texts: Is there a problem to solder only one side of a dual PCB?

texts: If I do a double layer PCB (with the toner method) is there a problem if a solder the bottom side only? there are parts that are so hard to solder from the top layer, do I have to solder everything in the top and bottom layer? for example this is my PCB, and I want to solder a base in the pic slot so I can put and remove my PIC, but is hard to solder it in the top layer.


texts: JDS6600 signal generator - broken or normal?

texts:
I recently treated myself to a JDS6600-60M signal generator. It's a (very) cheap one but that's because electronics is just a hobby and not something I make money with or anything.
The other day I noticed that at very low frequencies (1-10Hz) the pulse wave looks like this:

10Hz

1Hz
I'm not quite sure if it did this before and when I increase the frequency the pulse gets more and more 'square' as you'd expect. From about 100Hz it looks pretty ok:

Still a bit 'round' but better and from about 200-250Hz upwards it looks fine.
Now I got to thinking and suddenly I realized I had used the signal generator about a week earlier to toggle a relay on and off (just for test-purposes) at about 1Hz frequency. And then it dawned on me that this could've cause some pretty serious flyback which may have damaged the signal generator? I had hooked the relay coil straight up to the leads to the signal generator; no flyback diode or anything else.
So my question(s) is/are:

Did I break my signal generator? Or is this "normal" (for cheap signal generators)?
Maybe someone with a JDS6600 can confirm this?

The manual has this to say about it:

From what I gather it should be able to generate a signal from 0 to 15Mhz but I don't know if it's supposed to be guaranteed* a square signal over the entire range. Also: It let's me adjust up to 60Mhz just fine for a square wave and I can confirm this on my scope (though at the higher frequencies the square starts to look like a sine, which is pretty normal I think for a 110MHz,1GSa/s (also cheap) scope).
* As far as cheap devices make, let alone meet, these 'guarantees' ofcourse.


texts:
I purchased some of these solenoids and cannot get them to operate with a 12v battery. I am simply connecting the ground to one open wire and the positive to the other and the solenoid does not retract as I would expect. I also tried using this power supply, which causes the thing to shutdown when connected.

Is there something else I need to include to get these to work?


texts: Metal connector case connection when using a plastic housing

texts:
I'm designing a board with 2 SFP connectors and I am not sure what I should connect the cage pins to.  The manufacturer recommends connecting the case pins to chassis ground but my product is in a plastic housing.
I read this article but it assumes a metal housing.  Should all the case pins be connected directly to ground?  Or do I need a local plane under the cage and AC couple it to ground?


texts:
I am trying to understand pMOSFET. I searched online tutorial saying that pMOSFET is like a closed switch if V(gs) < V(threshold), like a open switch if V(gs) > V(threshold), V(threshold) typically -1.5V.

But when I do an online simulation, it show the following result. Does anyone know why the left one has current from Drain to Source but the right one doesn't ? Left one does't satisfy V(gs) < V(threshold) condition to closed the switch, but still has current flows. And why sometimes the gate, drain or source is in green, sometimes in shadow ?


texts: Confusion about Laplace and frequency response of a electrical circuit

texts:
I have a confusion between the Laplace transform of a circuit and the frequency domain AC analysis.
Suppose we have a series RLC resonant circuit connected to an ideal sinusoidal voltage source.

We can write
$$V_m \sin(\omega t)=i R + \frac{1}{C} \int i dt + L \frac{d i}{dt} $$

now if we take the Laplace transform (assume initial inductor current to be zero),

$$\frac{V_m \omega }{s^2+\omega^2} =I(s) \big(R + \frac{1}{s C}  + s L \big) \Rightarrow I(s) = \frac{V_m \omega }{(s^2+\omega^2) \big(R + \frac{1}{s C}  + s L \big)} \tag{A}$$

On the other hand, using frequency domain analysis we can derive current as,
$$ I= \frac{V_m }{R  +j \omega L + \frac{1}{j\omega C}} \tag{B}$$

My question is: How can we deduce (B) directly from (A) without inverse Laplace transform? just putting \$s=j \omega\$ will not simply reproduce (A).

To further elaborate my question: If we have a current of a branch as the form of
$$I_n=\frac{ V_n (s \sin\theta+\omega_1 \cos\theta)}{s^2+\omega_1^2} \frac{1}{Z_1(s)} $$

can we directly deduce (without taking the inverse) that particular branch is effectively acting as it is connected to a voltage source of \$ V_n \sin(\omega_1 t + \theta) \$ and impedance of the branch is \$ Z_1(j \omega) \$?


texts: Tips for adding voltage op amp to equipment

texts:
I have a source that creates a smooth sine wave in the range ±100mV at 1-15Hz.

Due to distances I need to amplify the signal to at least ±5V, and I should also maintain the shape of the signal if possible. Preferably ±12V, but I have been told ±5V will work as well.

How can I do this? An electrical engineer will do the actual work on this equipment, but I need to have some knowledge so I a can coordinate things.


texts:
I have a question,
why is rs485 limited to less than 100 meters at 10mpbs ( mbaud )
and is 100Base-TX ethernet applicable on 100 meters with 100 mbps bitrate

i know that rs485 normally use a sort of NRZ encoding with 2 levels
and ethernet uses a MLT-3 4B5B encoding with 3 levels

but i cannot understand why the difference between distance and baudrate of
ethernet and rs485 is more than a factor 10 (ethernet has an actual baudrate of 125mbps due to 4b5b encoding)

and theoretical if 100base-tx would run at half speed would the usable distance then muliply with 2?

endgame for me would be to create an 2 wire (half-duplex) master slave (rs485-like )network with around 200 nodes , a length of 1000 meters and a speed of ~10 mbps.

or alternatively a half duplex P2P network like EtherCat but simpler like rs485 but with a usable distance of 200 meters and a speed of ~10mbps

-source of rs485 distance baudrate graph
https://www.maximintegrated.com/en/images/appnotes/3884/3884Fig06.gif


texts:
I am trying to get some input on the feasibility of this project. I will have a radio controlled car. The car will have sensors that will output data like acceleration, gyro something like 6DOF. A similar sensor will be on the helmet of the driver of the car to control a camera on the RC car. So if the driver turns the camera will turn at the same time. Video streaming also needs to come from the car for the virtual driver.

Signals from car

X
Y
Z
Acceleration
video

Signals to car

Head Position X Y Z
Throttle
Braking
Steering

Traditionally RC cars are controlled by burst of AM but I think the best method for transmitting all this data is via wifi? Would it be fast enough to be realistic with little latency? Or just stick with regular methods?


texts: Help finding transfer function for root locus using Matlab

texts:
I'd like to pick \$k_d\$ using root locus method, but have problems deriving the necessary transfer function of the system presented below. Assume \$k_p\$ is fixed. The question originates from Randal Beard's paper: "Quadrotor dynamics and control", p.42. The answer is actually given there, but for a slightly different block diagram and with no derivation. So it's the derivation that matters to me most.

As far as I understand the method in question, I need obtain an equation:

\$ 1 + k_d P(s) = 0 \$,

but don't know how to derive \$ P(s) \$.

If you're able and willing to help, please don't only provide the solution - I need to know how the solution was obtained to be able to help myself in the future. Any hints appreciated.

EDIT: What I already tried out is simplifying the above block diagram into the form below:

Then we have:

\$ \Large L(s) = \frac{G(s)H(s)}{1 + k_d G(s)H(s)} \$ %Inner loop's transfer function

\$ \Large R(s) = \frac{L(s)/s}{1 + k_p L(s) / s} = \frac{L(s)}{s + k_p L(s)} \$, substituting for \$ L(s) \$ we have:

\$ \Large R(s) = \huge \frac{\frac{G(s)H(s)}{1 + k_d G(s)H(s)}}{s + k_p \frac{G(s)H(s)}{1 + k_d G(s)H(s)}} = \Large \frac{G(s)H(s)}{s(1+k_d G(s)H(s)) + k_p G(s)H(s)}\$.

So the point is, how to convert \$ R(s) \$ denominator into: \$ 1 + k_d P(s) = 0 \$.


texts: Logic inverter feedback resistor, SPDIF Input/Ouput circuit

texts:
What purpose of these resistors? Spdif level about 0.5Vpp. Do I need use feedback resistor if I will convert 3.3V SPDIF to 5V?

I want to make 4-way SPDIF Input/Output for WM8805 I2S<>SPDIF converters, and made a schematic. What should I do better?


texts: AP5002 step-down switching regulator loop stability

texts:
Problem, parameters

I have an 5V output power supply, with 2S LiPo input (6-8.4V), implemented with AP5002 (PWM control 2A step-down switching regulator, docsheet), and for the life of me, I can't make it stable. The PSU is chirping, dropping voltage irregularly, and in general shows a chaotic output voltage.

This is at around 300mA load. The full load my circuit draws is 900mA (mostly LEDs).

The initial circuit is as follows, I'm using ceramic capacitors both for input and output caps.

Note: C40 is far from PSU, close to the battery.

Ground plane with green:

My attempts

I started calculating the feedback loop, but I neither have enough experience in this, and also several parameters of the AP5002 are missing (eg. the internal amplifier circuit gain, transconductance, etc...). I calculated however the zeros and poles of the output filter network:

$$
W(s) = \frac{U_{out}}{U_{sw}} = \frac { R_e C s + 1 } { L C s^2 + R C s +1 } \\
p_{1,2} = -109 +-4.545 \cdot 10^4 j \\
z = -9.47 \cdot 10^6 \\
k = 218
$$

I started to implement a compensation network based on this docsheet of a similar regulator by ST. The most stable configuration I was able to come up with is this:

The values again (close to the theoretical values calculated based on the ST doc):
Rs=160R
Cs=2.2nF
Rf=6.8k
Cf=2.2nF

This was better, but became unstable at around 400mA load. I tried countless variations of values, even soldering in 47k trimpots for Rs and Rf to be able to sweep values from 0-47k. No success.
I also tried a 22uF tantal cap for output filter, hoping the larger ESR will make a diff, but nope; the loop behavior hasn't changed.

Any comment or advice is appreciated, thanks!


texts: What value determines the current flowing between two interconnected ICs?

texts:
If I connect two ICs (lets say two Arduino UNOs with one pin configured as OUTPUT and another as INPUT), something must limit the current so that there is not a short circuit when driving HIGH.

What values on the datasheet should I be looking for? Some kind of internal pin resistance?

