texts: Controlling Speed and Powering 12V DC Motor with Arduino and Wall Supply

texts:
first post here. I am a mechanical engineering student, but know little about electrical engineering or electronics. I am doing a project that requires me to (affordably) control the speed of a 12V DC motor. Here is the motor.

My issue is that I am unsure of what components I need to provide power to the motor and control its speed. I would like to use a wall outlet as the power supply and an Arduino to control the speed. I'd like to figure some of this out on my own, but I just need a little guidance as I walk through this project so I don't purchase the wrong components.

Can someone first give me an overview of the components required (especially for power supply)?
I believe I will get an Arduino Uno. I also think that I need an Adafruit Motor Shield. Then I'll need something to supply power to the motor from the wall. And something to supply power to the Arduino from the wall (or should I use a battery?). I'm pretty lost as far as the power supply. Transformers, transistors.. all of this is currently over my head.

I'm going to post updates to my progress and ask more questions as things are answered and I figure stuff out. If there are any guides that people can point to, that would be awesome as well.


texts: HC-12 detection by Raspberry Pi bluetooth scanner

texts:
I have bought an HC-12 module, but as much as I have investigated I have not found a way that a Raspberry Pi with a bluetooth detector called bluelog can detect it.
What do I have to do so that HC-12 wired to a Arduino can be detected with the bluetooth scanner?
How to set HC-12 in 'discoverable' mode?
Thank you


texts:
I'm trying to make a high power UPS, I have a 13.6V PSU and an Inverter and a Lead acid battery.

Everything would be connected this way:

There's a problem with that circuit, if the battery is too discharged the initial charge current will be too high for it, so I need to limit the current while charging and not while discharging.

The simplest solution would be this:

But that solution isn't very efficient. So now the next thing that comes to my mind is using a mosfet as diode, like the reverse polarity protection circuits. I only have N channel fets, so the end result should be this:

However according to LTspice that circuit doesn't work. As long as it is the default Nmos it does work, but if I try to replace it with with any Nmos in ltspice's catalog (Mosfets with a VGS above 20V), the MOSFET still conducts when it shouldn't. Why?

By the way, the MOSFET I want to use is an IRF3205.


texts: Why do we use derating factors when sizing conductors?

texts: What is the main reason behind using derating factors in case of determining the cross sectional area of a conductor and what happens if we don't take these factors into account ?


texts: What limits the speed of FPGA fabric to Mhz range, while CPU pipelines are clocked much faster? Is it the interconnect delays that places a limit on signal timing?


texts: Converting a variable frequency to TTL HIGH and LOW levels, based on a fixed (possible non-fixed?) frequency

texts:
I have a square output from an LM324 op-amp (0 and 5 volts) which has a frequency between 1 to 500 Hz (yes, low frequencies). I would like to find a simple way to have HIGH TTL signal when it is over 50 Hz and a LOW when it is below that. It's not necessary to be so precise, but around 50 Hz will be fine. I know that I can do it by uCs, and I did it. However I have 1500 outputs which I should make a network from, and I would like to make it cheap and fast.

More info about the signal: The frequency is almost fixed at something above 50, say 150Hz or may be 250Hz or so, and the frequency variation is less than 10 Hz, then suddenly it will drop to less than 50, stays for a minute and again back up.

Finally: Is there a way I can control this 50Hz threshold by uC?


texts: What are the precautions to take when building circuits powered over USB from a Laptop?

texts: I am working on a rather simple embedded system project which involves an hardware USB enabled AVR chip communicating with a host of other devices and a solid state relay which is used to make or break a 110V AC circuit . This AVR is powered over USB from a laptop . What are the precautions to keep in mind to prevent it from frying my laptop's USB port .Would a simple fuse in VBUS solve the issue?


texts: KiCad: Can I insert a net name into a footprint?

texts:
I'm new to KiCad, and using version 5.1.5.

I want to make a simple single-pad footprint, with a text label that is the net name to which the corresponding schematic pin is attached. Is there a way to do this?

Similar to how %R and %V can be used to sub in component reference/value, it seems like there should be a variable for a given pin/pad's net name... but I can't find this documented anywhere.

EDIT: What also might be useful is getting the name of a component's pin. Is there a way to get this info in the footprint editor?


texts: I am reading the specs of a DAC (this one), and it says the resolution is 10 bit. Does it mean it can generate 1024 voltage levels at the sample rate which is 12 GSa/s? It sounds pretty surreal. Can it really do communications at 120 Gb/s or what would be the practical limitation?


texts:
So I have one unused OpAmp left in my circuit and I would like to use it as "latching comparator" (for lack of a better name), but I'm having hard time wrapping my head around it. Here is how I want it to behave:

Desired properties are:

Fairly high input impedance
Works without inputs reaching rail volatges
Speed doesn't matter.

Closest thing that I found so far is
this. But I wasn't able to figure out how can adapt it to my application.

I hope this makes some sense. I'm trying to keep it abstract(quick to read), but if more detail is needed or this turns out not to be possible - I'll add in more info.

Ok, so to be more precise of what my goal is:

I'm using LM3419 as bar-graph driver chip and I need a circuit that would latch when top graph LED turns on and stay untill bottom LED turns off.
I use output of that to enable/disable some other chips.

LM3914 pulls constant current through LEDs, but I don't know what LEDs at what current I will use, hence arbitrary "high" and "low" levels.
I have one free LM358 available and I wonder if I can make it work as described.

Wanted to add schematic representation here, but it doesn't let me (need more reputation). I hope it's understandable :P


texts:
I want to simulate a simplistic "Van der Pol oscillator" in a circuit simulator such as LTspice or circuitLab.

The only circuit I found is the following:

But this requires negative resistance implementation which I don't know.
I couldn't find any whole implementation for such oscillator with its component values.

I would appreciate any help who are into the subject.

Edit:

Here I have combined pieces from net and here. So the below might be wrong:

100Hz Sine input amplitude 1V:

100Hz Sine input amplitude 5V:

Can someone explain what is going on? Is that what this oscillator supposed to output?

I'm especially trying to see non linear and chaotic behavior.

It seems one needs to be sure about the current region to operate as a negative resistance:


texts: How to increase mosfet switching speed, and decrease switching losses?

texts:
I hope this is not a too broad question, but what are the best practices to achieve fast switching on a MOSFET driven by a PWM signal?

My current knowledge tells me I can do two things:

1 - To use the lowest possible PWM frequency, because switching losses are higher at higher frequencies.

2 - Drive the gate with the maximum possible current, to overcome gate capacitance as soon as possible. To do this, I avoid adding a resistor between MCU and gate, or add a general purpose transistor between MCU and mosfet, so I can drive the gate with higher current.

Currently, I have a PWM that must run at least at 100kHz using a N-channel IRLZ44 mosfet, so first point is not applicable, and the second point is not enough to give me acceptable switching losses. My mosfets are overheating and I would like to find a better solution than using a bigger heatsink.

Should I look for a better mosfet? Or perhaps, should I try adding a capacitor somehow to kick in when PWM signal rises, boosting current through the gate? Or are there other ways to achieve faster switching?

Update:

I thought the question didn't need an example circuit diagram, but here goes it:

I got to this circuit based on other questions I asked in here. I'm using 5V and the load is about 1A. As you can see, I'm driving a transformer. In this configuration, I have 10 Vpp on transformer primary, and secondary elevates this to 1500 Vpp.

Based on current comments and answer, it's already pretty clear to me that using a driver is the easiest, cheapest and simplest way to achieve lower swirching losses. But if there's a way to improve the circuit without a driver, I would be interested on learning about it.


texts: Connect bulk in diode-connected transistor in synchronous rectifier

texts:
The diode-connected transistor is used for synchronous rectifier. I have just drawn bulk diode as below.
The fist one is mosfet with its bulk-source, bulk-drain diodes.
Second and third pictures are when B-S or B-D are connected together.
When B-D is tied together, we have body effect and this increases threshold voltage. However, we get a diode from D to S. I think this diode is good because it helps make the diode-connected transistor more like a real diode.

With the case B-S connected, we don't suffer from body effect but we don't have the help of diode from D to S.

So, my question is which one is better in this case, connect bulk with source or drain?


texts: Is there any reason why 5 volts is so ubiquitous for powering small consumer electronics?

texts:
So pretty much every phone charger, tablet charger outputs 5 volts.

5 volts was part of the original USB specification which I assume had some influence on this, resulting in it just being easier to design things to be powered by such a common power source.

However is there any good reason why 5 volts was chosen?


texts:
I have made this clap switch.It is working fine presently. I need suggestions for improvement for its long term use.
Specifically I want to know if the capacitor based power supply is okay in this circuit and wont damage the components in long run?


texts: Xilinx ISE warns that a signal is trimmed since it has a constant value of 0, but the signal is used within my code

texts:
I have created the following VHDL module, which is used as an up/down counter.

entity counter is
Port(clk        : in  STD_LOGIC;
     count_clk  : in  STD_LOGIC;
     reset      : in  STD_LOGIC;
     count_up   : in  STD_LOGIC;
     count_down : in  STD_LOGIC;
     counting   : out STD_LOGIC;
     value      : out signed(19 downto 0));
end counter;

architecture Behavioral of counter is
    signal temp_value   : signed(19 downto 0) := (others => '0');
    signal last_clk_val : STD_LOGIC           := '0';
begin
process(clk, reset)
begin
    if (reset = '1') then
        temp_value <= (others => '0');
    elsif (rising_edge(clk)) then
        if (last_clk_val = '0' and count_clk = '1') then
            if (count_up = '1') then
                temp_value <= temp_value + 1;
            elsif (count_down = '1') then
                temp_value <= temp_value - 1;
            end if;
        end if;
    end if;
end process;
last_clk_val <= count_clk;
counting     <= count_up or count_down;
value        <= temp_value;
end Behavioral;

ISE presents me with the following warning (for each bit of temp_value):

WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <ttl_top_inst/COUNTER_COMPONENT/temp_value_0> has a constant value of 0 in block <ttl_oneshot_inputs_top>. This FF/Latch will be trimmed during the optimization process.

