texts:
I am using a TFT display with ssd1963 controller built-in and stm32f4 discovery board, and everything is working well except when writing to the display.
There is a significant increase in system noise and it is actually
audible on the codec output and also effecting my ADC readings.

All pins are configured correctly and as I mentioned display is working very well.
I am driving the display controller from the stm32f4 with 150R resistors because I saw this used in a schematic for a dev board with a TFT. I assumed the resistors were used to terminate the tracks to help with track ringing and impedance, but perhaps they are used to limit current.

Has anyone else seen problems with TFT displays and data pin noise?

Would putting an array of transistor buffers between the micro and display help as long as the buffers where given it's own regulator to keep noise out of the main power supply?

With these kinds of projects making changes like this are not trivial so looking for possible suggestions before busting out the soldering iron


texts:
I've heard you can go faster in one direction if you adjust the timing, but do not understand why?  I have a sensored bldc motor with a 30deg shift of the hall-effect sensors, tried going forward (CCW looking into motor face plate) at 95% duty cycle and pulls about 6A.  Tried going in reverse (CW) at 95% duty cycle and it begins pulling ~15A before I pull the battery plug as quickly as I can.  I also tried going at 80% duty cycle in both directions and things seem normal.  There seems to be a dangerous threshold that I can cross going one of the directions with timing.

Are there any disadvantages to having 0deg-timing?

I scoped the gate drive lines and everything is as expected -- no shoot through, looks same as waveforms when going forward.  It would seem that something is shorting but I am not sure how.

Why might a ton of current all of a sudden be drawn for only one of the directions at the same duty cycle?


texts: What is the difference between rectifier/signal diode and zener diode?

texts:
I need to caution: I'm absolutely beginner in electronics! :) I'm stacked with the difference between rectifier and zener diodes. I've already read all the answers at https://www.quora.com/What-is-the-difference-between-a-diode-and-a-Zener-diode, but still have some significant doubts..

When I search for diodes on aliexpress there are always difference in how the parameters of rectifier and zener diodes are specified (by provides that sell them). For example, some shops specify only amperage and voltage for rectifier diodes (eg 5A/100V). When it comes to zener diodes, they specify only watts and voltage (eg 0.5W 10V). Why?

As I understand the principle differences are (1) Zener diod can conduct current in opposite dirrection without damaging, when Vz is reached and (2) the maximum reverse voltage of rectifier diod (before it will burn out or conduct and burn out anyway) is much higher. Also I have assumption that Zener diod conduct only specified/rated voltage in contrast to rectified. It will be great if somebody shed light on V/A/W properties and their differences on each type.


texts: would like to verify a filter design I need to make for a backup camera in my truck

texts:
I am installing a backup camera in my truck. I am getting some source of electrical "noise" in the electrical system in my truck and its not allowing the backup camera to operate. Let me explain a little further. (thanks for your patience)

Installed the head unit and backup camera in the truck, Head unit is pretty standard, it has a 12 volt (+) input to trigger the head unit to "see" that the truck is in reverse.
the camera is connected to the head unit via an RCA cable with an additional (+) and (-) line included.
at the camera end of the RCA line there is (+) and (-) tag ends hanging out that you are to connect to the reverse light harness on the truck.

Basically when you put the truck in reverse, the power is also tapped to the camera, when the camera is powered it sends a (+) signal to the head unit and it flips the screen over to the reverse camera automatically.

When the truck is off but key in the on position and I put the truck in reverse the camera works not a problem. When I start the truck and put in reverse the screen simply goes to the yellow ! on the screen. According to the manual they are saying its because there is interference with another signal. Im assuming at this point its with the alternator or something with the engine running.

In the installation manual they have a pic of a filtering circuit.

I believe that in the diagram has the polarity on the capacitor is incorrect? Should not the negative lead of the capacitor be on the negative lead of the 12 volt circuit?

In my local electronics store I could only get a 3300 uf cap but I believe this should be ok in this instance.

also to verify please the band on the diode should be toward the backup camera correct?


texts: SL8051 UART Data is Garbled Every Few Attempts

texts:
I have about 1500 samples stored in memory from an ADC on a SL8051 development board. When compiling these values into a CSV form to send over UART, the transmission is successful about 3/5 times. The other times it is completely garbled. The baud rate is the same on both sides, and we've checked that the UART sent is consistent with other receiving devices.

Acquisition code

 //Code to aqcuire from ADC
    void main (void)
    {
      // unsigned char delay_count;          // Used to implement a delay
      // bit duty_direction = 0;             // 0 = Decrease; 1 = Increase

       // Disable watchdog timer
       WDTCN = 0xde;
       WDTCN = 0xad;

       PORT_Init ();                       // Initialize crossbar and GPIO

        OSCILLATOR_Init ();
       PCA0_Init ();                       // Initialize PCA0
       EMIF_Init ();                        // Storing ADC samples in SRAM

       SFRPAGE = CONFIG_PAGE;

       RAM_CS = 0;                          // assert SRAM chip select

       UART0_Init ();                       // initialize UART0

       Timer3_Init (SYSCLK/SAMP_RATE);      // Init Timer3 for 100 ksps sample rate

       ADC0_Init ();                        // configure ADC0 and ADC1 for differential measurement

       EA = 1;                             // Globally enable interrupts

        while(1)
        {                           // loop this logic for multiple samples

           while(BB_GPIO_INPUT == 0);

           SFRPAGE = TIMER01_PAGE;
           TR0 = 1;
           DMA0_Init ();                        // configure DMA to move NUM_SAMP samples

           SFRPAGE = UART0_PAGE;
           //printf ("Data Acquisition in progress...\n");

           SFRPAGE = DMA0_PAGE;                 // Switch to DMA0 Page

           while (!(DMA0CN & 0x40));            // Wait for DMA to obtain and move ADC samples

           SFRPAGE = LEGACY_PAGE;
           //printf ("Data Acquisition complete.\n");
           SFRPAGE = TIMER01_PAGE;
           TR0 = 0;
           while(BB_GPIO_INPUT == 0);
           SendData();                          // Send data via the UART0

        }
    }

UART Code

//Code to print the data from DMA
 void SendData (void)
    {
        unsigned int i;
        char old_SFRPAGE = SFRPAGE;
        SFRPAGE = UART0_PAGE;

        read_ptr = XRAM_START_ADD;   //pointer at beginning of data

        for (i=0; i<NUM_SAMPLES; i++)
        {
            printf("%u",*read_ptr);     // send data as unsigned integers
            putchar(',');
            read_ptr++;
        }
        printf("\n");

        SFRPAGE = old_SFRPAGE;
    }

UART Init

void UART0_Init (void)
{
    char old_SFRPAGE = SFRPAGE;

    SFRPAGE = UART0_PAGE;           // Switch to UART0 page

    SCON0 = 0x50;                   // SCON: mode 1, 8-bit UART, enable RX
    SSTA0 = 0x10;                   // Timer 1 generates UART0 baud rate and
                                    // UART0 baud rate divided by two disabled

    SFRPAGE = TIMER01_PAGE;         // Switch to timer 0/1 page

//  TMOD = 0x20;                    // TMOD: timer 1, mode 2, 8-bit reload
    TMOD &= 0x0F;                   // clear all T0 control bits
    TMOD |= 0x20;                   // 8-bit auto-reload timer

    TH1 = -(SYSCLK/BAUDRATE/16);    // set timer 1 reload value for baudrate
    TR1 = 1;                        // start timer1;
    CKCON |= 0x10;                  // Timer1 uses SYSCLK as time base
    PCON |= 0x80;                   // SMOD = 1

    SFRPAGE = UART0_PAGE;           // Switch to UART0 page

    TI0 = 1;                        // indicate TX ready

    SFRPAGE = old_SFRPAGE;          // restore SFRPAGE

}


texts: Help identifying connector on vinyl shellhead

texts:
I'm working on a DIY project where I'm basically creating/connecting my own vinyl record player arm.

I have one of these shellheads in the picture below. Ideally I wan't to be able to use this, and also use the connector show, without soldering cables directly onto it. Is this a regular type of connector, which I can buy the female part of? If so, what is it called? It looks like a short DIN connector, but the pins are perfectly squared, which DIN isn't.

Thank you!


texts: Current capacity of very thin (0.1mm ~ 0.5mm) copper wires?

texts: I am looking at this very thin copper wire. It does not have much description other than the physical dimensions. What's the maximum current capacity of these wires? I guess they are not for power wiring (~ 200mA)?


texts: Passive Cell Balancing of an 2S3P Battery Pack

texts:
I'm currently attempting to design a passive cell balancer for a 2S3P battery pack (pictured below).

Being new to power engineering I'm not sure where to start looking; I know I want to go with a "resistor bleeding balancer" design but that's about it. I'm looking for a recommended IC or design for a battery pack in this configuration and chemistry (LiFePO4). Also I'm not sure how I'd wire the balancing leads to the battery pack as shown too; can anyone point me in the right direction?


texts: Why do trolleybuses power cables use DC and not AC?

texts:
I am interested in multiple aspects of trolleybuses as a way of transitioning from fossil-fuel powered buses to "green" public transport.
I am not an electrical engineer myself but I do have an, albeit limited, understanding of electrical engineering.
Reading through the specifications of available trolleybuses, it seems like the standard way of transmitting power to them is through DC (600V) wires. From what I know, transmitting current over long(er) distances is more efficient using AC.
What is the reasoning of using DC for power transmission in this case?
Is DC power transmittion in this case more efficient (no heavy power converters inside the vehicle; cheaper to produce DC motors; more efficient DC motors etc.), safer for the pedestrians, or just legacy?


texts: Purpose of laminations crossing squirrel cage induction motor rotor bars

texts:
Below is a squirrel cage induction motor's rotor and on the left shows only the shorted aluminum rotor bars; and on the right it shows the lamination disks are added to the rotor.

As far as I know the rotor can still rotate(as on the left) without those laminations. Those shorted bars are actually the structure which creates rotation. They form coils and pass currents and hence create torque and rotation ect.

But why are these limitations(on the right side) needed in construction of the rotor?


texts: Automatic power switching, grounds not connected

texts:
I'm currently working on a project that requires a 24V DC input. That is no problem, as I have that power supply available. However, the project should also remain working when the supply fails or becomes unavailable. For that, I want to automatically switch to the backup supply. This will most likely just be a battery, but can also be another generator.
There are a few ways to switch from power input automatically, but there is one important rule that I have to follow in this sector: the grounds may not be connected.
This, for example, is no solution because of that rule.
What would be the best way to tackle this?


texts: Step by step working of PN junction diode

texts:
In a PN junction diode, as far my understanding, when we apply a forward bias, the free electrons from n type material will cross the junction and then it will again recombine with the holes of p type material. And hence the p type material will become more negative. So in this situation if any remaining  free ectron from n type material wants to cross the p type material to reach the positive terminal of the supply then it needs more energy comparing to that was required at the beginning when there were only few electrons(only in the depletion region)??
In some places I saw that all the electrons will not recombine during crossing the p type material, but why so?


texts: Schematic representation of AGND and DGND in a shared ground plane design

texts:
I've seen many questions asking how to connect AGND and DGND in a schematic, and the usual answer is to use some kind of net tie component with a physical footprint (and to approve the resulting overlap DRC violation).  While rather hacky, this seems fine for a star- or segregated-ground design with a single point connection.

