texts:
I want to create a 5v power supply design to provide power to my PIC18F4550, for that I am using 7805 so it will give the required 5v as output.
I searched online and this is the diagram I found:-

It shows that I have to connect 2 capacitors with the 7805.
I am using a 9V battery as input power source to 7805.

In the datasheet the value of Ci and Co is given 0.33uF and 0.1uF respectively, but my friend used capacitors of value 470uF and 100uF respectively and he is getting correct output without any error.

My questions:-

Can I use my friends(using Ci and Co is given 470uF and 100uF) choice of capacitor for my 5v power supply to microcontroller without any adverse effect?
If yes, then why is some other values given in datasheet.
OR
Is it really possible to use the 7805 without any capacitors at all if I am using a DC 9v battery as input?
Is there some formula for calculation which can be done to determine the values of the capacitors? If yes, where I can find it?

I know this question has been asked a lot of times, but I am having a hard time understanding the answers provided on other questions. Please help me understand this basic concept.

Thanks.


texts: STM32 USB CDC: packet loss with active PC usage

texts:
I got a strange error in the USB CDC on the STM32F2. I use HAL implementation of the driver. The size of the buffer transferred in USBD_CDC_SetTxBuffer () is 4096 bytes. On the PC side, I accept the data in the terminal.

The problem is as follows. I am trying to transfer large amounts of data on 4096 bytes. Large parcels and send them in a cycle of 4096 bytes.

In case I do not touch the PC successfully transfer data. Tested on 165 MB. However, if on PC I start using the browser, open pictures, listen to music and in every possible way load it, then I don’t receive the entire data packet. I get <165 MB. What is the reason for this problem. PC Operating System - Windows

if I send this large buffer (165 MB) by 256 bytes in cycle - all right


texts: Thevenin equivalent with mutual inductance

texts:
I was practicing for the exam I found a problem in the book as follow :

I want to find the voltage Vth so here is what I did :

When finding the Vth I didn't ignore the dependant voltage source in the second loop

But I found a solution on the internet he ignored it and got different answer due to that.

Who is right now?

Thank you all


texts: HX711 ADC Simultaneous data reading from both channels

texts:
I am trying to connect two load cells to raspberry pi 3 using HX711 24-bit ADC.
I was wondering if we can get the output from two channels simultaneously i.e A and B  .


texts: Usb input current requirements for a power bank

texts:
My project is to take solar power from a 6w/6v panel, run it through a buck circuit tuned to 5v and charge one of the LiPo power banks. I perceive a buck circuit would do better at efficiency than a power regulator, though I could be wrong.

However, the power bank does not respond at all to the input. I've troubleshot the connectors, voltage all the way through up to the usb micro b male connector. You would be right to ask how can I be sure the micro plug is not the cause? When I hook this to a cell phone, it appears to be charging. (it may not be actually charging but at least it is receiving voltage).

Reading around on Google, I've tried tying the data wires together to short it out, and test it against known-good. In reading, the outer pins are for voltage but current is tied to the device. Since the power bank is not responding, current measurements are not shown but powering the cell phone shows 2.61 on the 20 scale. That's not a reasonable validation but this is to show that the current measurement does work.

So, what am I not understanding about the usb power requirements in reference to charging this device? thx, sam


texts: What is the purpose of a capacitor in the feedback path of a unity gain buffer?

texts:
First time using this site, I'm an EE student and have been studying opamps. So far in class we have only discussed 'ideal' opamps, but I saw an opamp with this layout and was wondering if anyone could clarify what 'C1' and 'R1' are used for?

I have been trying to look for answers online, and believe I have a good understanding of what 'R1' is doing, but I have been unable to find any answers for what 'C1' is accomplishing.

This is not a assignment, just my own curiosity.


texts:
I was reading a chapter of my book (I am not putting it as reference since it is not in english) about the quantization noise problem in digital filters. Specifically, it writes about a filter that performs multiplication operations:

  "If the input, the output and the multiplicative coefficients of the
  filter are numbers that can be represented with n bits, maintaining
  this accuracy in the calculations requires greater precision since,
  typically, multiplying two numbers of n bits produces a number that
  can be represented with 2n bits. The need to round the intermediate
  results therefore produces an error called truncation noise".

To understand exactly what happens I would need a practical example. For example I don't understand if the truncation refers to integers (for example 180 becomes 200) or only for decimal numbers (for example 180.5 becomes 180).

Take for example the numbers 200 and 4, each expressed with 4 bits, that is with 16 levels (therefore 200 will have a resolution of 200/16 = 12.5, and 4 will have a resolution of 4/16 = 0.25). Multiplying them you get 800. Representing it with 4 bits you get a resolution of 800/16 = 50. Is this what is meant by truncation? What is the relationship between the accuracy of the result and that of the operands?


texts:
I am not from an engineering background, so this may be very simple and stupid but:

Voltage is the difference in electric potential between 2 points

Voltage drop describes the reduction in energy of the supply through a passive element, given by the amount of current through the resistance of the element

So for the 9V seen on the diagram, there is a difference in electric potential between the 2 terminals of the battery. the difference is 9V which means 9Joules per 6.242×10^18 electrons (unit charge) can be given to move from one terminal to the other terminal?


texts: How to put a battery and battery charger parallel in a circuit

texts: I am making a speaker that runs at 3-5.5 RMS and I need a battery to supply power to it and so I got a house phone battery pack with a diode now I need a way to charge this so when it is charging that the load will still go in the amp here is what I thought please feedback will be amazing.


texts: Why does 100G Ethernet use FEC while Infiniband doesn't?

texts:
The 100G Ethernet physical layer signalling is moving to PAM4 and using Forward Error Correction (FEC) when the lane signalling rate is greater than 25 Gigabaud (Either 4 lanes x 25 or 2 x 50).

Infiniband EDR uses a signal rate of 25 Gigabaud (Gbd) also and from what I can see HDR uses a rate of 50 Gbd.  But Infiniband doesn't use FEC.

What is the difference in signalling that allows Infiniband (IB) to have the same signal rates but doesn't use FEC to reduce error rates.  Or does IB just accept higher bit error rates? (Or alternatively is there some other correction in higher layers that allows IB to get away with higher error rates at the physical layer).


texts: Flexiforce pressure sensor with positive voltage

texts:
I recently purchased piezoresistive Flexiforce pressure sensors but I´m having some problems connecting it to an A/D converter.

On their website they show an example of an excitation circuit but it is using negative voltage which is something I don´t have access to. I need to make a circuit that does pretty much the same thing but with only positive voltage.

This is the circuit they recomend:


texts: Does it use less power to process and compress data on a chip, or to transmit it to a station?

texts:
Let's say I had a grid of force resistors laid out in a pad. Every 5 minutes I'd apply power to the pad and read the resistance of every force resister. The pad itself would be powered by a battery, and would remotely connect to a base station and upload all the data. The connection would be over low power 2.4ghz.

When it comes to uploading the data back to the base station, I had two ideas.

Simply send all the raw data to the base station and let it deal with all the calculations.
Keep the old values in memory, and before upload compare the values to the old ones and only send updated values.

My question is, would it use more power to compute what data to send first, or just to send all the data without doing any calculations on it?


texts: What reaction would take place on an electrode in a lead-acid secondary cell if it were charged and the other electrode removed?

texts:
I'm reading a book that covers the basics of electrical theory and I'm at a chapter that discusses the concept of a secondary cell. The author includes the redox reactions that take place in a primary cell when it is charging/discharging.
The secondary cell is comprised of an anode (composed of PbO2) and a cathode (composed of Pb) submerged in a solution of H2SO4. As it discharges both electrodes are plated with PbSO4 until they are fully covered, at which point the reactions that produce a charge for the battery cease and the original H2SO4 is now diluted with H2O.
My question focuses on the charging aspect of it not the discharging (because I have an easier time framing my question from this perspective) but I want to preface this aspect with a quote from earlier in the chapter discussing a primary cell:
"The zinc element or electrode, when immersed in the acid, starts to dissolve, leaving its electrons behind and the zinc goes into solution as Zn++ ions. This action stops very shortly, as the zinc plate becomes negative and ceases to throw off positive ions. The amount of zinc thus dissolved is very minute. If the negative zinc plate is connected externally by a wire to the copper plate, an electrical current will flow from the negative zinc plate through the external wire to the copper plate (positive). As the negative charge of the zinc plate is thus removed, more Zn++ ions go into the solution"
As the original secondary cell I mentioned recharges the PbSO4 plating reverts to the composition of it's respective electrode and the diluted H2SO4 reverts to it's original solution. The reactions that take place when the cell is recharging as quoted from the book:
Positive Plate: PbSO4 + 2H2O --> PbO2 + HSO4- + 3H+ + 2e
Negative Plate: PbSO4 + H+ + 2e --> Pb + HSO4-
I presume that each plate is a half reaction; the negative plate is a reduction half reaction; the positive plate is an oxidation half reaction; I believe these half reactions can be combined into the full reaction: 2PbSO4 + 2H2O --> PbO2 + Pb + 2H2SO4. Please correct me if I'm wrong about what these half reactions are or about how I combined them; I have only just recently learned about redox reactions in order to better understand this chapter.
Now for the question this has all been building up to; if the positive plate were removed during the recharge process would the half reaction that takes place on the negative plate become the half reaction: PbSO4 + 2H2O --> Pb + HSO4- + 2O= + 3H+ for a short period of time until the solution becomes negative with O= anions and ceases to throw off H+ cations (similar to what happens in the quote)?
If this is the case, then I don't know how the difference of charge between the reaction and product side is possible. The only thing I can imagine is that the O= is just a spectator and does not participate in the actual reaction.


texts:
I have the Nerf Stampede gun that i am planning on making an automated turret from and need some help running it from a wall adapter, so here is where i stand:

The gun normally requires 9V (6 batteries) but i have been running it off of 8 for 12V and that is fine so far. After measuring with a multimeter and external battery pack it seems like the peak draw for the gun is ~1.7A which seems right and easy enough to cope with. My problem begins here:

I've tracked down a few power supplies, the current one i'm trying to use is is an audiovox 12v and 2A adapter, seems regulated and likely by switching as opposed to linear regulation as it's very light and i get a good ~12V even with no load.

But for some reason when i hook it up in the place of the battery i hear the motor whine a little a few times a second and the AC adapter seems to switch on and off since the power light blinks on and off.. Seems like it doesn't have enough juice but it's easily rated for enough...

Is this common? If so is there any solution? Or tough luck find a different supply...

