texts: What is the difference between ISO/IEC 14443 and ISO 7816 smart cards

texts:
I am trying to build my own smart card decoder and I found that the smart card with the most popularity in terms of security and utility is the Mifare Desfire EV1 which is pretty much industrial grade. The second card I found was the Parallax IS23SC4442 which is more of a home project card. The Mifare card has an ISO/IEC 14443 A and the Parallax has ISO 7816. I was wondering on what were the differences in between the 2 standards.

I dont know if this is any clear nor if I am in the right place but thank you for your time.


texts: How can I extend the ammeter wires to my shunt?

texts:
Is it possible for me to locate my ammeter and shunt a few meters away from each other (more than intended by original wiring)?

The extra wiring obviously has a resistance and provokes a false reading, which I have tested and found to be true.

Is there a way I can locate my ammeter away from my shunt?

It's a 12V DC circuit running from around 0 Amps to 10 Amps, Ammeter is rated to 50 Amps and the shunt is 75mv.
"False readings" are the ammeter showing anything from 0 Amps to 12 Amps when I know it is 1.7 Amps depending on the extension of wires I try'd.
I'm hopeful about trying to eliminate the noise and will report back when I've tested.


texts:
I notice that in Ben Eaters project for the 74 series logic chip computer, which my son and I are building, sometimes he uses current limiting resistors on LED's on the pins of some chips, and on others, he madly throws caution to the wind, and slaps that LED right in there with no apparent resistor.

I assume this means some kind of inner knowledge of each chip, and that the outputs of each chip are current limited with an internal resistor.

How can I determine which chips are safe to put the LEDs in without a resistor, and which ones require the current limiting resistor.


texts: Conditional Port connectivity during module /wrapper instantiation

texts:
I have a wrapper, with multiple ports (mainly used to parameterize/scale a particular module) and in this wrapper i parameterize the module instantiation with help of generate for-loop.
i.e.

generate
for (genvar a=0; a< NUM1; a++)
begin : module_label
module module_inst(
.x1(x1[a]),
.x2(x2[a]),
.x3(x3[a]),
.y(y[a])
  );
end
endgenerate

Now i want to control my port connectivity inside this module instantiation based on some condition. Can i use a if loop within this instantiation? Something like :

generate
for (genvar a=0; a< NUM1; a++)
begin : module_label
module module_inst(
.x1(x1[a]),
if ( NUM2 = 5) begin
.x2(x2[a]),
.x3(x3[a]),
end
.y(y[a])
);
end
endgenerate


texts:
I have a question regarding SR effect.

Let's say that we have some simple amplifier with op-amp with the following parameters:

\$G=+10 \ V/V, \ f_c=1MHz, \ SR =1V/\mu s, \ V_{supply}=\pm 15V\$

The source signal is a square wave:

\$V_{in}=5V, \ \overline{V_{in}}=0V, \ f=10kHz\$

And I want to ask about checking if SR effect will occur - it is easy to notice that the output voltage will be limited by \$|V_{outMAX}|\approx 13.5V\$.

So should I check if

(1) \$2\pi\cdot\frac{f_c}{G}\cdot V_{outMAX}> SR\$

or

(2) \$2\pi\cdot\frac{f_c}{G}\cdot V_{out}> SR\$
where \$V_{out}=V_{in}\cdot G\$

All I ask for is a one word answer. Thanks in advance.

Edit: I assume that amplifier will produce something like this (red color) and this is what I am asking about


texts: Controlling speed of 7 DC motors from Arduino 101 using PWM outside of the audible range

texts:
I am researching a way to generate PWM for 7 independent DC motor drivers, each connected to a 12 V DC motor. The drivers take in a PWM signal, a direction signal and a 12 V DC supply and use this to control the speed of the motors.

Currently, the design uses the Adafruit 16-Channel 12-bit PWM/Servo Driver board, based on the PCA9685 IC to generate multiple PWM signals from only one Arduino 101 (via the I2C bus). The issue with this IC and boards based on this IC is that the maximum possible PWM frequency that it can generate (1600 Hz) produces an audible hum from the motors when active.

It would be better to have a PWM generating circuit that can generate PWM at ~25 kHz, where it would be outside the audible frequency range. The circuit must be controlled by an Arduino, as this is the platform that existing software has been developed for.

