texts: How do I calculate closed loop gain's deviation?

texts:
I have an exercise in my book that I am trying to solve:

  How large must the magnitude of the loop gain, \$ |A \beta| \$ be in order
  for the closed loop gain, \$ A_t \$, to deviate less than 0.1% from the
  asymptotic gain, \$ A_{t \infty} \$ .

Since the amplification is given by:
$$ A_t = A_{t \infty} \frac{-A \beta}{1-A \beta} $$

This means that \$ \frac{A_t}{A_{t \infty}} = 1-0.001 = 0.999\$

By solving the inequality
$$ 0.999 \leq \frac{-A \beta}{1-A \beta} $$

I get \$ AB \leq -999 \$ and \$ AB > 1 \$.

But for some reason the answer in the book is different from my calculation

Answer in the book:
$$ |AB| \geq 999 $$ which is equivalent to $$ -999 < AB < 999 $$


texts: Single input terminal for multiple voltage inputs

texts:
I am designing a board for which I want to have single input terminal for voltage. Board is microcontroller based(Atmega328) so the voltage coming to uC(Vcc on picture) should not exceed 5V.

How I imagined it:
V_PICK is jumper for choosing the input voltage. User will connect only 5V or 12V to this board:
a) When 5V is connected, voltage goes directly to Vcc and to the rest of circuit. Jumper is in 1st position. The voltage gone to the linear regulator doesn't matter because is too small for regulator to do anything with it.
b) When 12V is connected, jumper is in 2nd position and voltage goes over regulator who regulates it down to 5V. Then the voltage goes to Vcc.

The problem is, when jumper is left in 1st position and 12V input is connected to input terminal - then 12V directly goes to Vcc and burns uC and other chips onboard. I have thought of adding Zener diode at place marked on picture, but not 100% sure how to connect it. I googled out that zener in series with resistor(who will deal with remaining voltage, for example if input is 12V and zener is 4V7, resistor will dissipate 7.3V).
If I need 500mA of current at 5V, resistor value should be 14.6 ohm? Is that correct? Formula I used is: (Vin - Vout) / current needed

VIN on picture is line used by MOSFETS in other part of circuit so it should be left there directly connected to input.

Is it correct that if I added zener diode, jumper and regulator will be no longer needed? Voltage would automatically "find its way":
a) 5V is in, voltage goes across zener to uC. MOSFETS directly draw current from VIN line while not load on zener.
b) Same thing when 12V is in, just voltage will be reduced for uC.

Finally, I should find zener diode that's 2.5W(500mA * 5V). As I have seen, they are not very often and might be expensive. Should I got some alternative way for all this?

I am just a guy still learning about electronic laws and really appreciate your help.
Thank you!


texts: Issue with double and unsigned char type variables

texts:
I am trying the code in this datasheet on an Arduino mega2560 with mpu6050 IMU,

I have made some changes in the variables and I do not get errors so far.
and the code doesn't give any output, can some show me a place with wrong code work?

I get mpu6050 range accX and accY -2^15 to + 2^15. I do not post code for mpu6050 since it works. I need to serial print and see how it displacement changes in this code.
in positionxy() function I wanted to print

 Sample_X =  (unsigned char)accX/129;
 Sample_Y =  (unsigned char)accY/129;
 Serial.print ( Sample_X );  Serial.print ("\t");
 Serial.println ( Sample_Y ); Serial.print ("\t");

and it gives nothing,
i think the issue is with the variable types and i cannot figure it out.
The part of the code as follows,

//all varibles
double accX, accY, accZ;
unsigned char  Sample_X;
unsigned char  Sample_Y;
unsigned char  Sample_Z;
unsigned char  Sensor_Data[8];
unsigned char  countx,county ;
signed int  accelerationx[2], accelerationy[2];
signed long  velocityx[2], velocityy[2];
signed long  positionX[2];
signed long  positionY[2];
signed long  positionZ[2];
unsigned char  directionxy;
unsigned long  sstatex,sstatey;

void setup(){
 *****mpu 6050 config is done here and works aacX and accY updates with
 current accelration value  *****
}
void loop(){
do{
Calibrate();
movement_end_check();
positionxy();
}while(1);
}

void Calibrate()
{
************see datasheet **********
}

void positionxy()
{
unsigned char count2 ;
count2=0;

do{
Sample_X =  (unsigned char)accX/129; // this line is changed
Sample_Y =  (unsigned char)accY/129; // this line is changed

below serial print always gives zero

Serial.print ( Sample_X );  Serial.print ("\t");
Serial.println ( Sample_Y ); Serial.print ("\t");

accelerationx[1]=accelerationx[1] + Sample_X;
accelerationy[1]=accelerationy[1] + Sample_Y;

************see datasheet **********
}
movement_end_check(){
************see datasheet **********

}


texts: Largest spectrum image sensor and processing its entire spectrum image

texts:
I was developing a digital system to process raw images stemming from an image sensor but I would like to deal with "universal" (as possible) spectrum image sensors with no filter.
I know that for long wavelengths (microwaves), the mechanism is different with respect to the detection of infrared-visible-UV-X-ray light since the last ones should use the photoelectric effect to capture photons, but between infrared-visible-UV-X ray that use photoelectric effect, the material of the sensor changes because the photon has different energy.

Does a new technology or a new kind of sensor exist that is able to detect "at least" radiation from Far Infrared to X-Ray wavelengths?
CMOS and CCD sensors have both roughly the same spectrum sensitivity (from NIR to part of Near UV)? Or exists CMOS and CCD sensors, made with different materials, able to detect also at FIR and X-ray wavelength?
In the market there exist CMOS or CCD image sensors with no filters? In this case, the resulting image is monochromatic?
A Bayer filter that gives RGB color to a detected image, since color is related to the visible spectrum only, this filter has a role on the building of a IR or UV (or X-ray) digital image? If I have a row image got by a sensor with no filter, thus an image with spectrum from Infrared to X-Ray (or UV), is it possible to make a digital filter? For example, starting from this row image with its entire spectrum with no filters, building digitally the IR only image, or UV only image or visible only image?


texts: Hi am simulating in ADS microstrip T-lines for a 3 bit phase shifter, the lines are calculated to insert 55,110 and 220 phase shift for 2.16Ghz. With the S-Parameter simulation i can see the phase of the direct transmission coefficient which is consistent with the calculation, however looking at the voltage waves there is a difference between  the calculation and the phase of the coefficient. What could it be? Here is the simulation and results.


texts: Optical communication module using LED and photodiode or sensors

texts:
I'm trying to build a wireless communication system using LED and photodiode sensors. The communication distance is at most a few meters away, and the communication speed can be around 10kbps or even less.
I try to use pre-built modules for sender and receiver systems as a turn-key system, but I found none so far.

Do you know where can I find some modules/kits or whatever that does the LED communication?
If there is none, is there any schematics or documents/books so that I can use to build one?


texts: Working out current, voltage and resistance in a Bridge circuit?

texts:
This community is so helpful, my thanks go out to any comment I got with helpful advice.

Here's another homework problem.

I've tried working most of it out, but I have a feeling that I'll have to redo some of the calculations. I've never seen resistors in this type of network before. All I know is that it might be called a bridge circuit?

I just need help finding: The total resistance of the circuit, finding Va using the voltage divider rule, finding V1 and V2, and calculating I1 with a direction.

Here are my calculations:

Original circuit


texts: How to calculate how much current can lithium battery provide?

texts:
I need to know how much current can produce battery below? And how to increse current and voltage with 2 batteries like this below?

Here are some details:

Nominal Capacity : 250mAh
Size : Thick 4MM ( 0.2MM) Width 20MM ( 0.5MM) * Length 36MM ( 0.5MM)
Rated voltage : 3.7V
Charging voltage : 4.2V
Charging temperature : 0 C ~ 45 C
Discharge Temperature : -20 C ~ + 60 C
Storage temperature : -20 C ~ + 35 C
Charging current: standard charge : 0.5C, fast charge : 1.0C
Standard charging method : 0.5C CC ( constant current ) charge to 4.25V, then CV ( constant voltage 4.2V) charge till charge current 0.05C
Maximum charge current : 1C
Maximum discharge current : 1C


texts:
I am currently working with real-time image processing in FGPA. I have some timing problems about the classical FFT algorithm. i.e : FFT of one images spends more time than one frame period time.  I dont get the term of burst-size(or length) of a SDRAM.Is this a mode of SDRAM ( aka Burst-mode? ). I am using DDR3.

Best Regards,

Edit: PART is MT41K256M16. This DDR3 works in 1866 Megatransfer/second datarate. Below image credit : Micron, MT41K256M16


texts:
I plan to create a magnetic vibrator to shake a small container.
What I plan is to buy

Two "Magnet Wire 14 AWG Gauge Enameled Copper 1.5lb 118ft 200C Magnetic Coil Winding"
a custom made container with two strong magnets on each side, the container will be held by two bearing, so the container can "swing"
a power resistor (Any suggestion of where I could buy a variable power resistor)

I plan to put the container in middle in two magnetic coils where those two coils and the power resistor are in series. I plan to use power from wall outlet 120V60Hz to create the magnetic field

Any suggestion?


texts: Upgrading a treadmill controller / console

texts:
So I have an older model treadmill that I would like to upgrade if possible. The newer treadmills roll to a stop very elegantly, whereas this older model just switches off. Also the console is old, worn out etc. It's a very common brand, EKS Fitness.

Under the hood, I see a motor for speed, and a motor for tilt, and a controller, and then of course the console.

I've asked and been told that the console and controller cannot be replaced.

But I'm skeptical. Surely the Controller and Console together represent 99% of the electronics? The two motors are almost certainly the same across many different models. I don't unfortunately have a whole lot of other parts to try, but if I could simply rewire the motor connections for a new controller/console, I would stand a good chance of success.... no? What am I missing?


texts:
I'm about to design a PCB for a project with a TI DSP (TMS320C6720). What is the best method to use as an interface for getting the program onto the DSP? I haven't done this part myself before. I'll be using CCS v4 and my motherboard has usb 2.0 pots and a parallel port but I'd rather use the USB so that I could keep using whatever cable I need to get in the future. I'd prefer a low cost solution, I saw some JTAG emulators that cost 100's which is more expensive than I thought would be necessary, however it would be helpful to be able to debug when I'm programming.
Thanks


texts: Orcad Capture CIS, How to change transistor area?

texts:
If using the QbreakN and QbreakP, how could I change the relative emitter areas of each individual transistor.

I need to match the parameters like in the figure below:


texts:
So I am basically trying to grasp/confirm my grasp of SDRAM and DDR. So basically I understand that there is going to be some chips each with up to 8 banks (so kinda like 8 chips internally?). For each bank there is so many rows, than for each row there is a column or basically like a grid or 2 dimensional array specifying a bit.