Thanks!


texts:
I'm previewing this chapter and I'm completely new to this. How do I solve for the answer? Can someone also please explain those $t<0 & t>=0$? I don't get time less than 0.

From Nilsson and Reidel, Electric circuits 9th edition.


texts:
I'm just getting started with the dsPIC33EPXXXGP502 processors.  When I wired it up on a breadboard, I was told to add a resistor between ~MCLR and VDD, so I did; I assumed that this was because the reset button would otherwise short VDD to ground, and that the PIC didn't care whether MCLR had a resistor or not (in other words, that it functions like any other input pin).

Upon consulting the datasheet, it seems that Microchip actually recommends this resistor be placed there:

What is the logic behind the wiring on the MCLR pin?  I understand why the capacitors are present (to help stabilize voltage during momentary current draw), but the arrangement of the resistors is confusing.

Can the resistors be removed if I don't need to be able to drive MCLR low?


texts: How can I change a DC current to a 1.7/2.4 MHz AC current for piezoelectric device

texts:
I would like to start by saying my experience in electronics is very limited and I will include pictures of everything. I am, however, trying to assemble a device which puts a current through a piezoelectric transducer to resonate at ultrasonic frequencies and atomize liquid water (hopefully).

I have found two cheap "humidifiers" on eBay with high resonance frequencies (1.7/2.4 MHz) and low current requirements. The power source I would like to use is a 3.6 V/15 A battery. My understanding is the piezo-transducer will resonate according to the frequency of its AC current.

Battery:

Question:

My question is: What is the most cost-effective method to convert my DC battery to AC with the frequency of 1.7 MHz & 2.4 MHz (these will be separate circuits)? Is there something I can use as an inverter but with variable frequencies, and would it matter if the waveform was square or sine?

Also, I think I will probably want to step-up the voltage, but I don't know how that would factor in here.

Thanks!

Edit:

I've removed images of the previous transducers as they are lacking specifications. Below are links to a transducer and spec sheet which seems to be better quality. This transducer runs on 1.65 MHz and it is different from those previously posted, so please be sure to take a glance at that spec sheet. As far as power, I have had trouble figuring out how volts/amps/watts relate to the rate the water atomizes at. I assume I would adjust the amps and keep the volts consistent to adjust this factor?

Also just to add to my question, I need to prove this is all done in compact, energy efficient, and relatively cost efficient manner because this design would need to be reproducible on a larger scale. It may be the kind of thing where I actually have to test it out to narrow down the right amp/voltage, but for now let's just assume the power is the max 30 Watts.

1.65 MHz Transducer: Product Page  Spec Sheet


texts:
I need some help regarding the transformer in the battery charger unit.
The lightning struck my house, and sadly the mobile home was connected to 230V outlet. Among other things that needed to be repaired or replaced in the house I have noticed that my batteries in the mobile home are not chraging.

After quick inspection I have found a fuse than was blown out. I have replaced the fuse but as soon as I connect charger to the 230V outlet the fuse blows out. I guess there is a short circuit in the transformer ? I did quite a lot of project with microcontrolers and stuf like that, but I only know basic principles how transformers work.

The unit is EBL 264-3 it has 12V logic. (Picture is for the 264-7 model but the specifications are practicly the same)

So, I guess the transformer is 230V - 12V, why are there 3 output wires ?

Here are a couple of pictures, as you were interested where the output wires go.

Marked wires :

Two wires (D,E) are going directly to the circuit on the right (I presume D is ground and E is +12). On the board is connected to the bridge rectifier (B40C800). By the looks of it, this is the board that switches things on and off from the control panel (couple of relays and so on). This is probably the power for the realy switching. (B40C800 - output current 0.8A, I guess ? )

The recomended input voltage for B40C800 is 40V. is there anyway I could figure it out how much was the transformers output ?

Picture of the circuit board above the transformer :

I have removed the transformer from the box :

I have found the scheme of the battery charger (the resolution is low, but this is directly from the manufacturer's site)


texts: The Art of Electronics - differences between book versions?

texts:
http://www.barnesandnoble.com/w/art-of-electronics-paul-horowitz/1100491782?ean=9780521370950

There appears to be a couple of versions of the 2nd edition of this book. I noticed US and International editions and a Hardcover or Paperback versions.

Are there any contents differences between the versions?

[editor's note: The third edition of this title is now available]


texts: LED series-parallel and parallel-series combination circuit

texts:
I'm designing some LED strips to use to grow plants along a long wall. There will be hundreds of LEDs run by a constant-current high quality LED driver (Meanwell brand or similar). All the commercial strips I've seen (Bridgelux, Samsung, etc) divide the LEDs in sections, wire the LEDs inside each section in series, and then all sections are wired in parallel, like the first example in the image below.

Could anyone tell me why that's better than wiring the LEDs in each section in parallel, and have the sections wired in series, like the second example in the image?

One problem I see with the first approach is that if there's a section where airflow is limited it will create a hotspot where all the LEDs in that section will drop their forward voltage and start hogging more current leading to thermal runaway.

The second approach seems like it would solve that problem since the LEDs heating up are all competing for the same current so it should stay more evenly divided.

Is my thinking correct? Am I missing some other major pitfall in the second example?


texts: Modem power usage versus signal strength

texts: Is it true that a modem (such as a 3G dongle) will use more power when signal strength is weak that when signal strength is strong? Also, can someone link me to a resource that discusses this? What is the variation in power usage between weak and strong signal for an average modem?


texts: Response of an LTI system by convolution

texts: So here in the picture \$e^{jwt}\$ is the input to the system and \$h(t)\$ is the impulse response. So, by convolution integral shouldn't the response be \$h(t-T)e^{jwT} dT\$? But here it is \$h(T)e^{jw(t-T)}dT\$. What am I missing here?


texts: I accidentally shorted three 18650, 3700 mAh batteries connected in series for about 2 seconds. I measured each cell individually with a voltmeter and they read very close to its original rated voltage of 3.7 V. However, when I tried to use the batteries to drive a DC motor, it doesn't work. How do I tell if the 18650 batteries are dead? If the voltage between each cell is close to 3.7, can I say that it is still well and alive?


texts:
I am attempting to implement this tail light design first by using a state diagram. The car has 4 tail lights on each side, making a total of 8. They behave accordingly when the following inputs are implemented.

Below is the state diagram I have attempted to make for it so far. Obviously the goal is to have a minimal cost design. I have the state diagram so that when the inputs 111 or 000 are implemented, it stays within the "on" state. I am wondering if what I have done so far is the correct way to be going about it.


texts:
I have been using a 555 timer to modulate an audio signal and it works as expected, but I wonder how.

If I am right, when the control voltage pin is positive, the "trigger points" get to CV and CV/2, but what happens when \$ CV \leq 0\$, as it does with an audio signal ?

Are potentials below zero simply clipped because of the comparators ?


texts: Swapping power supply - need clarification on grounding (AG & DG)

texts:
The internal power supply on my Yamaha keyboard was broken while moving house (PCB is nearly snapped in half) and because it's 30+ years old it's not easy finding a NOS part replacement. I've found the schematic for it (attached), but I'm confused on one part.

The output pins are labeled (and what believe they are):

+12  (+12V DC)
AG  (No idea - assuming ground???)
-12  (-12V DC)
+5  (+5V DC)
DC  (DC Ground)

Can someone please clarify the function of the AG for me? I can see it's connected via rectifier diodes to the +12V and -12V rail, but since I only have a basic understanding of electronics, I don't know what it's actually for.

I'm considering swapping in a pico ATX PSU since they're easily obtained and have the necessary +12, -12, +5 rails, but I've got no idea how (or if it's even possible) to wire in this AG. So secondly I'd like someone to clarify if this idea would/wouldn't work.


texts: I'm somehow able to light an LED by touching it

texts:
I have plugged one end of an LED into the ground port of an Arduino.

By touching the other end of the LED with my finger, the LED lights up dimly.

I can keep the LED lit as long as I am touching the LED, but it goes off if I also touch the USB port housing (ground) on the Arduino with my other hand. It comes back on when I let go of the USB port housing.

This implies that my body is somehow being kept at a positive voltage with respect to the Arduino ground and that the positive voltage cannot be discharged by touching Arduino's ground. But I don't know what is supplying this energy. I'm just sitting on my couch with my feet on the floor. The floor is made of wood and lifting my feet of the ground doesn't change the effect.

Any clues what is happening here?


texts: Audio from Arduino Due's analog outputs using LM386

texts:
Due's DACs provide 0-3.3v (actually less) and are rated at 3mA max. As far as I know, common speaker/headphone impedances range from 8Ω to a few hundreds, so driving these from the DACs will destroy it at best. I guess I could stick a series resistor, but it would need to have a huge resistance and would greatly reduce the output volume.

According to Arduino's SimpleAudioExample I can drive a speaker from Arduino's DAC using an LM386 amplifier. Is it because \$\rm{R_{in}}\$ (datasheet, page 2) is the LM386 input resistance, so \$I = \frac{V}{R_{\rm{in}}} = \frac{3.3\rm{v}}{50\rm{k\Omega}} = 66\rm{\mu A}\$, which is a lot less than the max 3mA the DACs can handle?

Arduino's SimpleAudioExample circuit looks like LM386's "Minimum Parts" example (datasheet, page 5) with a 10μF capacitor between \$V_{in}\$ and the pot:

Is this extra cap AC coupling the DAC with the LM386 input to remove the implied \$\frac{+3.3\rm{v}}{2}\$ DC bias at the input?

I hope I got all that right.

Even at a low 20x gain setting (pins 1-8 open) \$20*\frac{\pm3.3}{2}\ \rm{volts}\$ seems like a lot! Also, max input voltage is listed at \$\pm0.4\rm{v}\$ (datasheet, page 2). Is something (I guess the pot) reducing the input voltage and preventing huge Vout? Could it accidentally be set to deliver the whole 3.3v input and break the speakers?

What am I missing?


texts: How to calculate the voltage of the capacitor in this circuit?

texts:
i have a problem with this circuit.
I am trying to calculate all the voltages and currents but i think i did something wrong.
I think the voltages \$U_L\$ and \$U_C\$ are wrong because they seem a bit high and i am also not sure if the formulas used are the right ones in this case.

$$ Z = j\omega L + \dfrac{1}{\dfrac{1}{R} + j\omega C} =11.57 e^{j62.16°}$$
$$ I = 19.02 e^{-j112.16°}A$$
corrected:
$$ U_L = I\omega L = 646.66e^{-j22.16°}V$$
$$ U_C = U_0 - U_L = 463.6 e^{-j189.36°}V$$


texts: Is there a metric version of this nomogram?

texts:
I found this nomogram, which also appeared in an answer here I think.