Are there any pre-made circuit boards or integrated circuits that would allow this functionality?


texts: USB-C as power source and negotiation with USB 2.0 and 3.0

texts:
I have a PCB that currently features a Micro-USB used only for data transfer, and a separate 5V power supply input jack for powering up the device. The device's maximum drawn current is 600mA. To remove the need for the input jack and to use only one cable, I would like to follow the steps featured in this post in order to have my USB 2.0 device handle both data transfer and power (5V, 600mA) using a USB-C receptacle.
From what I understand, the steps include soldering the two data pins from the Micro-USB to the receptacle pins, soldering the 5.1k pull down resistors on the CC pins, and soldering the 5V/GND pins from the input jack to the VBUS/GND pins of the receptacle to power up my device. For now I do not care if the modification is bulky, I only care on safety.
I then want to hook up my newly modified device to a laptop. My questions are:
If I hook it up to a USB-C port, will the power negotiation work as expected? I understand that USB 2.0 hosts limit negotiation to 500mA, thus I want to know if negotiation will work as the host can handle more (900mA) but my device runs USB 2.0 only?
Now say I use a commercially available USB-C to USB-A adaptor to connect my modified device to a classical USB-A port on my laptop. I expect that the answer does not change if the port runs on USB 3.0? And if the port only features USB 2.0, will my device basically not turn on, as negotiation will stop at 500mA?
I am new to negotiation, any help is very appreciated!


texts: What are these parallel connected lines meant for?

texts: During my walk today, I noticed these small parallel connected lines. What purpose do they serve?


texts: Why is my mosfet driver circuit clipping lower voltages?

texts:
How can I fix this? I've been trying for hours. I want to try and get 0-20V and 2.5A out of 0-5V input (V3). I pretty much chose a random n-channel mosfet that I thought was in spec, but I have a P30N06LE to use.

Click on image to open full resolution version.

Most recently modified circuit (visible in stackexchange too)


texts: ModelSim Error : " could not find interpreter "ScintillaTk" "

texts:
I have installed ModelSim 10.4 X64, when I want to open a vhd file in editor an error shown in "Transcript" window as :
" could not find interpreter "ScintillaTk" "

I searched about that and I found out that this problem occurs when ModelSim installation path have a space character !!

I have installed it in "Program Files" Folder, Now how can I solve this problem without installing it again ?

I have changed the "Path" environment variable`s value form -path- to -"path"- but the problem not solved ...


texts: What does it mean for a CPU to support a stack?

texts:
How can a CPU not support a stack? Doesn't any architecture that uses subroutines (I'm pretty sure that's all architectures) have to push the return address onto the stack so it can return to where it called the subroutine from? The stack just means a section of memory with a pointer that grows in a certain direction and acts as a stack data structure no? I just don't understand how an architecture could not support a stack.

To what extent is automatic memory storage (automatic variables vs. static variables) determined by the compiler vs. the hardware architecture?


texts: Need help understanding how to calculate tpd while static hazards are involved

texts:
I need help understanding how to calculate tpd while static hazards are involved,

Given this circuit: (the output F is constant 0)

I found out that if X and Y are initated to 0 and we change Y to 1 we get an hazard after the AND gates (0->1->0) which I know cause a delay in the circuit even though the output is constant.

I am having trouble understanding how to calculate the delay, for example what delay should I take into consideration (HL,LH) for the AND gates.

If I could get an explaintion and an example calculating the delay from Y to F it would help a lot (not graphic if possible).


texts:
simulate this circuit – Schematic created using CircuitLab

I have dc into a bunch of 555 timers to create a square wave single that goes into the gate of the n-channel mosfet. im trying to power a transformer with 60 volts dc power. the resistance on the primary coil of transformer is 4 ohms. why will this not work? i do a open circuit test on transformer. it pulls more than 2 amps with no load. need some advice. i just need this transformer to work


texts: Nonblocking simultaneous assignments to wires and registers in Verilog

texts:
I am interested to write Verilog module which simultaneously will update several outputs Something like following code, makes 3 operations at the same time (clk 10):

module mymodule (a,b,c,d,e);
input a;
input b;
output c;
output d;
output e;

wire b;
wire a;
wire c;
wire d;

reg e;

initial begin
c <=  #10  (a+b);
d <=  #10  a;
e  <= #10  b;
end

endmodule

Is that code legal?


texts: Neutron Single Event Upset (NSEU) how its effect is mitigated in electronics in space vehicles?

texts: Since in the outer space the NSEU will be more common than in the earth, how the electronics in space vehicle is tacking the issue. I feel a solution will be existing for some decades but on google I got some information about single bit error corrections only. It does not mention any prevalent techniques.


texts:
If a sampled voltage signal \$y[n]\$ is composed of its offset \$\bar y\$ plus noise \$x[n]\$; i.e. \$y[n] = \bar y + x[n]\$, are both following equations for the RMS value of the noise component \$\text{RMS}(x)\$ same?:

\begin{align}
\text{RMS}(x) &= \text{RMS}(y - \bar y)\\
\text{RMS}(x) &= \sqrt{\text{RMS}(y)^2 - \bar y^2}
\end{align}

Are both equations above correct and same?
For the equations to be correct does \$x[n]\$ have to be random in nature? What if \$x\$ has periodic component?


texts:
I am using a very sensitive transimpedance amplifier on a 3m long cable to a photodiode. Signal levels are about 70 nA - 700 nA. Bumping into the cable causes a large voltage spike on the output of the amplifier. The insulating material is FEP.