The reason I want to know is I want to put an LED inline to cause a 2V drop from a 5V IC to an ATTiny65 input pin but the LED forward current is limited to 20mA. (I realise there are better ways to do this but I have a PCB already printed off which only allows two 1206 components in series in the data line).


texts:
I am using an STM32F407VGT board with an STLINK V2 programmer in keil IDE. I have downloaded to the board a very simple code:

#include "stm32f407xx.h"
#include <stdint.h>

int main(void)
{
  RCC_TypeDef *pRCC;
  GPIO_TypeDef *pGPIO;
  pRCC = RCC;
  pGPIO = GPIOA;

  pRCC->APB2ENR |= (1 << 0);
  pGPIO->PUPDR = 0x11;
  return 0;
}

The problem is that when I try to enter to Debug Session, I cant use breakpoints or see the memory, the command window shows "cannot access memory". I have done the needed debug setup, even I have tried changing the parameters but I just cant´t access the memory on debug, but i do not have problems loading my code. I have also tried on Eclipse/OpenOCD and I also can download the code to the board, but it has the same issue with debugging.

This is my board

and this is how keil looks.


texts: How to analysis this Operational-Amplifier circuit?

texts:
This is a reference buffer circuit that make a single-end audio input to be the differential inputs for ADC.

Circuit-1:

It does not like typical Op-Amp circuit of the same purpose like below.

Circuit-2:

I understand how the circuit-2 works, but I can not figure out how the circuit-1 works. How the input signal be transformed into a pair of inverted signals?

What is the OP-Amp configuration of IC1 and IC2?

Dose the IC1 use a non-inverting amplifier configuration with negative feed-back?

If so, for audio signal the C1 will short-cut the output and negative-input, then why we need the R2 and and R1 resistor?

Which configuration of IC2 is used, the non-inverting amplifier or the inverting amplifier configuration?

Could you explain the work of R1,R2,R3,R4,R5 and C1,C2,C3,C4?

Thanks!


texts: Where does Zi = hie+1(1+hfe)RE come from in a BJT from Hybrid Model?

texts:
I've been struggling to understand how to get to this expression without knowing about re model (actually, still knowing about it, I can't get to understand this).

In a BJT in, how does one get to Zi = hie+1(1+hfe)RE from the Hybrid Model on an unbypassed emitter configuration?

I saw someone saying it had to do with seeing the resistance from a different terminal it is in, and we had to "move" the (1+hfe) from the current part to the resistance, and this last part is cool to me, I think. Though... I can't understand why we must do this, since I've never done it when calculating the equivalent resistance on a circuit. I also saw it might have to do with having a dependent current source. Though, in my way of viewing this, if Zi is calculated with Vi = 0 V by definition, then the current source evaluates to 0 A and there's no current there --> open circuit, we cut from there and just remains a series of hie with RE (Zi = hie+RE), and that's wrong and I don't get why they're not in series if I just cut the source from there as I always do with the other circuits (the problem might be with the dependent source which I might not be understanding well, but I have no idea).

I've been looking in Electronic Devices and Circuit Theory and in Integrated Electronics Analog and Digital Circuits, but I can't find an explanation of there that comes from without mentioning the re model. If they're equivalent expressions, I'd just like to know how it works, so that they are indeed equivalents not just by the picture but also from the calculus and it would make sense in my head (might also help me understand something I didn't know I didn't understand, as a start).

Bonus: could anyone explain me (or point me to an explanation - that works for the other question too) how to get to that expression, even if from knowing about the re model? Zi = (beta+1)re and Zi = (beta+1)RE --> absolutely no idea how to get to the second from the first one. But maybe that has to do with the first question. Sorry, I'm confused.

Thank you in advance for any help on getting this.

EDIT: maybe I should have mentioned I'm interested not in any hybrid model, but in the h-parameters model. I thought Hybrid Model would lead immediately to h-parameters model (isn't it called only Hybrid Model?).

EDIT 2: I'll accept Verbal Kint's as it is the one that helped me understand the dependent sources (or at least a bit more than I did) with help of a friend removing some wrong ideas (or at least that didn't make sense for me) I had been put in my mind by other people. Though, LvW's answer helped too in understanding a bit better first how to deal with this without going to any models, so thank you both, and I'll accept the one I said because it's the one I'll use more, possibly (we haven't learned much about Control Theory yet, so I didn't completely understand but with time I will). Also sorry, don't have enough reputation, but I hope the 3 people get the upvote I sent. Even though analogsystemsrf's answer didn't help me on what I needed, helped clear something else on my mind so also thank you for that. This is a big text...


texts: Can I safely substitute a DC converter for the Macbook's AC adapter?

texts:
I want to go from this:

to this:

The converter would be this: http://smile.amazon.com/dp/B00HVCWGNE or something like it.

Does this sound safe?

The step up converter would be set to a specific output voltage and remain there. This bothers me insofar as it relates to a statement on Ken Sheriff's blog about Apple's "charger:"

  The charger provides a very low current...6 volt signal on the power pins (3 volts for Magsafe 2).

I don't know if he means the adapter or the connector that plugs into the laptop. I want to make sure all the 3rd parties that already produce something like this don't know something about the 3/6 volts that I don't.


texts: Difficulties supplying 5V TTLs to 50 Ohm terminated single photon counter

texts:
Some background:

I am building a confocal fluorescence microscope. Long story short, photons are recorded using a Time Correlated Single Photon Counter (TCSPC). This TCSPC is capable of time stamping each individual photon.

Since the detector is a point detector, I "scan" a laser beam over the sample using galvo mirrors to image it and I correlate the position of my laser beam with the photon data.

Laser scanning is achieved by generating a wave form on an NI-USB6343 (specs in link) AO channel. At the start of each wave form period I also generate a pulse on one of the digital outputs of the NI device. This digital out is recorded by the TCSPC on a dedicated channel and serves as a reference to reconstruct the images. For this, the TCSPC has a dedicated channel.

The issue

I can do programming and chemistry but have zero knowledge on electronics.

APDs, TCSPCs etc... all operate on 50 Ohms (no idea why). The NI box is not particularly designed for that it seems and any 5V triggers generated by it are not registered by the TCSPC.

Connecting the digital out of the NI box to a scope using a 50 Ohm BNC cable with a 50 Ohm terminator on a T-splitter, I can indeed see that my pulses are not 5 V anymore but merely 1.5 to 2 V. All other aspects of my pulses (rise time) seem to correspond to the TTL spec.

These are the relevant spect of the DO

And this is the spec of the TCSPC:

Finally, the specs of the detector (of which pulses are being picked up by the TCSPC):

Since the TCSPC costs more than a luxury sedan, I'd like to get some feedback on the type of circuitry that might help to adapt the output of the NI box to the requirements of the TCSPC without the risk of damaging either.

I would also be helped by potential suppliers of such equipment or perhaps companies where I could order custom circuits to achieve my goal.

I have looked at posts like this but given I have zero knowledge of electronics let alone soldering skills, I couldn't make anything out of the supplied information...

Edit

As suggested in the comments, the TTL specs look like the device might be intended to receive negative voltage signals (and detect falling edges). However, looking at the provided manual, there seems to be a distinction between the signal inputs (to which I connect detectors and which have high time resolution) and the "low resolution" trigger inputs.

In the manual I found a specific description referring to them:

So there is a reference to a NIM style connector (NIM seems to predate TTL with True−16 mA into 50 ohms = −0.8 volts) but it clearly says "TTL in". So I assume that those M1 to M4 channels should accept "standard" TTL, i.e. positive voltage signals.

Moreover, most movable stages or salvo scanners indeed provide real TTL triggers to indicate "start of line" or "start of frame" events while raster scanning an image area...


texts: What are the best free schematic tools out there?

texts:
I'm sure there are plenty of schematic tools available.  Which ones do you use/prefer?

Feel free to also list tools which aren't completely free but very popular.


texts: Input Voltage to Sawtooth oscillator Confusion

texts:
I have attached a schematic of a project that I am working on, it is following a design that has already been done and works well. My problem is regarding V7. now the schematic below works perfectly when V7 is a DC source of the required voltage, in this case 0.039V. But the actual source of V7 is from a microcontroller, which sends 12 bits to a DAC, which then outputs a voltage which is what V7 is simulating. My question is, wouldn't the output from the DAC be an AC waveform? However when I replace V7 with an AC waveform it doesn't function properly at all. what am I missing?

EDIT: The AC source only works when the frequency of the AC signal is 1Hz. would then be something expected from a DAC?


texts:
I'm planning on incorporating a latching switch into my design:
https://lcsc.com/product-detail/Electrical-Switches_XKB-Enterprise-XKB8080-Z_C318860.html I also found the corresponding datasheet: https://datasheet.lcsc.com/szlcsc/1912111437_XKB-Enterprise-XKB8080-Z_C318860.pdf However, the pinout is really confusing to me and I honestly don't understand how to connect it properly:

Any help would be appreciated.


texts: Can someone explain the protection resistor in this current limiter?

texts:
I am looking at this current limiting circuit on Wikipedia, which says that

  The optional component R2 protects Q2 in the event of a
  short-circuited load.

Can someone explain why Q2 needs protection in this condition?

My understanding is that when Rload is shorted, the base of Q2 will see a voltage of Vcc, minus Vce of Q1 (because Q1 is in saturation, due to R1). Assuming that's above Vbe (of Q2), current will flow, but immediately cause Q2 to sink current from the base of Q1 - cutting it off.

Is the purpose of R2 to protect against this initial surge then?

Does R2 not affect the operation of the circuit? (As it forms a voltage divider with the base of Q2 - where the voltage is sensed) Or is it assumed that Q2 Ib is so small, that the voltage drop is negligible?


texts: Is it normal for relay to have quiet buzzing noise?

texts:
I just noticed that a relays (SPST) that I am using for my project have constant but really quiet buzzing noise. The buzzing noise stops when relay is active.

Is this normal?


texts:
I need to drive a 12 volt motor with a signal from an arduino.

For this, I connect the ground of the arduino to the ground of the battery eliminator creating a common ground.

I then connect the collector of the transistor (NPN) to the positive end of the power source and the base to the output from the arduino. I finally connect the end emitter to the motor which is connect to the common ground

Not getting the desired results, I connect the base of the transistor to a pin with constant high signal from the arduino. I measure the voltage between the emitter and the common ground I find it to be about 3 volts.

What is happening? Why am I getting the potential difference between the base and the common ground instead of 12 V?


texts: Arduino: read different voltage values in a range from -12 to +12V

texts:
I would like to trigger different functions in Arduino related to the following voltage values: -12V, 0V, 6V, 9V, 12V (the range is from -12V to +12V).

According to the value of the voltage read (-12V, 0V, 6V, 9V, 12V) I have to show instantly different light animations on a LED strip.

Considering that the Arduino is not able to read a such voltages directly, I suppose that probably I have to use a voltage divider, but I don't know how to calculate the resistors to use. Can anyone help me?

Thank you.

I was suggested also to use 1 dual op amp do the following:

Create inverting amplifier with a gain of 1, but insert a offset of 12V to the + (non inverting pin), this will max your -12 to 12V range change to a -24-0V range.
To the output of stage 1, connect another inverting amplifier with gain of 0.2 you would get a a positive voltage range of 0-4.8V which is fine to work with the arduino's 0-5V ADC tolerance.

