texts: Reverse current from motor driver causes buck converter to shut down

texts:
I am using a TPS53319 (datasheet) buck converter to generate 5V 10A to supply H-bridge motor drivers and RC-servos. I am using this schematic which is based on the datasheet example and a TI Webbench design:

R13, C15 and C14 are needed when using a ceramic output capacitor with a low ESR.

The regulator works well during constant load, but when the motor driver switches off the motor, the current from the motor inductance gets dumped into the capacitance across the 5V net, increasing the voltage. The regulator has an overvoltage shut down function, which is activated when the feedback pin reaches 120% (0.72V) of the 0.6V target voltage.

I can keep the voltage on the 5V net below 120% (6V) of the 5V target by using a zener or TVS diode. However, there is an AC-path from the 5V output to the feedback pin (C14 & C15), which causes the quick voltage rise on the 5V net to be better coupled to the feedback pin than it would be with the voltage divider (R14 & R15) alone, as can be seen on this measurement:

The blue trace is the 5V output voltage, the yellow trace is the voltage at the feedback pin. The output voltage rises to only 5.32V (106%) but the feedback voltage exceeds 0.72V (120% of the target), causing the regulator to shut down.

I have thought about and tried a few possible solutions, but I haven't found one I am happy with yet:

Using a diode to prevent any current flowing back to the regulator. This works but is not an option, as a lot of power will be burnt in the diode at 10A.
Tried modifying the feedback circuit to get rid of the AC-path, but no success so far. I don't think this is possible without impacting the stability of the regulator.
Increasing the ESR of C16 with a 30mOhm series resistor to be able to get rid of R13, C15 and C14. I think this should work, as it satisfies the stability requirement from the datasheet but for some reason it was not stable?

Does anyone know any other possible solutions? Board space is very limited so it is only possible to use few and small additional parts.

Thanks


texts:
I have 10v output and analog input, i dont have constant current source 1ma or dont want to use whetsonebridge circuit, my question is can i read rtd sensor output with pull up resistor Xk, if yes what must be value?
Thanks


texts: How do I know if which leg is the emitter or the collector? (Transistor)

texts:
I'm new to electronics and here's a newbie question that I would like to ask:
How do I know if which leg is the emitter or the collector in a Transistor (For both PNP and NPN) using only an analog multimeter?


texts: Android Tablet Side Connector Interface Information

texts:
I'm not sure if this is on topic or not, but I'm trying to find out about the interface found on the side of some Android devices. An example can be found by side of the "pipo n2" device. It appears to consist of two groups of six pin receptors.

Is this a standard interface for Android devices?
Does this type of interface have a generic name?
Is the pinout published for this interface?
Are there standard docking stations available which utilise this interface?

Any help greatly appreciated.


texts: Verilog: Check, if a signal is 100 ticks active?

texts:
I have one input and one output. And I want to turn the output to 1, if the input was 100 ticks active (100 cycles).

module check_100(
   input wire clock,
   input wire reset,
   input wire in_a,
   output reg out_a);

reg[10:0] counter;

always @(posedge clock) begin
    counter <= counter + 1;
    if(in_a && (counter == 100)) begin
        out_a <= 1;
    end
end

But it doesn't seem to work properly.
Is this a good way to check, whether a signal is 100 ticks/cycles active or not?

Thank you! :)


texts:
I have a set of Samsung home theatre system. The Samsung DVD player is no longer working. I would like to get a new amplifier and reuse the 5 existing Samsung speakers.

But the existing speakers are all labelled 3Ω and the new amplifier is labelled 4-16Ω (1200W).

It seems that the speakers (3Ω) has lower impedance than the amplifier (4-16Ω). I worry the amplifier will be toast. But two different online shops confidently  told me they can be paired.

I have watched many YouTube tutorials about amplifier-speaker matching but still in the mist.

Can someone please give me a little advice? I really appreciate. Thanks.

BELOW: The new amplifier rear label. It’s 1200W.

BELOW: Specs of new amplifier.


texts: Suppressing contactor coil inrush, is this possible?

texts:
http://www.kvc.com.my/EnterpriseChannel/SharedResources/Datasheet/0/?ProductId=1000066755&Filename=SCHNEIDER-LX4-FH024.pdf

I am trying to operate a 24VDC coil with an inrush of approximately 30A, and a holding current of only 250mA. To avoid needing a 750W supply for a holding current of less than an amp, I attempted to use a 4 ohm thermistor to suppress the inrush current down to about 5A and allow me to use a much smaller 250W supply.

Unfortunately I'm thinking this might've been flawed logic. I was thinking the trick was to simply suppress the inrush current, but now I'm thinking maybe that inrush current is critical to closing the contactor. I tried testing the circuit as designed, but the contactor is not closing. The thermistor worked in the sense that my 10A breaker is not tripping, but I can not operate the coil. My assumption is it is not getting enough initial power to close.

My question is, are coil inrush currents something that can be suppressed? If so, I'm assuming there is a more correct way to do so as my idea does not seem to be functional.


texts: Strange powerplane layering issue in designspark

texts:
I'm trying to order a 6 layer PCB from a fab but they are asking me to resolve an issue with the file and I'm a bit stumped on what to do about it.

The second layer of the design I have designated as a power plane but I am also running a couple of short traces through it.

The problem is, when I output the gerber files of the PCB I get both a positive and a negative plot of the same plane.
In gerberviewer it looks like this with the negative plot

and this with the positive plot added

It seems to me that the positive plot is adding the copper trace to the power plane and the negative plot is adding the cutout around the trace, which means they are both neccesary, but you can't have a positive and a negative plot for the same plane.
What am I supposed to do here? Mistakes would be costly for me.


texts: Which standard is used to inspect stranded cables secured to PCBA with RTV?

texts:
Does some one know what standard can be use for quality inspection on a PCBA that have stranded wires soldered and fixed with RTV?
I check the IPC-A-610 Rev E and the most similar criteria, is in the section 7.2.2, but it is for Axial/Radial components.
This is the comment from the IPC standard:

On an unsleeved vertically mounted component there are a minimum of 2 beads of staking material for at least 25% of its length (L), and 25% of its circumference. Adhesion to the mounting surface is evident.

I might be able to adapt the criteria to stranded wires, but I am working in a medical industry and a standard is preferred, otherwise I'll have to validate it.
Thanks in advance for your support.


texts: Understanding a simple light bulb circuit

texts:
So I want to make a light fixture but I want to be safe and aware about all the details of my project before I just start plugging things in.

I have a light bulb and a light fixture that has two wires coming from it. I want to wire screw and electrical tape the bulb fixture wires to the lead and ground of a spare US male power cable that I have. Assuming I wire the lead and ground correctly can I just plug it into a wall socket or is the bulb going to shatter and am I going to end up with glass in my eyes?


texts: What does the word host in a host microcontroller mean?

texts: The MAX32664 family can communicate with several of Maxim’s optical sensor solutions (see table for details) delivering raw or calculated data, as required by the user application. This is achieved while also minimizing overall system power consumption. All versions interface to a host microcontroller through a fast-mode, slave I2C interface.


texts:
I am using PIC32MX350 series controller, on one GPIO , that is defined as input , and input that pin goes form one SMPS (PN : - PSC35 , IO Name :- AC out). Since SMPS IO is open drain we add a pull up and RC filter i between so it filter any noise that comes form SMPS which can couple to is IO.

Here on Normal condition SMPS AC output is 0, so my micro controller need to read 0, but we read 1 and before filter at point A on scope it read 0 volt with lot of noise peak, after filter at point B , scope read 3.3V constant.

here when i forcefully short point A to GND via some wire than uC read 0.

Uc Datasheet read low detect 0.15*VDD, so that makes 3.3*0.15= 0.495V. and gor High it need more than 2.5V.

q1) what if applied voltage betwwen 0.5 and 2.5V, than what uC read this input since its undefined state, is it read 0 or one. Or it may depend what internally pin is pulled high or pulled low inside the uC.

Also when i remove uC then at point B scope read flat 0 line with no noise peak.

Please advise


texts: Erratic outputs from a second order system when input is too small

texts:
I'm modeling a simple Mass-Spring-Damper system to represent the torsional behavior of a micromirror. With references to some papers (this one mainly), I've constructed the model of a torsional mass spring damper system.

Governing equation:

$$m\dfrac{d^2 \theta}{dt^2} + c \dfrac{d \theta}{dt} + k~\theta = T$$

Where T = Torque.

Calculated values (micromirror):

m = 3.61*10^-4 kg*um^2

c = 4.62*10^-3 uNums

k = 1.03 uN*um

The main issue I've been having is that below a certain input torque (~10^-6), my output seems to become unstable. I have shown examples of the good case (input is large enough), and the bad case (input is too small).

Input = ~10^-5

Input = ~10^-9

I'm stumped - I've been looking at this for a while without any solid grasp as to what is causing this to happen. I can increase the input by as much as I want and I will still see stable behavior, it is only at low input that this occurs. Any ideas what I could be doing wrong or neglecting?


texts: Why transformers Secondary magnetizing inductnace and Secndary inductace are Not Considered while doing filter calculation for output ?

texts: Why transformers  Secondary magnetizing inductnace and Secndary leakage  inductace are Not Considered  while doing filter calculation for output ? Why most  transformer datasheet  only mention  primary leakage inductance and primary magnetizing inductance ? Kindly elaborate the Role of Secondary leakage and magnetizing inductance in actual design .


texts:
Anyone got any super simple circuit designs for converting 1.5 V DC to 9 V DC?
Maybe something that uses a couple of transistors would be good?


texts: Coaxial DC power cable for switching AC adapter required?

texts:
Recently the DC cable from my AC/DC adapter to my laptop broke. I removed the broken section and it works again. Now the cable is too short for my taste and I would like to replace it. I heard from an electrician, that you should stick with the coaxial cable type (as it was used for the device, see picture below), saying something about the higher frequencies involved due to the switching-mode transformer. This is supported by the fact, that all major laptop producer seem to choose this kind of cabling.

So firstly I was wondering if that is true. After all, the output should be DC. Even if it contains spurious HF components, what would the coaxial cable help about it? Would using a "regular parallel cable" and a ferrite choke ring have the same effect?

Secondly I could not find any cable like this anywhere for sale¹. Do they have a special name under which they are sold?

