texts: Charge Distribution on a Microstrip Line

texts:
let's consider a microstrip line connected to a voltage source V0 (applied between the strip and GND plane). According to foundation for microwave engineering (collin) book, the surface charge density on the strip is the following one:

I am looking for a physical explanation of this behaviour.

Precisely, let's consider the instant in which the microstrip line is connected to the voltage generator. Step by step:

1) The voltage source provides many positive charges at its positive terminal and many negative charges at its negative terminal. Let's focus on the first one, which is directly connected to the strip.

2) Charges provided by the voltage source will try to distance themselves due to Coulomb repulsion and will go predominantly at the edges of the strip (this may explain the reason by which the surface density is infinite at the edges of the graph).

3) The voltage source will provide other charges which I think will go at the center of the strip. How will the charge distribution be influenced by this factor?

4) Where will the following charges locate?


texts: For most low-side switches I've seen, an NMOS device is used. I am wondering, is it not possible to use a PMOS device in a low-side switch?


texts:
I was reading about full-wave rectifiers and came across the schematics below which the capacitor C can smooth its voltage, but I didn't understand one case:

We know that when the rectifier's voltage begins to falling from its peak, the cap C starts to send its charge to load. Where does the falling current coming from FW rectifiers go? (The current from peak to zero and that one who rises from zero to the point which the cap starts to charge in diagram) Is it blocked, by diode or capacitor? Why?


texts: Can you combine the outputs of two ports on a USB Battery Pack?

texts:
I have a quick question: I have a USB battery pack, and I want to use that battery pack to power a little side project that I have.

Currently, this side project takes an input of 5V 4.8A, and I have seen USB Battery Packs that output 5V 2.4A on one port, and 5V 2.4A on another port for a total of 5V 4.8A.

I was wondering, if I ran two USB cables with their heads plugged into a 5V 2.4A (per port, 2 ports) USB battery pack, exposed the proper wires, would I be able to combine the red wire of one USB cable with the red wire of another USB cable and black wire of one USB cable and the black wire from the other USB cable to create an output of 5V 4.8A?  sort of like what is happening below in which many wires are soldered together, and then connected into a single red

Otherwise, could I split the ends of the wire that extends from the side project (the item I am trying to power) into two, so: split the end of the red wire in half and the end of the black wire in half. Then, attach a red/black wire to each half respectively and in the end have two red wires flow into the 1 red input wire needed to charge?

Thanks,
A community member.


texts: Why do we still use Bipolar Transistors for Class A,B Amplifiers?

texts:
I'm working on a 4MHz HF power amplifier (Very simple) and was wondering why people still use bipolar transistors for class B amplifiers?

Do they have better linear current gain etc. vs a FET? Is it because you only need 0.7V above the emitter to conduct so there is minimal crossover distortion (logic level FET could help this)? Is it because "it is how it has been done forever?"

Most of my experience is with Class D and up style amplifiers. Where I mostly just care about operating as a switch and ignore any linear effects.


texts: How do some SAR ADCs allow the input range to be 0 to 2xVref?

texts:
If the capacitive DAC on the ADC uses Vref, would it not output a signal from 0 to Vref to the comparator? How would the comparator work if the input signal is greater than Vref since it would always output all 1's.

The AD7914 allows the input of the ADC to be 0 to Vref or 0 to 2xVref by changing a bit in a register.

Does it use an internal resistor divider to reduce the input by half?


texts: How to construct a 10x8 ROM using two 9x8 ROMs

texts:
I used two 9x8 ROMs and used a decoder as enable for both ROMs. Now I have two 8 channel outputs from the two 9x8 ROMs, how am I supposed to make them into a single 8 channel bus? Or is my approach wrong?

Is this question even valid? Here is the actual question our teacher gave us.
"Construct 1K * 8 PROM using two 512*8 PROM. Use enable if needed."


texts: OpAmp Design Questions for Transimpedance Amplifier

texts:
I'm trying to improve on a transimpedance amplifier design by changing out the op-amp that I'm currently using for another one. The issue I'm facing now is that I'm unsure as to how to pick a good op-amp based on my needs.

My transimpedance amplifier circuit is shown below. I'm using the SensL MicroFJ-60035 silicon photomultiplier (SiPM), and the amplifier I'm currently using is the TI OPA656.

simulate this circuit – Schematic created using CircuitLab

SensL requires you to give your email for their datasheet, but I'll try and put some info on the device here. If you need more information, please let me know, and I'll add more info here. The spectral range of the sensor ranges from 200-900 nm, and its dark count rate is 80 kHz/mm squared. It has a typical gain of 5.3*10^6, a dark current parameter of 4.1 uA, and a rise time of 300 ps. Also, the sensor is rated for a max current of 15 mA.

The OPA656 is a voltage feedback amplifier with a slew rate of 295 V/us, and it has a gain bandwidth product of 230 MHz and a bandwidth of 500 MHz. It has an input bias current of 1 pA, and it has an input offset voltage of 100 uV. Also, the capacitance at the anode output is 4000 pF. The datasheet never said about the capacitance at the cathode output.

Right now, the issue I'm facing with my design is the speed. Currently, it's too slow, with the rise time at 14 ns. My team and I have managed to reduce the rise time of the circuit down to around 6.5-9 ns by reducing the feedback resistor from 470 ohms to 25 ohms, but the gain is so tiny, with the max amplitude being around 160 mV. I am trying to find a new op-amp that would allow for a faster rise time without the necessary drop in gain.

As I did some research, I don't necessarily have a full understanding of the nuances of op-amp design, so I focused primarily on the slew rate. However, I found that as the slew rate increases, the bandwidth decreases. Here's my first issue. My team needs a certain bandwidth requirement, but if the relationship between the slew rate and the op-amp bandwidth is inversely proportional, how do I determine the amount of bandwidth I need for my application? Is it based on my SiPM, or is it from the test environment on which the SiPM is tested?

My next question also relates to the bandwidth of the op-amp. A smaller BW means that the amplifier won't work on high frequency signals outside of its range, but how does that affect the output voltage? I found some SPICE models of my SiPM as well as the OPA656 and some possible replacement amplifiers (specifically the AD8014, ADA4895, ADA4860, and the AD8001). These replacements have a faster slew rate, but the bandwidth is smaller. Would a smaller bandwidth result in a smaller but faster output voltage? If this is the case, then this isn't too big a problem. We don't necessarily need a large voltage signal; having one at around 600 to 850 mV is enough for our needs.


texts:
I stumbled across this line in this datasheet (page 10):

  Serial Data Output Pin. Internal N-Ch FET with open-drain output that
  requires external pull-up resistor. It shifts out the previous eight
  SDI bits that allow daisy-chain operation of multiple packages.

Could somebody briefly explain what this means? Specifically, if I'm not planning on using the daisy-chain functionality, can I leave this pin unconnected or do I need to connect it to an external pull-up resistor regardless?


texts: diagnosing transistor failure in H bridge

texts:
I built the H bridge shown in the schematic below for use with an unknown motor I pulled off of a broken CD player. I was seeing how hard I could drive the motor using large values for Vcc, and inadvertently applied well over the transistors' max collector/emitter voltage, 40V, albeit for a very short period of time. When running the same Arduino code I was using before I toasted the transistors (which ran the motor in the pattern left, off, right, off, repeat), the motor now seems to only run in one direction. It runs at full capacity for 1/4 cycle, and at low capacity for the other 3/4 of the cycle. I used an ammeter to confirm it was truly running at low capacity rather than just coasting for the 3/4 cycle.
In my research to solve the problem, I've become aware this is a poor H bridge circuit, but I would like to save it if possible, since soldering takes me a very long time. Given the behavior described above, is there an easy way to narrow down which transistor(s) are broken without unsoldering them and using the diode function on a multimeter?


texts:
Is this an optimum wiring scheme for draining and charging seven 12v SLA batteries of different amp hour ratings wired in series/parallel for 72v 28ah output?
(powering a scooters speed controlled 1.5kw brushless motor)


texts:
I'm in the process of designing a controller PCB for a 10x10 white LED matrix clock (inspired by the tutorial here). It's based off an ATmega328 AVR IC and Maxim DS3234 SPI RTC.

However, I'm stuck: I have no idea how to control my custom non-standard 10x10 LED matrix. Originally I was going to use a Maxim MAX7219/7221 IC, but it can only drive 8x8 LED matrices. Then I was looking at some sort of charlieplexing solution with a ULN2803 darlington transistor array. The bright white LEDs I'm using need at least 30mA of current.

Here's my preliminary schematic (sorry it's not too clear, but note the I2C and UART lines are available for use):

Here's an example wiring schematic of my LED matrix (NOTE: the example diagram below only shows an 8x8 matrix. My matrix is 10x10.)

What's the best way to drive my 10x10 LED matrix with the AVR? (Also, PWM is not a requirement, but would be nice.)

Thanks!


texts: Switching power supply (SMPS) for servo motors

texts: I would like to find a switching power supply to power one ClearPath servo motor. I am aware that SMPS is not recommended for servos, but I don't need power for fast deceleration/acceleration. Beyond current/voltage requirements, I am a bit baffled as to how to find a reliable SMPS that can handle some regen power. Hopefully someone can provide some insights.


texts:
So I tried compiling this code below but keep getting the 1176E error message of

  Branch offset out of range 0xFFFFFFE8 out of range permitted values are up to 0x00007E

on the 5th code line. I read the error description on ARM site but can't make since of it. I think it my be something to do with the fact that this code is in a sub procedure maybe? Anyways it looks like using rout can help, but I am not sure how to implement that instruction in the code below and what pushes the PC out of range in the first place?
Can anyone shed light on how to use rout in this case to subvert the error?

powerCount           PROC
                     MOV r4 , r1              // get a copy of test value
                     MOV r9, #10              // make a divisor
                     MOV  r3, #0              // initialize a counter
loop3                CBZ r4, check            // check loop condition
                     ADD r3, r3, #1           // record the number of di
                     SDIV r4, r9              // divide the value toward
                     B loop3
                     ENDP


texts: Feeding multiple 50 ohm terminated outputs from a single 50 ohm source without signal degradation

texts:
I'm having an issue in which I have a trigger from an instrument meant to be sent to another instrument with a 50 ohm termination. I want to use that signal to distribute it to several outputs that are also terminated with a 50 ohm resistance. Because these terminations are now effectively in parallel, the signal voltage level drops significantly (because of the 50 ohm output resistance of the source) and the triggers are missed.

Because of the BNC connectors, it is not very clean to interface to an op amp buffer, that I would have to design a whole PCB for.

