texts:
So I went to a local electronics retailer, Communica in Cape Town yesterday. I had a small shopping list including:

10x 10µF Ceramic Capacitor
10x 0.1µF Ceramic Capacitor

The vendor didn't have any unpolarised capacitors, so he gave me the ones, as in the photo attached.

I immediately but respectfully commented, that this is a POLARISED electrolytic capacitor, and the sales chap cut me short, saying, it's unpolarised.

Am I subconsciously smoking something here? I admit I haven't been involved in electronics too long to have earned any badges, but I'm pretty sure that both the salesmen I asked are wrong.

I need the caps for decoupling in a USB + PIC32 MCU circuit (see image below), so I also think that 100V tolerance is a bit overkill, 10V will probably do, right?


texts: esp8266 doesn't work when connected to same supply as relays

texts:
The problem:

Circuit one (with Arduino Nano) did work fine. I used a separate power supply (5V wall wart) for it, because I didn't think that the on board regulator could handle 12V.

Circuit two (with NodeMCU) does not work - either does not turn on, relays are being switched chaotically, does not connect to wifi. When I disconnect the D1-D8 pins from the transistors, it turns on and connects to wifi. I guess, when I will connect the NodeMCU to a separate supply, all will work as expected.

My question is - why can't it be connected to the same +12V? Is there something horribly wrong with the second circuit?

P.S. The project is controlling three AC motors that move metal blinds (security shutters). I made the original circuit a few years ago, now I wanted to add wireless connectivity via blynk. I know that there should be flyback diodes across relay coils, but at the time I didn't know that, and the thing was functioning fine without them. I will probably add them now, however.

Thanks


texts: What does the prefix "+/-" indicate before the data line names?

texts:
At this link there are specs of a converter with the following excerpt:

What does "+/-" sign indicate(mean) above before TxD or DATA?

As far as I know TxD pin/line transmits and RxD receives the serial pulse train.

But what does the extra prefix "+/-" indicate then?

(And are these data lines always isolated from the ground of such converter? What is meant by Isolated RS-485 converter?)


texts: Two-tap voltage divider, why can't I solve for the center resistor?

texts:
Background

I'm working on a circuit involving an AC-excited sensor bridge, and am trying to figure out ways to detect a short between the two bridge legs, as that causes the bridge to fail to the "wrong side" (i.e. indicate all is well, when the sensor says all is not well).  One idea I had for this was to bias the in-amp that measures the bridge into its operating range from the input side, so that shorted inputs would cause the output common-mode voltage to shift dramatically, rendering the failure detectable by downstream circuitry.

The problem

So, I set to design a simple bias network to do this task:

simulate this circuit – Schematic created using CircuitLab

From this design, I went to solve the circuit for R by treating it as two voltage dividers with equations as follows:

$$V_1=5\frac{R+1M\Omega}{R+2.23M\Omega}$$
$$V_2=5\frac{1M\Omega}{R+2.23M\Omega}$$

However, when I plugged in a V1 of 2.2625V and a V2 of 2.2375V (2.25V +/- 12.5mV) and went to find my unknown R by treating the equations as a system, I was unable to come up with a solution, either by hand calculation or using Wolfram Alpha.  Initially, this was because I had R1 set to 1MOhm, which was correct for an original center voltage of 2.5V, but wrong for the current center voltage of 2.25V.  So, I solved a simple voltage divider for that center voltage and transposed the R1 I found (1.23MOhm, in E192) into my working circuit, but that didn't work either -- I'm getting far closer now, but it seems like I may have run out of resistor precision before I can get the small differential voltage drop I want?


texts: Using a capacitor to buffer power to eMMC

texts:
Sorry in advance for what may be an elementary question. I'm designing a circuit to provide a few hundred milliseconds of backup power to an eMMC module in case of power loss. This is to provide the module a chance to flush any pending writes to prevent corruption. My thought was to simply lay a sizable capacitor in parallel with VCC and GND. But I'm assuming I'll need to do something to ensure that power supplied to the eMMC while the cap is discharging is cut as soon as the voltage dips below 3.3v, so the eMMC module doesn't flicker on and off during that time.

So first, is this in fact an issue I need to worry about, or does it not matter if the eMMC flickers for a short duration or is supplied too low of a voltage? Second, assuming it does matter can someone suggest an MCU or something to handle this?


texts: Are laptop cells balanced while charging?

texts:
I have little-to-no knowledge about how the laptop batteries work.

I know there is a microcontroller to actually verify the balancing between cells (and in case blow up a fuse or something similar).

I was wondering, does the recharge circuit balances cells as well while charging?

Is charging procedure the same of the external chargers (diffent CV/CC phases) ?


texts: Scale and Shift Analog Voltage with a Single Op Amp?

texts:
I am looking to map the output voltage from the onboard DAC of an Arduino Due from its raw range [+0.54V --> +2.75V] into the new range [-10V --> +10V]. I will use an op amp with -12V and +12V power supply rails (Analog Devices OP07).

Orignally I tried to do this with back to back op amps - one to shift the voltage down (by subtracting ~1.65V) so it is first centred around zero, and then a second amplifier  to scale up the voltage by a factor of ~9.

However, I wonder is it possible to do this with a single op amp, and without inverting the signal's phase with respect to the input? In addition, I would like any reference for the bias point to be derived from the existing +12V supply rail.

Does anyone have any help on how to achieve this?

Many thanks


texts: Sine to sqare waveform but with variable peak-to-peak input

texts:
I need to calculate the speed of a little generator that produces a bipolar sinusoidal waveform with a peak to peak voltage value variable with the velocity. The produced signal also has a frequency proportional to the velocity. I prefer to process the frequency than the voltage, because I have a direct relation between revolution and speed. Four produce periods are corrispondent to one revolution of the generator drive shaft.
My requirements are:

Max RMS output generated voltage = 45 volt, at the maximum velocity.
Max output generated frequency=50 kHz at the maximum velocity.
A square signal circuit output to be sent to the micro min = 0 V, max = 5 V.
Only unipolar voltage to 12 V or 5 V to supply the circuit.

So I thought to a Schmitt trigger op-amp comparator like this.

But I have two problems:

Due to the variable peak to peak signal I cannot fix the two comparator's threshold VH, VL.
I have to scale (I think) the voltage produced by the generator to avoid to damage the op-amp. Here could be sufficient a voltage divider to the non inverting pin, fixing the divider resistors to have a value that at the maximum RMS signal 40 V, produce for example Vcc.

Any idea how I could proceed?

update:I attached a wrong figure (a comparator), instead I would attach a schmitt trigger because from what I read, the only comparator (without positive feedback) could create false trigger in the output due to a noisy input.

Thanks a lot.


texts:
Possible Duplicate:
  Calculating dBFs from RSSI

My RF chip doesn't have any RSSI output, just ADC I and Q. I was wondering is it possible to determine RSSI from ADC's I and Q values and adjust gain regarding to this? Someone suggested calculating RSSI as a vector magnitude.

$$
RSSI = \sqrt{I^2 + Q^2}
$$

Or could I just look at the outputs from ADC and if they aren't using full digital range e.g. 12bits, after some sample period, I make my AGC decision based on this.

Any good papers available about doing digital automatic gain control based only about ADC's I and Q outputs? Because all the papers those I have found from the net, usually use RSSI value for AGC.


texts: Using PIC18F4520 to measure slow period/Frequency

texts:
I have been trying to find a solution to measuring a relatively slow frequency using the PIC18F4520. The frequency range I'm attempting to measure is in the range of .5 to 20Hz. I need to have a 1 decimal place resolution.

The code I've been attempting to use is not producing results. When I use the variable 'period' unsigned integer, I get all zeroes. If I attempt to use the variable 'result' float, I receive bad data. I am relatively new to using CCP but because of the slow frequency, I felt this would be the best solution.

How can I measure a relatively slow frequency of 0.5 to 20Hz with a resolution of 0.1 Hz with the PIC timers?

//PIC18F4520
//Using CX8 ver 1.40

#include<stdio.h>
#include”lcd.h”
#pragma config OSC = XT // XTAL = 4MHZ External
#pragma config WDT = OFF

void InitGPIO()
 {
    DelayMS(10); // POWER UP DELAY
    TRISCbits.TRISC2 = 1; // CCP1 : CONFIGURE AS INPUT PIN
    ADCON1 = 0x0F ;
    TRISD = 0x00;
    TRISE = 0x00;
 }
 void CCPInit()
 {

 T3CON = 0X81;
 CCP1IE = 0;
 CCP1IF = 0;
 T1CON = 0X81;
 CCP1CON = 0x05;

 }
 void main()
 {
 unsigned char string[10];
 unsigned int start,end,period;
 float result,Frequency ;
 InitGPIO();
 InitLCD();

CCPInit();
 LCDString((char *)”Frequency Period”);
while(1)
 {
 while(!(CCP1IF)); // Wait First Rising Edge
 CCP1IF = 0; // Clear Flag Not Next Round
 start = CCPR1; // Save Value of First Rising Edge

while(!(CCP1IF)); // Wait Second Rising Edge
 CCP1CON = 0x00 ; // Disable CCP1 Capture Module
 end = CCPR1; // Save Value of Second Rising Edge

 period = end-start; // Subtract end – Start
 period = (float)period;
//Also attempted
    //results = end-start;
    //results = (float)results;
    //Frequency = (1/results );
 Frequency = (1/period );

LCDGotoxy(1,0);
 sprintf(string,”%.3gKHz”,Frequency);
 LCDString(string);

sprintf(string,”%.3gms”,period);
 LCDGotoxy(1,10);
 LCDString(string);
 }
 while(1);
 }


texts: Altium issue: Clearance design rule between via and pad of same net

texts:
In Altium PCB designer I have setup the following default clearance design rules:

At the beginning I had this rule to be applied only to different nets but I later realized I need to have some rules for objects of the same net. Mainly to have a minimum distance between vias and pads of the same net.

So I then changed this rule to be applied for any net. Although this achieved what I wanted, it also created thousands of new violations that are mainly related to not having enough distance between a via and a track of the same net. See for example the images below. The first one shows all new violations that came after I changed the rule and the second shows one example of "false" violation:

However this is totally wrong, since in this case the track in intentionally connected to the via. However Altium thinks this violates the design rules.

Which of course makes somehow sense. I mean by following blindly the rules set, the tool should indeed raise these violations.

But then the question is how to achieve what I want without having all these "false" violations that appear where there is basically short-circuit / correct connection between track segments or track and pad or track and via.


texts: Proper way of designing a battery backup system with 12V/5V dual output AC power supply?

texts:
I have a project (doorlock) with MCU / LCD / Keypad and solenoid (lock) connected together. MCU, LCD and Keypad runs at 5V while solenoid runs at 9V to 12V. I'm currently powering the system with an AC power supply that has 5V/12V dual output.