But I understand that a DIMM and most memory controller bus is 64 bit? So How do I get a connection from the 64 (128 cause they are differential pairs) to the 8 or so chips/modules?

I know this is a little bit of a fuzzy question, I may not know enough to define a more clear question.

BONUS OFF TOPIC QUESTION: Also just if anyone knows, how is this memory exactly accessed from intel cpu? Is the memory controller (set of registers) configured with the timings and that memory mapped to the cpu's address space so that a memory address operand will automatically be translated into banks, rows, and columns all opaque to the cpu code?


texts: Will an electrolytic capacitor work reliably with 0 VDC and 100 mVAC?

texts:
I ran across an instrumentation amplifier datasheet from "THAT Corporation", and noticed the polarized capacitor in series with the gain resistor:

It is a typical 3 op-amp in-amp, so the differential input will be seen across the gain resistor, and C1 is meant to avoid changes in dc output offset with gain.

Now, the input is typically a microphone, and the AC voltage can reach 100mV or even a bit more.

For a 2k gain resistor and 6.8uF cap, 10 Hz will be seen with -3dB across the cap: 70 mVAC.

So the question is, will an electrolytic survive and work properly during these small negative excursions?


texts: Will adding a pole in the loop gain make the system more unstable?

texts:
In the design above, the circuit designer added a low-pass filter in the feedback path of the op-amp for loop stability.
Won't adding a pole to the feedback factor actually make the circuit more unstable?
Source: https://www.radiolocman.com/shem/schematics.html?di=278861


texts: Importing spreadsheet (pdf/xls) into Altium

texts:
I have following spreadsheet in a PDF file:

How do I import it into Altium and place it on Top Layer in PCB Editor?


texts:
I'm have grounding problems (80% sure of it). I have an MPU6050(gyro sensor which works on 3.3V) which is powered by the Arduino's 3.3V pin and SCA,SCL,INT pins are used with the I2C bus of the Arduino Uno which I believe is also 3.3V, and finally the ground is connected to the Arduino's ground. All works well now, I get raw values which is processed into angles and finally printed in the serial monitor. So far so good. Here comes the big problem, the minute I connect a 12V lipo's ground to the arduino ground the MPU6050 stops responding. Clearly the battery is producing some sort of noise to the arduino , I'm using the lipo to power a motor driver (L298) which controls two motors. If I separate the ground(motor driver i.e battery) from the arduino the motors do not respond, clearly they need a common ground to work in harmony. Will adding a capacitor in series with the ground of arduino and motor driver solve this problem? If yes, of what value? [I've attached Fritzing breadboard schematic,I dint get the exact battery part so I've just attached a random battery. The battery I've used in my setup is 11.1V 2200mah]

And here's a link to my motor driver specifications : Link


texts: I have a mac and am looking for some instructions/tutorials on how to start using the Bluetooth Mate with a Lilypad board. If anyone has any experience with this that they would like to share I would appreciate it!


texts:
I have the data of power generated by a solar panel per minute in kW. I need to calculate the total number of kWh generated per day. How do I do this?

So far, I divided each value of kW by 60 and then added all the 1440 values(minutes per day) thus obtained. I don't think this is the right approach though. Can anyone please help?


texts: I am implementing an MPPT controller with a battery charging controller to charge a lead acid battery. The question has to do with my understanding of how MPPT works. From what I understand is that the MPPT controller will vary the duty cycle so that the load impedance matches that of the panel to extract maximum power for the PV panel. I have been looking for a way to charge the battery and extract maximum power from the panel simultaneously and my struggles was how the power will balance in a case where the PV panel generates way more power than needed. After reading some Q&A here one answer mentioned that "The MPPT controller varies the load so that the load will accept as much power as possible OR so that the panel will deliver as much energy as possible" by Russell McMahon . Does this mean that the MPPT controller will only extract power that the battery can accept/sink thus the input and output power will be somewhat balanced.


texts: Reverse-engineering a brushless ESC, could someone help me understand the circuit

texts:
So I'm in the process of trying to reverse-engineer a hobby brushless ESC.  Above is the schematic for a single half-bridge drive circuit.

VIN is 11.1V

D1 is an unidentified diode; all that I've been able to glean so far from it its orientation and that it has a forward voltage drop of around .54V.  Suggestions on obtaining more info about it are welcome

T1 and T2 are NIKOS P75N02LDG (logic-level enhancement mode N-FET)

T3 is LMBT3904-LT1 (general-purpose BJT)

HIGH and LOW come from a 5V micro.  LOW is also pulled-down (forgot to show that here.  10K to GND)

Haven't been able to measure C6, could possibly be 10uF-22uF (1206 package, my bet)

My questions are as follows:

Why does the high-side FET need to be driven with the BJT circuit and the low-side FET not?
What is the purpose of the diode in there (D1) (forward voltage drop of .54V, not sure about what part# it is)?  Is it to keep momentary dips in the VIN line from affecting how T2 is driven?
As near as I can tell, HIGH is not pulled up or down.  When the uC is not configured, this will leave the base floating, which will cause T3 to not conduct (right?), which will cause the gate of T2 to go high, which will cause VIN to go out on the motor line, right?


texts: Decoupling caps near ICs, but how much near?

texts:
I always read about decoupling CAPs should be near to MCU pins, but how much near? If we are talking about very small caps of 0201 dimensions, wich distance is good from MCU power pin?

Look at this example:

Each grid block it's 5mil of distance, decoupling cap was placed at 5mil from MCU power pin and this it's minimum distance I can get from my PCB manufacturer. As you can see I found some difficults to layout adjacent pins, also on reflow this small cap can slide(that happens to me) on MCU pins and this is problematic to solve. (note that big via is a 13mil size and seems very big near 0201 package)

But this 5mils I can get are really necessary? Can I go to 10mil or 15 mils? or place in vertical position this cap?


texts: 12V fan does not work when in parallel but does in series

texts:
I am building a food cooler for camping this summer. My plan is to build a thermoelectric cooler that is solar powered. My cooler is looking much like this:

including a CPU fan on the hot side and heat sink on the cool side. I bought a 5W, 12V solar panel to run it (and make it so I can also plug it into my car). Both the fan and the TEC will be connected in parallel to the source.  When testing with a power adapter, the fan runs only if in series, which would have it going at 6V.  In parallel the fan does not run.  This is a CPU fan that runs at 12V.

What is happening?  Any suggestions for a fix?


texts:
I have 2 of the normal Agilent E3646A power supplies and an Agilent
GPIB/USB adapter.

All 3 devices have different GPIB addresses and the two supplies are connected together with a GPIB cable.

However, only the device works which is directly connected with the
USB adapter.

I can connect to the other (it says "Remote Control" on the display as
soon as I connect) but as soon as I send an SCPI command (e.g., RST) I
get a timeout.

So, the connection works in principle but the communication not.
Do I need to terminate the GPIB bus somehow?
Can the cable be broken?


texts:
For the following question, how do we find \$I_B\$ and \$I_C\$?

Would it be

$$I_C = \frac{V_{in}-V_{BE}}{80k}$$

and

$$I_B = \frac{12-0.12}{5k}$$


texts: I'm an undergrad building a railgun and I need assistance!

texts:
I am a physics undergrad that chose his senior project to build a low voltage railgun, however I am running into a few different issues.

1.) The paper mentions a "flyback diode bank" which I have never heard of. I assume it is several flyback diodes connected together to prevent high voltage spikes, however it is only briefly mentioned in the paper and it is not clearly shown.

2.) There is also a MOSFET driver circuit which is mentioned but was not mentioned in great detail. Would I be able to create my own triggering system for the railgun, or could I possibly use disposable camera circuits instead?

For reference I am using three 3400 Farad capacitors in parallel, and have almost all of the electrical components mentioned in the paper. I currently do not have any parts machined and am in the process of doing so. I plan on decreasing the length of the rails due to the smaller current used.

https://aapt.scitation.org/doi/full/10.1119/1.4760659
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110005535.pdf

The first link is the paper I am basing my project on, however the second link is very similiar and is free.

Thank you for reading and any help provided!


texts: alternative to 4017 decade counter for iterating over matrix columns

texts:
NOTE: I have made some changes since the original question, the number of columns is 114 not 45, this may affect some of the answers below.

I'm working on a project with a large LED matrix I'm making. I'm using 114 columns of LEDs and need a way of iterating over the columns in such a way that I can use minimal number of pins from my AVR.

Back when I was in school I remember we used to use decade counters, the 4017, I seem to read now that these are obsolete, and they seem to have been replaced with bcd counters. That's all well and good, but I need pins, not efficiency, 4 bit bcd output doesn't help me, I need 114+ connections I can iterate over.

So, what do I use? I need something along the column length to switch them in sequence.

Below is a quick SPICE schematic I threw together of how I want to set this up, the difference is that my real project will have 28 LEDs in each column and 114 columns, R1-R28 and C1-C114.

I have 74HC595 8 Bit shift registers on the Rows, clocking in data, all I need is a suitable device to switch high the 114 transistors sinking the current.


texts: Would optical signal processing still suffer from slew rate?

texts:
In electronics, analog signal processing/computation suffers from parasitic capacitance which leads to slew rate—which is the maximum rate of voltage change allowed, so handling super-high frequency becomes impossible.

Is this still true for optical signal processing/computation, such as optical (frequency) mixer or optical frequency multiplier? If so, what would be the physics behind?


texts: How much might inductance change if the core is water instead of air?

texts:
I'm trying to make a water level indicator. I don’t like giant float switches. If anyhow change of inductance can be measured due to change of water level, it would be helpful.
I'll buy copper coil tomorrow.


texts: Designing oscillating circuit for DIY DC -DC converter

texts:
Am building a power supply that uses a transformer which outputs 24v rms. The problem is it uses various sensitive components such as an LCD. I think I have thrown together a buck converter to solve this issue. However am stuck on how to drive the MOSFET since I can't use a 555 timer because I don't have a 5v rail.

I have a feeling am trying to run before I can walk but hey. Ofcourse I can just buy a ready built dc-dc converter but I thought I'll have a go at building a crude DIY one. Not too bothered about efficiency.

Here's what I've done but am not getting 5v. As previously mentioned the output voltage
vin * duty cycle which is 5.1v. Am going to stick this into a 3.3v reg.


texts:
Now I am not getting how the second equation is made. Because how can you measure VBC? Because then it will be like measuring the potential difference between two split wires... Something like this...

So is that possible?


texts:
Is there a cable-connector type on earth which is twisted shielded and uses BNC connectors as terminals? My data logging instrument has differential inputs with many BNC connectors. If I use an ordinary coax cable then it will not be twisted and pick up more noise, but if I want to use twisted then I cannot find a twisted shielded cable with BNC terminal. I need single pair twisted shielded cable with BNC terminals for each channel.