Adding the Following lines to the code marked with --ADDED LINES removes the warning, but temp_value should not be altered at that point of the code.

entity counter is
Port(clk        : in  STD_LOGIC;
     count_clk  : in  STD_LOGIC;
     reset      : in  STD_LOGIC;
     count_up   : in  STD_LOGIC;
     count_down : in  STD_LOGIC;
     counting   : out STD_LOGIC;
     value      : out signed(19 downto 0));
end counter;

architecture Behavioral of counter is
    signal temp_value   : signed(19 downto 0) := (others => '0');
    signal last_clk_val : STD_LOGIC           := '0';
begin
process(clk, reset)
begin
    if (reset = '1') then
        temp_value <= (others => '0');
    elsif (rising_edge(clk)) then
        if (last_clk_val = '0' and count_clk = '1') then
            if (count_up = '1') then
                temp_value <= temp_value + 1;
            elsif (count_down = '1') then
                temp_value <= temp_value - 1;
            end if;
        else --ADDED LINES
            temp_value <= temp_value - 1; --ADDED LINES
        end if;
    end if;
end process;
last_clk_val <= count_clk;
counting     <= count_up or count_down;
value        <= temp_value;
end Behavioral;

The code works without problems in the simulation, but I know that the simulation does not equal the actual implementation.

Could someone give me directions on how to fix this problem?
Thanks in advance!


texts:
I built the following circuit on a breadboard:

Assuming rails of \$V_{DD}=3\text{ V}\$ and \$GND=0 \text{ V}\$, and an inverter switching threshold in the middle, one can calculate the theoretical period of oscillation as \$T=2 \ln(3) \text{RC}\$, which for the values I have translate to a frequency of \$f = 1/T \approx 4.5 \text{ kHz}\$. (You can see the exact and more general calculation here). As you can see, a switching threshold not perfectly in the middle is a pretty minor error.
But when I built the circuit on the breadboard (verifying all my parts are the right values), I instead got around 5.6 KHz.
What I notice from probing the circuit is that \$V_1\$ doesn't get pulled up quite as high or as low as it theoretically should, although the error in the negative direction is more pronounced. Since it doesn't go as low as it should, it gets back up to the switching threshold more quickly and so that part of the period is shorter than expected, thus higher measured frequency.
What's the most likely root cause of this? My first thought is the unequal drive strength of the inverters, although I don't know if this is expected to be a major issue for a discrete CMOS inverter (like I'm using).


texts: why is the gain of ad620 not responding to the change in( Rg), the gain resistor?

texts:
I am building an ECG sensor based on the AD620 instrumentation amplifier.For the purposes of testing , i have built a simple AD620 circuit with pin 2(-) and pin 3(+) connected to a 2.82mV(peak to peak) sinusoidal signal generator. pin 7(+Vs) is connected to +4.5,pin 4(-Vs) is connected to -4.5. a 33k Ohm resistor is connected between pin 1 and pin 8 which theoretically should give a gain of around 2.5. Pin 5(Vref) is grounded and pin 6(output) is connected to an oscilloscope with ac coupling.
1)My first problem is the signal on the scope is 282mV peak to peak which implies a gain of 100, how can this be explained and solved?
2) if I change the gain resitor from 33k, to 37.7k, to 70.3k, I still get the same output.
3)if I change the input signal from 2.82mV peak to peak to 0.91mV I stil get the same output swing, however if i switch off the signal generator the output goes to zero.
I have also tried to connect 33k resitors between each input and the ground but the result is the same.


texts:
In another post, Diode circuit with parallel voltage source, many of the top answers quickly claim that the voltage of interest in the circuit must be greater than 1 'by inspection'.

I'm very new to this and so I can't see how this is true. I tried to understand this by guessing the answer to be 2V, and then the top two diodes would be reverse biased, leaving only the bottom diode on. But I can't anything more from this and how this indicates a conflict.


texts: Okay for USB to send data without specific OUT command first?

texts:
I have been going back and forth between writing software for my device and the PC application trying to get the protocol right.

I have a pic18f4550 talking over interrupt transfers.  It needs to regularly send the status of up to 128 switches, and also maintain the status of pin outputs based on commands from the PC (on/off, pulse, blink, etc).

Much of the examples I have encountered place IN-transfers inside of a block that makes sure an OUT-transfer always happens first, like this libUSBDotNet example.  If there is no OUT data ready then no IN request will be made either.  The template firmware was initially set up to handle something similar - It would always wait for there to be data in the OUT buffer, handle that, then set up the IN buffer and send.

When I got started I thought it was overrated, because my device was always going to send the switch status if it had the information and always ready to the commands should there be any.  I adjusted my application to send OUT transfers and IN requests independently, and the firmware to handle each independently.  But as my code gets more complex, I wonder if I was missing something.

If I ensured the OUT-IN back-to-back structure, I could reserve one or two initial OUT bytes to include a command to send the switch update.  It would also allow me to easily stop requesting the data.  Of course I could leave it as is and have certain commands reserved to set flags that would enable/disable certain behavior on the data collection/transfer side.  I still don't know what might be necessary at the end of this project, so I guess I am looking for advise for best practice, and pros/cons of approaches.  Or maybe I'm way overthinking this.

Thanks.

EDIT:  Also, ping-pong buffer mode is turned off on my chip, so there are dedicated buffers for the IN EP and OUT EP, if I am not mistaken.

C# code (i've ported this into pyUSB as well).  Compare to the libUSBDotNet sample I linked to.  Run every 10ms with a timer

private static void RunUSB(Object source, ElapsedEventArgs e)
    {
        ErrorCode ec = ErrorCode.None;

        if (true) // for now always do this.  In future only if we have commands to send.
        {
            int bytesWritten;
            ec = writer.Write (commands, 0, 3, 2000, out bytesWritten);
            if (ec != ErrorCode.None)
                throw new Exception (UsbDevice.LastErrorString);
        }

        int bytesRead;
        byte[] readBuffer = new byte[64];
        ec = reader.Read(readBuffer, 2000, out bytesRead);
        if (bytesRead != 0)
        {
            //handle input data
        }
    }

Firmware code (using mStack)

// initialize endpoint 1 IN buffer
unsigned char *INPacket = usb_get_in_buffer(1);
memset(INPacket, 0, EP_1_IN_LEN);

    while (1) {
        if (usb_is_configured())
        {
            // get data from PC
            if (usb_out_endpoint_has_data(1))
            {
                unsigned char OUTLen;
                const unsigned char *OUTPacket;
                /* Data received from host */
                OUTLen = usb_get_out_buffer(1, &OUTPacket);

                // do stuff with OUT data
                // rearm for out data
                usb_arm_out_endpoint(1);
            }

            // send data to PC
            if (!usb_in_endpoint_halted(1))
            {
                /* Wait for EP 1 IN to become free then send. This of
                 * course only works using interrupts. */
                if(!usb_in_endpoint_busy(1))
                {
                    // fill INPacket with data
                    usb_send_in_buffer(1, byteCount);
                } else {
                    // send something
                    INPacket[0] = 0;
                    usb_send_in_buffer(1, 1);
                }
            }
        }
    }

Note that the if (!usb_in_endpoint_halted(1)) was originally inside of the if (usb_out_endpoint_has_data(1)) block


texts: Should the AC-Live or AC-Neutral wire be 'broken' by a relay?

texts: I have a 230VAC relay that will switch my bathroom light as well as the extractor fan. The question I have is whether the Live/Phase wire or the Nutral wire go through the relay?


texts:
When I read it, I think a \$2\$-digit BCD number is something between \$0\$ and \$99\$ in decimal. So, for example, \$0100 1001\$ is a \$2\$-digit BCD number and decimal equivalent of it is \$49\$ in my opinion.

However, this question confused me. I want to interpret \$A_0\$ or \$A_1\$ as a \$4\$ binary digits, representing a decimal number(BCD). And the circuit will add two \$2\$-digit binary numbers then. However, in such a scenario, I would expect to see an output labeling either as \$S_0\$ and \$S_1\$, which will also correspond to \$4\$ binary digits, but will represent BCD. Or, I would expect to see \$S_0\$ to \$S_7\$, each representing one binary digit.

In short, I am stuck in this question. Either I have some misunderstandings about wording, or I just don't get it.

I would appreciate if someone explains what this question wants to tell.


texts: What is a typical value for the gain of a smartphone's Bluetooth (or Wi-Fi) antenna?

texts:
I can't find specific values for transmitter and receiver gain anywhere. Very often the Bluetooth module is together with the Wi-Fi module, so a Wi-Fi antenna gain value will help me as well.
I need to find the value in order to use it in some path loss formulas, but my smartphone's spec does not specify the value, so it would be useful to know more or less what a typical value would be for a smartphone.


texts: minimum spacing between hobby circuit board edge and DIP IC

texts:
Since I don't run a labratory and I have a standard printer capable of printing 600 DPI, I'm trying to make a small circuit board but I'm wondering, whats the closest I should place the pins of a DIP IC to the edge of a circuit board?

My normal track settings are 0.3mm thickness, 0.3mm minimum spacing between everything.

I am at a hobbyist/amateurish level so I don't want to screw up my circuit only because an IC is too far to the edge.


texts: I have a circuit that is calling for a 400v capacitor to be used.  I only have 1000v available.  Can I susbtitute it and use the 1000v?


texts: MPLAB XC16 compiler outputting 8-bit HEX files for PIC24?

texts:
I am trying to understand a HEX file I compiled with Microchip MPLAB X IDE using the Microchip MPLAB XC16 Compiler.

Concerning the MCU, I am targeting the PIC24EP512GU814. However the scope of this question should at least apply to all PIC24 MCUs.

To compile the example HEX below, during the "New Project" wizard, I selected Samples > Microchip Embedded > PIC24 C Template and picked the XC16_24EP512GU814 configuration.

According to the PIC24EP / dsPIC33 Datasheet section 4.1.1 page 48, The memory is segmented into 16-bit words, such that each position (0x0000, 0x0001, ...) contains 16 bits. On the same page of the datasheet, program instructions are said to be 24-bit and span 2 words, such that the most significant byte of the most significant word is zero (00000000b).

This does not appear to be consistent with the compiled HEX file. Here are the first 5 lines of the file, numbered and with the different parts spaced out according to the Intel HEX specifications.

1. :02 0000 04 0000                             fa
2. :08 0000 00 0002040000000000                 f2
3. :02 0000 04 0000                             fa
4. :10 0008 00 c8020000ce020000e4020000d4020000 92
5. :10 0018 00 da020000e8020000ec020000e0020000 42

Consider lines 4 and 5. The first field correctly counts 0x10 (16) bytes in the data field. However, the second field which denotes location in the memory jumps from 0x0008 to 0x0018, or 0x0010 (16) positions.

From my interpretation, this means that this particular HEX file is 8-bit instead of 16-bit because each position is occupied by one byte.

