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How to parallel shunt resistors with 4-terminals (Kelvin connection)?

As we know, shunts have the problems of: Temperature coefficient for resistance, Resistance tolerance and paralleling has problems of unequal current sharing and uneven temperature rise. These ...
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1 vote

Higher current or higher voltage from a power supply

If the device was a resistor it wouldn't matter (assuming that the power supply maintains both limits) Say you have a 12V 12W resistor, (perhaps it's a an essential oil heater), you could use a 1A ...
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3 votes

Higher current or higher voltage from a power supply

There are two types of ratings: One is what the device does. The other is what the device is the maximum capability or limiting conditions within which the device is able to properly perform its thing....
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-1 votes

Higher current or higher voltage from a power supply

I had originally posted this as a comment, but I think it is really more of an answer. The answer is obvious for a device that is essentially resistive, where there is a linear relationship between ...
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1 vote

What value of resistor is needed to limit current to 0.5 ampere in a 12V DC circuit?

It's generally a bad idea to add a series resistor to a DC motor because it will reduce the torque without reducing the no-load speed at all. It might be acceptable for certain types of loads such as ...
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3 votes

What is the limit for pairing batteries in series? What happens if we cross that limit?

how would the energy be transferred from one cell to another in such configuration as a cell has a seperating layer (the electrolyte) would the electrolyte degraded quicker because of such huge power ...
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9 votes

What is the limit for pairing batteries in series? What happens if we cross that limit?

The limit is whatever the insulation surrounding the batteries can handle. If you have one million 1.5 V batteries, then it is perfectly possible to put all of them in series, thereby creating a 1,500,...
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0 votes

What value of resistor is needed to limit current to 0.5 ampere in a 12V DC circuit?

The total resistance is 24 ohm on 1A. so to make it half a 12 ohm resistor is needed.
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3 votes

What is the limit for pairing batteries in series? What happens if we cross that limit?

As long as the battery management keeps all the cells balanced, none of them will experience any kind of anomalous voltage or power. The limit would be dielectric breakdown between the most positive ...
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2 votes

How to make two different frequency square waves stay in sync with each other at all times?

Short: Yes, you can. What you want is called phase locking. You need to make the two frequencies based on the same source, otherwise you will never completely get rid of some drift even with the best ...
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2 votes
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How to make two different frequency square waves stay in sync with each other at all times?

In the general case, it's called frequency synthesis. You make a second frequency as a rational fraction of the first. $$F_{out}=\frac{num}{den}F_{in}$$ In your particular case, if you take the blue ...
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1 vote

How to distinguish different temperature wire insulations?

You cannot tell just by looking at it. You can distinguish silicone from everything else by feel, but that is about it. If you don't know you can probably assume PVC which is the most common and also ...
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1 vote

How to distinguish different temperature wire insulations?

There is no place for mistake because it is matter of fir safety. So, unmarked wire take as lowest rate then calculating maximum current.
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1 vote
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What circuit for the following input and output?

The logic derived from the drawing is that from every third transition, output a negative pulse approximately 50% of the clock rising edge interval. This could be made more precise if there were ...
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2 votes
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Why does slow decay decelerate a motor faster than fast decay does in a H Bridge?

Slow decay shorts the terminals of the motor, by decreasing equivalent resistance, resulting in an increase in current. This increase in current results in a back emf in the motor windings—which ...
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0 votes

Why is a simple current limiter cycling when heat press plugged in?

There are two likely issues; Either the heating element is failing, which causes a short from Live to Earth, and thus trips your RCD (which can happen a few minutes into the process due to the ...
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4 votes

Can I run resistor at a power higher than rated if I have external cooling?

If you need a reliable design, no. Indeed you might not even get that, as the rating depends on ambient temperature and free airflow, and if those are in limited supply, you don't get the datasheet ...
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4 votes

Can I run resistor at a power higher than rated if I have external cooling?

It’s up to you to evaluate whether it’s okay. The manufacturer may not support you, since you are operating outside of the absolute maximums for the part. If you wanted to be on solid ground, then run ...
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0 votes

Can I run resistor at a power higher than rated if I have external cooling?

A typical example of such an "overpowered" resistor is the mobile immersion water heater. If you take it out of the water, it will burn. Another more sophisticated example is the travel hair ...
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0 votes

Which of the following is correct?

welcome to Stack Exchange. Let me help you answer this. With regard to your second statement, it is indeed false, as the DC operating point must be found to determine the AC small signal parameters of ...
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1 vote

Can I run resistor at a power higher than rated if I have external cooling?

Try water cooling as it will try to go to 200'C in air
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0 votes

Would this situation I have work or would something blow?

The only risk is if you apply battery voltage in reverse. The start/stall current is 6.6A @ 7.6V where the 2S fully charged battery voltage would be under these conditions depleted from 8.4V quickly ...
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2 votes

Do I need a resistor for my doorbell wiring?

Stepping up your voltage is a mistake. It won't do what you want, because you misunderstand the problem. When a smart doorbell is wired up with 2 wires, it powers itself (recharges its battery) by ...
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1 vote

Do I need a resistor for my doorbell wiring?

40 is the correct answer, where you got confused is 24V/0.2A = 120Ω, which is the finished resistance, not the initial resistance. The initial resistance is ...
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0 votes

How to light one or some LEDs with extremely low current?

