# Tag Info

## Hot answers tagged voltage

49

OK. You say that it was a single jolt, and you pulled your hand away immediately. It was one of two things -- either it was static discharge and a true shock, but exactly what you would have gotten from a doorknob, you burnt yourself, or it was an actual shock and I can't count. You're running 5V through a $10\Omega$ resistor, which means that it's ...

18

The manual states that the panel has "blown fuse indicators" - red LEDs that will light when the fuse is blown. The simplest way to do this is to connect an LED and current-limiting resistor in parallel with the fuse. With a blown fuse (or no fuse) this would allow a small current to flow in the circuit - probably enough to light your test light ...

11

Even nominally "0 ohm" resistors have some resistance. The datasheet for the part you linked says that zero-ohm resistors have "< 20 mOhm" of resistance. I don't know how you're using this part, but in most cases for a resistor that small, the exact value of the resistor won't affect the current flowing through it very much, so you can ...

8

This is certainly not really 0Ω, since I’m pretty sure it is not made out of superconductor material. Hence, although we don’t know its value, it will dissipate some power as soon as you give it some current. The datasheet should give you the maximum ohmic value of this resistor. The power rating is determined by the package and how much power it can ...

7

The datasheet provides the real resistance (worst case) and current rating for the "jumper":

5

In general, batteries rely on chemical reaction to provide power. The chemical reactions generate a potential difference (voltage) between the terminals and this voltage depends on the battery chemistry. Table 1. Nominal voltages for various battery chemistries. Chemistry Nominal (V) NiCd 1.2 Lead-acid 2.1 NiMh 1.2 Lithium ion 3.6 I am not sure whether ...

3

Ohm's Law only applies to ideal resistors. It doesn't apply at all to non-linear elements like transistors and diodes, and can have significant errors when applied to real-world resistors. Ohm's Law is an approximation...a model... of real behavior. And George Box said it best: "All models are wrong, some are useful."

3

Voh and Vol are provided, just look at the datasheet for GPIO DC specifications. They are just based on the pin drive strength and at the rated current for that pin strength. At the rated current the drop is 0.8V. With less current, the drop is less. With no or very low DC load, the drop is almost nothing, 0V. Since the LED driver is a high impedance input, ...

2

Something like this should work for you: simulate this circuit – Schematic created using CircuitLab

2

It was either just a static discharge, or it can't just shock you, you must have also been in contact with some other metallic structure, such as a radiator. If it was a short sharp pain, then it was just static discharge. You get charged up moving in your chair wearing plastic clothing. Then you discharge when you touch something, like another person or ...

2

My guess is that it is an induction furnace. It doesn't heat the metal in the furnace (oven) by the heat dissipated in the water cooled copper coil, but instead the magnetic field created by the coil creates eddy currents in the metal in the furnace that needs to be heated. These currents in the metal cause heat dissipation in the metal, so they heat the ...

2

We’ve been over this. The GPIO source and sink capability depends on the ‘on’ resistance of the P and N driver FETs, respectively, a topic I and others have already addressed in your previous questions. That parameter, Rds(on), isn’t in the datasheet, but can be derived from V(oh) and V(ol) at a given source or sink current. Another name for this parameter ...

2

I should wait for the answers to the resistance measured and current needs but I believe its safe to assume a thin stainless steel braided cable of 4 feet is unlikely to support what you want to do. It has high resistance, aside from the issues about coatings or shorting to its case. Bowden cable is stainless steel cable in 2 or 3 layers meant for mechanical ...

2

R722 and VR722 appear to be the lower elements of a potential divider consisting of the undesignated resistor chain (1) on the right of the transformer. Lowering the resistance of VR722 will reduce the voltage at (2). (Think of the extreme conditions: if you reduce R722/VR722 to zero the output would be 0 V; if you open-circuit VR722 - making it infinite ...

2

In fact it is not so simple. The caps should be SMD ceramics, because they have low ESR and low inductance. The MOSFETs are usually also SMD in small package, they have good thermal conductivity, but you need multilayer PCB board (70um top/bottom layer) with lots of thermal vias that is acting like a heatsink.

2

Wait, it's on the DC or AC panel? On the AC panel it would be normal to have a voltage (in a no-load condition) due to capacitive coupling, even if the breakers were open. You could measure that voltage with a multimeter and it would be usually a small fraction of the full voltage, but possibly approaching the full voltage depending on the situation. However,...