Note: The voltage levels are not those of standard coax video formats (e.g., SDI), so commercial inline buffers/splitters are not really relevant. Instead, it's \$5 \text V_\text{p-p}\$.


texts:
Given:

\$U_q = 220 V, f = 50 Hz, R_i=10 \Omega, R_a=40 \Omega, L_a=95.5 mH\$

I'm asked to determine the real power transformed in \$Z_a\$. Here I break down the formulas that I use:

\$Z_{total}=Z_{La}+Z_{Ra}+Z_{Ri}\$
\$I={U_q\over Z_{total}}\$
\$P = Re[U_q . I^*]\$

I'm really sure that my calculation is right using that. But it gives a really different answer than the answer key, can you see what's wrong with my formulas? Can I use \$U_q\$ directly as \$U_{load}\$?

I thought the current are in series so it's must be the same, and also the voltage is parallel so it's must be the same. So how can I determine the power only in \$Z_a\$?

EDIT:

Here is my calculation:

\$Z_{total}= j\omega L_a+R_a+R_i=(50+30j)\Omega\$
\$I= {220\over 50+30j}={55-33j\over 17}A\$
\$P=Re[220({55+33j\over 17})]=711  W\$

And the correct answer is 284.7 W.


texts: How to turn an SPST momentary push button into a momentary DPDT?

texts:
How to turn an SPST momentary push button into a DPDT? I would like to close 2 circuits at the same time. (From comments: I want to ground the reset circuit while getting a pin to HIGH on an Arduino like board.)

SPST

DPDT

Image source.


texts:
I am currently trying to improve my understanding of analogue IC design and my textbook kind of brushes over this problem.

It is made quite clear that a low output impedance is desired so that the output voltage and current are mostly spread across the load impedance. However, in design (specifically in small signal analysis) a very common way of improving the gain is to increase the output resistance (since transistors amplify by means of the output current).

I understand that both can be achieved in multi-stage devices ex. with a buffer amplifier stage at the output.

My question is: how do I reconcile these design goals, particularly in single transistor circuits?

Cheers


texts: LM324 instead of LTC6081 for thermocouple

texts: I have circuit schematic with LTC6081 for thermocouple, but LTC6081 isn't available in my country. Can I use LM324 instead of LTC6081?


texts:
I need to test a differential ADC (with AIN and /AIN).

After some tests, I don't understand the behavior.

Let's use the AD6644 (taken from this Analog devices document):

  As shown in the functional block diagram, the AD6644 has complementary
  analog input pins, AIN and /AIN. Each analog input is centered at 2.4
  V and swings ±0.55 V around this reference (Figure 21). Because AIN
  and AIN are 180° out of phase, the differential analog input signal is
  2.2 V peak-to-peak.

Does this mean I cannot feed AIN or /AIN with a voltage higher than 2.95v (2.4+0.55) or lower than 1.85v (2.4-0.55).
 Then the input range is 1.85-2.95v. What is the behavior if I put /AIN at ground (0V) and the AIN input signal at 2.4v +-0.55v ?

EDIT:

Maybe my misunderstanding comes from the board I am using. This board doesn't contain any differential output opamp and contains only two different signals for feeding AIN and /AIN. With the possibility to set one or both inputs at 2.5V DC. It uses the ADC with no AC-coupled inputs... just as a "differential" (AIN - /AIN) ADC...

Obviously, the board  uses this diff ADC as a single-ended ADC.

Does the input offset of the signal matter or not ?

A) /AIN=0V AIN=SINE 0v offset, 2.2V p-p
B) /AIN=2.4V AIN=SINE 2.4v offset, 2.2V p-p

A and B are supposed to give the same result. Aren't they ?

Or A doesn't work or is not efficient because doesn't respect the 1.85-2.95v input range.

And AIN and /AIN AC-coupling at 2.2v p-p with 0V offset AND 2.4V offset (or any other offset) are behaving same ? Only the 2.2v p-p does matter or the 1.85-2.95v input range too ?


texts: If my electronics are outdoors in a ventillated NEMA 4 enclosure, should I conformal coat my circuit boards?

texts: I'm considering putting a circuit board in a ventilated NEMA 4 enclosure outdoors. I'm a little concerned about humidity and condensation inside the enclosure. Do I need to conformal coat my circuit boards, or take any other precautions?


texts: Estimating the power usage of a contactor

texts:
I'm trying to figure out the energy cost of the Hartland HCC family datasheet of contactors, in an application where they are pretty much active (contacts closed) 24/7.
I understand that in an AC application, just using P=squared(V)/R doesn't work because of the power factor. In any case, putting the datasheet numbers in that equation would lead to ~80 watts, which doesn't make sense.
Directly using the "sealed VA" rating (5.5-15VA) as watts is more realistic, although I remember enough AC theory to know that VA aren't watts - and it still feels high.
Does this datasheet provide enough information to evaluate the power dissipation? If so, how? If not, what would be a typical energy use for such a contactor ?


texts: Nature of analog channels on digital/mixed oscilloscopes

texts:
Can someone please help with scope terminology?
Some scopes have "analog" and "digital" channels. Am I right in thinking that the "analog" channels are in no way similar to the old Tektronix 475 I used to use at work, but are sampled/interpolated etc.? In which case, why are the "digital" channels different? It's pretty clear that none of the modern scopes have CRTs. Is it just that the digital channels are similar to logic probes and resolve to zero and one?


texts:
I am using dynamo on my bicycle to power the lights, as I hate using batteries. This serves me OK, apart from the fact I have constant problems with the end of cables.

The end of the copper braid (few cm) becomes whitish and stiff after some time and turns to powder when touching it.  Which means I have to constantly cut the wire and repair the problem.

I wonder, are there any special electric cables resistant to atmospheric influences, especially water, or I just had a bad luck picking low quality cable?


texts: Powering a PLC and transmitters during a power failure

texts:
I have 25 locations spread out over a large area we recently had another power outage lasting 48-72 hrs.depending on the location.
all locations have UPS back ups with generators.
Problem:

The ups does not last but 6- 8 hrs.  All equipment runs on 24 vdc. at about 3-3.5 amp stedy draw.
Generators are running for days to power a PLC. I have people running around check generators round the clock.

I propose remove UPS and install 2, 12vdc lead acid type batteries in series 200 amp hr.each to power the system.
So the system runs off the batteries 24/7 this should have a smooth current out flow immune from spikes??Yes/No??
I also need to be charging the batteries all the time??  I hope to size the batteries to last 72 hrs or more.
Can this work??  Benefits no expensive UPS ours are pricey, no wear and tear on the generators, no fueling the generators during the outage, no people checking operations round the clock during outage.
need a solution.


texts: Avoiding RCD tripping with Inverter Drive

texts:
I have a single-phase inverter drive hooked up to an RCD supply, which keeps tripping when powered. Removing the RCD is not an option, so I'm looking into other ways to make this work.

Although dangerous, hypothetically, would removing the Earth connection from the drive solve the problem? In doing so, there would be no current leakage down to Earth.


texts: How would i go about detecting if a rs-485 cable is plugged in?

texts:
The basic problem were trying to solve is certain secondary device's cables gets left unplugged and we need a way to detect a cable that is plugged into my device,and check if that cable is actually plugged into a secondary device and not hanging around unplugged.

I have a cable with 5 pins on both ends that are plugable i have 2 pins that are not used in the connector's and 1 pin is ground,and the other 2 pins are rs485 signal pins.My device has a mcu,and ports on the pcb that one end of the cables connector will plug into,i dont have access to the other end of what the cable will plug into.what i need to be able to detect is

If the cable is connected to my device
Is the other end of the cable connected to a secondary device

Iam not sure if this is even possible with how iam trying to go about this, without there being a mechanical switch inside the connectors or on the connector ports.
Any input is appreciated thanks

EDIT:Just to clarify the network isnt and cant use any termination resistors,and we dont have any control over secondary devices software,or hardware as they dont implement termination resistors,or a software response system on there end.


texts:
I am fairly new with non linear systems. I understand that a general representation of a nonlinear system is:
$$
\dot{x} = f(x) + g(x)\cdot u
$$

where \$x\$ is the state variable, and \$u\$ the input. My question is rather general: can \$ f(x)\$ be just a constant? Example: would it be possible to have:

$$
\dot{x} = 3 + 2x\cdot u
$$

Thank you very much for your help.

Lello


texts:
I have always wondered about how USB devices actually communicate. When I stripped a usb cable, I noticed that there were four different wires. Two of them being for power (positive and ground) and also two other wires.

I have searched up the pin names of these two other USB connections and they are called data+ and data-. Are these two wires used to send data signals, and if so why are there two (one for each data output for each device?)

What if the two devices are at two different clock frequencies? Wouldn't this mess up data exchange? And the questions which really hits me in the head is, how does one device "know" if the other device needs power, if the other device has no power source to "tell" the "master device" that it needs power? Can someone give me an overview about how the USB protocol works?


texts: Can anyone explain how device drivers work? I have seen Arduino and other development boards communicating with the PC's USB port with the help of a FTDI chip. This thing can be made to work after we install the device driver. So, what's the role of the FTDI chip and the driver here? Why can't we do this job without a FTDI chip, directly connecting the Atmel MCU(I have worked with AVR MCUs only) and having some proper driver for it.


texts: This is probably going to seem like a dumb question but how would you calculate the current i1 in this example?


texts: Capacitive reactance related to frequency

texts:
Why does capacitive reactance decrease with the increase of the frequency of the applied signal?
It is easy to prove why capacitive reactance decreases with increased capacitance. The more we increase the capacitance of a capacitor -> for the same charge at the plates of the capacitor we get less voltage which resists current from the AC source.
But why is reactance decreased with the increase of the frequency of the applied signal?


texts: Identifying DC electrical power connector

texts:
I have here a PowerFilm 10 Watt F15-600 Solar Panel, and attached to the panel is this connector:

The male end attached to the panel has a little green rubber gasket on it and the female end goes to a 12V female "port" into which you can put a 12V male cigarette adapter.

Notice how there is a gap in the right-side of the male plug and how there is a corresponding slot in the female one so that the polarity won't be reversed. Also, the clip won't attach if it was reversed.

I am just wondering if there's a place I could get more of these female ends so I can make more water-resistant attachments to the solar panel. The socket is a pretty good design, but I wonder if it is a proprietary design.


texts: I am trying to design my first PFC (power factor correction), and I am looking for the right inductor, but all the datasheets I've seen so far have the inductance rated at 1 kHz or 100 kHz. My question is, how do i calculate the actual inductance at the frequency I am using? Thank you


texts: Question about the 3-transistor current mirror

texts:
This is a basic 3-transistor current mirror:

I see some circuits add an extra resistor from emitter of Q3 to \$V^{-}\$. Just like this:

What's the purpose of this resistor?


texts: In series RLC circuit, does increasing capacitance value really make the circuit more inductive circuit?

texts:
This seems very counter intuitive to me. How can increasing capacitance value make the circuit more inductive ? The math tells me so :

If \$C\$ increases then \$X_c = \dfrac{1}{\omega C}\$ decreases, so the circuit becomes more inductive.