(larger version here)

Is there a metric version of this?


texts: High temperature reading of mechanically-separated body

texts:
I have a device with 2 mechanical parts. One side is stationary and can be connected to an electronic circuit with power. The second side is an enclosure that can have high ambient temperature (100-120°C). I cannot bring a wire from one side to the other, but I would like to read the internal temperature of the second side. The mechanical parts have facing plates of ~50mmx50mm with a distance of 10mm. Sensor must be able to read from -40°C to 220°C. One of the facing plates will rotate, as it is connected to a motor.

Reliability and low cost are important factors.
What type of sensing could be done?

I thought of magnetic coupling with energy harvesting, just like RFID. As the environment will be very noisy and reliability is important, I'd like something with a modulation robust to amplitude variation (FM or better). I thought maybe an oscillator connected with a RTD that would change the impedance of a transformer with a variable frequency could do the job, but I've never done this type of circuit.

Can somebody point me out to a temperature sensing technique that could fit? Or some literature that would help me design such circuit.


texts: Having trouble designing a JFET input stage in a Multistage Transistor Amp

texts:
I've been given the task to design a multistage transistor amp.
Specs given are:

Overall voltage gain: 80 (min) to 100 (max)
Input resistance no less than 1Mohm
Voltage supplies: +-10V
Achieve max output voltage swing when Load Resistance is 2kohm
Capacitive coupling with low freq cut off of no lower than 30Hz but no greater than 60Hz
Amp must also include negative feedback from final stage to an earlier stage (preference: voltage-voltage/voltage-series)

[PS. I am aware I don't need the emitter cap in stage 2 of the design above; I believe I must split the emitter resistor into two separate resistors for the negative feedback I'm hoping to implement.]
I'm trying to design the first stage using JFET, but haven't been able to design it very well. From the data sheet, I see the typical values for IDSS and VGSoff are 10mA and -8V (Although in the lab, actual VGSoff seemed to be = -4V). Keeping this in mind, I calculated values of resistors:
Assuming RD = 4.5k and RL=10k, I calculated RS = 350ohm. This didnt seem to work in simulation in PSpice or when I built it in the lab. Is there a way to calculate RD/RL instead of assuming values?
However, I have a question regarding biasing in my case. I went with R1=R2=2Meg (for low freq response). Still didn't work.
Which, from Self-Bias and Voltage divider at gate, seems like the best way to go in my design?
Even if I get values, I could calculate backwards and see how the theory works out.

Help much appreciated!
Thanks


texts:
Hello I recently bought this item at ebay and I am not sure how I should wire this.

I will power it with a 9 volt battery and the relay will power a pump, this is how they at ebay show how I should wire it. But I don't understand how I will connect my pump's positive and negative wires to the circuit or how I will connect my 9 volt battery to the circuit?

Since the (X) symbol on the chart is only powered by a negative wire from what i can understand. DC-

and from my basic knowledge the (x) symbol is a lamp? (the source that needs power)

I also don't understand what the two power terminal at the top will do that has nothing connected to it?

What this circuit will do is that it will delay my push button action so the power will remain on to the pump for 5 seconds then turn of instead of the push button will only power while pressed.


texts: Why does signal quality change in different indoor environments?

texts:
I noticed (I have some radios I was testing stuff with) that signal quality (not necessarily strength) seems to change from room to room.

The frequency of my radio is 2.4GHz, bit rate is 100kHz.

It can't be delay spread because the rooms aren't large enough for that to really play a role. No doppler, because the nodes aren't moving....

For the record, I have a large room (probably about 5 x 10m, 3m high ceilings) in which the signal seems to be of better quality than in a small hallway.

Any thoughts?

Edit: Intrasymbol interference? The carrier is 2.4GHz, so the period is quite small...


texts: Difficulties with Class B Amplifier Biasing

texts:
Here I am referring to class B output power amplifier.

This circuit should be easy to build and understand but I'm having problems with biasing  since I don't really know how to bias the bases of Q1 and Q2, so that Q1 would conduct only positive polarity signals and Q2 would conduct only negative polarity signals.
It seems that I only managed to properly bias class A amplifier, but not class B.

How would I had to bias the upper circuit to achieve class B operation of an amplifier?


texts: How to prevent voltage variation in a fast-switching circuit with parallel connection?

texts:
I have designed a circuit in which 2 LEDs are connected in parallel and controlled by MOSFET gates (n channel). These MOSFET gates are driven by the output pins of an FGPA to switch them btw ON/OFF at high frequencies around 1KHz.

As shown in the above figure, each LED is controlled by two MOSFET gates. I notice that when both MOSFET gates are switched at a close but different frequencies, say 1013 and 1023 Hz, the luminance of the LED slightly vary (Note that human eye can only perceive luminance change less than 60 Hz). However, if only one LED is connected, there is no human-observable luminance variation.

To find the problem, I connected an oscilloscope to the LED and notice there is a voltage variation btw the Drain and GND of the second MOSFET gate, the frequency of which is around 10Hz and is shown as follows:

What is the reason for such variation? Is it connected to the voltage drop of breadboard? How can I solve this problem?


texts:
I am struggling to see how the "inverted buck-boost" converter works the same as a "4-switch buck-boost" converter. In my mind, a 4-switch buck-boost is simply connecting a buck and boost together, but in the inverted buck-boost, I can't visualize that. Can anyone show how the buck and boost operations actually work in the inverted buck-boost (explanations on how it converts 20v to 5v & 5v to 20v)? I've seen a lot of descriptions/videos about how it stores/releases energy from the inductor, but never how the buck and boost functionalities come in to play (explanations on how it converts 20v to 5v & 5v to 20v).

Note: this post was mentioned by someone before @ Boost operation in inverting Buck-Boost converter, but wasn't answered to my better understanding

UPDATE: I'm asking the question in reference to the 1st picture shown below.


texts: How large is "one pixel" for S5 AMOLED display?

texts:
Referring to Samsung Galaxy S5 OLED Pixel structure in oled-display.net, in particular this image illustrates the S5 AMOLED pixels:

To my understanding, the yellow rectangle should represent "one pixel" as it is the smallest repeating pattern.

However, doing a few maths:

118 micrometers = 0.00464566929 inches
1/0.00464566929 = 215.25423735 pixel-per-inch (ppi)

Which is very different from the announced figure: 432 ppi.

However, surprisingly:

215.25423735 x2 = 430.5084747 ~ 432 ppi

In another words, 432 ppi is concluded by seeing 1/4 of the yellow rectangle (59µm x 59µm) as "one-pixel", isn't it?

But why? In the 59µm x 59µm square, it contains only either Blue or Red. In simple words, repeating the 59µm x 59µm square cannot produce this pattern, isn't it?


texts: Find location of wire break in low voltage wire buried in garden grass

texts:
I have a Flymo 1200R robotic grass lawn mower.
The auto mower detects the boundary position of the edge of the lawn through a low voltage electrical wire that is buried close to the lawn edge which emits some sort of electrical field that the auto mower detects.
This boundary wire runs around the edge of the lawn to contain the mower within the desired grass cutting area.
Boundary wire is about 210 meters long.
Wire breaks in this boundary wire stop the system working.
One way the wire can break is if a rabbit, for example, digs a hole over the boundary wire and then chews through the wire. The mower will then stop working.
Finding the location of a break can be a long, long, task involving lots of digging in different places where the wire is buried.
This boundary wire emits some sort of electrical field or radio signal while the auto mower is mowing. I am unable to ascertain what frequency is emitted after a fairly extensive google search and youtube search.
I have tried moving round the perimiter of the boundary wire, with an am radio, set to a few different frequencies, while one end of the boundary wire is disconnected from the mower docking station, and the other is still connected and transmitting, but this did not pick up any signal,  from the wire at any location. This method seems to work for some people as a youtube search can show.
I can disconnect both ends of this boundary wire from the mower docking station and pulse my own signal if need be to aid detection.
Can anyone recommend a low cost signal generator and detector kit, or other method to easily detect the location of the break in the wire.


texts: I am curious about how to wire DRAM to an SoC. What is required for optimal usage other than the net itself? I have seen conflicting information on if you should or should not use a termination resistor (here). There hasn't been much information I could find on connecting DRAM, which makes me think that a direct connection is what most board designers use, as otherwise there would be information on what would be needed to reduce EMI. I'm planning on using Micron MT40A1G8SA-062E for DDR4 RAM and a MIMX8MM6DVTLZAA SoC by NXP.


texts: Using an Adafruit Trinket 3.3v with a TIP120?

texts:
I'm new, so please go easy!

I'm trying to use a TIP120 transistor as a switch in conjunction with an Adafruit Trinket Pro 3.3v. According to the documentation for the Trinket, the GPIO pins should be able to source 20mA of current, which, if I'm understanding the transistor documentation correctly, should be enough to bias the TIP120.

Fabulous, except that I'm only ever measuring 10mA from the GPIO pin when I have the circuit hooked up.

The TIP120 is being used to switch on power from a 3.7V 18650 battery, and I do actually get some bias from the 10mA - I read about 2v - but I need the full 3.7v.

Could someone please let me know if it sounds like I'm misunderstanding anything here? Why can't I get the Trinket to source 20mA to fully switch the TIP120?

Thanks for your time and help!


texts: RFID 13.56, can you include a tab in the data string?

texts:
I have tried to find the answer by googling but I can't find anything about it.

On a normal barcode you can include a tab \t in the datastring making it possible to write username and password in two separate fields.

Is that also possible on RFID 13.56? Can you write username\tpassword on the tag and have that as your method to log in to software on a computer?


texts:
Lest assume we have the setup presented in the image.

What would be the potential difference (not voltage drop) between points A and B? Why?

What effect will the pn junction barrier potential have on the potential difference between A and B?

According to this book (page 79) the barrier potential can't be measured with a voltmeter (I will get 0V reading) but it exists :).

So I assumed that potential difference between A and B is equal with the barrier potential of the pn junction even if I can't measure it. Is this correct?
So B will be at a lower potential than point A?

Some people said that there is no potential difference between points A and B,  but on the other hand if I measure with a voltmeter the potential at point A relative to the "-" of the battery I will get a 5V reading, when I measure the potential at point B relative to the "-" of the battery I will get a reading of 4.8V. So I am a little confused :).
I am a beginner and I am trying to correctly understand what is going on.


texts: Can anyone identify if this is a standard connector or not?

texts:
Or let me know if there's a decision tree process to find out myself. It's from the LVDS connector on an apple motherboard. Foxconn part number m38&39, 01-01003047-00-b.

