texts: Simple power amplifier with feedback - designing procedure

texts:
I have a problem with understanding the whole feedback business in BJT power amplifier. So far, I only considered it in terms of thermal stability and \$β\$ uncertainty in simple 1-staged amps and was quite comfortable with it but now - in a full power amp - I fail.
Anyway, here's my problem. I do not know how to calculate the value of \$R2\$. The goal is to design a power amp that could produce \$5W\$ onto a \$8 Ohm\$ speaker at maximum input \$1V_{pp}\$. I did, however, established some value of \$R2\$ resistor but only using a real-time simulation (It was a blind adjusting, looking at the oscilloscope)
My calculation method is this:
For a \$5W\$ at \$8 Ohm\$ I need about \$6.5V_{RMS}\$ so \$18V_{pp}\$ => power supply of \$24V\$ should do it.
At the maximum level, the A point voltage sits at around \$22.4V\$.
Assuming that T2s \$β\$ = \$1000\$, the \$R3\$ has to deliver \$1.125mA\$ so:
$$
R3=\frac{(24V-22,4V)}{1.125mA}=1422 \longrightarrow 1,5k
$$
Now, at quiescent state, A point voltage sits at \$13.2V\$ so current must be:
$$
I_q=\frac{(24V-13.2V)}{R3}=7.2mA
$$
Now, that gives me \$I_b\$ of \$T1\$ transistor (assuming \$β=100\$)
$$
I_b=\frac{I_q}{β}=72µA
$$
To achieve this current I calculate R1 (\$V\$ at B point = \$12V\$):
$$
R1 = \frac{\frac{24V}{2}-0.65V}{I_b} \longrightarrow R1=160k
$$
And that's it, I have no idea how to proceed on calculating (not blind shooting) the \$R2\$ value when input is +/-\$0.5V\$. Also, I don't seem to understand how to calculate the open-loop gain.
Yes, I have multiple books with formulas but.. well, it doesn't help.
Could somebody please help me sort that out? I am a pure hobbyist so there is no teacher to talk to...

P.S. Forgive the battery biasing Darlingtons - that's just for simplification


texts: Transceivers - how to select an appropriate antenna?

texts:
I was considering purchasing these small transceiver modules but am unsure about sizing the antenna. I recall having read somewhere that the antenna must be in proportion (wavelength/4) to the transmission frequency or reception is impossible.

From what I recall, transmission at 915MHz would approximately require a 8cm antenna or so. What are the benefits other types of antenna over basic wire types? And what do you typically consider when sizing an antenna? Can you literally solder a wire onto the device and expect to receive/transmit properly?

I am looking to use these devices no more than 50 feet or so. I have read conflicting data about the dependence on distance.

Not sure where to start with this.

Thank you.

https://www.sparkfun.com/products/12031


texts: image distortion generating VGA signal on STM32 f4 using DMA

texts:
I'm trying to build a video generator using the STM32f4 (168MHz, using discovery board) + R ladder DAC to the VGA signal.

The idea is not to be based on a framebuffer (this would limit the resolution and color depth cause the board has 128k RAM externally addressable which allows 320x200 double buffer @ 8bpp) but to compose one line buffer by the CPU while the other line buffer is being sent to the DAC by the DMA.

The H-sync interrupt (at 30-something KHz for vga signals) would :

trigger sync signal generation,
switch linebuffers  between displayed and background buffer
start the DMA on the "displayed" linebuffer
then fill / do compositing of the "backbuffer" with data

This idea works quite well for now , except I see a LOT of horizontal jittering (up to 1/4 of the screen), resulting in vertical lines being stable in time but varying a lot horizontally (ie being not vertical at all and giving bad image distortion).

I suspect contention on the memory bus, but I gave DMA and interrupts the highest priority.
(there has to be memory transfers because the data line gets modified at each h-sync).

(same resolution static framebuffer  -320x200 repeated horzintally / vertically ) works quite well and does not have this shearing, maybe by a single pixel sometimes)

I'll include a screenshot as soon as I can.

Is there a means to improve on this, or am I damned by the frequent memory transfers between the CPU and the RAM ? Should I switch every N lines ? (ie have bigger buffers, reducing the number of switches but not the amount transferred ?)

Shall I separate buffers more so that the same "memory bank" / line is not solicited (if such a thing exists) ? Use several interrupts ?
Should I put the CPU to sleep before timer interrupts ?
Any idea ?


texts:
I`m new to electronic stuff, I was reading an artice on how control AC light using arduino, In part of solution there is a relay module which has a VCC and GND and IN and COM and NO and NC, but I don`t have that module instead, I have a relay like this:

can you please help me to find VCC, GND and IN in my relay? Thanks


texts: Can I see an analog signal with changeable frequency on oscilloscope?

texts: I have a sinusoidal signal with changeable frequency (which implies that it is not periodic). I wonder is it possible to see it on oscilloscope? Does it show non-periodic signals? As it is apparent my signal has different frequencies. The range of frequencies are less than 100 kHz.


texts:
I have always thought that MOSFETs have four pins [see wikipedia], one of them connected to the body (i.e. substrate).
However, when trying to order some, I have been completely unable to find any with a separate connection for the body; all the countless ones I checked had it already internally connected.
It would be really nice if someone knew some way (ie. nomenclature or something) to differenciate those! In other words: I am asking for an efficient way to search for MOSFETs where the body is not internally connected.

The generally applicable question above is more interesting of course but in case I have missed any possible solutions I will also describe my specific problem:
I am designing a quite accurate analogue amplifier and a sample and hold subcircuit. The sample and hold circuit needs an analogue switch with low leakage (the next stage has high input impedance and the usual leakage of a few nanoamps gives unaceptably high voltage errors and drift).
I had planned to either use an IC or build a similar cicuit to that shown in the lower right corner of the attached schematic. The trick with that circuit is that Q1 has almost no voltage drop across it when the switch is closed, so it also has almost no leakage.
Now the problem I’ve encountered is that the brute force approach of checking datasheets (on the farnell.com webshop) of either MOSFETs with 4 or more pins or analogue switches has not yielded any results after more that 2 hours. The problem with MOSFETs is that they have several pins connected to the same thing (e.g. drain) and all analogue switches I’ve seen have too much leakage current and generally bad documentation.

Thank you for your time

[English is not my native language; please forgive my blunders or — much better — edit them]

EDIT: Whilst the part suggestions are helpful for my specific case, I would also be interested in general terminology as this is more likely to be helpful to others.


texts:
This is a circuit I made to create a high signal when a switch is opened and closed. The duration of the signal can be adjusted by changing the capacitors and resistors.
It is also low powered when using a high resistance on R1 and R2.
This is a drawing and simulation I made on falstad.com/circuit

Is there a name for this kind of circuit?
Note:
I edited this question since it was of poor quality, so this question is only about trying to name the circuit.
I have created a new question with all the details, experience and requirements that I have. Improving edge detector with latching circuit for esp8266


texts: Apart from speed, do VSD's also alter current?

texts:
As I know it, a VSD alters the frequency to change the speed of a motor. I also understand that since the back emf of the rotor is directly proportional to the speed of the rotor, the slower the motor runs the higher the overall current there is going to be. Which explains why current is higher at starting of the motor, or at stand still altogether.

However, I've heard that the VSD can limit the current at starting of the motor whilst the motor accelerates from low speed to high speed. How is this possible? How does the VSD control the current of the motor whilst the motor is running slower than usual?


texts:
simulate this circuit – Schematic created using CircuitLab

Figure 1. Motor control schematic.

I am trying to replicate this circuit: Parastaltic pump driver.

The problem I have is after I lay out the circuit exactly as described, with a terminal block for the 12v power supply, the positive terminal of which goes up junctions to the Anode of the diode, then into the + of another terminal block, which runs to the pump, then comes from the - of the terminal block, junctions to the Cathode of the diode and then into the collector ([Pin 2][3]).

I have a 2.2kO resistor connected between the third and final terminal block + to the base pin, then I have the collector from the TIP120 and the - from the third terminal block going to the - from the 12v supply terminal block.

My understanding is that both power supplies need to have a common ground because obviously otherwise the + from the 3.3 PWM wont have anywhere to go and wont trigger the base of the TIP120.

Now, where it gets weird, for me...is that when I hook up the 12v power supply and I measure the voltage between the + and - on the 12v terminal block I get...12v...like the circuit is complete. The motor does nothing though. And no current is going through the base pin. If I take my pprogrammable power supply that I'm using in place of the 3.3 from the Arduino, plug it into the wall, do NOT turn it on, and touch the + lead to the + of the terminal block leading to the resistor connected to the base pin...the motor starts to slowly turn. If I touch the - from the power supply to the - terminal of the same block, it stop turning and something starts smelling funky (shut it off before I could investigate, the TIP120 is cold to the touch however).

Now, I did this in a project board and you know them, you have to do some nasty solders, so I thought, ok, I don't see any shorts or measure any shorts but lets do it in a breadboard just to be safe. Recreated the whole thing, same way, EXACT same result.

How the hell is touching the positive terminal of the powered off (if I unplug the DC PSU from the wall nothing happens when I touch the + lead to the resistor on the base) PSU causing the motor to spin? It also acts like its got plenty of current but low voltage as the motor spins up right away just very VERY slowly.

I've measured the DC motor and it takes about 375mA to get going and once its humming along with no load it draws around 80mA anything less than 375mA and it slowly ramps up, but obviously if I drop the voltage and leave the output current at 375mA it slows the RPM without impacting its ability to start.

I freely admit I'm new to this and learning but my understanding what, no base current, no circuit. But it acts like its free to carry all the voltage it wants, just no current. As to why hooking up the positive to a non powered on PSU allows it to start turning...and worse still why then also touching the negative from the powered off CPU appears to allow it to draw a LOT of current...I'm at a loss.


texts:
I am new with electronics and I have some issues removing DIP ICs from breadboard after testing something with them. I end up bending their legs if I pull them with bare fingers or pliers.

Is there some recommended way to pull them up nicely?


texts:
So i want to make a rgb led strip setup with irfz44n mosfets. The datasheet says that once 4.5v is applied on the gate the mosfet will start to let through about 9 amps. My psu is only 5 amps. Does this mean i can't dim the colors when using the arduino's analog pins?

EDIT:
Sorry for not being clear. I want to power my common anode led strip with a 12v 5a psu. Every color (red, green blue obviously) is connected to his own mosfet's drain, source pin going back to the psu's and arduino's ground. The gate i want to power with an arduinos analog pin. My question now is, will i be able to dim the leds since the gate-to-source picture on the datasheet says at 4.5 volts on the gate the mosfet will start to let 9 amps flowing from drain to source.


texts: Making prototypes with high speed SMD components

texts:
Even today we have breadboard and strip board on which one can make "quick and dirty" circuits and also test prototypes. However, we have now moved into an era of predominantly surface mount components many of which work at very high frequencies.

