New answers tagged

2 votes

Is there a way to know if you're reading a 4 digit SMD resistor code upside down or not?

Without removing the resistor you can measure it in-circuit (both ways) and look at the higher of the two values. Your two possibilities are 1.02K vs. 1.20K. The former is an E96 series so if the ...
2 votes
Accepted

Can you identify this resistor or resistance?

It is either a temperature sensor or a diode, or a diode used as a temperature sensor. In either case it is unlikely to be broken. The more likely cause for charging problems is that the battery cells ...
  • 61k
1 vote

Circuit Analysis: R3(Missing), Voltage(Missing)

You're given total current as 3A. You are also given V_R3 = 38V. Since all the current passes through R3, then I_R3 = I_total = 3A. Then use V_R3 = I_total * R3 to solve for R3. Once that is done, ...
14 votes

What is that blue round thing below the resistor?

Looks like a simple spacer. It's bad (for reliability and stability through soldering) to have the part too close to the solder blob. Those are precision resistors (and it looks like some kind of ...
0 votes

LTspice: Noise of frequency-dependent resistor in noise simulation

Don't forget that the noise at one frequency does not involve \$\Delta f\$. Therefore the noise should be \$\sqrt{4\cdot 1.38\cdot10^{-23}\cdot 300\cdot 1}\approx 128.7\;\text{pV/}\sqrt{\text{Hz}}\$ ...
2 votes

Pull up resistor why is it low when switch is pressed

The circuit below is a reasonable representation of a standard microcontroller GPIO. In this representation, the GPIO is 8 bits wide. Only two pins are shown entirely, the others are omitted for ...
  • 3,729
4 votes

Pull up resistor why is it low when switch is pressed

simulate this circuit – Schematic created using CircuitLab In the left-hand case (switch open) no current flows through R1 (assuming the meter does not draw any current) and the voltage is V1. ...
1 vote

LTspice: Noise of frequency-dependent resistor in noise simulation

This looks like it can be done, I did not check to see if it gave meaningful results (because of time) The first thing is you need to use an dependent source (or E source) to generate a "voltage&...
  • 65.8k
2 votes

Query regarding 9 V battery connection to 7408 IC

First, The 7408 is not a constant current device, therefore it will not always draw 8mA, so the 600-ohm resistor will not work. I'm not exactly sure how you found the 8mA in the first place because ...
  • 102
0 votes
Accepted

Emulating waveform at lower current

I took @user253751 's advice and used spice to work out the RMS power usage at 6500 RPM. It came to 837mA. I then found 680uH inductors with at least this current rating measuring 12mm x 12mm and ...
-3 votes

How do I properly level convert between microcontroller and 3.3 V SPI pins?

Use a bi-directional level translator which converts 5V to 3.3V. Its easy to use without any changes in software or hardware. This company makes such level translators: www.maximintegrated.com/
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8 votes
Accepted

Why do we connect unused (always low pins) pins to GND through a resistor instead of connecting it directly to GND?

Your provided source material explains does not say it is required to use a resistor. All it says is that you must not leave the pin floating. It then suggests that, if desired, you can use a resistor ...
  • 49.6k
1 vote

Magnetic levitation without any microcontroller

The current must be AC and there must be a phase difference between the two coils, which requires the addition of capacitance or (perhaps more likely in this case) three phase power. There are not ...
2 votes

Magnetic levitation without any microcontroller

In order to produce eddy currents in the plate, the magnetic field must vary with time. For the magnetic field to vary, the current in the electromagnets must vary. There may be a DC component in the ...
4 votes
Accepted

Triangular wave response of RC circuit

It's an illusion. If you calculate the response of a 1st order lowpass with a ramp input and then differentiate its response, you'll find these: $$\begin{align} H(s)&=\dfrac{1}{s\tau+1} \\ X(s)&...
3 votes

SPI bus termination for variable line length / variable number of slaves

Slave response delays due to cable length create a sync problem in SPI A 4 metre cable of average sort of characteristics will delay a clock edge by about 20 ns from one end to the other. This is ...
  • 397k
4 votes

SPI bus termination for variable line length / variable number of slaves

I think you are really swimming against the tide here. You are asking for theoretical background, I'll do my best. The point about SPI termination is not about bus speed, but that the whole thing ...
  • 5,367
-3 votes

SPI bus termination for variable line length / variable number of slaves

Edit: Added notes making drivers of the bus stronger. For short distance SPI communication, push pull mode, the MOSI or MISO lines need not be pulled up or terminated with a resistor when connected ...
  • 115
3 votes

MOSFET gate failure caused by unknown reason

Based on the gate-source voltage and resistance measurements, \$|V_{GS}|\$ is exceeding 30V. In your circuit the only way this can happen is with the FET's internal inductance in series with the ...
  • 3,729
2 votes
Accepted

Should I use a magneto resistor and a solenoid to dynamically change resistance?