Is there a way to make the compiler output a 16-bit file?
Is this file still valid for a 16-bit MCU? How can I interpret the HEX file so that I can manually flash the MCU?


texts: I want to record some lectures I am giving next semester.  I have a video camera, and can change its direction using a servo of some sort.  However I have no idea how to detect where I am.  Me carrying some broadcasting device would be fine.  Mostly the sensitivity should be able to determine if I am in the left or right side of the room, but I do not need much more than that.


texts: We want to be able to design a PIC microcontroller based timer. The specification requires that we have a time for at least one month (30 days). I have been trying to figure out how one can do that but I am stuck. Any suggestions please?


texts: Truth Table for 3-into-8 decoder with N.A. inputs, P.A outputs and enable

texts:
I'm working on an assignment where I need to draw a block diagram and the gate-level circuit of a 3-into-8 decoder with negative active inputs, a positive active
enable and positive active outputs.

I've drawn the block diagram, but before I draw the circuit, I wanted to do a truth table so that I made sure my logic was correct. And this is where I'm having some trouble. Normally, I think my table would look something like this. But with the inputs having negative active logic, I'm not sure how that will affect my inputs and change the overall truth table. I've always had a lot of trouble figuring out how N.A.L affects the overall circuit; could someone please help me out?


texts: Can someone please help with Electronics transient/capacitor question?

texts:
Can someone please help with Electronics transient capacitor question ?

The answer I keep getting is a minus so I think obviously I am wrong.

This question is in this link

from my class notes the only information I have to answer the question is

\$\cfrac{V}{2}\left(1-e^{-\frac{t}{\tau}}\right)\$

tau = 3R/2 (c)

c = 2x1x0.001 / 3xRxLog(0.9)


texts:
This is a fundamental circuit question. Suppose two nodes of a circuit are always kept at the same voltage by some unknown mechanism. If I now connect these two nodes with a wire, would it introduce any changes to the operation of the circuit?

For example, in an ideal op-amp, the two input terminals have equal voltage. However, I've heard some say it's incorrect to think these two terminals are shorted. Why is that? If these two terminals are always at the same voltage (as we are assuming an ideal device), shorting them wouldn't make a difference, would it?


texts:
I'm trying to drive high power LEDs with a laptop power supply, and wondered if I should use resistors to limit the extra current, or something like this to limit the current. If I did use that module, I would run it at 55V @ .7A

I'm aiming for decent efficiency without designing my own module. The laptop power supply I'm using is rated at 19.6V @ 4.62A. From there, I could either use a (cheaper) boost converter like this, which only limits voltage, and from there use resistors to limit the current. Or I could use the more expensive first linked module to regulate current and voltage. Which is better, in terms of efficiency?

I feel like the boost converter would be more efficient, but everyone else's circuits use resistors to limit current. Is there something I'm missing?

If I've made any incorrect assumptions, please tell me. I want to make sure I do this well.


texts: Driving a 12VDC solenoid from a 24VAC signal

texts:
I would like to put together a circuit that does the following function:
1) You input 24VAC.
2) It outputs 12VDC pulse to drive a 3W, 4Ω latched solenoid.
3) Once 24VAC is removed, it outputs a negative outgoing 12VDC pulse to unlatch the solenoid.

The idea is to latch and unlatch a DC solenoid from a 24VAC signal which comes from a controller.

How do I drive a 12V solenoid form a 24V signal?


texts: What signal loss can I expect by routing a 20 dBm 900MHz signal in a 90° curve in a PCB?

texts:
I would like to change a PCB to add a (not straight angle) 90° curve in a 900MHz signal path.

From my understanding my PCB designer is simply using the correct impedance, routing the signal on the top layer and using the ground plane below as a return path.

From his experience it would be advisable to simply use a right angle connector outside of the PCB, and doing another 90° curve inside the PCB is a bad idea (we already have one, but at -10 dBm).

I would like to understand what kind of problems another 90° in-pcb signal path curve would bring (only signal attenuation? Or distortion as well?) and if that depends on the power of the signal doing the curve (eg. would a -10 dBm signal be less affected than a 20 dBm one?).

Thank you.


texts:
I have a system that is powered by a 25V Lithium ion battery pack. I need to test the system with a 1 Vpp sine applied on top of the 25V supply, so 25V +/- 0.5V ripple.

I know theoretically to get this signal I could use a function generator generating a sine wave and feed that through a series capacitor, but is having an AC signal applied this way bad for the battery?
Can I put a large inductance between the battery and the capacitor such that none (or very little) of the AC voltage is seen at the battery?
Does the function generator need to be able to source much current?

The system may pull 1 to 2 amps maximum.


texts: Help in understanding Store Word (SW) instruction in Risc-V

texts:
So this is what I understood from what my professor said, but I don't think it's the right answer. What am I doing wrong? I'm sure It's just some small thing that I'm getting mixed up.
Given instruction: SW x8, -6(x4)
What I thought it meant: Take the content of source register x8 and subtract 6 from it. The result gives the memory address. Now, store the content of register x4 into the obtained memory address.


texts: I'd like to make a simple audio mixer that takes in line level signals from various mp3 players, computers, etc. I found a simple schematic online, but I'm wondering if this will be okay for my purposes. Do I need some sort of DC blocking in this circuit? I just want to ensure this won't damage any components I plug into it.


texts: Current Transfomer (CT) ratio setting on energy meter

texts:
I am using a smart energy meter which allows me to set the CT ratio among other parameters. I am using 50/5 ratio AC CT's. For the meter to do the kwh calculation correctly, I believe I have to set primary CT ratio to 50 and secondary CT ratio to 5. Now, if I have two rounds of the same 120 volt wire passing through the same CT, then I would set secondary ratio to 100. My question is, will this be equivalent to have just one round of wire through the CT and the primary ratio set to 50 , i.e the kwh calculated by the meter will still be right and I would'nt have to do any manipulations on the values obtained from the meter.

Meter data sheet: http://www.elmeasure.com/downloads/pg_5310.pdf


texts:
I'd like to mount a heat sink on a Sharp S202S02 SSR. Here's a drawing the indicates that the back surface of the device might be connected to AC:

In the "Design Guide" section of the datasheet it is recommended to add insulation between the device and the heat sink. That's quite clear. However, I still don't know if a metal screw used to mount the heat sink could still lead to a short between the back surface and the heat sink.

Does mounting a heat sink with a metal screw cause a short between AC and the heat sink, even if I add sheet insulation between the device and the heat sink?

I can of course use a nylon (or other plastic) screw, but it will get as warm as the SSR and degrade over time. Another option is to use a smaller screw and add a nylon sleeve, although the SSR's mounting hole is made for an M3 screw.

Here are photos of the real device. The first one shows the front, including the small area that is common to pin 1:

And here's the heat sink side. No metal to be seen:

It's all plastic, except those small rectangles at the front.


texts: How to make a chip with lots of pins in Logicworks

texts: I'm trying to make a mux in logicworks. I was already able to make a simple one. But now I'm trying to make one that has lots of pins. There will be two sets of 32 pins for the input, a select pin, and 32 pins for the output. Is there some way I can make this simpler than having 97 pins on the outside, maybe by using buses?


texts: Can a Nintendo 3DS battery be used to power a pcb?

texts:
I just bought a power bank pcb for a diy project I'm planning. The PCB requires a lithium ion battery with 3.7 volts as input. The power bank then outputs 5v to 2 other PCBs. Can I use any Li-ion battery that meets this requirement? More specifically, can I use a Nintendo 3DS battery (which meets the requirement).

The other PCBs are a Bluetooth receiver and an amp if that matters.

Edit:

Links

Power bank:
https://www.banggood.com/Dual-USB-5V-1A-2_1A-Mobile-Power-Bank-18650-Battery-Charger-PCB-Module-Board-p-1031593.html?cur_warehouse=CN

Bluetooth pcb:
https://www.banggood.com/Stereo-Audio-Amplifier-Module-Wireless-Bluetooth-Receiver-USB-Power-Support-TF-AUX-p-1100590.html

Battery:
https://www.banggood.com/Wholesale-2000mAh-3_7V-Rechargeable-Battery-Pack-for-Nintendo-3DS-p-39495.html

Amp:
https://www.bidorbuy.co.za/item/333899725/PAM8403_5V_2_Channel_3W_Mini_Digital_Power_Amplifier_Module_Board_For_Arduino_LOCAL_STOCK.html


texts:
I am trying generate guided waves on simple metallic plate through piezo-ceramic material, I place two piezo on the surface of the plate at the different location and through Arbitrary pulse generator, I generate the Gaussian pulse of 150KHz and excite the one piezo. This excitation generate guided waves which is sensed by the other piezo. but the problem is, the output signal has very high noises and very low SNR ratio, I hardly even see the signal on the oscilloscope, but whenever I switch to the normal sine wave of the same frequency, and shut off the arbitrary and burst option, then the output signal will have very high resolution and SNR value.
Please someone guide me how to reduce signal noises,


texts: SD card communication failure with USB2244 and TS3A27518E

texts:
friends!
I'm facing a very peculiar issue on a hobby project of mine, and would appreciate any insight.
The schematic for the relevant part of the project is attached at the end of this post. What I have is two microSD cards (J1 and J2 on the schematic) connected to a USB2244 card reader (U4) via two analog switches: a TS3A27518E for the data lines (U7) and a TS5A12301E for the power lines (U5). The design is based on the evaluation board for the USB2244. The CARD_SELECT and NCARD_DETECT lines are connected to a microcontroller (not shown) and are used to select one of the cards and inform the reader that a card was inserted, respectively.
The problem I'm facing is that the card reader fails to establish communication with the card. I attached a logic analyzer to the card end (using a handy sniffer), and after pulling the NCARD_DETECT line low I'm seeing the following pattern play out on the SD's CMD line:

The reader sends the CMD0 command, AKA GO_IDLE_STATE. According to the spec. I have access to, this should order the card enter an idle state.
After ~3ms the reader sends CMD0 again.
After ~3ms the reader sends CMD8 with the argument 0x1AA, indicating that it supports voltages in the range 2.7-3.6V, and a check pattern of 0xAA.
The card responds with a response type R7, and returns the same value of 0x1AA.
Steps 1-4 are repeated.
The reader sends CMD55 (APP_CMD), indicating that the next command is an "application-specific" command.
The card responds with R1 and a value of 0x120, which is interpreted as:

CURRENT_STATE == Idle (bits 12:9 are 0).
READY_FOR_DATA.
APP_CMD, i.e. the card expects an app command next.

The reader sends CMD41, with an argument of 0x40FF8000, which is interpreted as:

The reader supports SDHC or SDXC (bit 30 is set).
The voltages supported by the reader are 2.7-3.6V (bits 23:8 are set).

The card responds with R3 and a value of 0x00FF8000, indicating that it supports the same voltages, but that it is busy (bit 31 is not set).
The reader sends CMD55.
The card does not respond.
After ~100ms, the process repeats from step 1.
The whole dance stops after ~1s, with the card reader powering down the card.