I'd like to add a rechargebale battery backup system to this, with 6-pack AA rechargeable batteries attached so that the power is kept on even if the AC power goes away, but since the AC power supply has a dual DC output, I'm not sure how to properly implement this. Here's what I've designed so far:

J1/J2 are connectors for 12V line and 5V line respectively from AC power supply and J3 is the connector for 9V (6 x AA) battery. The batteries should recharge slowly if PSU is on given that a small current flows into R1 to batteries. When power from the PSU is lost, the 9V battery line should provide current through the D2 schottkey diode. For 5V line, I'm using a TPS2110 to auto select between 5V (PSU) line and 5V (Battery, from LM7805) line.

Edit: I'd also like to know if my choices of R2 and R3 seems correct. I'd like the battery voltage to be selected if 5V from power supply falls below 4.6V.

Would this work? Are there any modifications I should make?

Edit: Fixed diagram (Previous diagram had an extra schottkey diode which doesn't belong there)


texts: putting the decoupling capacitor merely/only near the vcc line

texts:
I know I am wrong, this question is just to understand logically why, I am not an engineer but an hobbist
While designing a pcb for a mcu I should put a decoupling capacitor near each power lines. We do it because the current draw of the ic could change and the capacitor will supply it immediately
Until here i hope we all agree
but why can't i put this cap only near the Vcc?
this is a hyperbole/example of what i am trying to say:

I heard that the answer could be: "Because the electrons moves from - to +" but i don't think that this is correct logic, because this could bring me to make the board in the opposite situation: the cap near gnd and a very long track until vcc
I hope that i m not going to "shock" anyone with this dumb question, please it is just a curiosity


texts: What's the best way to fit many components onto a Eeschema schematic?

texts:
I'm using Eeschema right now with A4 paper size and I've noticed that many component symbols are simply too large to fit onto the schematic or at least the part selected by the template.

The two most obvious brute force options are to simply set a larger paper size, but since A4 is the standard paper size here, it would make printing more difficult.

The other option would be to simply change the symbols in the libraries so that they are smaller, but that seems like a lot of work.

So is there any smarter idea to fit more symbols on the schematic?


texts:
Im trying to design a logic circuit for a 3 bit adder using 6 inputs, A2, A1, A0, B2, B1, B0 and 4 outputs, s0, s1, s2 and c (the carry out). I already have circuits for a half adder, full adder and a 2 bit adder. I thought I understood the concept behind it and iterated upon the 2 bit adder that I got working earlier but for some reason I'm not getting the correct answer.

My logic:

a0 XOR b0 = s0
(a1 XOR b1) XOR (ao AND b0) = s1
(a2 XOR b2) XOR (a1 AND b1) = s2
((a2 XOR b2) AND (a1 AND b1) OR (a2 AND b2)) = c (the carry out)

I'm testing values and when I try to following combination
a2 = 0 , a1 = 0 , a0 = 1, b2 = 1, b1 = 1, b0 = 1 . s2 shows 1 when it should be the carry I believe that should be 1 because, (001 + 111) = 1000, right? Could someone let me know where Im making a mistake? Thank you.


texts:
I'm generating a square wave as PWM whose frequency is set to 25 Hz. On the oscilloscope, I've got:

The data referred to the image above was stored and maniputed, then I plot it using jupyter notebook, as shown below:

Applying the FFT to that signal,I've got:

The main question is: wasn't the main peak (the 2.7 V) supposed to be near 25 Hz?

UPDATE: I just did the corrections that you tell and
the visualization is better! I'm still obtaining the main peak in 0 Hz, but the second harmonic is in 25 Hz ( but the amplitude is low). I also didn't get the 13 V dc offset that Chris pointed out.

UPDATE 2: I subtracted the average dc level (1.35 V)  from the signal as most of you told me and I got the result I believe it's correct now:


texts: How to make a pairing and mode button on a remote control receiver

texts:
I'm working on a remote control project and have come across many different RF receiver/transmitter modules.  Many have a pairing/mode button on the receiver that serves to pair the receiver and transmitter and to choose which mode the transmitter is in, momentary, latching, toggle, etc. Is this feature done with a microcontroller? Can I buy the chip preprogrammed or do I need to use something like Arduino? How could I duplicate this feature on a receiver that does not have it? Thanks.
Has feature:

Doesn't have feature:


texts: Negative Voltage Level Shifting to an ADC

texts:
I am currently building a project that uses an AD595 analog devices chip to linearize the output of the Thermocouple sensor to 10mv/deg C. This output is to be connected to the ADC input of a Zigbee radio, with a max input of 1.2v. Given that the Zigbee input determines the range, this would achieve a 0-120 degree temperature range. I am now trying to adjust this design to also sense negative temperature.

The AD595 chip can run as dual-supply by connecting -5v and +5v, to give both positive and negative output, however The zigbee radio will not accept a negative voltage input. I believe i now need to place in the design a Non-Inverting Summing Amplifier to "level shift" the range so that "-1.2v - 0v - 1.2v" becomes "0v - 0.6v - 1.2v" and can be interperated by the ADC. I am fairly new to this and i'm not sure where to start, it being especially difficult using a negative voltage.

So far i have used a voltage divider on the output to produce a 5mv/deg C output thus increasing the temperature range to 0-240 deg C. I will have a regulated 5V (ad595), 3.3V (for zigbee) and -5V (for dual) supply.

If anyone could help or point me towards worthwhile resources i would appreciate it a lot.

Thanks.


texts: I read in the lecture slides to a VLSI course that clock gating also can lead to a decreased chip area size. In my understanding, clock gating decreases the chip size as this technique requires an additional FF + and gate.


texts: Normal Mode of CAN Controller in STM32L476 Nucleo Board is Not Working

texts:
I am using STM32L476RG Nucleo board which contains only one CAN controller(bx_CAN1) and SN65HVD233 as a CAN Transceiver. I could able to test the CAN controller by using "LOOPBACK Mode".
Since my Intention is to develop an Interface between CAN to USB I have to use "NORMAL Mode". But whenever I am using "NORMAL Mode" I can not see any output.
When I started the debugging process I have observed some points, which are as follows.
-> In CAN transmit status register (CAN_TSR) TERR0(Transmission error of mailbox0) bit is set.
-> CAN receive FIFO 0 register (CAN_RF0R) is not getting updated about the message pending info in the receive FIFO (FMP0[1:0]: FIFO 0 message pending).
-> CAN error status register (CAN_ESR) shows that there is an Acknowledgement Error(LEC[2:0]: Last error code).
Here I have used only polling method to send and receive data from CAN controller. I have added the details about BIT Timing Parameters along with this.
I used a terminating resistor(120 ohm) across the CAN_H and L terminals and tried the process. Result was same, I did not get any output.
For testing CAN controller in Normal Mode should the CAN Bus contain atleast 2 Nodes?
By using a single STM32 MCU can't we check the Normal Mode of CAN Controller?
Can anyone help me to find my problem and further steps need to be done?
I have added BIT Timing parameter Image along with this query.


texts: Zigbee communication outdoors at long distance ( around 1 - 1.5 km)

texts:
I am planning to put some control boards around the school campus ( planning to use Arduino board with some add-ons). I would like to communicate with these boards and was thinking of Zigbee.

The distance between two controller boards is around 1 - 1.5 km. However, searched wiki that the distance depends on the line-of-sight of the transmittor.

Outdoors with line-of-sight, range may be up to 1500 m depending on power output and environmental characteristics

The environment I intend for installation has many buildings, thus no "line of sight" between each controllers. So, is there anyway I could use Zigbee (perhaps add I few more points for data collection and transfer)? Or is there any other communication media I could use?


texts:
I think I have designed a current regulator. This is the circuit diagram:

simulate this circuit – Schematic created using CircuitLab
The operation is very simple. Let's say the transistor turns on at a voltage Vo.
For 0<V1<Vo if we increase V1 a little bit according to Ohm's law the current in the overall current will be increased but the current going through the transistor will be increased as well (a little bit) and according to KCL the current through RL will remain costant.
The bigger the value of RL, the better it works. Also the more heavily doped the transistor the better it works.
However if V1>Vo the transistor becomes almost a short circuit and current through RL goes to 0. That's why I need transistors with on voltage somewhat bigger than 0.7 (2.5V would be okay) in order for this current regulator to have a practical voltage range of operations. Where can I find these transistors?
Where can I find transistors with on voltage > 0.7V?


texts: Memory limitations on interfacing SD Card with 4-bit SD data transfer mode

texts: I am trying to interface a 4GB SD Card in my application using 4-bit SD data transfer mode, but some of my friends said that the 4-bit SD data transfer mode supports upto 2GB SD Cards and above that memory you should use SPI interface. Is it true that the use of 4-bit SD data transfer mode only works upto 2GB. If yes, why is it like that?


texts: Digital Comparator from LSB to MSB using Lookahead

texts: This is homework to be upfront, but I'm really stuck on it and just need some kind of direction. I've been assigned to create a 16-bit lookahead comparator going from LSB to MSB using no more than 4-bit lookahead. The professor also said to remove the equals output and design the system so that when the two numbers are equal both less than and greater than will output '0'. I've been able to design the comparator, using a k-map, and defined the greater than and less than signals in their propagation forms., but I don't understand how the lookahead logic is supposed to work when going from LSB to MSB. Any help would be greatly appreciated.


texts: How long can equipment go unused before powering up runs the risk of damage?

texts:
I have an older solid state radio transceiver I want to power up but I understand that electrolytic capacitors loose their function after a long time of non-use.  There are articles about reforming electrolytics, but not much is said about how long electrolytics can be unpowered before precautions need to be take on powering up again.

The equipment is non-critical, no tubes, linear power supply.  It is a TenTec Argosy II amateur radio transceiver.  I can replace the caps if I need to.  (And, yes, I am licensed to use the radio.  KD4TTC)


texts: Three-phase rectifier for offline single-phase supplies

texts:
First thank you for the help. I'll try to explain my self for this problem and sorry in advance if I'm not very clear, english is not my native language.

I'm making a universal PCB design involving an AC/DC converter. The places where I will install this is in three phase four wire system, three phase three wires systems, and monophasic. Due to this I don't know how to attach my input to the AC/DC converter. I did a research and found that using a three phase may works when you have a three phase three wire systems as I attach next.

But in this design I'm not using the neutral cable, and if I install this device in a monophasic system won't work at least I connect neutral to L1,L2 or L3. But that won't work for my design purposes. What I would like to achieve is using an universal design that doesn't matter if is 3phase 4 wire or 3phase 3 wires or monophasic. Looking forward, I found this design:

I understand that the voltage may increase over 564dc or higher, as the source says. But my AC/DC can handle it. My conclusion is that I can use the last design as follow:

Please correct me, I'm wrong.

Sources:

First design
Second design
My AC/DC Module


texts:
NOTE: This question is related to a homework project.