What do you think about this idea?


texts: Choosing a relay to control outlets from Arduino

texts:
I'm working on a project that involves an Arduino Uno and some external electronics. I have a 12 V power supply that will connect to an outlet, and I want to be able to control this power using a relay connected to the Arduino (i.e. the Arduino will control the voltage that turns the switch on or off).

Though I understand it theoretically, I have no idea what I'm actually looking for. I was hoping someone here could point me in the right direction. All my searching has brought me to larger components. I was hoping I could find something that would fit on a typical breadboard. Do relays like this exist? Or is there another, easier method of doing what I'm trying to do?

EDIT: I went to RadioShack and tried to pick out things that fit the descriptions you guys described. Here's what I got:

Relay: http://www.radioshack.com/product/index.jsp?productId=2062480

Diode: http://www.radioshack.com/product/index.jsp?productId=2036270

Transistor: http://www.radioshack.com/product/index.jsp?productId=2062610

I also picked up some 1.5k Ohm and 1k Ohm resistors.

Will these work with the circuit diagram below?


texts: Inductor suddently conected to current source

texts:
simulate this circuit – Schematic created using CircuitLab

Assuming SW1 is closed for along time, and current in L2 to be zero initially.

What sort of current waveform can I expect in L2 when SW1 is opened ?


texts: PWM duty cycle RPM regulation via sensing DC motor current

texts:
I have a DC motor that needs to be RPM regulated, that is, it needs to turn at constant RPM regardless of the load. I've read this can be done by monitoring current thru the motor windings and appropriately linearly increasing the motor driving voltage.

I have a triangle oscillator and a comparator to generate the PWM. Reference voltage (goes from 0 to 10 V) on the comparator 'selects' desired duty cycle. PWM is running at 20 kHz. Motor is driven by this PWM through PMOS with low-side current sensing done via OPAMP.

Linear current increase linearly increases the reference voltage which again linearly increases the duty cycle.

The problem is when the PMOS is turned off, there is no current thus no voltage sensed and no reference voltage set (for duty cycle). I want previous duty cycle (reference voltage) to stay unchanged for a couple of PWM pulses (lets say 5ms for now) and then change to a new value.

I could have current sensing OPAMP with offset to generate some general duty cycle (reference voltage) with no current. But that would still cause drops in the duty cycle when PMOS turned off.

I'am thinking PI regulator done with OPAMP integrator, would that work, how would I go about implementing it?

Best regards!

EDIT:
Its a PMOS with motor and current sensing resistor on low-side.


texts:
I know that Fan out is the maximum number of inputs that can be connected to a specific output. This limitation clearly affects data signals, but I don't know the case for power-supplying ICs.

I have a DC/DC step-down converter with an output of 1.8V, this output  is connected as an input to many ICs in a system for power supply. My question is this, should I consider the fan out in this case, or I have to calculate the max output power of my converter (Voltage and current) and simply see if it can power my ICs from datasheets?


texts:
My instructor asked me why have I written the power factor formula as

  If \$\varphi\$ is the phase angle between the current and voltage, then the power factor is equal to the cosine of the angle, \$cos\,\varphi\$:
  $$|P| = |S|\,\cdot\,cos\,\varphi$$

with his reasoning that \$P\$ must always be positive with the exception when the resistance is negative, so I should not have the absolute value there.

Now I cannot remember the reason why, but I am pretty sure I have found it somewhere, but since I did a poor job with references, now I cannot find the origin of this formula.

I have found it on wikipedia.

Is this formula wrong? If yes, how can it be written correctly in this form. If no, can you forward me to some more reading on this? Many thanks.


texts: How does ground close the circuit, why isn't the current miniscule?

texts:
Let's say I have a 230v version of a AA battery resting on a table say, I touch the + terminal, think of me as a resistor of 1 ohm, the circuit needs to close, and can take infinitely many parallel paths, which is a bit confusing, but let's think of it as a single path to the - terminal.
The ground acts as a resistor, the resistance of the floor under my feet, up through the table legs through the air and into the - terminal. Think of the floor, table legs etc as another resistor with an enormous resistance, we now have a circuit with 2 resistors, first the me resistor of 1 ohm (say, just for a sense of ratio) and then the ground resistor of 1000000 ohms or some huge number, now the current through the circuit is miniscule and the voltage difference between my hand and the floor should be tiny no?
Equally, if I get one of the table legs, and use it to touch the + terminal with instead, I would expect this to be very safe? But what has changed, the resistance in the system hasn't changed much (ok now I force the circuit to mostly go through a table leg, but I don't think this is significant as it was always going to have most of its current through a table leg), so the current should be the same?
Equally equally, what's so different if I am levitating instead, now the circuit has to go through the air to reach the floor and air presumably has a really big resistance, several orders of magnitude greater than wood, but I already felt the resistance of the ground should be very big so I don't know I care too much?
To clarify, my question is, why isn't the current through me miniscule when touching a live wire as I imagine the resistance of the path to complete the circuit to be very high? In diagrams I often see all the grounds joined together to one vertex, but does this really make sense? to get from one ground point to another ground point you have to go through a lot of resistive material incurring a high resistance, no?


texts: Help Identifying a component via image (looks like a varistor)

texts:
I am having trouble identifying the following component:

It is in circuit as follows:

simulate this circuit – Schematic created using CircuitLab
From the circuit I would have expected it to be a pulldown resistor style to indicate that the connector is plugged in. The other pins of the connector are a wind sensor pulse output.
Any help is greatly apreciated,
Thanks

Update : After the helpful insight about checking it to be a PTC of NTC thermister I performed measurements and it was 22kOhms. Held it with my fingers and it decreased to 20k and breathing on it I managed to get it to go down to 18k.
In circuit measurements with the Vcc = 5V, across the thermistor it was 1.4 V approx.
So It is an NTC resistor
And it makes sense that it be an NTC resistor because when the weather is too cold, the wind sensor could freeze up and you would not know if the measurement is valid. The resistance would go up and therefore the voltage and that would be tending to a similar scenario as if the sensor was disconnected. i.e. Open circuit.


texts: The CAN bus in this vehicle has only one 120 ohm termination resistance. What problems would this provoke?

texts:
This vehicle that I've started co-developing is designed with only a 120 termination resistor on the CAN bus. Obviously there should be two of those resistors on two ends of the bus. I will be making that change, but there were some troubles in the past and present with the CAN bus. I'm wondering if it is likely that those are/were caused by this error. And how critical it is/was that the bus was terminated at only one location, and at 120 ohm.

I will be troubleshooting those issues, but they're intermittent. So it would be of great help to know whether it is sensible to keep looking for them if this termination resistor issue is solved.

Some information:

J1939 communications protocol is used
Bus speed 250 kbit/s
Bus length ca. 7 m
Amount of nodes is 15 (I guess), combined, 60 unique messages exist.
Average busload 40%, at intervals the bus load peaks at 100%

There are also issues with one node intermittently not getting online at startup. Twisted pairs were used that wasn't forgotten by the designer, if you were wondering...


texts:
I have to find voltage across R6 but the problem is, i get a parallel circuit in the end, when I solve the circuit i get,

R2345=76.67ΩR16789=96.059ΩTo apply voltage divider formula I have to get these resistors in series.
I want to know if its even possible to get the voltage across R6 using the Voltage-Divider formula.


texts:
I made a board with a STM32F031 and connected it to the ST-Link integrated into a STM32F4-DISCOVERY.
To this point I was able to figure out, that the SWD connection works, if I supply a voltage of <2.9V via an external laboratory PSU. Anything above crashes the communication, but it returns as soon as I go down to 2.9V again.

I must confess, that I didn't do proper decoupling of the VDD pin (just 1uF + 100nF) and I will fix it accordingly to the STM32F0 Reference design for my next revision.

Also I attached an oscilloscope to the VDD line but couldn't detect any significant spikes. Also I removed all components somehow related to the VDD line (LDO, other chips), so it's basically just the STM32 with some FETs attached to its GPIOs.

Here's a log of openocd:

Info : Unable to match requested speed 1000 kHz, using 950 kHz
Info : clock speed 950 kHz
Info : STLINK v2 JTAG v30 API v2 SWIM v0 VID 0x0483 PID 0x3748
Info : using stlink api v2
Info : Target voltage: 2.887324
Info : stm32f0x.cpu: hardware has 4 breakpoints, 2 watchpoints
Info : Listening on port 3333 for gdb connections
Error: jtag status contains invalid mode value - communication failure
Polling target stm32f0x.cpu failed, trying to reexamine
Examination failed, GDB will be halted. Polling again in 100ms

The Error, as I mentioned above, occours as soon as I go above 2.9V on my PSU. I find it odd that I have this target voltage line with ~2.89V, which is really close to my error threshold.

Update 1:

So I wrote a little Blinky programm, flashed it with SWD while the supply was 2.9V and then ran the chip with 5V on it's LDO resulting in VDD@3.3V, and it works. I dare to assume the Target voltage is not respected by the integrated stlink-v2 on the Discovery board. Ordered a stand alone, will update.

Update 2:

Stand alone STlink brought no difference, creating a second revision of the board with all caps as per reference design now works. Still, I was unable to reproduce the error with a STM32Ardurino board removing all the caps.


texts: What happaned when the flyback transformer is in saturation?

texts:
I am trying to design a DC-DC flyback converter.
Input voltage is 110V and output voltage is 24V. I have used NCP1252A PWM controller.
Flyback transformer windings:

Primary -> 24 turns

Secondary -> 12 turns

Aux -> 6 turns

Switching frequency is 470 kHz (for very small ferrite core)
When I tried to apply 110V, although the MOSFET is robust, gate signal is not created. I can not understand why it is not working. When I removed the MOSFET, the PWM controller created gate signal. Why?
I wonder if the transformer is in saturation. What happened when the flyback transformer is in saturation?
I can not understand how to calculate Rcomp resistor. I examined the NCP1252 datasheet and I calculated as 0R. (Because I am using lower duty cycle than 50%. As I understand We needn't it if using lower duty. But I'm not sure this info !!!
This matter is explained at slope compensation section at the datasheet.
NCP1252 datasheet
Circuit schematic is below [added in 23.07.2020]


texts: How can a one million megohm resistor be useful?

texts:
I used to do periodic maintenance on a detector system for low-power-level particles. Its circuitry included a one million megohm resistor. It was in a sealed solid brick made maybe of Bakelite, about 4"x2"x0.5". I mean, isn't there less resistance between you and I right now? How was that a useful thing?