But I've heard that factories that use heavy motors have a large \$X_L\$. For this reason they need to increase \$X_C\$ so that \$X_L = X_C\$. To increase \$X_C\$ they seem to "add" capacitors. But adding capacitors actually decreases \$X_C\$ right ? \$X_C \propto \dfrac{1}{C}\$. How does this work ?

Definitions :
\$X_C\gt X_L\$  : more capacitive circuit

\$X_L\gt X_C\$  : more inductive circuit


texts: Recent Innovations forced mostly by newer and stricter government regulations have brought us through extremely unreliable CFL light bulbs from the old incandescent light bulbs to these very expensive yet aledged long life LEDs.  So far I'm okay with these LEDs especially how cool to the touch they  are.  But I have been noticing a high frequency flash involved.  One can see the flash by using a fidget spinner and observing the light and area it illuminates.  Is this something we should be be thinking  about as far as health issues may be concerned?


texts: How to measure added voltage to my input?

texts:
I want to measure the voltage I'm adding to my input signal to my amplifier. My setup looks like this:

simulate this circuit – Schematic created using CircuitLab

Just to be clear, I've used the opamp symbol since we don't have amplifier symbol on circuit lab. Not that I'm aware of. But I'm depicting an amplifier with gain of G.

Ideally, the output \$z = G(x+y)\$. However, the amplifier have a gain error e. so the true output is \$z = (G+e)(x+y)\$.

Assuming that my amplifier has no offset error (just for this setup) and the only things I can measure are the input signal y and output signal z, I'm looking for a way to know the value of x.

What I'm looking at now is to input two values y1 and y2 to get z1 and z2. \$(z2-z1) = (G+e)(y2-y1)\$ so I'll get e. From y2, I get x.

Is there a simpler and more direct way to do this?


texts: Current leak detection circuit for 24 volt DC - Incoming Current equal to outgoing current

texts:
I am planning to make a 24-volt DC circuit breaker with MosFET, when there is earth leak in the load (DC motor), or a human touches the terminal (24 Volt DC) with hand, to simulate AC, earth leakage detection relay operation. Currently used is a small shunt resistor with op-amp current sensing circuit as below, connected Arduino to drive a buzzer when leakage current reaches 1 mA. But I am not able to detect current changes. The supply voltage used is 12 Volt DC. The Op-amp used is 741.

Design Assumption.

When incoming current equals to the outgoing current through sensing resistor or difference between them equal to nearly zero, no leakage is happening in the circuit.


texts: How to make LED flash once every 5 seconds using using 555 timer?

texts:
I know this is not new but i really can't find a circuit that makes an led flash once every 5 secs. I hope somebody can help me out.

Thanks a lot.


texts: Derivation of convolution integral from the discrete convolution sum?

texts:
I was wondering if anyone can provide a derivation of the continuous-time convolution integral
$$y(t)=\int_{-\infty}^{\infty}x(\tau)h(t-\tau)d\tau$$
from the discrete-time convolution sum
$$y[n]=\sum_{k=-\infty}^{\infty}x[k]h[n-k]$$

The discrete sum makes sense to me conceptually- as sum of amplitudes, but an integral means area... which is where I start to get lost, at least intuitively.


texts: How to define the hysteresis of the buck-boost operation mode?

texts:
In the buck-boost (transition) operation mode of a four switch cascaded buck boost converter, there is supposed to be a hysteresis to prevent bouncing. How do we define the hysteresis in this case as the converter transitions to and from the buck mode and to and from the boost mode?

Reference: https://drive.google.com/file/d/1hNCPMCk6M6cA-ZtW7djiLBN-2hCyJhi4/view?usp=sharing
Please correct me if my understanding is incorrect, or there are gaps in my explanation. I would greatly appreciate any help you can provide. Thank you.


texts:
I need to do something and don't know how to tackle the problem.

I need to use optocoupler to turn on a pnp transistor which will be able to conduct relatively high current, theoretically speaking 400mA (probably a few time higher).

Supply voltage for higher voltage side will be 12V and 3.3V for LED side of the optocoupler. If I look at the datasheet of optocoupler I see:

and

First puzzle I need to solve is next:

Does this mean that at 10mA (If) current 150mA will be able to flow through CE if the supply is capable of outputing that current?

If so is CE voltage drop negligible?

Update:
Ok so now I know that I should give more attention to the graphs, but how to get appropriate IF value for desired Ic current is still a mystery to me.


texts: How to relate memory address to physical components in RAM?

texts:
I am trying to understand how are the micro-scale components arranged to relay address information to the Operating system software.

What are the components that make up the ram which actually contribute to the address?

Also, how many such components would a ... say 2GB RAM contain?

Edit: This answer seems to contain some useful material, please see if it is helpful in answering my question: https://electronics.stackexchange.com/a/132056/86531


texts:
Can anyone help me solve the equation for I-reference?
The final answer is given, but I don't know how it is obtained.
Thanks


texts:
I find it quite hard to find any information on how to deal with legal issues concerning the use of USB online. I mainly have two question I cannot seem to find a definitive answer to.

Is it required by law (US or any other country) to have a VID/PID combination that is registered with the USB-IF? If no, why would you still want to register one?
Is the trident logo free for usage without a Logo License Agreement (this logo does not appear in the logo usage guidelines)?

I tried to search myself using these sources but they offer no definitive answer:

https://www.usb.org/compliance
https://www.usb.org/logo-license
https://www.usb.org/sites/default/files/usb-if_logo_usage_guidelines_final_103019.pdf
https://www.eevblog.com/forum/projects/how-to-label-a-usb-port-(legal)/
https://www.quora.com/Who-designed-the-USB-symbol-Whats-the-story-behind-the-individual-or-group-who-designed-it-and-the-design-process-they-pursued


texts: Different AH 12v battery to battery bank OK?

texts: Can I safely add a 12V 200 AH AGM battery to a 12V 230 AH AGM battery (from different manufacturers) for a small solar system?


texts:
I need to connect a DAQ to an existing system which uses a DAQ. The idea is to connect the DAQs in parallel so the existing system is not changed. It is likely that only one DAQ will be used at a time. The DAQs will be configured to output a 0-10V signal. I believe this will be fine, but I'd appreciate any clarification.

Thus, I cannot interface with DAQ0, so can I introduce DAQ1 in parallel with DAQ0 without compromising the signal or either of the DAQs?

Would there be any benefit to keeping the systems isolated?


texts: How did the term "volume" come to be used for the control which adjusts loudness/intensity?

texts: It's a term we're all familiar with, but how did it come to be chosen as the name of the control which makes an audio output louder or quieter?


texts: Avoiding DC voltage drop over long distances

texts:
I am trying to power my IP camera over a long distance from the power socket (about 10m). The included power adapter, rated for 5V 2A is about 1.5m long.

I cut the cable and extended it using a thicker wire (to prevent voltage drop) but despite that the voltage drops to about 4.5V at the end. The camera does power on, but making any PTZ movements on the camera causes it to reboot.

Any solutions other than buying a new adapter? And if I do buy a new adapter, what the general rule of thumb for voltage drop across x meter of wire when supplying low DC voltage?


texts: What is the most suitable battery for an inverter?

texts: I was thinking about making a small inverter project but I don't know what type of batteries is most suitable for this application. Anyways, I know the capacity(20Ah) but i don't know what type do I choose.


texts: What is the breakdown voltage of vegetable oil?

texts:
I’ve done a little bit of research and I can’t find any source that has the voltage breakdown of plain vegetable oil.

Maybe I missed something somewhere but I could use some help on this. Or a different point of view.


texts:
Hello all. Thanks for the forum.
I have some of these: G4 bi pin LED bulbs. Silicone coated dimmable 12 volt DC. They are 1.5 W.
Although not visible on this photo, the pins are marked "C" to the left and "P" to the right, when viewed with the pins lower most. Eveything else about them appears identical.
Could anyone confirm which poles they signify?
Or are these bulbs not polarity dependent?
I am a novice. I have a 24/12 volt solar system and I am designing a small set of chandliers.


texts: Are commercially available common-mode chokes, such as one you'd pull out of a dead switching supply, suitable for DC service up to their rated current, or will they saturate/do other baleful things when subject to their rated current as DC instead of mains frequency AC?  Do they need to be derated at all for DC service?


texts: How does one implement the following function with these tools provided?

texts:
Suppose I have a function defined as follows, such that it is expressed in POS form,
with the product of the following max terms of 4 variables (A,B,C,D):

0,3,4,7,9,10,12,15

and I only have a 4 to 1 multiplexer, one inverter, and one 2-input gate of my choice.

What would be the approach going about solving a question like this? In addition, what
would be the "correct" 2-input gate to use in this situation?

My idea:

Crunch out all possible combinations of inputs then take all possible gates possible for those particular inputs:

(A,B)
(B,C)

etc.

However I feel that takes too long and a rather cumbersome approach to take.


texts: Resultant voltage function through two opposing coils with mutual inductance

texts:
So my question is about the type of relationship in a particular circuit.  I would like to know if it is linear or something else like a power.

The circuit in question is a pair of adjacent, mutually inductive coils placed in OPPOSITE directions, and the discharge of a capacitor through them.

simulate this circuit – Schematic created using CircuitLab

With an initial voltage on the capacitor, what would the voltage function look like at Point A? (linear, summation of logs, etc.) What would the voltage function look like if a turns ratio of something other than 1:1 was used? (a mathematical explanation would also be appreciated.)


texts: Using an AT Tiny to detect a specific voltage input and then drive an output

texts:
Design goals/Problem: I want to design/build a device that can detect a specific input voltage between 0-5 vdc (I'm not sure exactly what voltage yet, but let's just say it's 2.8 vdc as an example) and when it does, it provides a connection to ground for the control side of an automotive relay (something like this)
This relay has a coil with a 1.3w power rating. The device would operate in an automotive application, with the purpose of activating the coil side of the relay when the device senses 2.8 vdc on the input line. The device would operate on typical automotive electrical power (12-15 vdc). The relay will be used to control a high-power circuit (reverse lights). The input is a variable-voltage transmission range sensor (it outputs a different voltage between 0 and 5 vdc depending on what gear is selected - this is an existing sensor on the vehicle that provides a signal to an instrument cluster that shows what gear is selected - but I don't know the output voltage-to-gear matrix yet, gotta do some testing), so this device is basically a reverse-sensing device used to activate the reverse lights using a relay. The application is for my UTV (off-road vehicle).
My questions:

would it be possible to design this using only discrete components, and if so, how? I'm thinking it could, but option 2 below might be easier and more cost-effective.

what about using something like an AT-TINY 20 to accomplish this, or is this "overkill"? I imagine it could be programmed to detect the voltage easily enough and control the output (ground) for the relay using the GPIO pins, but I also imagine I would need some additional discrete components (MOSFET to control the ground side of the relay due to the current requirements of the relay coil - 1.3w, which at 12vdc nominal would be about 110ma if my ohm's law calculation is accurate), since I doubt the AT TINY can handle that much current sink to ground.