I'm wondering if the mounting bracket is a standard shape or model. It has a total of 30 pins, with 15 on each side facing out.

The mobo mount

The actual part.


texts: Does choosing rounding mode have to be costly?

texts:
In many floating-point implementations, changing the rounding mode is costly in that it requires a pipeline flush.

Is this because there is something particularly complicated about rounding modes, or is it because global flags interact badly with pipelines? For example, if the rounding mode were supplied as a couple of bits in the instruction, instead of as global flags, would it still be costly?


texts:
Can anyone clarify if I am not understanding this comparator circuit correctly. The author says that if the temperature drops across the ntc thermister, resistance will go up and cause output to go low. Since it is the input signal connected to the inverting pin, would it not increase the voltage drop across it therefore dropping available voltage between r1 and r2. Non inverting would be greater than inverting and therefore output would be high. If I am wrong, please clarify. Thanks again

http://www.electronicshub.org/thermistor-based-hvac-thermostat/#comment-235699


texts:
Sorry if there is a straight forward answer but my partner has converted a trailer into a drinks unit. She has a fridge a freezer and a coffee machine. Also about 5double sockets and lighting.
The question we are stumped on is when applying for venues they asked which 32amp we need single or three? and I haven't the foggiest .
If anyone could help would be so grateful.

Many thanks

James


texts:
I have some experience working with stm32 but I only ever used them on dev boards.

I recently tried to solder stm32 and stm8 on a simple break-out board and program them with my st-linkv2 clone.

On first power up, the mcu makes some little noises like burning after a few seconds, and 2 minutes later its drawing 100mA and smoking.

I think there is some important details that I'm missing.
What could go wrong in a simple setup like this? (only vdd,vss, decoupling cap and st-link)

I tried over 20 times with both stm8 and stm32.

I got the decoupling cap as close as possible and supplied them with 3.3v.

A few times I was able to program and verify the flash but it showed some weird behavior * and again went up in smokes a few minutes later.

I tried drag soldering, regular soldering with smd tip and temperature as low as 260C and cooldown time after each pad. I also tried hot air gun on 270C and I'm close to sure the problem is not soldering.

I also tried with NRST pull-up and BOOT0 pull-down.

*weird behavior: "random" like timing on a simple led blinker or a pwm signal that only goes down to around 2.8v instead of 0v. overall its 'kinda' working but only for 1min.

** the problem is not st-link. its flashing the dev-board just fine

EDIT 1:
Here's the schematic (for stm32)(Connections to ST-Link marked with labels):

there is nothing beneath. just another (unpopulated) footprint connected to pins.

EDIT 2: continuity test: no shorts, all pins contacts are OK

EDIT 3: connected VDDA and VDD and added another 4.7uF on VDD. still fried up.
VDD measured directly on device: 3.36v

EDIT 4: current draw behavior: in all cases when the chip is fried, it draws around 20-40mA and sometimes suddenly goes up to 100-240mA for some seconds and then zeroes out(less than 10mA). and stays at zero for some time before start again.

UPDATE: i soldered another STM8S003F3P6,1uF on VCAP and 2x100nF and 10uF on VDD. and used a battery as source and made a little capacitance multiplier and emitter follower to make the 3.3v with lots of ceramic and low-ESR caps, and a current limit set on 15mA.
the voltage had less than 30mV noise over 50MHz. then i connected the MCU (freshly soldered).
current draw was less than 4mA and voltage was stable. i left it be. after a minute or two, it suddenly started to go over 15mA limit and trig the PDR. and now it starts to do that immediately (even with the NRST asserted). seems this one is gone too...


texts: Does any current flow through C-E of NPN BJT when the base is floating?

texts:
UPDATE

Have included an image. As you can see, LED is ON when base is floating. This is a 2N222A transistor.

Playing with an NPN bipolar transistor. The Collector is connected to the positive terminal of a 9V battery through a 1k Ohm resistor, and the Emitter is connected to the ground through an LED. The Base is not connected to anything.

The LED seems to be dim in the above case. When I connect the Base to the positive terminal, the LED is much brighter. That makes sense as current through the base Base amplifies the current.

My questions is: should any current flow through the emitter if the base is not connected to anything? I.e. Shouldn't the LED be completely off?

I have a similar question for NPN Unijunction transistors (understand that nomenclature changes from CBE to AGC)?


texts: Why is the signal rate separated into three case?

texts:
The definition of signal rate is number of signal elements (timewise shortest unit) sent in 1s.
The book says that the signal rate of all 1s or all 0s may be different from a data pattern of alternating 0s and 1s. (And there can be three cases : best, worst and average)
The strange thing is, it means that the signal rate changes in real time.
Data rate and signal rate are interconnected by a formula : S = N/r
How does the signal rate change dynamically even if N(data rate) and  r(number of data elements per one signal element) are static?

[EDIT]

Data Communications and networking (of Forouzan)


texts: Real-time vs Non-Real time ADC processing

texts: What are the applications or Pros/Cons of using real-time vs non-real time when reading an ADC? For example, let's say you're reading a sine wave from a CT. As far as I know, if you’re processing in non-real time, and the signal data is acquired in blocks (fixed-length sequences) of block length N, some math get kind of straightforward compared to continuous data acquisition. In what applications you would choose one or another?


texts: Is it possible to make illegal clones of an Intel Core i7?

texts: The reason I'm asking is that on http://alibaba.com you can find prices for the Core i7 as low as $20, minimum quantity 1. This looks like impossibly low for a genuine Intel, but then I also can't believe you can clone this kind of CPU. What's the matter here, and what kind of problems can I expect with these cheap CPUs?


texts:
I'm currently trying to use 74HC163 in a project, and it appears I have it wired up correctly, but it counts in a very strange sequence.  I wrote down the sequence as follows:

1 10 11 101 110 111 1001 1010 1011 1101 1110 1111

Translated into decimal:

1 2 3 5 6 7 9 10 11 13 14 15

As you can see, it skips several numbers including 0.  Why is this?

I have it wired as follows:

NOT CLR = 1
CLK = 10HZ clock from square wave generator
A = 0, B = 0, C = 0, D = 0
ENP = 1
GND = 0
VCC = 1
RCO = no connection
QA = LED, QB = LED, QC = LED, QD = LED
ENT = 1
NOT LOAD = 1

0 indicating unpowered, 1 indicating powered


texts: Dual-supply to Single-supply op-amp conversion

texts:
I'm building an op-amp circuit that takes my electric guitar signal shifts the voltage from -1.5V to 1.5V to a 0-3V. I have this circuit that works perfectly with a dual supply op amp in multisim, but when I use the single supply op-amp the output gets cut off at about 1.7V, halfway lower than I want it. I tried this with MCP2006 I/P(single supply) and the TL972 IP(dual supply). I used identical circuits (besides the power supplies of course) on both in multisim. My circuit will be battery powered so making a negative supply shouldn't be too difficult I'd just rather use one battery. Also, I'm just kinda curious as to why it doesn't work that way.

Here are the different oscilloscope readings MCP2006 I/P and TL972 IP, respectively.


texts:
I know this might be a bit too specific of a question, but I have trouble calculating \$V_o/V_i\$ in the given scheme.

I was given a BJT-transistor and had to find an equivalent AC-scheme (i.e. eliminating conductors and DC sources).

Now, I am asked to calculate \$V_o/V_i\$ as seen in the image.

Can anyone give some tricks where to start etc. and/or perhaps give a solution? There are no numerical values, so the solution should be in 'symbolic' form. The part which confuses me is the 'current controlled current source' and the resistor \$R_B\$ (more precise, how to bring it in to account).


texts:
I am attempting to read the voltage on a backup battery on an Arduino.  To that end, I used the circuit Olin Lathrop offered in answer to this question.  I am powering the Arduino with 5V, and the battery is 3 AA cells, so 4.6V or less.
Using the battery checker circuit Olin offered, see link above,
 I can reliably read the voltage on the main power supply (~5V) but when I connect the battery instead, I am only reading 0.06V when the Q1 is turned on.  I believe this is because the base voltage on Q2 is too close to Q2's collector voltage.  I only see turning Q2 on as more difficult as the batteries discharge.  I think the way to fix this is to modify the Q1 part of the circuit so that the base voltage on Q2 is less when this circuit is "on".
Any input would be appreciated.


texts: How to wire up GSM Modem(DCE) With MAX485

texts: I am trying yo figure out how to directly connect a GSM modem (say SIM800) with a MAX485 . The purpose of this is to make an RS485 GSM Modem. I am struggling how to wire it up, do i wire the CTS of the DCE(Modem) to the RE/DE pin together ?


texts: Altium Design Rule - How to apply to one named component?

texts:
How can I build an Altium Designer rule that applies to only one component or reference designatorrefdes?

I tried selecting my component, S1, from the Query Helper, but that just puts the string 'S1' into the query.  What else belongs there?


texts: Which software tools from LatticeSemiconductor do I need to develop design with iCE40 LP FPGA?

texts:
There are a lot of programs that can be found here:
https://www.latticesemi.com/en/Products/DesignSoftwareAndIP
Which of these do I need for creating a design with iCE40 LP FPGA?
The reason for my confusion is that we merely need Quartus Prime for Intel and Libero SoC for Microsemi. However, when it comes to Lattice Semiconductor, there is a lot of choice.


texts: Bypass IC output to give an LED a voltage boost

texts:
I'm attempting to modify a circuit in an existing device, the relevant part of which looks like this:

The IC controls the LED brightness, as well as having connections to other things. I have replaced the LED with a different one. My problem is the new (blue) LED requires more voltage than the stock (red) one and barely glimmers with the existing supply.

I don't have the resources, skills, or space to do anything elaborate. My idea is to add an extra line, with a resistor of a few hundred ohms, between the LED and the ground, to bypass the IC and give the LED a boost. The LED will still be mainly controlled by the IC, but the extra line will help get it off the ground, so to speak:

Now my problem is, I'm not really an electrician and I have no idea if this will affect the chip. Will it notice? Will it care? Will it melt?


texts: High side current sensing resistor selection assistance

texts:
I'm designing a circuit that will allow me to do transistor testing (similar to a curve tracer). One part of the circuit is a power supply that will apply different voltages to the collector / emitter.

** I have posted a question regarding the same circuit, however this is a completely different question. **

I need to monitor the current following into the transistor so I'm using high side sensing because:

I want to detect possible shorts at the power supply (I>250mA)
I have a few AD8418 current sense amplifiers that fit the job.