/edit add 2016.12.13

It seems I have been unintentionally playing a dumb game, not saying what this equipment was for.  Since all the tech manuals were marked classified, I was uncomfortable stating what the equipment was. Those manuals are now more than 55 years old.  Plus anyone could have linked from my profile, gone to my site, and seen my resume.  This would show I was a reactor operator on a nuclear submarine. The info, at least in general, is extremely unlikely to still be classified, and my career has never been. So, I've decided to just say it.

I am speaking of the low power level neutron detector system on my sub.  It was active while the reactor was shut down. We turned this off during start-up, and back on at the end of shut-down. We also had a separate intermediate range detecting systems (used during start-ups and shut-downs), and a high power detecting system used during operation.

Sorry if this lack of info was frustrating to folks.  It was frustrating to me, feeling like I was talking around things that I should just say.


texts: How can I detect a pulse from a device with the AC'97 component of a Xilinx Atlys board?

texts:
I have a digital device which transmits rapid pulses over a 3.5mm audio cable, indicating that some event has occurred. I want to connect that device to my 3.5mm line in jack on my Atlys board and determine how many of those pulses have come across. I have read some other people's questions regarding transmission, but have yet to find community sourced information on reception with the audio jacks.

The maximum pulse frequency from the device is a little under 6kHz, so I figure the Atlys board will have no problem.

I was hoping I could just monitor some "data ready" type of signal. But with the two different clocks (L15, L13) and the complexities of AC'97, for a beginner it's quite confusing.

Does anyone have any thoughts or suggestions on how I might accomplish detecting these pulses?


texts: I am using this 5V Stepper Motor and Driver IC. My motor is working fine but it consumes 10-20mA when there is no pulse. The circuit should consume power only when there is a pulse. I have attached the driver circuit and schematic of the communicator. My question is how to drop the holding current of the motor by that the motor doesn't consume power. Or if you got any idea or any modifications I can do. Please help me with your ideas.


texts: How to use a fingerprint reader sensor with STM32F4 Discovery board?

texts:
I would like to include a fingerprint reader sensor in a home project that I've been planing. Searching online it seems that the most standard kind of fingerprint reader sensor you can find is this one.

The problem is that I can't find any datasheets or example projects that would show me how to include it in own project. I am using STM32F4 Discovery board. I have found a website that shows how to use it in an Arduino project and even has some library written for Arduino. But I don't have and will not use Arduino.

Is there any resource that could help me get this kind of sensor running on my STM32F4 Discovery board ?


texts: Calculate the Norton Resistance and Current and the Thevenin Voltage of the following circuit

texts:
U=10 V, R=10 ohm

I calculated the resistance as such:
1/Rt = 1/R + 1/R <=> Rt = R/2 = 5 ohm

To calculate the voltage I did KVL as such:
U - 2Ur = 0 <=> Ur = 5V, where Ur is the voltage in the resistors
And then by applying KVL to the closed network that goes from a to b passing through the resistor, I got Ut=5V

Then I calculated the current using U=RI, and I got I=1A.
Is this correct? Because in my solutions I=0,5A


texts: Can I measure if current is on or off in cable with 24v DC (in a cheap way)

texts:
I have a number of valves that control the heating in rooms in our house. The valves have a pin on top which opens or closes the valve. The position of the pin is controlled by a regulator that sits on top of the pin and can be seen in the image below. The valves are either open or closed. I would like to monitor the valve position. I assume the only way to to that is to measure if a regulator is getting any current.

According to what I have found from the net it seems the regulators are getting 24V DC and using 1 W. Would that mean A=W/V => 1/24 => 42mA? On another place it says that "start current is <300 mA during maximum 2 minutes". The whole product name is Roth A5 24V Nc 1W. I assume A5 is the product name and does NC mean "normally closed"?

I don't know how regulators like these work, do they get current all the time they are open or only part of the time, but let's assume the get current all the time they are open.

Question:
What kind of non-intrusive sensor can I use to monitor if the regulator is open or closed?

I would like it to be non-intrusive because I'm not sure what the company that has delivered the system says if I cut the cords and install something. Since I have eight cords to monitor I would prefer if there was something costing like max 10€/sensor.

Update I changed the picture to ones from my own system where the regulator is open. I can also confirm that the regulators that are open are very hot on the top.

Update 2 Added a picture of the cables to the regulators.

Update 3 The original task was to log when the valve was open or not. Since the valves are either open or closed and not purposely in between I ended up ordering some micro-switches that the regulator will trigger when it opens.


texts: How do you measure phase difference between two wideband signals

texts:
I am receiving a signal from two antennas, and I wish to compare phase in order to extract angle.
I know that you would usually use a phase comparator. I was wondering whether this would work only with pure single tone signals or with more wideband signals as well. My signals have a bandwidth of about 2KHz (not so wide, but does it make a difference?).

I understand now that I am actually not looking for the phase difference but rather time difference. Wondering whether this could be done in analog.

Thanks


texts: What is the maximum current needed to power (supply current) STM32F401RCT6?

texts:
I am designing a custom PCB based on an STM32 microcontroller. What is the maximum current needed as a power supply for the STM32F401RCT6? I have 3.3 V and 250 mA regulated current to power the STM32F401RCT6 microcontroller.

From the datasheet:

As per the datasheet, do I need only 160 mA in total to power the microcontroller? Or do I need 100 mA for each Vdd pin? My package has 4 Vdd pins, so do I need 400 mA in total?


texts: Will the Stepper Motor 17HS3401 work fine with the TMC2130 driver? Or is the driver chip going to burn? Are they compatible?

texts:
I am considering whether to buy the stepper motor 17HS3401 of this catalog

Current

The motor uses a rated current of 1.3A. I need to connect it to the TMC2130 driver, which accepts just 1.2A with some peak of 2.5A. Should I be worried? Is the motor going to burn the diver chip in the long term?

Voltage

Also, the voltage is not shown in the motor features. Should I multiply the "Rated Current (A)" and the "Phase Resistance(ohm)" to get the voltage? >> 1.3A x 2.4ohm = 3.12V. It seems very low to me because most of this kind of motors use 12V or even 24V. Are my calculations right?


texts: I tried to separate soldering on a Raspberry Pi but exposed some copper. The Raspberry Pi boots just fine. Is this safe?


texts: how do I use H11L1 correctly to receive MIDI?

texts:
I was following this schematics. This is the first result on google images

My Arduino Serial Monitor received nothing. I tried to replace the H11L1 with LED, and it does blink. but as soon as I connected the H11L1 (while keeping the LED in parrarel and not connecting the H11L1 to anything else), the LED stops blinking. Tried with and without resistors, also tried to reverse the cable.
Then I plug out the H11L1, afraid to break my keyboard and the LED blinked again.

EDIT :
I was using Arduino Mega. I put it on reset mode by connecting Reset to GND. then I connected it like above and opened serial monitor. Nothing.
Also I don't use capacitor, so I edited the image a little.

Where do I start troubleshooting?

another edit, here goes my Arduino so far. Sorry for bad soldering.

What I've tried so far :

Reading the serial pin as a digital pin, without connecting the H11L1 to anything except the resistors, just like above. Always return 1.
Tried to put multimeter on it, still returns 1, expected return is 0. Tried to turn on LED with it, the LED did turn on.

EDIT as of 03/28/2019

I changed Arduino Mega to Wemos D1, and H11L1 to PC900V (some source told me that it is the same IC)

After that, I connected that (still using the same schematics) to D2 instead of RX, and using this code to check it. Still no luck, whatever I did it still only returns 1.


texts:
I would like to connect a signal coming from a line receiver to several op-amp based filters in parallel. The basic topology (high-shelf) looks like this:

simulate this circuit – Schematic created using CircuitLab

What I don't understand is the meaning of R1. Why does the positive input have to be shunted to ground? Doesn't it act as a voltage divider since the inputs of the op-amp have their specific input impedance?

My question is, if I want to connect several of those in parallel from one output, do I need both R1 and R4, or is one time enough? Do I need them at all?

simulate this circuit


texts:
TL;DR

What is the purpose of D3?
Which is the correct orientation?
Does it depend upon its intended purpose (whether to protect the USB or the 7805)?

I have two ATtiny85 development boards, one is a DigiSpark and one is a generic mini development board.
As the schematics below show, they are essentially the same:
DigiSpark:

Mini development board:

However there is one small but significant difference - the orientation of D3:

The DigiSpark has the anode to 5V and cathode to USB 5V;
the Mini Dev board has the anode to USB 5V and cathode to 5V.

I have tested and checked the orientation of D3, on both boards, with a diode tester and both of the schematics are indeed correct1, and both boards work from USB power, as required. However, the orientation of D3 on either board is opposite to that of the other.
For the Mini development board, I assume that the diode (with the anode connected to USB 5V) would protect the USB from externally connected VIN feeding back, via 5V. Would that be a correct assumption to make?
However, for the DigiSpark board:

How can the board be powered from USB, if the diode is blocking the USB 5V (anode to the 5V output of the 7805)?
Is D3 protecting the 7805 from USB power?
If so, then the USB is left unprotected (when an external supply is applied)?

For completion, here are annotated photos of the two boards, showing the component identifiers:
Annotated DigiSpark

Annotated mini development board

For full disclosure, these images come from my blog Digistumped?, which has some additional reasoning explained, which I don't need to go into here.
I have checked and metered out both boards and checked the components and their connections. All components are accounted for in the schematics... There are no hidden components (which aren't shown on the schematics) and no hidden traces/connections/contacts.
Footnote
1 I have searched and found links discussing the orientation, but none have a suitable explanation:
Diode D3 is not in reverse. as suggested in post#2 of digispark ATTiny85 not running on independent power:

Is D3 really connected as per the schematic? I think it should have the anode connected to the USB connector.

as this Bypass Digispark 5v 500ma current limit? post states

we can see that there is a diode that drops the voltage to the VIN pin on the board...as i understand it that pin is there to prevent external power from feeding back into the usb port...

See also Powering the Digispark and Power from USB connector, in particular this post:

I do think the schematic for the original digispark is wrong... the diode is pointing towards, the 5v, not away from it, so it is allowing the USB to provide power to the 5v pin, but preventing any power present on 5v from feeding into the 5v line. Just to be clear, this is the schematic I am looking at for the Digispark...


texts: Best method to short an ic chip on board

texts:
What is your preferred method to temporarily short two pins (DI, GND) on an IC chip while it is still on the board? Note this must be thin enough to allow the board to be replaced and stable enough to last through boot up and several software operations.

I am considering trying to cut conductive tape in a single thin shape to bridge the pins, or using a strand of copper, attaching with conductive ink and then taping it in place. Any better, easier methods you prefer with standard materials, again while keeping the chip on the board.


texts: Capacitance Measurement With Oscilloscope

texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to determine the capacitance of a sensor, but the oscilloscope's internal capacitance is loading the measurement too much.