Does anyone have any experience with such issue?


texts: What is this connector on my UPS called?

texts:
I need to get a hold of a connector to mate with the socket in the following image, but I don't know what this type of connector is called.

The socket is an external battery connector on a PowerWalker UPS.

Can anyone help me identify it?


texts: Why have a bottom mounted pad on a component and not use it?

texts:
For my design, I am using the ICM-20689. The pinout for the chip is taken from the datasheet:

Once I get to the bottom of the datasheet, I notice that there is a bottom-mounted pad that is not mentioned anywhere else in the datasheet.

On the manufacturer's website, they have a link to SnapEDA for the PCB footprint and there is no bottom-mounted pad here either.

So, is there a reason why they would manufacture the chip with a bottom-mounted pad that is not supposed to be used?


texts: Are pull-up resistors mandatory for inputs on modern parallel ports?

texts:
Here I go again testing more circuits on two computers with each reporting completely different data yet I feed the same data in.

Now this time, the data coming back is all logic highs on my laptop and on my desktop, more accurate data.

I did read somewhere that older parallel ports were TTL and had internal resistors in them that helped defined their default logic level (I assume my desktop), and I also read somewhere that some parallel ports are open-collector (my laptop?)

The status pins of the parallel port are connected to the outputs of a 74HC157 multiplexer through 100-ohm pull-up resistors.

I also heard about using pull-up or pull-down resistors for the status lines, but I'm not really sure since parallel port technology has changed over the years (heck, the internet has too!).

Should I really use pull-ups (I'm thinking 10K?) and assume the output of 74HC157 is too weak for the parallel port to detect?


texts: How does square metal plate antenna work?

texts:
I have a GPS receiver(works at 1575.42 MHz) with chip-antenna:

As I understand, this metal square plate is an antenna which is connected to PCB with short 5-6mm metal rod. This metal rod is hidden iside the black ceramic enclosure seen on the image. However, if I read abount antenna basics, then antenna lenght should be 1/2 or 1/4 of the signal wavelenght, i.e. 9.5cm or 5cm respectively because wavelenght in case of 1.5GHz is 0.19m. How does this square metal plate work as an antenna?


texts:
I am building a homebrew 8-bit computer on breadoards and PCBs with TTL logic IC's (LS, HCT and ALS families).

This is a small portion of the circuit (3 modules):

I'm using an ordinary phone charger to supply the required 5V, but some IC's are getting only 4V or less, even though it's working OK that's not good at all.

The total current required is pretty low, around 200mA, very within the power supply range. I've tried with a few different power supplies with no success. I've done some research and found out that cell chargers are regulated, so it wouldn't be a problem.

The computer has 6 modules, the module closer to power supply reads 5V on its IC's, and the more it gets away from power, the voltage gets weaker.

I tried to make a power rail directly connected to each module, with same results.

I could put the modules schematics here but it would make the question very long, so I will provide the links to them:

1- Clock & Sequencer

2- Program Counter & Memory

3- Instruction Register

4- Control Unit

5- Registers

6- ALU

Modules 1 and 3 are already in PCBs, the others still in breadboards.

Link to the project here.

Are there any obvious project mistake here? Any help would be appreciated.

Edit: Could it be poor quality ICs from China the cause?


texts:
I am in need of a 303 MHz transmitter.  Similar to this (just different freq):

https://www.sparkfun.com/products/10534

If I purchase the item above and replace the crystal with a 303 MHz one like this:

http://www.mouser.com/ProductDetail/Murata-Electronics/RO2043/?qs=Ps7QaYwWPwweGuQ2BJkoXA%3D%3D

Would it work?  Or would the antenna or something be wrong and it not work?

Sorry if this is a dumb question.  I am still fairly new to electronics.  I am more of a software guy.

Thanks!


texts:
I've been for quite some time now, trying to create a precise full-wave rectification of a signal coming from a CT sensor SCT-013-030.

Here's the circuit:

simulate this circuit – Schematic created using CircuitLab

Now, actually the 7805 voltage regulator is also providing regulated power supply to the remaining of the circuit, which is basically a XBee that's activating a given relay. If you feel it's required I'll update the post.

I first started by doing only a half-wave rectification. So I hadn't even the second op-amp in place, and the following was being displayed in the scope:

Basically the yellow waveform is Vin, blue waveform is V1. I must say that, considering the resistors (the same 10K at 1%), I can't actually understand that voltage boost.

When I try to apply the Full-wave rectification I get this:

Here's a zoomed screenshot of the last scope image:

I would probably say that I must first understand why am I getting such a boosted voltage  on the output, while doing only a half-wave rectification.

The input signal is around 50hz. Another thing is that the bridge rectifier is actually a 4 diodes set up.

So, after compiling all the great comments and answers I tried to implement all the suggestions. And I must say that I'm rather confused.

Here's the current circuit. Note that I left out the AC/DC conversion to simplify:

simulate this circuit

As a first approach I decided to do the full rectification, but without the dual power supply. For visibility purposes I've increased the power being used on the power cord being measured:

Afterward I've implemented the dual power supply making use of a inverting regulator ICL7660CPAZ, I got the following:

And last by not least I've disconnected whatever was attached to the power cord, and got this funky wave form:

I'm completely lost here...

So, I have to conclude that the problem is with my implementation of the precise full-wave rectifier. Even if the schematics that I'm presenting here, make sense, I'm problably not implementing it correctly.

So, bare it with me... but I feel compelled to post my breadboard image, because sincerely I'm out of ideas... the next step is to buy a different op-amp...

Let me know if you can see anything terribly wrong... needless to say that I've rebuilt the same circuit 3 different times...


texts: Convert Li-Ion battery-powered toy to regular battery

texts:
I'm no elec. engineer; I just like to do little protects like this, so please help me out.
My son's RC car is powered by Li-Ion, and I'm sick and tired for him to have to recharge it everyday for hours only so he can play with it for 5 minutes before it dies again.
I thought: maybe if I can just convert it to normal battery it'll stay for longer, and I don't mind having to buy a pack of batteries every once in a while. But daily charging for just 5 minutes is ridiculous.
So here's the circuit as it is now.

USB charging has two wires go into the board. Then there's two 2-wire cables (red and green sets) that go back to the car.
Why do I have two sets of 2-wire cables back to the car? I thought it would just need (+) and (-) in just two wires... Why 4?
And... The two batteries in it are: 500mAh, 3.2V, 1.6Wh
What do I replace them with?
Is that all even a feasible/viable project?
Thanks.


texts:
I've proto-typed a switch mode power supply with variable voltage and current control using a MAX1763 IC. I've powered it on and for the most part it works great, I can control the voltage using the pot, but the current control pot doesn't work in the slightest when testing it. I'm not sure what the issue is, any help would be greatly appreciated.

Testing:
Applied a load and attempted to change the current while the circuit is; the current draw does not change. (Vin = 2.5v, Vout = 3.3v, load is 10ohm resistor)
I've also noticed a considerable voltage drop when load is applied.

MAX1763 datasheet


texts: Generating random bits using two oscillators and a D Flip-Flop

texts:
I'm an electronic musician and computer science student I have been tinkering a lot lately with Arduino and analog ways of sound synthesis. Mainly I've been using 4093 ICs (NAND gates) to make oscillators.
I've wanted for a long time now to turn on and off the oscillator at random intervals to make percussive beats.
After some research, I came up with some papers talking about the oscillator sampling method, which uses two oscillators (one fast, one slow) and a D Flip-Flop to generate a randomized signal. (Diagram shown below)

It is noted on the research that I found that

The oscillators used are made using ring oscillators which I know nothing about.
The slow clock is mentioned to be a jittered or noisy signal, which again I know nothing about.
On some papers I've read that the frequencies must be related but that I'm am not sure what is the relation

Would I be able to use my NAND oscillators to create this random bitstream? If not, any help, reference or advice is very welcome.
Thanks


texts: RTD with a +/- 0.01 oC from its normal set value (78.37oC)

texts:
I am doing an assignement and have been asked to find a TMS for a whiskey distillary and I cannot find a suitable RTD. The parameters are that it needs to have a T range between 0 and 120 degrees celcius and an Output range between 0mV and 120mV. The input range is 0V to 12V. I have said an RTD would be the best option.
the question asks to select a suitable tempreture sensor and find an example. I have said that the RTD would be the best option


texts: pro micro timers and controlled pins datasheet

texts:
I am using a Pro Micro with a ATMega32U4, where can I find timer number and which pins that controlled?

I just found Arduino Mega: (tested on Arduino Mega 2560)
timer 0 (controls pin 13, 4)
timer 1 (controls pin 12, 11)
timer 2 (controls pin 10, 9)
timer 3 (controls pin 5, 3, 2)
timer 4 (controls pin 8, 7, 6)

Can I use this?

Thanks


texts: How does TI CC3000 wifi smart config work?

texts:
The ti cc3000 wifi chip has a special smart config mode, this is to allow the initial configuration of the wifi access details.

The cc3000 wiki page gives some details on how the process works,

The chip enters a smart config "listen" mode
Application on smart phone sends a "UDP" packet with access point settings
The chip captures this data and configures itself

I am aware of packet capture and wifi sniffing, but how does the chip "decrypt" the raw packet to get any info out of it ? I use wpa2-personal with AES on my router.


texts: How to compare an AC signal with a DC reference using a comparator?

texts:
To answer the title question, the only way I could think of is this but they don't seem to be working. The AC RMS voltage at the input is 33 V and the reference voltage at pin 3 is 2.6 V. Voltage at pin 4 is 2.2 V. The opamp output is always high even when I change the voltage 26 VAC. I wanted the opamp to go low when the voltage dropped below 30 VAC.