The AD8418 has a gain of 20 V/V so I can get the range I'm interested in using a stable 1 Ohm resistor.
Some online reading and searching brought to my attention that "high" values such as 1 Ohm are rarely used for current sensing. However, using a much lower values resistor will result in a much lower output voltage which will have to go additional amplification before being sampled by an ADC. I'm afraid that another stage will add noise, offset error and gain error.

Should I go ahead and use a "stable" 1 Ohm resistor or try another, more complex, solution?


texts:
I'm trying to use an NE555 IC in monostable mode to send a pulse that should mimic a button press.
This pulse should be delayed for some time (after the appliance powers up) and then stop (similar to how I'd do it, I plug in the appliance, I press the button for a short time and release).
The circuit looks like this:

According to simulation the voltages should look like this:

Hooking up an LED an playing with the RC values in order to change the timing to something more noticeable, this seems to work.
However when I plugin this into the appliance whose physical button I'm trying to mimic, things either work or they don't. They mostly don't, the button press isn't simulated, I only gotten it to work once or twice and I'm not sure how I did it.
The button I'm trying to "mimic" is the SW10 switch in this diagram:

So something relatively simple, a voltage divider to an input pin of an micro controller.
How can I figure out what is going wrong when using this circuit?
Doesn't the simulation fit the real world or are there some unknowns I haven't considered when fitting the circuit to the physical button?
I have succesfuly done this using an Arduino by setting one of its pins to LOW for 500ms, then to high impedance (INPUT) and it works 100% of the time.
I'm guessing the capacitors in my circuit remain charged or other capacitors influence the circuit (although they should influence the arduino as well - and I cannot see any capacitors on the circuitboard)?
I should note that I have no control over the R80, R5, SW10 or the Akai MCU components. I can only find their leads on the existing board and "plug" my circuit (the transistor TR1) there.


texts:
I have a design with chained modules. Each of them is a pipelined design, so the output in each of them take more than 1 clock cycle. To perform the test bench, I have created so many registered signals as stages in the pipelined designs to delay my gold test and compare it with the real output. An example:
// If module 1 has 4 stages:
reg [31:0] G1, G2, G3, G4;
always @(posedge CLK) begin
    G2 <= G1;
    G3 <= G2;
    // This is the the gold test bench synchronyzed
    // with the output from the pipelined module
    G4 <= G3;
end

In this way, I can compare the output of my module with the gold test. Other way is using time delays:
always
    #50 GOLD = output_from_module;

What is the best way to check an output that is delayed more than one clock cycle?


texts: Is it possible to draw circuits through code?

texts:
Is there a better way not by writing netlist files. something like:

Define Battery1 As a Battery
Define Resistor1 As a Resistor

Connect Battery1 First Terminal to Resistor1 Second Terminal
Connect Resistor1 First Terminal to Battery1 Second Terminal

EDIT:

I find the answers pretty helpful. It will be great if there is a way to simulate the circuit produced by the code.


texts:
My goal is to get a 3.3V MCU (probably a ESP32) to drive this circuit. It is driven with a square wave from 15 to 40 Hz where the pulse width itself of 2.5 to 13 msec. When searching for answers, the solutions would assume a 3.3V to 5V level shifting and have the load above the transistors that get turned on.

The originally supplied PCB with microcontroller for this function has perished; possibly related to the 12V input being 19.9 VDC? Reviewing the circuits on the original MCU PCB wasn't straightforward as I believe it had been employed across various uses and functioned by coincidence more than by design.

Diagram of what I'm trying to do:

Pics of the PCB are on imgur "post" or gallery and here is the TIP142 Datasheet. Please note a couple conditions: The MCU voltage is supplied from the PCB, so will have 20VDC, which I will use a buck converter to 3.3V for the ESP32. The load is on the emitters and there is shared ground between the MCU and the PCB.

Testing Steps Performed

+20 V to input turns on the driver circuit, Input open or on ground and circuit is off.
Voltage divider set up with variable resistors; discovered base-ground resistor needed to be maxed; so it stayed fixed at 437Ω.
Vary the base voltage up and I noticed between 5 and 6 V, the circuit turns on.
Data point: With the divider connected and the circuit on and 6.3V measured on the input, the Top resistor was 789Ω. Calculates to 15 mA of current.
The lowest voltage I could observe the circuit turning on was 5.0 V.
Without changing the resistances, I disconnected the voltage divider from the input and measured 5.66 VDC between the resistors.


texts:
Recently I designed a board to control the lights in my home remotely via HomeAssistant (ESPHome using a WeMos D1 Mini). Due to the lack of pins, I am using a PCF8574 to actuate the relays. The main issue I am facing is that when switching off fluorescent lights (be in PL-C 2 pin or tubular), the entire circuit (all the relays on the board) glitches to "ON".
Here is a circuit diagram of my board:

As requested the .pdf files for the board and schematic.
A video of the problem I am facing can be found here. Between 0:00-0:27 of the video, I cycle through all LED lights in the room (using the remote app) and they work fine. at 0:27, I turn on the problematic fluorescent light. At 0:31, I attempt to turn it off but it doesn't turn off and causes all the lights in the room to suddenly turn on. Checking the logs shows that the ESP8266 did not reset nor did any of the PCF8574 pins go to "HIGH" during the period of the malfunction.
Hence I likely suspect that this issue is caused either by the PCF8754 glitching out or perhaps caused by some form of interference caused by the circuit design.
Interestingly, I had tried the board out before installing it on similar PL-C 2 pin bulbs which can be found here. As such, it's really perplexing as to why the circuit would have failed when being installed.
Currently, I have the following hypotheses (in order of likelihood:

The PCF8574 glitches out when fluorescent lights are switched off on the relay. The cause behind this is unknown as I lack a proper oscilloscope and the know-how to troubleshoot the PCF8574.
Solution: Redesign the board and switch the relay pins to the ESP8266 and leave the PCF8574 to do the sensing on the button and the outputs on the light

Magnetic interference caused by the tangled nature of the wires could be causing the PCF8574 to glitch out. For reference, here is an image of the board being installed in the switch box:

Solution: Better wire management (which has been done, greatly reducing the amount of wire clutter); possibly isolating the wires from the circuit board using an aluminium foil?

Lack of isolation between load circuit and signal circuit.
Solution: Redesign the board with optocouplers to switch the relay with a separate power supply for the relays and the IC components.

I have written about this in greater detail in my blog here and have linked the relevant eagle files  here if it is helpful.
As I am still a beginner when it comes to circuit design, I would be greatly appreciative of anyone who could point me in the right direction! Thanks everyone in advance!


texts: How to calculate estimated current taken by DS3231 when it is wired for alarm

texts:
I am developing a system which is considered to be work for long under battery supply. I have a RTC DS3231 configured in alarm mode and it is also used to wakeup the micro controller. The circuit connection is given below which is taken from the datasheet.

I am going to use this circuit in project. But the problem  is that i wanna know more about the current consumption of this circuit. In datasheet, active power supply current is given by 200uA ( for vcc 3.63V).
I am using a 3.3V vcc. Can anyone help me to find the total current consumption by the above circuit( considering I2c pullup resistors and INT,32Khz pullup resistors).


texts: Can someone help me understand this transistor circuit?

texts:
I believe the purpose of this circuit is to perform SQ decoding.
It is supposed to shift the phase 90 from 100Hz to 10Khz.
I'm interested in listening to the quad version of the Pink Floyd Animals LP, and, I came across a bigger circuit, on a 70's electronics magazine, of which this network is a part of. So, my goal is to make this circuit, but I would also like to understand the phase shifting network.

SO, this is what the circuit should be, I'm interested in listening to the quad version of the Pink Floyd Animals LP, and, I came across a bigger, on a 70's electronics magzine, circuit of which this network is a part of. So, my goal is to make this circuit, but I would also like to understanding the phase shifting network.


texts: Does Quartus support UVM in files with .sv extension?

texts:
I want to learn UVM later (i am starting with verilog first, systemverilog is next) but i have this doubt in my head,  i have seem examples in the web but they use Modelsim, so my doubt is, if i make a testbench in Quartus with extension .sv, using UVM classes, will it run the simulation? Is it even possible to use the UVM classes in quartus?
I ask this because i know that quartus does not support systemverilog completely like unions, or dynamic arrays, etc. (https://www.intel.com/content/www/us/en/programmable/quartushelp/13.0/mergedProjects/hdl/vlog/vlog_list_sys_vlog.htm).
If it is actually possible to implement UVM in quartus, which i think it does because quartus run modelsim as a simulator, can anyone provide me some link/book/etc about it? i mean using uvm with quartus.


texts: 4 (5) band 5% resistor with superfluous black end?

texts:
I need to replace a resistor (brown black black gold black - if I am reading it correctly) - the kind I need is shown in the images below, but I can't seem to find an exact match of the colour code. Is the black (5th) line at the end of the code superfluous - so this is in fact just a 4 band code (making it a 10 Ohm 5% resistor)? From my research it appears that a resistor code would almost never start with black. However a 5 colour resistor of similar pattern doesn't appear to often end with black either...

Detail: I am repairing a toaster where one side (2) of the 4 toasting slots have stopped working. Each side operates independently so I am using the working half as a guide to repair the blown side.

Here is the blown resistor from the damaged side of the toaster - I'm working on the assumption that this is carbon film resistor.


texts: How to terminate Shield of USB connector to System Ground via Resistor || Capacitor or Ferrite Bead?

texts:
I want to know the best approach to connect USB connector's (receptor) Shield to System Ground?
Below are the two options.
PC(Earthed)<----- USB Cable ----> USB Connector female(PCB with NO metal casing or Earthing)

simulate this circuit – Schematic created using CircuitLab


texts: Limiting the input current with voltage divider

texts:
I would like to measure two signals with a microcontroller ADC:

0 to 5V, 5MHz
-36 to +36V 100Hz

simulate this circuit – Schematic created using CircuitLab

I want to draw as small current as possible from the input signal. I chosed the OPA365 amplifier to shift the signal and provide the current for the ADC.

My first question is how I should choose the resistors?
How can I change the value of the R15?

I don't have a DAC on the MCU, but I have GPIO, I thought I can connect TS12A4517 to switch between different resistor values. Is it a good idea?

simulate this circuit


texts: Why transistor pin outs are not standardized?

texts: I was replacing a BC548 with a BC639 without paying too much attention to datasheet details except the current rating. Obviously the circuit did not work too well until I checked the correct pins. Is there some manufacturing related reason or why the pins vary between two NPN transistors?


texts:
I need to drive an inductive load from an Arduino Due analog output.
The analog output delivers 0.55V-2.75V (yes, it doesn't deliver 0 volts).