¹ I was searching for "DC coaxial cable", "Laptop power coaxial cable", etc on DigiKey, ELV, eBay, Aliexpress, Reichelt and Conrad and found only either non-coaxial cables or RF-coaxial cables, but no high-current (4A) flexible DC coaxial cables.


texts: Plotting bode plot of the transfer function

texts:
two poles p1=1 and p2=25
two zeros are z1=100 and z2=origin
and the DC gain is 20log10(10)=20dB
I know that that the Dc gain Is 20dB which is a straight line with slope of 0 ,
The zeroes have 20dB slope, but I don’t know how to find amplitude of poles ( vertical positions) and and at what vertical position does the graph start ?


texts: Electrical power strips and current overloading

texts:
simulate this circuit – Schematic created using CircuitLab

Currently there is an extension cord that runs from the wall with 10kA. The current on the cord says 10 amps, 125 volts, and 1250 watts. The cord then plugs into a 6 outlet power strip. The power strip says 15 amps 1875 watts. The power strip has four plugs in it. There is an extension cord with 13 amps that plugs into a tape machine with 3.6 amps, 115 volts. There is a radio with 120 volts, 15 watts, .125 amps. There is a receipt maker with 4 amps and 120 volts. The final plug has an extension cord with a current of 13 amps that is used to plug in a 180 v and 77 amp conveyor. How much current is able to flow from the wall into the strip? I know the power strip is overloaded but I also want to know how much current is flowing out of each plug. Especially how much current is flowing to the conveyor. Any knowledge or insight on this subject would be appreciated.


texts: Converting a ground-referenced positive/negative dc voltage to positive voltage

texts:
I'm trying to create a circuit that converts positive or negative dc voltage into a positive voltage at the output. I can't use the conventional full bridge rectifer because my DC sources are not floating - they are grounded. Furthermore, I am unable to use a transformer to "float" my input dc voltage because it is dc. I'm currently looking into optoisolators or other galvanic isolators that may allow me use the full bridge rectifier.

Any ideas or other architectures to solve this problem are very welcome.


texts: How to make a MCU handles user applications without overwriting original program

texts:
At first, I am still learning and there is still long way to go. Please bear with me.
As far as I know that a standard single core MCU can handle single program.

But, I have seen some MCU's have a sort of default program running all the time and user can upload his/her program in order to make some additions or customization without dealing with the default program.

For example, I have come across a product has single MCU (ATXMEGA128D3). This MCU has a program on it. It runs all the time and communicate with many sensors. So far so good. The Product allows me to write code for my custom demands.
To do this, the Product provides with their libraries. It doesn't allow me to access to the MCU's peripherals/sensors explicitly but via some libraries.

So, when I am done with my programming I have very few lines of code. I flash it via PDI interface using Atmel ICE. It is quite straight forward.

Here is the code for a simple add-on;

#include "ApplicationIncludes.h"
static volatile word Counter;

static void Maint1000()
{
  WriteCStr(chMon,"\r\nHello World!");
  debugWrUInt("Counter",Counter++,-1);
}
static void Maint() {

}
void ApplicationInit()
{
  Register_Maint1000(Maint1000);
  Register_Maint(Maint);
  SetMonState(1);
}

This is the part I don't get it. I like to know how this is possible, how this is called and how I can use same way for my own applications?


texts:
I'm trying to make my workshop safer but I can't understand how electrocution happens.

For example, one hand is touching to live wire and neutral wire is not touched. If I know right, current flows from live wire to my body and to ground wire or earth but dry human hand's resistance is between 10-40k ohm so even my feet is touching directly to ground current is between 5.5-22mA and fatal dose is 30mA but how people get electrocuted from live wire without touching to ground or neutral wire?

Also can I measure resistance between live wire (or my hand) and ground? So I can get more accurate results.

I think I wasn't clear about my question : In my scenario neutral wire is insulated so current "have to" flow into ground , I understand my body's resistance not enough but floor or house have resistance too .

I made a small test for measuring resistance between my house and ground and I got three results :

1)One probe of multimeter connected to ground wire other probe connected to floor (I tried radiator too same result) multimeter showed more than 20M ohm resistance

2)One probe of multimeter connected to ground wire other probe connected my hand (feet touching to floor) multimeter showed 5M ohm resistance

3)One probe of multimeter connected to ground wire other probe connected to my left hand and my right hand touching to ground wire ,multimeter showed 200k ohm resistance

So only third scenario allows 1-2mA current other scenarios seem safe . if you see any mistakes in my tests please notify me so I can learn the truth.
Also when I making these tests I used special extension plug which only conducts ground wire other wires isolated from plug


texts: 3v wireless arduino and power consumption

texts:
I decided to create another post in order to get feedback for my ideas. I have created a network of wireless sensor nodes which connect to a central arduino with serial connection to a RPi.

I initially followed maniacbug's awesome post: https://maniacbug.wordpress.com/2011/10/19/sensor-node/. What do I want my sensors do at a first phase?

Connect to the base with an NRF24L01+ each
Temperature, humidity (DHT11 or 22)
Soil moisture
Soil temperature
Light
Battery voltage
Atmospheric/barometric Pressure

Right now I have connected the NRF24 and the voltage divider with the internal reference enabled (at 1.1V). I have also bootloaded the Mega328P with a 8Mhz bootloader for lower consumption. The circuit runs directly from two batteries (AA - 2.8V/2700mAh max) and the node sends data every 1 minute to the base.

When I tried to connect the DHT11 previously connected on an Uno board, I realised that it needs 3-5.5Volts which I don't possess and 3-3.3V is also necessary for other types of sensors. The ATMega328 works fine @8Mhz considering the manual from 2.4V and up. From a quick calculation and some tests, the battery voltage decreased 0.02V in a week. I haven't yet measured the current but I am willing to do so.

My choices are:

A voltage booster to 3.3V like this one
https://www.pololu.com/product/2561. I don't know what the
consumption will be but I suppose much higher than running the
battery directly to the board. It's also extra hardware, cost and
circuit size.
A bigger battery pack with 3(theoretically 4.5V) or 4 batteries (6V)
AA(2700mAh) or AAA(800-1000mAh): bigger size, more weight (not a
problem), the batteries run directly to the board, but the circuit
will need to shut down the sensor readings when the voltage falls
below 3V.
A 9V battery (200-280mAh) which is small and light in weight, but I
will definitely need a regulator which will consume also power.
Use a LiIon 3.7V battery. Higher cost, lighter weight and the need of a charger?
Find other sensors which work in the 2.4-3V range. Extensive research is necessary and orders that will usually take more than a month to arrive here. Yes, I am in the middle of creating something, I don't want to wait for ages ! :)

Please tell me your opinion. I don't possess deep electronics knowledge (developer) so don't just propose "create a booster, it's easy" !


texts: Multi-input AND gates from 2-input AND gates

texts:
To realize a 3-input AND gate from 2-input AND gates, we need 2 such 2-input AND gates. Assuming we have infinite supply of 2-input AND gates, can we obtain a general formula for the number of 2-input AND gates required to obtain a n-input AND gate?
Note that we have to minimize the resource usage.


texts:
I have a circuit of a USB chip (USB hub) with a custom external 24MHz oscillator. This oscillator have a max 3Vpp and the chip max voltage for XI is 2.45 with 1.8 recommended voltage.

What are the options to translate the output oscillator voltage? The simplest way is a resistor divider but a resistor have a intrinsic capacitance and inductance associated and XI may also not have an infinite impedance. Also found there are voltage translator chips but this means i also have to implement another 1.8V voltage rail and this is no option.

So, my question is what is the best solution?


texts: Why is there a capacitor and resistor added to this voltage quadrupler?

texts:
I'm not sure how to use the schematic function with stack exchange so I'll be posting these pictures. I wanted to repurpose the circuit in a fly zapper to make sparks. I drew a circuit I saw from the board to match the reference circuit I found. I want to know why they have added an extra capcitor and resistor to the circuit.

Reference Circuit

Redrawn to look like reference circuit

Drawn based on board component layout


texts: Is there such a thing as a (cheap) optocoupler with a non-polarised output?

texts:
Standard optocouplers have a polarised input and a polarised output, thus:

It is possible to get a coupler with a non-polarised input, thus:

However, what I require is an optocoupler with non-polarised outputs - for example, having two optotransistors/optodiodes in reverse-parallel. Does such a thing exist, cheaply (i.e. for a comparable price to standard optos)?
I prefer a DIP-4 package, but anything easy to solder by hand would do. And it should be smaller than DIP-8 because otherwise I might as well just use two standard optos in reverse-parallel.
(Note: triac outputs are not suitable, because they latch when passing DC. I just want two normal phototransistors/diodes in reverse-parallel.)
I have googled to no avail.


texts: How to determine the efficiency value of the inverter we design?

texts:
I designed an inverter with a maximum input voltage of 20 volts.
I want to make a specification of the efficiency of the inverter that I made using the formula efficiency = (output power / input power) * 100%.

The problem is I don't know how to calculate the output power of my inverter. Is the output power obtained from the load voltage * the load current connected to the inverter?

Is the input power obtained from the input DC voltage * the input DC current?


texts: Boundary conditions of the Electric field of a conducting transmission line

texts:
Solving Maxwell's Equations for the Electric Field of a linear-isotropic cylindrical conductor leads to the electric field being proportional to the Bessel function of the first kind (see below).

Maxwell's Equations:

\$ Div[E] = \frac{\rho}{\epsilon_{ps}} \$-> 0 (reasonable approximation of no free charge in conductor)

\$ Div[B] = 0 \$

\$ Curl[E] = -\frac{d}{dt}[B] \$   ... (i)

\$ Curl[B] = \mu J + \mu\epsilon_{ps}\frac{d}{dt}[E] \$  ... (ii)
Take Curl of (i):

\$ Curl[Curl[E]] = Grad[Div[E]] - Laplacian[E] = -\frac{d}{dt}[Curl[B]] \$

Since Div[E] ~ 0,

\$ Laplacian[E] = \frac{d}{dt}[Curl[B]] = \frac{d}{dt}[\mu J + \mu espilon_{ps} E]
\$
The assumption of a linear, isotropic material prompts us to treat eps, mu, and rho as frequency-dependent scalars (rather than tensors). Also, we make the assumption of J = rho*E, a rough approximation of Ohm's law that follows from the kinetic theory of charges in the context of the Drude model.

So: \$ Laplacian[E] = d/dt[\mu\rho E + \mu\epsilon\frac{d}{dt}[E]] \$
which is a basic wave-equation with a dampening terms via \$ \mu\rho \frac{d}{dt}[E] \$....

Representing Laplacian[E] in cylindrical coordinates to suit the geometry of the line, and solving the PDE by separation of variables (E[r,t] = R[r]*T[t]*Z[z]) leads to:

\$ R[r] = BesselJ[0,\lambda r] \$ (which is the r-spatial component of E).

In math/physics, it is here that we would typically quantize lambda using a boundary condition on the E-field at r = a (a being the radius of the line), and then employ some initial conditions to derive the required Bessel-Fourier series representation of the solution. Does this act of assigning boundary condition(s) apply to such wire systems, and if so, what form of boundary condition(s) on E[a] should we use? >> Are the standard boundary conditions of electromagnetism sufficient?