The reason for the large cap is that mains voltage comes in momentarily hence a protection Zener diode D2.


texts: How to write a variable from firmware to a PLC address in OpenPLC

texts:
I'm using openPLC for my project and this requires sending data from the firmware to OpenPLC. More specifically, I need to send collected data from the embedded program in the firmware to PLC addresses such as MW100 or MW101... That way I can use this address in my Ladder program to handle or calculate. Is this possible? If yes, how to implement it. I've read firmware code over and over again but still been stuck in finding it out. All about OpenPLC or its use in detail is in the following link. Hope someone help.
https://www.openplcproject.com/runtime/esp8266/


texts: How can I keep a steady voltage from car battery to power a switch even when battery voltage drops?

texts: I have a customized car with 2 engines.  I have no mechanical door opening system for the doors as I have removed it in favor of a remote-controlled electrical solenoid.  I have recently installed a capacitive switch to be able to open the doors without the remote.  Since I have the switch hooked up to the rear engine battery (that is not the car's primary drive engine), the battery tends to drop over time through non-use.  I was wondering if there is a way to hook up some sort of ups system in the car so that the switch will work even if the battery drops too low (this has happened).  I have a solar trickle recharger on order to try and help this problem, but I would like a more stable system to be able to open the doors.


texts: Help me to determine absolute encoder parameters

texts:
I see this encoder on the internet (SRM50-HFA0.)
I need to know:

What is the difference between "sine/cosine periods per revolution" and "number of the absolute ascertainable revolutions?"
What are the "total number of steps"/"integral non-linearity" and "differential non-linearity?"
Are the "REFSIN" and "REFCOS" signals -SIN and -COS signals?


texts: 555 timer giving unexpected output (astable multivibrator)

texts:
I am using this design:

The only exception that C2 is 150nF to change the timing slightly. When I plug in the circuit and attach an LED across GND and pin 3 output the LED is static on. However, on closer inspection with a multimeter frequency setting it says that it is 700Hz. Why though? This should provide a frequency of around 1Hz with these resistors and capacitors. I am using an LM555CN chip.


texts: How to reset MCP2200 to default settings?

texts:
I designed a simple USB to UART coverter using  Microchip's MCP2200 microcontroller. worked nicely for a while, but while i was trying to Update configuration using supplied config utility... the application crashed during the cofiguration was beig updated..

Now whenever i connect it to the computer, it says USB device not recognized.(malfunctioned)..

So, my question is, Is there any way to reset default settings by hardware. as it is not recognized by the computer at all.

P.S. i did not changed the VID/PID so it is not a problem of driver.


texts: Stability of a negative feedback amplifier

texts:
Consider a negative feedback amplifier whose open loop gain is A(jw) and whose feedback factor is F(jw).

We all know that the Oscillation Criterion is A(jw)F(jw)=-1

To evaluate the stability, the frequency Phase-Crossover Angular Frequency fp is defined as the frequency at which the angle of A(jw)F(jw) is -pi

and the frequency Gain-Crossover Angular Frequency fg is defined as the frequency at which the amplitute of A(jw)F(jw) is 1

I read in the text book that if fp < fg, for the frequency between fp and fg, the amplifier is not stable.

my question is for frequency between fp and fg A(jw)F(jw) is not -1, how could the amplifier be not stable?
thanks!


texts: How do I make a default on circuit the can latch off until a interrupt goes low?

texts:
I am trying to design a datalogger that should run for a long time on one set of batteries. I have a RTC module that has a interrupt wire that is high when powered on and goes low when a alarm time occurs. When this happens I want to power on the main circuit, measure and then send a signal from the arduino to power off again.

I have tried to just run via a p-channel mosfet, but my electrical engineering skills are not sufficient to design a latch circuit for it. I didn't manage to get it to turn on when the power turns on...

I would be thankful for some help.


texts:
I am looking at establish a circuit allowing to detect when one or two wire are cut such as a tamper system. When the wire are cut it should signal this a GPIO.
I suppose I need to use a transistor connected to GPIO but I have a bit some difficulty to see how.


texts:
I'm trying to identify a fuse part that says 125V T 2A on it.

It seems to be a solid state fuse soldered in place. IE I can't just snap in another replacement fuse in a glass tube like I'm accustomed to. So I need to desolder this one and solder in another. Anyone know where I can order one or if it would be possible to put in a holder for a more regular one?

I'm hoping I'll do better here than with the no-comment public post on Google+ I had.


texts:
This is a follow-up to my previous question. I am trying to increase the spark gap distance of an arc lighter without increasing the supply voltage - I'm using a 3.7V li-ion battery to power it. I'm getting a 3.5mm gap at the moment.

I'm using two MOSFETs in parallel to decrease Rds(on). The collector current is about 1A when the secondary of the transformer is sparking. I tried decreasing R1 to increase the collector current. This worked, but didn't make a significant difference in spark gap distance.

I noticed that there's a lot of noise at both sides of the primary. I filtered out the noise at the supply using a 47uF decoupling capacitor. The signal at the collector does not appear to be a square wave - it is very choppy and includes 125V spikes. I tried to filter this out using a revere-biased 3.6V Zener diode with a current limiting resistor (limiting the current to around 20mA). This did not fix the voltage spikes and the choppiness of the primary input. The below picture shows the collector voltage before and after sparking/conduction.

I also tried different frequencies and duty cycles, and this one seemed to be the best. I have considered a DC-DC converter to step up the voltage into the primary, but that would be too bulky based on the currents I'm dealing with.

Any suggestions? I'm open to redesigning the circuit.


texts:
I am using a TI LM4510 converter (datasheet) to step up from 5V to 12V (adjustable). I have good input power, enabled chip, and followed datasheet, but the output voltage is actually lower than the input. I've attached the schematic and board footprint. Any ideas on what's going on?

Thanks in advance!


texts:
For school I have to build a astable circuit that stays on for 5 seconds and then turns off for 1 second. However my circuit isn't working I am do not know why here is my circuit on a bread board. The led stays on but never turns off.

The schematic can be found here for the output I added 1000ohms resitor. R1=680kohms and R2=145kohms


texts:
I am new to electronics and have used flashing LEDs with chips built into them before now, but this time I am going to be using 8 LEDs total, and want them to stay in sync.

I want to have a setup where the output switches between two different outputs which each have four LEDs every 1/2 second (or thereabouts).

PS: I know I have to have resistors because the LEDs need 3.3v, and ill provide them 9v. I'll be using 240 ohm resistors when I build the project

Is there any way to do this?


texts: Voltage Regulation for a high frequency signal - Arduino Input

texts:
I'm trying to build a digital tachometer for my motorcycle using an Arduino nano. I have researched a lot on how to reduce the 12 volts from tach signal to 5 volts to be read by the arduino. One post here suggests using a voltage divider using zener diode.

The tach signal from the motorcycle is a square wave and quite high frequency. I'm not sure if the zener diode can handle frequencies like this. I'm not sure how the frequency is calculated but if its coming from the alternator, it will be very high.

Since I'm completely new to electronics, I would like to know if this will work with a zener diode or i should be changing something?

Thanks,


texts: How do professional designs compensate for offset voltage in opamps?

texts: I am new to electronics and have been told in class to always add precision potentiometers to compensate for input offset voltages in opamps for signal conditioning. My concern is that this offset voltage is inherent to the opamp IC and is different on each instantiation of the circuit. How do professional designs made for massive production deal with the problem of offset voltage? Do they adjust potentiometers after manufacture  for each board to check that they are adjusted? This sounds impractical. Do they use other tricks to get around the problem or perhaps simply use better opamps or tailor the design to avoid depending on individual IC parameters variance?


texts:
I am trying to run PSpice netlist in SIMetrix .cir and it says

NOT valid mode type SIMetrix from Netlist, do we have to add any command other than this.


texts:
I have looked around on SE but couldn t find anything that worked properly for me.

I am looking for a way to convert a 4 bit signal_vector to an integer. However I do calculations on signals as well. This means I need the library called

use IEEE.std_logic_arith.all

This is (the condensed version of) what I have so far:

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;
USE ieee.numeric_std.ALL;
use IEEE.std_logic_unsigned.all;

    signal counter: std_logic_vector(3 downto 0);

    counter<=counter + "0001";
                ...

       if ((to_integer(counter)) < (to_integer("0100"))) then

      -- do something

      end if;

this gives me the following error: Identifier "unsigned" is not directly visible.


texts: VHDL: Using '*' operator when implementing multipliers in design

texts:
Present day FPGAs have built in DSP blocks, the latest FPGAs even have built in IEEE-754 compliant floating point units.

It is possible to create DSP entity/module using a GUI after selecting the required parameters in it, and then instantient it in the design.

When do we need to do such micromanagment in a design of instantaiting actual DSP blocks and when do we just enter a '*' operator in the code and let the synthesis tool handle the low level details? Which is better?

There are many different type of multiplication algorithms when it comes to binary multiplication. Since now we have built in DSP blocks on silicon and even built in floating point multipliers, does this mean that all those algoriths have not effectively become obsolete.


texts: Is it possible to make decimal computer using binary technology?

texts:
I have a question about computer architecture fundamentals. About binary system. Well, I know, computer doesn't use decimal (base 10) system to operate, it uses binary system, because there is a technical problem about transistors, and signals. Well, I know that only two states ( + and - ) system is comfortable for transferring information, because if there is more state, then there is big chance of information error. and of course transistors have only two states too.
.
.
Yes, well, but I have a question, why don't we just group every ten transistors together, so we can use computer in our natural system - decimal. I mean, ten transistors,

so if the first one is active and other nine are off - it means 0,
if the second one is active and other nine are off, - it means 1,
if the third one is active and other nine are off, - it means 2,
if the forth one is active and other nine are off, - it means 3,
.
.
.
.
if the tenth one is active and other nine are off, it means 9.
.
So we can use decimal information, instead of binary. This one group of ten transistors will be one "bit". And, so this one "bit" can express ten different values, instead of only two.
.
So, why we can't do that? I think it would be great to make a computer that just uses decimal system.
.
What would you say about that?
Thanks...


texts: Overcoming a boost converters soft start function

texts:
I am using a TPS61235p to boost a 3.7V 18650 battery to 5.1v with a pure-resitive load of 2Ω.  I expect it to draw 2.5A, but upon pulling the enable pin high the output current is limited to about ~1.75A due to the soft-start functionality described on page 10 of the datasheet.

I have confirmed this by increasing the load resistance higher than the Fig 8 Minimum Load Resistance at Startup, and then bypassing my increased resistance, confirming I now have the proper output.  The booster never comes out of soft-start unless the load resistance is increased first, then reduced after the booster started switching.

The enable pin is controlled by an Arduino, so now I'm wondering how do I decrease the load resistance once I've enabled the booster.

My first thought was to put a resistor in-line like I am now, and then use a N-channel MOSFET to bypass the resistor after the booster has started.  But is there a more robust / effecient way to do this?

Forgive my cramped circuit, I'm still learning.

SYS is VCC, battery voltage unless its being charged
VOUT goes
straight to the load
EN and INACT go to the Arduino


texts: Can a soapbox-sized device dissipate 10-15W of heat? If yes, how?

texts:
Some time ago, I built a soapbox-sized battery testing device. One of its functions was to discharge batteries at a specified current, and it handled most of the common battery sizes well, but its maximum discharge current was quite limited. Thus I didn't need to worry about heat dissipation.