The voltage on the SD card stays at a pretty much constant ~2.9V during the whole process, with a momentary (~0.6us) dip to ~2.2V at step 9, where the card responds to ACMD41. Note: now that I'm writing this, could this dip be an issue, if the minimum voltage should be 2.7V? What in the circuit could be the cause?
I've ruled out the card and sniffer as an issue, as they work just fine with an actual card reader, as opposed to my contraption.
I've also recorded the voltages on the CMD and CLK lines, and the waves look pretty square to me:

From looking at the Texas Instruments forums, it seems other people also had issues with the TS3A27518E when using it to access SD cards. These other people talk about capacitance issues, so perhaps that's what I'm seeing? How can I diagnose this?
Any help would be greatly appreciated. Thanks.


texts: Can I share a single pull resistor on multiple enable pins to save space?

texts:
I am using this Schmidt trigger IC SN74HCS125 which has 4 channels
I would like to save some board space by hopefully using only one resistor to pull down the enable pins of each channel. I do not plan to connect those enable pins to anything else as I want them to be always enabled.

simulate this circuit – Schematic created using CircuitLab
I have not done this before since what I have been doing since now was individually giving them their own resistor. Just intuitively speaking it should work, but there might be caveats that I am not aware of. Is doing this perfectly fine?


texts: Voltage divider does not work with LM393 sound sensor

texts:
I have a sound sensor which I want to connect to a RaspberryPi.

RaspberryPi input voltage on GPIO is 3.3V and this sound sensor output gives 5V.

I've made voltage divider that looks like this:

It works fine when I connect it with power supply. It gaves me ~3.1V on V out.

However when I connect it to sound sensor it does not give me the expected voltage.

My circuit looks like this:

Output voltage is ~2V and voltage between sensor output and resistor R4 is ~3.3V.

I've also noticed that the small diodeon sensor (which lights when sound is detected) lights a bit when circuit is connected that way.

What might be causing this problem? Should I add a diode between R4 and sensor output? Will this solve the problem?

This is the circuit of the sound sensor:


texts: Using 2 outputs on an arduino to drive a motor

texts:
I have a small motor which I removed from a mobile phone. I want to control it from a digital output on my Arduino board.

Will I damage it if I connect the motor directly to to the board and it needs more power?

Can I use 2 outputs of the Arduino together?

I know the best way to do this would be to use a transistor as a driver but I'd really like to avoid it since I don´t have it on stock and it is cold in Copenhagen now.


texts: What is a typical example of a combinatorial feedback loop?

texts:
By looking at some of the details of the Altera timing analyzer TimeQuest, the concept of a "combinatorial feedback loop" was mentioned. The obvious search is not terribly helpful and there doesn't seem to be a Wikipedia article on the topic.

What exactly is a combinatorial feedback loop in the context of FPGA and ASIC design? Is there a typical example to illustrate the concept?

If an example is provided using an HDL, I much prefer Verilog over HDL.


texts: Is the grounding of the breadboard common used?

texts: Is the ground of the breadboard common used ? I mean can i connected two different voltage producer (voltage supply) ground pins in the some negative hole in the breadboard?


texts: multisized 7-segment displays in a circuit

texts:
I want to use 1-inch & 2-inch 7-segment display in a digital clock based circuit(six 2-inch display in a row & six 1-inch display in another row). I am using 74hc164(serial in parallel out shift register ic) for controlling 1-inch display.Data, clock and reset pin of 74hc164 is controlled by PIC microcontroller. QH pin(13th pin) of the ic is given to the data pin of the next shift ic and goes on.
        Since the forward voltage of 2-inch display is 9.6v, 74hc164 cannot be used(6v max).I got CD4015 with similar properties of 74hc164 and works well on 12v.

My question is, how can I connect the clock and data pins of 74hc164 to cd4015 since the operating voltage is different?.

please suggest a solution for this...

Thanks and regards,
Nikhil


texts:
I want to synchronize two atomic clocks at the same location to the same time... then let them run independently of each other (then I'd move them apart).

Is there some standard procedure to accomplish this?

Do standard atomic clocks come with inputs/outputs to accomplish this task?

EDIT: I haven't purchased the clocks yet.


texts:
I am reading about single stage CE amplifiers and I don't understand how the capacitors work here.

1) Coupling capacitors:

  The coupling capacitor is used to isolate the DC of one stage from the next stage and allows the AC signal only.

As per my understanding, when an AC input is given to a capacitor, it superposes with the AC bias voltage and we get something like this:

This is again only an alternating signal. There are no DC components. So, why do we need the capacitor? I found an answer on the internet that said that the capacitor removes the DC bias voltage from the output signal. But how can this be? Once an AC signal superposes with a DC, it still remains an AC, right (like the one above)?

2) Bypass capacitor:

  Bypass capacitors provide low impedance path to unwanted AC signals.

Below is a circuit diagram.

How are these "unwanted" AC signals filtered from the output? In the first place, do these signals even come from the output?


texts: Reverse polarity protection for a very low voltage devce

texts:
I want to add reverse polarity protection to a device which is powered by a single AA battery, so its voltage might go down to 0.8 V. Forward diode is too huge of a drop. I've already thought about adding P-MOSFET but what bothers me is a diode's forward voltage. It's usually around 1 V. What it means is that if battery is inserted the right way, MOSFET won't be open because Vgs is not high enough. As I understand, if after diode voltage is high enough, MOSFET will be opened and diode won't matter anymore. Am I wrong or should I consider other ways to implement reverse polarity protection?

Just to be clear what circuit I'm talking about:

I was considering Si2329DS which has a maximum Vgs of 0.8 V but diode voltage leaves it unusable.

edit:
So, I've been doing some research and I've found ideal diode controllers that enable me to use NMOS. I'm going to tell if I find something suitable


texts: Could I replace the antenna of a USB dongle with a RP-SMA connector?

texts:
I'm looking to replace something like this antenna shown:

with an RP-SMA connector. Would this work and if so, how would I do it?


texts: What happens if my SSR output voltage is rated higher than than my expected throughput?

texts:
I have a solid state relay (pictured below) rated at 24-140 VAC output, and I'd like to use it for digitally controlling a 12 VAC circuit.

Will I be able to use this device? In the case that I can't, why not, and what will happen to the SSR?


texts: What is the basic principle for a cmos vcc detector circuit?

texts: Most systems that have any controller/firmware need to know when to start powering up. I would imagine this might need a powerup circuit or a detector that trips when we are at an acceptable voltage. What is the basic principle of such a reliable vcc detector? I am starting to learn analog circuit design and would like to know how this is done in cmos in particular.


texts:
We are a design using 3 decoupling capacitors the value are 47 uF 16 V X5R, but we are having trouble with the supplier.

I have an idea to replace them with 1 capacitor 100 uF, 1 10 uF and 0.1 uF.
This value is common to find them.
Anyone has a better value to be replaced this 3 decoupling caps?

Thanks


texts:
I am designing a board with Ethernet input, but would like to have the Ethernet re-routed.

So the board should have two RJ-45 connectors, one which is the main Ethernet (board is using this port for accessing the network), and another which is just re-routing of Ethernet signal.

(Ethernet) --> My Board --> (Ethernet) --> PC(or another board).

I have looked around for a description, circuit or chip for doing this, but with no luck.

I have found the passive 3-port Ethernet hub, but I'm not sure whether that circuit is any good for my application.


texts:
I am using LT3751 for the first time, tried alot but no luck need help.

I am using the chip in regulation mode and following the circuit given in datasheet on page number 26 with title "High Voltage Regulator."

I want to generate 500V but the problem is the output is stuck at 260V.  It never increases above no matter what I change in the circuit.

Few observations on oscilloscope to share:

1- At startup there is spike of 2.48V on FB pin which falls down and reaches to 1 volt.

2- FB pin is always noisy.

3- At load greater than 20K after around 100 ms fault pin goes low. At 16.6K load 260V is sustained. Does the chip require some minimum load for operation?

Following are my specifications:

Vtrans =  28V

Vcc     = 22V

C2     = 0.22uF 50V

RBG, RVout, Clamp pins are GND with 0 ohm resistor.

Output capacitor (C4) = 100uF 900V

M1 NMOS (MOSFET) = IRF510

C10 = 1uF 25V

R1 and R3 = 100K

R2 and R4 = 600K

D1 = 8S2TH061

Charge pin is pulsed using RC circuit.

Rest is same as the circuit in the datasheet.

Circuit diagram:


texts: Diode bridge working only as half recitifier

texts:
I am trying to simulate diode bridge using 12.

In the image below you can see the circuit and the simulation of the circuit.

So my question is, why does this circuit does not behave as full-wave recitifier? It is only passing a half wave, the negative one.

Thanks for the help!!!


texts: Required crystal frequency for MCP2515 with ATmega328P

texts:
I want to connect a number of ATmega328P microcontrollers over a CAN bus. I found out that I will need some MCP2515 and MCP2551 ICs. In different schemas I sometimes see a 8 MHz crystal on the MCP2515 and sometimes a 16 MHz crystal.

This is the desired setup:

Multiple ATmega328P chips for a home automation project. The amount of data to be sent is really limited: switch on relay, switch off relay... so the speed on the CAN bus can be low.

What frequency should I take? Or doesn't it matter? Do I need to specify anything else needed to make the decision?

Is the use of a crystal on the ATmega required? Or can I use the internal clock of 8 MHz or 16 MHz?


texts: How to route Gigabit Ethernet, remote PHY or remote RJ45 connector?

texts:
I need to design a 10/100/1000 BASE-T “backplane” board that contains multiple  PHY outputs from Ethernet controller chips. On the board ,the LAN specifications are very strict in regard to how the LAN silicon(PHY) is situated to the magnetics and the RJ-45 connectors. My questions are primarily how to interface to an off the board RJ-45 patch panel that could be anywhere from ~2” to 28” away. Various forums have “addressed” this in the past, such as “For remoting 1000Base-T Ethernet connector, is it better to remote PHY from magnetics or magnetics from connector?”. One opinion is to place magnetics close to the PHY and remote the connector. Another opinion is to put the magnetics close to the connector, remoting the PHY.

Which of the two, remote the connector or remote the PHY, is “correct”/ easier to implement for maintaining signal integrity and minimizing EMI?

What is the maximum length that is possible to remote the PHY or the connector?

Do I have to run the long lengths off the board?

How does a 48 or 96 port gigabit switch run their signals while maintaining signal integrity?

Are there any definite specs on how to proceed? Thanks in advance.


texts: How do I design a clocked synchronous state machine for a combinational lock?

texts:
I need help in completing a task, I’m stuck on quite a few things. Since I’m very new to this topic on finite machines.