What is an appropriate method to determine a low picofarad capacitance using an o'scope in this situation? (o'scope internal capacitance is 24pF).


texts: PC Board/Power Transistor heat dissipation

texts: I am attempting a repair on a failed Sansui 881 Receiver / There's an  obvious problem on the power supply board where the heat sink of a power transistor has 'legs' that are soldered to the PC Board, not connected in the circuit and have reached a temperature that has caused the board to discolor and  the circuit trace underneath to substantially lift off the board.  This is likely not to be the "fix" of the failure, but rather an aspect of it and I'd like to change the heat sink anchoring scenario to the steel chassis.   What was the wisdom in soldering the heat sink to the PC Board in the first place".  thanks


texts: I have an accelerator pedal which outputs .75 to 4 V and I need to convert this to a 0-5 V output for my controller.I found a circuit that fits(shown below),which uses an opamp in non-inverting configuration with feedback,but I'm not sure how it works so I am not able to adjust the resistor values on my own to get the desired output.Can someone explain how I should calculate the resistor values?


texts: Charging a battery with two sources, should I put them in series or parallel?

texts:
I would like to charge a battery using two sources (solar and a generator), should I put the two sources in series or parallel before the battery?

The battery is actually 3 batteries in series. Each of them is 1.2 V with a capacity of 2300 mAh.

Is it better to give the battery more current or more voltage?


texts: How to reduce MOSFET heating in Buck Converter

texts:
I have designed this Buck Converter which convert 60VDC to 12VDC at 10A.
Switching Freq 100KHz.
Facing MOSFET too much heating issue.
MOSFET ON time and OFF time is decided by a UC3845B based circuit. MOSFET gate is biased with 2.2R resistor and pull down of 5.1K
is there any way to reduce MOSFET heating?
I've increased MOSFET rating to 110A 80V. Previously was 75V 75A but no succcess.

Edit 1: Updated Schematic for better understanding.

Edit 2: Previously tried this INFINEON MOSFET. Heating was less.

Then used this ST MOSFET.
Heating was more in ST MOSFET

Hello, here is an update, can I use below circuit as bootstrap?
here in place of 5V Input either I can use 60V directly or 12V from output.


texts: Need help to identify a three lead passive component

texts: Here's a picture of a damaged component salvaged from an old spectrum analyzer. The number on the component reads 226K & 253, which I presumed it as dual tantalum capacitors ( with three leads) of values 226nF and 25nF. Any advice or alternative replacement component values may please be suggested.


texts: Powering up several devices from one charger

texts:
I need to power up 4 peltier elements (at 12vdc, approx 50W) and 2 fans( at 12vdc).

I was wondering whether a charger(like that of a laptop/mobile) that supplies 12vdc for a single device will power all of these devices up if I connect them in parallel?

If not what kind of device (preferably cheap) should I go for powering these devices?


texts: Is it possible to connect this LCD display. Directly to the PC serial port using a prolific usb 2 serial converter ?


texts: How do I calculate the power consumption of the polarity detector circuit?

texts:
What method can I use to calculate the power consumption of this block?
In the paper it's equal to 3 μW at 1.5 V.
The datasheet of the piezo sensor.
The datasheet of the MAX9119 comparator.
Circuit:


texts: Im currently trying to control the power of my induction heater, i want to use an interrupter to control it. but if i now interrupt the driver at random points, the mosfets wont turn off at zero voltage points, how would i go with building a comperator circuit that only interrupts at a zero crossing?


texts: Invalid property name 'platform.board_id' in TCL VIVADO bd project setup

texts:
experts. I am a newbie to this FPGA community so this might be a very basic question.
I am sourcing my colleague's TCL shell script to create a block-design.
The relevant part of the shell script is below.
# Set the directory path for the original project from where this script was exported
set orig_proj_dir "[file normalize "$origin_dir/../vivado"]"

# Create project
create_project ${_xil_proj_name_} "vivado" -part xczu2cg-sfvc784-1-e

# Set the directory path for the new project
set proj_dir [get_property directory [current_project]]

# Set project properties
set obj [current_project]
set_property -name "board_part_repo_paths" -value "$origin_dir/../board" -objects $obj
set_property -name "board_part" -value "trenz.biz:te0820_2cg_1e:part0:2.0" -objects $obj
set_property -name "default_lib" -value "xil_defaultlib" -objects $obj
set_property -name "enable_vhdl_2008" -value "1" -objects $obj
set_property -name "ip_cache_permissions" -value "read write" -objects $obj
set_property -name "ip_output_repo" -value "$proj_dir/${_xil_proj_name_}.cache/ip" -objects $obj
set_property -name "mem.enable_memory_map_generation" -value "1" -objects $obj
set_property -name "platform.board_id" -value "te0820_2cg_1e" -objects $obj
set_property -name "sim.central_dir" -value "$proj_dir/${_xil_proj_name_}.ip_user_files" -objects $obj
set_property -name "sim.ip.auto_export_scripts" -value "1" -objects $obj
set_property -name "simulator_language" -value "Mixed" -objects $obj
set_property -name "webtalk.activehdl_export_sim" -value "62" -objects $obj
set_property -name "webtalk.ies_export_sim" -value "62" -objects $obj
set_property -name "webtalk.modelsim_export_sim" -value "62" -objects $obj
set_property -name "webtalk.questa_export_sim" -value "62" -objects $obj
set_property -name "webtalk.riviera_export_sim" -value "62" -objects $obj
set_property -name "webtalk.vcs_export_sim" -value "62" -objects $obj
set_property -name "webtalk.xsim_export_sim" -value "62" -objects $obj
set_property -name "xpm_libraries" -value "XPM_CDC XPM_MEMORY" -objects $obj

In the process of it, I get this error message that claims there is no property name for 'platform.board_id'. It's where it specifies the FPGA ID, and it seems ok to me, but it gives me this error message.
ERROR: [Common 17-142] Invalid property name 'platform.board_id'.  Please use the 'list_property' command to find properties supported by the target 'project' object.    while executing
"source scripts/cabletester.tcl"

After commenting out the line, the shell script obviously crachses with message that .bd file does not exist. Could someone explain and help me with the issue?
Thank you!


texts: I have a Microcontroller with a DAC output of 0-3.3V. What external circuitry can I use to convert it into a 4-20mA current transmitter.


texts: DALI specification: help to understand the physical layer schematic

texts:
I am trying to understand an NXP circuit that has implemented the physical layer of the DALI specification. In particular, it is DALI master hardware.  For the transmission (page 4), it says exactly:

  For high signals of DALI1_TX, Optocoupler OK2 connects junction R2 and R3 to the DALI bus, which creates a drive current for the base of T1 that starts to conduct and short circuit the DALI bus via bridge B1.

But I understand just the opposite: when DALI1_TX is a high (3.3 V), the direct current through the optocoupler diode is zero and therefore, the optocoupler transistor is cut-off. Then, the base current of 'T1' is zero and the transistor is cut-off. What am I doing wrong?

The explanation for the reception (page 5) I do not understand correctly either. When the bus is idle, the 'OK2' optocoupler transistor is saturated and therefore, DALI1_RX is a low level. On the other hand, when there is a low level in the bus, the optocoupler transistor does not drive and DALI_RX is a high level. It is right?

Thanks.


texts: Common clock signal to several components over long PCB lines

texts:
How to drive a clock signal to 20 digital microphone. The clock is generated from FPGA and about 3MHz frequency. First mic's line 2cm and last one's 15cm away from FPGA clock out pin. Also all mics should be sync.

FPGA drive strength could adjustable, but can it still drive 20 mics at this distance?
I found some clock driver, fanout buffer and similar ICs. Can someone who has experience give me an IC recommendation? Also if i need, how to locate it in PCB?


texts: Protection diodes for Arduino pin passing current to +5V rail when powered down - what to do?

texts:
simulate this circuit – Schematic created using CircuitLab

In the circuit above, I'm using a resistor (R1) and a couple of protection diodes (D3 and D4) to keep the voltage on an Arduino pin from 0V to 5V as the input from the LFO varies from -10V to 10V.

One thing that did not occur to me until I built this in reality was what happens when the Arduino is powered down.  When the 5V rail on the far side of D3 isn't powered at all, but the +/- 10V is still applied at "In", the diode at D3 seems to be forward biased at all times.  It seems to be allowing enough current to pass to at least light up the "on" LEDs of the Arduino, whether or not it's actually booting.

I suppose the maximum amount of current that would be passed in this situation would be (10V - Vf- 1V)/1K, so less than 9mA.

Could that be problematic for the Arduino?  If so, is there a good way to prevent this?


texts:
Is there an easy circuit or IC that will convert negative voltage to positive voltage and retain the initial value? Context below.

I am trying to add a volt meter to my power supply using some old parts I have lying around. My power supply is two 2-12V channels, one positive and one negative. I have an adc that can take anywhere from 0 to 5v. To start, I have a voltage divider on my channel output to my ADC so that my max voltage on both channels is just under 5v. However, I don't think my ADC can take negative voltage. I only have one 7 seg display, so I am using a switch to decide which voltage I am measuring.

On my ADC there is a VCC, +VREF, and a -VREF. I have VCC coming from my rectifier and my VREFs are coming from my regulated output. Initially I was using the switch to swap both VREFs depending on the channel. For example, my positive channel would have +VREF on my regulated positive output, and -VREF would be ground. On my negative channel it would switch so my +VREF was ground and -VREF was my negative output. This would still provide up to a 5v drop to my ADC for measurement. However, it doesn't seem to work that way.

My theory is that the 5V VCC doesn't change, so when I switch to my negative channel, it becomes much more than 5V relative to my VREF. So I want to put a negative to positive voltage converter on my negative output so that the ADC will receive a 5v drop relative to the initial ground. I just have no idea how to do that and all google seems to give me are positive to negative converters. Any help is appreciated! Thanks!


texts: Difference between applying voltage, and voltage across?

texts: I'm confused about the two terms, when voltage is applied and across a certain element in the circuit.


texts:
What do you call the outlets/plugs/connectors that you plug servos into on a board? These things circled in the photo...

I'm trying to purchase these and have no idea how to find them.


texts: LM324 with arduino as a differentiator for phototransistor signal

texts:
I want to measure the rate of change of voltage with respect to time coming out of a phototransistor, and preferably amplify it at same time, as the change is not so significant. But lets just not making it complicated! I am totally a newbie! Is it possible doing it with Rail to rail op amps and arduino? Lm324 can do that?
If somebody can provide me with a schematic, it will mean everything to me.

Thanx


texts:
I am new to Altium Designer and electronics in general. I want to share my future Altium projects with others, for example, on GitHub. How I should organize a project to make it more "share-friendly"? So that anyone could simply download and use it, without any additional complications.