I'm now designing an enhanced version, and this time I want to support draining middle-sized batteries (like the ones in cordless screwdrivers, they are around 12 Wh) in reasonable time. I'd be happy if I'm able to dissipate around 10-15 watts of heat in a device with the same form factor (think 85×60×40mm or similar). The heat-producing element is a TO-220 MOSFET. I'm thinking about either heatsinking it (and selecting a plastic enclosure with vents), or using an aluminum box, with the MOSFET dissipating directly to the enclosure. Would that work? Which approach is better (and of course, other ideas are also welcome)?

I'm quite new to this, so links, recommended reads, calculators and stuff would also be greatly appreciated :)


texts:
I've came across some products that help you troubleshoot a computer that won't POST, with listening and capturing traffic on PCI bus during system startup.

They essentially know the normal procedure, and can tell you what is not going on as expected.

I know conventional PCI is a shared Bus, which means you can sniff the traffic that is not even addressed to you just by listening on the bus. You don't even have to introduce yourself to the controller since you are not going to send anything.

But these cards have a PCIe port too. Isn't PCIe a Peer-to-Peer connection? How are they capturing traffic that is targeted to other devices?

And is it possible to use an FPGA that doesn't have a dedicated PCIe endpoint integrated and isn't fast enough to operate on a 2GHz bus?
Does the bus operate on a lower speed during POST or device initialization?

And after all, is it gonna work on newer hardware? Do they broadcast any useful messages during POST?

Thanks.


texts: Having Trouble Identifying Crystal Oscillator Symbol

texts:
I'm working on a circuit implementing the TI CC2640R2F (Datasheet) which requires an external 24MHz crystal oscillator to function. In the schematic (pg. 42), it shows what looks like a normal oscillator symbol but with extra brackets and wires on it.

Excuse the poor drawn in IC connections, pin designations are on pg. 10 and state that this X24M_N/P are "24-MHz crystal oscillator pin 1/2". I have 3 questions:
1. Why does the symbol look like this rather than the standard oscillator symbol
2. What are the four different pins?
3. Why does the oscillator right next to it in the schematic use the normal symbol?


texts:
I have purchased this item locally in the past and basically its 5 wires aligned in parallel, and makes my circuitry much easier (eliminates the needs to manually connect 5 individual wires side-by-side). They are however running out of stock and I'd like to buy more. In fact, If such a thing exists, I'd like to buy this project where there are 8 connectors on each side instead of 5.

The closest thing I could come up with is searching for a DIP resistor, but what ebay returned to me is a 22 ohm DIP resistor, however, I'd like something that has zero resistance. I searched for 0 ohm DIP resistor and found nothing.

Is there another name I can use as a query for this part?


texts:
I have a board that I intend to control with high fidelity differential analog, I'm aiming at one part in 216.

I want to connect the two boards with a COTS connector that solves most of the pick-up problems, without the cost.  I am considering using a SATA cable since it appears to be twisted pair and shielded.

Are there any issues using COTS digital hardware to run analog signals?  If so what would you suggest instead for COTS analog connections?


texts: Odd bypassed resistor network in the representative circuit of an MC7805 - what does it do?

texts:
Another question recently asked about the MC7805, and linked to its the datasheet for the generic MC7800-series of regulators1.

When I read it, I noticed Figure 1, Representative Schematic Diagram, and there is a construction that I can't understand, which I have highlighted in the following image:

As you can see, there are a bunch of resistors, all of them bypassed! I know that the diagrams in these datasheet are only representative, so I suppose my question is:

What is this supposed to represent?

My guess is that it's related to one of the protection modes: current limit, thermal shutdown, and/or safe-area compensation, but I can't understand how - the resistors are apparently completely and permanently bypassed.

1) I originally assumed it was specific for the 7805 variant. Brian Drummond pointed out in a comment to an answer that it is generic, which makes the purpose of the resistors easier to explain.


texts: Connecting switch-mode power supplies in series to increase voltage

texts:
I have two identical 48 V switched power supplies, both of which can deliver the same current of, say, 4 A.

Can I connect them in series to get 96 V at 4 A? Is this something possible / recommended?


texts: Keeping output of a phase shift oscillator in-phase with another sinusoidal signal

texts:
I have a sine wave source and a phase shift oscillator which gives out sine wave. The sine wave source is not always enabled. It may be turned of in arbitrarily time periods.

I want the phase shift oscillator to give out a sinusoidal signal in random phase when the sine wave source is disabled, and be in the same phase when the sine wave source is active.

I'm looking for a simple solution like injecting the sinusoidal signal from the sine source to one of the opamp inputs at the oscillator.

How do I implement this system?


texts: How can I relay 120VAC with a raspberry pi?

texts:
I have five 75W 120V AC LED lamps on a dimmer switch. They draw 13 watts each (375W total). I also have a 600W Lutron dimmer switch hooked up but the thing buzzes when the lights are dimmed. I also tried a Leviton dimmer with the same results. I've heard about debuzzing coils but seems to be that many folks have mixed results with them.

I'm wondering if I can just wire each of the 5 bulbs to a relay of some sort and then use a raspberry PI to control the relay (the PI is already wired into my home LAN so I can put an app on my smartphone to control the relay). This way, I can turn only one lamp on for dim lighting and all 5 for full brightness. No, it's not true dimming but at least it won't be buzzing.. I hope.

What kind of relay should I use? Looking on Ebay for a 120V AC 8 channel relay I found this but not sure if this beast will work.  I just want to use the GPIO pins on the PI to trip the relay so it seems pretty straightforward. The listing says the relay is good for 2A per channel and if I did the math right, that should be well within the 13W per bulb (13W / 120V = .1A)

Anyone have some thoughts as to what the best method would be to implement here? Should I go with a Triac relay instead (not sure what that is but will look into it if that's a better way to go).

Thanks!


texts: How exactly do 1950's rotary phones receive phone calls?

texts: What happens start to finish. For example, how does the signal get from the central office to the phone and what mechanisms within the phone move to signal that a phone call is coming?


texts: Selecting a MOSFET to Drive a coil with square wave

texts:
I need help with finding an alternative to IRF1310 in the circuit shown. The circuit is going to be controlled with a microcontroller with logic 3.3V. The simulation of the below circuit on LTspice shows the signal forms shown in the figure and was successful in doing what was intended, but the current at the gate is high (1A peaks every cycle).

The input signal is a square wave, simulated as a source but in the application it will be microcontroller output with frequency around 3MHz. The reason I am not using a more complex circuit is that I need to fit everything on a coin-sized PCB with the least number of components used (cost reduction). SMT is preferred if available I need to keep the date current to a level that can be driven directly by the microcontroller.


texts: STM32F103 SPI MISO doesn't work as expected

texts:
In one of my small projects I use STMF103C8T6 as MCU and SPI memory W25Q128 of Winbond to store a data. The memory chip connected to SPI1. Here is a part of the scheme:

The code is mostly generated by CubeMX. I've only added some code to communicate with the memory chip:

Initialization:

SPI_HandleTypeDef hspi1;

static void MX_SPI1_Init(void)
{
  hspi1.Instance = SPI1;
  hspi1.Init.Mode = SPI_MODE_MASTER;
  hspi1.Init.Direction = SPI_DIRECTION_2LINES;
  hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
  hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_32;
  hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi1.Init.CRCPolynomial = 10;
  if (HAL_SPI_Init(&hspi1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
}

W25Q128 code:

#define CS_Pin GPIO_PIN_3
#define CS_GPIO_Port GPIOA
#define ChipSelect() HAL_GPIO_WritePin(CS_GPIO_Port, CS_Pin, GPIO_PIN_RESET)
#define ChipDeselect() HAL_GPIO_WritePin(CS_GPIO_Port, CS_Pin, GPIO_PIN_SET)

#define COMMAND_IDENTIFICATION 0x90

uint8_t buffer_tx[4];
uint8_t buffer_rx[2];

uint16_t GetIdentification()
{
    buffer_tx[0] = COMMAND_IDENTIFICATION;
    buffer_tx[1] = 0x0;
    buffer_tx[2] = 0x0;
    buffer_tx[3] = 0x0;

    ChipSelect();
    HAL_SPI_Transmit(&hspi1, buffer_tx, 4, 1000); // send 0x90, 0x0, 0x0, 0x0
    HAL_SPI_Receive(&hspi1, buffer_rx, 2, 1000); // receive 0xFF, 0xFF
    ChipDeselect();
    return ((uint8_t)buffer_rx[0] << 8) | (uint8_t)buffer_rx[1];
}

int main(void)
{
    MX_SPI1_Init();
    HAL_Delay(1000);
    uint16_t id = GetIdentification();
    printf("Manufacturer ID: 0x%.4X\r\n", id);
    while
    {
    }
}

According to the datasheet to get chip manufacturer code I need to send 0x90 and 3 dummy bytes. The chip should return 0xEF, 0x17. But for some reason I receive 2 bytes of 0xFF. Ok, I've changed the chip twice in the PCB but without results. I still receive 0xFF, 0xFF. I've connected logic analyzer to the chip on the PCB and to my astonishment I get the following picture:

According to the diagram everything is Ok. The chip sends 0xEF, 0x17 as expected. But for some reason my STM32 doesn't see that.

I've rechecked the PCB, I reinstalled a few chips, I've tried W25Q128 and W25Q64 - all failed, I receive only 0xFF, 0xFF instead of real data. What could it be and how can I fix that?

The full project is here.


texts: I have to find all the voltages and current in the circuit

texts:
I am given Uab=100V

XL=6Ω

XC=3Ω

R=4Ω

This is how I started

X=XL+XC=9Ω

Ztotal=sqrt(R^2+X^2)=9.84Ω

Zab=R+jXL=4+j6=7.21∠56.30

I=Uab/Zab=100/7.21=13.86A

but obviously I made a mistake somewhere

U=I*Ztotal=13.86*9.84=136.3V

Uc=I*Xc=13.86*3=41.58V

UL=I*XL=83.16V

UR=I*R=55.44v


texts: Switching relay directly with an optocoupler

texts:
I have a relay network (more than 1 relay running in parallel), that I need to operate using a STM32 based MCU.
The relay I am using is Omron G5V-1 (24v).
I wanted to know if I can directly run these relays with optocouplers such as PC847.
Looking at the calculations, G5V-1 has a nominal power usage of 150mW @ 24VDC. So technically around 6.25mA. Each opto-isolator block in PC847, is rated at a max of 35VDC and 50mA, which is well above the safe range for driving the relay coil.

Is it really necessary for me to add an extra transistor, diode and
a resistor as the relay driver?
What are the tradeoffs of not using these and directly running off the optocouplers?