I’ve attempted the state diagram, state table, transition table, K-map values and the k-maps (Karnaugh - map) themselves. However, a lot of it is incomplete, because I don’t know how to continue.

Any hints or help is appreciated; I’m not asking for answers just guidance, I’ve tried for a whole week now but still failed to complete this.

You can read my task down below. And in my drawings are questions highlighted in yellow, showing where I’m stuck, or where I’m having the most trouble in figuring out a solution.

Task:
Design a clocked synchronous state machine for a combinational lock with two inputs (X and Y) and one output (Z).

Input ‘X’ is used to initialise the sequence entry. Input ‘Y’ is used to enter the binary sequence to unlock. Output ‘Z’ will be turned on if and only if the binary sequence is entered in proper order after the initialisation and must remain on as long as X input remains high.

This combinational lock operates as follows. Input ‘X’ must have changed from low to high in the previous clock period and should remain high afterwards (Initialisation). Entry of first binary digit must be done before the next clock cycle starts and entry of the remaining digits is done on the subsequent clocks.

If a wrong sequence is entered, it will require re-initialising to start entering the correct sequence.

My tables and drawings for this task:

UPDATE!

State diagram

State Table


texts: How can high temperatures be measured with Arduino uno and type k thermocouple with out maxing out 500 degrees C.?

texts:
I need to measure temperatures of around 1000 degrees C using an Arduino Uno (later to be used for PID control), but firstly I need to overcome the challenge of measuring temperatures greater than 500 degrees C (this has been achieved). Since the board operates at 5V, and is 10 bit, the resolution is 5V/1024, and the thermocouple and AD595 amplifier roughly give an output of 10mV/degreeC, I am struggling to work out how I can measure temperatures greater than 500 as 500degreesC = 1024 (the greatest number possible). As far as I can see, if the board had an operational voltage of 10V then this would be possible as 10,000mV = 1000 degrees C.

Are there any ways I can do this with just my 5V Arduino Uno board? Any hardware that can take the milli-voltage from the thermocouple (and thermocouple amplifier) and scale it down so that the arduino board does not max out at 1024 at 500 degrees C? I hope this makes sense, electronics is not my forte. Thanks.


texts: Light illumination method for video camera and CV detection

texts:
My control application implements human face detection and recognition with using of CV library. My device uses usual VGA USB video camera.

Problem:

Good and uniform light illumination allows detect and recognize face successfully.
Poor and uniform light (semidarkness), also allows detect and recognize face successfully.
Side lighting makes it difficult for detection

I've tried to create  haar cascade xml of half-lit faces and even use haar cascade of human face profile, but in both cases I have same result, detection can not manage this data correctly. The first way provides multiple extra detection of similar shadow relief, because half-lit face is too amorphous when moving and it is very difficult to determine appropriate data for it. Profile of the human face does not gives any results, except of detection of profile, for what it is intended, also with good illumination, but of course can not be detected as a half-lit face.

Recognition process itself not involved in the problem, because with detection I can process any object if it is matches example. In this question, I need to solve the problem of facilitating the camera to get a good quality video image with uniform light for successful detection.

I'm not sure, how it work with other devices or methods, but my phone with Android, Windows phone and iPhone all has a same problem with detection of half-lit face.

I've tried attache some kind of light source to my device to provide good direct light, but two problems arise, first, even if it is soft, not a very bright light, it is still directed to the eyes, what causes discomfort, and also getting of external light into the field of view causes overexposure, what affects detection even more than the lack of light.

Any advice about proper approach to this problem, for example, some suitable device, method, light source, maybe possibility of infrared light with CV etc., would be very helpful


texts: Lithium Ion Battery Pack - Looking to calculate watt-hours from V1 to V2

texts:
I've got a 2S4P Lithium Ion 18650 pack (that's 2 sets of 4 cells in parallel where each set is in series).

These batteries can be changed to typically around 4.1 or 4.2v and can technically be discharged low (2.5v), however the wider this range, the less life you can our of the cells. I plan on charging my cells to 4.2v and providing a voltage cutoff at 3.0v.

What I'd like to understand is how I get capacity (in watt-hours I believe?) out of the voltage range I've selected.

Let's assume each cell has a rated life of 2000 mAh.


texts:
I'm trying to make a 128-bit divider in Logisim using Logisim's built-in arithmetic library.  How do connect the dividers so that I can work with division of greater than 32-bits?

What I have considered:

Create the divider from logic gates (takes too long and would crash the simulation).
Write my own divider library (I don't know Java or the Logisim source code that well and I'm still stuck with the original problem).
Work with the dividers like I did the multipliers, but chain them in the reverse order (is that even plausible?).
Write an application to generate the divider (the resulting circuit would crash the simulation).

I might be able to provide a screenshot of what I described for #3 with my multiplier if I need to clarify that point.

Edit:  Here is what I've come up with so far based on the answer I got:


texts: Another solution for all MOS are in cutoff saturation region

texts:
Here is a two stage amplfier with a beta multiplier bias(lab3),the schematic of lab3 is in the second picture.

I simulate them when VDC is 1.8v and 1.98v for tt-corner and ff corner in 25 degree centigrade and 125 degree centigrade,the mos for the two stage are all in the saturation region,but when i simulate it for ss-corner in 1.62v,all mos become to be in the cutoff region,after i replace 1.62v with 1.98v,the mos become to saturation region,so i guess the reason that cause mos in the cutoff region is the insufficient VDC.

So the solution of insufficient VDC,i can add the VDC that higher than 1.98,but i if i can't not change the VDC(1.62v),what else can i do to let all mos in the saturation region? or if you think the problem is not insufficient VDC,then what is that?how do i improve this?


texts: Is there a best practice for resistor placement?

texts: Resistors are color-coded by digit, multiplier, then tolerance, but the book I'm reading (comes with the Arduino starter kit) shows its breadboard diagrams with all the resistor tolerance bands leftmost, which seems backwards to me. I understand that resistors are not polarity sensitive, so they can go either way, but I was wonder if there was some sort of best practice / convention people use (read order vs reverse-read order).


texts: Using touchscreen cellphone lcd module for custom projects

texts:
I intend to use the capacitive touch based lcd modules of cellphones in custom embedded projects,
I will be using this display with low cost stm32 boards.

Has anybody experimented with this approach ? Any ideas, links to datasheets ?

PS : I am specifically looking for touch integrated lcd modules, there is a hack available for nokia non touch modules already.


texts: Is using water to douse a reacting lithium battery safe?

texts:
I've been reading on safety protocols on Li batteries and I seem to remember that Lithium itself is extremely reactive to water.

However, FAA regulations recommend using water to douse the device to keep it cool.

Is the FAA's recommendation incorrect or is there a particular threshold where water causes more problems?


texts:
The following information appears on the nameplate / description of an existing thermal overload relay (for motor protection) I need to replace with a modern unit of same functionality:

IEC 292-1 660V 3 PH AUX Ith 10A 500V ~ max

600V a.c. max Aux. H.D.

Can someone please explain to me in simple terms what each of these terms mean?


texts:
Say you have an N-bit ADC with reference voltage of +/- 0.5V, it provides you 2's complement formatted binary values. You perform an M-point FFT upon the samples and extract the spectrum results. All of the bins are completely 0 except for one (I know this is unrealistic, but just for the sake of math).

What are the correct steps/functions to convert the complex value of that bin back into the amplitude, in volts, of the original sinusoid as sampled by the ADC. This assumes that it was known that a pure sinewave of constant frequency and amplitude was input into the ADC.


texts: What is the purpose of feed wire and return wire in electric railway?

texts:
Looking at the following image:

Image source: The Railway Technical Website

On the left of the mast there are two cables, feed wire and return wire.

Are they acting like a ground cable which usually is made by the rail working as a ground conductor?

They are not always present in the railway electrification system, which is why I am not sure about their role.


texts:
I want to create a sound amplifier with the LM386 and I need a potentiometer. I don't have a clue what I'm doing (:P) but I've printed out the datasheet (for the LM386) and had a look at it.

So I need a potentiometer, with a knob since I'm going to create a casing for it all :)

Also, I'm planning in stereo, so that's 2x LM386 but I don't want two volume controls. How can I hook that up?


texts: Why does the Intel Atom processor need so much thermal dissipation compared to similar ARM processors

texts:
When looking at cases designed around the Intel NUC Atom-based board it seems they put a lot of effort into thermal dissipation (i.e. the entire case is basically a big heatsink). Of course, these cases are fanless and the logic goes that since there is no fan you need to get rid of heat by some other means - hence the huge heatsink.

However, my smartphone contains a very comparable processor (Qualcomm Snapdragon) and my phone contains neither a fan nor that huge heatsink. The TDP for the Intel Atom is advertised as 5W whereas it seems the Snapdragon is closer to 2.5W .

My questions are:

Is the Snapdragon's thermal design just so vastly superior to that of the Intel Atom processor or is there some benefit to the Intel Atom that I'm missing?
Also, assuming that the 5W/2.5W numbers are accurate, does that justify the huge difference between cooling solutions?
Are there any other solutions (for running a linux-based appliance) that I should look at that have solid industrial support but neither require a huge heatsink nor a fan?


texts: Detecting surrounding electronics or electrical devices

texts:
I'm working on a project which requires using EM antennas or sensors array to identify and locate surrounding electrical devices such as cellphone, laptop, ipod, remote...

I'm not a EMF guy. I don't know which frequency band I should be using. Is there any commercial sensors available?


texts:
Are there any tricks I can use to connect a QFP (or similar) package component to a stripboard (veroboard), without the hassle of setting up a personal PCB fabrication kit to make a breakout board?