However, this doesn't really help in a "shared" ground plane design, in which there's no single point of connection between distinct ground planes, and instead relies on the physical distribution of devices and traces to keep AGND and DGND return paths apart in a single undifferentiated ground plane.

My question is, is there a way to represent this in the schematic, other than using a single undifferentiated GND net and relying on e.g. ad hoc annotations, separate sheets, etc to identify the distinct placement/routing domains?

I'm asking specifically about Eagle, but it would also be interesting to know what kind of support higher-end tools provide in this regard.

EDIT: To clarify, I'm specifically asking about a design that follows the principles laid out for example in this article by Henry Ott.


texts: Do we need to get certified from UL if we have certified from IEC to sell a electric/electronic product in the US market?

texts:
A inverter/charger has EN-IEC 60335-1, EN-IEC 60335-2-29, IEC 62109-1 but is not certified by UL standard.
So isn't the UL mandatory?


texts: Inrush Current Depends on the Power Supply Rise Time

texts:
I have a query.
I understand that the inrush current is the current that appears during the initial turn ON of the Board so as to charge all the Capacitors present in the board.
But I think that, this initial inrush current not only depends on the capacitors that are present on the board, but also the Power Supply rise time.
I found that there is a difference in the inrush current values when my power supply rise time is 300us and when my rise time is at 100ms.
My questions

What should my the actual power supply rise time be so as to calculate the maximum initial inrush peak current of my board? Is there any sort of standard regarding this Power Supply rise based on application?

Based on the power supplies which one is using, power supply rise times tend to differ. I assume it is due to the presence of the capacitors at the outputs of the Power Supply.
In real life, my PCB board runs on a 12V Lead Acid Battery. How to simulate the Power Supply rise time of the Lead Acid battery using a normal 32V/5A power supply.

How does the inrush current vary when one uses a Bench Power Supply and when one uses a 12V Lead Acid Battery.


texts:
I was trying to implement a simple D Flip Flop using 2 multiplexers.

Are there any errors in design?
Do you have any other suggestions about design? Thanks.
Update:
As you'd recognise I've not implemented the clock signal yet.
I used this example when designing the circuit.

There are two latches. When C=0, Q holds its old value Q' follows the input D. When C=1 Q' holds its old value Q follows Q'.


texts: How to detect movement of gadget without electricity

texts: I'm trying to make a device which needs to be turned on when it's picked up and might sit in standby for several weeks before getting picked up. Right now I'm considering using a Photo resistor at the bottom of my device or using a piezoelectric sensor for this purpose, but both of them use electricity and might drain the battery before actual usage of the device. Is there any other way for a device to detect its own movement without draining its battery?


texts: "expecting endmodule" error, can't understand why?

texts:
I'm trying to build a counter with a-sync reset, that will be shown on the 7-segment display on the fpga board.
I saw a few posts about my problem:

  "near text "if"; expecting endmodule"

But still I can't understand  why I'm getting that error, I know that I am missing an important rule, but I can't figure it out.

module up_counter(
input clk,rst,
output segA, segB, segC, segD, segE ,segF , segG, segDP);
reg [3:0] BCD;

always @(posedge clk);
    reg [7:0] SevenSeg;
    if (BCD==4'h9) begin
        BCD <= 4'h0;
        SevenSeg = 8'b11111100;
    end else if (rst==0) begin
        BCD <= 4'h0;
        SevenSeg = 8'b11111100;
    end else begin
        BCD <= BCD+4'h1;
        always @(*)
           case(BCD)
              4'h0:SevenSeg = 8'b11111100;//0
              4'h1:SevenSeg = 8'b01100000;//1
              4'h2:SevenSeg = 8'b11011010;//2
              4'h3:SevenSeg = 8'b11110010;
              4'h4:SevenSeg = 8'b01100110;
              4'h5:SevenSeg = 8'b10110110;
              4'h6:SevenSeg = 8'b10111110;
              4'h7:SevenSeg = 8'b11100000;
              4'h8:SevenSeg = 8'b11111110;
              4'h9:SevenSeg = 8'b11110110;
           default: SevenSeg = 8'b11100000;
           endcase
    end

assign {segA, segB, segC, segD, segE ,segF , segG, segDP} = SevenSeg;

endmodule

This "always" addition came after , I read that case and if statments need to come with always,but this didn't help.
   always @(*)
   case(BCD)
Furthur more, i tried to put an "always" before the :
    if (BCD==4'h9) begin
But then I got the same error:

  "near text "always"; expecting endmodule"

I feel so limited, because at this moment every time I had an "if" , I get an error, so I'm missing here a serious and basic rule.
Thanks a lot,I really appriciate your help.

Thank your all for your help, I think I did , every imporve you gave me, and this is the improve code:

module up_counter(
input clk,rst,
output segA, segB, segC, segD, segE ,segF , segG, segDP);
reg [3:0] BCD;
reg [7:0] SevenSeg;

always @(posedge clk)
begin
if (BCD==4'h9) begin
   BCD <= 4'h0;
   SevenSeg = 8'b11111100;
end else if (rst==0) begin
   BCD <= 4'h0;
   SevenSeg = 8'b11111100;
end

else begin
   BCD <= BCD+4'h1;
   case(BCD)
     4'h0:SevenSeg <= 8'b11111100;//0
     4'h1:SevenSeg <= 8'b01100000;//1
     4'h2:SevenSeg <= 8'b11011010;//2
     4'h3:SevenSeg <= 8'b11110010;
     4'h4:SevenSeg <= 8'b01100110;
     4'h5:SevenSeg <= 8'b10110110;
     4'h6:SevenSeg <= 8'b10111110;
     4'h7:SevenSeg <= 8'b11100000;
     4'h8:SevenSeg <= 8'b11111110;
     4'h9:SevenSeg <= 8'b11110110;
     default: SevenSeg <= 8'b11100000;
endcase
end
end
assign {segA, segB, segC, segD, segE ,segF , segG, segDP} = SevenSeg;

endmodule

It did resolve the problem I had, but now, I get only 8 in the 7-segments display, is there any more rules Im missing.


texts: Connecting antenna directly to RF module

texts:
I have a general question regarding the connection of an antenna to a RF module like GPS receiver or 433 MHz TXD:

Is a direct connection of an antenna (e.g. GPS ceramic patch) to a module preferred over the regular solution to use a 50 Ohm PCB trace? Or is there more signal reflection, attenuation or other negative impact?

Practically it would look like to have the RF module on the bottom of a PCB and the antenna wire would be fed from the top through a via directly to the antenna pin of the module.

Thanks!


texts:
What are the best options to show a line of text on a LilyPad Arduino, probably using a matrix of LEDs? Are there any thin and inexpensive displays?

The main problem is that the only things I can find on the Internet are around 8x8, but I need much more than that (about 4x40). Also, the number of pins on the LilyPad seems insufficient, but I might be wrong (I hope so) :)

Can anyone help me out? Thanks in advance.


texts: I have a pulse which varies between 500 Hz to 100 kHz where the quantity I need is the mark space ratio, I'm not interested in the frequency here although it must affect the design. What I've come up with is the sketch below. I think it should work but my math is rubbish, I have no idea how to calculate the values, can anyone help?


texts: Are breakaway headers the standard for interfacing when prototyping with these holes?

texts:
I have a board which has these holes in them for interfacing with other components. I would like to reuse this board in the future for other uses.

Is soldering breakaway headers onto these holes the standard for prototyping? If not, what other options do I have and where can i buy it?

Breakaway headers sold at SparkFun.


texts:
I am creating a non-profit product for charity and I have a simple electrical question.

I plan to place a small single cup immersion water heater inside a stainless steel cup. But I am going to have a plastic safety cover that goes around the outside of the cup. And a sticker on the cup that says "Be careful not to touch the water or metal cup, while the heater is in use."

Does this sound safe enough to sell on ebay and amazon?

Thanks so much for any advice.

ps: I live in Thailand, so it might take me a while to answer any questions, cause of the time difference.


texts:
I trying to find a low-power processing unit with lowest price for some practical research. I trying to made a simple device with 1 SATA 3.0, 1 microSD and 1 USB 3.0 interfaces.

Can someone advise where I can search such CPU by such parameters?

I'am a newbee in PCB design, but I'am very interested in this field.


texts: Trouble with rectifying a pulse with a diode

texts:
I'm trying to obtain a pulse from a square-wave of a function generator.
I thought it is an easy straightforward thing.
So in this case the square-wave is +5V to -5V. I use a 1N4001 diode and a 220 Ohm series resistor.

As you see in the below simulation output will go to a comparator's input. Green plot is the output voltage (Out):

(V1 represents the function generator)

But I'm having those negative spikes during falling edges both in scope and in simulation.

My questions are:

1-) How can I prevent those negative spikes? I need around zero volt during OFF time of the pulse without such spikes. Why do these spikes occur?

2-) Is 220 Ohm okay or better to use 50 Ohm? (Im asking because at the output of the function generator it is written 50 Ohm)


texts:
I own a small data logger for recording accelerations. The data logger is a Slam Stick X with integrated 250mAh rechargeable battery. My problem is that the capacity of this integrated battery is far too small for my projects. I intend to use a battery pack with 40,000mAh.
Since the Slam Stick X has an USB port I could use a big power bank as one can use for mobile phones, tablets and so on. Unfortunately all of the power banks I found have an auto shutoff function when drawing too little electric current. When my Slam Stick X draws too little power (for example in standby mode waiting for a trigger event) the power banks automatically shut off.
MIDÉ, the manufacturer of the Slam Stick X, recommends the usage of the power banks from Voltaic Systems. They have an ‘Always On’-Mode implement that means that they don’t have a low current shutoff. See the following link for further information: Always-On mode by Voltaic Systems
But the biggest power bank they have just has a capacity of 19,200mAh. Not even half of the capacity I want to use.
My idea now is to build a power bank by myself. I think it is most practicable to use the 18650 batteries from Panasonic since they are not expensive and available everywhere. To reach the 40,000mAh I need to connect twelve 18650’s in parallel. A step up converter can increase the voltage to 5V so that I can power the Slam Stick X via its USB port.
I need help to put my little electrical project into practice.

Is it safe to operate a Li-Io battery in ‘Always-On’-Mode or do I need to observe safety precautions?
I have found out that a lot of Li-Io charger ICs exist. They have mostly overcharge and over-discharge protection implemented. Which one should I use that does not shut off when drawing low current?
Maybe I would like to increase the capacity with more battery cells. Is this easily possible?