I’m designing a PA for the 850-880MHz band. We have quite a lot of freedom for doing that. Only two requirements are specified:

The amplifier must reach P1dB=29dBm
It must have at least 15dB gain at 1dB compression.

I expect some loss in the input and output matching networks, so to my mind, the device should reach at least P1dB = 30dBm and 16 or 17dB gain at compression. In this sense, I’ve chosen the following LDMOS device from NXP and downloaded its model for ADS.

https://www.nxp.com/products/rf/rf-power/rf-mobile-radio/3-w-cw-over-1.8-941-mhz-7.5-v-wideband-rf-power-ldmos-transistor:AFT05MS003N?tab=Documentation_Tab

I’m aware that this is a 3W device that far exceeds the project specifications, but I didn’t found a another suitable device with a nonlinear model freely available on the Internet. If you know a good source of nonlinear models for RF transistors, please let me know.

Well, I run a DC curve tracer simulation and selected the bias point so as to operate in class A or AB (VDS = 6.5V, IDS = 440mA). The IDS traces look like this:

Then, I’ve opened a design template: Design Guide→Amplifier→1 Tone Nonlinear Simulations→ Spectrum, Gain, HD, Power w/ PAE.

So far so good, I’ve got P1dB ~ 30dBm with 19dB gain at 1dB compression.

My problem is the following: I wanted to plot the loadline, so I put the time domain waveforms of IDS and VDS over the above DC traces. For my surprise, IDS takes negative values for a part of the cycle:

Then I examined the VGS waveform. I expected it would be a sinusoid since the gate is connected to a power AC source, but it isn’t. I simply can’t figure out why.

I’ve also checked out ATF511P8 from Avago. According to the datasheet, ATF511P8 should meet the specifications. Unfortunately, I discarded it because simulation shows that I need to increase the bias current far outside the maximum limits specified by the datasheet to meet P1dB=30dBm requirement. In this case, the loadline clips at IDS=0 for high drive level. Does this mean that the AFT05MS003N model is wrong?

https://www.broadcom.com/products/wireless/transistors/fet/atf-511p8

So, my questions are:

Why IDS takes negative values? Shouldn’t it be clipped to 0 instead? Is the device model still valid for the design?
Why VGS is not sinusoidal?
Does this mean that the results of the HB simulation are wrong?

Any advice will be welcome.

Thanks in advance.

EDIT
As suggested, I've examined the loadline trace of a class C design. Specifically, this is a sample design that comes with the ADS. It can be reached from Design Guide->Amplifier->PA examples by class of operation->Class C->Spectrum, Gain, ...

As expected, the loadline is clipped at the bottom whereas the loadline of the AFT05 LDMOS describes an elliptical trace that goes below IDS = 0. Excuse my ignorance on the topic, but I've noticed that the active device on this example is a GaAs FET using the Statz model. On the other hand, I didn't find details about the AFT05 model, but probably it may be MET (1). I'll try to examine the loadline of another LDMOS device.

(1) https://www.nxp.com/files-static/abstract/ldmos_models/MET_MODEL_DOCUMENT_0704.pdf


texts: How do construct a electrical resistance tomography apparatus

texts: Im interested in constructing an electrical resistive tomography setup to image underground structures. While I somewhat understand the principle, I have found limited information on design and construction. I'm looking for any information on how to construct one.


texts: Why is a Flush needed in the MSI cache coherency protocol when moving from Modified to Invalid?

texts:
While studying the MSI protocol as described in different sources such as:

https://en.wikipedia.org/w/index.php?title=MSI_protocol&oldid=941977299
http://courses.csail.mit.edu/6.888/spring13/lectures/L7-coherence.pdf

they say that when moving from Modified to Invalid due to a BusRdX (another cache wants to write to the line), that the cache must write back to memory, or a "Flush" in the Wikipedia terminology.

However, I don't understand why this is needed. Wouldn't it be more efficient instead to:

not do anything immediately
service future reads from the new Modified cache.

This new Modified cache must exist, because the only way for a cache to move from Modified to Invalid (besides eviction) is with a BusRdX, and the only thing that produces a BusRdX is another cache going to Modified after PrWr.

More verbosely, the cache of the new writing CPU must first request that line to be read from the old modified cache, and this request both invalidates the old cache, and makes the most up to date value be in the new modified cache that was written to.
only Flush on eviction, when the Modified cache is full and needs to offload something into main memory

If this approach is wrong, could anyone provide an example of how it would lead to a data loss problem? Or is there another more external reason why this Flush is needed?

This question somewhat supposes that cache-to-cache transfers are possible, which I'm not entirely sure. Here is a video that discusses that: Cache To Cache Transfers - Georgia Tech - HPCA: Part 5.


texts: Impedance matching for high speed pulse generators

texts:
I came across the following article on impedance matching for pulses which have very sharp rising and falling edges:
https://www.avtechpulse.com/appnote/techbrief12/

They claim that the output impedance of the generator (50 ohm) and the load impedance should be equal
They assume the pulsers have \$Z_{out}\$ = 50 Ohm Output Impedance

Therefore in the case of a load which is less than 50 ohm, a series resistor needed as shown below:

Similarly if the load is greater than 50 ohm, a shunt resistor can help as shown below:

I have three questions regarding this issue:

When they make matching why they only take into account the load resistor and series or shunt resistor but not the 50 ohm resistance from the coaxial cable? For example in the first example they set: \$Z_{out} = R_s + R_{load}\$ = 50 ohm. Why do they omit the coaxial cable resistance in this matching?
Why would unmatched output impedance and the equivalent load resistance cause ringing or reflections? Is there a way to describe this reason illustratively?
Is there a specific reason historically to standardize output impedance 50 ohm in general but not 10 ohm for instance?


texts: What is the function of DC offset block in an oscilloscope?


texts: Laptop AC Adapter using a higher Amp or Watt rated and effects

texts: I have a laptop AC Adapter that has a power specification of 19v 3.42A  65watt and the laptop power requirements are 60 watt. What are the likely effects of using a higher rated AC adapter, ie 19V 4.74A 90watt . My understanding is that the laptop cannot draw more current than required and even though the 4.74A AC adapter has a higher capacity, it would not effect the laptop as the laptop would only draw 3.16A as max. Can this be confirmed? Also is it physically possible for a laptop to draw more power than its specification ie can my 60 watt Laptop suddenly decide to draw 90 watts through its system and cause damage? Is there any possibility of damage to the laptop by using a higher AMP rated (same voltage) AC Adapter?


texts: I need to drive a inductive load with a triac dimmer. Circuit uses zero-voltage cross and delay for gate trigger. An additional circuit for detecting zero current cross has been added. So, what are the correct steps in order to safely control power for a highly inductive load? -> zero-volt cross, delay, trigger triac, delay, detect zero-current, trigger triac.


texts: Opamp Astable Multivibrator - initial delay

texts:
I'm trying to build a low frequency oscillator (think about 0.01Hz - 5Hz) using a TL072 as an astable multivibrator. Here's the circuit in LTspice:

And here's the simulated output:

Where does the 2.8s initial delay come from? It appeared once I raised R to 1M to decrease the frequency to suit my range. Also, where would one put a potentiometer for frequency adjustment? I also suspected using an electrolytic capacitor in this configuration would damage it as it's repetitively getting a negative voltage, so I limited C1 to 100n.


texts:
I am new to FPGAs (started with a CMOD S7 last month) and my end goal is to create a hardware accelerator (or an array of accelerators if there are enough resources, which can be used for parallelization and even more acceleration) for a real time image processing algorithm. It's not a standard algorithm so I can't just use IP cores and call it a day, but imagine convolution using randomly distributed kernels of varying sizes. I have written Python code and verified my algorithm in software and want to move into the hardware acceleration phase (using GPUs is not an option for the end product, please don't comment regarding that).
I have written some very basic verilog projects like a counter, clock divider, simple adder, etc. but now I want to start with the real project and hence need a way to debug my designs. Since I'm using an iterative design methodology, creating test benches and simulating every iteration of every module is not the best option for me and I need a way to directly read from or write to different registers.
My initial thoughts are using a MicroBlaze processor witch interfaces with a BRAM controller and uses the USB serial communication with PC to perform the read and writes but I'm not sure if that's a viable or even a good approach. I'm going to give it a shot sometime soon but please let me know if there are better approaches as I just started learning about FPGAs and don't know much.


texts: At t=0 the voltage across the Inductor will immediately jump to battery voltage. Why?

texts:
While reading transients i come to read......

"the voltage across the inductor will immediately jump to battery voltage (acting as though it were an open-circuit) and decay down to zero over time (eventually acting as though it were a short-circuit)."

Why the inductor voltage will immediately jump to battery voltage. They say that thats because of the time changing magnetic field across the inductor that will induce equal and opposite voltage in the inductor according to Lenz-Law. But then at t= 0 they claim that the current is zero in the inductor. So when the current is zero in the Inductor then how a magnetic field can be built to induce opposite voltage across the inductor.

So whats happening at t=0 ? zero current and equal and opposite volage ? Since there is zero current then what makes the inductor voltage equal to battery voltage ? If there is current at t=0 then why its never mentioned anywhere in theory or in equation ?


texts: \$2n\$ point charges on a circle at \$O\$, what's total electric field intensity \$\overline{E}\$ at \$\pm 1\mathrm{m}\$?

texts:
The problem reads is from a Schaum's Outlines of EMFT and reads:

  A total charge of \$1\mathrm{nC}\$ is equally distributed among \$2n\$ points which are placed equidistantly on a circle with \$1\mathrm{m}\$ radius centered at the origin in the \$xy\$ plane.  Find the electric field intensity on the axis of the circle at \$z = \pm 1\mathrm{m}\$.

The answer given is \$\overline{E} = 3.18 \hat{a}_z \ \mathrm{Vm^{-1}}\$.  But I keep getting \$\overline{E} = 4.5 \hat{a}_z \ \mathrm{Vm^{-1}}\$.

My method:
By symmetry of a \$2n\$-gon at the origin, the field intensities parallel to the \$xy\$ plane will cancel each other out when you add them all together, so that the intensity experienced by something at \$z = \pm 1\mathrm{m}\$ is all due to intensity along \$\hat{a}_z\$.

So far we have:

$$\overline{E} = 2n \times \dfrac{\dfrac{10^{-9}}{2n}}{4\pi\dfrac{10^{-9}}{36 \pi} (\sqrt{2})^2} \hat{a}_z = \pm 4.5 \hat{a}_z \ \mathrm{Vm^{-1}}$$

where \$\epsilon \approx 10^{-9}{36 \pi}\$ is the permittivity.