If one wants to make a circuit one may first need to design some simpler prototypes of fully understand how the complex off the shelf ICs work and determine their performance, sometimes we may find that the datasheets are wrong too. In this process if we find that a connection was wrong or the chip was fried, we can rewire/replace them easily when we have a strip board or veroboard, we can always use a breakout board for surface mount devices to generate pins from them.

However, for circuits that work and high speeds, doing so is not possible anymore. How does one follow the prototype stage in this case? It seems that the process will become longer and more expensive and rather inconvenient if PCBs have to be respinned many times.


texts:
I purchased a flashlight that came with 3x AAA cells. These are branded with the flashlight brand, labeled as Alkaline (Mercury and Cadmium free), LR03 AM4. Made in China. I am dubious of the Alkaline claim, but at least it's not a "Heavy Duty" cell.

What's odd is that the flashlight was working well, at full brightness. Then it dimmed. Some percussive adjustment it went back to normal, but eventually back to dimmed. Opened the flashlight, checked for corrosion, leakage/vented or a bad connection, there is none. Moved the batteries around, and suddenly back to normal. The slightest movement cause it to go back down.

Eventually I identified one of the cells as the issue. I could rotate it in place, and at some point it would work. This was the odd part. I couldn't get it to work normally again. Worse, I measured the battery voltage. -0.3V. Somehow, it has reversed it's polarity? A second set of these batteries from another flashlight shows one of three also having the same issue. -0.1V, while the other two show 1.49 and 1.52 volts. When on, this bad cell jumps to -0.56V when the circuit is pulling 5mA.

Obviously, this is a bad battery of questionable quality, but this is the first I've seen a battery go bad like this. What would allow a battery to fail and reverse itself? A normal chemical process? The other two higher voltage cells attempting to charge into a lower voltage cell (all in series)?


texts: Is this a ring counter ? What is its definition?

texts:
We can know the ring counter  like :0000 -> 1000 -> 0100 -> 0010 -> 0001,it  shifts the "1" bit.

Here is my schematic,the same as the schematic from the internet,and because my d-flip flop is active low,and Q=1 for set=reset=1 and set=0,reset=1,so as you can see,my output is not 0000,but 1000. I deliver a low signal at the white line ,0, to let first output become 1,and it does shift the "1" bit

So is it a ring counter? What is the definition of ring counter? Must it begin with 0000 and shift "1" bit from left to the right? or it is not necessary to begin with 0000 and just shift the bit,which is different from others, from the left to the right?


texts: What is the difference between OPB606 and TCRT5000?

texts: I had to make a path following bot. I needed an OPB606 sensor for that, however I couldn't manage. Instead I used TCRT5000, but the bot is not working. Is there a similarity between these two sensors? What should I do now?


texts: Increasing LED brightness on arduino-controlled 8x10 LED matrix

texts:
I have made an 8x10 LED matrix, controlled using a CD4017 decade counter and Arduino. A simplified schematic is shown below:

In the real version, there are 8 Arduino pins, and all 10 outputs of the decade counter are used (I have only shown a 4x4 for simplicity). The way it works is, for every clock pulse from the Arduino, the decade counter moves the output along by 1. This grounds one of the 10 columns of LEDs via the 2N3904 NPN transistors. At the same time, the LEDs that light up are controlled by turning on/off the relevant Arduino pins. By switching between columns quickly, the LEDs appear constantly on to the eye.
My problem is that the LEDs are pretty dim. I attribute this to the fact that the Arduino has to do a decent bit of processing for the display, meaning the LEDs can spend quite a lot of time off. I have tried to minimise this in code, but although it has had an effect, the LEDs are still dim. Also, the Arduino's power delivery using the digital pins is somewhat lackluster. How could I make the LEDs brighter? I was thinking of having an external power supply, and use the Arduino pins to instead control power delivery from this using transistors, but I have had trouble selecting a transistor for this to work. As far as I know, the LEDs are just standard 5mm LEDs, but I can't find any datasheet for them. I purchased them here.
Any help is appreciated.


texts: (Basic) How to connect the ground in this schematic to a breadboard?

texts: I just want to know how do I connect the ground in the circuit. I know how to connect DC source but I'm confused on how to connect the ground. I have adept knowledge about the concept of ground, I just want to know how to connect the ground(0V) in this schematic to a breadboard. I'm just playing the basics  in falstad but I got confused about this.


texts: Converting a NEMA 6-50p plug to NEMA 10-30p

texts:
I received a compressor recently that has a (I think) 6-50p plug on it but my dryer is currently plugged into a 10-30r receptacle and that's the only 240v I have available.  I'm renting the house so I would prefer not making changes to the receptacle.

Without thinking much of it, I purchased a 10-30p plug to put on the compressor, but while I was about to install it I realized the wiring is different between the two.  I know very little about this stuff and I thought I should seek advice before doing anything stupid.

If I'm not mistaken, the 6-50p is grounded while the 10-30p is not.

What would be involved in replacing the 6-50p plug with a 10-30p plug?  Is this even possible?

Here are some pics.  Thanks!

The current plug on compressor:

The one I purchased (that fits my the receptacle in my garage):

Compressor info:


texts: If a lithium cell is said to have a capacity of 20 Ah, does that mean all 20 Ah can be used?

texts: Toshiba's SCiB 20 Ah Lithium titanate cell is said to have a nominal capacity of 20 Ah. The cutoff voltages are 1.5 V and 2.7 V. Does this mean that all 20 Ah of charge exist between those two cutoff voltages? Otherwise to get all 20 Ah of charge one would have to completely discharge and thus damage the cell.


texts: Schematics of this mini high pressure switch

texts:
Does anyone have any idea of the internal schematics (illustration) of this? It seems they've incorporated a traditional one-port pressure switch and tee into a single casing, right?

https://www.soleaqua.com.tw/water-pressure-switch/high-pressure-switch.html


texts: Why would you put your input amplifier in front of your filtering for an ECG signal?

texts:
In this article at eetimes.com they show the signal chain for measuring an ECG.

The raw signal of an ECG contains noise and offsets at least a magnitude larger than the real signal. (Some few mV ECG, several tens of mV from power line noise and electrode offset and up to several hundred mV baseline wander due movement of the breast.)

This would intuitively make me do the filtering of the signal in front of the amplifiers, to avoid amplification of the unwanted signal components. In this article however they do the signal filtering after the input amplifier, the high frequency noise removal even after the second amplifier.

I can not really think of a reason why they would do this. The only thing coming to mind is the very high impedance of the signal source, but the filtering would not affect the signal source, because that frequency range would obviously be in the passband.

Am I missing some important reason why you would do the signal conditioning in this order?


texts: Not enough digital outputs for SPI slave select lines (CS#)

texts:
I have a microcontroller with only 4 digital outputs available and 4 digital inputs. The problem is that I need to communicate with at least 4 SPI devices (ADC's and DAC's). 4 SPI devices means 2 outputs on the microcontroller (MOSI,SCLK) and 1 CS per device => total of 6 microcontroller outputs.
Do you guys have a solution ?


texts: Measuring output of op-amp current shunt circuit using ADC

texts:
This is my first post here, so I hope I have done it correctly.

I am rather new to analog circuits, so undoubtedly I've overlooked something.

Here is what I want to do: Using a 24-bit LTC2400 ADC, with a precision voltage reference I want to read the output of an op-amp current shunt, the value of which is anywhere from 0mV to about 800-900mV. Since I want to be able to measure low voltage AC currents (isolated), and DC currents, both of which have the potential to output negative values. ADCs don't like negative values. How do I convert the negative part of the sine-wave to a positive part with good accuracy? I'm looking for +-.01mV resolution, and +-.1mV accuracy or better.

Now that I've described the problem, I'll explain my circuit. the circuit is based on the EEVBlog µCurrent. However, I have changed a few things. The analog side will be powered by a rechargeable 3.7V LiPo, and values read by aforementioned ADC. The measurement side is completely isolated from the microcontroller side. The microcontroller is an 8-bit Atmel. Values are read over USB using a serial connection. All resistors will be the "precision" type. I'm using a voltage follower for the V-GND.

So here are my main questions summed up:

Does my schematic design look correct? Anything I can add to improve noise?
Is there a better option for an ADC? (I'm using the LTC2400 24-bit)
On the ADC, how should I connect the FO pin?
Best way to convert the negative part of a waveform to a positive one.

On that last note, here are some examples of this that I found online:

AC voltage measurement using Arduino: AC voltage detector

Biasing an AC voltage for input to ADC

I'm still confused though, hence why I'm asking here.

Here is my schematic; sorry if it's not clear. +3.7V = +Vbat, -3.7V = -Vbat, V Gnd = Virtual Ground:

Here is an assortment of datasheets:

uCurrent Page

ltc2400 datasheet

MAX14850 datasheet

ADR4520 datasheet

MAX4239AUT op-amp datasheet


texts:
I have designed a Arduino shield that is designed to be placed in the field and log data from a sensor which it then saves to an SD card. In order to log this data, I must convert 5v SPI to 3v3 of course, so I designed in a TXB0104 (datasheet) 4 bit logic level converter.

This logic level converter outputs extremely noisy signals that only make it up to ~2v, with an extreme amount of noise between 1v and 2v. This noisy-ness occurs both when the SD card is inserted and when it is not. Here is an oscilloscope capture of one of the data lines:

Here is a picture of the board itself (R1 is not necessary BTW):

And a picture of the schematic:
(Sorry it's so crowded, I have the free edition of Eagle. Can't do multiple sheets.)

The 3v3 regulator (datasheet) does not appear to be browning out. It is rated for 800 mA.

Another possible source of error that I think is fine is the IC (datasheet) to switch the 3v3 regulator on (it is battery powered, so trying to conserve battery life while it is off). The power switch is rated for 2A.

One mistake I made when laying out the board is that there is no 3v3 decoupling caps extremely nearby the logic level translator IC. However, C1 (0.1 uF) is on the 3v3 line and very near the 3v3 regulator output there is a 100 uF electrolytic, so I don't think that is the main issue.