I'm just getting into electronics and trying to learn (I've picked up a myriad of development boards - an ardunio uno, Rpi zero w, BASYS3 FPGA board, and a few TI TIVA LaunchPads - to play with), so I'm unsure of how to reach my design goals for this device due to my lack of knowledge. My background is an an automotive technician, specializing in electronic engine/powertrain diagnostics and electrical diagnosis. I'm currently taking college classes for Engineering Technology as well.
I also realize that this could be accomplished with some type of switch on the shift linkage that operates the relay directly, but where's the challenge/fun in that? BORING.
Thoughts?


texts: Sub-Miniature version of the 12AU7 valve (vacuum tube)

texts:
I want to make my own valve amplifier, and for that, I'll be using an 12AU7 dual triode tube. Since the 12AU7 is quite large, is there a sub-miniature version available?

Also: the main difference between the European ECC82 and the American 12AU7 is the heater voltage of either 6.3V or 12.6V. I heard they can be both wired to use both voltages, could someone please explain how?


texts: Using an analogue multiplexer to control a motor controller?

texts:
I am designing a control circuit for a Sabertooth 2x60 motor controller. When this controller is in analog mode, it runs in full reverse (0v control signal) until my software starts and applies 2.5v to the signal pin. I have currently integrated a voltage divider and a relay circuit to apply 2.5v from a source independent of the computer (5v vin divided by two 47kOhm resistors) which works but I am hoping to get rid of the mechanical component (relay) if possible.

It has been a long time since I have worked with transistors and mosfets and was hoping if someone could assist me in the design and if there is an IC I can use? To recap requirements; Apply 2.5v from a voltage divider circuit until the software applies a 5v signal (Digital I/O) to the relay which then switches vout to use the analog output of my control software instead? There will be two analog inputs to my control circuit, one 2.5v from the voltage divider and one 0-5v from my software. Using a Hi/Lo pin, I want to select which input the circuit should output.

Thanks in advance for any assistance you can provide me :)


texts: Output Drift of an operational Integrator

texts:
R = 1k and C = 0.1 uF

In practice, the output of an operational amplifier integrator will (drift) until it saturates at a value close to one of the supply voltages, even when the input voltage (Vin = 0). Why does this happen?

How can we prevent the drifting?

I found the answers on Wikipedia but I couldn't analyse them logically.


texts: 5V Power out beaglebone blue doesn't work

texts:
I'm trying to understand why the power out 5V and 3.3V of my new beaglebone blue doesn't return 5V. The power out 3.3V seems to be the only enabled. As you can see on the pictures below the power out 5V return 0V. Is it a manufacturing issue?
Thanks


texts: Determining the frequency response of an audio crossover (something seems off)

texts:
I'm in the process of putting together an audio crossover. I finished assembling the components, and I though it would be neat to do a frequency sweep on the filters. When I inspected the tweeter filter, I got some weird results. I assume I somehow mis-wired something, so I decided to go through the math to figure out what I should be seeing.

In any case, here's the circuit (not my design):

simulate this circuit – Schematic created using CircuitLab

Below is my analysis of the filter in the S-domain (I hope I did my math right):

In any case, I threw this transfer function into MATLAB and it generated this Bode plot:

The phase plot is fine in my opinion, but the magnitude plot seems amiss. One, the magnitude of attenuation seems ridiculous, and two, there's no knee. From the circuit, it's obvious that it's a high-pass Chebyshev filter. It should be attenuating only the lower frequencies and letting the high frequencies through. So, it seems like I did something wrong? Is it my math or something else?


texts:
I am kinda new to the website, I just came across it after looking for answers for such a long time. I have an assignment that asks to add an input bit to your circuit from the circuit I created that goes up my sequence of 3 up to 15 called U (for up). If U is a 1, your circuit should count up through the sequence of multiples of 3 as normal. If U is a 0, your circuit should count down through the sequence of multiples of 3 (0, 15, 12, ..., 6, 3, 0, 15, 12...). I was able to draw the truth table and the K maps both for going up and down but I don't know how to implement the input circuit. For this assignment, we use a program called Logisim. Please let me know if extra information is needed

This is the counter going up

This is the counter going down


texts:
I have 70 turns of enameled copper coil, 1.25 mm diameter and 25.4 m in total.

I wound it on top of eacher and soaked the whole thing in a thermally conductive compound. What I fear is that by pulling the coils while winding them, I scraped some of the enamel away. I am not sure how resistant it is. That would cause some of the coils to come in contact with each other thus short circuiting the whole thing.

How can I check for this?

Should I see a fluctuating resistance on a multimeter? Is there any obvious tell?


texts: How can I successfully make a PCB at home?

texts:
I have tried several times, unsuccessfully, to manufacture a PCB at home. A lot of the other questions are about improving PCB performance and such, but I can rarely, if ever, even get the ink to adhere to the copper board. I even bought the special "blue" paper that I saw recommended several places.

What are some common gotchas that one might face when making a PCB? Specifically, I am having problems getting the ink to adhere to my board when I iron it. I have heard people briefly mention baking in the oven as an alternative.


texts: What set the speed in a cassette tape recorder?

texts: I was wondering what set the rotational speed in a cassette recorder?  I assume that the speed must be constant, but that means that the tape data would have different effective densities depending on where you were on the tape.   Was it a stepper motor and a timer to create the rotations or was something more interesting used?


texts: How does a transistor work when collector is disconnected?

texts:
My transistor works when its collector is disconnected. That is: The LED in the following circuit glows, albeit somewhat dimmer than when I connect the collector. (but it still glows considerably good)

simulate this circuit – Schematic created using CircuitLab

Is this normal? If yes, could you explain why is this happening?


texts:
I have a working stopwatch and I need to continue it so it will count up to 30 days, 12 months, and 9999 years but I am unsure of how to continue.
Here is a picture of my logisim file:


texts: TTL square wave inverter adjustable duty cycle

texts:
I am an amateur and I don't have experience with logic circuits so please forgive me if this is very simple.

I have a 5V TTL crystal oscillator (4-pin). I need to create a second square wave from it that is 180 degrees out of phase with the first wave. It would be optimal to be able to adjust the duty cycle of the waves. (Just to note - this will operate at up to 20MHz)

I know I can probably use an inverter, but I have never made 'logic' circuitry before.


texts:
I'm trying to do communicating an Arduino Mega to an Arduino Nano through RS485 protocol.

In this way, I'm using two MAX485 boards like this :

If I apply this wiring :

I get this signal :

As you can see, the signal output from A and B are same and a little distorded at the beginning.
Would you have an idea why ?

Regards


texts:
This query is related to my old post: ADC outputs random values to constant input

I made further tests, and still struggling. The reason I made a new post is, the query is different. I am using  FPGA (Spartan6) to sample the signal. The PMODS can handel a maximum of 3v3. I expected the output of ADC to be below as the input. Also with multimeter I get the same voltage level. But I found in the datasheet (http://www.ti.com/lit/ds/symlink/ads7822.pdf) Page 4 - DIGITAL INPUT / OUTPUT - Logic öevels: Voh = 3V5 (min). That means its from3V5 to 5V. Is my understanding clear?


texts:
I have seen optocoupler series with common cathode and resistor on every anode. My question is whether or not one resistor on the cathode side will be sufficient, with the right wattage, of course, and what is the reason behind these many resistors.

simulate this circuit – Schematic created using CircuitLab


texts: I'm intrested in doing somethings with FPGA's, but most sources lead to a hardware description language. I'm personally more interested in using something like http://www.simulator.io. Where you just plan your gates out thus being able to see what the gates look like. Is there anything like that which can be used in an FPGA board.


texts: Capacitor value for rectified magneto PSU

texts:
## Need capacitor value for below circuit ##

Hi guys,

Kindly help me with the situation below.

I want to run my LED headlamp (with upper & dipper functions) via flywheel magneto.

Current setup: 6v Magneto >> Headlight coil >> Headlight incandescent bulb 12v 35/35w (No regulator/rectifier).

New setup: 6v Magneto >> Headlight coil >> bridge rectifier(KBPC 3510) >> smoothing capacitor (unknown value) >> XL6009 step up booster >>LED headlight (9-30VDC 9 Watt).

Reference data:
->Magneto is of 6v & LED is of 12V. (9 to 30v)
->Magneto keep on changing the voltage as per RPM.
->AC current & frequency is unknown.
->No battery /battery coil is present.
->Full wave bridge rectifier is rated at 35 amps.
->Step up booster is rated at max 4 amps.
->Current withdrawn by LED is unknown.

Please help me to find a suitable smoothing capacitor or to re-arrange the mentioned connections.
Any other suggestions are also welcome.

Thanks.


texts: 2 mesh circuit giving me trouble. (steady-stade, mesh current method, dependent current source)

texts:
The task is to find Ic in phasor form.
The circuit is in steady sinusoidal state.

I used mesh current analysis and I got to that:

I have no idea how to keep going from there. Also the answer has been given as Ic = 0,5 - j0,5

Sorry if I don't use the terminology correctly. I can explain if needed.


texts: How can I make a motor stop when the output of a PIR sensor is below a threshold?

texts: I will attach a PIR sensor to a motor and i want the motor to stop turning when the output of the PIR sensor ( http://www.rapidonline.com/pdf/61-1466.pdf ) is below a threshold. I also want the motor to start turning again when it is above the threshold.


texts: How to determine the value of the variable resistor to land on saturation region?

texts:
I'm trying to determine the  Linear region of the transistor by setting an upper and lower limit for the resistor on the lower left hand corner. I've already fixed the lower limit and tried to find a value for upper limit by using: $$I_B+I_C=I_E$$
$$R_EI_E+R_CI_C = 15$$ $$\frac{15R_2}{R_2+10^5}-B_{BE} - I_ER_E =0$$  Clearly these set of equations ain't enough. Is there any way out ? or i'm fundamentally wrong?


texts: Will using a relay for triggering remote send interfering signals?

texts:
So I have a remote control with a SMD button I want to trigger. To do so, I need to bridge horizontally a pair of the pins, as shown in blue:

However, when testing this, I connected a long (10cm) cable. I had my headphones plugged in to the computer, and I heard weird high-pitched sound for as long as the pins were connected. The noise was not audible when I disconnected the headphones from the computer, or when taking the headphones out. The noise is not present when pressing the button usually with the headphones connected. What was this sound?
My question is: will I create interference or maybe change the tuning of the device if I use such a long cable to bridge the pins? I'm using a Raspberry Pi and a relay to trigger this button. The PCB remote board takes a 12V input while the Raspberry Pi is a 5V board, would using a transistor be safe and work better in terms of the interference? I'm new to electronics and would like to use the easiest, but most importantly the safest option.


texts:
This may seem a little dumbfounded but I asked someone if it was safe to use a 2.5mm - 3.5mm cable converter on both ends of a male 3.5mm cable, and they told me it was alright as long as it was a 3-pole plug. What exactly is a 3-pole plug? I'm trying to substitute a 2.5mm male to male cable for (2) 2.5mm to 3.5mm converters and a 3.5mm cable.

