor in pull-down "switch" application

Example for NPN with emitter connected to GND and the load in the collector path: Define the expected load current and voltage, here e.g. 100 mA and 24V Find a transistor, that can operate with a ...
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1 vote

Is there a way to predict the VDC rating of a relay in function of its VAC rating?

The only thing you can say for certain about the DC rating of a relay is that it will be less, much, much less, than its AC rating. There are various features the relay designers can use to increase ...
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1 vote

How to detect welded contacts of a redundant relay? (for reliable high-current e-Stop)

(I misunderstood the question to start with, but I think the answer to that could still be useful, so I'll leave it up, below the break.) Answer to the correct question: There are contactors with ...
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How to detect welded contacts of a redundant relay? (for reliable high-current e-Stop)

You could do something like this: simulate this circuit – Schematic created using CircuitLab One 14-pin jellybean chip, a few resistors or networks and one LED. OA1 and OA2 form a window ...
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1 vote

How to detect welded contacts of a redundant relay? (for reliable high-current e-Stop)

Have an "off light". Remember, the "stuck contact" condition simply cannot be detected while the machine is intended to be on. Use DPDT relays. On one pole, use the NO contacts for ...

Automatic voltage selection using SPDT relay

how to improve the whole design to add reliability and protection ? The whole design seems correct. At least it provides the functionality. And powering the relay's coil from PSU instead of battery ...
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Automatic voltage selection using SPDT relay

Here's a simpler solution, using Schottky diodes that have a low forward voltage drop. The power supply, that is set to 13.8 V to reverse bias the Schottky diode in series with the battery, will ...
• 10.5k
1 vote

Question about Disconnect Switches

Never mind. I found the answer in the legend. See attached
Accepted

What's inside this RF absorptive modulator?

The clue is in those four arrows forming an X. That's a common way to draw a quadrature hybrid coupler. A signal incident on one input splits its power equally between the two outputs, but with 90 ...
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Can I digitally open a circuit?

If you want to allow a microcontroller to turn itself off, this may help for a start: simulate this circuit – Schematic created using CircuitLab When the user activates the circuit with the ...
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