I've seen TQFP-to-DIP adapters on places like Farnell, but they tend to be extortionate - some are over £80.


texts: Full bridge inverter failing after given input voltage

texts:
For my master thesis, I am designing a wireless power transfer using magnetic resonance. For this purpose, I designed a full bridge inverter which is connected to an autotransformer whose output is rectified (this way I can gradually increase my DC input voltage).
The bridge is driven by two IR2110 drivers which are connected to a dspic30F1010 microcontroller. The microcontroller generates four PWM signals of constant 50% duty cycle. (edit: with a dead time of 50 ns, so not exactly 50% duty cycle).
The system works fine and I was able to transmit about 700 W during 30 minutes without any problems. Yet, when I increase my input voltage to a certain value (a bit less than 300 V), one leg of my bridge fails.
The right leg of the bridge works fine and keeps a nice 50% duty cycle, but the other leg shows the following features:

Figure 1: Vds of the TOP MOSFET of the failing leg

Figure 2: Vds of the BOTTOM MOSFET of the failing leg
The first picture shows Vds of the top MOSFET and the second one shows Vds of the bottom MOSFET. One can see that the top MOSFET gets turned off every 4 PWM cycles.
On the second picture, one can see that the current keeps flowing via the bottom MOSFET when the top one fails (I think it flows through the body diode, because Vgs remains low during that moment).
The following picture shows a picture of Vgs of the failing MOSFET (the top one):

Figure 3: Vgs of the failing MOSFET (TOP MOSFET of the failing leg)
First, one can see that it is really spiky and not stable. I'm not sure whether this kind of behaviour is normal with a bootstrap system or not. Then, one can see that during the glitch, Vgs almost remains zero all the time.
It also seems that the measurement itself impacts the phenomenon, as it happens every 4 cycles when measuring Vds and is much less regular when measuring Vgs (it seems to be every 5 cycles on the picture, but it is not always the case though).
I also checked the control signals coming from my microcontroller. These stay 4 nice PWM signals as expected.
The following pictures may help you to better understand my layout. The first one shows the PCB itself, in case it might be linked to the layout:

Figure 4: PCB of the inverter
Then the following two are diagrams of the circuit and the components that I used for the design.
The 100 ohm - 100 pF is used to filter out high frequency glitches at the output of the microcontroller and the 4.7 kohm resistor is a pull-down resistor to avoid short-circuiting the bridge at start-up.
The MOSFETs are STW28N60M2, the gate diode is V2P6X and the bootstrap diode is GB01SLT06.
[edit: I changed the following picture to remove the ambiguity on the capacitor value]

Figure 5: Microcontroller circuit

Figure 6: H-bridge & drivers circuit
This behaviour is something I never met before and I really can't find any explanation. It is even more strange to me because it occurs only in one leg and only after a given voltage value.
I tried changing the bootstrap capacitor value (lower & higher), I tried changing the gate resistor value, I tried to replace the IR2110 and the MOSFETs, nothing solved the problem.
Did anyone ever meet a similar kind of behavior, or does anyone have a clue on how to solve this?


texts: Why input voltage only appears over R1 and not R2?

texts:
Why does the input voltage v_in only appear over R_1, hence making i_1 = v_in / R_1?

I understand that a positive voltage on the inverting input results in a large negative output. Some of the output is redirected through R_2 back making v_i = 0 (ideally). Since the input current is also equal to 0 (due to ideally infinite input impedance), in my eyes, the voltage from v_in should appear both over R_1 and R_2, and perhaps even over R_L as well?


texts: What is the flowing current through an inductor when the switching gets delayed?

texts:
Consider the following circuit in which the switching takes place instantaneously at \$t=0\$.

The current flowing through the inductor right before switching is \$ \tfrac{E}{R_1} \$.  As the current must be continuous then it must be the same right after switching. It is not hard to derive that $$ i_L(t)= \frac{E}{R_1}  \exp \left( -\frac{R_2}{L}t \right) $$ .

Question

I wonder if there is an amount of time delay in switching, what is the current through the inductor? Does it become zero? Where does the stored energy in the inductor go?


texts:
Can somebody please help me answer these three questions?:

Two identified here:

When we multiply the immediate operand by 4, do we multiply the binary or the decimal by 2^2? Is the addition sign for concatenation?

What is the maximum offset from $s?:

Thank you in advance!


texts: Drawbacks of using large resistors in voltage divider?

texts:
Two part question! I'm building an audio dummy load featuring an 8Ω, 1%, non-inductive 300W beast of a resistor. This is connected to the speaker terminals of an amplifier under test. In addition, I'd like to scope across the resistor (using a female BNC connector to attach a scope) and have a switch which toggles a 10:1 voltage divider, to compensate for higher voltages that my scope may not be able to handle (much like the 10X setting on an oscilloscope probe). My circuit looks something like this:

I realise using small value resistors for R1 and R2 would mean less current going through the load, so high values are preferable so as to not interfere with the measurements. What, if any, are the pros and cons of using smaller or higher value resistors here? Why not go for much higher values - say, 360kΩ and 40kΩ - for even greater measurement precision?
How careful do I need to be about the power ratings of R1 and R2? Am I correct in assuming that with the values I currently have, that the ratio of current going through the parallel branches is so tiny that even puny 1/4W resistors would barely be taxed?


texts: Voltage regulator with op amp(negative feedback) and MOSFET

texts: The schematic above is a very good voltage regulator, excepting the high power dissipation for Q1 (also I'd use an NPN instead of a PNP). Can I replace Q1 and Q2 with a high current n-mosfet and expect the same behavior? A mosfet has lower power dissipation than a bjt.


texts: Can a short circuit in the output of a transformer be dangerous?

texts: Assume that I have a 220 to 12 volts transformer with a nominal output current of 3 A (marked  "12 V 3 A"). Now what does happen if I connect the two output wires to each other or to a load with very low impedance? Does the current exceed 3 A by a large margin? I don't think so. But is the secondary coil designed to withstand such currents? If the temperature gets too high, the insulation of the coil wires would be damaged, which is obviously dangerous.


texts: Why does sparking occur while unplugging a 40V DC, 6A load from a source?

texts:
To start with, the problem was two-fold (sparking at plug-in as well as at unplug).

The plug-in problem was solved by introducing a delay in MOSFET 'turn-on.'
Would there be a way to solve the unplug problem too?


texts: Are cheap Chinese peltier modules efficient?

texts:
I'm developing a product that cools beverages and trying to decide what peltier modules to choose.

I've noticed that some companies like Laird Technologies, CUI inc and TE technology offer expensive coolers, while there are many generic offerings form china that come in at a fraction of the cost such as the TEC1-127XX series devices.

I'm just wondering if anyone has experience in comparing the value from the expensive manufacturers and the cheap generic ones. Have the Chinese mastered thermoelectric coolers and saturated the market with competitive prices or are there significant performance gains to be had from the expensive manufacturers?


texts: Flash memory: Does the entire page need to be erased before writing just a few bytes?

texts:
An easy question, I hope! I'm not finding any definitive answers...

I'm writing drivers for a SST25VF064C flash memory chip.  It communicates via SPI.

Like all flash memory (that I know of), it needs to be erased (all bits = 1) before it can be written (bits = 0).  For this chip, the smallest area that can be erased is 4kB.

Its memory is divided into 256-byte pages.  With one instruction, I can write anywhere from one byte to 256 bytes into a specified page.  I don't have to start on a page boundary: the first location to be programmed can be anywhere within a page.

The general rule is to make sure that the page is erased before writing into it.  But, can I write into a previously-written page, if I avoid the already-written areas?  For example, say that I store data into bytes 0-127.  Can I later write another 128 bytes into the same page, if I start at byte 128?


texts: diode selection for large current reverse bias, small current forward bias

texts: I'm designing a circuit where I want to pass a small test current from one leg, but block a large "firing" current (rocketry) coming from another leg in reverse bias. I have a 5vdc indicator line (with about 1-2 vdc and <.5 amp once it would get to the diode) I want to pass through a forward biased diode to indicate the fuse is still viable without burning the fuse, but need that same diode needs to block 12 vdc at as much as 30 amps in reverse bias for a short duration (maybe as long as 5 second until the igniter lets go and opens the circuit and the "firing" voltage is turned off manually). How do I select the proper diode? What am I looking for on the diode spec sheet to be sensitive enough to allow the low current forward bias and strong enough to block the large current reverse bias. I know that is what diodes do, but how to select the right one escapes me.


texts: Do Active RFID tags require special readers?

texts: I am researching using RFID for a project. I've read a lot about active RFID tags, such as this one. The sites that explain active RFID generally don't say much about the readers. Is a reader for an active RFID tag any different from a Passive RFID reader? Also, do the readers need to be set for the correct frequency? As in, do I need a 433 MHz reader to read a 433 MHz tag?


texts: PWM duty cycle meaning.. how does it affect current through motor

texts: I have a big misunderstanding.. when we say the pwm is 10%  the motor should be off for a longer time.. But the motor driver draws most current at 10% pwm .. I am not able to understand this concept..


texts:
I've got a pressure sensor and a flow sensor. Both have a 5V span, but have a (different) null offset i.e. at zero pressure (gauge) or zero flow they read ~2V and ~1V respectively.

I am using an ADS1256 ADC and PiPyADC (from git) so can only read up to 5V. How can I remove these offsets?

Git code has a function:

|  cal_self_offset(self)
|      Perform an input zero calibration using chip-internal
|      reference switches.
|
|      Sets the ADS1255/ADS1256 OFC register.

but I'm not sure that's what I need, I definitely can't make it do what I want anyway!

Currently, my only thought is to step the voltage down over a 2/3 potential divider to get into range, though I'm bound to lose some accuracy this way. I'm hoping I can somehow remove the offsets from both sensors.

I appreciate any help/guidance,

Thanks.


texts: Obtaining the water temperature from a heatpump using a microcontroller

texts:
There is a heatpump, which uses the following controller. How should one interface the heatpump, so the current water temperature (which is normally displayed only on a 4 seven segmen display, built in the controller) could be obtained and passed to a remote service.

I had two options in mind:

Use a Raspberry pi zero and a camera to perform some ocr on the built in display.
Use an ESP8266 or an Uno to interface either one of the 3 analog probes (which probably holds the temperature) or add an aditional ntc probe from the microcontroller.

How should one go about doing this? Thanks.


texts:
In an ideal Wilkinson power divider(because in practical there will always be resistive loss), the scattering parameters, or S matrix is given as:

From the condition that checks if network is loss-less or not which is:
Say s-parameters matrix is S(nxn). Transpose of S is X and conjugate of S is Y then X.Y=I (Identity Matrix) if network is lossless.
It turns out that the power divider is lossy as X.Y is not equal to I. Then how does the input power split equally at outputs? It means Pi=Po1+Po2(where Pi is input power, Po1 and Po2 are output powers at any 2 output ports; Po=Po1+Po2). Thus, net power loss=(Po-Pi)=0.
Does it not violate the fact that network is lossy. Or is it that Scattering parameters deal with the overall network meaning a lossy network can have a lossless path in it? If the latter is true then it makes sense to me and I can safely conclude that "A lossless network means all paths are lossless and a lossy means at least one path is lossy"[Path here meaning a road from any input to any output].
As stated in Wilkinson Power Divider, an image of which I am attaching if link goes down:

In its ideal form there would not be any resistive loss, so then would the s-parameter matrix differ from the one that I have attached above to reflect the lossless attribute?


texts: Any free software to compute boolean expression?

texts:
I found a few but they cannot evaluate long expressions. For long expressions they give me boolean values for each individual sub expressions (which is usually grouped by parentheses).