With a classic bridge rectifier we only catch the enery peaks. This has a bad power factor. I have difficulties to simulate such an energy source, but I assume, that any change in charge should be ...
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1 vote

Can the current through a connector be higher than the rated current at lower voltages?

The answer, in most circumstances, is no. This current rating is the connector contact’s current limitation, i.e. the maximum current the connector contacts can withstand. Please note that current ...
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How to light one or some LEDs with extremely low current?

After reading the Wikipedia article on triboelectric nanogenerators, it looks like you will need to capture and store the pulses of power generated by the your gadget. Rectify the pulses, store the ...
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0 votes

How to light one or some LEDs with extremely low current?

The circuity is tricky since the current are very small. Luckily there is a whole sub-industry dedicated to this kind of applications. Search for "energy harvesting". The usual major ...
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14 votes
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Why not always use a higher millicandela (MCD) rated LED?

Assuming cost and availability aren't a concern, or other more subtle properties -- sure. Note the viewing angles are the same, so the visual intensity should indeed be somewhat better for the 65mcd ...
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3 votes

Why not always use a higher millicandela (MCD) rated LED?

The LEDs are not basically same, but completely different. For you it might not matter if you only look at the brightness versus current. For other purposes, they might be incompatible. They have ...
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2 votes

Short circuit broke a P-channel MOSFET

If you place a 10mF cap (the one in the upper right corner) on the p-mos drain, I would imagine that the inrush current while the cap is charging is what broke the MOSFET. That is, the cap is now ...
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1 vote
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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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Why does Pomona banana jack cable have 18 AWG but can handle 15 amps?

The item in question is an assembly not a wire. So a simple possibility is the connectors are the limiting factor not the wire. Don't overlook specs can be rather arbitrary. I'm doubt the manufacturer ...
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Why does Pomona banana jack cable have 18 AWG but can handle 15 amps?

Current ratings for wires and connectors are all about how much power you want going through it for a given amount of time. Pomona has specified that 18AWG cable can run continuously carrying 15A. You ...
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1 vote

Why does Pomona banana jack cable have 18 AWG but can handle 15 amps?

Current ratings for wire are not hard numbers. Copper can handle the current up until it melts or loses structural integrity. But in practice, the max temperature of the insulation used will limit ...
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2 votes
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Why does the LED turn off when I try to measure current?

Why does the LED turns off? The LED needs about 2 volts across it before fully illuminating. But, if the voltage across it drops below around 1.8 volts, it'll not illuminate at all. And, it'll drop ...
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3 votes
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Why is there current flowing through the resistor R1?

I'll assume by "input voltage", you mean \$V_B\$. We don't have values for R1 or \$I_{IN}\$, so I am not sure how one is expected to produce a graph of \$I_{R1}\$ vs. \$V_B\$. I suppose we ...
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1 vote
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Resistive current sensor shows reading when I connect it in series with a battery while no current is flowing through it

The shunt used only generates 375uV. This is not ultra low, but precautions are required. Common Mode Rejection Ratio: The INA219 has a typical CMRR of 120dB. Hence by moving the sense point to the ...
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2 votes

Why is a short circuit in the secondary winding of a transformer reflected on the primary side?

First a small back step. When Vp is applied to the primary winding, a primary current starts to flow and this causes a magnetic flux in the core, refer to the 'right hand rule' in physics texts for ...
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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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2 votes

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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0 votes

Resistive current sensor shows reading when I connect it in series with a battery while no current is flowing through it

You wrote: " I did the same with a multimeter and a reading of 0.0003 mV was obtained across the shunt, which is also negligible." Can you really measure 300nV ? An ordinary multimeter can ...
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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 ...
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0 votes

Why are there two NOT gates in a complementary PWM circuit?

Always be mindful that digital electronics is merely convenient analogue electronics. The AND gates have an analogue voltage range, consisting of two digital regions (valid logic LOW, valid logic HIGH)...
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3 votes

Why are there two NOT gates in a complementary PWM circuit?

The RC circuit will not produce a clean digital pulse. The edges will be rounded. Your drawing shows the rounded corners of the output of the RC circuit. The first NOT gate (actually a Schmitt ...
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2 votes
Accepted

How to calculate the current through the LEDs/the collector current in the BJT circuit

Assume beta is large, base current is negligible. Assume ideal zener diode: if current flows through it in reverse, it will deliver the voltage on the label. So, there's 4.7V across the zener, and the ...
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2 votes

Electric current flow

The battery sets up an electric field. This causes nearby electrons in the wire to move in such a way that there is a net charge on the surface of the wire. This net charge on the surface of the wire ...
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2 votes

How to get more current from laptop usb 3 port

USB 3.0 standard says it can provide up to 4.5W (0.9A@5V) of current, with dedicated downstream charging USB 3.0 ports providing maximum 1500mA (7.5W). 5V/2A is simply not possible. The internal ...
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0 votes
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Dependent source circuit find voltage

You need to introduce \$I_M\$ into the fray or you'll just get 0 = 0 and that helps nobody: - $$5 = 2\cdot I_M + V_A$$ Where \$V_A = 2\cdot I_M\$ (as per the dependent source) so: - $$5 = 2\cdot I_M + ...
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