The code I used in testing the SD card is as follows:

#include <SPI.h>       // For SPI communication to the SD card
#include <SD.h>        // For interfacing with the SD card

//********************* PIN DEFINES *********************************

#define V_BATT        A0      /* Battery Voltage Detection */
#define CURRENT       A1      /* Motor current measurement pin */
#define LLS_EN        A2      /* Logic level shifter enable */
#define GREEN_LED     A3      /* successful startup */
#define RED_LED       A4      /* Error */

#define XBEE_TX       0
#define XBEE_RX       1
#define ENC_2         2
#define ENC_1         3
#define CARD_DETECT   4
#define MOTOR_EN      5
#define MOTOR_DIR     6
#define MOTOR_PWM     7
#define REG_3v3_EN    8
#define REF_4096_EN   9
#define SD_CS         10
#define SD_MOSI       11
#define SD_MISO       12
#define SD_SCLK       13

void setup() {
    Serial.begin(9600);

    pinMode(GREEN_LED, OUTPUT); // GREEN LED
    pinMode(RED_LED, OUTPUT);   // RED LED

    pinMode(CARD_DETECT, INPUT);
    pinMode(REG_3v3_EN, OUTPUT);
    pinMode(REF_4096_EN, OUTPUT);
    pinMode(LLS_EN, OUTPUT);
    pinMode(SD_CS, OUTPUT);
    pinMode(SD_MOSI, OUTPUT);
    pinMode(SD_MISO, INPUT);
    pinMode(SD_SCLK, OUTPUT);

    analogReference(EXTERNAL);
    delay(100);
    digitalWrite(REG_3v3_EN, HIGH);  // Turn on SD and misc 3v3 stuff
    digitalWrite(REF_4096_EN, HIGH); // Turn on 4.096v ref
    delay(250);
    digitalWrite(LLS_EN, HIGH);      // Turn on logic level shifter
    delay(500);                      // wait for everything to settle

    if(digitalRead(CARD_DETECT) == LOW) {
        if(!SD.begin(SD_CS)) {
            // Error, could not initialize SD card. Flash Red LED
            Serial.println("ERROR: Couldn't initialize SD card.");
            while(1) {
              delay(125);
              digitalWrite(RED_LED, HIGH);
              delay(125);
              digitalWrite(RED_LED, LOW);
            }
        }
        else {
          Serial.println("Success");
        }
    }
    else {
      Serial.println("ERROR: No card inserted");
      while(1) {
        delay(500);
        digitalWrite(RED_LED, HIGH);
        delay(500);
        digitalWrite(RED_LED, LOW);
      }
    }
    while(1) {
        digitalWrite(GREEN_LED, HIGH);
        delay(1000);
        digitalWrite(GREEN_LED, LOW);
        delay(1000);
    }
}

Any ideas are appreciated! I'll post back with updates if I make anymore progress.


texts: 555 timing capacitor discharge via threshold input

texts:
The circuit below is the timing logic for the SC280 UV exposure unit. Based on my judgement the design of the circuit is poor - and I'm planning to replace it -, I'm posting my question only to learn something more about 555 timer circuits and debugging similar issues in the future.

simulate this circuit – Schematic created using CircuitLab

The 555 is an NE555P, the UV exposure time is set with the R1 potmeter from 0 to 5½ minutes, and the exposure is started with the SW1 switch. The reason I checked the circuit is that the timer was inaccurate, the actual on-time was considerably less than the preset one (by up to a minute). As you can see the DISCHARGE and CONTROL pins are unconnected, even though they should be connected to C2 and to ground via a capacitor respectively according to the 555 monostable circuit on Wikipedia.

My question is how C2 discharges after the timer expires and if that way conforms to specification. Based on my measurement after pressing SW1 until the preset time expires it charges up to 10V (= ⅔ * 15V), then it drops suddenly to about 1V and then discharges slowly towards 0V. I suppose this was the circuit designer's intention, but it still surprised me, given that the discharge pin is unconnected and that (as I imagined, but also based on the datasheet) both the TRIGGER and THRESHOLD pins should be high impedance inputs. After building this same circuit on breadboard, I measured the discharge current (up to 400μA) to be via the THRESHOLD pin, while I didn't measure any considerable current via the TRIGGER pin. Looking at the 555 internals this pin is connected to the base of a BJT (which in turn is part of the threshold comparator).

Does the above discharge current go via the BJT's base-emitter junction? Normally (when the 555 is permanently powered via its Vcc pin) the THRESHOLD pin doesn't draw any considerable amount of current even if the timer has expired, so I doubt that this high discharge current would be due to normal BJT BE current to keep the transistor open. Maybe it's via the BC junction, due to Vcc falling below the voltage level on the THRESHOLD pin?

Is there any problem in THRESHOLD and TRIGGER being above Vcc? At least according to this NE555 datasheet they shouldn't be above it.

Why would someone choose this design over the more obvious (and correct?) one where Vcc is always connected to 15V and C2 is discharged via the DISCHARGE pin?


texts:
I'm having a problem getting I2C running with a PIC32MX795F512L.  It was not acknowledging the address byte being sent out, so I put a logic analyzer on SDA and SCL and got the trace shown below:

The two excursions on the SCL line are the only ones that occur.  So I don't understand why there are only two, instead of one per bit plus the start and stop conditions. This is obviously why I never see any acknowledgment.

Also, SCL is low all of the time before these sequence starts, and I expected it to be high and then go low with SDA high to indicate a start condition.  I have checked that I have pullups on both SCL and SDA.

The code I am using is straight out of Microchip's I2C example code.  Here is the relevant part:

   // Start the transfer to write data to the EEPROM
    if( !StartTransfer(FALSE) )
    {
        while(1);
    }

    // Transmit all data
    Index = 0;
    while( Success && (Index < DataSz) )
    {
        // Transmit a byte
        if (TransmitOneByte(i2cData[Index]))
        {
            // Advance to the next byte
            Index++;

            // Verify that the byte was acknowledged
            if(!I2CByteWasAcknowledged(EEPROM_I2C_BUS))
            {
                DBPRINTF("Error: Sent byte was not acknowledged\n");
                Success = FALSE;
            }
            else
            {
                Success = TRUE;
            }
        }
        else
        {
            Success = FALSE;
        }
    }

    // End the transfer (hang here if an error occured)
    StopTransfer();
    if(!Success)
    {
        while(1);
    }

It gets to the I2CByteWasAcknowledged call and fails.  Anyone have any pointers on getting I2C on a PIC32 to work with the Peripheral Library code?


texts: Mixed NPN and PNP H-Bridge DC Motor Driver

texts:
I've briefly looked at including an H-Bridge circuit in one of my designs and I see that most (if not all) have N-Type transistors (either Darlington
 or MosFets). This however needs two separate control signals to turn one half of the circuit on while the other is off.

Would the following circuit work? The theory (in my head at least) is that when the "Motor-Direction" signal is high N-Type Transistors T2 and T3 would be enabled while P-Type transistors T4 and T1 are disabled. Alternatively When the same signal is Low the opposite would happen. T5 would simply cut the power to the entire circuit and allow the motor to slow down and stop via the "Motor-Enable" line. I get that you would not have the Motor-Stop or fast reverse capabilities, but for a simple circuit that doesn't need that, would this not work just fine?


texts:
When I plugin my Osepp Uno (off-brand of Arduino Uno), the LED flickers a bunch, then the RX and TX lights do the same. But when I

ls /dev/ | grep -i usb

I get nothing.
When I startup the arduino IDE, and go to Tools -> Serial Port, All I get is:

/dev/tty.Bluetooth-PDA-Sync
/dev/cu.Bluetooth-PDA-Sync
/dev/tty.Bluetooth-Modem (<- this one is the default)
/dev/cu.Bluetooth-Modem

I tried to upload to all of the four above serial port connections, and the first two fail with avrdude: stk500_recv(): programmer is not responding and the latter two respond with Serial port ... is already in use. Try quitting any programs... They are obviously not the arduino port.

I don't think that the OS is instantiating communication correctly, because there is not /dev/tty.usbserial or /dev/tty.usbmodem or /dev/ttyUSB0 (this is what my board is on linux systems). It works in Linux, when I select Uno. I can upload to it and watch the serial port and everything one would expect in Linux.


texts: Using a Mosfet correctly as a switch in this circuit and how to prevent it from "loading"? the circuit

texts:
I have a staircase generator circuit with a Mosfet connected to capacitor 2. The input of the capacitor is connected to a comparator and I wish for the Mosfet to cutoff when the output of the comparator is high. The comparator is connected to a sine wave generator
The waveform I want to achieve is shown below.

I am having problems achieving this, when the Mosfet is disconnected as above, the wave form I get is this.  So the blue staircase wave is working as intended albeit no resetting. However the moment I connect it the staircase waveform is affected with some weird fluttering at the beginning and then it not resetting the staircase anyway . I have confirmed that with a manual switch the staircase resets as needed however I cannot get the transistor to work as intended.


texts: how to purchase simple custom devices with low quantities?

texts:
We have need for a few simple devices, mostly as adapters and connectors between other devices.

One example is:

6-pin Molex connector with 20-30V between two pins
24V to 12V DC-DC voltage converter
24V to 5V DC-DC voltage converter
2 x USB port (5V voltage output)
1 x simple DC power plug (12V voltage output)

I found suitable voltage converters as components: 24V to 5V, 24V to 12V

Now, my question is: how can I purchase this as an assembled device with a case? Is this prohibitively expensive for low volumes? I would need around 10 of these for testing, perhaps hunders or a couple thousand later, but nothing certain can be said about that. Should I attempt to find a simple sweat shop locally for the first 10, or can I buy them from China through some service? What are my options in general?


texts: How much electricity a human can conduct?

texts:
I have watched video on youtube  when a man exhibits  conductivity through his body. But how much current can a human conducts safely?   Is there any trick?

I have heard from a man who said that " I'd like to see him connect one wire to his left foot and the other to his right arm. It'll make current pass through his heart. Just a thousandth of an amp passing through any human being's heart can kill them."

How true is that?


texts: Why aren’t the main conductors in this underground power cable made from copper?

texts:
I’ve found a piece of electrical cable left by the electricity company that supplies the area. They did a repair recently underground.

I’m curious why the three big triangular conductors aren’t made from copper. It looks like aluminium to me, but I’d have thought copper would be a much better conductor.

What am I missing? Is aluminium almost as good but far cheaper?

Photo:


texts: How to measure amplifier circuit loop gain

texts:
In the last few days I've tried to understand how to get the loop gain (Aol*ß) of my amplifier circuit.
I've received several suggestion.
I would like to hear your opinion on this matter.
Are these 2 methods equivalent? Are they correct?

A (AC analysis in the point labeled as loop-gain)

B

Analysis comparison

Bonus circuit (AC analysis in the point labeled as loop-gain)
Why is this method wrong? Is it because the system is non-linear or because I don't have to change the DC operationg point?

Cheers


texts:
Hi i am a student & was hoping someone could please clarify on the below.