I need to get something like 0-14V with up to 3A maximum and so that the output voltage is linearly dependent of the input voltage.

Now I am overwhelmed by all the possibilities to achieve this. I do not know if I have to use MOSFETS or Operational Amplifiers and so on. I have seen solutions like this but this doesn't get me currents up to 3A? I would like the simplest solution. If I can buy something small, even better.

I have also seen tools like the operation amplifier designer from TI but this gives step-down converter as results that convert a variable V_in to a constant V_out, which is not what I want. Or am I wrong?


texts: Zero-crossing signal inconsistent timing

texts:
I have an ESP-07 with NodeMCU firmware connected to a dimming module with a zero-crossing pin.

The current frequency should be 50Hz, which means that the time between two zero crossing should be 10ms, ~10000 microseconds.

However the time between two interrupts is sometimes correct, but often is about ~450 microseconds.

What's the catch? I use tmr to measure time

Here is the code:

gpio.mode(2, gpio.INPUT)

gpio.mode(5, gpio.OUTPUT)

t = tmr.now();

counter = 0;

local function zc_callback(level, pulse)

    counter = counter + 1;
    counter = counter % 200;
    if(counter == 1) then
        print(tmr.now() - t);
    end

    t = tmr.now();

end

gpio.trig(2, "up", zc_callback)

Thank you, I try to figure this for some time, it affects my light bulbs which blink instead of dimming.


texts: Probing an externally powered circuit using MSP432 connected to the PC

texts:
I have an circuit powered by an external SMPS and I'd like to debug it using a TI MSP432 MCU. The MCU is connected to the PC and I'll use TExaS Display software (it basically works as a cheap low-bandwidth scope for low frequencies). However, I need the MCU to be connected to the PC and the circuit to the SMPS - but the MCU does't use differential voltage measuring (it uses only the P4.4 pin as input).
So my questions are: do I need to connect both grounds (SMPS and MCU GNDs) for correct measuring (both the PC and SMPS are connected to the same power outlet)? If so, do I need to worry about groundloops/how to deal with them?
Thanks in advance.


texts: Trying to determine the output of a RC-filter with load

texts:
I have a low pass filter like this:

simulate this circuit – Schematic created using CircuitLab

\$V_{\text{out}}\$ is measured right after \$R_1\$, which I suppose means that it is measured over the parallel part.

\$R_2\$ is the load of the filter. When this circuit is measured with an oscilloscope it seems like it is not dependent on the frequency at all. I would like to investigate why.

I tried to calculate the transfer function for the filter, but I am not sure that it is right.

$$ H(j\omega) = \frac{1}{R_1\left(j\omega C+\frac{1}{R_2}\right)+1}$$

I'm using \$R_1 = 33\text{k}\Omega\$, \$R_2 = 1\text{k}\Omega\$, and \$C = 220\text{pF}\$.

If I plot the frequency response in Matlab with this, I just get a straight line going from the origin through (1,.5), (2,1) where (Hz, H(w)) and so on.

Is this correct?


texts: all. Anyone know what value this capacitor should be? It says 104... but that does not help.


texts:
The flexible flat cable of the LCD i want to use has these odd ground pads in the ends that i have not seen before. How is this handled in practise, does it turn the otherwise 37 pin connector into a 41 pin connector to account for the extra padding, appearing like approximately two extra pads in each of the ends or does this require some special connector/treatment?

It looks like a special locking feature for the connector is needed. Is there a name for this ?


texts: Development Board / Micro-controller with an onboard camera or external addon

texts:
I wanted to use a micro-controller with a camera module to be able to do some processing on the captured images. The Arduino was my choice, but since it has only 256K of Flash memory, it clearly is not a good candidate, I scoured Google to find relevant posts, but decided the Arduino is not the best tool. The closest Arduino came was with http://jarv.org/sdcam.shtml, using an SD card to store the images.

I stumbled across Leapord Board: http://designsomething.org/leopardboard/default.aspx, it has an onboard camera, unfortunately documentation and sample code is really scare for this.

Can someone recommend a good micro-controller that can allow me to use a standalone camera and perform simple processing on it? And more importantly has an active community, sample codes already available?

Would appreciate any thoughts!

EDIT: The ability to use a regular camera and process those images would be great if possible. I would assume this would be done via a USB interface, so the micro-controller has to be able to act as a USB host.


texts:
Knowing that I1 = 100mA, I3 = 300mA,
  UR2 = 10V, determine R2.

So I tried it like this: we know that in parallel connection, the voltage stays the same so UR2 = UR1 = 10V. Then, R1 = U1 / I1 = 100 Ohm. Also, I3 = I2 + I1 so I2 = 0.3A - 0.1A = 0.2A and so R2 = 10 / 0.2 = 50 Ohm.

Is this correct? I'm trying to learn for the exam but something doesn't seem right to me here.


texts:
I am reading the datasheet of an ARM Cortex chip, specifically the GPIO chapter. Ultimately, I want to configure various GPIO pins to use them in "Alternate Function" mode for read/write access to SRAM.

Of all the GPIO registers available, I do not understand two: GPIO_PUPDR and GPIO_OTYPE which are respectively the "pull-up/pull-down register" and the "output type register".

For GPIO_PUPDR I have three choices:

No pull-up or pull-down
Pull-up
Pull down

For GPIO_0TYPE I have two choices:

Output push-pull
Output open-drain

What is the difference between all the different configurations, and which would be the most appropriate for SRAM communication?

The documentation for the board I am working on is available here (see page 24 for the SRAM schematics). The reference manual for the ARM Chip is available here (see pages 145 and 146 for the GPIO registers).


texts: Recommendation for an inexpensive electric motor to drive a mechanical speedometer

texts:
I'm needing a small DC electric motor that could be used to drive a mechanical speedometer. This would be used for older cars that have been retrofitted with a newer engine or transmission that doesn't have a traditional older style cable speedometer drive.

I expect there will be an Arduino in the mix, taking ABS ring signals from the rear axle and converting that as required to drive the DC motor.

It seems that the standard is 1000 rpm = 60 mph, so to cover a range of 0-150 mph the electric motor will need to be capable of about 2500 rpm. The load is extremely low.

It sounds like stepper motors would be a good solution but they are too slow. Any other possibilities?


texts: KiCAD 5 ‒ Is ist possible for a footprint to have multiple courtyards?

texts:
One of the components I am using is really a daughterboard that plugs into two rows of pin headers. Under the daughterboards, between the pin headers, there is space for a additional components. I have therefor designed the footprint for the daughterboard with two courtyards, one for each row of pin headers:

However, this fails in DRC, with KiCAD (in the German translation) saying that the courtyard is "not a closed contour":

Is there a way to have multiple courtyards in a single component that passes DRC, or should I delete the courtyards altogether?


texts: Connection diagram of external WatchDog timer MAX6369KA+T and Arduino

texts:
Tasks:

Ensure a reliable reboot of the microcontroller in case of a hang.
The ability to disable the WDT timer.

For these purposes, I found an external watchdog timer MAX6369KA+T.

Scheme:

Logic:

WDI is directly connected to the IO of the microcontroller, which will send short-term pulses (HIGH-LOW).
WDO is pulled to 5V through a 10K resistor. A 1K resistor is connected in series, which should protect the RST pin from static voltage. If no pulses arrive at the WDI from the IO of the microcontroller, the WDO should go down and cause the microcontroller to reset.
SET2 is pulled to VCC to start WDT. The MAX6369 can be turned off by pulling SET2 to GND. For this, I want to use a bipolar transistor, which can be controlled using a separate controller.

Questions:

Are there any errors in the circuit?
On WDO, I set the resistor to 1K in series. Will this affect the reset process?


texts: How to make library and compile with vhdl code in verdi and in ncvhdl?

texts:
I don't know where to start from.
I want to compile VHDL codes by ncvhdl.

But I have met some error messages like this when I have compiled like this.

ncvhdl text.vhdl text1.vhdl

USE ZOTLIB.ZOTLIB_COMPONENTS.all
ncvhdl_p identifier (ZOTLIB) is not declared.

So how to make ZOTLIB and how to compile vhdl with libraries?


texts: What is this white component in this circuit?

texts: Can't figure out what is this component and also please mention about how to test it?


texts: Clocked edge-triggered timing (contamination delay)

texts:
I'm reading a book about computer architecture, and it says that, in clocked edge-triggered devices, the contamination delay is usually nonzero, and that the contamination delay for registers is assumed to be greater than its hold time, "giving it the important property that its inputs and outputs can be read and written simultaneously (that is, by similar devices sharing the same clock input)".

But I didn't quite understand this statement. As far as I know (I'm very new to this subject), contamination delay is a minimum time, measured after the active clock edge, during which the output remains valid after the input has changed (measured after the active clock edge), and hold time is a minimum time requirement measured from the active clock edge, during which the input data has to be kept stable. Why is contamination delay of register greater than the hold time, and how exactly does this fact allow it to be read and written simultaneously? Could someone give a more detailed explanation?

Update: I understand basically the importance of having contamination delay greater than the hold time in edge-triggered flip-flop in the situation where there are two chained flip-flops (that is, the output of the first one serves as input to the second one). When clock rises, the input to the first flip-flop gets sampled and propagates to the second flip-flop. Then, after one clock period, when clock rises again, the second flip-flop samples its input. But the input of the second flip-flop must remain at the same value for at least a hold time after the clock rises, if we want it to get correctly stored. So, the first flip-flop must guarantee that its output (which is the input for the second flip-flop) will not change for at least a hold time. That is, the contamination delay of the first flip-flop must be at least the hold time of the second flip-flop.

Is this correct? The part that I'm not understanding is why this fact gives to registers "the important property that its inputs and outputs can be read and written simultaneously (that is, by similar devices sharing the same clock input)".


texts: ipod headphone jack only driving one side - is there an easy way to fix this?

texts:
The headphones work fine in other devices.  If I push or pull the connector a little bit I can get sound from both.

It is apparently an issue in the mechanical connection of the jack.

Has anyone had this issue and fixed it?

It is out of warranty but well take care of.

This is the version 5th gen video/color ipod


texts: Generate DC pulse after switch turned off?

texts:
I've got a power source (say 12V DC) that I'm monitoring with a relay. I want to send a pulse (over 5V DC) to another relay for 60 seconds after the first power source has been turned off.