In mathematics, a boundary condition is typically specified and a Bessel-fourier series is then used to determine the nature of the field in the line. In electrical engineering, what type of boundary conditions are applied to a conductor carrying a current in the direction of the E-field?


texts: SW-420 vibration sensor module getting stuck

texts:
I am experimenting with SW-420 vibration sensor modules I just got from China. The digital out pin is supposed to output HIGH when sensor detects vibration, and LOW, when at rest.

There's an onboard LED that is lit when sensor is at rest and goes out when it has detected vibration.

However, with several (sometimes many) attempts at light poking, I can provoke a state when the LED is out constantly, although there is no movement. Usually it takes a light touch to kick it out of this state and the onboard LED lits up to show that the sensor is at rest.

I am wondering if this is a typical behavior of the vibration switch and I should program the firmware accordingly, to detect and handle a situation when the sensor gives uninterrupted HIGH for unreasonable stretch of time.


texts: How to attach a clincher connector to a FSR

texts:
How do you attach an Amphenol FCI "clincher connector" to a thin film force sensitive resistor? I see several sites selling these connectors explicitly for making it easier to wire FSRs, but almost no one explains how to attach them.

I found this single very bad "how to" video, but the video resolution is so low, I can't tell what's going on. They say to "trim off the leads", but it's unclear what that means. Are you supposed to trim off the pins, or the entire metal crimps on the FSR's default connector before applying the clincher connector? In the video, it looks like they just trim off the pins, and not the metal crimps, but I can't tell for sure.


texts: How is an XOR with more than 2 inputs supposed to work?

texts:
I've just started studying computer engineering, and I'm having some doubts regarding the behavior of the XOR gate.

I've been projecting circuits with Logisim, whose XORs behave differently from what I've learnt. To me, it should behave as a parity gate, giving a high output whenever the inputs receives an odd combination. It doesn't, though, for more than two inputs. How should it behave?

I also read in a book that XOR gates are not produced with more than two inputs. Is that correct? Why?


texts: AHRS algorithm under continuous linear accelerations

texts:
I have tried several algorithms to get pitch, roll and yaw under continuous linear accelerations and vibrations (smaller than 0.4g, frequency lower than 10HZ). None of them give good results because the readings either drift or are affected too much by linear accelerations. What I want to achieve is when external acceleration is smaller than +-0.4g, the error on pitch and roll should be smaller than +-1deg.

I have tried these algorithms:

Madgwick's algorithm. When Beta gain is set very high, the convergence is fast but angles are more susceptible to linear accelerations. I tuned it down and reduced the error under linear accelerations down to +-0.5deg. However, if the vibration is continuous, the readings will drift and it takes forever to converge to true values. It makes sense because under linear accelerations, gyro is trusted more and calculated angles drift as gyro integration drifts.
Mahony's algoritm. On the contrary to Madgwick's, it doesn't drift at all regardless what values I use for Ki and Kp. However, it is always affected by linear accelerations. (Errors bigger than +-6deg)
Traditional Kalman filter. Lots of time has been spent on tuning those huge R and Q vectors. So far it has the same performance as Mahony's.

I am using razor IMU. I know with cheap sensors it's impossible to achieve the same result as this one.

There are couple more options like UKF but it's a pain to understand or implement.

Any suggestion is welcomed.


texts: Powering a chain of 5volt sensors across 25 meters

texts:
I have 150 pcbs which are positioned across a 25 meter duct, each consuming 30mA maximum, how should I power them?
A pair of 24v wire and 7805 on each board will be fine? With decoupling caps?
Every 24 pieces also has a controller with rs485, so the ground should be common also? Or no?!


texts: Buck Boost Circuit for Automobile starter circuit

texts: One of the major problem with two wheeler like Royal Enfield is that the starter motor wont work efficiently as the battery ages with performance. Morning cold cranking the engine ignition will not start the engine but also weakens the battery life. Can a buck-boost convertor be used to supply steady voltage to starter motor, will this reduce the sudden Amps spike on the battery  and will this really improves that battery life?


texts:
I want to make a circuit that has to drive more than 20 LEDs that need to be bright on a single PCB. Each LED will have to be turned on independently based on information received. Power is going to be delivered via a 12V car battery and has to be brought down to MCU voltages 3V3 or 5V.

My idea is to have an MCU and LED driver IC - TLC5951DAP for example which is going to give me the needed pins to drive all of the LEDs. The problem is that if say I want to drive these LEDs at 10mA (as I said I want them to be bright), there is going to be a lot of power dissipated by the LDO. By the calculations I did, the LDO will have to dissipate 3.52W which is well above the 0.54W it is rated to handle. Is there any way to get around this?

Another idea I had is to make transistor LED pairs which will have to be turned on by a different IC which I have not yet figured out.

I am also open to other suggestions.


texts:
As title says, I'm trying to print a very dense PCB layout on a thermal paper.

I'm using a laser printer, as it is mandatory. The problem is, you can see some little grains/gaps all over the printed PCB design.

What can I do to prevent this? Is this due to dust/grease on the paper? or bad
printer/printing method?


texts: Vestigial Side Band Demodulation: Which components are to be retained and which are to be filtered out?

texts:
This article shows the analysis of Vestigial Side Band Suppressed Carrier demodulation.

I have understood the mathematical derivation up to eq (1). However, I am unable to understand which components in eq (1) are to be retained and which are to be filtered out and the reasoning behind it. I understand that in VSBSC modulation, along with one sideband, some portions of the other sideband (vestige) are also included while transmitting.

  Please help me understand, which terms are to be retained and which
  terms are to be filtered out in case of Vestigial Side Band
  Demodulation.


texts:
I haven't performed any tests, but if I am in a train with velocity != 0, what will measure my IMU? (With IMU I suppose to have acc + gyr + magn).

I am in a relative motion system, and my MEMS will measure the acceleration with respect to the train measurement system or with respect to the earth measurement system?


texts: how many SPI slaves dsPIC33EP series MCU can drive at the same time?

texts: I am designing a data acquisition system:a dsPIC33EPxxx MCU collect data and coordinate several (would like to have 28 of them) ADS1248 ADCs by SPI bus. A start conversion command will be sent simultaneously to all slaves and conversion result will be collected one by one. all chips will be on the same PCB with small distance to MCU. Does the SPI module of PIC power enough to drive all slaves at the same time?


texts: Why are high frequency signals not disturbed by stray fields?

texts:
I am trying to design an inductive position sensor based on a high-frequency signal.

It is mentioned that using high-frequency signals gives immunity towards stray magnetic fields.

Could anyone explain the theory behind this?

Why are the high-frequency signals immune to EMI?


texts:
Why is the AC flag set while using the ANI instruction in 8085:

MVI A, A3H
ANI 97H
HLT

The sign flag is set which is understandable but the AC flag is also set which makes no sense because, there's no carry from the D3 bit to D4 bit. How is this happening?


texts: Mesh network with high data rate on 868MHz

texts:
I need to create a wireless network with high expactations to redundancy and security, making my choise fall on a mesh type network. Between the nodes I should be able to transfer video or at least still images within 5-10 seconds or so to a central, communication on 868MHz without worrying about battery time since it is going to be powered with transformed mains power.

I haven't worked with mesh networks before, so I have started reading up on existing protocols and architectures, but if someone have any suggestions to what architectures I could try to use I would be very grateful.

EDIT: And how would I go forth to implement an open protocol on a microcontroller? Are there libraries I can use that is available for the general public?


texts: What is the cheapest way for two devices spaced less than 10 feet apart to communicate wirelessly with each other?

texts:
I'm building a musical instrument that comprises of two separate devices...one device is the master...has an accelerometer and a speaker. The master's buddy device also has an accelerometer.

When the buddy tilts, the buddy device interprets the accelerometer data and then sends a note to the master. The master plays the note using instrument voice 1.

The master, at the same time is processing it's own accelerometer information. Based on accelerometer data, it will play other notes using instrument voice 2.

If the user moves device one and then moves device two in special ways, a flourish will play.

My question is...taking into account the type/amount of data that I'm sending...essentially short control bytes, what would be the cheapest way for the two to communicate wirelessly?

--CLARIFICATION--
These devices ideally would be wireless and not tethered to each other. Also, these devices will be moved around freely so any line of sight method is less than ideal.


texts: Why Zener diode doesn't fire at specified voltage?

texts:
I have the following schematic, which would be used as a over-voltage and reverse polarity protection:

simulate this circuit – Schematic created using CircuitLab

Both D1 and D2 are rated at 15V+-5%, which should theoretically produce maximum breakdown voltage of 15.75V. Lab power supply is used as a voltage source. If I'm using jumper wire instead of fuse F1, then PSU just goes into current limiting mode, but crowbar part works as expected, but not at the desired voltage of 15V. I've tried it several times, both with and without load R3 (I'm using a heater as a load). The results are the same:

Voltage at output drops to zero when input exceeds 16.9V. If PSU is set to 16.9V, same voltage is at output. When I add 0.1V more, crowbar fires and output drops to zero.
I've measured voltage drop across D1, it exceeds 15V. If input is 16.9, then D1 voltage is about 16.3V, way too high compared to spec.
I'm using second DMM to measure D1 voltage. When input is getting closer to 16.9V, sometimes when I touch D1 with probes, output voltage drops to zero, but crowbar part does't fire (PSU shows 16.9V at the output).

Questions are: how to explain what I see, and how to tune crowbar to fire at exactly 15V? I think I could use 13V Zener, but I don't like acting without clear understanding of what's going on.


texts: How should I select my crystal frequency?

texts:
I have seen questions like this that talk about selecting a crystal for UART and I have seen questions like this that mention 32.768 kHz for RTC. But how do I decide the right crystal for my application.

At this point I am not sure what UART baud I will be using, but it will be one of the standard one. It would be nice to be able to get semi-accurate time in milliseconds, but not a requirement. Intuitively I think going with the fastest crystal that my micro can use will give me the most flexibility, but is there something I am missing? Is there a "general-purpose" frequency that people use?


texts:
I've just finished designing my own laboratory power supply unit. At first I wanted it to be 0-3A current limited, ~1-30V, but I've changed my mind about it - I think I might need more acuracy in the lower current levels instead of higher currents. For ease of design I decided that it'll be powered from a laptop charger. The choice of charger and LT3080 for current precision made it 0-1A, 1-20V. The whole thing is monitored and controlled by microcontroller.

About the whole project idea: this is a hobby project. I know that one can buy better bench PSU cheaper, but beside having a power supply I want to build it.