In a section of learning materials for a module I am taking the symbol for the MOSFET is shown and referenced (FIG 11) with respect to a CMOS NAND gate:

All other sources I have come across show the P channel MOSFET with the arrow pointing out on the  source terminal  & for an N channel MOSFET the arrow pointing into the gate on the source terminal(FIG a).

If anyone could please advise if there is issue with the symbol for FIG 11 as these variants contradict one another. I have searched through other questions on a similar nature to this, but my understanding is that the symbols used in FIG 11  should have a T connector gate rather than L type connector gate in order to adhere to common practice?


texts: Sizing of different PCB polygons on different layers for high current

texts:
I need to design some traces or polygons for high current (15A) on a 4 layer Lithium Battery Management System board, but I am unsure about their sizing.
I am following a reference design from TI, from which the screenshots of the PCB below are taken. The board is a Lithium Battery Management Solution (https://www.ti.com/tool/TIDA-00982).
My question is general ,but I use this board as an example.

The red marked polygons go to a Lithium Battery positive terminal with 15A continuous current.
The narrowest side of the polygons is 3.5mm on top and second inner layer, 2mm on the bottom layer (no connection on first inner layer).
I'm trying to understand how they calculated the sizes of those polygons.
I can order only 0.5 oz inner layers and 1 oz for external, so I probably need to increase the size of those polygons.
I thought: the polygon on the top layer is fixed due to other components, but I can increase the polygon on the second inner layer and bottom one (connected through multiple vias).
The problem is how much?
If you have two mirrored traces between the same points, on two different layers, the current will be halved. What if you have different polygon sizes and on different layers (externa/internal)?
Should I calculate like below?

current per polygon: 15A / 3 polygons = 5A per polygon
top layer polygon size (fixed): 3.3mm --> use Trace Width Calc with 5A, 40C temp rise, 1oz copper --> 1.2mm trace width for external layer-->top layer is ok
inner layer 2 polygon size:  use Trace Width Calc with 5A, 40C temp rise-->6.2mm trace width for internal layer

bottom layer polygon size: use Trace Width Calc with 5A, 40C temp rise, 1oz copper --> 1.2mm trace width for external layer.

Now that I have the width of the polygons, what about the length? Does the length not matter for heat dissipation? Is length decided by the requirement (in this board) “short low impedance connections for power connection”?
Thanks for your help


texts: Help understanding simple circuit - ADC0803LCN

texts:
Would someone mind having a look at the circuit below and explaining in very simple
terms :) what the circuit below is doing. Circuit is taken from the ADC0803LCN datasheet.
Looking in particular at the area within the red box - Span/2 = 2V

Probably not relevant but I'm trying to adjust the analog input range of the ADC0803LCN from 0-5V to 0.5-4.5V.


texts: Why would a USB cable give less power after being used for a while?

texts:
I'm asking this from the perspective of wanting to understand what actually happens inside the cable.

I use this app to measure how many mA are being received by my smartphone while charging. Some cheap cables seem to be unable to transmit enough power to charge my phone. So I always test cables with the app before buying them. Last time I was in the shop, I tested one that only gave 200 mA. The one I ended up buying (two pieces of) gave 1100 mA. I used the same power adapter (it's the one that came with the phone) for all the tests. The two cables I bought would sometimes it gives as much as 1300 mA.

Today I was charging with one of those cables (one that had consistently been giving me around 1000 mA for weeks, and I noticed that the battery level was going down even while I was charging. I tested with the app and I saw that I was only getting 150 mA. Using the same cable in another adapter gave a similar result. I tried the other (identical) cable that I had purchased at the same time, and I was back to getting 1000 mA.

Clearly, something bad had happened to the former cable.

Speaking in terms of the inner workings of the cable, what would cause such a change in the cable? (Its ability to transmit power dropping drastically.)

Additional information:

The change appeared to happen suddenly. It was sort of like one day the cable was fine, then the next day it was at 150 mA.
I live in an area with a very unstable power supply. There are often surges and fluctuations in the current here. Many people have stabilizers, etc, on their electronics to protect them from such things.
Several of my cables have just stopped working altogether after some weeks of use.
The observations of the app are somewhat corroborated by the fact that when the app displays a low mA, the battery level of the phone goes down if I use it while charging, wheras when it displays a high mA, the battery goes rapidly up, even if I'm using the phone. I'm not saying the app is exact (it may even be off by several hundred mA), but it gives you a rough idea. I'd say 150 mA vs 1000 mA is a significant enough difference to make the app relevant.


texts: Altium: Change Net Label Size and Font at once!

texts: I have a complete schematic project in Altium Designer. I need to change Net labels text and font. Since I have a huge number of Net Labels, I am wondering if it possible select for instance 20 different Net Labels and change the size and font at once instead of change just one at a time!!


texts:
I'm quite new in the microcontroller world, since I work on it only for my internship. But I have a problem in my main project. I was implementing an automaton based on a PIC18F46J50, and we printed the final product on a board using a new pic. I choosed a PIC18F45K22.

We realised yesterday that this PIC does not handle th RTCC module, and it is one of the main features of this project.
Since the board is already printed, it's a big problem to find a PIC with the same number of PIN, but it's my year project, so it's quite important for me to find a solution
so here is my question.

Is there any other PIC that have 44 PIN (or 40) and a RTCC module ?
Or is there any way to implement a RTCC module without it on the PIC ?


texts: Resistor calculator to get close to a final value?

texts:
If I search on internet I see thousands of serial or parallel resistor calculators, where you can fill in the 'input' resistors, and the output resistance is given.

However, I wonder if there is a program/app/website where you can set the output resistance, and it calculates the closest value using e.g. 1, 2, 3 and 4 resistors in any serial/parallel combination.

So. e.g. I want a resistance of 1.5K.

The result would be something like:

1 resistor:1 K ( = 1000R )
2 resistors: 1 K + 510 ( = 1510 R)
3 resistors: 1 K + 470 + 22 (= 1492 R)
4 resistors: 1 K + 470 + 22 + 10 ( = 1503 R)

Probably there are better solutions using parallel combinations, but to find them is quite hard (trial and error).


texts: Need a circuit that lights a LED but shuts down LED after a while

texts:
simulate this circuit – Schematic created using CircuitLab

I am thinking of creating a circuit that lights up a green LED once the garage door is open so I don't need to lean out the car window to see when the garage door is open all the way. A switch will be triggered once the garage door is all the way up. But if I leave the garage door open for more than a couple of seconds, or even minutes, then the LED should stop shining so the battery doesn't drain, and once the circuit is open (garage door is closed) it should 'reset' so that it lights up the next time I open the garage door.

I want to use basic electronic components, and no chips.

I've tried something similar to this:

I've used software to try and emulate but.. I've more or less lost my train of thought.

I've tried this in the circuit designer:

Once I click the switch into closed it lights up, but when I click OPEN and wait, then click to close the circuit it seems the capacitor isn't discharged and led doesn't lit up.

What's the best way to go about this?


texts: Ceramic capacitors: how to read 2-digit markings?

texts:
Related question: Ceramic capacitors: how to read 3-digit markings?

I have some ceramic capacitors with a 2-digit marking. How to read them? Do the colored markings at the top mean anything?

Image description:

Brown ceramic capacitors with 10 written and a black mark at the top
Brown ceramic capacitors with 47 written
Yellow ceramic capactiors with 1n0 written and a green mark at the top


texts: Microcontroller with ADC and capable of SPI communication

texts:
I am designing a system where

Analog Signal ---> (ADC- Digital Data )---> UWB chip mostly WSR601 or AL6301/AL5100 Chipset

Note (1): UWB is an abbrieviation for Ultra Wide Band wireless communication technology. Wireless USB chips which are being used here make use of this technology. So, in short the data is transmitted at 5 Mbps to the UWB (wireless usb) chips using SPI or USB 2.0. These wireless chips then transmit data to the receiver.

Note (2): The data sampled through the ADC just directly needs to be passed on to the UWB chip through whatever interface (USB , SPI etc). Data does not need to be processed in any manner.

I am looking for a microcontroller to perform the function of ADC and interface with the UWB chip. Both (WSR601 and AL6301/AL5100) support various options like USB 2.0 , SPI, SDIO 2.0 , UART etc.

1) The ADC that I need is 10 bit and the data rate resulting from that which I need to transmit to the UWB chip is around 5 Mb/sec. ADC sampling rate required would be around 5 * 10^5 times per second.

2) It needs to be as low power as possible

3) Would SPI be the best choice for this considering the data rate and the low power or do you think some other communication interface would be better?

4) Any uC suggestions having sufficient processing power for the ADC and SPI to work simultaneously?

I was suggested PIC32MX250F128D by someone who claimed that it consumes 14.5mA at 40MHz, 3.3V. But again this uC has a LOT of interfacing options available which I think is unnecessary and also this uC doesn't seem to be available on the microchip website.

So I hope someone can suggest uC with a little lesser functionality and hopefully lower power consumption than one under consideration.


texts: If resistors do not decrease flow in a circuit then why are they able to make things like an LED short when otherwise it would without the resistor

texts:
So I just spent the last 8hrs trying to comprehend how resistors function in a circuit and still cannot find a source of explaining it to me. And please not another water analogy. I already feel hydrated and I only drank one cup today.

It is said that every component in a circuit "absorbs voltage" like a 9V battery going in a 2V LED making the voltage coming out the LED 7V. I thought that once electrons are through a circuit they must go somewhere and that nothing can take away power (energy cannot be destroyed) like the case of a resistor where it's just slowing down the electrons. So where did that voltage go to?

In the case of the LED/resistor relation, if the resistor is not 'reducing' the amount of electrons then how is it preventing an LED from smoking if it's just slowing down the electrons? Which still makes the current the same through out the circuit.

I'm tired after an uneventful day so the wording is really butchered. But hopefully my questions go through.

I think my understanding of the fundamentals is jaggedy. I also feel like I have to be really good in algebra to be able to grasp these aspects.


texts: Conflicting impedancies in peak detector

texts:
Here a circuit :

Here is a scope view of what I get before the diode (in blue : input, in yellow : output of the Op Amp):

The opamp saturates almost everytime. There is just a small time where the signal is non-zero due to the presence of the capacity (when I get it off, everything is okay at the output of the opamp (always before diode) ; when I put a resistance before the capacity, everything is okay also). But I can't explain more. Someone to help me?

The circuit performs well in any case, it is just a wonder of comprehension.


texts: Rated frequencies and power requirements

texts:
(Here is a related, earlier question.)