I think it may be because I'm using \$\sqrt{2}\$ for distance when I should be using \$1\$?  But that would give \$9 \ \mathrm{Vm^{-1}}\$, so I'm not sure what to do.  Thanks.


texts:
I have a 4 layer(Top-MID1-MID2-Bottom) PCB with VIA drill pairs as shown in the figure.

IS it possible to manufacture a PCB like this?


texts: Differentiation between passive and active components

texts:
While I (most of the time) know from experience what components are generally considered active or passive, I have yet to come across a satisfying definition.

Why do we divide electrical components into those two main categories at all?

Some examples:

From http://www.electricaltechnology.org/2013/06/the-main-difference-between-active-and.html

  Active: Those devices or components which produce energy in the form of Voltage or Current are called as Active Components
  Passive: Those devices or components which store or maintain Energy in the form of Voltage or Current are known as Passive Components

How does a Diode "produce" energy?

From http://www.differencebetween.com/difference-between-active-and-vs-passive-components/

  What is the difference between active and passive components?
  1. Active devices inject power to the circuit, whereas passive devices are incapable of supplying any energy
  2. Active devices are capable of providing power gain, and passive devices are incapable of providing power gain.
  3. Active devices can control the current (energy) flow within the circuit, whereas passive devices cannot control it.

What exactly means "can control current flow"? Isn't a (passive) capacitor able to control or at least influence current flow as well?

Some people argue, that it depends on the context in which the component is used to be able to consider it active or passive. This doesn't make things easier.

Especially for diodes there are so many conflicting/different arguments:

"In most cases (rectifier, Zener, etc.) a diode is, no doubt, a PASSIVE device. Only in some special cases like with a tunnel diode, when its negative resistance region is used, it can be considered as an ACTIVE device."
"it is an active device.since its impedence is positive,or v-i chara lies in 1&2 quadrants."
"Yes it is an active device since it requires an external power source, to operate it in forward or reverse bias."
"Diode is an active device, since it can be used as an waveform generator (half wave rectifier, for ex)."
"If the i-v characterisitics of the diode are in region I and III, then it is a passive device (always dissipating power). I think most diodes fall into this category."

I am pretty sure that there is no "one rule" and you always have to ask several questions about a component that must be satisfied to classify it. But what are those criteria exactly?


texts:
I want to build a simple measurement circuit for indicating the load on a little 12V pump. Assuming that the pump draws 200 to 2000mA depending on the load, how can I connect lets say 5 Red LEDs so that they are turned on in  400mA steps.
To be more precise:
For 0mA no LED is on.
For 400mA one LED is on.
For 800mA two LED are on.
Etc.

The pump is directly connected to the power source.
Is there a way to do this using simple parts (resistors and LEDs)? If not how can it be done?

I want to build the circuit from scratch to get a better understanding of electronics.

Regards


texts: Ethernet phy connection: grounding between chassis, connector and IO

texts:
The phy chip I'm using has a evaluation board which grounds the chassis, connector and signal gnd points in the following way:

However, I don't really understand why the MCTx connections are connected through a resistor and cap to GND. I understand the ground bit - they are grounded to bias the center of the transformer, but don't understand the R and C between the MCTx and ENET_GND - if the unit (or cable plugged into the phy) is struck by lightning, then how is the R and C going to protect the rest of the circuitry?

With regards to the isolation between signal gnd and ethernet gnd (C13, 14, 16 and FB14) I came across this thread (Should chassis ground be attached to digital ground?) and am not too sure if it applies here (are chassis and ethernet ground the same thing?)

Is isolating signal and ethernet gnd in the manner shown above is good practise?, and if it is, what determines the values of the components to be used? Is it necessary for isolation between ethernet gnd and signal gnd to also be lightning proof?


texts: How to charge bootstrap capacitor to achieve 100% duty cycle

texts:
To be more specific, the IR2110 uses a diode and a capacitor for bootstrapping. It's not allowed to use 100% duty cycle on the high side MOSFET. How to design the circuit to charge the bootstrap capacitor and regulate its voltage (\$V_b\$,\$V_s\$) to near \$V_{cc}\$.

For more information.
I planned to use it with a IRF540 N-FET and \$V_{cc} = 12V\$


texts: How do I determine blocking capacitor and bias resistor values for an Electret Microphone?

texts:
How in general does one select blocking capacitors and load resistors for an electret mic?  Can the effect of incorrect values be observed on a common scope or are the voltages just too small?

Why? I've inherited a design which is not producing a high enough recording volume.  The basic setup is:

In this particular case the given design uses R1=2.2k, C1=10uF, C2=1nF the power supply is actually 2.2-2.6V.  The blocking capacitor is specified as type MLCC.

The AK4951EG audio amplifier IC has a specified input impedance of 20-40k ohm, and adjustable gain from 0-30dB.  The microphone data sheet is sparse, and mostly in Chinese:

I see also Electret microphone: selecting a bias resistor


texts: I have multiple piezo sensors acting as vibration sensors. I am using a PIC microcontroller that only has 2 ADC. I want the circuit to function in such a way that if any of the sensors are hit and generate a response above a certain threshold then the PIC will flash a LED. I don't want to use a multiplexor for timing reasons and want to use just one ADC. Is there a component that will help me?


texts: How does a HCF4051BE multiplexer work, at a very simple level?

texts:
I'm a totally noob, so please, take this in consideration when replying :)

I want to understand how this multiplexer works. I tried to Google it, but all the answers was too advanced for me.

I mean, whats each pin is for? What happens when I send a sign to pin 'X'? What should I do to use it as a mux (or demux)?


texts:
I'm currently researching on MPPT (Maximum Power Point Tracking) and will do some programming into arduino using this flowchart but right now i'm struck on this as I do not understand what is \$\textrm{PV_P} (n)\$ and \$\textrm{PV_P}(n-1)\$.

I have no idea what is the \$n\$ despite searching online for all sort of explainations, most of the answer I found is them explaining about the terms etc.
Appreciate any efforts of letting me know about the meaning for the \$n\$ and briefly about the flowchart.


texts: How is it possible to feed the output signal back to input using a TRRS connector

texts:
I want to be able to "play" the output signal back to the device (in my case an XPERIA X10 which i think uses a standard TRRS plug) so that everything that is output by the device comes back to it. Would it be possible to simply loop this cable?

Apologies for my ignorance - i really have no clue about even simplest electronics.

--oleg


texts: Decision on connecting Earth Ground to one of Two GND pins

texts:
I'm planning to design a board that is suitable for industry so EMC is so important. I have decided to use two separate power supplies(+5v and +24v) to Isolate the board from outside world. Optocouplers have been used to connect these two areas. I don't want to connect these two GND(power supply) together and I want to keep them separated. About the earth ground I read lots of articles that says it is better to connect the GND in PCB to the Earth Ground(for metal chassis). I wounder to Know if I'm doing right and having two separate GND for designing PCB of the board which one of these should be connect to the Chassis ?
and How about the other one !
I would appreciate if you give me some good references to read.
TNX


texts: Why there is voltage differences in this question and how can I add up resistors to complete voltage?

texts:
Can you just explain to me the logic of this question because I am a bit confused here.
Why do we have a 120 volt and 30-volt value? My take out is this: there is a current flowing through 120-ohm resistor but the voltage across the resistor is 30 volt. Should I put another resistor to complete 120 volt? I tried to do it like that and parted 1A current like 0.25A and 0.75A but I got nowhere with this. And it doesn't make sense because I feel like I should use the 1A current to make Norton circuit. I am not trying to make you solve this question entirely but if you can help me out to understand this question a bit I would really appreciate it.


texts: Can a MOSFET be on if there is no current flowing through it?

texts:
I am reading about hysteresis comparator here and wondering if a MOSFET can be on if \$V_{gs}\$ is larger than threshold voltage but there is no current flow through it (\$V_{ds}\$ is zero),
As you can see in the picture, because M2 is off, there is no current flowing through M6. However, the slide says that M6 is on (active). So could you comment about this?


texts: 'Stiffening' capacitor/s for DIY flash battery pack?

texts:
I'm planning to build a DIY battery pack for one of my camera flashes that involves basically wiring a bigger external battery to the battery leads in the flash. Admittedly I don't know much about electronics but keep my feet just oh-so wet in it.

The main goal for doing this is actually to improve recycle times of the flash with the added benefit of longevity from the battery.

Question #1 is: Whether or not there would be any benefit to adding a capacitor or two to provide a limited rapid-charge for a quicker, subsequent re-charge after the flash goes off the first time.

My rationale is: often the flow of taking photos involves a flash or two; or three; change spots/framing/talk to subject (which by then the capacitor/s might be recharged to supply the benefit again)

Question #2 is: Is there a formal word/phrase for what this process (a capacitor used for rapid discharge in tandem with a battery) is so I can do further research for academic purposes.

More details:
The battery supply is 6V - there's a variance on how much the flash is willing to draw based on the supply (4AA's vs. the bigger battery mentioned in my links); I don't know what, or if there are limitations on what kind of current the flash can draw (hence if it can benefit from caps). There's an external AC adapter that supplies 200V@4mA for the flash.


texts:
Building a simple VFD clock with 4x IV-22 tubes. The heaters run at 1 to 1.32v @ 100mA each.
Whats the best way to supply power to the heaters?

All the heaters need to be in parallel so that their potential is the same relative to the grids and segments.

Thats ~1.3v @ 400mA. for 5V supply a resistor would need to dissapate 1/2W. That seems wasteful.

Is it possible to use the MCU to generate a PWM signal to drive the heaters directly? Then how does the current get limited (is P now 2W = 5v * 400mA?) The heater in VFD tubes is both a heater and a cathode, it has to be hot and at 1v potential to emit electrons, right, but not too hot to limit its life?

Maybe there is a way to generate AC waveform to eliminate luminance slant of segments on one side?

Also, as a side question, while I have attracted the attention of VFD knowledgeable people: For internally non-multiplexed tubes such as IV-22 what is the purpose of the grid? When would you ever want to keep it low on a single digit tube? Am I OK just wiring all the grids together into VBB (the 30V supply)?

Update: Thanks for the comments. To clarify further I will be powering this from a low voltage PSU, 12 or 9V DC so I won't have a transformer to tap from. Any voltages higher than supply will be made using Boost DC converters.


texts: Frame Errors (Character Stretching) of CP2102N

texts:
When I send a data stream from my PC to a CP2102 USB-to-Serial Bridge, the data coming out of the RS232 side is sometimes corrupted. The receiving micro (an ATmega2560) reports frame errors when this happens.

I send a command of 30 characters every 180ms. for every 10000 commands there are around 15 to 30 failures.

I use 9600.8N1, so a start bit plus 8 data bits should take 0.9375ms. Flow control is set to None.

It is always the first byte and sometimes (1 in 20) the second byte that is corrupted. I've captured the data on an oscilloscope and measured the byte times (beginning of start bit to beginning of first stop bit).

If I have corrupted data, the time is around 1.000ms. Good data takes between 940us and 960us.