I would be very thankful if you could support me and give me some advice. Thank you very much.


texts: Bit bang ATmega328 with Arduino bootloader using AVRDUDE

texts:
I have an Arduino Uno development board with a blank ATmega328 chip (no Arduino bootloader. The chip that came with the unit is soldered in a separate stand-alone project so that I can use the Arduino board for more than one instance :) )

So looking here, the Uno isn't able to program the chip as it cannot be used as an ISP (yet?).

Would I be able to use AVRDUDE in a bit-bang programmer mode and hook up the ATmega's SPI lines to my serial port (using the correct lines obviously) and program the bootloader? I've seen topics on the web that say this is possible to do with other AVR chips, but I'm just really a noob here trying to get by. I understand that I can purchase an AVR ISP for ~US$20 to do so, but I was hoping to get started on a project tomorrow/tonight and do not want this weekend to go wasted (waiting for it to arrive...).

Anyone have a good reference on how to proceed?

To clear up some confusion, I am trying to program an ATmega328 with an Arduino bootloader. I only have the Uno development board and a blank ATmega328. I do have a serial port and really do not want to wait for an AVRISP to come in as I would like to get started sooner rather than later. Is this possible with the ATmega328? How would I proceed?


texts: Choicing crystal or external oscillator for time critical project on PIC18F

texts:
Need to learn how making frequency counter (or any time critical project) using PIC18F that display output over USB.

Having choice of 3 clock sources:

±50ppm 4.0000 MHZ crystal ATP040SM

4.0000 MHZ 20PF SMD ±50ppm

http://www.ctscorp.com/components/Datasheets/008-0325-0_A.pdf
±50 ppm 24.0MHZ external oscillator

XO-54D-24.0MHZ

±50 ppm

http://www.vishay.com/docs/35025/xo-52.pdf
±100 ppm 40.0MHZ external oscillator

MXO45-40M000 Manufacturer: CTS CORP

40 Mhz

±100 ppm

http://engineering.dartmouth.edu/courses/engs031/databook/oscillator.pdf

To run internal PLL PIC18F will divide clock input by PLLDIV that can be setting to either 1, 6 or 10 for above options respectively.

I thinking which option providing best stability?

When thinking myself, I feel 3rd option will be best as I reasoning that ±100 ppm 40Mhz clock will be divide by 10 and hence effectively behaving like ±10 ppm 4Mhz clock?

Or is reasoning wrong and ±100 ppm 40Mhz clock after divide by 10 is effectively still ±100 ppm 4Mhz clock?

If you, experienced designing having choice of above 3 - which one you choose and why (no consider PCB space or 5V voltage issue in 3.3v world, but might consider cost only between more expensive ±50 ppm vs less expensive ±100 ppm)


texts: How to detect 3 way slide switch positions?

texts:
With one of this 3 position 8 pin slide switches, I want to detect all three positions:

Required function:

Position 1: Node1 to ground
Position 2: None
Position 3: Node2 to ground

If I pull an digital I/O pin HIGH and connect it after SW2, HIGH means position 1 and LOW means position 2:

simulate this circuit – Schematic created using CircuitLab

Can't connect another digital I/O pin to any of the nodes (I have spare I/O pins but nodes voltages are higher than 5V. even if I use a voltage divider, I can't get an Ideal HIGH from them because their voltages will vary) and nodes shouldn't be connected to each other.

How can I detect all third positions?


texts: Durability of SMD MEMS pressure sensors in pure oxygen enviroment

texts:
I have a question regarding durability/reliability of COTS SMD mems pressure sensors in oxygen rich (basically 100%) atmosphere under pressure of 1bar/1atm and temperature around 20C/293K.
Sensor which might serve as example is BMP280 from Bosh.
In theory it should work fine, because according to my research, top layer of sensing layer is silicon oxide.
Also very related to sensor are its connections to rest of circuitry. How proper reflow solder joints and generic solder mask react with oxygen rich atmosphere?


texts: Slow turn-off time on PNP when driving 7 segment led

texts:
I know that there has already been question about optimizing PNP turn-off time, but my circuit is a bit different from that question so the solution presented there does not seem to work for me. Here is my circuit

I use MAX7219 to drive this circuit. The MAX7219 digit output is inverted by CD4069 so it can drive the common anode 7 segment that I have. D1 represents segment A, D2 represents segment B, this configuration continues up until segment G.
The problem that I have now is because MAX7219 scanning time is at about 800Hz for 8 Digits display, the PNP 2N3906 does not turn off fast enough, so there is ghosting on the display. Here I have tried measuring the 2n3906 collector voltage on CH-1 (yellow), and base input of the 2n3906 on CH-2 (green).

From those measurements i think that my turn off delay time of my pnp is way to slow, but i dont know how can i possibly improve it.
Here is the 7 segment that  I use:

EDIT:
Here is the output waveform of MAX7219 on Digit 1 and Digit 2. From what I see in the datasheet the interdigit blanking should be at least 1/32 of a cycle, but here I see almost no interdigit blanking. Any idea why?

EDIT2:
Here is the waveform of the current measurement on a segment as suggested by Spehro, the current looks fine to me. So it should be eliminate pnp turn off time as the cause of the ghosting problem right?


texts: Creating DPDT Solid State Relay with FETs

texts:
I feel like this should be a very simple question but so far I have not found a solution. My goal is to make the following DPDT relay circuit using MOSFETs:

The goal is to connect INX to OUTX or OUTY and INY to OUTY or OUTX depending on the state of an input signal (I have two data lines available for the switch control). Normally I would use a mechanical relay but due to the nature of my project this really won't work, I need a solid-state option. DPDT solid-state relays are very difficult to come by, and any I have found cannot be connected to work in the way shown in the image.

I was looking at using two enhancement mode and two depletion mode N-channel MOSFETs, but since a FET needs a G-S voltage to switch on I would not be able to simply pass the data signals straight through the FETs as they need to be isolated from ground.

So how might one construct a DPDT solid state relay entirely out of MOSFETs that would allow them to swap the two outputs (connecting INX to OUTY and INY to OUTX, or vice versa)?

EDIT: I forgot to mention, I had been looking at using bilateral switches but most of them can only handle about 30mA. These particular data lines can carry up to 200mA, so I'm looking for a ~500mA solution (hence using discrete FETs).

EDIT 2: I was looking at these: http://download.siliconexpert.com/pdfs/2014/7/28/1/10/31/351/aro_/manual/semi_eng_ge2a_aqw21_e.pdf

My thought was to connect them as follows (please pardon the crudity of the drawing, it had to be done in MS Paint, and I didn't want to put detail of the FETs and all in it. Just know that each pair of wires on the output are effectively connected to a switch:


texts: Battery Protection IC (DW06D) burning LDO (MCP1700)

texts:
I badly need your help.
I have a PIR sensor setup. It works fine without the DW06D LiPo battery protection IC.
Yesterday I added the battery protection IC (instead of just bypassing it) since the DW06D took some time to ship. This is U1 in my schematic.
The moment I inserted the 18650 battery, the LDO started emitting smoke and burnt.
I then made a small board to test the DW06D, everything worked as expected and combined with the same LDO, MCP1700, it was outputting 3.3V.
I thought that I probably shorted something when I soldered it onto my PIR board. So I soldered it again, and inserted the battery, everything went fine. I just had to clean up some solder point, so I removed the battery, and reinserted it a few minutes later, and AGAIN the MCP1700 burnt!
I don't understand what is going on. Why is the DW06D in place burning my MCP1700 on my board! Please help!

**Update 1:**
I added a picture of the tiny board I used for testing, but please remember, the DW06D chip also worked shortly on my actual board.
The short while it did work on the actual board, before removing and replacing the battery, I checked the input and output voltages to the LDO, all was fine.
The two holes on the board are just going to the 18650 battery holder on the back.
Oh and please disregard the capacitor on the tiny test board :)


texts:
I only have some limited knowledge in interrupts.

This is what I understand about following ISR functions

ISR(USART_RX_vect) will get called when a new data becomes available at the receive buffer (RXC0 of USCR0A will set to 1) and it gets cleared when data is read

ISR(USART_UDRE_vect) will get called when UDRE0 becomes 1 indicating transmit buffer is empty and ready to receive data

I set up an UART interrupt code as below, not sure is this the proper way ISR function should look like but it works

/*
 * uart_interrupt.c
 *
 * Created: 12-10-2018 04:54:04 PM
 * Author : Athul
 */
#define F_CPU 1000000UL

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

#define BAUD 9600
#define SIZE 500
int i = 0, j = 0;

uint8_t data_int;

/* For U2X0 = 0 */
uint16_t UBRR0_value = ((F_CPU / (4L * BAUD)) - 1)/2;

/* For U2X0 = 1 */
//uint16_t UBRR0_value = ((F_CPU / (8L * BAUD)) - 1)/2;

void uart_init(void)
{
    /* For a baud rate of 9600 (F_CPU = 1000000), error is 7% when U2X0 = 0. Writing this bit to one will
     reduce the divisor of the baud rate divider from 16 to 8 effectively doubling the
     transfer rate for asynchronous communication and reduce error to 0.2% */
    UCSR0A |= (1 << U2X0);

    /*set (global) interrupt enable bit*/
    sei();

    /* transmit enable, receive enable & RX Complete Interrupt Enable */
    UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);

    /* 8 bit mode */
    UCSR0C = (1 << UCSZ00) | (1 << UCSZ01);

    /* Baud rate registers */
    UBRR0H = UBRR0_value >> 8;
    UBRR0L = UBRR0_value;

}

void uart_tx(uint8_t data)
{
    /*wait till USART Receive Complete*/
    loop_until_bit_is_set(UCSR0A, UDRE0); // same as while(!(UCSR0A & (1 << UDRE0)));
    UDR0 = data;
}

uint8_t uart_rx(void) {

    /*wait till USART Data Register Empty*/
    loop_until_bit_is_set(UCSR0A, RXC0); // same as while(!(UCSR0A & (1 << RXC0)));
    return UDR0;
}

void printString(uint8_t *ptr)
{
    while(*ptr != '\0')
    {
        uart_tx(*ptr);
        ptr++;
    }
}

/*Interrupt sub-routine for RX Complete Interrupt Enable*/
ISR(USART_RX_vect)
{
    data_int = UDR0;
    loop_until_bit_is_set(UCSR0A, UDRE0);
    UDR0 = data_int;
}

int main(void)
{
    /*Initialize uart*/
    uart_init();
    /*Test*/
    uint8_t *p = "Hello";
    printString(p);

    /*Set PORTB pins as output*/
    DDRB = 0XFF;

    /*event loop*/
    while (1)
    {
        /*Toggle PORTB pins*/
        PORTB = 0XFF;
        _delay_ms(100);
        PORTB = 0X00;
        _delay_ms(100);
    }
}

To know how to implement UDRIE0, I made following changes,

//USART Data Register Empty Interrupt Enable
UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0) | (1 << UDRIE0);

ISR(USART_RX_vect)
{
    data_int = UDR0;
}

ISR(USART_UDRE_vect)
{
    UDR0 = data_int;
}

It keeps printing the data that I last entered

Then I decided to create an array and store received characters in it and the ISR(USART_UDRE_vect) would read each character and transmit it.