Two microprocessors are identically manufactured.  However, after testing the two processors, the manufacturer bins, rates and labels them to operate at slightly different frequencies -- for example,

Intel's Core i5-3320M (2.6 GHz) and
Intel's Core i5-3360M (2.8 GHz),

whose specs differ only in the clock rate.  Once the manufacturer has shipped the two processors, assuming that the customer clocks each processor at its respectively rated frequency, I've five, closely related questions, please:

Am I correct that the faster processor draws more power (and thus dissipates more heat) under a computational load?
If so, is the power under computational load approximately proportional to the rated/clocked frequency?  In other words, inasmuch as the one processor is clocked 8 percent faster than the other, does it run about 8 percent hotter under load?  Another way to ask the same question is to ask:  does each processor process about the same quantity of data per unit of energy? or, if battery powered, can each accomplish about as much before its battery dies?
When not under load, do the two processors idle equally cool, or are there practical or theoretical factors that make the one idle cooler than the other?
Even if the processor's price were not determinate, might one prefer the slower processor merely for the sake of cooler operation and extended battery life?
Would the answers differ for embedded processors?

Naturally, you needn't number your answers 1 through 5.  If the general thrust of my inquiry seems clear, then feel free to answer accordingly.  Even partial answers would be read with thanks.

The reason I ask the question -- besides that it is interesting -- is that Intel (for example) gives each of the processors mentioned a thermal design power (TDP) of 35 watts.  Such information hardly helps one to choose between two such processors (or between two microcontrollers by ARM, etc.) as one hesitates between quick peak processing and cool extended operation.  The question is thus a prudential engineering question that datasheets do not seem directly to address.


texts: Inductor : how to choose toroidal ferrite core material

texts:
I want a 2.2mH toroid inductor working at 200kHz switching frequency able to keep 2A saturated current. I found a ferrite core provider with these possibilities :
- Core FT50-61 (12.7x7.15x4.9) with AL=69 needs 178.6 turns
- Core FT50-75 (12.7x7.15x4.9) with AL=4200 needs 22.9 turns

So which core should I choose to make a 2.2mH toroidal inductor 2A saturated current?
I suppose that the AL parameter is the key. Can you explain me why?


texts: Where do the RGB LED matrix resistors go?

texts:
I have a number of 8x8 RGB LED matrices.

Each has 32 pins, and you could (barely) characterise them as common anode - all the anodes in a row are common, but so are all the Red, Green and Blue cathodes in each column.

In short, I don't know where the resistors should go: but I figure that 24 resistors on the cathodes is better than 8 on the anodes. The Red voltage drop is 2.2V, while both the Green and Blue are 3.3V - and all are reportedly 50 mA (max 70 mA) LEDs.

To avoid brightness "droop", do I (5V supply, 30 mA drive each):

Provide no resistors at all (I don't think so!);
Provide the maximum for 1 LED (100Ω for Red, 68Ω for Green and Blue);
Provide the minimum for 8 LEDs (12Ω for Red, 8.2Ω for Green and Blue);
Average the results (stuff it: 47Ω for the lot of 'em!)

Before you start, I don't want to use an LED driver like the MAX7219 or AS1107 - there are too many matrices, and I'm multiplexing the multiplexors already...


texts: Wideband impedance matching of a power amplifier

texts:
I want to design the impedance matching circuit for an underwater acoustic power amplifier. Because the power amplifier should work in a range of frequencies, the output impedance changes due to the frequency variation (i.e. I think I need a wideband impedance matching). Thus, the common matching methods such as transformers and filters are not suitable for my purpose. I just know the input and output impedances, nothing more.

How do I solve this problem? Would an audio transformer work? If not, what should I use instead?


texts:
I was given the task to design a circuit that has a 5V input and uses a differential op amp to provide an output that oscillates between 5V and -5V. The design I came up with is the following:

simulate this circuit – Schematic created using CircuitLab

Basically, I have a ~50/50 555 timer generating an oscillating output of 0 or 5 volts, and this setup will, in theory, create an output that oscillates between -5 V and 5 V. This output will make the two LED's flash one at a time.

When I ran a simulation of this circuit, it worked swell when I had an oscilloscope in place of the LED's. When I went ahead to build the actual circuit, what struck me is this: I have no idea how to give the op amp chip a -Vcc equal to -5V.

How would I do that? Additionally, is there an alternative setup you'd suggest to accomplish this task?


texts: Using Parallel MOSFETs as a simultaneous switch

texts:
I have searched quite a while, but using parallel MOSFETs to alleviate thermal issues and dividing currents seemed to be the critical issues for lots of people.
For me, I'm trying to use the parallel Nch MOSFETs(2N7002NXAK) to turn switch on and off at the same time. But it doesn't look like people are using parallel MOSFETs like this since I couldn't find any example.
I only have 1 GPIO to spare but 2 devices that I need to pull down when not in use. Is this not the normal way to use parallel MOSFETs at a switch?
Thanks


texts: I'm working on a 4 layer PCB with internal 2 layers being power and GND... 2 outside layers are signal. Is it better to have a pour on the outside layers or just leave them empty except for the signals?


texts: Project with wattmeter in proteus works and in practice there is difference of values

texts:
in my project i'm using a current sensor ACS712 30A, for measuring current, i tested on proteus 8.6 sp3 and works ok, but in practice (using protoboard) the sensor it's accusing current without any loads connected. here's the part of my code that deals with the ACS712   obs: i'm measuring AC current and arbritering 220 V as voltage

    while(1)
    {
       char ACS[15];
       char Corrente [15];

       pino1 = 0;
       for (i = 0; i < samples; i++)
       {
           pino1 = pino1+ ( ADC_Read(0) - 511.95  );
       }
       current = pino1;
       current = current / samples;
       current = current * current;
       current = sqrt(current);
       current = current / 8.6f;

       FloatToStr(current, Corrente);

       potencia = ( current * 220 );
       FloatToStr(potencia, ACS);
       Lcd_Cmd(_LCD_CLEAR);
       Lcd_Cmd(_LCD_CURSOR_OFF);
       Lcd_Out(1, 1, "AMP =");
       Lcd_Out(1, 7, Corrente);
       Lcd_Out(2, 1, "P =");
       Lcd_Out(2, 5, ACS);
       Lcd_Out(2, 16, "W");
    }


texts: Choosing a resistor for connecting a bipolar transistor

texts:
I need to run some LEDs using Arduino. The total current consumption is about 190 mA. For these purposes, I found a bipolar transistor
PMBT2369 (Nexperia).

Transistor characteristics:
- Maximum emitter collector voltage -> 15 V
- maximum current collector -> 200 mA

I have a question on the choice of the nominal resistor on the base.
Can I get a 2.2 kΩ resistor for this purpose? Or should I choose another resistance?


texts: Connecting a 3mm electrical wire in a non air environment?

texts:
Is it safe to connect a 3mm electrical wire (running 240 V) in a complete closed no air environment (Completely sealed "Hazard proof" cabinet) ?

I will use similar to the below


texts: Replacing Nimh battery to Li-ion in hybrid cars

texts: is it a good idea to replace a Nimh battery in hybrid car (like prius model 2012) to Li-ion battery without any problems.


texts:
I'm dealing with a question about an implementation of a full adder with component delays.

tpd(XOR) = 5 ns
tpd(AND) = 2 ns
tpd(OR) = 2 ns

I'm having problems solving for the the propagation delay for the S and Cout outputs. How do I find the propagation delay?


texts:
I have a circuit with two supplies. A 19v supply for stepper motors, and a 5v supply for driving the ATMEGA644, 3 stepper motor driver daughter boards, a bluetooth LE daughter board, and 2 ws2812b rgb leds.

With two supplies everything worked, but I really wanted to get it down to just one supply. So I did another version of the board using just the 19v supply and a VX78-500 switching regulator. I used their recommended input and output caps. (But not the low noise version that include some extra inductors) .

I have a 100uf electrolytic on the 5v rail. Not 100% sure if that's a good idea but it's well below the max capacitive load for the VX78-500 which is 680uf and I thought it might help with noise.

I also have 3 100uf electrolytic on the 19v line next to the stepper driver boards for the same reason.

When I first turned things on I noticed the WS2812b'd flashed slightly but everything was fine. That didn't happen on the 2 supply version of the board. However on maybe the 3 or 4th time I turned it on the bluetooth LE daughter board died. Which is kind of surprising because it's got its own on board 3.3v LDO regulator.

I don't know that much about supply best practices/inrush current, etc. I knew my new setup would be noisier using a switching supply/being down stream from the same supply as the steppers. Any ideas what is going on? That flashing makes me think there's a bad spike happening at switch on time. It seems weird that the atmega644 is still ticking but the BTLE daughter board died. How do I trouble shoot this?

Are those 100uf caps just a bad idea in general? Does my circuit need some other form of protection?

Those daughter boards are $19 so I don't want to blow out too many of them in a search for the solution. Here is a pic of the PCB.  I'm sure I'm just making some noob mistake, but I'd really like this 1 supply version to work.

Oh ignore where that says 12v, it's really 19v.  blush
Thank you for your time.

Here are the two sheets of schematic as well.


texts: Revolutions (pulse) per minute counter circuit?

texts:
Does anyone know how to set up a circuit by using counters, decoders, 7 segment displays and a 555 timer to show the revolutions (pulses) per minute from a photo-transistor?
I'm doing this as part of my own project but I am not sure of what other components I need and how it could be wired.


texts: Building a DeWalt Charging Circuit - Getting out of my depth - Help?

texts:
Problem:

I'm working on a project that will require a 60V DC (mobile) power source. I'd like to use DeWalt 20V 5Ah batteries to supply this power, 3 in series x 3 in parallel (9 total).

Part of this project will be making a circuit that can charge all 9 of these at once, without removing them to put them on a separate charger. I could use help designing the circuit to control the charging. I'm getting a little out of my depth, so I thought I'd see if anyone has any ideas.

Research I've Done:

To understand what it takes to charge a DeWalt battery, I built a test rig, depleted a battery, and sampled the current and voltage during the charging with 1 battery and 1 stock charger.

Testing Circuit:

I don't have access to any more sophisticated equipment than a basic multimeter, so I bought some ACS712 chips off amazon, ran wires from the charger to each of the pins on the battery, individually. This gave me access to measure each cell in the battery as well as some control signal inputs.

Here's a rudimentary diagram of my setup:

Testing Results:

What I learned, in broad strokes, is that the Dewalt charger applies a constant current of 4A until the output reaches around 19V, then it switches to a constant current of 2A until the output must be around 19.8V. At that second milestone, it maintains a voltage of ~19.6V and notifies the user that charging is complete by triggering the "TH" pin.
 - An interesting note, here, is that I measured no current across any pins except the TH pin.

Chart (noisy because of cheap equipment):

Note: I limited the Y-axis of the voltage to 18V-20V, each of the C1 through C4 pins shows the same line as TH but scaled to represent the lesser number of cells measured across (I felt relevant cutting that portion of the graph off as there was no current across the lines leading to those pins).