It is always the last few data bits (i.e. the highest bits) and the stop bit that is the problem.

See image below for an example of the second byte being corrupted:

The character between the vertical cursor lines should be a 'P', but it takes 1.000ms and is received as 0xd0 instead of 0x50. The byte before it is a '*' (0x2a) and is fine, it takes 0.940us.

What could cause these frame errors?


texts: How are these RC values calculated in this buck converter?

texts:
Buck converter: LTC3824

The datasheet says:

  VC (Pin 4): The Output of the voltage error amplifier gm and the
  control signal of the current mode PWM control loop. Switching starts
  at 0.7V, and higher VC corresponds to higher inductor current. When VC
  is pulled below 25mV, the LTC3824 goes into micropower shutdown.

I can't find any values in the datasheet to calculate the R1 and C1 values. How does the Vc value change with inductor current? The inductor current goes to the output, not to ground...


texts: Atmel AT90USBKEY2 delay wrong before dropping power

texts:
When I program my AT90USBKEY2 with dfu-programmer, the delays are wrong until I restart the board by unplugging it.

#include <avr/io.h>
#include <util/delay.h>

int main(void) {
  DDRD = 0xF0;
  while(1) {
    PORTD |= 0xF0;
    _delay_ms(100);
    PORTD &= 0x0F;
    _delay_ms(100);
  }
}

A simple program. F_CPU is defined in the makefile.

Makefile I am not proud of does these steps:

avr-gcc -Wall -Os -DF_CPU=1000000 -mmcu=at90usb1287 -c blink.c -o blink.o
avr-gcc -Wall -Os -DF_CPU=1000000 -mmcu=at90usb1287 -o blink.elf blink.o
avr-objcopy -j .text -j .data -O ihex blink.elf blink.hex
dfu-programmer at90usb1287 erase
dfu-programmer at90usb1287 flash blink.hex
dfu-programmer at90usb1287 reset

Reading pin 6 of port D shows this:

15.6 ms high, 63.2 low.

After bouncing power, and any time it's started after that

100ms high and low, the correct timing.

I also tried a pin on port A that isn't tied to an onboard LED, same results.

avrdude: safemode: Fuses OK (E:F3, H:99, L:5E)

AVR Fuse Calculator

Am I doing something clearly wrong, or is it just accepted that I have to unplug the board after programming?

It seems like this might just be an issue where the reset button/dfu-programmer reset doesn't reset it properly.
I don't know how that works yet, will update when I learn more.

Though bouncing the thing after programming isn't the worst.


texts:
I have a lot of (new) LED light strips from a job I was on. These light strips were in 2x4 fixtures. As a project I would like to use these as undercabinet lights. But the CC driver that comes with the 2x4 seems to be insufficient.

I had to modify the length of most of them to fit under each cabinet. This was done successfully. I checked if my modification was good by using the old CC driver.

The problem: Once I got all the lights to the length I needed and plugged them all together (think LED ribbon) The old driver will not light the whole string. A problem I thought might happen.

The main question: What size CC driver is required?

The facts:
CC driver in donor light. Osram optotronic OTi 30/120-277/1ao dim l. this driver has dimming capabilities. But I don't need dimming. Pout=30W, Vout=10-55
Iout=350-1050mA. Factory setting output current is set to 540mA.

LED's in donor lights. Unknown. (4) strips of 40 led's 3500k. Each LED measures about 25mmx45mm I could not find any typ. LED's online with these dimensions. I asked the factory for the data sheet but they were unresponsive.

My finished quantity of LED's = 320

How do I size a new driver based on these facts?
Thanks


texts:
In my simulation I require Earth on my chassis so that filter could be simulated. But I am not getting how to make an Earth in LTspice.

Please note:  This question is regarding ' LTspice '  protective earth grounding and not on filtering. I need to distinguish in between GND (circuit common ) and PE(symbol)  to make simulations.


texts:
I have a square wave (1st line), I want to skip every odd impulse, and output every even one without change, as shown in the second line.

Is this different from frequency division? What is the proper name for such circuit? Can it be done with double d-flops, like 4013?


texts: Determining how much current I can actually run through my Cat6 24AWG Cables in my confirguration?

texts:
I want to use a CAT6 (24AWG) RJ45 cable to carry a total of 2A at 48V. As per the AWG Chart, I see that the Maximum amps for power transmission is 0.577A but the Maximum amps for chassis wiring is 3.5A. I am not going to be using this cable in a bundle and it will be in lengths up to 10ft.

Am I OK here? WHich number do I follow: Maximum amps for chassis wiring or Maximum amps for power transmission?

If this is a bad idea, are there other DC cables I can use for a 10ft range carrying 48V and 2A?


texts: Sending flyback current to another inductor using crossed diodes

texts:
So, here is the context. We have two electromagnets (modeled as R1 and L1, and R2 and L2), their state is dictated by a microcontroller which sends PWM to Q1 and Q2. The signal sent to Q1 and Q2 is a square wave around 80 Hz. The two square waves have the same period and amplitude, but an 180 deg. phase shift, so when Q1 is open, Q2 is closed.

Here is the idea: when the switch to an inductor is suddenly opened, a flyback potential is created across the inductor. A diode pointing to the other side of the inductor is usually added to avoid arcing.

My idea is that I apply this flyback potential to the other inductor, some of the energy stored in inductor 1 as moving current will be transferred to inductor 2 through the diode. I have an intuition that since the current through inductor 2 can't change instantly, this setup would still give me sparks though.

The question is, would this increase the efficiency of the system compared to connecting each diode to the corresponding inductor? Or am I misunderstanding flyback voltage to begin with? If so, what would be the corrected way to "recycle" the energy stored in the first inductor?


texts: Parameter tolerance estimation with non-pure ratios

texts:
I am trying to estimate the exact tolerance of a simple circuit, consisting of an op-amp based, inverting comparator with hysteresis.

This is the schematic (electronic-tutorials.ws)

For which I have a given Vref derived from a buffered voltage divider powered from the same +Vcc of the op-amp and all the resistors are +-1% of tolerance. Now, I want to calculate the tolerances on the threshold voltages.

Let's say the voltage divider is made by Rup and Rdown, my Vref is:
$$ V_{ref} = V_{cc} * \frac{R_{down}}{R_{up}+R_{down}} $$

The positive and negative threshold will be:

$$ V_{highToLow} = V_{oh}*\frac{R_1}{R_1+R_2} + V_{ref}*\frac{R_2}{R_1+R_2} $$
$$ V_{LowToHigh} = V_{ref}*\frac{R_2}{R_1+R_2} $$

Assuming that the equations are correct, I thought to use the worst cases. For example, taking the Vref at its higher value, with R2 at higher value and R1 at lower one, so to increase the ratio and the multiplication. Viceversa when estimating the lower bound of the overall equation I will do the same with the lower values or the combination that lowers the ratios. The strange (or cool?) thing is that I have two ratios, one with R1 on the top and the other with R2, and they seems to compensate a bit each other.

Assuming that the flow until now is correct, now the last (or maybe the first) thing to do is how to estimate the Voh. I think to add in this estimation, also the 1% of the Vcc (which is nominal 5V). So, trying to explain better, from the following picture:

The Voh would be ((4.965-4.875)/2)+4.875 = 4.92V with tolerance of [+-%]: $$\frac{\frac{4.965-4.875}{2}}{4.92}*100 = 0.9$$

But since the power supply is already at 1% of tolerance, I would consider a total error on the output saturation voltage of around +-(0.9+1) = +-1.9 => +- 2%.

And in this case, just reiterate what I have already done with the previous equations, but also considering the worst case of the Voh.

I'd like to have an opinion on this approach and if there are some things that I can neglect.


texts: Does proximity matter when hooking up batteries?

texts: I'm planning to put two batteries in both feet of a two-legged robot and then creating a serial connection of the two sets using wires up to the hips. My question is, does this effect the power source in any way? Is it important to have the 4 batteries serially connected as close as possible?


texts:
Why do a mobile phone charger (without mobile phone attached to it) constantly hums when kept plugged into A.C. outlet and the moment mobile phone is plugged into charger, humming goes.

Why so ?


texts: Logic Level Converter, Arduino and Cellphone

texts:
I am trying to interface a 6150 Nokia cellphone with an Arduino Duemilanove board, as some have already done through the FBUS protocol (see here for example).

The FBUS protocol uses 2.8V logic, so I bought Sparkfun's logic level converter to interface with the 5V from the Arduino, right ?

They say:

  The level converter is very easy to
  use. The board needs to be powered
  from the two voltages sources (high
  voltage and low voltage) that your
  system is using. High voltage (5V for
  example) to the 'HV' pin, low voltage
  (2.8V for example) to 'LV', and ground
  from the system to the 'GND' pin.

Thus

HV  <->  Arduino 5V
GND <->  Arduino GND

LV  <->  ??
GND <->  ??

TXI <->  Phone TX    (Low Voltage)
RXO <->  Phone RX    (Low Voltage)
TXO <->  Arduino RX  (High Voltage)
RXI <->  Arduino TX  (High Voltage)

The problem I have is with the low voltage source: there is no power output on the phone.

Can I power the converter LV/GND from another 2.8V source ? Would it be ok with the Arduino 3.3V source ?


texts:
Question:
If two, one-inch magnets with the same “pull” strength are magnetically connected to each other, do the combined magnetic lines of force extend twice as far as if only one magnet’s line of force was measured?


texts: What is this quadruple triangle logic symbol?

texts:
Or maybe it is two mirrored triangles... and an 'invertor' dot?

This is from a diagram in the ATMega328P datasheet, page 76 bottom left.

Note that this question shows a similar device. In that question however the symbols only have two ports and no dot/circle.


texts:
I have a problem with circuit, because I don't know how to design a voltage limiter.
I connect to the input (In) sensor that generates signals with range of 240mV to 940mV. Next, The signal output with sensor is amplified voltage by LM358 operational amplifier.