#define SIZE 64
int i = 0, j = 0;

uint8_t data_int[SIZE];

ISR(USART_RX_vect)
{
    data_int[i] = UDR0;
    i++;
    if(i > 64)
    {
        i = 0;
    }
}

ISR(USART_UDRE_vect)
{
    UDR0 = data_int[j];
    j++;
    if(j == 64)
    {
        UCSR0B &= ~(1 << UDRIE0); //disable UDRIE0 interrupt
    }
}

It prints "hello" and nothing else.

Can anyone tell why isn't it working.
A small example of UDRIE0 if possible?

Also compiler gives a warning
pointer targets in initialization differ in signedness [-Wpointer-sign]
What does this mean?


texts: Waking a sleeping micro over bluetooth, is this possible?

texts: I'm currently working on a low power wireless application and am looking for a possible method to wake a sleeping microcontroller (not using a timer) using bluetooth. Has anyone seen anything similar being done before?


texts: Newbie question: How do pots limit current?

texts:
From my understanding, a series circuit has a constant current, and when resistance is placed in the circuit it is voltage that changes across the resistors and not current.

Potentiometers, from what I understand, are simply a variable resistors. However, when placed in a circuit they are usually used to control current. I am struggling to understand how what is essentially another type of resistor is suddenly breaking the constant-current rule I have been told. How is this possible?

Thanks for the dumbed-down explanation, I have an engineering background but not in electronics, and I can't find a good explanation for this anywhere else.


texts:
While simulating tps54719 in https://webench.ti.com/power-designer/, for my specific application, the simulator suggested IDC in the range 9.1A to 15.75A.
Is there a logical explanation to why would the simulator prefer a IDC to be higher than the maximum amperage the DC-DC can provide (7A)?
I also get confused between IDC and ISAT, I understood that IDC is equivalent to Current Rating which can be applied at a constant rate without thermal damage, while ISAT is the saturation current is where the Inductance drops to a specified level in the datasheet.
Is it okay to choose an inductor with ISAT=24A while the simulator is asking for IDC in the range 9.1A to 15.75A? Is there an disadvantage of choosing an inductor with too high ISAT relative to IDC?


texts:
I am designing a LC CMOS Tail injection based Oscillator but somehow the node voltages are constantly showing errors.
The circuit schematics are

The properties of MOSFETs are as followed:

Node Voltages:

I am getting weird results in which the Node Voltages are constantly shooting up to Mega-Volts range.
It would be helpful if you could suggest what am I doing wrong possibly.
Thanks in Advance


texts:
I have nearly  non previous experience with VHDL and the most of the code here is given to me by the teacher.

I'm trying to communicate with a ADXL362 accelerometer using SPI on a Xilinx Sparten 3E. As far as I can understand from the RTL schematic of the ADXL362 I need to make a module with 5(?) ports. MISO, MOSI, SS(slave select), data ready and system clock for the top module to talk with it.

The SPI interface behaves like a submodule of the ADXL362 module, so how much to I need to declare of the ports in my top module then?

By the looks of it, the ADXL is the slave and I have to write a master module to be able to talk with it. But all the examples I have seen just got a lot more wires then what I got in the premade code. So I'm totally stuck as of now, so any help would be greatly appreciated.

Top modlue code:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--use IEEE.NUMERIC_STD.ALL;

-- Uncomment the following library declaration if instantiating
-- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity top_module is

    port(
        sysclk :in std_logic;

        --uart_tx: out std_logic;
        btn : in  STD_LOGIC_VECTOR (3 downto 0);
        --miso : in STD_LOGIC;
        tx : out std_logic;

        led1 : out std_logic;
        led2 : out std_logic

        );

end top_module;

architecture Behavioral of top_module is

signal tempX : std_logic_vector (11 downto 0);
signal tempY : std_logic_vector (11 downto 0);
signal tempZ : std_logic_vector (11 downto 0);
signal ZZ : std_logic_vector (7 downto 0);
signal YY : std_logic_vector (7 downto 0);
signal XX : std_logic_vector (7 downto 0);

signal clr: std_logic;

component ADXL362Ctrl
port
(
   SYSCLK     : in STD_LOGIC; -- System Clock
   RESET      : in STD_LOGIC;

   -- Accelerometer data signals
   ACCEL_X    : out STD_LOGIC_VECTOR (11 downto 0);
   ACCEL_Y    : out STD_LOGIC_VECTOR (11 downto 0);
   ACCEL_Z    : out STD_LOGIC_VECTOR (11 downto 0);

   --SPI Interface Signals
   SCLK       : out STD_LOGIC;
    MOSI       : out STD_LOGIC;
    MISO       : in STD_LOGIC;
    SS         : out STD_LOGIC

);
end component;

);
end component;

-- convert data from 12 to 8 bit
component convertion is
port (
   ACCEL_X    : in STD_LOGIC_VECTOR (11 downto 0);
   ACCEL_Y    : in STD_LOGIC_VECTOR (11 downto 0);
   ACCEL_Z    : in STD_LOGIC_VECTOR (11 downto 0);

    Ax : out std_logic_vector (7 downto 0);
    Ay : out std_logic_vector (7 downto 0);
    Az : out std_logic_vector (7 downto 0)
    );
end component;

begin
    A : ADXL362Ctrl
--clr <= btn(3);
        port map
        (
            MISO => miso,
            SYSCLK => sysclk,
            RESET => btn(3),

            ACCEL_X => tempX,
            ACCEL_Y => tempY,
            ACCEL_Z => tempZ,
            --SPI Interface Signals
            SCLK        => sclk,
            MOSI        => mosi,
            MISO        => miso,
            SS          => ss
        );

    A3: convertion
        port map
            (
            Ay => YY,
            Az => ZZ,
            Ax => XX,
            ACCEL_X => tempX,
            ACCEL_Y => tempY,
            ACCEL_Z => tempZ
            );`

SPI interface http://pastebin.com/t7LFnvDp
ADXL code http://pastebin.com/uwZ8mZBH


texts:
I am a student of EE, and recently in my book I read about the Tow-Thomas biquad filter.

The book simply states that "R4 and R4' should be of the same values, as well as R3 and R3'", but does not give any explanation as to why. I could not find any explanation on the Internet.

In my understanding, the third op-amp provides a voltage gain of -1. So here is question: why is that amplifier even needed and why is important to have specific resistances of the same value?

Thanks for your time and responses!


texts: How to modify TL431 current limiter to work with 80V bus?

texts:
I referred following circuit from TL431 datasheet
TL431 max voltage at cathode is 36V.
since circuit has only a transistor , how to modify this circuit to work with 80V at input(Vi bat).
output current should limited to 5mA. (5-10% error is allowable ) at 80V (load regulation 5% allowable).
application - short circuit protection.


texts:
I have a board with two RJ45 connectors.
One is used for an Ethernet port and the other one is for a RS485.
The Ethernet is for Power over Ethernet.
What are some suggestions to protect the RS485 port in case the operator connects the PoE at the RJ45 of the RS485 instead of the Ethernet one?
Unfortunately, the PSE recognizes the RS485 port as a valid PD, and applies power to the RS485 transceiver.
How can I avoid this?
In case the operator is wrong to make the connection I would like to protect the RS485 transceiver and I would like the PSE not to supply power.


texts: Considerations for converting a LED Bulb from AC to DC power

texts:
I was asked by my uncle to convert 22 units of gx53 LED Bulbs that are powered by 230VAC 5W to DC voltage power.
The LED Bulb itself consists of 5 LEDs(string) in series, in parallel to another 5 LEDs(string) in series.
I have disconnected the LEDs inside the Bulb from its inner driver and through a resistor i connected it to a DC power supply.
I learned using a measuring device(voltmeter) that each LED lights up with 8VDC and the current flowing through it is 8ma so the Bulb itself can be powered by 40VDC with current of 16~20ma.(5 * 8V=40V, 2 branches of LEDs * each branch is 8ma=16ma)
Now what i need is the right led driver.
I learned that LED drivers supply constant current while the output voltage is within a range of voltages.
So if i have 22 LED Bulbs that each need 20ma with 40VDC then the driver, to my understanding, should supply current of about 450ma with output voltage of at least 40VDC.
I ask for advice whether i'm right or wrong.


texts: In calculation of Maximum power transferred for reactive circuits why is this done?

texts:
We are trying to find the value of the impedance for which power transferred to the load will be maximum.

Let

$$v(t) = V_mcos(\omega t+ \theta_v)$$

$$i(t) = I_mcos(\omega t+ \theta_i)$$

Then

$$ P=  \frac{1}{2} V_mI_mcos(\theta_v-\theta_i) $$

For a purely resistive circuit

$$ P= \frac{1}{2}V_mI_m= \frac{1}{2}I_m^2R = \frac{1}{2}|\mathbf I|^2R$$

Finding the Current through the load

$$ \mathbf I = \frac{\mathbf V_T}{(R_T+ jX_T)(R_L+jX_L)}$$

To find the average power, why do we use the following equation

$$ P=  \frac{1}{2}|\mathbf I|^2R = \frac{|\mathbf V_T|^2R_L/2}{(R_T+R_L)^2(X_T+X_L)^2}$$

(as
$$ \frac{1}{2}|\mathbf I|^2R $$

the power for a purely resistive circuit.)

(instead of)

$$ P=  \frac{1}{2} V_mI_mcos(\theta_v-\theta_i) $$


texts: Calculating feedback resistors for op-amp based voltage regulator

texts:
I need to design a voltage regulator with an output range of 20-25V. I managed to re-create this ciruit from a course, but I'm stuck on calculating resistor values.

These are the formulas I'm given in the course, but so far all my calculations have led to a dead end. Needless to say I really, really suck at maths. Ignore the already present values in the screenshot above, they're random.


texts: Arduino DC Motors Not Working Correctly With The Servo

texts:
I m building a simple obstacle avoidance robot. Here I Typed the code. But there is a bug I cannot find . The Motors are not working properly when they intergrated as whole. when I check the codes and run separatly it runs the dc motor smoothly. when I put all together motors are not spining. I have double checked my connections.