I have some concerns about parts of the circuit, namely:

Does the control of the ST1S14 look right? I found this kind of voltage controlled dc-dc converter somewhere on the Internet and I think I understand how it works, but I've never built anything like it - will it really work? I'm aware that there will be some offset from the set voltage and thats ok in this application, since this is just a preregulator (or there's an option to overcome this in software). Also is the BCR169 a good transistor here? I used it just because it's cheap and seems to be fast enough.
For the current limitting there are 2 digipots - 5k and 50k. This gives 0-1A regulation with theoretical resolution of \$1A \frac{\frac{5k\Omega}{256}}{50k\Omega}\approx0.4mA\$ (plus errors, plus wipers resistance offset). Could current limiting be done better without digipots, but using DAC and some opamps?
Finally the programming port. There's USBasp connector on sheet 3 and I want to use it while the board is powered externally, is it enough to connect all pins but vcc?

Is there anything else you see here that doesn't seem right? Are there any flaws with the schematic readability (there are everywhere, but how can I improve it)?

Here is the schematic:

sheet 1 - input to output

sheet 2 - additional supplies

sheet 3 - MCU and peripherials

Update - fixed ADC buffering opamps. Changed them to MCP6001 running from VREF(reference 3V). Changed shunt resistors to single 1W 500m\$\Omega\$ resistor.

Update - I've rethinked preregulator control part and came up with a way to drive it with analog feedback. This makes things a bit less complicated. I tested it in LTspice (with some LT dc-dc ICs) and it apears to be working.


texts: What are these parts and elements in the schematic doing?

texts: What are these transformers before the bridge? Whats the purpose at all of the schematics before the diode bridge?


texts: Difference in the characteristic impedance of a low frequency signal

texts:
In one of my PCB design, for a RS 485 signal termination resistor of 120 ohm is there. But the differential characteristics impedance of the signal is taken as 100 ohm instead of 120 and the signal travelling down the trace is of low frequency.
Does this impedance mismatch/change affects the low frequency signal particularly at the destination with reflections or some other SI issues?


texts: Tips on analyzing circuit with multiple op-amps and bjts

texts:
In a homework exercise I need to sketch the Vout-vs-Vin  graph, having it first obtained analytically. I know that Ur and Vin are both nonnegative, and the circuit is shown here:

It seems like there is a lot of symmetry in the circuit, and that this apparenntly complicated circuit can be broken down into a few smaller ones. All four of the op-amp stages resemble the classical logarithmic amplifier, however I feel that we can somehow bypass invoking the  \$\ln\$ function in this analysis.
UPDATE: Here is an Lt-spice dc sweep graph I did for R=0.5k, and Ur=5V. Seems, like Q3 was at first saturated, then went off.


texts: I am attending electronics basics course on coursera.org and professor says that Ia = Ib only if dq/dt = 0. Does he mean with that dq/dt = 0 that currents will be equal only if material is not previously charged, so we have clean material without charges and current supplied will go in and exactly the same amount will go out from that tube?


texts: To what extent can Gielis' so-called "Superformula" be used to improve the efficiency of WIFI antennas?

texts:
I am new to this Stack Exchange venue, so please don't shoot me if this question is not appropriate. This question was taken Math Stack Exchange.

In 2003, the Belgian plant biotechnologist Johan Gielis proposed a formula that allows for the description of a wide variety of shapes in \$2d\$, \$3d\$ and higher dimensions. This is the formula

$$r( \phi) = \bigg[\bigg|{\frac{\cos(m \phi/4) }{a} }\bigg|^{n_2} + \bigg| \frac{ \sin(m \phi / 4)}{b} \bigg|^{n_3} \bigg]^{-\frac{1}{n_1}} $$

in polar coordinates, where \$r\$ is the radius and \$\phi\$ is the angle. More information can be obtained via the wikipedia page. Gielis' original article can be viewed here.

A couple of days ago, it was reported by numerous dutch newspapers and magazines that this formula can be applied to make new WIFI antennas that supposedly are much more efficient than previous antennas. Furthermore, it is claimed by the Telegraaf newspaper that this formula can be used by architects to create \$3d\$ designs more easily and that it could be used to design software for $3d$ printers. (See the Telegraaf article here. It is in Dutch, but one could use google translate to understand it). In the online magazine called Kennislink, it is claimed that the formula can be used to reduce the size of \$3d\$-imageing software a thousandfold. (See the Kennislink article here.)

Questions: To what extent are these claims true? Why do you believe so?


texts: Implementing an absolute value function in C

texts:
I am implementing a function to find the absolute value like this:

uint16_t absolute_value(int16_t n)
{
  int16_t mask = n >> 15;
  return ((n+mask)^mask);
}

Is it any quicker than just doing a simple multiply by -1 if less than 0?

This code is on a microprocessor where speed is everything.


texts: Replacing aluminum capacitor by tantalum capacitor for accelerometer bulk bypass

texts:
I am currently working on a design which includes the AIS3624DQ accelerometer from ST. In the datasheet, it says (section 4, page 17):

"Power supply decoupling capacitors (100 nF ceramic, 10 μF aluminum) should
be placed as near as possible to the pin 14 of the device (common design practice)."

Can I replace the 10μF aluminum (due to its large size) with a tantalum capacitor instead?


texts: dimmers - is the problem solved with pure sine wave

texts:
I've been interested in dimmer technologies these days, and spent some time in reading about this topic on the web.
According to what I understand, the problem with usual dimmers is that with inductive or capacitive loads, the current is not in phase with the voltage, which prevents the dimmer from working. So, they invented various technologies like phase adaptive dimmers, or pulse width modulation etc.
I just want to understand: if a dimmer were able to deliver a pure sine voltage of settable amplitude (and of the same frequency as the main), without regard to the current flowing through the device, would the problem be solved ? would led lamps, transformers etc. work well under this "dimming", or is there something else?


texts: Can I safely connect 20 Raspberry Pi Zeros to this 5V 10A power adapter

texts:
I want to connect 20 Raspberry Pi Zeros (5V, .200-.300A) to a 5V 10A power supply shown below. The setup Im planning will look like the photo below but with many more Raspberry Pis.

I posted my setup on the Raspberry Pi Stack Exchange here where I was told this was unsafe, but I did not really understand why or how to fix it. The guy was telling me something about a polyfuse on the Pi Zero that might blow, but when I googled that, apparently a polyfuse is not a component on the Pi Zero, so I figured I would come here for a second opinion.

My thoughts are this, please correct me if Im wrong (in simple terms since I'm a noob). The power source is 5V 10A rated so if I were to just connect that 1 Pi shown in the photo it should be totally fine since it runs on 5V and it will only draw the amperage that it needs from the power source. Alternatively, I could also hook up 20 Pi Zeros to that terminal block in the photo, since cumulatively they would only draw 4-6Amps of the 10amps available (and they all run on 5V). This seems safe to me but maybe I'm missing something.


texts:
I’ve been trying to revive a set of vintage Apple-branded powered desktop speakers. Nothing more than a gunked up potentiometer and a broken solder joint on the input and they’re now working again.

There’s however a constant hum/buzz coming from both speakers when plugged into their 9v DC power supply, which gets worse when I put a finger over some of the caps’ contacts. Example here: https://youtu.be/XfSJliJzJvA

The noise is there whether any inputs are connected or not. There is nothing else plugged into the electrical outlet, and I’ve tried other outlets in the house. As I understand it this rules out ground loop noise, but I’m by no means an expert.

Boards look fine visually and I’ve pulled and tested each of the larger caps.

I suspect that it’s simply the amplifier(s) picking up noise, and have read that a resistor across the input can cut out this noise. The resistor value should differ based on whether the input is amplified or line level, but these speakers should be able to deal with either scenario, I think.

Would this work, and what value of resistor might you recommend?

Edit: Just wanted to add that I tried running the speakers with another power supply I have (one of those cheap AC/DC switching power supplies), and the noise was even worse.


texts: Add constant DC voltage to a variable DC input

texts:
I'm designing a PCB and I need a voltage rail, roughly 3 volts above the main input (of 3 - 30V). This rail is to power some CMOS devices, so it won't need to supply much current.

Currently I plan on using 2 AA batteries in series with the input, but those batteries are huge compared to the PCB so I want to get rid of them. I have searched for multiple solutions, but none match my requirements:

Charge pumps probably won't work, because of the big voltage change in the input.
Boost converters deliver a steady voltage, but I need an addition to the input.
I have looked at isolated DC/DC converters, but these usually run on 5V or higher, or they are too expensive.

Do you have any ideas?

EDIT: I don't necessarily need a higher voltage. I need a stable 5v from the input. I'm not willing to use a buck boost converter, since that will take up too much space.


texts:
What I did, step by step:

Cut off the USB-A cable from a device. (smart card reader)
Cut a USB-C to USB-A cable in half. (cable came with a phone)
Soldered the USB-C part (see step 2) to the device (see step 1):

Connected the device to my phone: It was not detected. (lsusb in
 Termux)
Cut a USB-A to Micro cable in half.
By soldering, replaced the USB-C cable with the USB-A cable from step 5.
 (In case you wonder: I could’ve used the original cable from step 1, but
 that was already destroyed as I tore it apart – see below.)

Connected the device to my phone using a USB-C to A adapter. Now it worked.

What did I do wrong?

Now I read in an answer that one should do some connections via a resistor.
However:

I tore the cable from step 2 apart:

The USB-A part contains no resistor. Furthermore the colors of the wires
exactly matched the standard USB-A pin out.
The USB-C part contains some electronics. There is a component labeled
D9 and another very tiny component possibly labeled R1. It looks like
that tiny component bridges the white and the green wire. It’s hard to
see because it is all covered in glue which is almost impossible to peel
off.

On the web, I found advertisements for USB-C to USB-A cables that mention
the resistor being part of the USB-C plug. I assume this is standard
practice.

I don’t understand what went wrong. The solder connections were certainly good.
In fact I redid them, then tried again, got the same result. Also I was very
careful not to short any connections, except for intentionally shorting the two
black wires once: no difference


texts: Explaination of high current zener transistor regulator circuit

texts:
This is a high current zener TRANSISTOR regulator circuit. I want to know

What does "high current" mean here?
How is this circuit working as a zener regulator?
What is the purpose of transistor here?How is it working?
What is the main component in the circuit diagram?
What is the purpose of capacitor here?
Why is the purpose of resistor here?


texts: I'm designing a circuit to charge mobile battery. My source is giving a DC output of 15V, 100mA, whereas I need DC 6V, 450mA for charging. Is there any way to boost DC current?


texts: Verilog RAM module with Register File & Testbench

texts:
I am designing a RAM module with testbench in Verilog. It is suppose to access a register file (.dat) in the testbench and run it through an ALU module. There are 4 modules (memory.v, alu.v, toplevel.v and testbench.v).

My problem is that when I run the ModelSIM I am not getting the expected results.