Have seen similar questions (Driving relay directly from optocoupler, what is best?, Why is transistor needed when using a relay?) though, but haven't been able to draw conclusions.
Adding Schematic:-


texts:
How would I send 32bit data values using SPI of K66.. here is my attempt. The problem is only some parts of the 32bits are shown in the scope

status_t ADF4158_GenericWriteReg(pll_register_t reg, pll_params_t *params)
{
    dspi_command_data_config_t command;
    uint32_t value;

    if(reg >= kPLL_MAX)
        return kStatus_Fail;

    /* obtain formatted register value */
    value = ADF4158_GetFormattedRegValue(reg, params);

    PRINTF("Writing Register R%d with value 0x%08X\r\n", reg, value);

    /* Define Chip Select  */
    command.whichCtar = spiCtar;
    command.whichPcs = spiPcs;
    command.isPcsContinuous = true;
    command.isEndOfQueue = false;
    command.clearTransferCount = false;

    /* upper 16 bit */
    DSPI_MasterWriteDataBlocking(spiBase, &command, (uint16_t)(value >> 16U));

    /* lower 16 bit */
    command.isPcsContinuous = false;
    DSPI_MasterWriteDataBlocking(spiBase, &command, (uint16_t)(value & 0x0000FFFFU));
    ADF4158_DelayFunc();

    return kStatus_Success;
}


texts: Why don't battery manufacturers make 5 V batteries?

texts: Why is it so? Is there something that cannot be crossed while manufacturing 5 V batteries? They can make billions though! Still...


texts: "Side channel" information on laptop audio jack?

texts:
I'm playing around with an oscilloscope and my laptop's headphone jack. I get the tip/ring/ground and measure between them. I also measure between them and an external reference ground. I notice I can see when the battery is charging. That is, if the battery is not in the laptop but the AC is in, then I insert the battery, it runs through a few seconds of a test, and then if the battery is not full, it goes to a certain waveform – if it is full, it goes to another "quieter" waveform. This is best done when the laptop is turned off otherwise the waveform is quite noisy.

I'd like to be able to understand more about what is going on. Might there be any other data present in the signal on the headphone jack if I am not putting out an audio waveform? ie. by virtue of the circuit passing through some of the data processing elements of the motherboard, when the computer is powered on? There is a lot of noise in the signal but maybe it is possible to clean it up some.

I thought this was interesting as it is a similar idea:
http://cs.tau.ac.il/~tromer/acoustic/ (Here the noise comes from a bank of 1500µF capacitors).


texts: Reading a serial data stream with Verilog

texts:
I'm using an FPGA to sample a serial data stream (happens to be PCM audio in this case).  Basically, there are two signals:

Bit clock: a basic clock signal (square wave)
Data: the bit to be read is present on the rising edge of the clock

Currently, I have an asynchronous edge detection on the bit clock.  So basically, a flag will go high for one clock cycle when the bit clock is on the rising edge.  My approach was to wait for this flag.  When the flag goes high, I take the value of the data line and put it in an index of my buffer.  However, I don't think this is working correctly.  Can I not just sample the hardware value of the data line?  Do I need to buffer it?  Here is my code for reference:

always @(posedge clk) begin // posedge of system clock

    if(bclk_rise == 1) begin // Rising edge on BCLK detected, sample the bit and place it in the correct buffer index

        audio_data[data_count] <= data; // 'data' is the wire type that's connected to the ADC data line

        data_count <= data_count + 1; // 5-bit value, gets reset to zero every 32 loops

    end

end


texts:
I have recently designed a passive-based modular PCB.

When I click the secondary board into the base board, I would like it to break the current circuit at a fixed point, and insert itself in series instead:

I could easily connect the secondary modification board in parallel with the wire connecting the two passives halves, but then I must break the wire connection for it to be in series, so I have a plan.

I remember back to my childhood days when McDonald's toys had little white pull-tabs that you needed to pull out before they became operational.

One way or other, the pull-tab would keep the circuit open and close it when removed. The easy way to do it would be to place the tab between two small coin batteries, with the spring pressure holding it in, but I have seen toys that have the tab on the side away from the batteries. I suspect the circuits inside are using two plates that push against each other on the PCB, and would close the circuit without the tab being inserted between them.

I would like to do the same thing in my design, only with a permanent tab on the underside of the secondary PCB and the contact plates on the base board. When I clip the secondary board into the base board, the insulator tab pushes the contacts apart, allowing the connected modification to be in series with the rest of the circuit.

Are there parts out there already that are designed for this? Maybe something similar? The boards are passive, so non-mechanical options are not viable.


texts: Can you use an FPGA / verilog to accelerate SAT / SMT solving?

texts:
I am aware that SAT and SMT are widely used in hardware verification. This would tell me intuitively that trying every input on a circuit is slower than porting the circuit to a solver. However, we have ASICs for computing SHA256 faster in mining Bitcoin, so my thought is why not for SAT?

I would like to build something that takes CNF SAT expressions (later on SMTLIB) and generates Verilog for them. I am not sure if it would be faster to pipe test inputs back and forth over USB or write a little harness to run within the Verilog. Either way, I'd like to offload the expression testing onto an FPGA. I figure generation + device programming time will be fixed (say, 20 seconds) so it will only make sense for longer running solves.

Is this feasible or is there something about SAT solving / FPGAs I don't understand?


texts: How to specify in the project or firmware of the application, where to start writing the code?

texts:
I have a bootloader to PIC18F4550 that was written using Mikro C for PIC and I have two firmware applications, one was written using Mikro C for PIC and the other using MPLAB X with XC8 compiler.
With the bootloader installed, I can upload the application written in Mikro C without problem, but, with the same bootloader installed, when I try to upload the application written in MPLABX I can't. I load untill 100% but, in the end, it crashes.

In the bootloader code there is the following code:

const unsigned long BOOTLOADER_SIZE   = 8000;//7432;
const unsigned long BOOTLOADER_START  = (( __FLASH_SIZE - BOOTLOADER_SIZE) /
_FLASH_ERASE) * _FLASH_ERASE;
const unsigned char RESET_VECTOR_SIZE = 4;

I suspecting that the firmware application is interfering in the part of the instruction space that the bootloader occupies. I did nothing in the XC8 application to ensure it does not overlap the bootloader already present in the device, I just compiled it and use the .hex file to be uploaded.

At this moment, my firmware application does not need to invoke the bootloader and does not need to use any I/O resources that are also used by the bootloader.

I tried to modify linker comands, in a .map file, but I don't know if this is the way. I didn't put it here because it is too extensive

Does someone know, or has a tip, of how to configure MPLABX, or write in the application's firmware, to guarantee it does not overlap ?

Following are two images of the configuration project that MPLABX provides. Remembering this is the project of the application firmware.


texts: Identify these potentiometers or variable capacitors

texts:
I recently came across an old radio that has these odd parts on them. They are labeled "T3" and so on, so maybe they're some kind of capacitor or transformer?

They're adjustable at the top and branded/stamped "JET" around the adjustment screw.

In the last picture, I carefully dissected one and it's just thin copper wire wrapped around what seems to be a ferrite/iron core.

Any ideas?


texts: How to wire up camshaft position sensor in lab environment?

texts:
I have taken out this camshaft position sensor out of my Chevrolet Aveo 2007 and I am trying to verify whether the issue I am facing is with the sensor or the ECU/computer (the car cranks, but does not start and had P0340 code).

My question is - how do I wire up this camshaft position sensor in lab environment (without car in the picture) to verify that it is working according to its specification?

Additional info:

The harness that plugs into sensor has 3 wires (Pink, Black, Black&Blue). When I turn car key to ON position with harness unplugged from sensor, then

voltage between Battery Minus and Pink Wire slowly grows from 2V to 12.2V over 10 second period;
voltage between Battery Minus and Black Wire stays at 0V;
voltage between Battery Minus and Black&Blue Wire stays constant at 5V.

With sensor plugged into car's harness and intercepting with oscilloscope between Black Wire and Pink Wire at the time of Cranking I see that 12.2V voltage disappears and there are "squarish" pulses that don't have steep triggering edge with lows of 0V and peaks at only ~2.5V:

Here is schematic from my car (BK - black, PK - pink, L-BU/BK- Blue&Black wire):

I guess this is confusing me because this sensor does not have a simple Output pin where ADC in car's ECU measures voltage. I am not sure:

which electrical property (current, voltage) is supposed to change on which wire when camshaft position sensor detects tooth on reluctor ring.
why voltage on Pink wire slowly grows from 2V to 12V. And when I crank, then oscilloscope shows waves of 2.5V peaks between Black and Pink wire. Was it supposed to be constant at 12V?
W.R.T. #2 as test would it be safe to connect Battery Plus to sensors pin where Pink wire previously went in to eliminate problem of voltage slowly rising to 12V?

After adding 10KOhm sensor, as suggested in one of the answers by JRE, I see that rising edges in the oscilloscope are now steep. This probably proves that problem in my case is not with the sensor, but rather somewhere else in my car's electrical wiring.


texts: What kind of start is good for GPS modules used in Tracking

texts:
I came across Cold start,Warm start and Hot start in GPS Modules while developing code for a GPRS Tracker. I know the difference between them.
But when I use hot start method,signal is acquired faster but at times empty NMEA strings comes that affects the tracking. Which would be the best starting method I could use in this case? Module used is 'Global Top GMS-G6'


texts: Low Power Timer That Becomes Dead Short at Intervals

texts:
(Edited based on feedback)

There are two parts to this question:

1) Does the thing I describe below exist already in pre-packaged form, IC, etc.

2) Is the thing common enough to have a name that I can google more about?

And here's the thing:

I want a component that can be connected to a power supply that provides 5V at up to 1W.  The component acts as a low power (<<1mA drawn), high resistance timer for interval N and as a dead short (to an output line) for interval M, where N would vary from minutes to days, and M would vary from milliseconds to perhaps up to a second.  Intervals M and N would alternate indefinitely, input line would always receive voltage/power, and the external load would always be attached to the output line.

If I've left something out that would help answer this, please point that out, I'm an electronics noob so this may be underspecified as it stands.

Also, the specific numbers I used aren't hard and fast, but they illustrate the operation I want.  Any solution should behave conceptually the same if the power supply varies, e.g. 12 V at 10 W, etc.

Context for this question is that I am trying to find a component that can  take power input from either/both a storage unit or generator (both in the same range of voltage/power) and supply this to the load (solenoid) only at the active (M) intervals, while during the off intervals (N) the generator stops supplying power and the storage provides enough to run the low power counter until the next on interval.  When transitioning from off to on intervals, the storage has enough stored energy to supply the load for a short period at which point the generator kicks in.  None of this is part of the component in question, just providing this context by request, and in case it helps answer.


texts: 12 Volt from solar panel converted to 120VAC without battery

texts:
I have solar panels that will supply about 200 watts. (They are rated for 400 watts.)

I have a load that needs about 150 watts, 120 Volt AC, off grid, and only when the sun shines.