Here is the code

#include <Servo.h>

const int trigPin = 13;
const int echoPin = 12;

int getDistance() {
  long duration;
  int distance;

  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);

  // Calculating the distance
  distance = duration * 0.034 / 2;
  return distance;
}

int left_speed = 10;
int right_speed = 9;

int left_pin_1 = 7;
int left_pin_2 = 6;

int right_pin_1 = 4;
int right_pin_2 = 5;

int driveSpeed = 100;
Servo myservo;

void setup() {
  myservo.attach(11);
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
  pinMode(left_pin_1, OUTPUT);
  pinMode(left_pin_2, OUTPUT);
  pinMode(right_pin_1, OUTPUT);
  pinMode(right_pin_2, OUTPUT);
  pinMode(left_speed, OUTPUT);
  pinMode(right_speed, OUTPUT);
  setForward();

}

int turnLeft() {
  digitalWrite(left_pin_1, HIGH);
  digitalWrite(left_pin_2, LOW);
  digitalWrite(right_pin_1, HIGH);
  digitalWrite(right_pin_2, LOW);
}

int turnRight() {
  digitalWrite(left_pin_1, LOW);
  digitalWrite(left_pin_2, HIGH);
  digitalWrite(right_pin_1, LOW);
  digitalWrite(right_pin_2, HIGH);
}

int forward() {
  digitalWrite(left_pin_1, LOW);
  digitalWrite(left_pin_2, HIGH);
  digitalWrite(right_pin_1, HIGH);
  digitalWrite(right_pin_2, LOW);
  delay(300);
}

int driveStop() {
  digitalWrite(left_pin_1, LOW);
  digitalWrite(left_pin_2, LOW);
  digitalWrite(right_pin_1, LOW);
  digitalWrite(right_pin_2, LOW);
}

int setForward() {
  myservo.write(90);
}

int searchRight() {
  myservo.write(0);
  delay(500);
  int dist = getDistance();
  delay(500);
  return dist;
}

int searchLeft() {
  myservo.write(180);
  delay(500);
  int dist = getDistance();
  delay(500);
  return dist;
}