What I think I need:

Because I'm going to be charging 9 batteries (3 in series x 3 in parallel,) I believe I need a circuit, then, that can generate an output of 6A (2A * 3 in parallel, ignoring the 4A stage) through a range of voltages from around 54V to 59.4V to charge all at once. I'm open to counter-arguments on this, that's why I'm here!

I'd like to stay as IC as possible, but I emphasize simplicity over being strict on that. I'd be ok with using a microcontroller to monitor the charging cycle and control different states in the process (ex: from 6A to 0A when charging is complete).

What I need from you:

Suggestions if I'm heading down the wrong path anywhere above.
Help designing the circuit that can charge these batteries.


texts: How to make a small amplifier, able to amplify a signal 2 × the input

texts:
I have a small device expecting a signal in the 8MHz range of 2V peak-to-peak.

The output of my signal generator (or rather the device that outputs the modulated signal) is only at 1V peak to peak.

My idea is to construct a (very) simple amplifier to boost the signal. The only requirement for this amplifier, is that it is

small, simple, and (relatively) low noise
non-inverting.
Non-inverting is very important, as it is an analog picture signal.

As I understand it, I'd simply need a single transistor, but I'm not sure how to wire it up, so that it acts as signal amplitude doubler or something. The signal source is stable, i.e. the amplitude never goes beyond 1V and the amplitude is never lower.

Perhaps using an op-amp circuit would be better, given the output is not necessarily high impedance?

I'm not sure where to start, even though the application is "pretty simple" at first glance.


texts: Control a knob on a Honeywell fan via ESP8266

texts:
Hey all I am wondering what all I would need in order to control this knob on my
Honeywell 2-in 1 Air Circulator Fan, HT-9700

I am wanting to use a ESP8266 in order to control it via wifi. I know how to do it on that side but I am unsure what's available for the other side (the knob) in order to "turn" the knob or hook into the knob wires.

more images:

OK So here it is:

BROWN wire = Low fan speed
RED wire = HIGH fan speed
BLACK wire = HOT

With the black prob on BLACK and the red prob on RED with the fan ON/HIGH I get: 09.9
With the black prob on BLACK and the red prob on BROWN with the fan ON/LOW I get: 00.0
With the black prob on BLACK and the red prob on RED with the fan OFF/OFF I get: 124.4
With the black prob on BLACK and the red prob on BROWN with the fan OFF/OFF I get: 124.4

Note I am using the AC mode on my multi meter that looks like this:


texts:
How exactly a ground plane helps inproving antenna gain? What is the logic behind it?

As per my general understanding, ground plane in reference to any perticular signal trace on PCB helps to absorb unwanted radations. Hence reducing radiated noise.

But in case of a antenna as it is a radiating element, how a ground plane works in other way.

A also heard about ground plane works as a reflector for antennas. Need to know more about it.


texts: How to tell flat flexible cable(FFC) alignment when inserting?

texts:
I have an MSR with an 8 pin FFC with contacts on one side. I don't know if there is a top and bottom and if so how to tell the orientation. There is writing on the contact side I assume to indicate alignment that looks like

<-
D1|
D2|
D3|
D4|
D5|

Does this indicate that with the contacts and writing facing up, the left most pin is pin1?

The header designed to accept it is an 8 pin FH52-8S-0.5SH, with contacts on top and bottom.

The header has a triangle on one side to indicate pin 1 on the header.

Am I correct in assuming the FFC should be inserted with the contacts up so the left most contact is on the same side of the header as the triangle?

In general, is there a rule of thumb that contacts should always go up or down or does it just depend on the design?


texts: Connecting transmitter coil to the oscillator

texts:
Hi guys i have two problems.

1.Where to connect the transmitter coil to the oscillator part?

2.How to make the output of the oscillator stronger? because someone told me that the output coming from the oscillator is weak. i need a stronger output to make a decent magnetic field from the coils.

im just new to electronics and i want to learn more, hope you can help me guys


texts: 480v delta/400v wye with Neutral ungrounded

texts: I have a European machine using a 480/400 volt three phase transformer. The neutral conductor is used to power some devices at 230 volt. The manuf. insists that the neutral must not be solidly grounded. I believe this creates an unstable electrical environment for the machine electronics also, it creates a shock hazard under ground fault conditions. Am I thinking correctly on this?


texts: Powering a Raspberry Pi Rover with Lithium Ion Batteries and Charging Them

texts:
I am working on a 4 wheeled rover project. As the rover needs to be operated remotely, I will need some sort of batteries onboard. The major parts that need to be powered by the batteries are:

Raspberry Pi 3
Raspberry Pi Camera 5 MP
Arduino Uno
6V Brushed DC Motors

The Pi Camera will draw its power from the Pi. The Arduino is to be connected to the via Pi USB. The Arduino is to control 4 x DC Motors for the wheels with an LM298 H-Bridge IC. The Pi will draw its power from the batteries through a 5V Step-Down converter. The Arduino, and the Pi Cam will draw their power from the Pi's USB port, and CSI interface respectively, and the motor voltage pin of the LM298 will be directly connected to the batteries.

I believe a battery with a 2A output will be sufficient. I am looking forward to using two protected 18650 3000mah batteries in series. This will give an output of 8.4 V at full charge, which is suitable for my application.

1) How do I charge two 18650 batteries with a single charger?

I found this Li-Ion charger module based on the TP4056.

With an output of 4.2 V and 1 A current, it can easily charge a single cell 18650 battery. However, I need to charge two cells simultaneously.

I came across this design on the Adafruit website for LiPo batteries and a different charging circuit:

Here, the two cells are connected to the charging circuit in parallel during charge mode. When the relay is switched, the charging circuit is disconnected and the batteries are connected in series.

I wish to use this design with a Lithium Ion 18650 and a TP4056 charging circuit. Is a TP4056 charging circuit capable of safely charging two batteries connected to its output terminals in parallel?

2) Are the batteries safe to be used in series configuration?

Since each battery has its own protection circuitry, will the protection circuitry work as it should when the two batteries are connected in series during usage?

3) Which step-down converter should I use for the Raspberry Pi?

I believe I need something which can take 7.4V input and give a 5V voltage and at least 2A current output.

I hope my questions are clear. Thank you for taking the time to read.


texts: STM32 in emmc-slave role. DMA transfer by both edges of external clock

texts:
I want to implement emmc protocol in a device role with STM32 (for now I've had ST-Nucleo-F767ZI and ST-Nucleo-F429ZI dev boards). Idea is to have a bridge to real emmc with STM32 as an adapter.
STM32 (emmc mem) should sync by the external clock from the host. Here I suppose to use TIM1 in external mode 1 (TI1_ED) and capture the data from gpio by DMA.
Emmc could work in SDR and DDR modes (so, in sdr packet syncs by one edge of the clock, in ddr by both) but even with activated TI1_ED trigger source to have PeriodElapsed interrupt events I should set counter to 1 and I found that it appears only by every rising edge, not by both.

Is any more clear/flexible way to work with external clocks at SMT32 (then TIM1 in external mode 1)? Or configure the integrated host-emmc controller in device-role?
Is that possible to trigger DMA transfers (and got interrupts) by EVERY edge of TIM1 input?

Please note, that I've tried to find FPGA with IP cores SD / SDIO / MMC Host Controller, but didn't get any cheap variant (the price more than 15$, even about 25). If you can suggest something (even by architecture), it definitely will help a lot.


texts:
How can I customize board shape in Proteus ?
I've seen answers in other forums saying "use the 2D closed path" tool, but none demonstrate how exactly.
I want a hexagonal PCB, is it possible ?


texts: Voltage divisor on a oscillator output using Capacitors vs Resistors

texts:
My question is pretty simple.
Why does this chip datasheet suggest to use a voltage divisor using capacitors? Does it make a difference to use capacitors instead of resistors?

Edit: Link to datasheet -  Page 800
https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/i210-ethernet-controller-datasheet.pdf


texts:
I am a newbie trying to build a simple circuit for reversing polarity (using the components I have). The intention is to control a DC three way motorized ball valve. The valve has two positions and to switch I have to change the polarity of voltage applied to the input wires. I would like to make the switch happen via output from a couple of RPI GPIO pins.

The schematic is attached.

Most common H-Bridge's that I saw on the net use some sort of BJT combination. Unfortunately I do not have the luxury of ordering more components that what you see in the circuit. Will the schematic work, or should I really go hunt for some new components?

Thanks for your comments..

Vijay

EDIT: Modified the schematic based on inputs is below,


texts: Intuitively, why does gain margin and phase margin infer instability in feedback system?

texts:
On MATLAB https://www.mathworks.com/help/control/ref/margin.html, gain margin and phase margin are additional gain in the system and additional delay in the phase of the system such that the system will be unstable.

Can someone explain with an example as to:

why increasing the "gain" of your system will cause instability,
why delaying a signal will cause instability? This doesn't seem to be very intuitive at all. Because if I delay my sine by 2π I get back my sine again.
How does gain and delay translate into physical components inside of a feedback system (say a circuit). Intuitively, a gain is an op amp, what about a delay?

Also, what does instability here refer to? Are we talking about the circuit going into oscillation or blow up behavior?


texts:
I'm working on an open source filter design where the PCB can be reused for many future designs. It is based around a Sallen-key filter since a few changes to the capacitors and resistors can change it from a low-pass to a band-pass or a high-pass. When looking at layout, I've realized it would be very beneficial to make the capacitor and resistor pads fit both larger (like tantalum caps) to smaller 0402 packages.

Is there anything I should be careful of while designing this 'universal pad'? Is it possible someone has built something like this already?


texts: Arduino flash trigger using laser and photodiode

texts:
I am trying to create a trigger for a high speed flash using an Arduino, a Sharp BS120 photodiode, and a laser pointer.

The results i've obtained so far are inconsistent, the system seems to miss small objects passing straight through the laser beam and also seems to have a significant delay, several millimetres worth of falling before the flash triggers.

Also, it seems to be insensitive to soap bubbles, which is what I need to trigger off.

Can anyone suggest a suitable circuit for this application.


texts:
I'm facing a dilemma on how to route correctly in order to minimize noise on a data signal line. In the example bellow there is a 2-layer flexible PCB (which is very thin). The copper layer is 1OZ and the routing is 5mil. Red is Top layer and blue is bottom layer.

The blue wires are connected to LEDS which turn on or off many times a second, max current is 10mA. The red is 3.3V 30Mhz data signal with no error correction or protection in the protocol, just plain data. I have no doubts that there will be errors and this is fine, I just want minimum errors.

What would be the correct way to route the data signal (red) in order to minimize the noise the blue routes generate on it? The examples below just show the principle, I can't really 'go around'.