The maximum voltage output can be 1000mV. When sensor generated 940mV signal, I have output voltage of 1060mV.
How do I limit the output voltage to maximum 1000mV?


texts: Need help understanding RF radio parameters

texts:
I am experimenting with the SPSGRF-915 RF transceiver, particularly with the different center frequencies.
My question mainly revolves around the situation where multiple devices can transmit at the exact same time, and I need to make it possible for the respective receivers to decode the signals properly.
I plan to achieve this by modifying the center frequencies of each transmitter and receiver setup/pair so that each setup/pair can decode these signals properly.
If I were to configure transmitter A (TxA) and receiver A (RxA) to:

Center Frequency: 913MHz
Channel Space: 100kHz
Bandwidth: 160kHz

and transmitter B (TxB) and receiver B (RxB) to:

Center Frequency: 915MHz
Channel Space: 100kHz
Bandwidth: 160kHz

Would it be correct that these two setups should not interfere with each other because of the different frequencies and the bandwidth?
In the example above, since the bandwidth is 160kHz, would that mean that TxA would most likely occupy the 912.92 MHz to 913.08 MHz range, and this would not interfere with TxB because TxB would most likely occupy the 914.92MHz to 915.08MHz range?
What are other scenarios that could cause the setup above to fail?
Can a high transmit power (say +15dBm) on either transmitter cause the other setup to fail?


texts: Current transformer with additional multi-turn winding for test purposes

texts:
Some explanations for the circuit below:

This is a CT with 1000 turns secondary. It has high sensitivity
down to mA levels so that's why I put an amplifier given that the
burden is small (35 ohms).
The CT has 1000 additional turns for the test winding. So the ratio
is 1:1 between secondary and test winding.
The reference voltage IC is configured to give Vcc/2 = 1.65V which
is the DC shift.
I'm planning to use a square wave from the micro followed by a high pass filter to feed the test winding. It just need a small current during a quick moment. The switch is to open the winding when no testing. The general purpose of the test winding is, of course, to test the system, so I don't necessarily need to put current in the primary.

My question is: Do I need to connect the test winding to the DC shift like the sense winding? Or do I need to connect it to ground instead?


texts:
Do electronic components have an expiration date?

How long does it take to components to go bad if we store them at room (normal) temperature and humidity?

What components go bad sooner? (resistor, capacitor, transistor, ...)

What are the best conditions for components storage?

Conditions of maintenance maybe are written in the datasheet, but is expiration date coming from the datasheet too?


texts: Finding the Voltage drop across capacitors

texts:
The capacitance on the square with CB, CC, and CD will be:
$$C_{Eq}=C_C+[1/C_B+1/C_D]^{-1}=246.875$$

I used the equation:
$$V_{Eq}=V_A*[C_A/(C_A+C_{Eq})]$$
$$V_C=V_{Eq}$$
$$V_A+V_C=119V$$ so that I could get the value for V_Eq, which came out to 29.9371V; I plugged this value in to the first equation to get V_A and the sum of the two is 119V. This is not accepted as a correct answer, though. Is there something I am doing wrong?


texts: intrinsically matched Schottky diodes (sharing common substrate)?

texts:
I'm looking for a pair of Schottky diodes on a single die: one to use as a non-linear element and one to measure the temperature.  All of the dual Schottky's I've found so far are on separate dice, bonded in a single package.  (I presume this is to provide better isolation between the two.)

I know I can get dual NPN transistors and use them in a diode configuration, but I need the low Vf of a Schottky.

Is there a family of devices -- perhaps not Schottkys -- that would serve the same purpose?


texts: real time online push button based counting system

texts:
I am doing this project:

I have 4 inputs. These are push buttons, connected to a microcontroller.

Each time a push button is pressed, say for example pushbutton_1 is pressed, the press of a switch button should be recognised as a HIGH.

In its normal unpressed state it should be recognised as a LOW.

Then using serial communication i should transfer it to a computer.

Along with this, i need to implement a count for each button.

Each time a push button is pressed, the count that is assigned to that push button,  should increment by 1.

The data arriving through serial communication should be transferred to an excel sheet/database.

The excel sheet/database should display a count for each pushbutton.

I have 4 important question areas:

Which microcontroller should i use? (I have experience with arduino development platform)
How do i implement the transfer of data from microcontroller to computer via serial communication?
Afterwards, how do i transfer the arriving data to MS excel/database?
How do i run implement the system in realtime?

Please suggest me the best possible way to implement this system.


texts:
Given the following circuit:

simulate this circuit – Schematic created using CircuitLab

I'm trying to find the equivalent capacitor assuming that the capacitors are already charged. I'm aware that C1 and C2 are in parallel, therefore they must have the same voltage. What I'm not too sure about is if I can just add both of their capacitance since the resistance R is only connected to C2, but at the same time C2 instantly affects C1 keeping the voltages equal.

Just to clarify, by equivalent capacitor I'm referring to this:

simulate this circuit

Thanks


texts: 4-layer board in PCB Editor - do I need custom vias?

texts: I routed a 4-layer board using the default via. When I put in my ground and VCC planes the vias had no clearance. How do I fix it? Do I have to make my own vias? (I thought it was automatic). Next time I will draw the inner ground and VCC planes before I route. Geeezzz.


texts: What is the best way to remove the non-rejected portion of a common-mode voltage and any bias voltages from a differential voltage measurement?

texts:
I am using a high-common mode differential amplifier (AD629) to measure several DC 10 to 15 voltages stacked together.  Since the AD629 is not the cheapest amplifier in the world (though not as expensive as an instrumentation amplifier), I want to multiplex one to measure every signal and save power, probably with a solid-state relay (SSR) since they have a relatively long lifetime (number of cycles) relative to electro-mechanical relays.  Any mismatch in the SSRs will reduce the common-mode rejection ratio.  Since this is unavoidable, so I would like to calibrate the unrejected portion out, as well as any other bia voltages that may enter the signal later down the circuit path before it is sampled.

What is the best way to do this?  My guess is to use a high precision voltage reference on the input.  If the reference is not connected to the common-mode voltage, it only calibrates to some of the biases, but not anything due to the common-mode voltage.  Would it be possible to connect the reference circuit's ground to the common-mode voltage as a virtual ground?

Then a new problem is introduced, which is how to power the reference using the common-mode voltage as a virtual ground?  I could use a voltage regulator with the common-mode voltage as ground and the top of the signal as power, but I do not want an input capacitance to the regulator impacting the signal.  Besides, isn't drawing unnecessary power from the signal of interest frowned upon, even if it is essentially a DC supply voltage?


texts:
I'm not sure if this is the right place to ask this kind of question(mine seems practical as opposed to academic) but here it goes.

The embedded board I am using(Jetson TX1) can be powered using:

4S LiPO(4 cell / 14.8V nominal / 16.8V charged) with 1-2A (or 15W) of
continuous current
    or
3S LiPO (11.1V nominal / 12.6 charged / 9V    discharged) with 1-2A
(or 15W) of continuous current

(from https://devtalk.nvidia.com/default/topic/914529/jetson-tx1/battery-for-jetson-tx1/1)

I'm trying to mount Jetson TX1 on my quadrocopter which has XT30/XT60 ports with the following spec:

Output Voltage: 20 - 26.1 V
Max Continuous Output Current: 10 A

(from http://wiki.dji.com/en/index.php/Matrice_100-Reserved_Ports_Description)

Now I'm trying to buy a DC-DC step down converter and I'm currently looking at DROK 200143 DC-DC Buck Converter 3.5-30V to 0.8-29V 10A Step-down Volt Adjustable Output Regulator Module Power Supply which has

3.5-30V input
0.8-29V output output
10A Max output current

My concern is the input current. The output current only needs to be 2A but it should take 10A input current.

Is the max input current same as the max output current?


texts: Is noise a problem when using a logic level shifter?

texts:
Good morning everyone,

I'm building a device that uses several bidirectional logic level translators to interface 3.3V microcontroller to 5V, 2.5V and 1.8V sensors (via I2C lines).

But I wonder if level shifters produce any significant noise; this is interesting for me due to extensive use of MOSFETs, internal current sources and one-shot pulse devices in level shifters (please see MAX14548E as an example).

I'm asking because I haven't seen any mention of noise characteristics in specs of any of LLT devices.

Is noise a problem with level shifting, or should I put my worries to rest?

Thank you.


texts: Why Bluetooth audio works at so high latency?

texts: Referring to this, the lowest latencies achieved in Bluetooth audio streaming are around 30-40ms. But given the fact that Bluetooth physical layer data rate is of around 2-3 Mbps and today's Bluetooth chipsets support sufficiently high processing power, the source to playback device latencies should be much lower (e.g. within 10ms or so, even by keeping substantial buffering). The audio codecs like AptX claim to add latency by 1.8ms only. So what causes so high latency in Bluetooth audio streaming using Bluetooth A2DP profile?


texts: AC Induction Motor Constant Speed Control without Tachometer

texts:
I want to run the AC induction Motor at a constant speed with LOAD also without Load. So I am controlling motor speed by TRIAC. I can control the motor speed, but my problem is:- I don't have a tachometer in my circuit. If the tachometer is available, so I can get the feedback from the Motor, then I can control the speed of the motor at a constant level. But my question is without tachometer is there any other technique to run the motor at a constant speed - with & without load. Please help me to solve this problem.

For an Example:
I want to run the Washing Machine - Wash motor, in the Wash motor there is no RPM feedback. Only the Supply line three wires are present in the motor. I want to run the motor at the same RPM whatever given User Load. In this scenario what is the solution to run the motor at same speed with different load?


texts: Please someone explains the main parameters used in the k_linear part in pspice , more specifically what is L1 , L2 , L3 and designators in its parameters?


texts: Transistor buck converter system current increase

texts:
I am putting together a small system to control an externally powered circuit from my RPi to drive a LED.

The circuit can be separated into 2 parts:

One side is used to power the Pi. I go from the battery (12V, 6A)  to a buck converter that I use to drop the voltage to 5V. This seems to work fine. I was able to set current limitation and it would be effective.
The second part is used to control the LED. Here I go from the battery to a first MOSFET controller ( MOSFET Tube Driver Module For Arduino SCM ARM Raspberry Pi with a IRF520 )  plugged to the ground on the Pi and to GPIO16. The circuit continues then to a buck converter that limits the voltage to 3V and that should normally limit the current to 750mA. It goes then to a second MOSFET controller that is used to control the LED status. This MOSFET board is connected to the ground on the Pi and to GPIO21.

Now my problem is with the 2nd system. If instead of a LED I attach a multimeter and try to read the current I get the following:

MOSFET 1 and 2 are off --> current 0mA
MOSFET 1 on, 2 off --> current 0mA
MOSFET 2 on, 1 off --> current 0mA
MOSFET 1 and 2 on --> the current starts low (0.25A) and continuously rises. After 1 min it is around 0.5A and keeps going. I am new to electronics so I didn't know if it could damage the Pi. Therefore I did not leave it on to see where is stops climbing.

If I switch off the 2 MOSFETS for a while and then switch on again, the current values has dropped a bit and rises again.

My questions are:

What could potentially limit my current in the 2nd system at 250mA when I start up?
This current increase looks like something is charging somewhere. Could some part of the current go into the Pi? Or is my reading wrong by closing the system with my multimeter?
How can I prevent this unwanted behavior and have the wished 750mA right away when I switch on the 2 mosfets

Thank you in advance


texts: Why do high-voltage transformers need oil?

texts:
Someone told me that high-voltage transformers need oil because it prevents arcing.  However, in terms of dielectric breakdown, isn't air the strongest?