Of particular concern are library components. What if I use components from my own library in some project? Should I also share the library? Should I share separate SchLib and PcbLib or integrated IntLib? Maybe it would be best to create a project library from the schematic, as described in this blog post?


texts: I was curious if I could possibly strip the end of a USB cable, and direct audio traffic from the phone through the USB to a 5volt in p/n speaker, sub, or a tweeter. I haven't seen this done anywhere else online and I'm just curious if I could direct the audio out of the USB female port, vs using auxillery, considering I'm trying to make portable speakers, the auxillery output is just a wee too weak, and I can't always bring an amp with me wherever I go.


texts: What is the correct name for a footprint that connects to a panel mount component?

texts:
Let's say you have a panel mount switch. When you create the footprint for this switch, you aren't creating it for the switch itself, rather, you are making a footprint with holes for the wires that will be run to the switch on the panel.

So what do you call a footprint that isn't for the component itself, but for wires that will run to the component? It's driving me nuts not having a way to refer to this.

I've been calling them "interfaces" but it's a stupid name and just a filler until I learn the correct word. What are these types of footprints called?


texts:
Im glad to be with you. I have question about coupled inductors in altium. I want to make a flyback converter and tried first as in Image 1  . I converted 310V DC to 12V DC as you can see. I wrote spice model for T1(Transformer)

Then, I wanted to ascend my outputs as you see in the Image 4
But sim out came like in Image 5
For 3 output transformer spice code that I wrote

What is wrong?. I think 3 output transformer spice model wrong. But I didnt figure out. Give me advice please about that.

With my best regards...


texts: Construct OPAMP circuit for given inputs and output

texts:
Here is my task:

Construct circuit ??? which uses power supplies +12V and -12V and gives output voltage:

Here is circuit:

I solved it using 4 opamps:

First opamp scales V3, second integrates V4, third sums the results of the prior two circuits and fourth inverts signs in sum (output of third opamp).
Can this problem be solved using single opamp?


texts: Which pull-up resistors to connect when microSD is interfaced in 1-bit data bus width mode (SDMMC, STM32)?

texts:
I am going to interface a microSD with STM32H7 (via the SDMMC interface).
The SDMMC supports either 1-bit or 4-bit data bus width.
If I use the 1-bit mode, do I still need the pull-ups on D[3:1] signals or can I use the pull-up only on D0 and CMD signals?
Thanks!


texts: How can I code in a buzzer while using a 7-segment in an 8051

texts:
I'm currently working on a small queuing system where whenever someone presses a button (which I have linked to INT0), my 8051 would increase the register and would display a higher number on the dual digit 7-segment.

As an example. If the 7-segment is currently displaying 76, if I press the INT0 button, the number on the 7-segment would increase to become 77.

I have already finished the above mentioned parts when it comes to coding and hardware, and I believe that they work bug free. I would now like to add a buzzer, so that whenever the INT0 button is pressed, the number on the 7-segment would increase and the buzzer would play a sound.

From what I've studied so far, I've written the following code to play a sound with the buzzer:

PLAY_SOUND:
    MOV R1, #50
MI_L1:  MOV R0, #21
MI_L2:  MOV TH0, #HIGH(-379)
    MOV TL0, #LOW(-379)
    SETB TR0
    JNB TF0, $
    CLR TR0
    CLR TF0
    CPL P0.0
    DJNZ R0, MI_L2
    DJNZ R1, MI_L1
    CLR P0.0
    RET

The following is a partial code of how the system should interact together

.
.
.
;---------------------------------INT0 ISR-----------------------------------
ORG 0003H               ;Starting address for the ISR (INT0)
LCALL PLAY_SOUND
LCALL INC_7_SEG         ;Increase the 7-segment count
RETI
.
.
.
;-------------------------------SOUND SUBRO---------------------------------
PLAY_SOUND:
    MOV R1, #50
MI_L1:  MOV R0, #21
MI_L2:  MOV TH0, #HIGH(-379)
    MOV TL0, #LOW(-379)
    SETB TR0
    JNB TF0, $
    CLR TR0
    CLR TF0
    CPL P3.7
    DJNZ R0, MI_L2
    DJNZ R1, MI_L1
    CLR P3.7
    RET

The above code works somewhat fine, as in, whenever the button in INT0 is pressed, the buzzer would play a sound, BUT, while the buzzer is playing a sound, the 7-segment turns off. And then the after the buzzer is done, the 7-segment increases it's number.

If it is of any help, here is the schematic of the circuit I've made so far:

How can I make the buzzer play a sound, without the 7-segment turning off (momentarily) using my current setup?

I can provide the full code if I need to, but its about 350 lines long.


texts: Trying to find Vo in this circuit diagram

texts:
I am pretty lost working this textbook example (not homework).

Will someone verify if I did this correctly?

1) simplify the circuit

1a) \$20\text{k}\Omega + 40\text{k}\Omega = 60\text{k}\Omega\$

1b) \$60\text{k}\Omega \parallel 30\text{k}\Omega = (60\text{k}\Omega \times 30\text{k}\Omega) / 90\text{k}\Omega = 20\text{k}\Omega\$

1c) \$20\text{k}\Omega + 20\text{k}\Omega = 40\text{k}\Omega\$

Resulting in a collapsed circuit with just the 12V source and a \$40\text{k}\Omega\$ resistor.

Is this even the right start?  It appears that with this simplified circuit \$V_o\$ would just be 12V.  What did I do wrong?  The answer is 2V.


texts: Logic Level Converter for Negative Voltages

texts:
Here is logic level converter mostly used for converting signals between 3.3V and 5V. (Other positive levels such as 1.8V are also possible). What if I want to convert from 3.3V to -5V logic (negative!)? It doesn't have to be bi-directional. Could we use a P MOSFET instead? And how the schematics would be?

NMOS example for positive level converter:


texts: Is there any CC Led Driver IC that has common GND between led cathode and VIN-?

texts:
I have a project that has as 3W (using 500mA) Led and an I2C sensor at the end of a cable, and I need 6 wires for it. (4 to the I2C sensor) and 2 for the led.
I’m using the PT4115 CC led driver CI, but LED- is not GND, so I need two wires from the driver to the led at the end of the cable.
But I want to use a 5 wire cable, to use standard micro USB 5 pin connectors to connect this cable to the control box.
I’m searching for another led driver PWM capable IC that has a common GND at the led cathode, so I can share  the same GND pin I use for I2c, but so far no luck...
Does anyone know of any SOP pwm capable led driver ic for a 3W led that has a commom gnd?
Or a way to get around this, in a power efficient way?
My Vin for the led driver is a 7.4V battery, and an attiny85 at 5V controls it’s pwm and the i2c sensor (proximity sensor).
I actually did find and tested a CN5711 IC (but in a separate module, not in my circuit) that has a common GND, but it heats a lot at 500-600mA...
The PT4115 with the proper inductor stays cool with no need for heatsinks... my enclosure space is limited in hight, so a heatsink is a problem if needed...
Thanks!


texts:
simulate this circuit – Schematic created using CircuitLab

I've been calling this push-pull but apparently "push pull" is another name for totem pole now.


texts:
I am calculating transfer function with some parallel caps in the circuit, same ones.
I have parallel 4 capacitors with 100 microF each then total capacitance is 400 microF and it is presented as

\$ Z_{tot} = \dfrac{1}{s \cdot 400 \times 10^{-6}} \$

But if I calculate it this way then I got different result:
One capacitor:

\$ Z = \dfrac{1}{s \cdot 100 \times 10^{-6}} \$

4 caps in parallel:

\$ Z_{tot} = \dfrac{Z \cdot Z \cdot Z\cdot Z }{Z + Z + Z + Z} = \dfrac{Z^3}{4} = \dfrac{1}{s^3 \cdot 4 \times 10^{-12}} \$

which is totally different result, and wrong I guess, but I don't see where the error is...
I would appreciate some help for this basic question.


texts: How to prevent Current Limiting Circuit failing short?

texts:
I am utilizing what I believe to be a fairly typical current limiting circuit at the input of a DC/DC converter.  I am driving the converter from a battery so I can never exceed a certain current or I risk damaging the battery.
The limiter is based off a recommended circuit from Art of Electronics. In the case of a short circuit at the load I have found that the limiting transistors dissipate a very large amount of heat and fail short.  Thus, the input current to the converter exceeds the rating of the battery. Is there a common way to make a current limiter that does not fail short?


texts: Are batteries suppose to show open or shorted across the taps from positive to negative? I have 20 or so 1.45v 265 ah SAFT batteries that show half of them open and half shorted.


texts: How are circuits which use complex ICs normally simulated?

texts:
I understand that it is common practice in electronic design to simulate a circuit in some spice program before building it. Sometimes a project requires the use of complex ICs, for instance an IC which performs charge control for a Li-Po battery or an IC which acts as PWM controller. Manufacturers generally don't make spice models of these sorts of complex components available. I would like to find out from any electronics engineers/designers what they do in this situation. How do you simulate such a circuit? Or is it more a case of working with the manufacturer designs provided in the application section of the datasheet and trusting that the designs will work. Maybe you abstract these ICs and simulate other portions of your circuit with the kind of output signal they would provide?

I would appreciate any real world practical examples from your experience in electronic design to illustrate how you approach simulation of circuits which make use of off the shelf ICs which do not have spice models available.


texts: General Question about Coil wrapped around a transformer core

texts:
I had a doubt about how inductance of a wire is calculated if it is wound around a iron rod, and when its wound around a transformer core.

Case 1 : Considering an iron rod at first , or in other words an electromagnet.

NOTE: Please Ignore the voltage supplied in the images below. For our case I am just asking about a simple coil wrapped around an iron rod without any voltage applied.

Now here flux lines will flow from bottom to top(in the iron rod), and will turn around and flow from Top to bottom(outside the iron rod) to complete the closed loop.

In this case Inductance can just be calculated by using the standard equation

Now My question is in the second case:

Case 2: When the coil is wrapped around the Transformer core.

like in this image(IGNORE the voltages applied) :

Now how is the inductance of the coil calculated ? Do we still use the general equation of the inductance or do we use the entire length of the transformer core for our calculation ?
NOTE: Ignore coil 2 in the image above.


texts: Using a single push button to start/stop a motor

texts: Is it possible to use a single push button with a N/O and N/C contact on the back to start and then stop the same motor using only relays. The button will be pressed and the motor runs until the button is pressed again which will stop the motor ?


texts:
I want to use this(data-sheet) electromagnetic relay given this pin-out:

But from its data-sheet I couldn't figure out whether it is normally open or normally closed. It doesn't write it explicitly.

So I have some questions regarding the data-sheet:

1-) Is this a normally open relay? What indicates that?

2-) There are also the following parameters:

What is limiting continuous current? Does that mean the relay will open if the continuous current exceeds 6A? I also don't underrated what it means for 10A in parenthesis. All 13 14 and BB bridged?? The sentence is not so clear.