((A v B) + (~A v ~B)) v ((C v D) + (~C v ~D)) v ((E v F) + (~E v ~F)) v ((G v H) + (~G v ~H)) v ((I v J) + (~I v ~J)) v ((K v L) + (~K v ~L)) v ((M v N) + (~M v ~N)) v ((P v Q) + (~P v ~Q))

This is the kind of expression I need to evaluate. It will give me 2^16 ~ 65k rows.

I used this website, but doesn't seem giving me the final column.

Oh. I don't want to compile the program myself...
Thank you very much!


texts: Measuring internal resistance of a battery while it's being charged

texts:
I was startled to hear that there are devices out there that can measure the internal resistance of batteries, in circuit, while the batteries are being (trickle-)charged.

For example, Hioki markets industrial IR meters for UPS batteries. The lowest range is 3 mΩ with a precision of 1 µΩ (!), and they claim you can measure the battery while it's online. I'm puzzled here - isn't the charging current going to interfere with your readings?

I can imagine that if you compare battery voltages with some small and large loads applied (e.g., 1A and 10A), you can estimate IR, but you won't get µΩ precision. But at least, at 10A, the trickle-charging current is probably insignificant and doesn't interfere a lot.

However, all manufacturers seem to use an AC testing method at 1 kHz (Hioki uses 150mA @1kHz at the lowest range). I'm not exactly sure what that means. Wikipedia suggests that these are simply ESR meters, but reading on how an ESR meter works, it can't be possible, since it starts with the assumption that the DUT is completely discharged.

So, my question is: what this AC testing method is, exactly, and how does it isolate the charging current out of the equation?


texts:
I am revisiting Microcontrollers and Microprocessor concepts.

Yes. I know this question has been asked many times like here and here. I have also visited many sites regarding this concept but still I find it difficult to grasp.

But still I am unable to get the concept in my head.

Can someone provide me some image/visual representation or an example(and an analogy) to help me understand the concept of Memory Mapped IO and IO mapped IO.

Why is this necessary concept? Is this related to microprocessors or microcontrollers?
Do we really use it somewhere. Please provide an example in simple terms


texts: Signal in and out of flip according to IEEE symbols

texts:
I have the following IEEE symbol for a SR flip-flop

I have to work out the waveforms W and X given A and B. Here are A, B and the associated solution for W and X (as given by the book):

From my understanding of IEEE symbols the following rules apply:

If S1 is asserted then I should make W = 1 and then X will get a value according to the truth table of a SR flip flop.
If R2 is asserted then I should make X = 0 and W will get a value according to the truth table of a SR flip flop
If both S1 and R2 are asserted then I should make W = 1 and X = 0
If neither S1 nor R2 are asserted then I should just use the truth table of SR flip flop to determine W and X.

However I'm having some issues understanding the solution as at the beginning both S1 and R2 are asserted yet both W and X seem to be 1.

Where am I going wrong with my assumptions?


texts: What is a gel battery rated to temperature wise?

texts: I have a battery (in this case a car battery, but there's other types of batteries also made of gel), and was wondering what they were rated to so the charge is still there for when it's used?


texts: Crimp and Solder connectors for flexible electronic

texts:
I am desperately looking for crimped connectors compatible with flexible PCB and devices such as the one depicted in the following figure :

This is a pressure sensor based on a piezoelectric polymer. The connectors are crimped-on. It seems very easy to use and very practical for prototyping. Thank you for your help !


texts:
I have a Blue Line Innovations PowerCost Monitor. It sends packets to a display unit over a 433.92 MHz RF link. There is code (Power Monitor, incomplete) to detect these packets with a RF Link 4800bps Receiver and an Arduino.

I'm definitely getting something from the transmitter, but the packets don't seem to make sense. How might one go about systematically decoding data from a device like this?

(Update/Aside 2014-07: A github user has completely decoded the protocol, and forked the rtl_433 package for SDR dongles to read it: radredgreen/rtl_433.)

(Update/Aside 2014-08: Another github user has implemented this on Arduino: CapnBry/Powermon433)


texts:
I want to have this "debug" header with 10 pins (I could probably get away with 9) and I am wondering if the DTR pin is ok to be filtered by a capacitor for ICSP.

This is how I am sourcing these pins:

Note the capacitor in magenta. Will that affect the RST line for ICSP?

Why? Why not?


texts:
In TI's LMH6518 datasheet, it shows a JFET LNA implementation:

What's the purpose of C5, R17 and R49?


texts: Can we use 555 timer in automotive electronic circuit?

texts:
Can we use 555 timer IC in autmotive electronics design?
If not then please suggest an IC in order to create dealy at laod side.


texts: Using a transistor to control a pull-down switch

texts:
simulate this circuit – Schematic created using CircuitLab

I have a Runcam 2 video camera.  It uses a temporary switch to turn on/off and start/stop recording.  I would like to control these functions with an arduino.  Once side of the switch is 3V the other is ground.  Pushing the switch pulls the 3V to ground.  I've soldered two wires to the switch and can operate the camera by shorting the two wires.  I would like to use an NPN transistor with the base controlled by an arduino pin or other suitable method to operate the camera.  I've searched the archives and the closest I found was using a transistor to pull a pin low.  It did not help.  I am limited in my electronics knowledge and would appreciate any help.


texts: How can I measure the charge current into a small LiPo battery?

texts:
I have a SparkFun USB LiPoly charger that by (default) is set at 500mA.
If I try and measure the charge current with my DIY multimeters, the charging LED goes out and the meter reports zero current?

I guess this is because of the multimeter's internal series Vsense resistor confusing the onboard MCP73831 controller chip?

If this assumption is correct, can anyone suggest a DIY method method of measuring small Lithium battery charge currents?


texts:
I am trying to stimulate a JK Flip Flop in Logic.ly
But, when the input is 0 in the circuit shown below, there is an error, which I cannot pinpoint. How do I fix this?
This is the initial circuit:

This is the error for input 0:


texts:
Good evening!

I want to create an active load system where I can vary the PWM signal from the microcontroller to the control input of the MOSFET which is attached to a fixed resistive load.

I want to change the effective load value by changing the PWM. How can this be done? Is it wise choice to do something like this?

Purpose : I made a DC-DC converter of output wattage of 4W and voltage 3.3V, I want to dynamically change the load so see my DC-DC converter's performance.


texts: How to adjust the offset of a full-wave precision rectifier?

texts:
I've made a full-wave precision rectifier with TL072, for a vu-meter, and the first 3 leds are ON without signal, because I have +15mV offset at rectifier output and the levels for leds are: led1=7mV, led2=10mV, led3=14mV, led4=20mV...

I want to make this rectifier with TL071 so I can adjust the offset. But which opamp should I adjust to null the offset of the whole rectifier ? Or should I adjust both ?


texts: How slowly can you clock an AT25DF641A SPI Flash?

texts:
I am have started to try to use a SPI Flash.  To better understand how it works, I decided to try to bit bang it with the GPIO on a Raspberry Pi.  Everything seems correct, but I do not seem to have any output from the SPI Flash.  The clock signal I am sending it is approximately 1 hertz.  As I troubleshoot, I thought I should ask the question:
Is there a limit to how slowly you can interface with an SPI flash?
I am currently using the AT25DF641A-SH-T (1265-1180-1-ND on Digi-Key).


texts:
I have this Power Supply EA-PSI 9200-15T.
My input voltage to a board is 28.8V. No load current is drawn from the power supply.

With reference to the above diagram, if I connect the board to the power supply and turn the power supply ON directly, I get this waveform:

The rise time of the power supply from 0V to 28.8V is around 10ms here.

But now, if I connect a toggle switch between the power supply and the board, and I keep the switch in OFF position first. Now, I turn ON the power supply and then I turn ON the toggle switch as shown above, I get this waveform:

Ignoring the ringing, the rise time of the power supply from 0V to 28.8V is 20us.
My questions:

Why does the rise time vary when I connect and turn ON the power supply directly and when I connect and turn ON using a toggle switch?

Why is there ringing in the supply when I connect it through a toggle switch?

Can someone please help with these questions.


texts: Can I run 125kHz RF circuit on a breadboard?

texts: I was wondering if making a low frequency RF circuit on a breadboard is viable.


texts:
So I've been trying to understand how an RC lowpass filter works, and I think I got it, but I just need some clarification.

My understanding: So an RC Lowpass filter in a nutshell is just a voltage divider made to filter out higher frequency signals. The cutoff frequency is dependent on the R and C values of the filter.

The equation for the impedance of a capacitor is 1/jwC. So with low frequency signals (i.e. 20 Hz), the impedance of the capacitor will be high. Now looking at our voltage divider, since we have a large impedance connected to ground, Vout should be close to Vin.

Now let say we have a high frequency signal (i.e. 1GHz). Here, the impedance of the capacitor will be low. And because of that, Vout will instead be a small value, close to 0V.

Can anyone clarify if my thought process is right?


texts: Meaning of motor constants for three-phase PMSM

texts:
When looking at three-phase permanent magnet synchronous (brushless) motors, \$K_T\$ and \$K_V\$ numbers are often specified. Also, controllers for these motors typically specify maximum currents. However, I'm confused what these numbers are measuring. I can think of many "obvious" ways to measure voltage and current in a three-phase system like this:

peak-to-peak for a single phase
\$abs(\text{peak})\$ for a single phase (probably not for voltage)
RMS for a single phase
RMS for all three phases
peak-to-peak line-to-line
RMS line-to-line

It seems pretty obvious that the voltages specified on motor controllers are peak-to-peak line-to-line because that's what the input voltage corresponds, but the other three numbers (controller current, motor voltage, and motor current) don't have any similar constraints that are obvious to me.

The measurements could also be something different from those possibilities, and possibly not the same between current and voltage. What is the convention?

Also, the numeric values for \$K_T\$ change depending on the current waveform used to drive the motor. Converting between them is straightforwards, but what waveform are the specified values measured with? Does it depend on the flux linkage waveform of the specific motor or not?

If a specific example helps, consider the Turnigy AquaStar T20 3T. I have measured that particular motor's flux linkage (hooked it up to a scope and spun it with a drill), and it's very nearly proportional to \$18.1 sin(\theta) - 2.65 sin(5 \theta)\$ (that is, a sin wave with a pretty significant fifth harmonic). Does that mean the manufacturer-specified \$K_V\$ is for driving it with a matching current waveform proportional to \$18.1 sin(\theta) + 2.65 sin(5 \theta)\$ to get no torque ripple, or just plain sinusoidal current with some torque ripple, or just plain sinusoidal voltage with some (different) torque ripple, or something else?