I remember from classes in college that as the dielectric constant increases, the breakdown voltage decreases.  Is this correct?


texts: Relationship between junction area and voltage in forward biasing

texts:
What is the relationship between junction area and voltage in forward biasing? My book said that the voltage to establish forward biasing increases with decreasing of junction area. Why?

EDIT: The question is about BJT which has two junctions, base-collector junction is greater than base-emitter junction. In saturation region the two junctions are forward biased, but

$$V_{CE}=V_{BE}-V_{BC}=0.2V$$

thus the larger junction area has a lower voltage in forward biasing.


texts: Shift registers, understanding parallel-in serial-out

texts:
I have the 74hc597 parallel-in serial-out (PISO) shift register. The datasheet can be found here.  I have a general idea about how serial-in shift registers (SIPO) work, but I'm having trouble understanding PISO and what a couple of pins do or how they work. I have a few (very basic) questions about this table in particular:

Questions:

1) The shift register is clearly described as a 'parallel-in serial-out' (PISO) shift register, so why is there a 'serial data input' pin?

2) Which clock input (shift register or storage register) is used for controlling the serial output? I am guessing 'shift register clock input' is used because you are shifting out one bit at a time from the parallel data stored, right?

3) What is 'parallel load' input? Is this used for reading all the parallel inputs? Is it some type of latch pin, similar to SIPO shift registers?

Here is my summary of how I think PISO shift registers work, please tell me if it's wrong:

-When the 'parallel load input' is set to LOW, all the inputs enter the register

-Then when the 'storage register clock' pulses, the data is saved into the storage
register.

-Then during each 'shift register clock' pulse, the bits are outputted one by one

Thanks for your help.


texts: LAN9512 differential wire routing on PCB

texts:
Using the Saturn PCB Tool (V7.05 - calculation method IPC-2152 - Etch Factor 1:1), in order to achieve a 90 ohm differential line with a single line impedance equal to 50 ohm for a design based on the LAN9512 chip, I've found these parameters:

conductor width : 0.15 mm
conductor spacing: 0.25 mm
conductor height : 0.10 mm

This set gives me 91.2 ohm (differential) and 47.7 (Zo) with a FR-4 STD substrate permittivity equal to 4.6 (changing between 4.3 up to 4.9 don't cause trouble and the value stay around the prescribed nominal value in a ±5%).

This track values are compatible with the LAN9512 land pattern width equal to 0.28 mm and also give some free into the board routing process.

As a consequence, this will give a very thin PCB. Does anyone know if there is a way to achieve the goal (to work with a LAN9512 chip) with track width around 0.15-0.2 mm and a final PCB (4 layers) thickness of 1.6 mm nominal?

Thanks.


texts: Can a pogo pin spring cause an inductive spike?

texts:
I have an IO pin on a LM3S1751 microcontroller tied to a pogo pin which shunts to ground when engaged. There is a 100k external pullup on the pin. The pin sees 3.3V when not engaged and 0V when engaged. It's really very straight forward.

Now, I've shipped approximately 100 units and recently received 4 returns because this pin always reads low/zero. I have verified that the voltage does indeed swing from 0V to 3.3V at the microcontroller. I've also verified that the registers to configure the pin as an input are set correctly using the debugger. Everything looks correct. The only way I can get the pin to read high is if I set the bit which controls the internal pullup.

Since I believe (and have had others confirm) the pin is properly configured, I am now looking at scenarios in which the pin may have been damaged. This got me wondering if exercising the pogo pin could generate a spike which may have damaged the port pin. Inside the pogo pin is a spring, which electrically looks like an inductor. However, the part of the pin that moves and the part which is static are likely always in contact which represents a parallel path. The port pin and pogo pin are separated by roughly 2 inches of 7 mil trace... not excessive.

And let's say it did somehow generate a spike that damaged the port pin. What is a likely failure mode? And would it not affect more than just the single pin on the port?


texts:
I'm building a PIC-based text editing 'laptop'. I have an SD card connected to the PIC and am using a keyboard and an LCD screen.

My problem is that I want to edit real big files like for example over 300kB. Now I have some options for the memory control:

Store the whole file in extern RAM. Inserting new characters in the middle of the file will result in replacing every byte to one address higher. Disadvantage: speed, since replacing 300,000 bytes will take some time.
Store bytes address-based in extern RAM. Separate the RAM into two halves: one contains the addresses for the bytes in the other. Inserting characters would mean adding bytes to the end of the second half, and adding the addresses to the end of the file to the first half. Disadvantage: not so efficient RAM usage, would take a long time to save the file in the end since all the addresses are spread through the RAM.
Something with a gap buffer in extern RAM, so that would mean leaving NUL characters on the SD card available for future insertions. Disadvantage: not so efficient SD card usage, however this is not a problem. Also: hard to code(?).

My question: I'm thinking about the gap buffer to implement, however I might miss something. Is a gap buffer the best way to do this?


texts:
I'd like to use a Tripp Lite PR40 as a backup 12V UPS by connecting it to a battery before a couple motors in parallel. The battery is 125AH deep cycle AGM. Can I do this?

The manual says that the power supply can be used to charge a battery but that a 40A fuse should be in between to keep it from back feeding and frying the power supply. I think I can do this with a diode but I'm not aware of any 12V 40 amp diodes. Any input on the type of diode and do I need a circuit board of some sort to wire it in?

If not, are there smaller diodes like 20A I could use?


texts: How do I check a BJT transistor if it is still functional?

texts:
Is there a simple method to do a sanity check on a bipolar junction transistor whether it is still functional or defective?

simulate this circuit – Schematic created using CircuitLab

Say for example I have a circuit that used to function, and I suspect the transistor (NPN, PNP). How would I go forward to make sure the transistor is defective or how can I reasonably be sure it isn't? Do I need the datasheet for the part?


texts:
I am using a INA125P to amplify the signal from a beam load cell - and I have noticed a frequent ramp in my INA125P output signal, of about 100mV every 200uS.

EDIT: My gain is roughly 800x.

I have scoped various locations in the circuit, including the cell excitation, the cell output (unamplified) and the general circuit supply, and cannot see the same pattern anywhere - suggesting this is being introduced inside of the INA125P.
I have tested a few INA125P chips to rule out the damage - all are identical.

EDIT:
Here is the Circuit.io (excuse some of the nonsensical layout... circuits.io layout is an exercise in futility).
Note: I have added in the low pass filters... I haven't tried the actual circuit yet... this weekend most likely.

Thanks


texts: Choosing the appropriate power plug for a given fan motor

texts:
In a fan motor I have, the written specifications are as follow :

"dual power: 110/230v 50/60Hz 22/20w".

I would like to power the motor directly, without electronic parts between any 220V wall power socket and the motor ( only a standard power plug unit).
To select the appropriate 220v power plug I need to know the amperage.

Using the formula A=w(20)/V(230), I get A=0.0869

Are my calculations correct ?
If they are, then I am lost. What kind of power plug could I use to get such a low amperage?


texts: Can someone please explain this attenuation setup?

texts:
This is a part of an Agilent signal generator output attenuator. These are 4 or 5 of these stages with the resistor setup as shown, different values at each stage to set different attenuation levels and these can be combined using relays to create several combinations. For example one stage is -2dB, another stage is -4dB but they can be both inserted inline creating (surprise) -6dB attenuation.

What I don't really get is the resistor arrangement. What's up with the values and why the network instead of 3 simple resistors?


texts: Why Ring Buffer is preffered for asynchronous communication?

texts:
Ring buffers are the go to choice by most veteran embedded programmers for asynchronous communications.
Assume that data arrives over UART from only a single source and only when a msg is asked for(Master->Slave,Slave->Master), since codes are sequential in nature, we can just implement an ordinary array(max size of data received) to hold the received data.
Like so:

#define MAX_SIZE 8
U8 RxBuff[MAX_SIZE]

Once data has been processed and replied,the master and slave can reset the RxBuff.There is no need for a Ring Buffer.

But this got me thinking,do Ring Buffers offer the advantage of a longer SRAM life? I have read that memories like Flash,Ram have limited write cycles but infinite read cycles.
By implementing a Ring Buffer that circles around RAM locations every time data arrives,does such an implementation, by reducing the write cycles for constant memory locations of the RxBuff everytime data is received,offer improved memory life?

Or are there other reasons why Ring Buffers are preferred?


texts:
I am involved in the design of a system composed of:

multiple asynchronous motors,
each equipped with separate drive,
all acting in parallel on a load,
via a common rack and pinion transmission.

As the loads on motors are expected to be high, and the transmissions very stiff, we would like to implement a load sharing technique to make sure the motors share the loads sufficiently.

As we would like to avoid complex centralized systems, and possibly master/slaves architectures, we thought about something like droop control.

Unfortunately, I could find very little about droop control on the internet for load sharing applied to asynchronous motors. What I mostly find are references to load sharing applied to synchronous generators. And most of them imply a master/slave architecture

I have then three questions:

Is droop control generally used for distributed load sharing using asynchronous motors?
If so, how is it generally implemented? How does it work?
Are there other distributed techniques generally recommended?


texts: Can you differentiate between RFID types?

texts:
Background:
We have a project were we want to be able to assign a scanned RFID to an object in a database. The scanners, using Bluetooth, will vary wildly, but will use either UHF or LF, but at first pass, we couldn't see a way to tell the difference. The reader itself or the tags themselves, don't seem to attach any extra data regarding this. So we've resigned ourselves to having a manual toggle in our software.
But are there other ways?
Aside from frequency ranges being different, is there something inherent to a RFID tag that tells us if it is LF or UHF?


texts:
I have a DC high voltage (>270V) high current (>40A) circuit which needs to power a standard LED along the way to a heater. The LED is to indicate whether or not the heater is activated.

I'm struggling with dropping down the power to light the LED, whilst losing as little power as possible and maintaining an acceptable level of luminosity. Unfortunately I don't believe a potential divider will work, since the voltage source is variable (due to heater requirements) from around 30V to 300V.

What I need to be able is to have a stable low voltage signal powering a standard LED which shows whether there is voltage, with constant luminosity no matter the amount of voltage. Hope this makes sense.