This is a very limited design in space so I have no room for LVDS. I can only make the routes thinker or double them.

Thanks.


texts:
How do stud sensors actually sense current, what would cause the effect to propagate across an 8x8 foot surface area and remain strong enough to be detected?

I asked another group "what is happening", now I would like to ask your group "why".  This is a question about electrical sensors included on some stud sensors used in home repair to find wiring within walls. The garage for my home was built in 2000, the garage interior is naked particle board directly nailed to wood studs, and the insulation has paper backing (not foil).  When using the electrical sensor, most of an entire wall surface shows having current instead of indicating specific wire routes. Other walls in the garage do not show this effect. When I turn off the breaker for the outlets, the current disappears (so the reading is related to current flow, not a bad sensor).  What is the effect the sensor is designed to detect, and why might that effect propagate across the surface of one wall and not the (similarly constructed) other walls? Thanks.


texts:
I have a couple of moving heads like this They have a QCL (Quad color led chip) Theres a total of 10w. Most of the time I don't use the colors, I just use the white quadrant, which I presume is 10w. If I want a bright white I can turn on the R G & B quadrants as well but it gives a rather sickly white with weird colored edges.  I was thinking of replacing the QCL led with a single 10w White led. Obviously each color, R,G,B,W is controlled by a separate dmx driver. I'm just wondering would it be a very bad idea to join all these drivers together and solder them onto a single chip? I'm concerned about the output from one going into the the others. I can programatically be fairly certain to make sure that all the drivers are set to the same output at all times though but I can never be 100% sure!
What do you think?
Also on a side note, these lighting fixtures are rarely on for more than a few minutes at a time so well below their max in terms of overheating, would it be better to take the output from one of these RGBW channels and just use that with a transister to maybe drive a 20w or 15w white led chip?


texts: MATLAB filter designer giving out filters with huge DC gains

texts:
hope y'all beings safe out here and doing well.
I am trying to create a single stage biquad (2nd Order) butter worth filter using MATLAB's filter designer tool.
Just to see, I tried plugging back the filter coefficients that MATLAB give out into a discrete transfer function and then converting that discrete transfer function to a continuous transfer function using the "D2C" command using tustin just to see what I would get (Hopefully something close to what I designed).
Behold, I get roughly the same, but with a huge DC gain? I am curious as to where this came from?
Filter Coefficients:

Filter Designer Parameters:

Bode Plot of D2C:

Transfer Function (DISCRETE):

Transfer Function (CONTINOUS USING TUSTIN from D2C command):


texts: How to draw the input into the VCC net/bus in a circuit diagram?

texts:
I am currently drawing the circuit diagram for a device. To simplify the diagram I already using the ground symbol for all pins which are connected to ground. This makes the diagram much more readable.

But now there is a special power source (USB LiIon charger/power source) in the schema. It has various outputs, so I am currently draw all connections from the 5V output to the different components.

If I would use the symbol for VCC, it would simplify the diagram. But...

How do I show that the 5V output of the power source provides the power for all elements connected to the VCC (symbol)?

See this minimal example diagram:


texts:
I previously had a simple remote that allowed me to turn the LED strips on my motorcycle on and off when parked, which then I also wired in a separate relay so that the strips turn on with the ignition switch. The remote was switched on the positive line, so it made things easy. Never had an issue, it worked like a dream for the past 4 years.

I now have a 2 channel LED remote that has a function that alternates a strobe effect on the two channels. The remote is switched on the ground lines, not the 12v+. when I connect it up, and try the alternating flash setting, it doesn't alternate between the 2 channels, they both strobe at the same time.

I am trying to isolate the 2 channels using rectifying diodes, but I don't seem to have it right. I did up this diagram to show what I have now, thinking that the diodes would have worked in that configuration, but no joy. should the diodes be going on the 12v+ side?? Help me out please.


texts: Misunderstanding document about leakage inductance in a flyback converter V2

texts:
I m back again on this document ! :D The document teaches me a lot of things and I think it will help me to better understand the losses across the switching components. I really appreciate if someone could tell me if my reasoning is wrong. I spent a lot of time on this document !

Here it is : https://pdfs.semanticscholar.org/c061/313303ee8c231b069be4f0d67d9e4cddcbf0.pdf (the document is really insteresting)

Here are my questions :

Here are my questions :

"Ipeak is the current value when the switch opens" It means that the peak current through Lp and Lleak is maximal at the switch opening. According to Lenz's Law and Faraday's Law, if the current is going to be lower than Ipeak after the switch opening, then the voltage across Lp and Ll will reverse and the inductances will begin to discharge their relative energy previously accumulated during Ton. Do you agree ?

Nevertheless, it seems if I correctly understand the document that Lp and Ll are not reversed just after opening the switch. So the current through Lp and Ll must grow up and this current is provided by Vin as the energy accumulated into the inductance is still growing up.

We now have a capacitor which is connected to Vin, So Vin = VLp + VLleak + VClump. (Please tell me If i do a mistake, My reasoning is probably false). The slope of the current through Lp and Lleak will reduce as the voltage Vlp and Vleak will reduce as the voltage across VClump will increase. It will increase rapidly as Ip (=Ileak) is already high depending on the value of Clump.

So far, the voltage across the secondary winding was oriented so that the diode was not be able to conduct as Lp did not reverse his voltage. (energy was being accumulated and the current Ip was still growing up)

"The drain voltage increases until the voltage across Lp reverse" . Then "As both Lp and Lleak are energized, Lleak forces a current into the lump capacitance which continues its charge." What I have to understand ? The drain voltage continues to grow up so the the voltage across Lp is not reversed. Nevertheless it seems to be reversed there is a mention as "Lp and Lleak are energized". Besides, Lp is reversed as it is written " The secondary diode becomes biased". So at this moment, the current through Ip and Ileak goes down and the energy accumulated into the inductance is decreasing. When does Lp reverse ?

It seems that the voltage across Lp reverse when the voltage across VClump is equal to Vin. Vin source cannot more provide charge to the capacitor as its voltage is equal to Vin. So no energy is provided by the voltage source Vin and the inductance Lp and Lleak have to reverse as there is no more energy from the voltage source. The formula is obtained thanks to the Kirchoff's voltage law.

Then as it is mentionned, Lleak provides charges to Clump thanks to the energy accumulated previously. So the drain voltage is still increasing whereas the voltage across Lp is reversed. The drain voltage stop increasing when its voltage is equal to Vin + Vclamp.

Between the moment where VClump is equal to Vin and the moment where Vclump is equal to Vin + Vclamp, the energy into the circuit is only provided by the Lp and Lleak inductance. So the current through the secondary is proportionnal to Ip-Ileak. (No ?) As the two inductors was energetically charged with a current equal to "Ipeak" (E = 1/2*(Lleak + Lp)*Ipeak²), the current through the secondary at t = 0 (when the voltage across the two inductors reverse) is null as Ileak(t=0) is equal to Ip(t=0). At t=0+, the current Ip is different of Ileak and the current begins to rise at the secondary (Is this wrong ?). After a certain time the energy of Lleak and Lp has charged the Clump capacitor to the voltage Vin+Vclamp. And then the slope of current is constant as the voltage across Lleak is constant as it is mentionned.

Thank you very much :)


texts: Can a high voltage rated push-button switch be used on lower voltages?

texts:
I have a question regarding switch usage in a high voltage, very low current circuit (micro amps). Basically, we're taking the 120VAC out of the wall, converting it to DC (output can be either 5, 12, 15 or 24VDC) where it's going to a switch that is going to be the input to an SEL relay. Currently, it uses 120VDC as the input. What I want to know is can a push button with this high of a rating be used for a low voltage application? There are microamps going through so the power dissipated is <1W. Everything I've been taught tells me a push button will work regardless of the voltage running through it, as long as it's pushed (and the button switch isn't melted).

The button I'm referring to


texts: Why two N-channel MOSET instead of one P-channel?

texts:
Today I saw the schematic of a lenovo G480-la-7981p (download or download). On page 23 you can see this part:

I mean this part/configuration:

They've used two N-channel MOSETs instead of one P-channel. why?

Edit: Page of DMN66D0LDW


texts: ATTiny Circuit only works when connected to AVR ISP

texts:
I've got a very simple circuit (as you can see from the diagram below) with an ATTiny45 and a piezo buzzer. Everything worked great as I was testing it out and had the ISP (an AVR ISP MkII) attached. The piezo played the little tune it was supposed to, every thing was fine. But when I disconnected the ISP from the ICSP header everything goes haywire. The speaker just kind of constantly stutters. It almost seems like make it's constantly resetting but I'm not sure why. I tried placing a resistor between VCC and RESET to make sure it's pulled high, but that has no effect. I've also checked everywhere and there's no shorts that shouldn't be there.

Any thoughts of what the AVR ISP has that my circuit doesn't and obviously needs?

simulate this circuit – Schematic created using CircuitLab


texts:
We would like to add a BLE transmitter to our board so that it can serve as an iBeacon (and whatever the non-Apple equivalent is known as).

It seems like the engineers at Estimote and Stick n Find decided to settle with the NRF51822, which seems to be the "easy option". I've messed around with the NRF51822 dev kit myself and the wealth of samples make life a lot easier. Another competitor I've seen is the CC2543 but the power numbers from that chip don't look great.

However, given that we are looking into producing large quantities of our board, I was wondering if there were cheaper alternatives out there (even from the name brands?). For example, two areas that seem excessive are:

I've already got a micro on the board so I don't really need another SoC. A BLE radio would suffice.
Given that iBeacons are just transmitters, are there any BLE radios that do not have the RX capability (which would hopefully translate to lower costs)?


texts: Sub pf thin film capacitor vs capacitive t-network

texts:
I need very small capacitances to stabilize my high speed transimpedance amplifier.

This Burr Brown app note recommends using a capacitor t-network to achieve tunable, sub pF, capacitances on page 4: http://www.ti.com/lit/an/sboa035/sboa035.pdf

There is also the option to purchase single sub pF capacitors: http://datasheets.avx.com/Accu-P.pdf

Regarding tolerance, a single capacitor with 10% tolerance should be better than some product or quotient of 3 capacitors with 10% tolerance. I don't know if the single part is more expensive on its own, but having 1 part instead of 3 for pick-and-place machines saves money.

Are there other factors to consider, other than cost and tolerance, to choose the capacitive t-network or specialty capacitors for sub pF tuning?

Thanks


texts: Continuity testing - Why does swapping DMM probes give differing results?

texts:
Continuity query - Can anyone explain this?

Circuit is a simple 12v DC, wired as follows -battery pos to bulb to spst switch back to battery earth. Testing with DMM in the dedicated audible continuity mode.