A practical example would be: A computer has been turned off and the power supply is no longer providing power, turn on a relay to turn on a light for 60 seconds (or send a 60 second 12V DC pulse to the relay).

I'm having a hard time finding a circuit for this. I'm fine using transistors/diodes/caps/sub $1 ICs/etc. but want to keep it analog.


texts: Direct control over Real and Reactive charge/discharge in a battery/inverter AC system

texts:
In a paper (page 31) discussing the installation of a battery(*) in an electricity substation, UK Power discuss the ability to control the real power and reactive power components. They go so far as to show a graph showing actual results compared to the ideal:

They also say:

  The ESS (ESS = Enery Storage System, i.e. the battery and inverter) had ‘out-of-the-box’ set-points available to control
  real and reactive power exchange between the 11kV network and ESS.

and:

  The deviation was dependent on amount of real and reactive power the
  ESS was set to import or export, for instance when expecting the
  export of 150 kW and 150 kVAr, approximately 149 kW (99%) and only 116
  kVAr (77%) were delivered. At another extreme, when set to export 150
  kW and import 150 kVAr, approximately 138 kW (92%) and -118 kVAr (79%)
  were delivered.

As far as I’m aware in AC real power is an outcome of resistive loads and reactive power an outcome of inductive loads (e.g. synchronous motors used in industry)

Let alone the fact that 2 of the quadrants above imply opposite charging/discharging for each power component, the following plot (page 23) shows the real power (ESS P) and reactive power (ESS Q) again being independent of each other:

I feel like I’m missing some understanding, such that I’m not even sure of what question to ask other than:

How is this arbitrary control managed?

How does a load cause such a lag/difference so that the plot above (fig5) is possible?

Simultaneously charging and discharging??

(*) LiPo, obviously inverted to AC, and used primarily to limit the peak of power demand from the usual supply – i.e. charging the battery when usage is low and then tapping into it when power demand is high...


texts:
Varistors are known to use for over-voltage protection, as they have high electrical resistance at low voltage which decreases as the voltage is raised.(wikipedia).

But is there any electrical component or simple solution to function reversely?!
In contrast, A non-linear resistor to have low electrical resistance at low voltage and high resistance at high voltage? or simpler closed-circuit when no voltage, and open-circuit when voltage greater than any constant applied?


texts: AA Battery charger and re-chargeable battery

texts:
I have a Canon digital camera that requires a 3.2V battery.

I'm trying to figure out what would be the impact if i use a re-chargeable battery that has 1.2V capacity.  For a similar reason, I need to know, if I buy a new battery of capacity 3.2V then what should the charger specification be?

I don't understand the concept of "Volts" as applied to battery specifications.  Can you explain how I could determine from the specifications whether or not a slightly different battery is compatible with a device?


texts:
I'm planning on using a dual inductor in series mode to increase the inductance.
I realize that the total inductance will be L1+L2+2M where M is the mutual inductance (when the polarity is connected to give aiding, rather than opposing, magnetic flux).

My question, though, is whether the saturation current will decrease by using this arrangement.  My initial thought is that it won't change (appreciably) since, although the flux is doubled, the effective core length used is also doubled.  Is my thinking correct?


texts: how to differentiate the gnd audio to gnd of battery?

texts:
i'm new to the forum.
I have some problem to Connect this device with one single battery. I think the problem is on the connection of the max4466 electret. It has a common ground and it make me impossible the connection with the pam 8403 that have separate ground. Audio- and battery -. How can i Connect it properly? Maybe a diode? i attached an image. when i use these chips with two different batteries it works very well. Please help me


texts: How can i convert an AC output from an outlet to a digital signal?

texts:
I´m making a digital frequency meter and want to compare the frequency from an outlet with a stable 1hz frequency from a crystal using an AND logic gate. However, I´m not sure how can i get a digital signal from the outlet. I will be using this project to measure frequencies from a function generator as well.
I deeply appreciate any help.

Edit: By "outlet" i mean a wall outlet with 127-220v 60hz, and the range is from 0 up to 99kHz. I´m a novice to digital electronics, so i thought an op amp was the best idea
Edit 2: i just want to know a way to get a digital signal out of an AC input so i can use with digital ICs.


texts: Are there methods to get the modulo of a variable voltage, with reference to another (constant) voltage?

texts:
If, for example, one has an input voltage of 5 Volts, and one wants to obtain this voltage modulo 3, as:

$$V_\text{out} = 5\mod 3\text,$$
 then how does one perform this operation using simple circuitry?

This is perhaps an unusual question, but the aim is to try and replicate the basic programming math operations (+,-,*,/,%) using the simplest circuitry possible, and with voltages.

So far, I found this old question from 2013 on the topic, , Is there a device to get modulo of voltage value? but over here (from what I understood), there's only the possibility of modulo 2n, n being the number of cascaded stages. If, one wants modulo 3 or 5, then how does one change/replace the circuit mentioned in the attached question's answer to do this?

There is also a circuit mentioned in this paper: https://www.academia.edu/2309394/An_8-bit_Voltage_Mode_Analog_to_Digital_Converter_Based_on_Integer_Division but even this states that the reference number for division (modulo) should be a proper power of 2?


texts: Connectting intercom audio into sound card

texts:
I want to connect the intercom in my apartment to a sound card, both input and output. The voltage of the intercom mic and speaker signals (2 different cables) is 12V while not load is applied. When the speaker or the mic of the intercom are connected, the voltage drops to around 4.5V. In the attached image you can see the signal on the mic wire when a 2kHz sine sound wave is played near the mic. As you can see, the signal saturates at around 4.6 peak-to-peak voltage.

So, i need a protective circuit to connect the speaker signal from my intercom to the mic input of my sound card and the mic signal from my intercom to the speaker signal of my sound card.
For the sound card input protection, I was thinking in using a decoupling capacitor in series, a 6:1 voltage divider and two diodes in parallel for over voltage protection. Is this enough? What about the grounds, do I need to use an isolation transformer?.
Edit: Added intercom schematic

The intercom is a wall-mounted phone.
The six wires in the top left go inside the wall.
J1 and J2 are connected with a 4-wires patch cord, just like a normal telephone.
L1 is the buzzer.


texts: In a boost converter, should ground plane be placed underneath the gate trace?

texts:
When designing the PCB layout for a DC-DC boost converter, one does not place a ground plane under the inductor, to prevent induced ground currents. Also, for SMD MOSFETs, the drain (switch node) usually serves as a heat sink, so, since it should be small but sink a lot of heat, it makes sense to pour it on both sides, connecting them with vias. Which means no ground plane underneath the switch node (I'm using an IRFH5025, if you'd like to visualize what the package looks like).

However, I am not clear on whether it is beneficial to place the ground plane under the rest of the MOSFET, specifically the gate trace, sense resistor, and current sensing filter.

On one hand, this might limit magnetic interference from the inductor. On the other hand, it would increase MOSFET gate capacitance and provide another path for return current, right underneath the quite sensitive current sense trace.

Here's a picture with the area I'm considering marked in orange:

So, should I leave this area clear of the ground plane?


texts:
I want to safely charge a 110V capacitor to 36V without it causing any damage (the reason we can't charge to 110 is that the battery is too small). Is there a way to calculate what resistors and how many I will need? For more info, I have 3 12V batteries connected to each other.
Edit: My teacher helped with some calculations and I was able to charge one 110V capacitor to 36V in a couple seconds with a 220 resistor. I would still like to know how he made the calculations though, because he never explained what he was doing.


texts:
I am looking to build a light stick.

I am quite new to electronics and have just been experimenting so far. My light needs to be portable so I am using a 3.7v LiPo battery (I am into RC so have some lying around). I initially thought that wiring my LEDs in parallel would be best as it requires no voltage boost but I seems like it will use more battery that way.

I looked at linking them up in series but I have about 16 and need a voltage of around 51-52V to run them in series. From what I have read this uses fewer amps for better efficiency but I don't know if this is correct.

The voltage regulators seem to get quite bulky when you up to a higher voltage. What I was thinking of was creating segments of LEDs in series and put the segments in parallel using multiple step up voltage converters in one project.

Would it be ok to use more than one and would you recommend using a pre-made one or incorporate it into my design and have it on the board.


texts: MIC1557 clock frequency constantly increases. Why?

texts:
I'm trying to get a 19.2 KHz frequency out of the MIC1557 clock generator.

I managed to get close enough (enough for my application) to this frequency with off the shelf components.
The shematic is basically the same as in the first page of the datasheet under "Typical Application", the schematic on the right "MIC1557" ( not the 1555).

Resistance is 3.4K (composed of 3 resistors in series) (instead of 1k in the schematic) and capacitance of 0.01uF (one capacitor).

I also tried the same combination with 34K (also 3 resistors in series) and capacitance of 0.001uF.
All resistors and the capacitor are SMD.

In both cases, I get a frequency of approximately 19.2 KHz (+- 0.1 KHz).

The problem is that this frequency is increasing constantly and regularly. After half an hour it's about 0.5 KHz higher.

It happens also when the oscilloscope probe is disconnected. When I reconnect it the frequency incrementation is the same.
And nothing seems to stop this. Please help.

(I know using a crystal oscillator is a better solution. But this one, with the MIC1557 is much cheaper and doesn't generate any high frequency.)


texts: Custom Boards With Custom Programmed Microcontroller

texts: I have built a prototype for a project that I'm trying to manufacture. The prototype uses an arduino, but I'm unsure how to get that produced on a larger scale. If anyone has any suggestions, please let me know. I'm really just in search of a way to get my the code that I loaded onto my arduino built into an AVR microcontroller, and how to implement that into my design. If it helps, I'm only using nine pins, and my arduino is an uno. Also, where is a good place to get boards manufactured that include sockets for microcontrollers. I havent' decided how many to manufacture yet, not until I work out this and a few more kinks.


texts: Filtering out TRIAC's triggering current spike on the mains

texts:
I've got my 2KW heater controlled by a home-made dimmer, on 230V/50Hz mains. It's using the common TRIAC delayed command process. The TRIAC (BTA24-800BW) is a snubber-less kind, drived by an (non zero cross detect) opto-triac (MOC3021) parallel mounted on A2/G.
When switching on, the line voltage can fall by more than 100V in less a µS and re-stabilizes in about 20µS. This wave floods the whole home grid, an illustration is that it even makes the induction hob noticeably noisy. Indeed, the maximum effect is at mid-power so when the mains voltage reaches its peak (320V).
I've tried to put a non polarised 1µF capacitor on the dimmer plug, this reduces only by less than 50% the spike. I also tried to put the capacitor on the induction hob plug, but observed the noise doesn't clearly reduce !
Once the induction hob died but the warranty where still running. I can't proove if my dimmer spikes could be implicated, but I'm nearly sure my device is far no conforming to basic electrical standards.
So my question is : What's the best solution to fade the spikes. And L/C filter ? On the mains side or heater side ?