void loop() {
  forward();
}

int setDriveSpeed(int spd) {
  analogWrite(left_speed, spd);
  analogWrite(right_speed, spd);
}
```


texts:
Background:
             I am sampling a signal from accelerometer at a rate of 20KHz( period of every 50 micro seconds). I need to store this information in memory card. Kit: STM32F40, IDE: Keil.  ADC Input is 8 bit. I am trying to store numbers in an array .

Question: How a variable is stored in processor?
 As per keil/ other sources it depends on compiler. Compiler would take atleast 4 bytes of memory to save an integer. for example if a number is 1024 how is it stored in processor ? will it be stored as 1000000000 or the individual number i.e., 1,0,2,4 gets stored individually ? if the number is 256 how is it stored in processor ?


texts: Low current (~100ma) buck voltage converter simple, low cost options (48V to 12V)

texts:
I have 48V AC-DC power supply that I use to drive high power LED drivers. I also want to use the same 48V input to power a 12V fan and Arduino Pro Mini. Fan is rated at 0.25A but I could do without the fan at all if the voltage reduction circuit can be simplified at lower amperage.

I considered linear voltage regulators but with LM317 the efficiency would be below 5%.

I also considered voltage divider but wasn't able to get it to work. With high resistor values the voltage dropped drastically when load was applied. With lower resistor values they would dissipate around 3W with one configuration for example.

Lastly switching power regulators aren't ideal because the cost is quite high for input voltages over 40V such as over 2 euros for a single texas instruments LM25019. Then there's also additional components like inductors that are out of my scope of knowledge...

Are there any other alternatives? Could voltage divider be a suitable solution?, if so how?


texts:
This is a question from my intro circuits class that I can't figure out the answer to:

Of course it's very simple, but I had a professor who was incomprehensible most of the time, and my textbook doesn't have any examples similar to this. Would someone please either point me in the right direction to answer this or suggest a good and free resource for me to use to teach myself?


texts: Best way to communicate Raspberry Pi and ATTiny13

texts:
What is best way to connect two or three microcontrollers, ATTiny13 to Raspberry-Pi and get master (Raspberry Pi) communication? Are there any ready libraries for ATTiny13 for SPI or I2C? Maybe some other protocol supported by Raspberry Pi?

It doesn't have to be really fast. 1-wire speed is enough for me. Easiness is priority for me but I also don't want buy too many expensive items.

I found 1-wire slave library but I have issues with it so I'm looking for alternative.


texts: sending differential signals off board, what kind of connector do I use?

texts:
So, my question is this. I've got four differential pairs from an LVDS chip which need to go to a connector, along with a few single-ended signals.

For this purpose, I chose a hirose df13 connector.

I found out today, however, that there exist connectors specifically meant for differential pairs (e.g. Samtec QTH-DP)

Is that really necessary for differential pairs? In general, is there some necessary characteristic I need to look for in the connector I use when it comes to pairs?

On the flip side, if I were to use something like the QTH-DP, can I send single-ended signals through it? Or would I require 2 connectors, one for pairs and one for singles?


texts:
In the SMBus spec it says:

  The I²C specifications do not require that a device always acknowledge its own address.
  This can confuse a system controller.
  If a device does not acknowledge its own address how does the system controller know if it is because the device is busy, has failed, or has been removed?

This sounds a lot like blackening I2C, and I'm not used to see this kind of language in a spec.

Besides, I think SMBus is lying here. In I2C the address byte must be acknowledged just like any other byte. Or must it?


texts: Controlling AC mains using Arduino and removing control easily

texts:
I am planning to for an Arduino to read status of a switch, and accordingly switch on and off AC appliance, for a demo purpose. I want to add a feature to it of easy recovery to manual switch control.

simulate this circuit – Schematic created using CircuitLab

First circuit to the left is when Arduino reads status of switch, and controls a bulb by digital pin P2 which drives SSR/relay.  Circuit on the right is normal switch board controlled light bulb.

So basically what I am trying is: when I remove Arduino board, my previous control (light bulb controlled only through switch) should be regained. Really stuck on this, help will be highly appreciated :)


texts: Soldering station - sensor fault protection

texts:
I have got the attached soldering station schematic and I need a protection for the soldering iron heater in case of disconnecting one or both thermocouple wires.
Source of the schematic: http://electronics.vlzqz.com/home/lm324-analog-soldering-station

I added the Rx1 (100k) resistor to the thermocouple amplifier block. Will this resistor protect the soldering iron by blocking the triac in case of disconnecting one or both thermocouple wires?
During the testing of the schematic I saw that if I use MOC3041, the led flashes at a higher frequency in comparison to MOC3021. Which one, between MOC3041 and 3021 should I use?


texts:
I am looking for an circuit that can do as follows.
I have DC24v (200A) x2 battery packs and 24v DC electrical equipments..(which uses about 80A atleast)
So lets say i want a circuit board that can connect 2 battery input and 1 output.
So if i disconnect 1 battery pack the unit should automatically switch to the next battery pack without power interruption..
Is this possible?


texts: Protocol used by tankless water heater remote control

texts:
Edit: see my main thread here Reverse-engineering asynchronous serial protocol for EcoSmart Tankless Water Heater

I'm using an EcoSmart ECO 11 electric tankless water heater in a hydronic system.

This heater has a "Remote Control" port on the side.  The port is an RJ-11 jack with 4 wires.

I want to interface this unit to my house heating control system (a networked Arduino). I want to get the following information from the heater (or as much as possible):

Water inlet temperature
Water outlet temperature
Water flow rate
Temperature setting

I contacted EcoSmart to ask for protocol details, but they discontinued the remote 3 years ago and stated that there is "no information available" about it.

I can gather some basic details about it from the Amazon page:

There are 4 wires in the cable
Two remotes can be connected simultaneously on the same bus.
The remote displays the temperature setting, as well as providing Temperature Up, Temperature Down and Power buttons.

Does anyone have suggestions regarding the type of bus used to communicate between the unit and remotes?

I have a 4-channel o-scope with the option to decode various protocols (I2C, SPI, etc).  I don't have an EcoSmart remote to test with.

Any suggestions welcome.  Maybe someone knows if there are standards for this sort of thing?

I think SPI can be eliminated, because each slave requires a select line, and a 4-wire bus wouldn't provide this for 2 remote units.

I have no problem disassembling the unit if necessary, but I'm betting it uses a custom ASIC with little info.  It looks pretty generic - I'd say mass produced for multiple rebrands.

Thanks for any insight or tips!


texts: Kicad: How to add a Filled Zone around a Net with a single pin?

texts:
I am designing a PCB in Kicad and I need to add a filled zone around a single pin (pin needs to become part of the zone, not an island).

For some reason, when the "Copper Zone" tool provides me with a list of nets, it does not seem to include the nets which only have one node.

The reason I only have one node in that net is b/c I am connecting an incoming
+110V line to a switch contact. I've tried connecting the switch to a Power
Symbol, to a PWR_FLAG and to a hierarchical pin, but the generated net still
only contains one node:

(net (code 11) (name /Mains_Power/+110V)
  (node (ref SW1) (pin 1)))

What can I do to make the "Copper Zone" tool allow me to select that net? Is there some other way to create some copper around that pin?

Thanks!


texts: How to model RF-PA in MATLAB when the design values are given?

texts:
I have been given a designed Class-E  RF-PA - the technology used for the MOSFET, the inductor and capacitor values attached to the MOSFET (as given in the figure below). I am suppossed to find the AM/AM and AM/PM distortion graphs using this information using MATLAB or Simulink.

I searched on the internet, and I could find memory polynomial block of the RF-PA (which needs input of the behavioural model of the PA) in RF-Blockset. But, I do not know how to implement my model using this available block. Is there a better way to do this? Later on, I also want to implement the DPD and memory effect - which I figured out how to do. But, I do not know how to get started.


texts: One transistor versus two transistors as a switch

texts:
Why does the led dim first and then switch off when I use one transistor as a switch, but directly switch off when I use two transistors as a switch?
These are the two circuits:


texts: Starting Copper thickness & finishing Copper thickness

texts:
What is the difference between 'start copper' and 'finish copper'? If the specified requirement is of '2 oz / 70 um Copper thickness', will that be start copper thickness or finish copper thickness?

A little confused with the terms there. Will be grateful for help!

Thanks!


texts: Help me understand my campervan split charge relay

texts:
I am new to the world of electronics, but keen to learn. The below all relates to the 12 V circuit of my van.

I have picked up a campervan which has a second "leisure" battery which powers items in the rear, such as LED lights etc. These lights run off a caravan-style "power management system" and this system is fed from the leisure battery via a 25 A fuse.

When driving, the van alternator (90 A) charges the starter battery like a normal car. There is a split charge relay (CB1FM-12v) which closes the relay when the ignition is on and this allows the current into the +ve terminal on the leisure battery also. This +ve terminal on leisure battery also has a wire off to the PMS system in the rear via a 25 A fuse.

My question is this: if the alternator can produce 90 A then when the relay switch is closed (ignition is on), why doesn't the relay fry as the relay is rated at 40 A?

Also, why doesn't the fuse going to the PMS blow as the fuse is only 25 A?


texts:
It might sound stupid but I'm in a real doubt since many datasheets disagree regarding the  BF494 transistor pinout.

1- http://www.datasheetdir.com/CDIL-BF494+RF-Transistors

2- http://www.electronica-pt.com/db/componentes.php?ref=BF494..495

3- http://www.datasheetcatalog.org/datasheet/philips/BF494B.pdf

I soldered erroneously because of this confusion and i'm now waiting some insight to sold again.


texts: Why are NAND flash and NOR flash named using the terms NAND and NOR?

texts:
Is the naming of the two flash architectures related to differences between the two types of logic gates?  If so, how?

Why does or doesn't this difference also apply to different DRAM or SRAM configurations or layouts?

(This question is not about the R/W performance or usage differences between NAND and NOR flash, which has already been asked here: What are the differences between NAND and NOR flash? )


texts: As a follow-up to my other question: what components I could use instead of a 4PDT switch to create the desired effect of switching a USB device such as a keyboard between two systems? I'm new to electronics and am seeking some solid basic information.


texts: i have problem with capacitor discharge ignition circuit CDI

texts:
i have a hard time to understand what is the problem in this circuit, can someone help please, i have a Moped with its capacitor discharge ignition Box work fine, the spark exist, but i wanted to make my own capacitor discharge ignition circuit because i like electricity, electronic is my hobby so i did some research and i found circuits diagram and explenations and seemed to me that i understood them but when i created the circuit it didn't work no spark, i tryed anything
this is the diagram below and thank you


texts: BC547/BC548 with 5V at base can't control 12V at collector-emitter?

texts:
For an Arduino project I needed both 5V and 12V voltages. Specifically, for an IC I needed 5V and I needed to be able to switch it on and off using an Arduino PIN. Since the current drawn by the IC might exceed what can be drawn from the Atmega328 pins, and since I couldn't tolerate any less than 5V, I tried using the following circuit.

So the idea was to control the 12V source using the BC547 transistor with the base controlled by an Arduino pin, and then to feed the emitter of the transistor into a standard 7805 regulator setup (with cap sizes taken from the 7805 datasheet).

However, the circuit doesn't work as expected. I'm only seeing 4.32V on the emitter of the transistor - not 12V as I had expected. I can see that the input to the base is drive to 5V, and given the 4K resistor there should be amble current for the base (at least for 100-200 of collector-emitter current). Yet it seems the only voltage I'm seeing at the emitter is the mentioned 4.32V which seems to be just the base voltage minus some voltage drop. Changing the 4K resistor to e.g. 800 ohm didn't change this.

So what is the problem here? It is not possible to control 12V using 5V at the base? If so, from what values in the datasheet can this fact be derived?

I tried replacing the BC547 with a 2N7000 MOSFET, and that actually worked and I'm seeing 11.3V at the emitter of the transistor, and 5V at the output PIN, as expected. But I don't see why the BC547 couldn't do the job.


texts: Classify Signals (Static vs Dynamic) Homework Assignment

texts:
For the following assignment, I only want to see if I am on the right path when answering the question.

The following question ask:
let x(t) be the system input and y(t) be the system output. Determine whether the system is static vs. dynamic and causal vs. non-causal.

1) y(t) = 2x(t-1) + 4x(t-2) + 3x(t)

2) y(t) = 10\$x^2\$(t)

I started off by plugging t = 0 in equation 1, which results in:

y(0) = 2x(-1) + 4x(-2) + 3x(0)

From this the first two terms on the left side of the equation depends on past inputs. For this reason, I believe the system is dynamic and casual as the output depends on the past and present inputs.

For the second problem, I also plugged in t for 0 for:

y(0) = 10\$x^2\$(0)
I believe this is static and casual(output depends on only the present value).


texts: Dubious output from instrumentation amplifier

texts: I have a setup as shown in the schematic below. I am using AD9833 DDS to generate a sine wave with ~300mV DC and ~600mVpp signal. I am sending this though a RC high pass and sending this over as first input to an AD620 in-amp. The other input to the in-amp is ground. I am adding a buffered voltage of 1V to set the output common mode as suggested in the data sheet. The first scope capture shows node A (the input sine wave to the inamp). The output is shown in the second capture and as you can see the chip is railing(or is unstable, I dunno). I can't figure out what is going wrong. The gain should be simply ~1.5, so there should be no reason for this weird output. What I have messed up in the design? I have probed all nodes to make sure the voltages are correct.


texts: Dependency of Collector current in common base transistor(active region)

texts:
I just started reading about transistors from book "Microelectronics circuits"by Sedra/Smith,
This is written in book which I don't understand, any help would be much appreciated
For forward active mode -
"Collector current(Ic) is independent of Vcb(reverse voltage between collector and common base )"
But in next paragraph it is also written that
"saturation current is inversely proportional(Is) to width of base (W) "
And "saturation current (Is) is
Directly proportional to collector current (Ic)"
So I concluded  that -
collector current (Ic) is inversely proportional to width of base(W)
But how it is possible that collector current (Ic) depends on width of base (W) but not on
Vcb?
Isn't by  changing Vcb we can change the size of junction (between base and collector) and if size of base-collector junction changes then effective width of base (W) also changes