Ideas I have looked at so far, without much success, are potentionmeters (power will be too high) and non-contact solutions (seem to only work with AC). A logic gate might work, but I wouldn't know how to incorporate a high power gate into this circuit.


texts:
I am doing math for a closed loop equation. I know the transfer function for a closed loop system is:

(Image copied from "Loop Gain and its Effect on Analog Control Systems" by Gabino Alonso and Simon Bramble)
$$ V_{out} = G \times V_{in} \tag {Eq 1} $$
$$ G = \frac {A}{1 + \beta A_0} $$

\$ A \$ - open loop gain
\$ \beta \$ - Feedback factor.
Now when I do the math like
$$ V_{out} = A(V_{in} - \beta V_{out}) \tag {Eq 2} $$

What is the initial of Vout to start with?
Vout numbers with 1 & 2 do not match and initial value of Vout is making a lot of difference.
Why are they not matching?
If A = 1000, B = 0.25, Vin =1, Vout =3.98;
>From Eq 1

Vout = 1000/(1+0.25*1000) = 3.98

From Eq2

Vout_initial = 0
Vout = 1000*(1-0.25 x 0) = 1000
Vout = 1000*(1-0.25 x 1000) = -249000
Vout = 1000*(1-0.25 x -249000) = 62251000

Never settles, what am I doing wrong?
If I chose A = 1; B =0.1, Eq1 and Eq2 numbers match eventually to 0.91

Vout = 1*(1-0.1 x 0) = 1
Vout = 1*(1-0.1 x 1) = 0.9
Vout = 1*(1-0.1 x 0.9) = 0.91

and

Vout = 1/(1+0.1*1) = 0.909

What's going on? What fundamentals am I missing?


texts: Can anyone explain the point of this dual PNP/NPN set?

texts:
I like to consider myself fairly experienced in Electronics Design, but upon being contracted to review this schematic I'm a little stumped. This is basically the output stage of a boost power supply:

I've drawn in the red lines to symbolise where the power actually flows. The MOSFET Q2 on the top left makes sense (although there is no base resistor for Q3, which is the first mistake I pointed out. 3.3V from a micro directly to a 0.7V base-emitter diode, youch!). This is just a P-FET power switch.

What's weirder, but, is after this - the Q4/Q5 pair. Q4 is another P-doped transistor acting as a switch, but the net driving its base in Q5 - and what's driving Q5? The output of Q4! It's a paradox if you ask me. There are two main concerns from me:

The first is, what's the actual point of this? The only thing I can
think of is, assuming Q4 (and thus Q5) turns on by "default" if the output +Vout
is shorted to GND, this turns off Q5, which turns off Q4, which
disconnects the output voltage from shorting directly to said GND.
Fair enough, if this is what it's for - if it's not though, please do correct me?
The second is, removing my assumption, will this even turn on in the
first place? If Q4 was a depletion mode P-MOSFET, I would say yes
as this would be "on" by default, let 12V flow through in the
"initial" state, and then turn on Q5 until the output +Vout was shorted to GND. In this case, but, this is just a plain-old PNP BJT which,
unless I'm crazy, is "off" by default. Thus, it won't ever turn on.

Thanks. Any insight from people would be great, as it seems like a handy little tool for preventing short-circuit overcurrent (although these days, this sort of protection is built into a lot of chips internally). But it looks to me like it hasn't quite been executed correctly, and it needs to be a depletion mode MOSFET there instead so it at least has a defined initial state.


texts: MPPT display voltage vs actual battery level

texts:
When I have a high load on my system the battery voltage on the MPPT display will go down. It usually sits between 12.8v - 13.1v however if the load is high (it is currently on 8amps) the battery level will drop down to 12.4 or something. This will then go back up if I turn the load off.

Why is this? I am worried about discharging the batteries too much and ruining them.


texts:
I want to use the third solution from this answer to step up three of my GPIO pins from my Raspberry Pi.

Would I need to make one of these circuits for each of the pins or could I, for example, replicate the bottom row again and increase the value of the resistor?


texts: Why can't current go through two voltage source junction?

texts: I crossed out the middle because it felt like it wouldn't make sense. (Mostly because i felt like conservation of current was violated.) But im not sure why it wont go through at that particular section. I thought whenever you have junction the current must go each pathway but why not in this case?


texts: Connect a geophone to an Arduino Uno board

texts: I'm a student working with an Arduino Uno. I don't have much experience in electronics. I need a help to convert the analog data that coming from geophone as the output and save it from .wav format.


texts: I don't understand convolution, and I would love to see some worked examples

texts:
I'm trying to get ahead on my classes for the school year and decided to start with Alan Oppenheim's Signals and Systems course. I'm already very stuck on how to convolve two signals. I have some specific examples from his textbook that I would love to see worked in order to get a better understanding.

The answer I get is different from the answer the book gives. I tried to graph both of these, and then shift h[n] through x[n] and calculate each point. However, this does not give the book's result of

Secondly I don't understand this problem

Any explanations or clues to understanding would be appreciated. I've been watching different videos and searching around and something just isn't clicking.

Below is my attempt to solve the first. I only had blue and black ink for the graphs, and it's not easy to see the different between the h[n] and x[n] graphs.

enter image description here


texts: What's the usage of the three boot mode of STM32f103?

texts:
If you see in refrence manual of STM32f103, you can see three boot mode for it. well, What's the usage of the three boot mode?

please say to me by example for each mode.


texts: Electric vehicle power component selection help

texts:
I need your advice on high power device selection.

I'm working with a similar application to this schematic, with the descriptions being in this forum.  Without reading through the dozens of pages (and several bad Oprah jokes that I don't get): it's a motor driver circuit for an electric vehicle.

Think 500A, 144V driven with PWM at 16kHz.  Parallel NMOS looks like the best solution, though I'm open to suggestions for monster parts that would be in the same price range and handle the full load...

With this kind of power, I'm thinking it's very important to have minimum losses (the original gate driver is described as an "Ultrafast MOSFET Driver", and the NMOS is rated at 11 milli ohms).  Price is a consideration, but should be compared to the losses adding up with daily driving use over years and taking range into consideration.

The driver in the schematic is EOL from what I can tell, so I need a recommendation on the driver as well.

In summary: I need selection help for MOSFET, flyback diodes and gate driver IC for this application.


texts: How to solve transfer function of a bandpass filter with Butterworth approximation?

texts:
How can I calculate the transfer function of this bandpass filter characteristic with Butterworth approximation?

\$A_{max}\$ = 0,9 dB
\$A_{min}\$ = 6,5 dB
\$\omega\$3 = 100
\$\omega\$1 = 300
\$\omega\$2 = 1100
\$\omega\$4 = 3300

Which steps do I have to take and what are some good resources for learning these kinds of filter design problems?


texts: Is this an RC filter in the circuit for a nightlight?

texts:
So there is this nightlight (a little flower that you plug in directly into a mains socket and switching it on gives you some light to light up your bedroom at night) which I dismantled and tried to know how its wired up. This is what I got:

simulate this circuit – Schematic created using CircuitLab

The mains is 230V AC @ 50 Hz and the capacitor C1 is of the shown type:
 except its marking is 224K 200V which I presume is 22E4 pF (ie 220 nF), 200V maximum voltage rating and K = 10% tolerance.

My questions are :

Is the R1-C1 combination acting as a filter here? Is this common in this kind of rectifier circuit?
I plan to make the same circuit, can the diodes be replaced by others from the 1N400X series?
The markings on C1 shows it's a 220nF cap, but measuring capacitance across the cap gave a reading of 580nF. Is this the result of the other parts of the circuit?
I plan to make the same circuit, is it a safe bet to use a 2.20 uF capacitor as C1 ?

EDIT: I had inadvertently swapped the values for R1 and R2. Now the circuit appears to be correct.
I made the following measurements across the components during operation:

\$\approx\$ 14mA through each LED
\$\approx\$ 2.95 V drop across each LED
\$\approx\$ across each diode
\$\approx\$ 1.37 Vdc across R2
\$\approx\$ 217.5 Vac drop across R1


texts: Can an old SMPS serve as a tablet/cellphone charger

texts:
A computer SMPS is capable of providing stable power supply to multiple devices like hard drive, CD/DVD drive, etc....

Is it possible to convert an old SMPS to power a tablet/cellphone?

What modification should I do an SMPS to serve 3.1 AMP 5.0 volt to charge 7200 mAh 10 inch tablet device?

I would like to convert a 450W PC ATX computer power supply with an input voltage of 5 AMP 230 volt, the output I want is 3.1 amp 5.0 volt which can be connected to a cellphone or tablet with a 2.0 mm DC pin

The IC which I see inside is WT7520.

I can see the high power components F12C200, D13007k, C5027-R attached with heat sink.

The label sticker provides the following input/output:

INPUT:  AC230V 3.5A 50Hz
OUTPUT: AC230V 1.5A 50Hz

But I don't know what is the current provided to hard disk power plug.


texts:
I am looking at the Q factor of certain inductors from the datasheet -
inductor datasheet

Now, I am trying to analyse the Q-factor for the 2.2uH inductor. The chart shays that the Q factor is 48 measured at a frequency of 7.9MHz. But, if I look at the graph it says a different picture. At 7.9MHz its is almost 70.

How is this possible ?

Also, my need is for the frequency range 300MHz and 2.4GHz (different inductors ofcourse).
So based on the graph the Q factor is not available for those frequencies. Do Q factors decay away to very low values after the peak or will it rise again at other frequencies ?


texts: Why do LEDs need resistors and lamps do not in a series circuit

texts:
Obviously a basic question but unbelievably difficult to get an answer

I understand that LEDs are diodes and that if you don't limit the voltage to a LED it will blow because it draws as much current as it can from what is available. However whenever I see lamps in a series circuit, there is no resistor associated with it which I suppose means that lamps only draw what they need. So my basic questions are as follows

a. Does this then mean you can do ridiculous things like power a 2V lamp with a 220V power source and nothing will blow?
b. If I am right with the fact that lamps draw what they want and LEDs dont how can I predict this for other components- ie how are these components then classified
c. Slightly tangential but if I connect LEDs in series (lets say there are three and are all 2V) to a 12V supply and then introduce one resistor that limits the available voltage for all the LEDs to 6V then surely the first two LEDs in the series will blow because I'm giving it 6V and 4V respectively when they only need 2V? Or perhaps Im misunderstanding the idea of the voltage available and the voltage used.

Please help. Would really like to understand these simple concepts


texts: What is the datasheet of this component in the photo, with markings 74YH S21B?

texts:
I need the datasheet of an SMD component, on which I can read
74YH
S21B

The chip is about 3mm x 3mm and, given its position on the board, has likely something to do with voltage regulation (but I can't be 100% sure).
It has 8 leads.
Please see the attached picture if that helps.

I have already explored the component-identification procedures proposed in the following post:
How do I identify SMD components? (or how do I identify any component)
but nothing clear came out (at best, hundreds of potential results...).


texts: Why base current is affected most on changing beta in voltage divider bias configuration of BJT?

texts:
In the given voltage divider bias configuration when the value of \$ \beta \$ is changed from 80 to 140 the base current changes from 21.26\$\mu\text{A}\$ to 12.9\$\mu\text{A}\$ which is a change of 39 % where as the change in quantities like collector current,collector to emitter voltage is merely 5.4 % and 5.6 % respectively.

simulate this circuit – Schematic created using CircuitLab

So,my question is why has the base current changed the most?

My guess to this question is that base current is in micro amperes so a change of about 10 micro ampere ,wouldn't bring much change to the circuit,although the operating point will be shifted.