I'm sorry if this question isn't clear, I'm really not sure how to word something like this. Also I'm sorry if this is the wrong section (or website)


texts: Drive 10 piezo buzzer from micro controler simultaneously and independently

texts:
I'm looking for a solution to drive simultaneously 10 piezo buzzer from teensy. I'm aware about the limitations of the number of internal timers so I'm looking for an external chip that would enable the control of 10 piezzo buzzer independently and simultaneously.

I want to generate up to ten frequencies using piezo buzzers and a micro controller.

I see some I2C PWM drivers such as MAX7313 or PCA9685 but I'm not sure how they would act for piezzo such as the following: https://docs-emea.rs-online.com/webdocs/1581/0900766b815811a0.pdf

Any idea of a way to achieve that ?


texts: what's up with u-law companding when u is 0

texts:
https://www.tutorialspoint.com/principles_of_communication/principles_of_communication_modulation_techniques.htm

It says that I can get the compressed output of a signal using this:

it also says that there is no compression when u=0...
when I plug it in the formula it should give me back my input but instead I end up dividing 0 by 0...

can someone please help me understand why this has been a long running thing in data communication?


texts:
I'm currently studying Power Systems, and I stumbled upon "Inner voltage" I tried to search about it. However, very little is written about it. Could someone explain what it is?
Edit: Someone people wanted to know in what context this term is used. It's used in regards to synchronous machines and generators.


texts:
I have a weird but annoying problem. I have an inverting low pass filter as in the figure below:

simulate this circuit – Schematic created using CircuitLab

I want this circuit to act as a RL circuit and in simulations it does. So when giving 5V as an input I would expect to have -7.12V at the output, except that I don't. The output voltage decreases in the beginning as it should but once of a sudden it stops at -4.3V or so and decreases slowly but when I say slowly I mean 0.001V every second so not even remarkable. When I remove the capacitor everything is okay, I get my -7.12V so I suppose the problem has something to do with the capacitor.

Anyone experienced a similar problem or knows what's going on?

Thanks!


texts: Decrease the time it takes to transition from saturation to cutoff of a 2 terminal phototransistor?

texts:
Consider a two terminal phototransistor (collector and emitter) that is saturated and the light source is then removed.

What can one do to speed the transition from saturation to cutoff ?

Edit:

This question for some reason is being interpreted as homework (I'm not in school) and this question is being interpreted as if I am new the site (lol). So let me add some additional information that I didn't think was immediately relevant to the question.

For a BJT transistor, to get the device to go transition from saturation to cutoff faster, two things would need to be done. Prevent the device from getting into saturation and apply a negative voltage at the base. Both these items are done with the base terminal.

I do not know the underlying physics of a phototransitor, but given its symbol (resembles a BJT), light hits the base, goes through some photo electric effect and we get minority carries in the base, and the operation is similar to an NPN.

With that, the phototransistor being similar to a BJT, how can I make the phototransistor (that does not have a base terminal) turn off faster than just removing the light source - since I can't add a diode between base and collector and I can't apply a negative voltage to the base ?


texts:
I'm interested in developing a bespoke through-the-earth (TTE) radio transceiver for a measurement instrument in a limestone cave system.
The issue I have is that conventional RF signals cannot penetrate the surface due to the conductivity of the permeable material so I've turned to frequencies in the 30kHz to around 130kHz range (potentially higher, not sure how effective this would be as per current research).
The plan is to use ground spikes to inject current into the earth and for the conducting medium to serve as a channel for the signals to reach the transceiver underground, and vice versa.
My question is: As I aim to make this project as cost effective as possible, what do I need to consider when designing this hardware? Are there any existing RF modules (preferably for Arduino) that can produce signals at these frequencies directly through a home-made antenna across the ground, or do I have to build one myself? If so, how would I go about designing such a module?
I'm not interested in transmitting audio or video from the cave, only .CSV files via MySQL. I've already identified the need for a GSM module to transmit the data from the surface to an online server for remote data collection purposes - the main issue is the data transmission between the transceivers. Attached is a diagram summarising a similar system given to me by a developer of a TTE radio system.
Any help would be greatly appreciated, even if just in the form of a nudge towards some appropriate sources.


texts: Can't figure out the general formula for electric circuit

texts:
I have the following setup. Note the device in the middle says P, not R, so I now how many Watts the device produces. (I'm not sure if I drew the correct symbol there)

Calculating the current resolves to a quadratic equation, which I can solve:

This gives 2 values for I, one of which will result in negative values (right?) and can be discarded.
Now, when I add another device (and then another and another), it becomes too complicated for me:

I figure there must be some general formula that I can plug into the previous one at each step.
The ultimate goal is to figure out how many devices can be added before the voltage becomes too low, considering each P and the lengths of the wires (which is what R1, R2, etc represents) Can someone figure this out?

Update:
As it turns out, working backwards is extremely easy, e.g. asking the question: "If I need a minimum of v Volts over the last device, what does \$V_0\$ need to be?" It's just a matter of adding voltages and currents.
Working forwards in the way I imagined is not doable, e.g. asking the question: "If \$V_0\$ = v Volts, what is the voltage over the last device?" This can be done with iteration.

Everyone keeps saying the voltage drop from the wires doesn't matter, but it does. With 25W devices, depending on the number of devices we hook up and lengths of wires (which can be hundreds of meters), we can get voltage drops from the wires that are over 10% of the voltage drops from the devices. 2 or 3 Volts per wire is significant in our situation.
Thnx for your help, everyone!


texts: How to power multiple amps with one transformer?

texts:
I am building a 4 channel power amp. Each needs 2 x 25-30 VAC/ 100-120 VA. My plan is to use a single transformer and wire them all parallel. Would a 2 x 30 V/400 VA transformer do the trick?

I'm a total novice and want to avoid any disasters.


texts:
I would like to design an earth resistivity meter for use in archaeological surveying. This is essentially a current source placed in the ground and a ohmmeter to measure the resistance between the probes. This tells us something of the composition and moisture content of the soil, and whether there might be archaeological features beneath the topsoil.

An example of a commercial "res meter" is the Geoscan RM15-D, and John Becker wrote an article in Everyday Practical Electronics about 20 years ago with a design for one. The drawback with that one is it uses +/-5v on the probes which limits its usefulness in dry or very rocky soils. The Geoscan machine can output at either 40v or 100v (peak-to-peak I think) which makes it
a more versatile device. An AC-coupled waveform is needed to reduce the capacitive effects of the soil.

So what I would like to design is a circuit that gets me somewhere near the specification of the RM15-D:

up to 100v p-p AC at <150Hz at a user-selectable constant current of 0.1mA to 10mA
powered by a rechargeable LiPo/Li-ion battery
be as lightweight as possible because frail archaeologists need to lug this thing around bramble patches all day

The circuit in the article uses a simple pulse train as its output waveform, and while the actual waveform shape doesn't appear to matter a great deal (as long as it is AC coupled), the potential for very high transient voltages seems to me undesirable. Assume for the purposes of this that I can generate a low voltage sine wave to be fed into the circuit. Presumably some amount of isolation will be needed as well.

What would be the recommended way of achieving this? Would using something as simple as a transformer be sufficient, or perhaps something like a DRV2700 as has been mentioned in this SE question?


texts: Oscilloscope ground and unit under test ground issue

texts:
I am working with an instrument which has a supply of 230V AC or 400V DC. AC source is isolated at the input via 1:1 transformer and DC source is a floating supply.

I have a Yokogowa DL1620 oscilloscope. The power cord of scope does not have an earth pin. So my question is: I know unit under test shall be isolated always as I done however, can I work on an isolated unit with unearthed scope?

Also if scope is earthed then "ground" of unit under test will be at 0V. Is it desirable?


texts: I was reading about debuging the code for ARM Cortex-M based MCUs. Moreover, I read about ARM Debug Interface, so What is ARM Debug Interface?


texts: How can we visualize the lag between voltage and current in capacitor or inductor? i.e. When voltage goes down Current goes up...

texts: Its hard to imagine the scenario and contradicts basic understanding.


texts:
There are plenty of I/Q modulators produced, how can I learn theirs sample rate(bit rate) from datasheets. There are only LO frequencies and sometimes baseband frequency there.
For instance


texts: What to do with USB power and ground when you have an external power supply?

texts:
I have a externally powered USB device.  (It's actually my old VIC-20 computer, sort of)

USB data is handled by an ATTiny85.  The USB interface is based upon the V-USB easylogger.  The ATTiny85 receives inputs from the VIC-20 on three of it's pins and is powered by the VIC's power supply.

My question is, do I need to worry about the VBUS line at all if I'm getting my +5v from another supply?

Also, I'm currently sharing grounds between the USB, ATTiny and VIC-20.  Is that a possible problem?

Here's the USB portion of my schematic.


texts: Why are both bias resistors considered parallel in a common emitter amplifier?

texts: When calculating the input impedance of a voltage divider biased BJT common emitter amplifier, we calculate the parallel resistance of the bias resistors and the emitter resistance. But why do we consider both bias resistors? Looking from the amplifier input (the transistor base), the other resistor leads to the voltage source, while the other leads to ground. Shouldn't we only consider the one that leads to ground? Why would any of the input current go to the voltage source/battery?


texts: What is the function of the capacitor in this circuit?

texts:
I was reading on the internet about reading the remaining voltage level of a battery operated device using an ADC. This circuit is designed so that the ADC is only used when it is needed to be used, rather than it constantly draining the battery.

However, I do not understand what R3 and C1 are used for. I'm guessing it's some kind of MOSFET driver, but I am not sure.