`timescale 1ns/1ps

module testbench_lab3_reg();

reg clk;
reg [4:0] Read_address;
reg [4:0] Write_address;
reg read_en;
reg write_en;
wire [15:0] DataOut;
reg [15:0] memory [0:15];

assign DataOut = (read_en) ? memory[Read_address] : memory[Write_address];

lab3_reg dut(.clk(clk), .Read_address(Read_address), .Write_address(Write_address), .read_en(read_en), .write_en(write_en), .DataOut(DataOut));

always
begin
    clk = 1; #10; clk = 0; #10;
end

initial begin
$readmemb("memfile.dat", memory);

Read_address = 5'b00000; Write_address = 5'b01001; read_en = 1;  write_en = 0; #20;
Read_address = 5'b00000; Write_address = 5'b01001; read_en = 0;  write_en = 1; #20;

Read_address = 5'b00001; Write_address = 5'b01010; read_en = 1;  write_en = 0; #20;
Read_address = 5'b00001; Write_address = 5'b01010; read_en = 0;  write_en = 1; #20;

Read_address = 5'b00010; Write_address = 5'b01011; read_en = 1;  write_en = 0; #20;
Read_address = 5'b00010; Write_address = 5'b01011; read_en = 0;  write_en = 1; #20;

Read_address = 5'b00011; Write_address = 5'b01100; read_en = 1;  write_en = 0; #20;
Read_address = 5'b00011; Write_address = 5'b01100; read_en = 0;  write_en = 1; #20;

Read_address = 5'b00100; Write_address = 5'b01101; read_en = 1;  write_en = 0; #20;
Read_address = 5'b00100; Write_address = 5'b01101; read_en = 0;  write_en = 1; #20;

Read_address = 5'b01001; Write_address = 5'b00000; read_en = 1;  write_en = 0; #20;
Read_address = 5'b01010; Write_address = 5'b00000; read_en = 1;  write_en = 0; #20;
Read_address = 5'b01011; Write_address = 5'b00000; read_en = 1;  write_en = 0; #20;
Read_address = 5'b01100; Write_address = 5'b00000; read_en = 1;  write_en = 0; #20;
Read_address = 5'b01101; Write_address = 5'b00000; read_en = 1;  write_en = 0; #20;

$stop;

end
endmodule

I know my ALU works because I tested it using a MegaWizard generated RAM. The following is my ram module:

module memory(
input clk,
 input [15:0] write_data,
input [4:0] raddress,
input [4:0] waddress,
input read_enable,
input write_enable,
 output [15:0] read_data);
reg [15:0] memory [0:15];
 reg [15:0] data_out;

assign read_data = data_out;

always @(posedge clk)
 begin
    if (write_enable)
        memory[waddress] <= write_data;
      if (read_enable)
            data_out <= memory[raddress];
end

endmodule

The following is my top level module, which instantiates the ALU and the RAM:

module lab3_reg(
            input clk,
            input [4:0] Read_address,
            input [4:0] Write_address,
            input read_en,
            input write_en,
            output [15:0] DataOut
            );

wire zero;
wire signed [3:0] y;
alu inst1(DataOut [12:9], DataOut [8:5], DataOut [15:13], y, zero);

wire signed [15:0] y_signed;
assign y_signed = y;

wire [15:0] data;
assign data = DataOut;
memory inst2(clk, y_signed, Read_address, Write_address, read_en, write_en, data);

endmodule

I'm pretty sure the problem is with my testbench, but I've been racking my brains over this, so any help would be awesome.

memfile.dat

0100000111100000
1100000111100000
1111111000000000
0001111111100000
0010000111100000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000


texts:
in the following circuit:

Im looking to find what \$v_D(t)\$ is given \$V_γ = 0.7 V\$ and \$r_f = 0\$.

Now when doing the DC analysis, find that \$VDQ = 0.7 V.\$
But im having trouble finding IDQ.

Would that be \$4.7/7V\$?

Once, I find that I use \$r_d = VT/IDQ\$ correct?

Thanks you all very much!


texts: The Relation of power heat losses with V & I in transmission lines

texts: The voltage is stepped up at the beginning of transmission lines and step down again at the end of the latter. This is, of course, to reduce the current passing through the line and thus reducing the heat losses. \$P\$ loss \$= I^2 \cdot R\$. but also this equation can be rewritten as \$P\$ loss \$= V^2 / R\$. So, if we raised the voltage difference across the whole transmission line we also will increase the losses, according to the second equation. I know this happens to be false. But, what is exactly wrong with that way of thinking?!


texts: What prevents (illegitimate) operation of NFC with higher power?

texts:
I was going to post this on Information Security, but Elecrical Engineering may possibly be a better fit since it's more about the technical side.

Like most people nowadays, I am left with no choice but to have a NFC chip on my credit and debit cards. Although you can tell the bank not to enable NFC payments (which I did), the chip will nevertheless tell anyone asking the credit card number and validity date, in plaintext. That's just how it works.

Now, the NFC propaganda states that this is perfectly safe because it only works up to 4 centimeters range (although other sources say 30cm), so someone would have to get extremely close to you, which is none more risk than any other card because they could as well steal the card.

Disregarding EM regulations, which a criminal couldn't care about less... what exactly prevents a criminal standing a meter or two behind me from using, well, a slightly bigger antenna, maybe a directional one with a reflector hidden under the T-Shirt, and a somewhat stronger sender, so the signal is for example a thousand times (let's say 1024 times) stronger than what's used in the card reader terminal. The square root of 1024 is 32, so that should provide the field intensity necessary to power up the chip (and make it reply) at 32 times the distance, respectively 32*4 = 128 centimeters. Or, assume 4096 times stronger for 2.5 meters range.

A credit card terminal (the entire thing including display and all) has a total power consumption of about 2W. So it's not unreasonable to assume that the sender is rather... weakish. The antenna can't be much larger than 3-4 centimeters either. Even more so as e.g. in Europe no more than 10mW ERP is generally allowed at all for frequencies below 27MHz. So it's probably something "single-digit milli", or "micro".

Surely it is possible, and easy, to carry a sender that is a thousand times stronger than that?

Of course, using a high-power sender might accidentially "fry" someone's chip when getting too close, but again, what does a criminal care about frying my card.


texts:
I was recently reading up on vacuum tube like devices that could serve as a possible replacement for traditional CMOS technology. How could vacuum tube like technology replace CMOS if vacuum tubes don't have two different types of switching (In CMOS this would be N-channel and P-channel transistors). Vacuum tubes only stop current if there is a negative charge on the gate, in contrast MOSFETs have two different kinds of transistors (N and P channel) that switch with different voltages. So my question is: Is it possible to implement two different kinds of switching in vacuum tubes? And if not, why do people think this could serve as a possible replacement for traditional MOSFETs?

Here is the article I was reading: http://www.nytimes.com/2016/06/06/technology/smaller-chips-may-depend-on-technology-from-grandmas-radio.html?_r=0


texts: Holding voltage high, for monostable 555 timer pulse

texts:
I want to know if there is a simple (and cheap) way to make a momentary button (for which we cannot control the time it holds when pressed!) press to virtually hold for about 1-2 seconds.

More precisely, I want to implement a low power consuming solution for a monostable-"mode" 555 timer. Thus when the button is "hit", the 555 Vcc pin will go HIGH for at least the amount of time required for one pulse to be sent out. After that the circuit will go back to stable 0V, until next hit.

Even more precisely - The pulse is used to move a small servo to a certain, constant, predetermined position.


texts:
I've bought this kit and successfully assembled it.
I use 23.4-0.23.4 V power source and two ELZET 10000uF caps.

So, after I connected my speakers (by the way it is Amphithon (Амфитон) 25АС-027 4 Ohm, it is USSR speakers, very powerful and have isodynamic tweeter) I noticed there a lot of bass (and not enough hi-freqs), my windows started vibrating at 10% volume.

I tried to use EQ and lower low freqs, but it didn't helped much.
So, I decieded to investigate a bit how it works, I removed the OPAMP and installed jumpers to pass input signal bypassing OPAMP, so I completely get rid of OPAMP impact actually. The sound became a bit hush but still bassy. After that I decieded to investigate the preamp schematics, I used multimeter and created a wiring diagram, Here it is.

After removing highlighted resistor the sound became clear and crisp.

So, my question is why do I need that resistor? What other components can affect sound? Is it Ok to remove highlighted resistor? Why these components needed, I can't find that type of apllication in datasheet...


texts: I2C slave not pulling down SDA data line for the full clock cycle

texts:
I am communicating with some slave devices via multiple busses, however even though they are all the same device (http://www.invensense.com/mems/gyro/mpu3050.html) and all receive the same message/clock from the master, they don't hold the SDA line down for the same amount of time:

If you notice, devices 1 and 3 do not pull down for the same length of time as devices 2 and 4.  However they are all the same type of device receiving the same messages from the master.

In this instance, devices 1 and 3 are causing problems because their changing from low to high (due to not holding the line low for long enough time) on the same clock cycle which should not happen during slave ACK or slave data sending:

The device I am using to send and capture these signals (simultaneously) is a National Instruments PXI device that oversamples at 1 MHz which should be plenty so I don't think its simply a display issue.

I thought it could be a timing issue of some sort, but per the MPU-3050 device specifications on page 16, it adhears to I2C FAST-MODE:

My current timing parameters are much slower than that so they should be valid inputs:

tSU;STA - 4700 ns
tHD;STA - 4000 ns
tSU;DAT - 1000 ns
tHD;DAT - 4000 ns
tSU;STO - 4000 ns
tBUF - 4700 ns
tHIGH - 4000 ns
fSCL - 80 kHz

My only real requirement is I need the device to ALSO satisfy the STANDARD-MODE specifications for I2C (as my above ones do) because I plan to add more devices to these busses that won't allow FAST-MODE.

I really have no idea of what could be happening here, so its possible its not even a timing issue at all.  I've tried some "trial-error" stuff with the timing, but similar behavior always occurs.  If you have any ideas as to how I could try to fix this, please let me know!


texts: Sampling too soon after MUX switching channel

texts:
I'm confused with noise created by switching channels on a MUX. My supervisor on my bachelor thesis warned me about sampling too soon after a channel switch, because noise could make the voltage values inaccurate when sampled by an ADC.

The MUX I'm using is the SparkFun Analog/Digital MUX Breakout - CD74HC4067

This is the oscilloscope picture from a channel switch where "channel 1" is \$\approx\text{0V}\$ to \$\approx\text{2.7V}\$ on the next channel.

In the datasheet on the component CD74HC4067 it says (on page 4):

Am I completely misunderstanding the term "switching noise"? Because I can't really see values that will be big enough to cause a problem. I'll be sampling after approx >7ms.


texts: Can anyone identify this manufacturer? "E3"?

texts:
This has everyone I ask stumped. The board is a Siemens 115U CPU (6ES5943-7UA11) from the Simatic S5 rack, circa 1990's. It has some LEDs and two SPDT, O-ring sealed toggle switches on the front, one of which is an exotic ON-OFF-Momentary style. I've tried running the numbers (26-11 06xx), nothing. Tried looking through hundreds of manufacturer logos, nada. Even went to patent trademark websites and searched through countless combinations of "E3" "3E" "EE" "33" etc... nope.  Can anyone confirm whom made these switches?  Was it Siemens in an act of obscurity?