And hence collector current changes?
So why there is contradiction between my conclusion and what is written (as I explained above) in book?
Where did I go wrong?


texts: Phasor is used to represent an AC quantity but for fixed frequency resistance and reactance of the circuit are not alternating but still they are represented by phasors. So is it right to call them phasors or they should be called something else like vectors or stationary phasors etc ?


texts: Replacement of MEMS gyroscope with better less noise devices

texts:
Is there any good replacement for MEMS based 6 or 9 degree of freedom gyroscope to use with Arduino ?

I read that most of MEMS are not reliable regarding the values, with slow reading and high noise effect on raw values.

Here is the link I was reading and quoting:

  There is no 'best', the MEMS sensors are all more or less unstable and
  noisy.


texts: In a closed loop system, when obtaining a bode plot why is the open loop transfer function used?

texts: In a typical closed loop system, with G(s) as the forward function, and H(s) as the feedback function, why is the transfer function used to calculate the bode plot G(s)H(s) instead of G(s) / 1+G(s)H(s)?


texts:
I am transmitting RS485 via:

Mono application -> Linux USBTTY device -> RS485 adapter with an added 100R terminator -> ~1m CATV -> SN65176 with an added 100R terminator -> PIC.

Via debugging I am able to see that transmission from the application to the PIC is successful, and the PIC transmission out of its serial port is also OK. However, when the SN65176 is switched from receive mode to drive mode, the output low level is very noisy (see scope capture):

In this scope capture, channel 1 (blue) is the data (R/D) side of the SN65176, and channel 2 (yellow) is at the RS485 terminal close to the PC.

In this particular case, the first byte was from the PC (00001101) and the second byte was from the PIC. It was supposed to be 00011101 but was received as 00000100.

Here is the relevant Mono/C# port code:

        port = new SerialPort(
            portName: portName,
            baudRate: 115200,
            parity: Parity.None,
            dataBits: 8,
            stopBits: StopBits.One)
        {
            Encoding = ASCIIEncoding.ASCII,
            Handshake = Handshake.RequestToSend,
            DtrEnable = false,
            RtsEnable = false,
            WriteTimeout = 1000 // ms
        };
        port.Open();
// ...
        Port.ReadByte()

The RS232-to-485 adapter is an XS201A. It claims to have fail-safe biasing; however, direct measurement does not support this claim. Perhaps that's because the bias is only enabled when the unit is powered, but I don't consider that particularly fail-safe. It provides no schematic and it's a sealed unit, so it's more difficult to reverse-engineer the thing; however, when driven in the presence of external 100ohm termination on both ends, I see the following voltages:

Va-Vb = 44mV
Va-gnd = 311mV
Vb-gnd = 267mV

The XS201A also claims to use "Automatic Send Data Control", to be port-powered from RTS/DTR/TXD, and to short RTS+CTS and DTR+DSR+CT.

With the SN65176 disconnected, and some slightly different biasing, it seems that the XS201A has an undocumented 4 bits of line drive after which the driver is disabled:

This shows two consecutive 0x33 from the PC. There is one stop and start bit surrounding both bytes, plus the trailing drive timeout.


texts: Read the instrument data from printer port directly with computer

texts:
I could not find the step by step guide of some kind to accomplish what I am planning to do. I have two devices that I want to connect to PC (windows). Right now, both devices write their output through the printers attached to them. My goal is intercept the data sent to the printer and read the output through computer and remove the printer completely from both devices. On one of the device, the OEM seems to have used just some pins  and removed others.

Can you please advise  in a step-by-step manner the instructions I need to follow to transmit the data directly to the computer?

I have attached the images of the cable that is now going to printer.

I have some programming experience but this is the first time I am playing with serial and parallel port communication.


texts: Why doesn't controlled impedance depend on track length?

texts:
High speed design noob here.

Resistance increases as wire gets longer, but I found in saturn pcb calculator the impedance depends only on track geometry and distance from plane.

Say for DDR3 single ended signals with controlled impedance, does a point to point long track (say 150mm) vs. a short track (say 10mm) have any effect on the signal quality?


texts: How does the current remains constant in an ideal capacitor?

texts:
In a tutorial given here, it is explained that the current remains constant upon sweeping the potential in an ideal capacitor.

Can someone explain in a descriptive way (in terms of the role of electrons) how it happens?

When applying a positive potential, we are charging the capacitor (right?) Why the current remains constant during charging?

Constant current means a constant flow of electrons in the circuit (right?) Then, how is this flow kept constant?


texts: Process for Making a Flyback Transformer

texts:
I am looking to make my own flyback transformer that can put out a DC voltage from 0 to -40 kV DC and a power of 400 watts, as most commercial flybacks do not go up to the specified power and typically do not provide a negative voltage. Thus, I was curious how I could build such a device and the what the required specifications for the components used in the transformer (i.e. the size of Litz wire and the amount of wraps on either side) would be to build a proper transformer.

Preferably, the voltage input for such a design should be 0-24 V DC with a transformer output that correlates with the input (basically resulting in an adjustable output based on an adjusted input if possible). The ripple of the -40 kV DC output should not exceed 350 V.

If the use of a single flyback transformer would be impractical for such power, how could I create an assembly of transformers that would collectively provide the needed power and voltage? Thank you.


texts:
I am designing a BLDC motor controller circuit on my own.
My BLDC motor ( Chinese motor) is 1kw with a hall sensor and my own controller spec is 1kw,48v, and 30A.
My controller circuit is working fine in a breadboard and dot board using a basic running program
without load condition.
After PCB fabrication, we used that PCB it's not worked properly.
It seems my program is good, but some problems in PCB designing method for the controller.
I will list my problems below,

First, I give power supply of low voltage (12v) to PCB and its works fine with low RPM

After achieved MAX voltage 48v, my microcontroller is totally shutdown and restart again.

Finally, everything is working fine in the dot board but not working properly in PCB.
Anybody, suggest to me for any solution..Thanks in advance...
For dot board using dip components and PCB using SMD components ..it is the only difference between two boards..no circuit changes in both boards... I have attached PCB top and bottom layout images link
https://drive.google.com/file/d/16Uc1cxBVntGvoIVNmZq42yVkoka9LSe6/view?usp=sharing
https://drive.google.com/file/d/1_4SZBrsR8X5_vp-OHbwVBBvNUk6h6OkP/view?usp=sharing


texts: how to calculate value of capacitor and inductor in a high power LC circuit?

texts:
I am a new learner of electronic.

I am trying to modified a H-bridge motor driver circuit to control a thermoelectric cooler. Since I want to use PWM to control mosfets ON/OFF duration, in order to control the input voltage of the thermoelectric cooler. I want the circuit can output a smooth voltage then I use the LC filter, but I don't know how to calculate the value of L & C.
I try to use 16V,180uF capacitor series with another 16V,100uF capacitor and in parallel with the thermoelectric cooler, it turns out that mosfets are damaged.
Can I just capacitor to do the voltage smoothing? If yes, how can I determine what's the value of the capacitor I should use?

the circuit is similar to this:

PS:  The maximum voltage of the thermoelectric cooler is 12V (dc) and maximum current will be 12A, the maximum output frequency of micro controller is 1MHz.


texts: Is there a fluctuation effect between heat, resistance and current?

texts:
We are told that heat increases a resistor's resistance (or decreases its conductance) and current decreases when resistance is increased.

So with less current, less heat would be dissipated, which drops the resistance and causes more current to flow, and then again, more current, more heat...
It seems like an endless cycle .

Does this fluctuation ever occur in real circuits? Does it stop at some point?

(I am referring to DC circuits, since this would probably be much more complicated in AC circuits)


texts: Passive Cell balancing affecting Gas Gauge Coulomb Count

texts:
I am designing a solar 7.4V Li battery charger, and want to include gas gauging, and cell balancing. If I use passive cell balancing, I waste power and cause my coulomb counter to lose count. Is there a way to balance the cells without affecting my gas gauge? I'm trying to stay away from the complicated $10+ active balancing ICs. Is there a discrete solution?

Specs:
Max charge/discharge: 2.1A

Max Vin: 8.4V

Battery: 2Series, ~2000-3000mAh

Two ICs I am considering:

DS2745   <-Gas Gauge

BQ29209  <-Cell Balancer


texts: Questions About My Solar Home System School Project

texts:
I have a battery, light bulbs, a solar charge controller, and a solar panel. The actual issue has come with me testing the solar panel. I have both a 30W and a 50W solar panel, so I am assuming the issue is not with both of these solar panels. I have been using a multi meter to test them. When it is sunny out, it usually gets over 20V. This part is fine. The issue is what happens when I measure the current of the solar panels. On the 10 Amp setting, I am measuring 0.2 Amps. This would mean that the solar panel is only producing 4 Watts. I have tried moving the solar panel and adjusting its tilt angle as well.

Additionally, when I connect a circuit with light bulbs, the light bulbs light up. These are 5W. Yet somehow the multi meter says that there is less current moving through the circuit. So this is where my questions come in:

Because it is a 10 A scale, does that mean that the .2 is actually 2 A or not?

Is there another reason that both solar panels would have this discrepancy?

Am I measuring something wrong or should I be doing it a different way?

What would you consider the best way to measure the efficiency of the system?

This isn't working at all well even in good sunlight and at the right tilt.


texts: Wireless Communication between cellphones

texts:
Hypothetically, is it possible to transfer data from 2 devices using a 4g network that's not from their service provider. OR in other words: Could one device download the data from the provider and send it to another a few km away (at the same speed which is why I'm saying the 4G network/band)? (The assumption is both devices can receive and transmit on this network. Would that be realistic if they both could download data from a provider?)

Another question I had was that this would need another band that acts as a channel, or would this "other band" basically need the same data requirements to pass through it, like the downloaded data from the device from the first provider. Essentially is there any difference from channeling the data versus being the provider for the original device that downloaded it.

Curious to hear other thoughts on how I could send data downloaded from one device to another a few miles away (for e.g. on a smart phone without using any other kind of hardware preferably).


texts: DC relay with 2.5V coil voltage and contact voltage of +12V and -12V

texts:
I am working on a project where I need a DC-relay which has 2.5V coil voltage and contact voltage of +12V and  -12V.
My relay should act as a switch. when relay input is 2.5V then it should pass both +12V and -12V otherwise it should stay OFF.

Please let me know if anyone knows which type of relay should I use.

Thanks in Advance.


texts: From noise spectral density to equivalent short circuit input RMS noise

texts:
I have an acquisition system that is supposed to be low noise. It acquires from an ADC into a wav file. I read this file and process it with Matlab. Then, being "x" the array with time signal, Fs the sampling frequency, and N the number of samples, I calculate noise spectral density (NSD), as indicated in Matlab help:

N = length(x);
xdft = fft(x);
xdft = xdft(1:N/2+1);
psdx = (1/(Fs*N)) * abs(xdft).^2;
psdx(2:end-1) = 2*psdx(2:end-1);
freq = 0:Fs/length(x):Fs/2;
plot(freq,10*log10(psdx))

Now, this seems correct and works well; I am getting noise figures that make sense.

However, this is the noise power spectral density calculated in dBFS/Hz, that is the power in dB referred to the full scale of the ADC on the bandwidth of 1 Hz. I would like to convert this into the equivalent short circuit input RMS noise voltage (which is usually expressed in nV/sqrt(Hz)), of course knowing the full scale of the ADC.

How do I do this conversion?


texts:
I've a simple circuit where I need to detect AC voltage presence via a microcontroller (ESP32).

The ESP32 is a 3.3V device, and requires (worst case) 2.8V to consider a logical one on a GPIO.

I'm using a photocoupler (TLP290) for this. Such photocoupler requires at least 0.5mA to start conducting (the CTR for such a low diode current is only 70% typically).

On the AC side, I'm currently using two 1/4W resistors in SMD. (See top circuit). For the configuration shown, I'm expecting 0.7mA in the circuit (input is 230Vac at 50Hz), so the resistors will dissipate ~90mW each. In case of overvoltage, with 280Vac, they'll dissipate ~130mW each.

simulate this circuit – Schematic created using CircuitLab

I think such power might cause issues (like local high temperature on the PCB) so I'm trying to replace the basic resitors by a more complex RC filter so that the impedance is close to what I want at 50Hz, but less power is dissipated in the resistors.

See the bottom circuit for an example implementation. In such circuit, the impedance of the RC filter is ~300kOhm at 50Hz so the same current flows in the circuit, but then the power dissipated in the resistors is now only 12mW.

I understand I must use a X rated capacitor for this case (I'm not connected to ground in that case), but I don't understand which of X1 or X2 type I must use.

I'd like to avoid using film capacitors here, since they only exist in through hole version, and I'd like to use SMD capacitors here (15nF does exists in SMD in 2010 package).

note: I haven't found an optocoupler in the circuit drawing software on this site, so please consider the D1 or D2 diode as the 2 inputs diodes of the AC photocoupler.


texts: How to stop Car Alternator audio noise / buzz?

texts:
I connected a Raspberry Pi 2 in the car to add OSMC media player capabilities. However, there seems to be a buzz / hum of background noise in the audio. The noise is correlated to the engine speed so it seems to be coming from the Alternator.

What are some different method of fixing this?

Is there some kind of shielding that could be implemented?


texts: Is it possible to put a via right next to the component pad it is connected to? In other words, if a via and a component pad are on the same net, can they touch as in the image below (red=top layer, yellow= mid layer, gray=via's pad, brown=hole, pink=component outline,distance shown=edge of hole to edge of pad)?


texts: Sending a rapidly changing variable through SPI

texts:
I am trying to send the value of a counter running in timer1(32bit) to another chip, ideally through SPI. The timer triggers an interrupt every 1ms to increment the counter. Overall, the variable increments constantly but for some reason the variable goes backwards occasionally.

unsigned long t=0;
void timer1ISR(){
   timerFlagBit=0;//clear interrupt flag
   t++;//increment the counter
}
void sendValue(){
   static unsigned long tempT;
   tempT=t; //save the value to a temporary variable
   Spi_Write(tempT>>16); //most sig byte. I only want a three byte value
   Spi_Write(tempT>>8);
   Spi_Write(tempT); //least sig byte
}
void main(){
   init();
   startTimer();
   while(1){
      Delay_us(500);
      sendValue();
   }
}

Any advice on how to transmit a rapidly incrementing value?

Here are some examples(I took out repetitive values):