3-) How come can this coil draw only 18mA at DC. I though coils have high resistance for AC voltages? Does that mean coil's DC resistance is 1.3k? Data-sheet also does not mention any peak current for when the coil is de-energized. I thought the coil will have some high current during entering to off state.

4-) Can I use this relay for application rated for nominal 10A?


texts: TRIAC can be connected in series of 230 V. Shall I use mutivibrator for giving gate triggering this TRIAC? Also, how can I turn off this triggering by giving an external signal?


texts: Is flash chip capacity really limited to the powers of 2?

texts:
I have never seen any flash chips with capacity not confined to the strict (i.e. not like in hard drives) power of 2. I wonder what prevents manufacturers from creating such chips: is it some engineering reason, or just the marketing, or anything other?

I've came to this thought after examining some flash drives: the NAND flash inside is, for example, 8 GiB, and the drive itself has a size of 8 GB. Looks like the difference is used to compensate errors which appear quite often in MLC NANDs by replacing bad blocks with spare ones.

For example, plugging an SD card labeled as "512 MB" into my Linux box produces the following message:

sd 12:0:0:0: [sdb] 996352 512-byte logical blocks: (510 MB/486 MiB)

It is not formatting nor partitioning overhead: the full size of the device itself is much less than 512 MiB.

Also, I'm aware of the out-of-band (OOB) space present in all (MLC) NAND flashes. I don't consider it as "extra" or something because:

It is almost always used to store the ECC codes and not the actual data; hence, the amount of information is same with or without OOB.
The count of pages and blocks in entire flash is still power of 2, and moreover, amount of bytes in data and OOB areas of page on their own is power of 2, too. While the latter may be very well justified by minimizing overhead of addressing, the former is puzzling for me. We already have RAS and CAS, with one's address space bigger than other, and the matrix is already asymmetrical — why do it exactly in the power of 2?

So, what prevents a vendor from adding a bit more rows or columns? I'm mostly interested in NAND flashes, as they have an unified 8-bit address/data bus, and the number of bits in the address does not really matter (unlike for NOR ones).


texts:
I am trying to solve the attached practice problem from Hayt's 8e of Engineering Circuit Analysis but I am struggling to find a solvable differential equation for the circuit.

I am trying to use KVL to derive the DE, but I can't find an expression for the voltage across the dependent current source. Can anyone help me out?

I've also attached what I have so far.


texts: STLINK V2 disconnects in the STLink Utility

texts:
I have some strange behaviour of my STLINK V2 when I just plug it in the USB port and then open the STLINK Utility tool. When I then go to settings it finds the STLINK V2, but after about 5s the program seems to hang and the serial number disappears and it says "Old ST-LINK firmware / ST-LINK already used"

I use windows 10 and the most recent drivers for the STLink and the windows 10 drivers (STSW-LINK009). The STLink is just plugged in and the SWD interface is not connected to any device.

Has anyone an idea why this error occurs and how to fix it?


texts:
I'm playing around with E-ink displays and I have a project in mind that would have to subject the display to extremely high temperatures (around 110 degrees Celsius). The display does not have to be operational during exposure but afterwards should hopefully operate.

My question is what would happen to it in theses temperatures? I couldn't find anything online other than that it's operating temps are from 0-50 degrees but I'm more interested in it's limits before it gets damaged. Would it react similarly to how an LCD would react? Will the display it self start to melt, pixels evaporate? I have no clue but any ideas would be really helpful, thanks.


texts: Input Bias Current in an OP-AMP and its value in a datasheet

texts:
Yes,i have seen all those similar questions of this topic and I am still confused about few concepts.So far i have been taught that an simplified OP-AMP circuit  looks like this--------------

So,thinking about input bias current in that circuit here are some confusions-------
1)In a Youtube video i was told that input bias current enters/leaves from both inverting and non-inverting terminal at the same time...and they are equal,How?
2)In an OP-AMP datasheet we have only one value of Input bias current----
But what if the source voltage changes along with the source resistance in that term the bias current also has to change(Below is my note,about what i mean to say)-----

So,we should have different values of input bias current but why only 1 value of input bias current is given in the datasheet?


texts: How to generate schematic visual from Gnucap / Spice files

texts:
I am looking at the circuit diagram from here

The gnucap description for it is given as
C1 0 2 1UF
R1 1 2 1K
R2 0 2 1K
Vin 0 1 AC 1
.OPTIONS PHASE=RADIANS
.PRINT OP V(Vin)
.OP 0.00 100.00 BY 10.00 BASIC
.END

I can run the simulation on this using gnucap fine, see output. But is there a way to generate the schematic visually from just the textual description above using a simple command line tool?


texts: Can I use Vreg output to power AD805 current sense amplifier? Is there apower restriction?

texts:
I am using an LTC6811-2 battery monitoring IC for monitoring a battery pack. I am also using an AD8205 to sense the current between battery and load.  To control both ICs, I am using an STM32F401 microcontroller. I am using a 36V nominal 2500 mAh battery pack. Its maximum voltage is 42V.

Microcontroller power consumption:

supply voltage : 3.3v
input current : 160 mA max

AD805 (current sense amplifier ) power consumption :

supply voltage : 5v
input current : 20 mA

Since my microcontroller input supply voltage is 3.3V, I have used a buck converter to buck the voltage from 42V to 3.3V to give as an input voltage to my microcontroller.

The problem is the current sense amplifier supply voltage is 5V. I cannot use one more buck converter to get 5V again it will end up in more components and power loss.

Can I use the regulated output of my battery monitoring IC to power my current sense amplifier. In the datasheet of my IC is given like.

It is given like Vreg pin is used to power the internal SPI and ADC converters, but in my design I am giving the power of SPI through 3.3 v of microntroller. This is also mentioned in the datasheet.

Since I am not using Vreg output pin of my battery monitoring IC to power my SPI. Can I use it to power my current sense amplifier so that I can reduce the component count and reduce the extra power consumption. Like this:

Is it possible or should I go with the current sensing amplifier with 3.3 v as input voltage?

Please find the attached data sheet of battery monitoring IC : enter link description here

Current sensing amplifier datasheet:enter link description here


texts: Switch from electolytic to ceramic capacitors in car ECU?

texts:
I'm looking into replacing the capacitors in the vehicles ECU. I know the ratings and voltages for the three. My question though is which would be better to go with, electrolytic or ceramic. I'm not worried about price of the caps just would like to know which would be the most reliable and will last.

The capacitors are:

22µF 50V
47µF 50V
100µF 25V

Also if it helps it's for a 1996 Mitsubishi Galant VR-4 RHD.

I've read through Can I replace all electrolytic capacitors with ceramic ones? but didn't really answer my question unfortunately.

Thanks for any help.


texts: What is the purpose of this solder jumper?

texts:
I've been studying the schematic of an audio modem, which takes/sends data as audio signal over an audio jack via FSK encoding:

Does anyone know what the solder jumper SJ1 is supposed to do? My reading is that it's a 3-way jumper, but shorting all 3 pads would effectively short the MJ-2135's pins 1 and 4. Shorting SJ1's middle and bottom pads effectively produce nothing more since MJ-2135's pin 4 is already in parallel with R5.

Am I missing something?


texts: Leads of a particular electrical component

texts:
Is lead the most common term used in electronics to indicate the number of connectible input/outputs that a component has? Are there other terms that are used interchangeably with leads?

Are there different qualifications for the type of lead it is? For example, ground would have something like one input lead but zero output leads, whereas a resistor might have two leads that could be almost interchangeable/symmetric in that they both accept incoming/outgoing directions, whereas a transistor/diode has specific leads with specific properties. In other words, is there something like a glossary or something of all the different lead types or how 'connectable areas' of a component are defined?


texts: Port A digital output set up on pic16lf1827

texts:
I am having difficulty moving my code from port b to port a on pic. I am looking at adc disabling and also comparator disabling, but not having much joy. Anyone see what I'm doing wrong?

void init_pic(void)
{
    //OSCCON = 0b01101000;

    TRISA<4:0>=0;
    TRISB=0b00000000;       //set up for I2C and USART, plus ADC input on AN9 (RB3)
    ANSELA = 0b00000000;    //all digital outputs
    ANSELB = 0b00000000;    //all digital outputs
    ADCON0 = 0x0F;          // All digital inputs
    ADCON1 = 0x0F;          // All digital inputs

    CM1CON0 =0X07;
    LATA = 0b00000000;
}


texts:
I have a 4 layer board, with Power and Ground being the inner planes.
I have a component which connects to the netlist AVDD
The power plane has:

Net: AVDD=POWER

Layer/Colour: Power

Boundary: Default

Relief: RELIEF

Type: Solid

Clearance: 10th

With boxes Relieve Pins and Supress islands both checked

I connect a via between top copper (component side) and Power:

From: Top Copper

To: POWER

Style: DEFAULT

Net: NONE

This via does not connect to the AVDD on my component - why?


texts: Does a generator produce voltage or current?

texts:
I know that this question might sound very stupid for +90% of you, but my brain doesn't really get the electricity generation.

The thing that I don't understand is what does a generator produce, voltage or current when it spins? Sometimes I see that a generator can produce x amount of potential and y amount of current.

I'm starting from the basics of electricity. A spinning/moving magnet makes the electrons move in one direction, generating a potential due to the change in kinetic energy, right? So if one would connect a multi-meter at both terminals, one would read the voltage. I did this and it's easy to comprehend. Now things start to confuse me.

Sometimes, one can see on the specifications that a motor can deliver a certain current and this is what I don't understand. The current is related to the potential through Ohm's law, right? In other words, the current is dependent only on the resistance of a load (or wire) and the potential. Also, the current flows only if there is a voltage gradient/drop. Why is there the current specified on generators like this one?

What confuses me is this intrinsic combination of voltage-current on the generator. Can anyone help me to understand this? Thank you and sorry for dropping the IQ of this group.


texts: How to get an output of 100V from a 3.3 V pulse waveform?

texts:
We have a problem when trying to drive a piezo transducer(the output of microcontroller is a 3.3V pulse, but the piezo works around 100V-300V, so we have to convert the 3.3V pulse to 100V pulse).

Does anyone has any idea about how to design the circuit? And how to design the protection circuit between the 100V drive voltage and the small voltage received by the transducer?


texts: Determining Open Loop Gain of an opamp in LTspice

texts:
I'm trying to extract two characteristics: "Input Offset Voltage" and "Open Loop Gain" of an opamp LM741 by using LTspice.
To do that, I use the following circuit model and plots where the horizontal variable is the input voltage Vin between -2mV to +2mV:

To see the Input Offset Voltage I check the value of the Vin when Vout is zero in the middle red plot. This is roughly around -0.99998mV.
So I conclude this is the Input Offset Voltage.

As you see in the top plot, the gain which is Vout/Vin changes(from zero to a crazy big number) dramatically. Isn't that supposed to be a constant huge number? (edit: Okay this is because of division by zero). But gain is changing in linear region as well see the second plot below.