Inside they are pretty neat. Flipping the lever moves a spring-loaded ball bearing along a pointed track for the "snap" action feel. While the shaft holding the ball bearing, once it reaches position, pushes against a top and bottom set of tiny switch contacts.


texts:
simulate this circuit – Schematic created using CircuitLab
I need an LED flasher circuit to operate inside small model lighthouses. Ideally the flash needs to be white and the battery needs to be physically small but last for years.
Conventional wisdom (and holy writ,) is that you should not put a resistor in series with the Vdd pin of a CMOS logic circuit however I have working before me a highly efficient LED flasher circuit that does just this.
The circuit (that I rather stumbled upon,) uses one 4001 IC. The IC has two gates configured as a conventional astable and uses the remaining two gates as inverters in series which provide anti-phase outputs.   With no resistor in the supply line and a supply voltage of 9 Volts this part of the circuit consumes 170 microamperes which is not surprising for a CMOS oscillator at this supply voltage.  This is unsustainable for a small battery to supply for any length of time. The oscillator cycle period is 12 seconds.
With a massive 1 Meg Ohm resistor between the supply line and the Vdd pin the circuit still runs but now with a cycle time of 5 seconds. The circuit now consumes around one microampere and, incredibly, the 'On' voltage available at the output of the two inverters is above 6 Volts and is available to feed two 2N7000 FETs with no need for level shifting. The two FETs are wired in series and fed in anti-phase so that when one is switched 'on' the other is 'off'. At the source/drain junction between them the output voltage cycles between 0 and 7.1 Volt.
The output of the two FETs is connected to two white LEDs connected back to back in parallel and these in turn to an electrolytic 'bucket' capacitor which is connected to ground. When the output goes high it charges the capacitor via one LED giving a flash and when the output goes low then the capacitor discharges via the second LED giving another flash.  The two LEDs can be physically mounted close together so as to appear to be a single light source and to fulfil the requirements of a model lighthouse.
The intensity of the flashes can be varied by selecting different values of the bucket capacitor and I have tried values from 4.7nF which gives a just discernable flash and up to 47 microfarad at which value the flashes are very bright. At 4.7nF the current consumption is 1 microampere and at 47 microfarad the current consumption is 21 microampere. These values are roughly one thousandth what would be normal for a 555 circuit and would reduce further with longer cycle times.
The knotty problem of measuring such low currents is solved here by having the 100 Ohm sense resistor with a parallel 3 Farad super capacitor in the supply line. (This capacitor is one that I have to hand--a smaller super capacitor would probably do.) After a lengthy period, (say half an hour for very low current values,) the voltage across the resistor can be measured with a suitable millivolt meter and the current calculated. These two components can be removed when not required.
My question is "I would like to think that this circuit could have widespread application but is it just too outrageous to recommend?" (I should add that my qualifications lay outside electronics but having had a ham radio callsign for nearly sixty years I have a long history of cruelty towards and misuse of innocent components.)


texts: Why laptop reboots after electrostatic discharge

texts:
So why does this happens when my laptop is plugged to the charger? Typical charger scheme looks like this:

What is the path for discharge current? Low voltage part seems to be isolated from power lines.

Some forums says that the reason the laptop was not connected to the grounded outlet but how can grounding helps?


texts: A binary number is parallel-loaded into a shift register. The shift register is then commanded to shift right" for one clock pulse. How does the value of the shifted binary number compare to the number originally loaded in, assuming that the MSB is on the left flip-flop of the shift register?


texts: What is the purpose of this schottky diode reversed across the BJT base resistor?

texts:
In a design for the popular "gotek" floppy drive emulator, as per the standard, the outputs from the floppy emulator are open-collector.

An STM32 is used as the processor. This drives a 74HC04, which then drives MMBT2222A NPN transistors through a 1k resistor as the open-collector outputs.

On just one of these six drivers (the serial DATA_OUT from the floppy emulator), there is a schottky diode across the base resistor. What is the purpose of it?

My guess is that it causes the transistor's base capacitance to discharge quicker when the HC04 goes LOW, so this driver will switch off quicker than the others? (I'd think this level of timing precision wouldn't be needed for floppy drives).

On a side-note: I am developing an enhanced version for vintage computers (original is very basic without modifications). I am trying to optimize the design. Based on looking at what other floppy drives use to drive the open-collector outputs (often a 7438), I should be able to use a 74LVC07, or a 74HC07 with 3.3V powering it, and do away with the transistors? Or am I missing something important.
Or the safe option: use the original design (but use HCT04 instead).

A 5.25" floppy drive on the same open-collector "bus" can have 150-ohm pull-ups. This would cause significant current that would be pushing a logic IC, so I wonder why floppy drives get away with using 7438 as the driver.


texts:
I am trying to ring a phone bell with an Arduino. I have tried using a 12v motor controller (h-bridge), but I have an old bell, and that was barely enough to drive it, and I'd also like to use a single 5v wall wart to power the entire thing (logic board and bell).

I found several circuits that can be powered by 12v, expensive or hard to find ring generators (Black Magic and others), and one unit that seems like an ideal match, but a bit of an overkill, really: http://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=38816

So I'm looking for a schematic for something simpler that could make that bell ring off a 5v supply. As far as I understand it should be some kind of boost circuit and h-bridge combo, so I can control the frequency of the bell from firmware. But a fixed frequency bell that I can turn on and off will do as well.


texts: Which side of SPI link harness to locate SDO pull-up?

texts:
I'm looking for some help/insight into a decision I am making about whether to change a circuit I have built.

My slave device requires a pull-up on its SDO (MISO) pin which is open collector. When originally drawn, this pull-up was placed close to the slave device, before the signal passed through an isolation device and was then sent over a link harness to the board containing the master device.

Later we moved the isolation barrier to the control board side, and the pull-up got dragged across too, for whatever reason.

So the sequence now goes

SDO pin -> Link harness -> master board with pull-up and isolation device -> gate array MISO pin

and the two boards work together OK.

Given the opportunity now to respin the slave board, what are the arguments for bringing the pull-up back across to live with the slave device, if any?

Apologies for lack of diagram - written on my mobile device. Hope the question is clear, thanks for any input.


texts:
I am struggling to understand how the receiver is able to differentiate between multiple CDMA users, who are transmitting at the same time.

In this figure for example, I understand each part, except from the final two rows, when I do the multiplication, I only receive an 0, while in the example, several integers are changed from positive values to negative or vice versa. For example in the bottom row, why does the -4 become a +4?


texts: Why does a Common Base amplifier gives non inverting output?

texts:
I am unable to understand why a Common base amplifier gives a non-inverting output.

My reasoning so far:
Let's take a look at the Common Collector (Emitter Follower) Amplifier. Here \$V_e = V_b -0.7\$. So on differentiating we get \$ d{V_e} = d{V_b}\$ which clearly implies that output is non-inverting. Similarly in the case of Common Emitter amplifier \$ V_{out} = V_{cc} - I_cR_c \$. which implies that \$d{V_{out}} = -d{{I_c}R_c}= \beta d{I_b}R_c \$. The negative sign implying that output is inverted. But in the case of a common base amplifier, I can't figure out with similar reasoning. When the emitter voltage increases then \$I_e\$ increases which in turn increases the \$I_c\$ and the situation again becomes like that of a CE amplifier. Please provide an explanation of why this is the case and where am I wrong?


texts: Is it possible to use a digital pressure sensor with a ATtiny4313?

texts:
I have a pressure sensor as follows, tested and works great with the Arduino Uno:

Output is digital through SCL/SDA.....

Will I be able to use this directly with the ATtiny4313 coding with Arduino language? On the Arduino Uno it's a piece of cake to connect up and use. I have not yet got the hang of the protocols and the datasheets are beyond my current knowledge and understanding.


texts: My oscilloscope is not measuring the frequency of my wave accurately

texts:
I bought an oscilloscope from Amazon it is Hantek DSO5102P (Digital, 2 Channel, 100 MHz, 1 GSa/s)

I am trying to test it, I have an MSP430FR6989 development board (MSP-EXP430FR6989) and programmed it to toggle a pin (P4.7) every 0.5 ms to give me a square wave of period = 1 ms (f = 1 kHz).

This is the code for reference

#include <msp430.h>

#define ONE_MS  25;
#define ONE_SEC 25000;

#define ENABLE_PINS 0xFFFE

int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;   // stop watchdog timer
    PM5CTL0 = ENABLE_PINS;

    //init Timer
    TA0CTL |= TASSEL__ACLK;

    TA0CCR0 = ONE_MS;
    //Taclk = .02ms faclk = 50Khz
    //count = 0.5 ms/.02 ms = 25
    //count = 1 sec / .02 ms = 25000

    TA0CTL |= MC__UP;//count till TA0CCR0

    P4DIR |= BIT7;//P4.7 output
    P4OUT |= BIT7;

    while(1)
    {
        if((TA0CTL & TAIFG) == 1)//if flag is set
        {
            P4OUT ^= BIT7;//toggle P4.7 every 0.5ms or 0.5s
            TA0CTL &= (~TAIFG);//clear the flag
        }
    }

    return 0;
}

I probed the pin with reference to ground and pressed the AUTOSET button, it gave me a square wave of period = 1.39 ms (f = 720 Hz).

EDIT1

I checked the compensation of my probe, I connected the probe's lead to the PROBE COMP ~5 V @ 1 kHz connector and the reference lead to the PROBE COMP Ground connector and got this waveform.

END OF EDIT1

Is that normal for oscilloscopes?

The community's help is very much appreciated.


texts:
this is my first electronics project that i am doing so my understanding is pretty basic.
I am using an ESP8266 connected to a L293D motor driver to power a bipolar stepper motor. The issue I am having is the pin connections.

This is the microcontroller that i am using. It has 9 GPIO pins at 3.3V.

This is the driver I am using.

My first question is whether I can use the 3V out of the micro controller to power the EN pins? On the data sheet, on Recommended Operating Conditions, the High-level input voltage is a minimum of 2.3V so I guess this would be ok?

Secondly, I am trying to drive a 12V bipolar stepper motor so I am unsure whether I would need to use a second motor driver due to the lack of available pins on the driver.


texts: MOSFET driven LED AVR blinker circuit exibits flakey behavior

texts:
The following circuit, built on a prototypeboard/stripboard, sometimes fails to operate: it is dead to the world. No output regardless of the input. I originally thought that some of the soldered connections were flakey (on the basis of the fact that touching the the board would seem to cause the circuit to go dead or back alive), however, after checking the prototype board again, I couldn't find much of anything out of the ordinary, other than the resistance between Vcc and Gnd being 7.?? mega ohms.  I am wondering now if there is some mistake in the circuit design/logic?