It increments by a step of one from 0 to 20. The next value right after 20 is 99.
It then increments from 99 to 114 by a step of one and then the next value is 95.
After 95 come 96, 97, 98 then 197, 198, 199, 200, 201.
After 201 it jumps back to 182 and starts incrementing from 182 to 196.
After 196, it jumps to 276.

So only at the very beginning it jumps according a pattern if I graph all the values.
It looks like this:
After a short while the value stabilizes. I have played with the priority with the timer but nothing has changed.

This is done on a Microchip Pic.


texts: What does resistor value change in a passive audio sum circuit?

texts:
I'm looking to build a passive audio sum box to connect two mixer headphone outputs (with output impedances of 10 Ω and unknown) to a single pair of headphones for music performance. I plan to use my 18 Ω Sennheiser HD 4.40 BT headphones with this. I know this question is duplicated elsewhere, but I've not seen explanations that make too much sense to me so wanted to understand what reasoning is used to choose the resistance values across all use cases.
My understanding is that the resistors serve to electronically separate the inputs to prevent them trying to drive each other when they disagree on input voltage. Is this something that's done by sufficiently 'weakening' any signal that does make it through the common connection and back towards a different input, or have I got the wrong end of the stick? I've seen some people saying it 'converts the signal from voltage mode into current mode which can be added in parallel and then back' (paraphasing - see MarkU's comment here) - how does this work? Given that any wire has a resistance, presumably this is a sliding scale rather than a proper conversion?
I've also seen people recommending resistor values that are several orders of magnitude apart. I've seen suggestions as low as 10 Ω and as high as 10 kΩ.
I've graphed the equations shown in this answer with headphone impedance as a constant set to 18, source impedance assumed to be around 10 Ω and resistor value on the x-axis. It seems that increasing impedance reduces attenuation (counterintuitively to my monkey brain) with diminishing returns but massively increases the impedances seen by the headphones and outputs. Since I know the impedance seen by my mixers and the overall output impedance seen by my headphones in normal operation, I'm thinking I'd aim to keep it about the same as what I know works, so I think 10 Ω would seem to be my best bet. Am I right in thinking that is desirable?
My assumption is that the higher values are better where the mixer would go into an amplifier (whether a built-in op-amp or an external speaker amp), whereas a direct load such as headphones would be better off with a similar resistor value to that load's impedance - is this correct?
Returning to my specific case, for a bit more context: both mixers have headphone volume controls so I'm not too worried about getting the volumes absolutely correct, and I'd like to minimise the attenuation but I'm not too stressed as both can run my headphones at reasonable volumes with quite low output levels so I believe I have a fair bit of headroom. I'm asking this question more as I'm interested in how I could calculate the ~'"best"'~ value in some arbitrary situation and don't fully understand the mechanics behind it all.
TLDR, I'm a bit of a noob and have some ideas about how this works but I'd like a concrete answer before I build something stupid!


texts: Capacitor running hotter than I think it should

texts:
This is in the right hand power amp in a Nakamichi AV-10 receiver. Whilst watching the Olympics opening ceremony at considerable volume, the unit overheated (hot pcb smell) and cut out.

Having cooled it now works up to a point.

The main problem is that now cuts out at moderate volume. Using an Infrared Thermometer I have identified this capacitor running at 63C. It's mate on the other amp is at 30C. Cooling it with a fan allows the amp to operate at higher volume.

The other slight problem is that there is a faint crackle on the right speaker.

So, my question.

Do you think that the capacitor is the problem, or is it merely the indicator of a different failure?


texts: 9-pin micro-d connector for LVDS signals

texts:
Has anyone utilized 9-pin micro-d connectors for driving and receiving LVDS signals? I am running the LVDS at 100 Mbps for 20-30 inches.

I am using a vertical pcb mounted connector 380-009-213 from NorComp. Can this connector be used?


texts: getting access to more UARTs on micro controllers

texts:
I will need to interface a micro controller to some breakout boards that only talk through UARTs, so confronted with the eternal 'need more hardware UARTs' problem.

I have seen 2 kind of solutions out there:

add a barebone ATmega328P or similar, connected by I2C to the main micro controller, and use it as an UART. Sounds like using a hammer to kill a fly.
find a dedicated barebone micro controller breakout for doing this, for example:

https://www.instructables.com/id/SPI-to-4-x-UART-Bridge-MULTIUART/

This is a bit the same as using a barebone ATmega328P, but at least I get 4 UARTS. I looked for established shops where to buy these already assembled but could not find. Any suggestions?

Any other idea? Is there really no hardware bridge I2C <-> UART available as breakouts out there?


texts: What is the difference between nets and buses in Altium Designer?

texts: As the title, who can tell me the difference between bus and net in Altium?


texts: How to reduce a pulse voltage maintaining a high impedance?

texts:
I have one pulse with 200ns and 60 V. I have to reduce this voltage until 10 V min because of the monostable multivibrator. After this, I will extend the pulse with a monostable multivibrator and then I'll count this pulse with a microcontroler.

The problem is that I have to reduce the tension keeping the point of mesure with a very high impedance in order to do not perturb my test circuit.

I have 2 option in mind but I am not sure if they will be work:
-use a transistor (60V is very high for the base of a transistor,  think)
-use Current Transducer(limited in bandwidth and my pulse is to short)
Maybe someone can have an better ideia . Thank you in advance =)


texts: DC motor power consumption grows every time direction is reversed

texts:
I am building a Li-Po powered robot, with NodeMCU at its core, and two DC motors run through a TB6612FNG DC motor controller. Also some sensors that are not relevant here. Full schematic:

Basically Li-Po is connected to a boost converter going up to 6V, which is then fed into NodeMCU and the TB6612FNG, while the NodeMCU 3V3 line is used for powering logic level. I am switching AIN1, AIN2, BIN1 and BIN2 pins on the TB6612FNG through PNP transistors, so I can control motor directions with 2 pins on NodeMCU instead of 4. Please ignore the sensors and the servo motor in this example, they are disconnected on my test board.

I wrote a dead simple code that turns both motors clockwise for 1 second, stops for 1 second, then runs counter-clockwise for 1 second, and stops for one second again. This is a single loop, which is repeated infinitely. Full duty cycle, PWM frequency set to 512.

Now, something really weird is going on. I noticed that after some time of motor going back and forth, my Li-Po battery disconnects. Safety feature due to over-current. So I hooked it up to my PSU instead, and noticed that with each loop, the current draw on the clockwise rotation remains the same, but the current draw on the counter-clockwise rotation gradually increases. After some 6 or 8 loops it reaches its peak, and then starts decreasing with every loop. Like some sort of a wave.

I hooked up just one motor for demonstration purposes. At rest, current consumption is ~155 mA (that's for NodeMCU). With motor running clockwise/counterclockwise at first loop, the consumption is 214/223 mA. Second loop - 214/300 mA. Third loop - 214/331 mA. Fourth loop - 214/366 mA. And so on. It keeps growing and growing until it reaches almost 800 mA, and then it starts going down again. I caught this on tape:

https://youtu.be/lTup1g7zn-g

Now, things I already tried:

Soldering ceramic 0.1 µF capacitors between motor legs, and also to the chassis, as well as twisting the wires;
Soldering a fat 2200 uF electrolytic capacitor right to the TB6612FNG VM/GND pins;
Replacing motor - I have 6 motors of different kinds (different brand, size, power, etc.);
Replacing TB6612FNG;
Increasing and decreasing the time that motor spends at rest;
Swapping the DC motor polarity;
Switching from A channel to B channel, even tried one wire on A channel, one wire on B channel;

And none of these things made the slightest difference. Nothing changed, at all. The current still grows with each loop in one direction.

Important note: if I run motor continuously in one direction - doesn't matter which direction - the current consumption remains the same, steady at around 214 mA. This strange growth only happens when I start changing directions, as in the video.

I could understand that if I changed the motor direction immediately there could be a power surge, but the motor spends whole 1 second at rest! And yet something remains. It's almost as if the current is "pooling" or something. I can't explain it rationally.

Any ideas? What is going on here?

EDIT: One detail that might relevant. During these current spikes, the voltage does not drop anywhere across the system. Not from PSU, not after the boost, nor the 3V3 line on NodeMCU. All voltages seem to be very stable.


texts: To protect a LiPO cell from undervoltage, how low current is low enough?

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This may seem like a topic beaten to death, but bear with me.. this is an apparently ignored wrinkle. Over the past several weeks I've been designing various circuits to protect a LiPO cell from under-voltage, if the user of my device carelessly leaves it on. Now I know you can buy protection circuits ready made, but most of them start cutting the current when the LiPO voltage gets to around 2.5V. If you really want to protect a LiPO cell from damage, 3.0V is a much better discharge point to call it quits. At this point I thought I had a few good solutions, but I may be wrong... dead wrong!

I don't know about you, but if I accidentally leave something ON, and its something I don't use every day, then it might be ON for days... maybe weeks or months. I've come to realize that just about any scheme to stop battery draw when the voltage is too low is NOT going to drop the current to ZERO. Even the best MOSFET based circuits are going to have leakage current, and a good control circuit may increase it more. So how low is low enough?

I suppose its somewhat related to the capacity of the cell. Obviously if my cutoff circuit limits cell current to less than 1 uA, that's going to prevent a 10000maH cell from damage for a good long time. But what about a 200mAH cell? Would a cutoff to 1uA offer "reasonable" protection or am I just kidding myself? What about 1/10 of that (100nA)? the lower the circuit leakage, the more expensive the design. So how low is low enough?

Addendum... Here is a circuit I'm intending to try. If it works as I'm hoping, it will will reduce residual current to about 1uA when the cell voltage reaches about 3V. There are only 3 parts here, a Load switch made by Fairchild (FDC6331L) does all the grunt work of cleanly switching my load, while a Microchip part ( MCP112-315 or MCP112-300m) "trips" at about 3V, to control the load switch. The total cost of this circuit is about $1, and the low part count is due to the multiple parts inside each IC. This is still unproven but I'm hopeful. But if it works as planned, time and experimentation will tell how long it actually protects a little 200mAh cell in actual use, when the user leaves the load ON.


texts: name for relay that holds state and only consumes power when toggling states

texts: I am wondering if there is a certain label or naming convention for a relay that can mechanically hold its contact state after the coil is de-energized. I thought this is what a "latching" relay does, but after some googling, it looks like latching relays hold their state by opening/closing a current path for a secondary coil. I would like for there to be no power consumed by the relay once the switch has changed state. Does such a device exist?


texts:
I want to control an analogue clock movement with a microcontroller. A Lavet motor is used to advance the hands.
The issue is detecting where the hands are. I noticed that some radio controlled clocks move the hands to midnight before moving them to the correct time.
What mechanism do they use to detect midnight position?


texts: How calculate the input offset current effect on measured voltage?

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Here is the data-sheet: http://www.mccdaq.com/pdfs/manuals/PCI-DAS6034-35-36.pdf

A data-acquisition board's differential amplifier measures a constant voltage across a resistor R1 shown in the Figure below:

Ib+ and Ib- are input bias currents and their value is +/-200pA given at the data-sheet page 30.

I'm trying to quantify the error introduced by the input offset current in terms of voltage.

I mean ideally lets say the true value of the potential difference across the R1 is V1, in that case what would be the error introduced by the input offset current in terms of V1?


texts:
I got a (relatively inexpensive) SmartYard LED Solar Spotlight as a gift, and have been playing around with ideas to extend the battery life.  It uses a 3"x5" solar panel, and comes with a 3.7V, 1400mAh 18500 Li-ion battery.

There's extra room within the housing, so I originally considered the prospect of adding a second 18500 battery in parallel.  However, several other posts here suggest there are multiple concerns/complexities associated with charging them in parallel, and with potentially unbalanced cells.

So now I'm thinking I could buy a single cell housing for an 18650 and use a (protected) 18650 instead of the 18500.  The voltage is the same between the two, so presumably I'd get added battery life, with the only cost being it will take longer to charge.

Are there other issues I should be concerned about with this approach?


texts: Is there a need to use public OUI numeration for "private" Ethernet ports?

texts:
So I'm working on a product which will have two Ethernet ports:
One for "public" network, which will be used by the customer, and one internal, within the machine chassis, which needs to be opened, which should be only used by the service technician and internal accessories.

The dogma to which I was exposed to during my network training says that all Ethernet ports should use registered OUI numbers, but on the other hand, I'm can't really think of a reason why would we need an official MAC address in this case.

So my question is:
Is there any reason why to use the officially registered OUI numbers for the internal Ethernet port?


texts: Simple relay function with 2 buttons and continuous signal

texts:
I am asking this question as I'm not too sure how to find a solution (nor how to search).

I am a real beginner in electronics and i need to make a simple circuit using a relay and 2 switches

so the basic functionality should be:

1)When I press button #1, the current goes to the motor, at the end of motor revolution, a mechanical arm pushes button #2 (the current does not stop until a full revolution is made (even if the button #1 is released).

2)When the button #2 is pressed by the arm, the button #1 should cutoff power (even if it's pressed - basically the motor should stop).

I am using a 11.2v li-po battery having 25-50C discharge rate.

What kind of relay do I need and how do I wire it?

Any help or links to answers are appreciated.

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texts:
I was trying to run my ESP8266(iot device) by watching and learning from this video.

https://www.youtube.com/watch?v=9QZkCQSHnko (only 5 mins long)

Now in the video it is mentioned that the ESP chip requires 20mA-250mA of current.

The person uses a voltage divider circuit built through resistance to regulate the voltage.

He uses two resistors of 2k Ohms and 1k Ohms respectively. Now, the minimum resistance of the circuit connected to power supply, when the ESP is connected through parallel will still be greater than 1k Ohm (least lower bound) as you will connect the ESP through parallel to the 2k Ohm resistor.

Now the power supply was of 5v in the video, and by using Ohm's law, we would get a maximum current of 5mA. How can the chip work then?