Could someone help me to understand what they are for?
Thanks


texts:
I have a 90 V motor I'm testing on a bike. I ran it with two Bosch corldess 18 V batteries in series. With 18 volts it ran about 10 miles per hour. With 36 volts (both batteries together) about 20 miles per hour.
I have two 14 volt batteries from another power tool set and I'd like to connect them together in series to bring it up to 64 volts. Can I do that? I want to test it first to see if it's about what I want for the speed before I buy my permanent battery.

Can I connect 18 volt and 14.4 volt batteries together in series?


texts: Raspberry Pi Zero - Male pad or connector for underside contact pads?

texts:
I got an idea after reading this hackaday article

http://hackaday.com/2015/11/28/first-raspberry-pi-zero-hack-piggy-back-wifi/

that I could make a daughter board to sit under the Pi Zero and have some form of contact to preclude the need for soldering to the Pi Zero.  I found this EE SE article

interface component for screwing to make electric contact

that has a good part (Spring Loaded Headers), but it seems to be several dollars a piece, so that defeats the point of the Raspberry Pi Zero.

Is there another or different type of connector that I could use in this circumstance?  A sort of male pad for an under daughter board?


texts: How is the energy consumption of a ciruit component calculated?

texts:
I know that watts are equal to amps times volts, and that watts are a rate of energy consumtion. I have looked at some circuits, but I am unsure of how the total energy use is being distributed. My guess—correct me if I’m wrong—is that the energy used by a component is the voltage across the component times the amps through it. Since the volts add up to the power source voltage, this maintains the total amount of watts.

No amps through something, no energy being moved.
No volts across something, no pressure difference is necessary to traverse it.

Does this mean that a resistor is not just slowing the flow, but turning the energy into heat?
An inductor that is “charged up” and has little resistance is not using any energy because there is no voltage across it, even though there are many amps?
The vast energy loss in a short is in the existing resistance, the battery/power source?

I always imagined (but knew better) that less resistance should be easier. Perhaps it is; the wire is hardly drawing anything. But is the resistance in the source?

One last thing, maybe a bit off topic: is it easier to turn a generator connected to an open circuit than a closed one simply because no energy can be transferred? A water pump would get harder in that scenario. (In terms of work, less energy would be used if I am always applying the same pressure to the crank. It wouldn’t move, so no work.)


texts: Suggestions to upgrade this PWM AC circuit to handle 3000w

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I'm planning on building a circuit that can "phase control" the AC signal to lower the power supplied to my hot water element. The goal is to lower the power in line with my PV generated in near real time.

The element is 240v 2400w.

I purchased a triac based dimmer but I feel it's not the correct/most elegant solution due to noise created by chopping the wave.

I came across some high-frequency PWM solutions using IGBT or Mosfet but they seem to be switching smaller loads (100w-500w bulbs) or the components listed don't leave any headroom for my 2400w element.

The detailed description can be found here on instructables: AC-PWM-Dimmer-for-Arduino

I would like some help upgrading the components to handle such loads:

Suggested Optocoupler 4N35 (No need to upgrade)

Suggested mosfet is STP10NK60 (10a - leaves no headroom)

Suggested IGBT IRGPC40 (obsolete)

My suggested upgrade would be IRG4PC50UD (VCES = 600V @VGE = 15V, IC = 27A)
with a large heatsink.

Am I missing anything here, could anyone suggest a better component?

Could anyone also shed any light on filtering any high-frequency noise on the line if there is any?

I couldn't find any off the shelf pre-made circuit board, which I found strange - everything used the old triac method or slow PWM.


texts:
I was studying a Texas Instrument reference board and would like to understand some topologies and PCB routing techniques. The project is a 230-V, 3.5-kW PFC with >98% Efficiency.

Here's the complete project page where you can download the CAD files: TIDA-00779 CAD Files.

I would like to start asking what are the reasons for using these marks on the bottom solder layer?

If anyone observes another interesting feature or technique used in the design of this board, please share with us.

Thank you.


texts: I'm using an Arduino Blend Micro with outputs that provide only 3.3V and I need to control a MOSFET that needs 5V on its gate. Can I step up the voltage from 3.3V to 5V using a single BJT?


texts:
How do you calculate the actual power dissipation across the resistor in an RC circuit?
For instance, 12 V source, 10 Ohm resistor in series with 100 uF capacitor, no other load connected.
12/10 = 1.2A x 12V = 12 Watts (This calculator says 14.4).
But only for 4 milliseconds.
I tried a 0.5 Watt 10 Ohm resistor with 300 uF and 12V supply and the resistor didn't even get warm, so I assume the power dissipation is very small. But I'd like to calculate for other source voltages, resistors, capacitors.
Is there a simple way to calculate the RMS power dissipation per this partial answer: RC Network resistor power rating with DC supply


texts:
i bought this transformer to use in a power supply http://www.dhwelectronics.com/Safety_Isolating_019000600020/P028_1A_Secondary_30VA_Transformer_With_15015_Vac_Ouputs/
i want to have two outputs but as there is only three wires was wondering do i have to cut into the transformer to add a fourth wire or can i solder that wire onto the strip board and then branch a wire off from there ?


texts: Unstable Phase of Channel Impulse Response

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I'm using DW1000 UWB radio transceiver and extract its channel impulse response (CIR). The CIR output by the transceiver is the complex baseband CIR. In a static environment, the CIR is a LTI filter expressed as
$$ h_b(\tau) = \sum\limits_{i} a_i^b \cdot \delta(\tau-\tau_i) $$
where
$$ a_i^b = a_ie^{-j2 {\pi} f_c \tau_i} $$
\$ i \$ is the index of (multi-) paths. \$ a_i \$ is the (complex) scaling factor including distance, antenna gains, etc. \$ f_c\$ is the carrier frequency. \$ \tau_i \$ is the time delay due of path \$ i \$.
What I'd like to have is the phase of the direct path. Let direct path have index \$ i=0 \$, the phase is then \$ a_i e^{-j2 {\pi} f_c \tau_0} \$. Since the direct path is the shortest, i.e. \$ \tau_0 < \tau_j, \forall j \ne 0\$, if I take the phase of the first peak in the CIR, I would get the phase of direct path.
So I have two DW1000 transceivers, one Tx and one Rx (whose local oscillators are not synchronized), keep everything static, and take multiple CIR measurements from the Rx. However, the first peak CIR phase varies quite a bit from one measurement to another (it even seems changing randomly). I understand carrier frequency offset (CFO) might be causing this, and tried a technique to eliminate it but with no luck. So I'd like to ask if there's any other potential reason for the unstable phase?
Since I'm still learning about RF systems, an explanation from up/down-conversion and channel estimation point of view is greatly appreciated!
In the figure below, x-axis is the first peak phase of n-th CIR and y-axis is phase.
Thank you!


texts: Analysis of diode biasing in the given bridge connection of four diodes

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How does the output voltage change when Vs is varied from -10 V to + 10 V in the given circuit?

Given: Vs is input voltage, Voltage at 【A】is the output voltage; all diodes are identical with cutin voltage = 0.7V

PS: TP1 is just an scope which can be ignored in this case.


texts: Multiplexer and feed-forward equalization capable line driver

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Starting this project, on multiplexer and feed-forward equalization capable line driver.
Would this be a good implementation for the pre-drivers and drivers or maybe a CML implementation would be more suitable.
The input going into the gates are pulses 0's and 1's (0V and 3.3V) coming from the XOR, with duration of 100ns.

Using this paper : https://www.researchgate.net/publication/2983309_A_10-Gbs_5-tap_DFE4-tap_FFE_transceiver_in_90-nm_CMOS_technology?enrichId=rgreq-17506414a2d1e8134110047e9d8aaa56-XXX&enrichSource=Y292ZXJQYWdlOzI5ODMzMDk7QVM6MTAxMDYzOTEwNzU2MzYxQDE0MDExMDY5MjI4MjU%3D&el=1_x_3&_esc=publicationCoverPdf


texts: MOSFET relay connections to control a 3V motor

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I need to turn a 1A, 3V motor on and off with a touch switch.  I bought Omron 653-G3VM-61-AR and quickly smoked it.  I had the battery + connected thru a 300 Ohm resistor to the touch switch (to get the current down to 10mA) then to one terminal of my MOSFET, grounding the other terminal on the same side to ground.  I connected the same battery + to the terminal of the Mofset with the dot by it, the other terminal to the motor then to ground.  Obviously this is incorrect.

I can't afford to keep smoking these $20 components, so any help you can give me will be appreciated.  The side that I hooked the control current to was the side with the transistors, the side I hooked the load to seems to be the "coil" side, by Omron's schematic.

Obviously I know little to nothing about electronics, so I need all the help I can get.


texts:
First of all, please see my other question HERE as it is related (Any help with that is greatly appreciated too).

If you read through my other question, you will know that I am attempting to interface with a magnetic sensor IC, the MLX90393, on the Sparkfun Breakout Board.

I have been having trouble reading the data from it, and I am confident the issue is in the code, not any of the hardware. The reason for this, is when I use the ARDUINO EXAMPLE CODE on GitHub, with the Arduino IDE (still using the STM32 Nucleo hardware), everything works and I can read the data from the sensor. However, when I attempted to convert that code over to mbed, I just get an error, and I am unable to extract the data.

I have now decided to see what would happen when trying to do a scan to find the address. Previoulsy, when doing an I2C scan in the mbed IDE, I got an ACK from every single address. The code I used was HERE. When running this code, this is the response I got:

Please note I added an additional \n after "I2C device found at...." so that it didn't scroll across the screen. Please note I have tried it with Error ==0 and 1. When I use Error ==0 for mbed, I get 'No devices found'

This is almost an exact copy of the Arduino I2C scanner, which can be found HERE. Looking through the 2 of them, they are basically exactly the same, and I cannot find the difference between them (bear in mind this is my first time working with I2C). When I run this code on the same hardware but via the Arduino IDE, this is what I get:

Does anyone have any idea why this is happening? What is the difference between doing this with the Arduino IDE and the mbed? I hope solving this issue may assist in solving the issue with my other question, but this is really getting frustrating. I have tried changing I2C pullups to different values and that had no effect either.


texts: More than three nested parametric sweeps in LTspice

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I have an LCR circuit including voltage sources where I need to sweep more than three parameters (nested sweep) for a transient simulation. I need to try a large number of different combinations of parameter values (I have 5 parameters, each of them can take anywhere from 3 to 10 values, for a total number of combinations up to 5000). Once the simulation stops, I need to use cursors in Probe to figure out which combination of parameters generates close to a a certain result. I cannot use Monte Carlo since the cursor information is missing (i.e. which parameter combination corresponds with which waveform). Besides, the Monte Carlo will take too long and it may 'duplicate' some combinations.
Is there a trick I can use to overcome the 'up to three nested loops' limitation?


texts:
Assuming I have a brushless DC motor which externally exposes only a + and - terminal. (I.e. I do not have access to the windings and hall sensor directly.)