The input is either 0V or 12V, and is connected to the uC via optocoupler. The uC listens for the input, and flashes the various leds while the input is 12V and turns them off when input goes back to 0V. Full code:

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <avr/cpufunc.h>
#include <avr/sleep.h>

volatile uint8_t  useless = 0;

ISR(INT0_vect) {
  useless ^= 0xFF;
}

int main(void) {

// Using PCINT0 as low-level interrupt

MCUCR &= ~ ( (1<<ISC01)|(1<<ISC00) );   // low level interrupt on INT0
GIMSK = 1 << INT0;                       // enable INT0 interrupt

#define OUTPUTA 4
#define OUTPUTB 3
#define INPUT   1
DDRB= 0x00|(1<<OUTPUTA)|(1<<OUTPUTB);
PORTB=0;

sei();    // enable interrupts

_NOP();

while (1) {
  if ( (PINB && (1<<INPUT)) == 0 ) {
    PORTB |= (1<<OUTPUTA)|(1<<OUTPUTB);
    while ( (PINB & (1<<INPUT)) == 0) {
      _delay_ms(170);
      PORTB^= (1<<OUTPUTA);
    }
    PORTB &= ~ ( (1<<OUTPUTA)|(1<<OUTPUTB) );
 }

 if (1) {
   // Go to sleep
   MCUCR |= 1<<SE;
   MCUCR = MCUCR && ~( (1<<SM1)|(1<<SM1) ) |  (1<<SM1)|(0<<SM1);
   sleep_cpu();

   // Wake up here
   MCUCR &= ~(1<<SE);
 }

My current best idea is to replce the 74HC14N (my apologies the Schmitt trigger is that, and not 74LS14), and the size of the smaller bypass cap (the circuit is powered by a 2-3A wallwart and there is quite a few LEDs)

EDIT: Fixed schematic vis-a-vis optocoupler output (thanks Peter Benett)

EDIT2 Fixed schematic to show that reset pin is tied to Vcc (thanks geometrikal)


texts: Arduino Serial print changes behavior of program undesireably

texts:
I'm using a loop counter, declared in a header:

int loop_counter = 0;

I use this counter to trigger an event every so often. I used to use a modulo for this same type of behavior, but I simplified it so it's easier to work with (it still results in the same behavior)

void loop() {
    if(loop_counter > 100) loop_counter = 0;
    else loop_counter++;

    //Serial.println("hey");

    if(loop_counter == 0) {
         //do_something_important();
    }
}

All is well and good, until I try communicating with Serial by uncommenting the //Serial.println("hey");  ("hey" in this example because, to me, this behavior is absurd).

This results in loop_counter never triggering the do_something_important(); section of code.  I tried declaring loop_counter as volatile, that didn't change anything.  I tried Serial.print ing loop_counter, and I was also getting odd behavior (it would freeze the loop).  Serial.println("hey"); works in the sense that in the Serial monitor I get plenty of "hey", (i.e. quickly a lot more than 100 "heys", the number of iterations at which the other section of code should trigger)

What could possibly be causing the usage of Serial, with data that is not (as far as I can tell) tied to loop_counter completely prevent it from working properly?

EDIT: Here is the part of the main file that ended up posing the problem (well, contributing the most to it (using too much memory)):

void display_state() {
  int i,j,index=0;
  short alive[256][2];

 for(i=0;i<num_rows;i++) {
   for(j=0;j<num_cols;j++) {
     if(led_matrix[i][j]==1) {
       alive[index][0]=i;
       alive[index][1]=j;
       index++;
     }
   }
 }
 alive[index][0]=NULL; //Null-terminate.
 alive[index][1]=NULL;

 //383 is a great number
 for(int idx=0;idx < index; idx++) {
   display(alive[idx][0],alive[idx][1]);
   delayMicroseconds(283);
 }
}

Here is "letters.h":

    #ifndef _MY_LETTERS_H
    #define _MY_LETTERS_H

#define nrows 4
#define ncols 4

#define num_rows 16
#define num_cols 16

#define MAX_WORD_LENGTH 16
#define NUMBER_OF_CHARACTERS 26

#include <stdlib.h>

int loop_counter = 0;
short led_matrix[num_rows][num_cols];

const short letter_a[nrows][ncols] = {{0,1,1,0},
                    {1,0,0,1},
                    {1,1,1,1},
                    {1,0,0,1}};
const short letter_b[nrows][ncols] = {{1,0,0,0},{1,1,1,0},{1,0,1,0},{1,1,1,0}};
const short letter_c[nrows][ncols] = {{0,1,1,1},{1,0,0,0},{1,0,0,0},{0,1,1,1}};
const short letter_t[nrows][ncols] = {{1,1,1,1},{0,1,0,0},{0,1,0,0},{0,1,0,0}};

typedef struct letter_node{
  const short *data;
  letter_node *next;
  int x;
  int y;
} letter_node;

letter_node aa = {&letter_a[0][0],NULL,1,1};
letter_node bb = {&letter_b[0][0],NULL,1,1};
letter_node cc = {&letter_c[0][0],NULL,1,1};
letter_node tt = {&letter_t[0][0],NULL,1,1};

letter_node letter_map[NUMBER_OF_CHARACTERS];
    #endif

Some more information:
- I'm using an Uno (ATMega328)


texts:
Can a transistor array supply current to a single LED using multiple outputs pins?  In the following 5 volt circuit, an LED is connected to two outputs of a M54561P current supply transistor array.  The configuration is intended to render two different brightness levels from the LED (1 triggered, or 1 & 2 triggered).  Will this circuit function, or will current flow back into the array (through the output clamping diodes maybe) if only input 1 is triggered?

simulate this circuit – Schematic created using CircuitLab


texts: I was wondering as to why VHDL has a boolean data-type? When does '0' or '1' not cut it? Is boolean implemented differently?


texts:
Are simulations delayed?
Below is my simulation, when enable and reset are 1, Asynchronous reset should be printed
In the simulation this happens at 5ns on the rising_edge but in the simulation it shoes at 25ns?


texts: Do I need to add smoothing capacitor for this setup

texts:
I'm trying to build an array (100) of WS2812B which are controlled over an Particle Photon, both are powered by a 10A/5V power supply.

Powerwise: 10 WS2812B will be daisy-chained in one row
Datawise: All of them will be daisy-chained in one serial row

The whole setup looks something like this:
The resistor after

I added a capacitor at the power supply to smooth the voltage and a resistor prior to the first WS2812B to protect the data pin.

My question is: Do I really need the individual 100nF capacitors for each LED is the big one at the power supply enough? Or do I even need to add more capacitors, for example in the middle of each daisy chain?

Thanks for the help. I couldn't find to much in the data sheet. But each WS2812B can draw a maximum of 60mA when emitting white at full power.


texts: What is a good circuit for recording a piezo contact microphone or an electric guitar pickup?

texts:
I'm building a guitar tuner that can be used with a (piezo) microphone clip for acoustic, and from the pickup for electric. In my experiments they have comparable signal levels.

However, the piezo has a very small capacitance and large resistance. So the input circuit needs to have a high input impedance.

So far I've been using a good old non-inverting opamp with a 100k biasing resistor to ground. This seems to work okay, but then I found this collection of opamp circuits that includes a "Amplifier for Piezoelectric Transducer" that I don't really understand. What is going on here? How do I go about calculating the gain and impedance of this circuit? (and what is the 30pF cap doing?)

I've also found this other question about This guitar piezo opamp buffer lacks any sort of bass, why? which has the common problem of having too low input impedance. Their suggestion seems to be to just increase the biasing resistor of the classic circuit, but in my simulation this only goes so far before the input current of the opamp starts to create a noticeable offset.


texts: Block diagram for an analog audio amplifier,

texts:
I am attempting to design my own audio amplifier i have started the process with a block diagram. So far the "blocks" i have are:

Input audio signal → Band-pass filter → Preamplifier → Power amplifier → Load

The only restriction that has been imposed is:

No digital electronics

Is a buffer amplifier needed between the input and band-pass filter?


texts: Odd voltage readings between phase-ground, phase-neutral, neutral-ground

texts:
Recently i tried gathering voltages from few AC outlets in my house. I got following readings using a dmm
Phase-Ground = 398V-400V (should be around 240V)
Phase-Neutral = 230 V
Neutral-Ground= 210 V (should be around 1-2V)

I tried in the whole house but got same results and i can't figure out where the problem lies. I know for certain that my ground is fine.


texts: Why would a sensor output an inverted signal?

texts:
I have a sensor that has 3 components: X, Y and Z and for every component there are 2 channels:

X+ :0 V ± 5 V voltage output
X- :0 V ± 5 V voltage output inverted

All I know is :

If the circuit uses "active high" logic, 5 volts represents a digital "1" and 0 volts represents a digital "0".
If the circuit uses "active low" logic, 5 volts represents a digital "0" and 0 volts represents a digital "1".

My question is: what's the purpose of the inverted output? How can I make use of it as I am plotting results.


texts: A question regarding noise investigation

texts:
There is a single-ended earth grounded data acquisition system which is multiplexing and sampling eight channels at 500Hz sampling rate. Channel are isolated from earth ground and the signals are low freq. signals like force transducer amplifiers, temperature sensors ect.

After solving the 50Hz ground loop issues and be sure no ground loop exists, now sometimes(we don't know when and why) I'm encountering a large noise on all the channels. To make it more clear the two plot below are from the same transducer at different days(offset is expected but not the noise):

As you see above, the standard-deviation and the noise margin around the blue plot is much much greater than the green one. An this large white-like noise exists on all channels when it appears.

Here is the FFT spectrum of the noisy channel:

Before I investigate these, I dont have so much time and I'm not sure about some basic route paths I might follow.

1-) Can this be common mode noise? I'm asking because normally common mode noise is at 50/60hz by magnetic coupling. Because it seems to me(?), if the noise would be coming from a single transducer it would not appear on all the channels.

2-) Should this noise be considered as "white-noise" or can it be a particular high freq. noise?(The sampling rate is 500Hz).