With switch open, all points from battery pos up to the switch read continuity as one would expect.

If one closes the switch (live circuit) repeating the above test gives a negative, no continuity result - which i understand to be correct as continuity testing should be done on non-live circuit.

BUT... if I then swap the DMM probes over (neg DMM to Battery pos) (still on live circuit) all points on the circuit now read continuity (beep)

Also this situation occurs just testing across battery terminals - pos to pos and neg to neg no continuity, but swapping so DMM neg to battery pos gives continuity.


texts: Deciphering Mux/Demux/Switch Nomenclature: AxB:C?

texts:
I'm looking through Digikey's Interface - Switches, Multiplexers, Demultiplexers section (and, thanks to W5VO, the Logic - Signal Switches, Multiplexers, Decoders section as well), and I'm having trouble deciphering what circuit/topology I need.

I've got a processor with a 32-bit coprocessor interface, and I'd like to interface it with a parallel Flash or RAM chip.  Ideally, I would have both, and could swap between the two in software.  I imagined (wrongly, it appears) that this would be a fairly common need, and that I could buy a pair of ICs that would each break out 16 inputs into 2 banks of 16 outputs, with power, ground, a single channel select pin, maybe an enable/high impedance pin.  This would ideally come in a 54-pin TSSOP or 64-pin QFP or something of that size. A 32-switch chip would also work, but I imagine that two switches would make routing the a bit easier. The interface would be digital (I don't really need an analog switch), and I'd like to keep up with the 150MHz maximum speed grade of my processor (but will settle for 72MHz or so of actual performance). I am confident that I don't need some of the $200+ crosspoint switches!

I imagined that this would be a simple task, but it seems that my idea of what AxB:C should mean is different from Digikey's idea.  I thought that the options would include 1x16:32 or 16x1:2, but (1) these options are not available at reasonable prices (I don't see why this device should cost $70 or $234!), and the other options (like 8x2:1, which seems popular) are designed for analog switching of Ethernet signals.

 Where can I learn about the mux nomenclature?  (An answer on this site would be ideal :)  Also, where can I learn about the various functions listed, like AV/crosspoint/Ethernet/USB?
 What topology or function should I use for to do this task (digital, ~100MHz, 32 or 16 lines)?
 If all else fails, how can I build a switch out of discrete components or transistor arrays?


texts: Does the frequency response \$H(j\omega) \$ exist for system with unstable poles?

texts:
This question arose from a discussion between me and TimWescott in the comments here. The question is:

Does \$H(j\omega) \$ exist for systems with poles in the RHP (unstable poles)?

My own answer to this question is no. If there is even one pole in the RHP, then the Laplace integral doesn't converge for \$s=j\omega \$, the system is unstable and \$H(j\omega) \$ is meaningless. A quote from signal processing and linear systems by Lathi seems to support me.

Math example
Say we have a system \$F(s)=\frac{1}{2-s} \$ with a pole at \$s=2 \$. In the time domain this function is \$f(t) = -e^{2t} \$. Let's try to evaluate the Laplace integral for this function.
$$F(s) = \int_{0}^{\infty}f(t)e^{-st} \: dt= \int_{0}^{\infty} -e^{2t}e^{(-\sigma-j\omega)t} \: dt$$
$$F(s) = \int_{0}^{\infty}-e^{(2-\sigma-j\omega)t} \: dt $$
If we want to find the frequency response for the system, we need to evaluate the integral on the imaginary axis, where \$\sigma = 0 \Rightarrow s=j\omega \$.
$$F(j\omega) = \int_{0}^{\infty}-e^{(2-j\omega)t} \: dt $$
As can be seen, we end up with a growing exponential term inside the integral, and \$-e^{2t}\rightarrow -\infty \: \text{for} \: t\rightarrow \infty \$ which causes the integral to not converge, and therefore \$F(j\omega) \$ is meaningless.
It might be that my reasoning is wrong, and if so, I would appreciate being corrected. I just want to understand the premise and prerequisites of the Laplace transformation.


texts:
I have to program an 82S23.

There is surprisingly little documentation on how to do this. There are datasheets that will tell you how to read it, but not burn.

I built one following these specifications, but after programming, the bit would stay low. In addition, application of the high programming voltages actually causes the PROM to heat up. I actually fried one by holding the program button down too long.

Any advice?


texts: A question about selecting and using a fully differential amplifier

texts:
I have a unipolar but balanced/differential output transducer. The transducer outputs around +/-200mV and I want to amplify this with a gain of at least 10. The data acquisition board is also differential inputs.

Now I want to amplify this balanced transducer signal and obtain again a differential/balanced signal at the output with gain of at least 10.

I found this differential amplifier, but it seems it is not fully differential. But it is great that it has inner gain so no gain temperature issues. But its output is single ended I guess (?)

My problem is I want a fully differential amplifier(with diff outputs) in DIP package which can work any dual supply voltage between min +/-5V up to max +/-15V.

But I couldn't find a single one in the market. Does anybody have experience with that? My frequency of interest in this force transducer application is from DC to 150Hz.

The best would be of course fixed gain fully differential amplifier in DIP package, otherwise resistive networks(which are also not DIP) to eliminate temperature effects on gain or CMRR needed.

(How about using a single ended to differential ended driver after this INA106. My problem is I'm restricted with supply rails and DIP package?)

Edit:


texts:
I live in Brazil, our residential electrical outlets are 127 VRms, 60 Hz.

So if I were to plug a fan (AC motor, forget anything DC) into the socket and then I were to "ride an electron" that's at the interface socket/fan cable what would I see?

EDIT to make my question more explicit: A car very simple converts the energy from the chemical bonds into kinetic energy.

What is the "chemical bond" of the power outlet?

Does the electromagnetic field get a tiny bit weaker/"consumed" by the AC motor?

The electron can't lose mass. Can't lose charge. Can't travel more in one direction than the other. Is it something in the electrical-magnetic wave permeating the wires? Does it have something to do on a quantic level?

PS: I did 4 years of chem engineering grad and transferred to electrical engineering (currently at the 4th year with an "focus" on computer engineering), so I have good theoretical concepts of power, energy, voltage, current, transformers, generators/motors, thermodynamics, ..., and some knowledge of basic quantum physics/chemistry.


texts: What happens if you feed 3.3V to a 5 to 3.3 voltage regulator?

texts:
The PCB circuit I'm using expects 5V input voltage which it then converts to 3.3V using an AMS1117-3.3 voltage regulator. The power supply I'm using is 3.3V. What happens if I feed the 3.3V to the input of the 5 to 3.3 voltage regulator?

The input of the voltage regulator has an easily accessible jumper header. Whereas bypassing the voltage regulator would require the use of bodge wires. Can I get by with just feeding the 3.3V into the regulator? What are possible drawbacks if it even works? What would happen when the PSU voltage drops below 3.3V (as I doubt it will provide a precise and constant 3.3V)?


texts: How do I determine the inductance of a circuit using Op-amps, Capacitors and Resistors?

texts:
I am trying to prove that the inductance of a given circuit (between the source A, and ground) (see image below) is equal to (R1*R2*R4*C)/R3.

Under the assumption that it is an ideal op-amp, I know that the input to each of the op-amps is equal to the input voltage (A), and that there is no current entering.

I've attempted nodal analysis, but my main issue is that I don't know the current leaving either of the op-amps, and I can't find any information regarding a circuit like this one on the Internet.

On top of that, I also cannot figure out how to tackle the capacitor, so any advice regarding that would also be greatly appreciated.

Finally, the circuit is supposed to result in being equivalent to an inductor, L = (R1*R2*R4*C)/R3 , and that is what is required to prove.


texts:
Do we use IQ modulation because quadrature signals are a good physical implementation of phasors - or is it the other way around?
To elaborate a little:I'm having a hard time getting a clear explanation of we do things this way in radios. I can see that IQ signals and phasor representations go very well together. I understand that a pair of quadrature signals are needed to represent a rotating complex exponential as real values, and that modelling signals as complex exponentials is useful because when you multiply them, the phases add. It's all very elegant, but it doesn't fully explain why we do it this way. Why not make do with real functions for modelling, and use simpler mixers in the real world? I see 2 competing explanations:

We use complex exponentials because they're the simplest way to model a pair of quadrature signals from the real world. This raises the question of why we like quadrature signals in the real world in the first place.

We like quadrature signals in the real world primarily because that allows us to model things using complex exponentials.

Unfortunately no matter how hard I search and no matter how much I read, no source will commit to one of these explanations as the main reason for the whole thing. People tend to drop hints that it's a little bit of both, which is very unsatisfying. I'm not saying that it can't be partly both, but would one of these be enough on it's own? And if so, which one?
I know there is a real-world advantage to IQ modulation, in that it doesn't produce duplicate sidebands, so it's more efficient in terms of bandwidth. Is that it? Is that the fundamental motivation behind the whole thing?


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I am trying to create RF module using the nRF24L01P. I am trying to maximize the range while still using a trace antenna. My plan is to combine the simple trace antenna design with the long range antenna design.
Short range nRF24 Module

Long range nRF24 Module

My understanding of the long range design is that it uses a rf amplifier to increase the signal power before sending it through the antenna. What I am hoping to do is keep the trace antenna from the first design but then put the amplifier bettween the antenna and nRF24L01P. Is it feasable to replace a typical SMA antenna with a trace antenna in this way?
Here is a copy of my design. Is there anything else I need to be doing to preserve as much of the range as possible while still using a trace antenna? Also is there a particular type of PCB substrate I need to be using or will just a standard substrate work?


texts: Railway overhead lines: What happens to other two phases in single phase railway power?

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This is actually two questions. As my imagination I have the German/Swiss/Austrian/Norwegian/Swedish railway system on mind (15kV, 16.7Hz). I think conceptually the problem is the same on other AC systems.

So in order to operate a overhead AC system one must produce one phase AC power. Usually generators will however generate 3 phases of electical output. But for such a system you need only one. And it is understatement that a generator or 2-phase system must be operated with symmetric load. The problem with this system is that the system uses 16.7 Hz frequency (which is not equal to the mains grid with 50 Hz)

So what happens to the other 2 phases that are not used?

Secondly: Is the railway net actually running phase symmetric in all it's separate sections? Or could it be that sections are driven with phase difference (so to say the other phases)?


texts: High output of NCP5104 (half bridge driver) is active in dead time zone. How can I solve it?

texts: I try to drive BLDC motor. I have a problem in gate driver circuit. I use three NCP5104 gate driver. NCP5104 has 520ns internally fixed dead time. "The dead time is the time between the high side and low side output signal to avoid any cross conduction."@Delphesk But in my circuit, high output of NCP5104 (half bridge driver) is active in dead time zone. How can I solve it ?