Is there a way to control the speed? With a brushed DC motor one could just reduce the supply voltage.

Am I correct in assuming that this is not really an option for a brushless DC motor that will give a lot of range? I am thinking that most likely the internal commutation control circuit is powered using a voltage divider: if one reduced the supply voltage, the internal control circuit would experience low voltage dropout, right?


texts: How does a telephone hybrid transformer work?

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Suppose the following circuit:

I can see how an incoming signal (Kim's voice) wouldn't be coupled with the lower pair, but I can't see how an outgoing signal (Ron's voice) only goes through the lower pair.

When the signal from the upper pair reaches the hybrid then one part of it goes to the 2 wire telephone line (seeing a line impedance of Z1) and the other part (right inner inductors) does the same except it will 180° out of phase when it reaches the lower pair (because the impedance Z0 perfectly matches Z1). As such Kim's voice won't travel back.

On the other hand, I don't understand how a signal coming from the left phone would only travel through the lower pair.


texts: Setting up STM32 to sample 50/60 Hz Signal

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I'm setting up this ADC triggered each ms with a timer interrupt, or 1 kHz sampling frequency to read a 50/60 Hz AC signal and calculate its RMS with 1% accuracy. Also I'm using DMA. The AC signal will swing around 1.65V or Vcc/2 to avoid the negative cycle enter the ADC. I have another ADC channel to track another variable. I have the following questions for the AC signal sampling:

I need to find the RMS in a single cycle of the AC signal (20 ms or 16.67 ms). Is 1 kHz enough? This mean that for 50Hz I will take 20 samples per cycle and for 60 Hz 16 samples. So I need to fill the DMA buffer with these few samples.
How do I choose the sampling time? I could choose between 1.5 and 160.5 cycles. I chose 160.5 as the signal is slow but I'm not sure.

A little pseudo code would be:

Fill DMA Buffer with the samples
Subtract DC offset from each sample or pass the filter through a high pass filter
Take the filtered buffer and calculate RMS


texts: Why won't a switching transistor work in this circuit

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I've been working with an Arduino lately, and building various breadboard circuits.

A simple example was to build a transistor based inverter for a project involving 9600 baud serial combination at 5v. (I could do it with a quad NOR gate, but that is a 14 pin DIP package that needs 12 wires connected (when you include tying unused inputs to ground. That takes a lot of room on my breadboard and a lot of time to set up. I understand that a "real" CMOS inverter is a better choice for this application, but bear with me.)

I built an inverter based on this thread:

How to invert a digital signal

The circuit looks like this:

If I use r2 = 100k ohms and r1 at 3.3k ohms, it works, when using a general purpose NPN transistor like a 2222A or a CP9014. If I use a "switching" NPN transistor like a C1740, however, it doesn't work.

What is it about switching transistors that makes them unsuitable for a circuit like this? I thought switching transistors were tuned for very "snappy" response that tends to be either fully on or fully off. I would think a switching transistor would be a BETTER choice for this circuit, since I want it to be either fully on or fully off.


texts:
I am projecting a brushless motor driver that contains a LoRa SX1276 radio and a ESP32-D0WDQ6 chip. The power line then gets really noisy when everything is working.
For the RF blocks (SX1276 and ESP32), it needs to be very clean at the 3.3v fixed voltage. There are some power signals on the board, so that the image bellow shows the power tree with it's loads on each branch:

That being said, I have some questions:

Is there any problem on using the same LDO(ADM7172) to power both the analog chip lines (i.e. ESP32 and SX1276)? This LDO is going to be used exclusively to these two chips, as it's shown above.
The digital blocks from ESP32 and SX1276 are going to be powered by the "green-one" LDO line, on the diagram above. Add to this, the IMU and the DRV motor driver. Despite this LDO is 1A capable, it is recommended to power multiple ICs with one LDO? The noisy around this configuration is acceptable? (Bellow, the schematics:)

How GPIOs affect the LDO stability in order to not disturb other chips? Considering the fact that some chips have GPIOs and SPI pins to communicate with the microcontroller, how to prevent oscillations on that LDO that powers the ICs?

Basically my doubts are about how to stabilize the digital and the analog circuitry and when to divide the source of power between this two parts, or even when use the same LDO to power all this pins.
I hope you can give me some ideas, and thanks you guys for sharing the knowledge!!


texts: High Voltage DC - Shunt Resistor, Voltage Regulator Question

texts:
I'm a newbie here but was trying to wire a setup and was running into some issues attempting to calculate my required resistance, and resistor tolerance to current.

I have a power supply that brings in a range of voltage,
between [60 to 110]VDC @ [ 4.89Amps and approx 510 - 550watts ]

I'm trying to add a [ Shunt Resistor, Voltage Regulator, Voltage Stabilizer, Something?? ] in place to either drop 10 Volts from the power input, or a range where I can adjust the voltage coming in between dropping anywhere from 0 to 10 Volts.

The reason I'm attempting this is because I have a board that requires < 100 VDC to run properly, and I would like the ability to either switch on a regulator/shunt in the route (when necessary).

ie

Voutmax =  100V   <- what I've got
Vin = 60-110 V.   <- What I want

I tried calculating ohm resistance and I believe I wound up with something like,
100K Ohm resistance for a voltage regulator?
and something like...
1.03 to 1.1 Ohm resistance on a 100amp shunt resistor?

Honestly really a bit confused still and just trying to find the most direct way to regulate or drop those 10 Volts from my input line.


texts: Negative Charge Pump- How to analyze this?

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I am using CMOS 4069 inverter and wired up this circuit. I want to generate a \$-V_{dd}\$ negative pulse and \$2V_{dd}\$ positive pulse. The circuit above is for the negative voltage. However, I get really low negative voltage. In the analysis of the circuit, I couldn't get about the on-off regions of the mosfet when the square wave is sent. Could anyone help me with the analysis?
Another small question - shouldn't \$V_A\$ and \$V_B\$ be negative for the MOSFETs to be in ON-region? Thank you.


texts: Understanding the operation of a soil moisture measurement circuit

texts: I have a circuit that measures soil moisture but I am not able to understand how it works. Should we use copper plates or probes in the circuit? Is the circuit measuring the capacitance or resistance between the probes?


texts:
I'm working on a project that utilizes an array of IR sensors and recievers to map objects directly in front of it. This is similar to the various interactive coffee table setups that light an LED when something is close to it (via reflection of the IR light).

Now, I'm creating this array and putting it directly underneath a sheet of acrylic (or some other opaque material), so that when something is directly on top of the sheet it will pick it up. This makes the design easier, because my working range for the sensors is small and short (like 1 cm).

With that being said, I'm trying to figure out which IR emitters and sensors to use that will efficiently achieve this. I've been looking at SMDs because size is a factor, and I was hoping to use this emitter and this sensor, but I have some concerns.

This emitter is small and considerably weaker than those used in other emitters used in sensors (like the TCRT5000), and I don't even know how to compare the phototransistors, but given the very small range and somewhat controlled conditions, I was hoping it would work well to not only save space but to limit the noise of everything not directly on top of the acrylic.

I just need to know if this setup could work so that I can order them and start testing them, but if I'm not even close I'd rather try something else. If anyone has any tips for choosing these emitters and sensors, that would be great.


texts: On page 10 in the this article there is an example of time measurement with AVR. Is the same thing possible to do with this?


texts:
I am a software engineer and have limited knowledge of electronics.  I am using a Raspberry PI to control a AD5360 ADC eval board (http://www.analog.com/en/products/digital-to-analog-converters/da-converters/ad5360.html#product-overview).

I need to attenuate +-5 volt output form the DAC to +-50 Microvolts on 16 independent channels.

I am thinking that I need an on chip attenuator.  I am still prototyping so and part needs to be used on a bread board or with pins that can be soldered to a solder board.  I need a fast response time because I change voltage on each of the 16 channels between 256 to 2048 time each second, and a high level of precision.  If required I could build them, however because I need 16 I would prefer to buy them.  I have tried to use a simple voltage divider however, this introduces too much variance at the microvolt range.

I am open to other ideas if they can solve the problem more efficiently or are more cost effective.


texts: Can this push pull oscillator improved for experimental realization?

texts:
I am using the following push pull oscillator circuit  is extracted from this Application Note for implementation of a wireless charging system. In simulations, it's efficiency is above above 85% when coupling is 0.1. (I used parasitic resistances of L1 and L2 as 15mOhm which is realistic value for coils made using litz wires. The efficiency of this is highly determined by the coil quality factor - I want to exclude this in answers)

MY questions are:

How can I improve this oscillator circuit (not the Wireless Power System parameters )  in terms of efficiency, reliability or any other practical issues? - is there any better componet selection or better drive circuit?
Can we use this topology for high frequencies, for example, at 1 MHz? If possible, how can we improve it to use at high frequencies? If not, do we have any other oscillator topology  suitable for high frequency operation?

I also want to stick into a self oscillating circuit- I understand that pulse control topologies  like h-bridge conver or class E can be high efficient but for this application, I want to exclude them.


texts: Trying to make a current source with an XRP29302 (linear regulator)

texts:
I'm familiar with the configuration to make an LM317 (voltage regulator) into a current source.  You connect a resistor between the Vout and Adj pins (Say 1.24 ohms) and draw the output directly from the adjust line (not the Vout line).  With that resistance, you get a constant output current of about 1 amp.  Easy peasy.

I'm trying to do that with an XRP29302.  They are also linear regulators, but with some added bells and whistles.  Instead of the 3 pins of the LM317 (Vin, Adj, Vout), it has 5 (Vin, Enable, Adj, Vout, Gnd).   I tried hooking it up in a similar way, but it seems to be no go. (It works somewhat, but the output current is far too low.) I don't know what I am doing wrong.  I think I have to incorporate the gnd in an appropriate way, but not sure how.

Some LM317 info is here:   http://en.wikipedia.org/wiki/LM317

Some XRP29302 info can be found here:  http://www.datasheetdir.com/XRP29302+LDO-Regulators


texts: Is there a reliable way to read an in-circuit capacitor?  I have a PCB-type ESR meter with a zero-force insertion socket that works for components, but do not have a meter that was designed to read specifically capacitors embedded in a circuit.


texts:
For the below circuit according to Ohm's law the led will get 23mA.

What happens if the resistance is removed? How many amperes will the LED get? My assumption is that the wire has some kind of resistance as well...but how much ?