The scope screen-shots (from wide time scale to very tightened) :

peak's magnitude (peak acquire mode) at mains frequency scope :

resonance after the spike, recovery time :

zoom on the spike itself :

nearly exact schemata (lately reconstructed) :


texts: A theoretical question on probe resistances for a voltage measuring device

texts:
As seen in the figure above, a current regulator is providing a constant current looping through the series resistor Rshunt. Input impedance of data acquisition device is 10 GigaOhm. Can we say that almost no current passes through the probe resistance Rcable(since input impedance is huge) and therefore there is no voltage drop across the probe cables? How can I relate this resistance to input impedance of DAQ device and can I just neglect the probe resistance?

Can I quantify the error caused by Rcable here in relation with DAQ inout impedance?


texts: Are there advantageous situations when we cascade filters by descending Q-factor instead of ascending?

texts: We usually cascade filters in ascending Q-factor to avoid saturation in each individual stage. But are there advantageous situations when we cascade filters by descending Q-factor?


texts: Signal leakage when volume is turned all the way down

texts: I was hoping I could get help with a design I have breadboarded/diagrammed with regards to a low level signal still present when I have my volume pot turned all the way down. When I turn my volume control down all the way there is a low volume/high treble sputtering distortion signal that's still audible. I thought is was a grounding issue on my volume pot but it's not coming from there, not exactly sure where it's coming from. I hope I tagged this correctly as I'm still learning proper terms.


texts: How to deal with voltage sag from a motor starting

texts:
I have a buck converter LM2956, same as
 here

stepping down voltage from 12 to 8 volts. A motor turns on from the regulated stepped down voltage, and when it does I get a voltage sag that drops the voltage down 1.5 volts (so from 8 to 6.5). it lasts for about 2 milliseconds which is unacceptable for my application.
How can I deal with this voltage sag? I have no passive components from the regulated 8volts to the motor driver.
attached is an oscilloscope image of the sag when starting the motor from the regulated voltage(goes from 5.4 v to 4v for 2 milliseconds in the image). This is messing with sensor readings a microcontroller reads by ADC. How would I go about solving this voltage sag problem.

more info:
the motor I use
on load current < 1A
stall current 2.2 A

the lm2956
max current 3A


texts:
For testing purposes, I need two circuits: 220Vac rectified and 48Vac rectified, both having the same reference, like this:

But I don't have an isolated transformer 220V:220V. I only have an isolated transformer 220V:48V and an autotransformer 127V:220V.
If I connected like that, since autotransformer has no isolation, I'd say my circuit would be equivalent to the following:

I understand that working not isolated from the mains is dangerous but it would be a quick test of a simple circuit. I'd like to know, are the two circuits above equivalents in terms of references? Is there any problem connecting it like that?


texts:
Does anybody know what this could be?
It is wound 1:1, and each winding has 17.9ohms and ~20mH. I've removed the ferrite (It was brittle and reacted to a magnet) and it was a typical E I.

In a different thread (are common and differential mode chokes interchangeable) it was suggested that coupled inductors (pulse transformer) are used for this task.

It's used in a powered bus, as seen in the diagram below. I drew it as a differential choke because that's how I understand it should work.  It blocks a superimposed ~20kHz signal from entering the power section.


texts: How to use two Demux to index a matrix layout of registers

texts:
Consider the following. Let's say for simplicity sake I have an arrangement of 8 bit registers in a 4x4 matrix layout. I could easily use a Demux that has a 4 bit input select line for the addresses with an 8 bit data input and from that address line I can then easily select which of the 16 registers I want to access.

Instead of using a single Demux let's say I want to use 2 Demuxes to do the same thing except I want to designate one Demux to represent which row and another to represent which column.

I'll still be using the same 4 bit address line only I was thinking of using a wire splitter and using the 2 lower order bits of the address line for one demux and the two higher order bits of the address line for the other.

How would I be able to set up the arrangement of these Demuxes to access the appropriate row and columns of my matrix arrangement of registers?

Do I need to feed the data line into both demuxes? Would I need addition logic or muxes to combine the two lines? Or would a decoder help in this kind of situation? This is where I'm getting stuck at in my design decision.

I could use a single Demux however due to the limitations of Logisim my actual registers are 32 bits each and I have an arrangement of 8x8 registers for a total of 64 registers. I'm planning on using this as Cache for my CPU instruction register or instruction decoder.

If you need any more information than this or need any kind of diagrams or images let me know and I'll upload - post them upon request.

Here's my 16x1 byte register arrangement using a single Demux:

I want to make something similar however it won't be 4x4 as it will be 8x8 and the registers won't be 8 bits as they will be 32 bits and I was planning on using 2 Demuxes one for the row and the other for the column.


texts: Wouldn't Charge Flow On Power Lines Due to Capacitance

texts:
If I touch one line of an exposed power line (say 300 kV AC) and the rest of my body is freely suspended (only in contact with air), am I not forming a capacitor (to ground)?  If I am, are electrons not flowing in/out of me as I charge/discharge?

Is my understanding that this forms a capacitor incorrect, or is the capacitance such that electron flow is small despite the high voltages associated with power lines?


texts: Do USB Data Wires (D+/D-) have 90 ohm differential impedance and single ended 45 ohm impedance to ground and if so how is this made?

texts:
I understand that USB data transmission is done over various speeds where transmission line effects could come into play(max 480Mbps which means a max frequency that is much higher considering the square wave harmonics/edge rate, perhaps 5th harmonic for 2.4GHz max significant signal frequency content) as a differential pair with controlled 90 ohm differential impedance or 45 ohms to ground for each individual wire in the pair.

My question is if it's true that ANY USB cable capable of transmitting data must have D+/D- wires manufactured in a precise way as to maintain this impedance along the length of the cable. If so how is this done? Surely this must require some complex calculation involving inductances/capacitances and very specific spacing between the wires and surrounding ground shield that must maintain constant over the length of the cable, right? Do all cable manufacturers really take this into account?

Or am I wrong and the cables do not need to achieve this characteristic impedance at all? Does it depend on the length of the cable such that normal cable lengths do not need to worry about this?

Taking a random USB cable picture off google it doesn't seem like the data wires get any special treatment...


texts: Do DSL / ADSL modems have an ADC with ~ 2 MHz sampling rate?

texts:
For fun and no real practical use, I'm trying to design a DIY modem that can transmit data over an audio line, like old 56k modems did. I'm studying how to pack bits of data efficiently in a 1k-15k audio spectrum, such that I'll be able to de-modulate it later.
During my readings, I saw that DSL modem use the 25 kHz - 1 MHz spectrum, in order to avoid interference with voice on the telephone line.
Question: on the demodulation side, in order to be able to do digital signal processing (FFT, etc.) to identify peaks of spectrum at, say 400 kHz or 800 kHz or 1 MHz, one needs a 2 MHz sampling rate (Nyquist).
Do (A)DSL modems have ADC (analog to digital converters) with 2 MHz sampling rate?
Same question for dial-up 56k modems: what kind of sampling frequency did they use at the ADC/DAC stage?


texts:
In my design I want to connect a PHY (88E1512) to a switch which contains another PHY (BCM53115M). The devices are separated by a few inches of PCB and will be impedance matched. Both have the same ground reference but different power supplies. Ethernet also seems to have a 1m distance requirement between ports.

I'm able to place magnetics in between the two but I wanted to know the logic behind requiring magnetics between two on board PHYs. I have also heard of using capacitive coupling instead of magnetics all together and was wondering for such short distances are magnetics better or would simply capacitive coupling be better like in this question: Connecting two Ethernet PHY without magnetics?

Note: Both devices seem to have termination inside them.


texts: In relation to the answer at https://electronics.stackexchange.com/a/298969/35737, namely when the switch buttons needs to protrude through the casing. I do not have special equipment for precision cutouts in the said casing Is there any way for me to easily match the cutout with the protruding tactile switch button ?


texts: Designing a stiff voltage source using an emitter follower

texts:
simulate this circuit – Schematic created using CircuitLab

I am new to electronics, and I am trying to do Exercise 2.2, page 67 of The Art of Electronics.

  Use a follower with base driven from a voltage divider to provide a
  stiff source of +5V from an available +15V supply. Load current (max)
  = 25 mA. Chose your resistor values so that the output voltage doesn't drop more than 5% under full load.

According to my understanding, a BJT in emitter follower configuration has its emitter following the base, no matter what the emitter signal is fed to. Therefore, under normal operation the emitter follows the base (with a 0.6V difference because of forward voltage drop), and is not really influenced by what's connected to it.

We need to find resistor values so that even under maximum load current 25mA, the emitter voltage never drops below 5V - 0.05*5V = 4.75V.

If I set VE(minimum) = 4.75V, I(load,maximum) = 25mA, I can compute the corresponding minimum load resistance value but I believe this is useless and is meaningless.

If there is no load, I set VE = 5V. So VB = 5.6V. I would have used the voltage divider equation to find the ratio needed between R1 and R2, but I am not sure this is valid since there is a current going through the BJT collector.

I am kind of lost on what i need to do. It's the first design question I try, it seems like there are more unknowns than constraints and so we have to set some values, and I have no electrical intution/experience to know what to set to which value and why.

Thank you for your help.


texts: Can I put Two AC coupling caps on PCIE bus?

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Do you think if there is a problem when I have two AC coupling caps on PCIE bus, 220nF and 2.2uF?
Since 220nF on the daughter card and I want to put mid probe on main board.  For the transmitter from main board to daughter card, we need to place AC coupling cap before the mid probe.  so that's why I have two caps on PCIE bus.


texts: Voltage fed versus current fed Inverters

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I would like to ask about voltage fed and current fed inverters.

I know that a voltage fed converter uses a capacitor as the storage device while a current fed converter uses an inductor.

What are the advantages and disadvantages of these two topologies and why should someone choose the one over the other?


texts: Power Barrel Connector Voltage Rating Inquiry

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My system is using 48V at 3A max. I am currently looking for a power connector to my PCB that can handle my specifications. I came across a potential connector, but I noticed on the data sheet it is rated for 24VDC and 5A. How does the manufacturer determine the voltage rating? Could I get away with using it at 48V if I am well below the current rating?

Part of interest: PJ-037BH-SMT-TR