The 12 volt solar panels have an open circuit voltage about 17 Volt.

All the 12V inverters have an input range 10 to 15 volt, and 17 volt is an overvoltage.

I don't want to use a battery because I don't need to store the power. I don't want to invest in one, batteries don't last long.

How can I overcome the mismatch of the panel output voltage and inverter input requirement?

How can I do it inexpensively and without losses? (Like voltage regulator, or DC to DC converter.)

Grid tie inverters have larger input voltage range, but I don't want to connect to a grid.


texts: how to automatically reverse the direction of a stopped gear motor and restart 12 hours later

texts: The reversible gear motor needs to turn on @ 6:00 am pull a object 12 inches and shut off.  Twelve hours later the gear motor needs to turn on and reverse the direction and place the object back in place.  A timer would turn the motor on and a contact switch would turn it off but how would you get it to reverse direction and stop it at starting point?  What other pieces of equipment are required and how would it be wired.  The object being moved would be connected to a chain.  The object could also be connected to a actuator?


texts:
I’m beginner in electronics and i have project for grow LED light and i want to connect LED with timer. My inquire how I protect my circuit.
My circuit

Adapter
12V 1.2A

Timer
(5-20v) up to 5A

2 * LED CHIP
(6.6V 0.300A) 2W
One led (3.3V 0.300A 1W) i will conect series.

I want be sure 6.6 V will be arrive to LED chip not more to damage my LED
I’m waiting for your recommendation.

Thank you

Is this circuit correct ?

simulate this circuit – Schematic created using CircuitLab


texts: What should a contract Electrical Engineer deliver once a project is complete?

texts:
I'm getting ready to hire an electrical engineer for a small contract job - creating a prototype.  What I'd like to know is, what should I have him deliver to me when the project is complete?

I imagine schematics, the prototype, parts list would be standard, but what am I missing?  Should I ask for an auto-cad file - not sure what this is yet...  Are there other things that I would need in the future for a different engineer to take over the project?

Simply, what should I be asking for?


texts: Problem related to phase spectrum of DSB-SC signal

texts:
I have tried to solve this question (4.2.3). I got the magnitude spectrum right but the phase spectrum wrong. I am getting the phase spectrum at \$ \frac{\pi}{4} \$ and \$ - \frac{\pi}{4} \$. However, in the solution manual, they have plotted it at  \$ \frac{\pi}{2} \$ and \$ - \frac{\pi}{2} \$.

The phase is visibly at \$ \frac{\pi}{4} \$ and \$ - \frac{\pi}{4} \$ from the coefficients \$ e^{- \frac{j\pi}{4} } \$ and \$
e^{ \frac{j\pi}{4} } \$ in the two terms.

I am not able to understand why am I wrong and why are they right!


texts:
I am working on a battery charger/discharger. I am now looking to enhance it to support discharging at various rates (i.e. currents). I would like to have some way to control this discharging current programatically from the Arduino  in increments of about 50 mA ranging from 0 mA to around 500 mA. The voltages involved will be in the 0.4V to 2.0V range.

A useful solution would be where I can output a PWM signal from the Arudino which contains the information on the desired current. Then I need to have a circuit that can react to this signal. The question is how the circuit should work. Conceptually, it should be like a variable resistor, accepting the input from the Arudino. I have searched a bit around and found some suggestions of using a power MOSFET for this purpose. But I am wondering if a general MOSFET could be used or a specific one. I havent found a MOSET with a data sheet giving an exact current for given gate voltages, which seems to be a requirement in order to employ the MOSFET for this purpose (at least naively, with the gate current coming from the Arduino). Anyone who has any suggestions? Either with the MOSFET space or something completely different?


texts:
I am designing a PCB with a A20 (allwinner) SoC. This SoC has a SATA 2.0 host (RXP RXM TXP TXM) that I have to route to a M.2 "M" key connector.

I found only one source for pin out, but I can't find confirmation of this pinout. Anyone can confirm if this is correct? I should connect only the 4 data lines, GND and 3.3V pins from the list there right?
Should RXP RXM TXP TXM be controlled in impedance and if so what is typical value for them?
What is the dimensions between the NGFF connector and the screw hole for 2230, 2242 and other formfactors? I guess the screw hole position in each formfactor is a standard to enable compatibility, same as screw hole position on the motherboard. However I can't find this information anywhere. I asked NGFF connector manufacturer but had no reply so far...
I know 2242 stands for 22mm wide 42mm long, but is 42 mm the total dimension of the board, or dimension to the screw hole? And from what point? Center of the connector? End of connector? End of the 2242 board?


texts: I am trying to make a digital ohmmeter on a parallel port interface that can measure resistance with at least 95% accuracy. I have tried a 555 timer monostable assembly which generates a pulse with respect to the connected resistor. My program detects the width of pulse and then after calculation gives a value of resistance, but the results are not accurate, especially for small values. Is there any IC avaliable for resistance to digital converter? The output may be serial or parallel.


texts: Trouble starting a Constant Temperature Anemometer

texts:
I made a Constant Temperature Anemometer using this and this as reference. However, I'm having trouble in making it work properly. To get the circuit started I need the emitter voltage (Bridge Top) to be negative but can't seem to get it. No papers nor discussions i searched seem to have this problem. My questions are (details below):

I'm trying to find out what happened when a closed loop circuit like this has just turned on. Specifically, where should i start placing initial voltages to do analysis?
How do I achieve negative voltage at the bridge top to make the circuit work properly?
Should I change the 10k pot in the offset circuit?

When I tried this circuit, the bridge top has a positive value. This is a problem since the current booster is a PNP. The base voltage is 13V, which is above the emitter-base breakdown voltage. I assume the problem is because when I start the circuit, the initial voltage at bridge top is positive which is then amplified 1010 times and lead to saturation of the OPA37. I tried to circumvent this using a resistor between the emitter and collector like this circuit as well as placing a diode at the base like this circuit. However, it doesn't work and the bridge top is still positive even though the base voltage is already below 1V (I already replaced the transistor and verified the OPamps are not broken). Changing to NPN yields the same problem just different polarity.

I setup the offset circuit so that the pot can output voltage between ±5V using zener. However when I connected it like the circuit shown, it can't give the full ±5V range (it can't even go down to negative). I assumed the pot value is a problem due to loading effect, but TINA TI simulation proved otherwise. Not quite sure what's going on.

Note: I used a 1A ±15V Supply and a 1W resistor in place of hotwire to achieve the same condition as the simulation since it is quite complicated to factor in heat transfer. I did try using a Dantec Hotwire and have the same problem described above.


texts:
I am simulating a basic sample and hold circuit in TI TINA. The op amp is TI TLV333.

The parameters are:

Vin - 1Hz - DC:150mV - Amplitude:1.3mV

Switching frequency:100Hz

The following two plots show the simulations under different capacitor (C2) values.

(1st: 1mF; 2nd: 1uF)

Can anyone why the ripple and oscillation occur when using smaller capacitance? Thank you.


texts:
I need to slow-charge a bank of capacitors that power a load which draws up to 150A at 12V, because I don't want to draw a massive amount of current when the battery is connected to the ~20000uF cap bank.

I thought I could do it by having a relay switch a high value resistor in series with the cap bank for a few seconds, then bypass this resistor for normal operation. However, such a relay would have to pass 150A in the normal operation mode. Many relays can't do this, because they are rated based on their interrupt current and not operational current. My application will only require 150A when a battery is plugged in, and when disconnected the relay will continue to be energised by a support circuit until the 150A load has shut down and draws nominal current. This will occur several seconds after the battery disconnect, so the actual interrupt current will be small, in the milliamp range. The 150A load is electronically controlled, and can be shut down very quickly, almost instantaneously. So, no arcing should occur on the relay contacts, which is what I believe gives them their normal current rating?

Are there any relays specifically optimised for this job?


texts: Will a DC circuit breaker trip due to high voltage?

texts:
Will a DC circuit breaker trip due to high voltage (exceeding voltage rating) or will it only trip because of high current? For example, if you have a 40 Amp DC circuit breaker which also has a 32 voltage rating would you have to keep the amperage below 40 and also keep the voltage below 32? Or do you only have to consider the amperage not going above 40?

The reason I ask this is because someone else on here asked if an AC circuit breaker will trip because of voltage and the answer was no. An AC circuit breaker will only trip due to high current and can't even detect voltage. I was also hoping this applies to DC circuit breakers as well. Does anyone know the answer to this?


texts: Parallel Capacitors with different voltages

texts:
Let's consider a capacitor precharged to 5V.

Now immagine to put it in parallel with a capacitor which has no charge. What does it happen? They reach a voltage in the middle? Does it depend on their capacitances?

In theory they are both in series and in parallel, so we will get Q1 = Q2 and V1 = V2, but this will mean C1 = C2, that is an absurd.


texts: How to Shift Carrier Frequency in QAM Signal?

texts:
If I wanted to apply a 100MHz frequency shift to a QAM signal with a 400MHz carrier frequency, I would

Demodulate it at the carrier frequency
Apply a frequency shift to the original signal
Modulate it again at the new carrier frequency

Is there a way to apply a frequency shift to the IQ values of a QAM signal without demodulating it?


texts:
I'm trying to write a code for pic16f877 by translating a simple algorithm into assembly code.

The instructions set doesn't have such an instruction.

Here is what I wrote:

MOVF 0X40,W
MOVWF 0X50
SUBWF 0X41,W
BTFSS Status,C
GOTO label
MOVF 0X41 ,W
MOVWF 0X50
label END

My question is: is there a way to "end" an algorithm when programming a microcontroller using assembly code?


texts:
I made a small bristlebot. my version can turn left and right using two vibrators and is controlled by an ATTiny uC. I would like to add remote control functionality so i'm asking what's the simplest and smallest component(s) I can add to my bristlebot to make it remote controllable? (the size of the actual remote control device doesn't matter, just the components on the bristlebot).
i want to use radio control, not IR.
I have to say, comming from the digital side, I have no experience with analog circuits and RC sender/receivers so far.

thanks for the hints


texts: Arduino or MSP430 Launchpad as a serial passthru to reprogram a Fonera router?

texts:
The Fonera has 3.3V TX/RX logic, I have a launchpad and an Arduino, can I use any of the cable/boards to reprogram or access the serial on a fonera?