The effects you list are fundamental effects that occur when certain materials or material interfaces are subject to magnetic fields. The advantage is that this is essentially a passive effect, i.e. ...
  • 12.5k
1 vote

MOSFET gate failure caused by unknown reason

The gate capacitance is around 1 nF and you have a 4.7 MΩ resistor. Thus the turn of of the MOSFET will be slow. As well, there's the leakage of the Zener to consider. When simulating the circuit, ...
  • 5,867
4 votes

Time constant of a high-order RC circuit

It is almost impossible to obtain this type of 3rd-order transfer function in a meaningful expression without resorting to the fast analytical techniques or FACTs as described in my book on the ...
  • 15.7k
1 vote

Time constant of a high-order RC circuit

I guess that you measured "impedance" versus "frequency". The same simulation can be made if measurements are "impedance" versus "time". Here is a graphical ...
  • 7,201
2 votes

Time constant of a high-order RC circuit

It reminded me of a distributed RC delay, where the Elmore Delay approximation seen also here, might be useful for you. The first link provides a tutorial and discusses some limitations and ...
  • 1,172
1 vote

Time constant of a high-order RC circuit

A simple RC circuit is described by a differential equation.When you have multiple capacitor you need to solve a system of differential equations.The differential equations of the system come from ...
4 votes

What is the cause of my resistor going up in flames?

Based on the small dark spot on the capacitor, it is the IC that has expelled smoke towards it and left a mark on it. The capacitor is very likely OK as it doesn't have the characteristic signs of ...
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0 votes

What is the cause of my resistor going up in flames?

Given where the resistor is on the board, it's not only acting as a resistor for current inrush limiting, but it's acting as a fuse as well. Something else has shorted out on the board, and instantly ...
  • 15.6k
1 vote

What is the cause of my resistor going up in flames?

The photos look to me like the burnt marking on the capacitor has come from the side of the IC. Heat inside the IC probably cause the case to crack on the side and a flame came out and burnt the ...
  • 3,727
0 votes

Doesn't using resistors serial to LEDs all the time waste a lot of energy?

Yes, if you have an LED that requires 1.5 V and you're powering it with a 9 V battery; then the resistor would actually use 5 times the power the LED is using. The only thing you could do to increase ...
0 votes

Is there a way to increase resistance of a resistor with an outside current?

Motor driven potentiometers are available, in slide and rotary types and in B linear and audio tapers. You would have to build a servo amplifier and devote one of the tracks to feedback to make it ...
1 vote

Is there a way to increase resistance of a resistor with an outside current?

There are ways, see "carbon amplifier" and "magnetic amplifier" and "vactrol" for examples. (well magnetic amplifier is technically a variable inductance, but it's used ...
  • 27.9k
1 vote
Accepted

Is there a way to increase resistance of a resistor with an outside current?

First of all, I know (correct me if I am wrong) that variable resistors are a thing, but my problem with them is that they only work because they have hundreds if little resistors inside. Variable ...
  • 7,689
8 votes

Cascading resistors in series

5000 ohms + 1% of tolerance is 5050 ohms. Two of those in series is 10100 ohms, which is 10000 ohms + 1%. So same thing. However, whether it is recommended to split it or not depends on what is the ...
  • 97.5k
11 votes
Accepted

Cascading resistors in series

can I use two number of 5kohm 1% tolerant resistor in series , so that the equivalent resistance is 10kohm connected to ground? Yes, you can. Not many people do, as one resistor is usually smaller ...
  • 146k
1 vote

Compute voltages and equivalent resistance in the presence of a bridge

Nodal analysis on the original circuit gives, \$\large \frac{V_B-50}{R_1}+\frac{V_B-V_C}{R_3}+\frac{V_B}{R_4}\small=0 \$ \$\large \frac{V_C-50}{R_2}+\frac{V_C-V_B}{R_3}+\frac{V_C}{R_5}\small= 0 \$ ...
  • 7,467
5 votes
Accepted

Compute voltages and equivalent resistance in the presence of a bridge

I've just checked the first half of the problem by transforming the delta R3, R4, R5 to a star and get the equivalent resistance to be 44.8 ohms. Which agrees with your first set of calculations. ...
0 votes
Accepted

Battery with resistor: looking for verification that my understanding is correct

Assuming you are only connecting a resistor as the load, then yes. Kinda. Basic ohms law determines the numbers you provided. V=IR but we are looking for I amperage in Amps, so I = V/R, I = 12V / 4 ...
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2 votes

Battery with resistor: looking for verification that my understanding is correct

Conceptually it seems like you are correct except you are saying "the other side of the resistor" which is unclear. Also you say "use a 4 Ohm resistor." But it is not clear HOW you ...
  • 26.6k
0 votes

Battery with resistor: looking for verification that my understanding is correct

Yes, roughly. But you're not accounting for internal resistance of the battery. Look up the specs of your battery online and add its internal resistance to your 4 ohm resistor; then redo your math. ...
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3 votes
Accepted

How to find resistors from E series for a certain ratio?

You can create such a table yourself using Excel and a macro function. I've created one for the E24 series. Formulas: F3 cell: =E3*POWER(10;$C$2) G3 cell: ...
  • 1,528
1 vote

What amount of current (heat) can a pre-charge resistor handle?

Peak power is over 4kW (almost 100x steady-state rating). There's a chance the resistor won't just fry, it might literally explode. I strongly suggest you pick a resistor with a pulse power rating ...
1 vote

Battery with resistor: looking for verification that my understanding is correct

Here are the discharge characteristics of a typical 12 V 18 AH lead acid battery.
  • 12.2k
1 vote

How to find resistors from E series for a certain ratio?

I have faced this tricky little problem many times in my career, and eventually ended up with the solution of putting the E24 series (and 48, 96 and 192) into a spreadsheet. When I want to find a ...
  • 146k

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