But how can the "Open Loop Gain" be determined in a similar way?
Should the "Input Offset Voltage" be used when finding this as well?

Here is only focusing on linear/amplifying region and the gain is still dramatically dependent on the input voltage:

Why is the gain not constant? I was expecting a huge almost constant number as the open loop gain.


texts: Dyson keeps going on about their new "digital" motor. What is a digital motor? How can a motor be digital, if it is inherently analog? Is it just marketing doublespeak?


texts: How to use the Root Locus design method to improve the transient response of my system?

texts:
By closing the loop, I need to design a controller in the feedforward path to minimise the effects of the two pairs of dominant poles of the 5th order transfer function. Use a pole-zero cancellation technique on a root locus diagram and if need be introduce  an integrator to eliminate the steady state error. Proceed to determine a suitable gain K that satisfies the following design specifications:

Less than 5% overshoot
Less than 2s settling time
Steady State Error Minimized

From the above performance requirements, I calculated where the closed loop poles should be:

desired_poles = [-2.6 + 1i*2.39, -2.6 - 1i*2.39, -100, -120, -110];

My 5th order system is defined as follows:

num = [0.0001 10];
den = [0.005 5 0.66 61 2.1 10];
tf = tf(num, den)
[A, B, C, D] = tf2ss(num, den);
e = eig(A)
sisotool(tf);
step(tf);

where:

e =

   1.0e+02 *

  -9.9990 + 0.0000i
  -0.0004 + 0.0347i
  -0.0004 - 0.0347i
  -0.0002 + 0.0041i
  -0.0002 - 0.0041i

and the step response is :

and using sisotool() I get a different step response:

and zoomed in with design requirements inputted/ I am unable to come up with any form of compensator which does not result in the two rightmost poels going unstable:

For example, if I add a lead compensator with a real zero at -2 and a real pole at -5 I get a reshaped root locus which passes through the desired area. However, the two furthest right poles will immediately go unstable as soon as I start moving the other poles around.

I am now trying to determine which compensator is needed to achieve the desired results.

Going through MATLAB official docs, the process seems to involve trial and error inside the sisotool() app.

How can I design a compensator to give me the above poles which yield desired results?

Any help is appreciated.


texts: Motorbike turn-signal blinker starts OFF, I want it start ON

texts:
I bought a cheap blinker that claims to be good for LED bulbs (so the frequency is independent of the load.)

It is true, but it has a flaw: the lamps go ON only after about a half second from when I turn the switch, which I don't like at all. I want my turn signal going immediately ON and then blink.

I opened the blinker, and this is what the schematic looks like:

Falstad circuit simulator

I used Falstad to try and understand the circuit and get a solution myself before asking - without result.

How could I modify the circuit so the lamp starts ON?

Please note that I have no other wiring other than what is represented: I have no a "pure" ground wire, just the + and the wire that goes to the handlebar switch.


texts: Protected 3.7v battery as replacement for 3.8

texts:
I have a set of bodycams that need replacement batteries, and i cannot find anything suitable short of 400 quid to send them back to manufacturer. At that price i might as well spend the extra 100 and buy new ones.

The originals are 3.8v, 2000mah x 2 bagged cells at 45mm square.

Can i replace them with protected 3.7v cells and trust the protection board to prevent overcharge?

I would assume the cameras would only read 90% battery when full and try to continue to trickle, but will the charge profile ruin the replacement cells, or worse release the magic smoke?


texts: What's the use of a decoupling capacitor near a reservoir capacitor?

texts:
I've seen some circuits where a decoupling capacitor is used as well as a reservoir capacitor, like this (C4 and C5):

I've read about decoupling capacitors and for me it looks as if they are meant to remove small fluctuations in the supply voltage. Then I thought - wasn't that the purpose of a reservoir capacitor as well? Why wouldn't the reservoir capacitor be able to filter out the small fluctuations, if it is able to filter out the large fluctuations?

So I feel like I have a basic misunderstanding here. What is the purpose of a decoupling capacitor next to a reservoir capacitor, when we assume we place both equally near to the power consuming part? Or is the only advantage of the decoupling capacitor that it is smaller and can therefore be easily placed more near to the power consuming part?


texts: Why doesn't a boost converter help overcome USB cable resistance?

texts:
I ran a long USB extension cable from my pc to a WiFi adapter. The cable was too long and the gauge was too thin. So the resistance made the voltage drop to ~3V under load, making the WiFi adapter disconnect. To overcome the voltage drop, I devised this:

I snapped the USB extension cord's power cables (the data cables were kept intact) and ran them through a 0.9-4.5 to 5V boost converter capable of handling 1 Amp at input (the WiFi adapter takes 300mAmp max at 5V as measured by USB doctor.)

Now one would think that this setup would work. Kind of like voltage stabilizers that step up low.voltages of household. But it didn't work. I can't find out why. Whenever the WiFi adapter kicks in, the input voltage drops to 1.5V and the booster can't keep up with the power demand. Why is this happening? The same principle is used for stabilizers of households where the voltage is low. So why don't stabilizers trip like this USB booster is doing?


texts: How do you drive a variable reluctance stepper/SRM as a generator?

texts: I think I understand the principles, even if not the details, of operating a VR/SRM as a motor. But I don't understand, and can't find any good explanation online of, the principles for how to use one as a generator, just statements that it can be done. What kind of signal would you drive it with, and what kind of output would you expect, operating this kind of motor as a generator?


texts: How to produce electricity with mechanical power/spring coil

texts:
As a home project I want to make a electricity generator which uses a spring coil, which when turned/wound(just like the mechanism in wrist watches) enough times will start unwinding and generate power small/large enough to power a small bulb/ night light / LED.

The entire assembly should be handy/easy to carry around.

Can you guys give some ideas? some online DIY project reference ?

Pls feel free to add/remove relevant/irrelevant tags.


texts:
I followed this tutorial and got the following error when trying to compile upload the attiny85 sketch:

avrdude: usbdev_open(): did not find any USB device "usb"

The attiny is already soldered on a circuit (with two leds, a buzzer, button and a brightness sensor). Can this cause the error?

Also, the attiny already has a program on it (that I want to overwrite) so I assume I don't need to install the bootloader?

I found two files with the attiny hardware files, one that adds ATtiny85 (w/ Arduino as ISP) and one that adds ATtiny 85 (internal 1Mhz clock) to the Board menu. When using the first one (Arduino as ISP) i can only compile the blink sketch when I add

#include <Arduino.h>
#include <wiring.h>

otherwise it says "OUTPUT" was not declared in this scope.

UPDATE: Tried it with setting programmer in the tools menu. I changed it to Arduino as ISP. The error is now a different one (with upload as well as upload using programmer):

avrdude: stk500_getsync(): not in sync: resp=0x00

- Board: ATtiny85 w/ Arduino as ISP
- Programmer as ISP
- COM port correct (I also tried the other one)

Sometimes I get this error (only with normal upload), which indicates a successful upload according to the tutorial, but the ATtiny still performs the program that was installed before.

avrdude: please define PAGEL and BS2 signals in the configuration file for part ATtiny85
avrdude: stk500_program_enable(): protocol error, expect=0x14, resp=0x50
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51


texts: How do I determine if I can safely substitute potentiometers?

texts:
I've got a number of audio projects on the workbench, and of course, each of them requires different potentiometers. Instead of waiting for another box o' parts to arrive, can I substitute? What are the rules of thumb for that? While my first inkling is that it'd be the same as a regular resistor (e.g, 5-10% is generally close enough), I've been second guessing and, well, have confused myself in that thought experiment. I've never ~noticed~ tolerance ratings on pots, but that doesn't mean they're not there.

So within what ranges can I safely substitute? 10k for 20k or vice versa? What'd happen if I subbed a 500ohm for a 100k? Looking forward to some guidance!


texts: Using a 670Kv outrunner motor, how can I calculate a way to get variable low speed and high torque?

texts:
I have an E-flite Power 46, 670Kv outrunner motor (Kv is the shorthand for RPM/volts, it has 3.9A idle current, 40A maximum continuous current, 14.4-19.2 voltage range, 925 watt maximum) but I wish to use it for a low-speed robotics application where I don't need more than 100 RPM and I want as much torque as (cheaply) possible. For any other motor type I would simply attach a gearbox, but I can't figure out the reduction ratio that I need.

If I run it at 20V (round up for simplicity), that would be 13400 RPM, so I'd attach a 120:1 gearbox and that would be close enough to 100 RPM. However, that's 13400 RPM unloaded; the gearbox will be a load and the robotic parts will be a bigger load, but I can't find anything that specifies how much the speed will change based on load. So where/how can I calculate, estimate, or even dead reckon that?

Additionally, I'll usually want to run the motor at much lower speeds, but I've not found anything saying how much torque is available at those lower speeds - most of the stuff I've found just implies that constant voltage into the motor will mean it has constant power, and thus it will provide whatever torque is needed to deliver that power. But with 925 watts, if I want to get 5 RPM out of the motor, the formula "Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488" says I'll get 1575.55 Nm - which seems like a ridiculously high number compared to similarly powered gearmotors (and in this case, the motor isn't necessarily geared). It seems unlikely that the motor (without a gearbox) could run at 5 RPM, so there must be some minimum operating speed for the motor. Is there any way to find or calculate a minimum speed for the motor, perhaps depending on load and/or voltage?

Also, I intend to run this off an AC->DC converter (variable voltage and current, up to 10A 30V, but I can get large constant-voltage converters cheaply), and I do have the ESC. I'm not certain if that power supply makes a difference - such as if a battery is better at handling rapid changes in load. I could add capacitors or batteries into the system, but it is a lot easier to handle and test the system if I don't need to worry about a battery running low.


texts:
Below is a question in my homework:
\$F(P,Q,R,S,T)=(P+Q)S+(R+T)\bar S\$ using one or more 2x2 AOI." />

Here's my attempt for (a):

Step 1: simplify boolean expression.
\$F(P,Q,R,S,T)\$
\$=(P+Q)S+(R+T)\bar S\$
\$=PS+QS+R\bar S+\bar ST\$
Step 2: expand boolean expression so that it fits into the AOI gate logic:
\$F=PS+QS+R\bar S+\bar ST\$
\$=\overline{\overline{(PS+QS)+(R\bar S+\bar ST)}}\$
\$=\overline{(\overline{PS+QS})(\overline{R\bar S+\bar ST})}\$

I want to know:

Do I continue manipulating the boolean expression, or can I just implement the result from Step 2 with AOI gates?

Is this double-negate manipulating method suitable for implementing boolean functions with AOI gates (or maybe even all gates in general)?

Any guidance is appreciated!


texts:
Skin effect of metallic conductors is well documented.

What about SMD resistors?
High values Vs low values? Above what frequencies would this be an issue?