Thanks


texts:
I am using a GPS device. I'm told it's a WD-G-ZX4120, but on the actual device it says it's an ET-318. I heard from somewhere that this device uses 100 to 150mA. However the datasheets seem to say that it uses only a maximum of 42mA. So how much does it actually use?

Here is the datasheet for the WD-G-ZX4120, and here is the datasheet for the ET-318. Are these the same thing?


texts: Level shifting 5V signal to 3.3V using voltage divider where source has 10k resistor to ground

texts:
I made a circuit to read from a dust sensor that operates with a 5V rail. The microcontroller I am using is supplied with a 3.3V rail, and it shares the same ground as the dust sensor.

As the output of the dust sensor is an op-amp with low source impedance, I thought I could shift the level of the sensor output to interface with the microcontroller with simply a 2:1 voltage divider, but this does not work well. I did not realise when I designed the board that the sensor has a 10k resistor to ground on the output of its op-amp (shown as "0-5V signal"):

simulate this circuit – Schematic created using CircuitLab

The dust sensor's signal should smoothly vary between 5V and 0V depending on the air quality. With the above setup, the signal either jumps between around 1.7V and 0.3V with almost no transition in between.

Is there a way to compensate my voltage divider values in the presence of this resistor, such that the 0-5V signal is still translated to within the 0-3.3V range?

The dust sensor is a Shinyei PPD42NS. The circuit diagram can be found here.


texts: Current waveform in an inductor with AC source

texts:
If we connect an AC source with a pure inductor when AC source is going through 0 volts we get the following graph of the voltage and current.

There are few things in the graph about which i am confused.

In the first graph/diagram "A" of the picture which shows the voltage when it starts to flow and the corresponding current, the current doesnt seem to be lagging behind the voltage by 90 degrees. What is the reason behind that? Is the statement "current lags behind the voltage in an inductor BY 90 degree" is valid just for the steady state voltage shown in graph "B"?

Second confusion is that for the first half cycle of the voltage in graph "A", current is rising both for increasing and decreasing voltage. How is this possible that current is rising in the inductor for both increasing and decreasing voltage?


texts: What is the maximum voltage permitted when MOC3061 is "on"?

texts:
First, I am not an engineer,im a hobbyist.
I recently talked in a forum thread about (off-state output terminal voltage) in optocouplers.

A very good analogy was made between this off-state terminal voltage and Vce max of a BJT or Vds max of a MOS. Then I question about Voltage across MOC3061 optocuplor pins must not exceed 600V in the "off" state. Here is a direct link to this component if you feel is important: https://pdf1.alldatasheet.com/datasheet-pdf/view/53872/FAIRCHILD/MOC3061/+_3JJ4UwYhRDpKxHeyUKwvhw+/datasheet.pdf

-Mister NoiseEngineer had give me a splendid answer about this problem i had.
I summarized what i understood from him here, and also i come with an additional question still related to this case: -When the junction is closed (not current activated), its practically a big resistance in circuit, that supports maximum up to 600V in this case to not get damaged. But what if the junction is "on"(it's Gate/Base is open) and the same 600V are applied? Is the same thing as when is in "off" mode? It's the resistivity of the metals + some conductivity in play? Then i should ask, what is the maximum voltage permitted when is "on" ? Still 600V maxim (in this case) or greater(because of conductivity)?

--Thank you--


texts: Current in \$R{_1}\$ of resistor divider with capacitor

texts:
Given the system calculate the current in \$R_{1}\$, $$R_{1}=R_{2}=10k\Omega $$ and $$C=1.2\mu F$$. Well, I have two approaches.

When the capacitor is fully charged, it will open the circuit and there will be a voltage divisor

So $$V_{R_{1}}=20_V\frac{10k\Omega}{20k\Omega}=10_V$$
and then
$$I_{R{1}}=\frac{10_V}{10k\Omega}=1mA$$

Model the system, calculate the step response and you will have the capacitor voltage, so $$V_{C}=V_{R_2}$$ and then $$V_{R1}=V-V_{C}$$
System model:
$$\frac{V(t)}{R_{1}C}=\dot{V_{C}}+\frac{1}{C}(\frac{R_1+R_2}{R_1R_2})V_{C}$$
the time constant:
$$\tau=C(\frac{R_1R_2}{R_1+R_2})=0.006s$$
taking the Laplace transform with the input given and aplying the values of the components
$$1666.6\frac{1}{s}=V_{C(s)}-V_{C(0)}+166.6V_{C(s)}$$
Grouping, calculating the partial fractions expansion and taking the inverse Laplace transform:
$$\frac{1666.6}{s(s+166.6)}=V_{C(s)}$$
$$V_{C}=\frac{10.0036}{s}+\frac{-10.0036}{s+166.6}=10.0036-10.0036e^{-166.6t}$$ with $$t\geq0$$ and when
$$\underset{t\rightarrow\infty}{\lim V_{C}}=10.0036V$$ then (again)  $$V_{R1}=V-V_{C}$$
$$V_{R1}=20V-10.0036V=9.9964V$$
$$I_{R{1}}=\frac{9.9964_V}{10k\Omega}=0.00099964A$$ or $$I_{R{1}}\approx1mA$$

I made a graphic of the response.
OK, hope this can be reviewed and point any error or comment if this is done right! Thanks in advance.


texts: I want to connect 4 push buttons using interrupts on all of them, with my atmega328p, but when i read the datasheet, I found that the atmega328p had only 2 external interrupts ( INT0 and INT1), are there any solutions?


texts: What Load impedance to use for LC Filter before transformer?

texts:
I have an inverter circuit in which I want to filter the output with an LC filter. Lets say the fundamental component that I want is 60Hz.

When designing a Low Pass LC filter, I need to use the load impedance. In this case it is 100 Ohms and it is placed on the high side of a transformer. The LC filter will be on the low side of the transformer.

Do I use the impedance value from the high side in my LC Low pass calculations or do I have to use the equivalent impedance that would be seen on the low side for the LC low pass calculations?

Shown below is an example circuit.


texts: Designing flyback converter - wire selection

texts:
Some guides suggest using multiple very thin strands in parallel to "reduce the skin depth". Does this make any real difference?

When I apply their formulas I end up with something like 14x31SWG, which is rather a lot of headache to wind. Obviously for industrial design every watt counts, but for hobby is it OK to use single wire of appropriate diameter?


texts: Is it possible to connect D- and D+ to an existing USB to FTDI connection?

texts:
This maybe a noob question. I already have an ftdi connection on my board, using an FT232 RL connected to a micro USB.

But, the pic i'm using PIC32MX470F512L has D- and D+ for USB interface. Can i connect it directly to the existing connection of - and + of USB? I know i can use 0 ohm resistance / switch for the signal to go to FTDI or the USB pins of PIC. But would it work? Will it damage anything?


texts: How do I desolder these specific points?

texts:
I'm currently attempting to replace some bloated caps on an old PC motherboard but am currently having problems with some specific points.

Here's a pic of the motherboard:
.

The area outlined in fuchsia are the series of caps I am trying to desolder. Notice they are in pairs of square and round solder points. The round solder points are no problem to desolder. It's the square ones that won't desolder. No matter how much I heat them up, the solder on the points just won't melt and so I can't pull the caps off!

Is there a special technique or tool I need to perform this task?

Thanks in advance for any help you can provide.


texts:
I have a lot of 5v 400mah to 2a adaptors laying around.
Is it possible to use this on an old camera with input 6v 6.4w?
The battery is out of the camera and the power would only go thru the camera and not the battery.
If this makes a difference.

I read something on step-up converters but don't really know how that works or if it's safe.
And how would I be able to get the correct circuit to get 6v 6.4 watts of power.

Not really sure where to start?

So I tried a 5v 3A adaptor and it still didn't go on.

I tried finding more info and I found a picture of the charger online.

pictures below!

The charger says 6v - 11.8w
So I would need more than 5v 3a charger correct.

Or could it be that the camera needs a battery to work? (it's a phillips VKR 6847/00)


texts: Using a TVS diode instead of, or in addition to a MOV for AC line protection?

texts: For 220 V AC mains voltage, is it good practice to replace a 300 V MOV with a 300 V bidirectional TVS diode (like in here http://www.littelfuse.com/products/tvs-diodes.aspx), or connect both in parallel? Are there any points that need to be considered?


texts:
So I was thinking of buying a logic analyzer and found that a lot of the cheap ones are good to only a few mhz, and the microcontroller based ones can't have big buffers. So I was wondering if I could just use ram as a buffer? Like if it has 16 data lines, a 20 bit address, could I just feed 16 digital inputs (the ram I'm looking at reads >2.2V as HIGH so should be compatible with 3.3V logiv), and a 20 bit address counter run by a very carefully picked out crystal or some other kind of stable clock generation? I figure if the ram has a 45 ns write time, I should be able to easily get 22 odd MHz for only a few bucks, and then read it back with a slow micro controller or something, it doesn't need to access that data very fast.

However, I find that usually when I (and many other newbies) have these "why doesn't anyone do this?" ideas, there's usually a good reason.


texts: RF Antenna 50 ohm controlled impedance design

texts:
this is my first time doing RF design and I'm currently using ThingMagic Nano M6E RFID module and in the process of designing a 50ohm impedance circuit/trace from the IC to the antenna.

On their reference document, they specify that I'll need an LC circuit (assuming is for matching impedance network). I read somewhere that as long as my trace length is less than 1/10 of the wavelength, then I don't really need the matching network. Is that true? The module is using 917.4-927.2Mhz. If I were to add a matching network, how do I actually calculate/select the LC values for my circuit? And I'm using this antenna with 50 ohm impedance as well.

I'm using Kicad for my PCB design. For CPWG, how do I actually specify the gap width as the copper pour will fill the area? With the inductor and capacitor footprint, it actually makes the gap width varies across the trace, is that ok? I already created a keepout zone as shown but the C and L keepout zone seems to be affected the gap width.

Thank you.


texts: Understanding current readings from a multimeter

texts:
If you couldn't guess, I'm new to electronics.

So, I've just received my 3V air pump, it didn't come with any specs, so I'm trying to figure everything out.  I hooked it up to a DC variable power supply (at 3V) and a multimeter.

I switched the multimeter to 10A non-fused and placed the lead there as well, pinned a wire from the power supply ground to the pump, and used the multimeter as the bridge between the positive terminal of the supply and the other side of the pump.

I got a reading of 0.17 under normal conditions and 0.21 under full load.

Now, here's the question, 0.17-0.21, is that amps?  Does that mean I am pulling 170-210 milliamps?  When I toss these numbers into Ohm's law, I get 17.64706 Ohms resistance. Does this seem reasonable?

Since I'm just learning this, I just want to make sure this is all correct.  If I am wrong, I would love to understand more!