1

Ground is only a definition of 0V But shared currents may conduct crosstalk from the trace resistance and inductance. Thus isolating power return currents from analog signal currents is paramount in any high SNR design. If the power currents go directly to the power source and the signal ground does as well but without noise added then they can share a ...

1

GND is a generic term that can refer to many different things. Simply put, it is a common point. A track fuse is a fuse made from a pcb track. For all intents and purposes it is a fuse. AGND is analog ground - this is usually a low current path that does not have significant current flowing as compared with PGND which is the power ground. This is the high ...

1

Vin is 12VDC - 24VDC regulated to 12VDC with ~8A max. Buck boost brings extra complications, cost, and losses. So you should check if you can get away with a simple synchronous buck. That depends mostly on the loads. For example if the loads are a bunch of 12V input DC-DCs powering CPUs and stuff like that, these will run fine on 11.8V. If you check the ...

1

You are talking about a 100W power converter and, sadly, the buck-boost is not quite the most efficient topology of all (especially in boost mode). Most probably you have seen a four MOSFET design where the big inductor is essentially inside an H-bridge: the controller drives in synchronous buck mode (more efficient) or boost mode (less efficient) and it's ...

1

Seagate’s Barracuda power spec is 12W seeking constantly and 3A or 36W surge startup on the 12V supply mainly. This design must have sequenced power to avoid the all at once surge. Thus a 1.5kW supply can power half of the drives easily if you invoke sequenced power on. This means only two 15A breakers required and the equivalent of 2 hair driers running. ...

1

Your calculations are correct. In reality it’s likely that the drives will draw rather less than the 36W each, but it’s wise to allow for the maximum. Check the current rating for your whole house - 5.6kW is a significant amount. You’ll also need to consider how to get rid of the waste heat, don’t just stack up dozens of drives. As you say, you’d need to ...

1

The motor spec for L and R and V will definitely e your currents. Holding current: I= V/R. For V=Vavg if PWM modulated. Moving current is reduced by L initially as dI/dt starts 0A at t=0 then rises (exponentially) with a 63% I time constant of T=L/R which tends to be in the 1ms range for small steppers. This means you can use a higher voltage for a period ...

1

The parameter would be the gpio mosfet on resistances. But the manufacturer doesn’t tell you that. What they do tell you is the minimum you can expect over temp and vcc. You can infer the on resistance via Ohm’s law then extrapolate what voltage you can expect at your given current. As well, there may be thermal, bond wire and total current constraints.

1

on what parameter does the minimum and maximum sourcing and sinking current of a GPIO depend upon It depends on the output resistance of the GPIO pin, which is not informed directly and may not be symmetrical. If you try to source more than 3.5 mA, the output voltage will drop below $(V_{dd} - 0.8)$ V. If you try to sink more than 3 mA, the output voltage ...

1

Batteries are generally considered to be voltage sources. Not textbook ideal voltage sources, but imperfect mushy, droopy, slightly variable voltage sources. They maintain a relatively constant voltage while the device takes as much current as it wants (within limits). I am not sure whether one of the functions should be to provide voltage or provide ...

1

There is no such thing as a transistor "fully on". There is "acceptably low resistance between the source and the drain (Rds)" and/or "staying safely away from the saturation region". In the datasheet you attached, you may want to look at the "Output characteristics" graph. You will see that at 3V gate voltage, the ...

1

You are using a switching power supply with a two prong mains connector. These often include a pair of (hopefully!!) Y1 rated capacitors bridging both poles of the mains connector to the output ground, for EMI suppression purposes. This lifts the output to half the mains voltage, if there are no further grounding provisions on the secondary (output) side. ...

1

In a cable tray, the electrons don't care if you parallel ten 1000 kcmil aluminum wires or seven 1000 kcmil copper wires. However the person paying for the wire cares, so you use aluminum because it's 1/3 the price. Different deal in a winding where you're all about making a lot of magnetic flux in a small space. There, density is so critical that you ...

1

This circuit is a voltage doubler which is designed by cascading a positive and a negative clamper circuits. It is a specific extension of voltage multiplier. It simply doubles the magnitude of the input AC voltage (in this case 5sinwt). Note: Here I am not considering the RMS value, only the peak value has been taken into account. For positive half cycle of ...

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