Fonera serial info is here: http://www.dd-wrt.com/wiki/index.php/LaFonera_Hardware_Serial-Cable-Port#Accessing_serial_console_on_the_Fon

I am specifically asking about methods and boards not covered in this previous Q: Can I use an Arduino as a USB to serial interface?


texts: Purpose of gate driver in Class D amplifier

texts:
Can somebody explain to me why we need MOSFET gate driver in class D amplifier like in the picture below(common class D schematics)?
What I don't understand is if we for example have 9V rails, then the comparator(LM311 for example) would output PWM waveform with 9V level. If we then use MOSFET doesn't it just becomes equivalent to wire? So, wouldn't it be the same if we just connect it neglecting MOSFET driver?
I understand the concept of MOSFET amplification if we have weak signals, but for me we just converting 9V pwm to the same 9V pwm here. I was trying to see how the current changes if we place MOSFET, but also don't see the difference...
One reason I can think of is that comparator has high output resistance which limits the current, I wonder if that is true, but still if we connect 8ohm load to it shouldn't matter so much.

(source: soundonsound.com)


texts: How are different circuit form factors (SODIMM, PCIe) designed and manufactured?

texts:
Using  recent technologies, System on Chips (SoC) and other type of single board computers are manufactured on compact small boards. A common form-factor SoCs is a DIMM based or even PCIe form factors. where the entire system is laid down on the board, and the socket expands and gives access to the pins of the SoC.

What type of software is used to create these? for example, can you make a SODIMM based PCB on Eagle or KiCAD, or are there special programs?
How would one manufacture these? is it possible to manufacture these form factors in small quantities the was most traditional PCBs are manufactured?

I have designed a single board computer that i would like to make a DIMM style prototype for, any good books you would recommend ?


texts: Passive Component ratings displayed on schematic - Use actual value or design requirement value?

texts:
When placing a passive component such as a cap or resistor on schematic, most people usually place the relevant rating (usually power for resistors, voltage for caps, and current for inductors) next to the symbol in addition to the actual component resistance, capacitance, or inductance value.

However, as the design solidifies and actual physical components are chosen, the rating for the physical part may be different than (and hopefully, exceeding) the design requirement.  For example, I may need a 10V cap on a certain line, but there is a cap that is cheaper or perhaps already stocked by my contract manufacturer that is a 16 V cap but otherwise identical.  It would make the most sense to spec out the already-stocked part.

In such a case, what value should be shown on the schematic - Vmax = 16V or 10V?  On one hand, I feel that schematic should communicate design requirements, and part substitutions should be decided elsewhere.  On the other hand, the schematic also serves as a reference for the actual built circuit - so the actual part rating is more useful from that perspective.

An additional complication is that the BOM is usually generated from the schematic, and thus displaying the design requirement but then also spec'ing a higher-rated part (i.e. for stocking reasons as mentioned above) can lead to confusion if someone compares the specified requirements to listed parts.

I've read this question and the answers linked to it and haven't found an answer to the specific question.


texts: How much current for a 5V 60 LED/m WS2812B 5m LED strip?

texts: I'm planning on controlling a 5m 60 LED/m WS2812B chip 5V strip with a Raspberry Pi Zero W. According to the website it draws 18 watts per meter (90 watts total). What current would this strip draw, and what would you recommend on powering both the Pi and the strip from one PSU? Any link to some decent, budget ones would be appreciated.


texts:
I saw a dimmer on instructables and try to create circuit and pcb for it. However the it looks nice and probably will work but I'm not confident the reliability on long run.
So my question would be if this design violates some safety rules or not.

Yes I know the resistors don't have value yet but I still analyzing the datasheets of the optocouplers and the triac I have. (Probably will result more question(s))


texts: How often are bits sent over cat 5 ethernet cables?

texts:
sorry if this is a bit of a dumb question, but I read somewhere that cat-5 is 4 twisted pairs. so that means at most it's transmitting 4 bits at a time. What determines how often the 4 bits are measured in order to create a packet structure?

I know how the ethernet frame is laid out, but I'm really confused about what defines how often each bit is measured? I assume that there is a standard for each type of wiring, but I haven't been able to find it.

if the 4 bits are 1011 for 2 sec, you get vastly different data based on how many times it's measured in that one second. So that must be defined for each type of wiring somewhere i assume.


texts: What happens if I change the polarity of the battery?

texts: Suppose if i charge a capacitor. Now if I reverse the polarity of the battery, how much is the heat produce during that process? My book says as change in energy = 0 (in capacitor) therefore heat produce 2cv^2. Can somebody actually explain me what will happen when the polarity is changed and provide me with some other way of explaining this answer?


texts: Controlling High Voltage device with Arduino

texts:
I want to control lava lamps using Arduino. I think it shouldn't be hard project, but I have no experience with hardware projects so I'm not sure witch design will feet best for me.

I consider using S202T01 Series Solid State Relays (I already have two of them).  I think it's the easiest way to do it (Am I right?, Are my SSR good for that?). Probably I could use LED blinking example and use SSR instead of LEDs. I think there are some other advantages of this approach. It's safety because of optoisolation, and it can switch very fast. Unfortunately SSR are quiet expensive and I need control ten devices.

I'm looking for cheaper solution (but not much harder to use, and also safety). Me by I should use TRIACs (if yes what models)?

And one more question: how about cooling? Should I use radiator on Solid State Relays or TRIACs?


texts: Simplified eqn for inductor charge for short timeframe?

texts:
In a worked solution my professor has given me it says:

I(load) = Io(1-e^(t/time constant))

and I(load) = Io * (t/time constant) (for a short time period)

I don't understand how the second line can be true?


texts:
I have an LED bar that draws about 1.17A when connected to a 5V 1A external USB battery. The voltage across the terminals measures 4.61V.
The LED bar draws about 1.7A when connected to a 5V 2A external USB battery. The voltage across the terminals in that case measures 5.1V.
In both case, I'm satisfied with the light it gives,but with the 5V 2A battery, it is quickly hot.
I only have 5V 2A batteries, and I'd like this LED bar to be powered with 5V 1A max, so it lights up AND does not heat up.
How can I do that ?
My electronic courses are a bit far by now.


texts: Torque, Current and Voltage Relationship in Induction Motor

texts:
In induction motor, Torque is proportional to square of applied stator voltage (I agree that) but some source says torque is proportional to current. For me something proportional to square of volt should be proportinal to square of current as well. Is that right?

This source may be meaning under constant voltage torque is proportional to current? May it be?


texts: Obtaining both an Analog and Digital 5V Supply From Single 5V Supply

texts:
I'm replacing a stolen PCM4222EVM adc with a PCM4202EVM adc but they left my  + -15V, 5V triple-output linear power supply.  However, I just discovered that there is a difference in powering the PCM4202EVM in that it also requires an extra DIGITAL 5V supply, so 4 separate power supplies: + - 15V, 5V & 5V Digital.
Being a dolt, can I just solder a wire to my 5V supply and run it to the digital header or do I need to do some kind of decoupling with a capacitor setup? Also, what would I do with the grounds?
I may replace the triple-linear with a triple-switching supply if that makes any difference with adding the 5V digital.  Both would supply adequate current for the dual 5V draw btw.


texts: How do multiple mixing stages work in a spectrum analyzer?

texts:
I'm reading about spectrum analyzers from Keysight's AN 150. On page 12 they explain how multiple mixing stages are used to obtain narrower IF filters. The block diagram offered is the following one:

They state that the tuning equation would then be:

$$f_{sig}=f_{LO1}-(f_{LO2}+f_{LO3}+f_{final \ IF})$$

And that

$$f_{LO2}+f_{LO3}+f_{final \ IF} = f_{first \ IF}$$

So they say:

  Simplifying the tuning equation by using just the first IF leads us to the same answers.

My doubts

I tried to deduce the first equation, but I'm getting a sign wrong. My reasoning was the following. I have a sinusoid of frequency \$f_{sig}\$. After the first mixing stage, I get two components at \$f_{LO1} + f_{sig}\$ and \$f_{LO1} - f_{sig}\$. The first one will be filtered out, so after the second mixing stage we have \$f_{LO2} - f_{LO1} + f_{sig}\$ and \$f_{LO2} + f_{LO1} - f_{sig}\$. Again, the first one is filtered out and after the third and last mixing stage, and after the filtering too, we have that the following equality must be satisfied to generate a response on the display:
$$f_{LO3}-f_{LO2} + f_{LO1} - f_{sig}=f_{final \ IF}$$
Reordering:
$$f_{sig}=f_{LO1} -(f_{LO2}-f_{LO3}+ f_{final \ IF})$$
So in my equation, \$f_{LO3}\$ appears with a negative sign, but on the AN it doesn't. Where did I make the mistake?

The other question I have is regarding the second equation shown above: \$f_{LO2}+f_{LO3}+f_{final \ IF} = f_{first \ IF}\$. Is this a design requirement? I mean, must this equality be satisfied in order for the spectrum analyzer to work properly? Could the frequencies of each mixing stage be any combination so that the equality holds?


texts: Help me understand this shift register timing diagram

texts:
My basic understanding of using a shift register to convert serial to parallel data is this:

On every clock pulse, the state of the serial data pin is read
As data is read, it gets shifted in to the registers
When the latch pin pulses the values in the register are sent to the parallel output pins

Here is a timing diagram for the 74HC595.

SH_CP is the clock, and DS is the serial data pin. To begin with DS is low, and then it goes high and then the latch starts pulsing... Then I don't really get it. As it stands I don't understand what this diagram explains or how it is useful to me.


texts: Is it possible to switch an electrical machine several times from motor to generator and vice-versa, within one revolution of its rotor?

texts: I would like to find out how quickly and frequently a reversible electrical machine (EM) can be made to switch functions from a motor to generator and vice-versa - and what are the parameters of the EM that determine this.


texts: How to mathematically determine the frequency of a tone based on components being used

texts:
My REAL question is how to choose the right components if you want a specific frequency spit out from a 555. In my particular case I want a potentiometer to control an output frequency from 16Hz to 33000Hz (roughly the tones audible to humans), and need to know the values of all the other components in the circuit.

I was perusing Forest Mims' Engineer's Mini-Notebook V2, and came across the following adjustable frequency tone generator. The image export is a little wonky, but it's readable. If you've got the book handy, it's on page 60.

What caught my eye was the formula and given table of values. Looking at the values, they just didn't seem to make sense, and I cannot get that formula to make any sense on paper given the components in the schematic. Using the 555 calculator, I can't make the math match the table either. It appears, however, that with a 4.7ohm resistor as R2, a 0.1uF cap for C1, a 100k-470ohm pot will deliver a range from 14 to 30037Hz.  to

I'm trying to understand what I'm missing. If it's a simple "the book is waaaay wrong", fine...but I ALSO want to make sure I understand the math for the future.

My understanding of the formula is that R1 is my potentiomer, in Ohms. R2 is a non-variable resistor, also in ohms. But which cap of the two gets plugged in to the formula? do I total the caps? and what unit of measure is used in the formula? uF? pF? nF? F?

Is the info in the book bad? Are the numbers I came up with by playing with the calculator a better guesstimate of component values? Or is there something else I'm missing?