3-) I'm planning to check or renew all the BNC connectors and coax cables. That's all I can think for now. Because people I work with don't want me to use any sort of filter. So I want to find the source of this noise. One of my colleague who is not into these subjects keeps saying the issue might be related to earth ground and want me to earth the transducer's frame. But that doesn't make sense to me. I'm really confused at this point. What kind of test or procedure should I follow? I don't know if the source of the noise is the ADC itself, or one of the signal input, or cables, or common-mode noise or the earth ground...

edit:

Another example of same issue when 16 channels sampled. ch14 and ch15 are analog output but still sampled:


texts: Remove DC offset from a Hall sensor output

texts: Here is the test circuit for an encoder output from a car seat motor. It seems the output signal has a DC offset of 4.5-5V. How do I convert this signal to a 0-3.3V level?


texts: Can I saturate a BC337 transistor using the output from a 4017 decade counter?

texts:
I want to build something very similar to an 8x8 led matrix (like this one https://www.instructables.com/810-LED-Matrix-with-4017/ only with more power) using a shift register plus eight transistors to supply the electricity and a 4017 decade counter with eight BC337 transistors drain it (switching between the eight rows really fast).
I think that the maximum current which needs to be able to flow through the BC337 transistor would be 500 mA (it can handle 800 mA maximum).
If I understand correctly, the datasheet of the BC337 states that 50 mA is required in order to saturate it so that it would work as a switch.
Does anyone know if the 4017 counter would be able to supply this and what kind of resistor I would need to use?


texts: Why is my analog temp sensor's signal so unstable?

texts:
I have an analog temperature sensor (TMP36 - datasheet - product page) and it is properly connected to an analog pin for reading its output.

The Arduino sketch (firmware) works just fine. Everything actually works fine except for two things:

If I plug more components in the circuit, like for example connecting an LED in parallel, temp readings go up for 1 degree (Celsius).
From time to time the readings go crazy (like 80°C or 100°C), although it's never that hot in here.

The connection is like this: from the Arduino's 5V pin to the sensor positive lead. Then, from the sensor's negative lead to the GND pin in Arduino. And finally, from the middle lead to the A1 analog reading pin.

Why are situations 1 and 2 happening? Is this normal?


texts: Why is the prewarping not working as it should?

texts:
Just playing around with the 'c2d' command from matlab and trying to convert a continuous 2nd - order lowpass Butterworth function to a digital one which has the specs of Fc = 20e3Hz and Fs = 44.410e3Hz.
When I apply the pre-warping frequency parameter of 20e3Hz, it doesn't close to mimicking the continuous function.
Is there a reason why this is occurring? Does the prewarping have a limitation of how much it can "pre-warp" or am I doing something wrong? Maybe that's the intended output?
Legends:

LP = Continuous TF
LP_D = Discrete TF

Code:
s = tf('s');

LP = 15587249629.803/(s^2+176556.77655678*s+15587249629.803);
LP_D = c2d(LP,1/44.410e3,['Method','tustin','prewarpFrequency',125663.706]);

UPDATE: With a higher FS = 96e3Hz from 44.410e3Hz with no pre warping:

UPDATE2: Comparing with and without prewarping on two different Fs (44.410kHz and 96kHz) using a 3rd order Butterworth filter lowpass
Cutoff frequencies:

LP = 1.25e5 rad/s
LP_D_44kHz = 6.70e4 rad/s
LP_D_96kHz = 1.10e5 rad/s

With pre-warping:

Cutoff frequencies:

LP = 1.25e5 rad/s
LP_D_44kHz = 8.59e4 rad/s
LP_D_96kHz = 1.13e5 rad/s

Without pre-warping:

UPDATE 3: Doing some research I might have an idea. Just a gut feeling.
I found 2 resources that converted an analog Butterworth into a discrete one using the Tustin method with prewarping and it worked for them.
I noticed they created the Butterworth filter completely different from the way I did it. I made mine based on the Sallen-Key configuration and just found the transfer function, could that be it? For some reason the Sallen-Key way doesn,'t like the prewarping?
Resources HERE and HERE
I also noticed when using a notch filter with the same sampling frequency (44.410kHz) and prewarping it works perfectly. Why when doing low pass filters it doesn't like it that much?
UPDATE 4: Could be the warping is just to nonlinear for it?


texts: Measure average and instantaneous pulse power

texts:
1) How to calculate average power by having voltage and current waveforms of one oscillation period that looks like this?

Someone suggested me to use:

Won't this integration result in "negative power" somewhere between 5 us and 10 us and then again after 15 us? Applying this formula to waveforms that overshoot results in negative power. Sine waves with purely resistive loads should result in zero power (hence, RMS?). Shouldn't an RMS variation of this integration be used for average power measurement?

2) What can one say about instantaneous power where voltage waveform is positive and current waveform is negative (and vice versa)?


texts:
I'm working on a hobby project that is to add sensors to a wooden chess board in order to detect if a piece is on a given square.
I'm quite beginner at electronics, only experienced in programming, not aware of terminology.
I've come across a few ideas, from reed switches to Hall sensors. In terms of sensors, I'd prefer Hall sensors (SS49E).
The next problem is how to read data.  I've seen a solution that uses a cd4067 to implement multiplexing. I'd need 4 of these.
Is there a solution that does some kind of chaining? An ideal solution would be to have a module with a Hall sensor belonged to each square and chain them together, read them similar to dealing with shift registers. Something like implementing a 1-bit shift register with the sensor on it. Sorry if this is stupid idea.
The goal is to minimise wiring and make the hardware simple.


texts: How to reduce the DC power supply ripple noise during relay switching

texts:
I have relay controlled by BC547 transistor powered by 24V Zener regulator.
The transistor is switched by a microcontroller which is powered by a 5V linear regulator.
The linear regulator receives input from the 24V from Zener regulator. At the instant when relay is switched, linear regulator 5V output fluctuates between around 1V min to 7.8V max for about 20nS.This causes microcontroller to reset(but not at every instant).
Guys is there any fix to this??


texts: Recommended Sensor / Type of the sensors to be used

texts:
For example, I have a board (A plain board or a board with sensors, this needs to be decided depending on sensors ). On this board, I will place small objects. These small objects are having 2 sides (like a coin). I just want to know how many objects are placed on this board.

What kind of sensors can I fit on the board?
What sensors can I use on these small objects? (might be some sort of magnetic strip attached to these small objects and the sensor on the board can detect these object)

The objects can be placed randomly(not one at a time) on the board. Each object can be of different weight.


texts:
I just measured a pair of LEDs "just for fun" and discovered that they're outputting energy. I held one on the LEDs in the sun's direction and the Multimeter went straight up to 10V. I laughed because I had absolutely no clue what's happening inside those things and how...

How is that possible? Are they "solar panels" in a way, because ... how can this be?

Below are two pictures of my "finding":

(I tried plugging an Arduino Mega on the other end to see if it would power on but unfortunately it stayed off)

I also measured the amperage between the two leads, but the only mode that work on my multimeter is the "10A" mode. It stated 0.00(A).

EDIT: The LED has this appareance:


texts: How is reverse saturation current of a BJT measured empirically?

texts: I'm not asking the definition, but wondering how do the manufacturers measure this parameter's quantity in a lab for instance? For example for Ic Vce characteristics they keep Ib constant and they obtain plots. What is the procedure for obtaining  reverse saturation current of a BJT?


texts: Converting expression to only use NAND gates

texts:
How would I go about converting this Boolean expression so that it would only use NAND gates in its circuit?

A ⋅ ¬B ⋅ ¬D + ¬A ⋅ B ⋅ ¬C ⋅ D


texts: Switching a 3v motor with a MOSFET using a 3.3v signal

texts:
****I have knowledge of programming but VERY little experience with electronics.****

I'm attempting to switch a MOSFET using a 3.3v signal from an Adafruit MCU module (Adafruit Module here).  The load the MOSFET would be switching is a 3v water pump (Water Pump Info here).  The MOSFET that was chosen is the PMV28UNEA from Mouser.com (MOSFET Datasheet here).

The problem I'm having is when the signal pin from the MCU is set to high, the MOSFET switches on but my multi-meter shows a voltage drop when the motor is connected.  Without the motor connected the voltage is around 4v (expected from the battery).  However, whenever I connect the motor, the voltage drops to around 2.30v and the motor will not cycle on.  The motor did cycle on once when I first tried it but hasn't since.  I can't figure out what's causing this drop in voltage. I've included a simple schematic along with the links to the MCU, pump, and MOSFET.  If I'm missing any relevant information here that would help please let me know.

simulate this circuit – Schematic created using CircuitLab


texts: What material are pins of a microcontroller typically made of?

texts:
I've found the following suggestions around the web, but I found no source which I could trust completely:

Tinned Steel
Kovar
A copper alloy

As suggested, I'll edit a little bit of background info here, which I have also posted in the comment section. Im currently learning about soldering, in the context of research. Its a lateral entry for me, and since I have a background in materials I wanted to know exactly what alloys can be involved. It is background research. I realise that normally, an electronics engineer doesn't care that much about it since there are standardized techniques for soldering in the industry.


texts: VHDL simulation full adder, timing question

texts:
Let's say I have this design for example:

library ieee;
use ieee.std_logic_1164.all;

entity adder is
port(x : in std_logic_vector(3 downto 0);
     y : in std_logic_vector(3 downto 0);
     z : out std_logic_vector(4 downto 0));
end entity adder;

architecture rtl of adder is
    signal c : std_logic_vector(3 downto 0);
begin
    adder_gen : for i in 0 to 4 generate
        half_adder_gen : if i = 0 generate
            z(i) <= x(i) xor y(i);
         c(i) <= (x(i) and y(i));
   end generate half_adder_gen;
        full_adder_gen : if 0 < i and i < 4 generate
            z(i) <= x(i) xor y(i) xor c(i-1);
         c(i) <= (x(i) and y(i)) or ((x(i) or y(i)) and c(i-1));
        end generate full_adder_gen;
        overflow_gen : if i = 4 generate
            z(i) <= c(i-1);
        end generate overflow_gen;
    end generate;
end architecture rtl;

Usually if I run a design like this what I see in the waveform is that ALL the bits of the output changes instantaneously as soon as the input bits change as well. However this behaviour is not what I expect in this case, I would expect that the output bits y(4) ... y(0) changes when the value of c(i) is known, but such bit depends on the c(i-1) and so on... Is there something I'm miss understanding?


texts: Why can't you put a plane under a trace antenna?

texts:
I'm working with RFID for the first time. All the app notes I've read show a separate region of PCB allocated for the trace antenna, with no planes above/below. I want to understand why this is, and if it's strictly necessary. I understand that the plane will shield the antenna from one direction. For my application, this is ok.

I can fathom the following scenario:
1) An electromagnetic wave is incident upon a trace antenna with a copper plane below it
2) The distance between the plane and antenna is half the wavelength (not realistic for RFID, but this is a thought experiment)
3) The field seen at the antenna is 0, because the incident wave and reflected wave are 180 deg out of phase.

So, in this scenario, there's no changing field and no current induced in the trace antenna, so nothing is received, but this is only because the separation between the copper plane and antenna is lamba/2. When this is not the case, I would imagine there should be current induced in the antenna.

I'm particularly interested in this because I want to save board space. Specifically, I want to put components and signals on top, and the antenna on the bottom, with a copper plane in between.

If I cannot do this, can anyone explain, with precise language and in EM fundamentals (no handwaving armchair engineer stuff please!) why this will not work?

Thanks