I'm pretty sure this all applies to any synchronous motor (with any number of phases) too, but I'm excluding other kinds of synchronous motors from my question, and sticking with exactly three phases, to keep it more manageable.

I've found references for how all the math works, but I'm just having trouble deciphering what people actually mean when they say "this motor has
a \$K_V\$ of 170 RPM/V". This answer guesses \$K_V\$ is RMS line-to-line, but 15% off seems like a lot and suspiciously close to \$1 - \frac{\sqrt(3)}{2}\$ which would make it peak line-to-line like that question says Wikipedia says. This other answer seems to completely ignore which waveform is being used to drive the sinusoidal vs trapezoidal motors, which seems like it affects the proportionality constants it's discussing.


texts: Could an electrically charged person damage an ESD sensitive component, that is isolated from ground, by touching it?

texts:
Forgive if it is a silly question, but I couldn't find any answers to this online. I find it hard to understand some ESD related issues.
I believe that, typically, Electrostatic Discharges occur when something electrically charged touches or get sufficiently close to another thing that is grounded (I understand that it doesn't necessarily have to be grounded. I'm talking about common ESD related problems in practice). If this "other thing" is an ESD sensitive component, the electric current that passes through it may damage it.

Assume there is an ESD sensitive component, with no electric charge, in an antistatic bag (isolated from ground?). An electrically charged person opens the bag and touches the component with her bare hands. I presume that, since the component is not connected to
ground, no current could pass through it, only to it (assuming some electric charge would flow from the person to the component, until they are at the same potential).

Could this current easily damage a component? Or the electric charge necessary for it to be damaged is too high to be a concern?

Maybe my question is somewhat similar to this one, except it asks about a bird killed by a powerline instead of a component damaged by an electric charged person. The answers mention that a very high voltage would be necessary to kill the bird:
Can a bird, previously at earth potential, get electrocuted by landing on a powerline at high-enough voltage due to the initial “equalization charge”?


texts:
When the voltage on node n-mosfet is a Logic 1, the complementary Logic 0 is applied to node active-low n-mosfet, allowing both transistors to conduct and pass the signal at IN to OUT. When the voltage on node active-low n-mosfet is a Logic 0, the complementary Logic 1 is applied to node n-mosfet, turning both transistors off and forcing a high-impedance condition on both the IN and OUT nodes, but that not the case here, the output behaves independent of what happens at the gates. I expect to have zero voltage at the out put when the voltage at the p-mosfet is high.
Am i doing something wrong?


texts: How do you choose whether to use a TVS, clamp the signal, or both?

texts:
When you are trying to protect a single-ended signal, how do you choose whether to use a TVS, clamp the signal to the rails, or clamp the signal and put a TVS on the rail?

Using a TVS can help prevent backdrive (feeding voltage into the rails of one circuit through the positive clamp), but chances are that a digital IC will have internal clamps anyways, so this might not really help. I also guess that a TVS might take less PCB real estate.

Using a clamp seems like it would be more effective at limiting the peak clamping voltage than a TVS. Also, I would imagine that with ESD, the current pumped into the rail wouldn't cause too much of a voltage change.

How do you choose whether to clamp or use a TVS?

[EDIT]
One of the answers motivated me to do some more research. I did some simple SPICE simulations, and it seems that the idea is to use steering diodes (clamps) on signal lines that can't handle capacitance, and to steer the transient/ESD into a location that is more able to deal with the energy (e.g., a voltage rail). A voltage rail has enough capacitance to lessen the voltage rise, and a TVS on the rail prevents the rise even moreso.

Of course, there are many more considerations such as bidirectional, ground level differences, speed, etc. but for my low speed circuit this should be enough.


texts:
I have some Brushless DC Motors with drivers and I need some help finding the pinout of the drivers.
Please take a moment to view the pictures here, clicking on a picture will show its higher-resolution version in the current tab.
Driver Top:

Driver Back:

Motor:

(source: herringthorpe.com)
I have so far got the motors running in 1 direction by shorting pins 1,2 and 3,4 it also runs with shorting pins 1,4 or providing 5V to pin 4.
I have been testing by providing 12V to pins 5 and 7. I assume that I should be able to control the movement precisely / reverse / break as the motor is a BLDC servo.
Any help is very much appreciated, I can provide any readings using my multimeter if that will help. I am a bit of a novice when it comes to electronics!


texts: How to prevent floating input for this system?

texts:
I have a simple system where a motor speed is controlled by a voltage signal via a circuit. Below represents the system where A is the voltage signal device; B is the circuit and M is the motor. The details of the inner circuitry is not important for my question.

All I can say for now is that the voltage input is connected to the circuit via a BNC cable which directly couples to an opAmp of the Circuit B.

When the device A is off or zero volt output, the motor M stops running which is very good. But when I plug off the device or the BNC cable, I think the input to the opAmp starts "floating" and the motor starts jerking.

My question is:

Is there a technique, tool or a way to prevent this floating when the BNC is unplugged?

Edit:

Input part of the complex circuit. DAC represents the input voltage:


texts: How to supply power from vehicle to a low power device?

texts:
I am a programmer with only basic understanding of electronics/electricity.

I am trying to install this device into my vehicle. The device accepts a wide DC power input (10V to 30V), but has a maximum power supply rating of 12W (Edit: had typed 1W).

I am assuming that means the input current should be somehow controlled, external to the device.

What do I need to do this? A current limiting circuit? A fuse for extreme situations?

A current limiting circuit as described in wikipedia will dissipate power? Are there off-the-shelf components for this?

Is a separate spike guard required?


texts: "input" signal corresponding feedback network

texts:
The pictures below are enhanced output impedance current mirror and a general negative feedback model.
The current mirror has a negative feedback loop. However, I can't determine where is the input that is corresponding to the "input" signal in the general feedback model.

What is the input signal of the feedback network here?
The output signal is Iout, and the input is not clear to me.

PS: I would like to talk more about my purpose of this post now.
I want to make it clear what feedback configuration the circuit is (voltage-voltage, current-voltage, voltage-current or current-current) and then I can apply the feedback theorem to calculate output impedance of this circuit.

Rout = gm1*ro1*ro2*(1+A) where A is the loop gain and the output impedance of the network without feedback is gm1*ro1*ro2.


texts: Choosing the right Antenna for radio chip

texts:
I'm using Atmel Atmega256rfr2 which is a 8bit microcontroller with a radio transceiver for IEEE 802.15.4 communication. They come in 2 evaluation boards #1 and #2. Both are almost same with the main difference being that #1 has an on-board debugger and #2 does not. Both the boards use on-chip ceramic antenna by default but also have the capability to use an external antenna. #1 has SMA female on board and #2 has MS 147 connector.

I want to use the external antenna and I'm not sure how to choose one. I have the following questions.

Can I use any SMA male antenna for the 2.4Ghz range like this?
For MS 147 on #2 should I use MS147 - SMA converter and then use SMA antenna? I cant seem to find a mating MS 147 male antenna.
How do I select the gain and height? How much of a difference does it make to overall performance?
One of the reasons I want to use external antenna is that the on-chip ceramic antenna does not fare very well outdoor. My hypothesis is that external antennas can provide better range and reliability.
Can I use monopole or a dipole antenna?


texts: The use of cyclic prefix in OFDM to mitigate Intercarrier Interference

texts:
I understand that a guard interval (GI) is required to eliminate ISI in OFDM-based systems. In this context, an empty GI could be used.

But, why an empty GI does not remove Intercarrier Interference (ICI)?


texts:
I have a PCB design with a long row of 1206 power resistors. Although only a few of them will be active at a time, they can dissipate up to 1 watt each, so I would like to heat sink them. If they get too hot they may overheat the components they're connected to, or just fail sooner.
Picture for reference:

For electrical and space reasons I can't attach either pad of the resistors to a large plane. I've placed thermal pads under the resistors, but they cannot be electrically connected to it, only thermally.
My original plan was to "pour" thermal epoxy over the resistors after reflow assembly, this would spread the heat out from the active resistors, and also couple it into the nearby thermal pads. I tested that, and it works, but the issue is that the epoxy is much thicker than I anticipated (like frosting). This makes smearing it onto the board without covering adjacent LEDs quite difficult and time consuming, not really suitable for production.
I also considered placing a dab of thermal compound (not epoxy) under each resistor before reflow, but the issue with that is that the thermal compound must be able to withstand reflow temperatures. I found one (boron nitride), but it's a very watery consistency and it dries to a crust in seconds, so that also proved to be impractical.
Does anyone know of an elegant way to heatsink these resistors?


texts: Best resistor value in series with LDR sensors

texts:
I am designing sensors array for the Line following Robot, based on LDRs Resistors and transmitter LEDs, the value of LDRs Resistors in series is changing with the position of the array on the black Line, so I can measure the Deviation angle value from the voltage divider through R1 to control the tow Motors.

The value of LDR Resistors changing from 92 Kohm to 110 kohm, I put a resistor R1 in series with the LDRs, the ADC pin (A0) in arduino uno is connected to the voltage divider through R1.

Question: How I can choose the value of R1 to get the best sensitivity on A0 pin?
I tried 10k ohm but I get  a small changes just  [4.5,4.58] volt and that's not working I need more sensitivity. How can I choose R1 to get the best sensitivity on A0 pin?

simulate this circuit – Schematic created using CircuitLab


texts: Does doping always increase the conductivity of a semiconductor?

texts:
The conductivity of a semiconductor is given as (if extrinsic):

\$\sigma = qnu_e  + qpu_h\$

where \$\sigma\$ is the conductivity, \$u_e\$ and \$u_h\$ are the electron and hole mobilities.

But does this equation always hold true? Is there any circumstances when conductivity decreases if a dopant is added (whether p-type of n-type?). What happens if a dopant is added which has a large binding energy to the lattice. Surely that'll decrease the conductivity!?

I am only a second year Engineering so I have not gone into that much detail into solid state physics/electronics.


texts: Powering a calculator's liquid crystal display (LCD)

texts:
Hello, so I'm trying to use a calculator's LCD for a project of mine and I want to put a current through it. However, the LCD is powered by the "sheet of plastic" shown in the picture, circled in red. Does anyone know what that "sheet of plastic" is and how does it work? In addition, how can I put a current through it with just two wires?

Thanks!


texts: Oscilloscope and power supply measurement

texts:
If I use a switch load and an digital oscilloscope to test my linear power supply response, then which type of trigger should I use, if I want to display on CH1 the PSU output and on CH2 the output of the switch load? Should I use DC trigger on CH2 (switch load) and AC coupling on CH1 to show the response of the PSU under test?
This is the schematic of the switch load: https://ibb.co/dMtCBLh