Could this be the piezoelectric effect in the cable insulaton?

Edit: Here's a typical voltage spike. This happens when I bend, shake or tap the cable.


texts:
I have a design using an LPC1788 together with a SDRAM module from ISSI (IS42S32800D). This is a 32bit interface.

I have routed this design out and had a prototype made with a PCB manufacturer that does 6 layer prototypes. The prototype PCB works fine. I then thought I would get the PCB manufactured in a small volume batch (100) from my usual PCB supplier. I gave them the stack up information that my prototype used to ensure there would be no issues.

However! I have massive problems with the production board. At first I was unable to raise any response from the SDRAM what-so ever with the same code I used in my prototype board. The previous board was working at 120Mhz so I was sure something was wrong with this new board. I then found a post where people suggested using Repeater Mode on the SDRAM data lines (I had not used this previously) and this raised a response from the SDRAM, however it is not stable. I can write to 16 or so addresses, but then with subsequent reads the data returned (at every address) is the data which I wrote last (probably due to Repeater Mode). When I disable repeater mode, the data returned is 0xFFFFFFF. I am now trying to connect at 48Mhz, the lowest configuration I have timings for.

I am using the same termination resistors (on the Data lines) of 22Ohms on both boards, data lines are an average of 3cm long. Clock line is 2.4cm long. Address lines are average of 3.8cm long.

Is this too out of spec, should I delay the clock longer if it substantially shorter? I am really stuck here, as I have changed nothing about the design I was hoping for a seamless manufacture run for these boards.

Maximum Data Line Length: 59mm (Although this includes the branch to the NAND Flash)
Minimum Data Line Length (Ctrl to Res): 18mm
Maximum Address Line Length: 44mm
Minimum Address Line Length: 24mm
CLK: 24.5mm
CKE: 25mm
CAS: 28mm
RAS: 28.7mm

Here is the PCB stack configuration for the original (working) prototype:

Here is the PCB stack configuration for the production (non-working) PCBs

Here is the routing for the SDRAM:


texts: How to calculate Impedance of Edge Coupled Stripline Coplanar Waveguide

texts:
I have some questions about adding copper pour on signal layers with high-speed differential pairs traces.
I am routing my HDMI diff pair traces on an inner layer. because we have been having some issues passing radiated emission tests, a colleague suggested for the next board revision to add on all signal layers copper fill to essentially create a waveguide around the diff pair as illustrated below.

How can I calculate the impedance of stripline waveguide? I haven't been able to find any calculators online that have that configuration
Is this even a good idea?


texts: Understanding the exact meaning of dB/decade in a Bode plot

texts:
To make the question clear I will ask this with an example.

Let's say we have a LP filter with a -3dB attenuation at cutoff frequency of 1kHz.
And lets say we are given the steepness of the filter as 100 dB/decade.

Does that mean the filter will attenuate 100 dB/decade right after -3dB point?

If so, the following possibilities for Bode plot points confuses me when I try to use dB/decade definition:

-103 dB at 10 kHz? or

-100 dB at 10 kHz? or

-100 dB at 11 kHz? or

-103 dB at 11 kHz? or

Which one of the above is exactly correct according to the definition dB/decade?
What confuses me is should we take decade as multiplication or addition to the cut off frequency? And should we go down from -3dB or zero for the attenuation?


texts: This lab requires us to extend the memory and I/O ports on our µPad using our EBI backpack. What I'm confused about is how the fully address decoded SRAM will differ from the partially addressed i/o ports. And will the i/o ports have the same address range? Please help with parts a and b!


texts: What is the use of analog circuits today?

texts:
While studying analog circuits and conducting experiments with op-amps, I couldn't help wondering why would I need an analog circuit to add/multiply/integrate electrical signals. In modern times, computers are quite cheap, and it seems a lot easier letting a computer calculate anything you want (it's fast, versatile, reliable...)

So, why use op amps and analog circuits?


texts:
I need to build an Active twin- notch filter that will filter out 60Hz. I am following the schematic bellow:

To test the schematic, I am simulating it on Falstad Circuit Simulator, but the 60Hz is not being filtered out.

Here is the link to the simulation.

Could any tell me where I am going wrong ?

Thanks,

Liam


texts: Side of headphone doesn't work unless I hold the volume button or pause/play button on headphone.

texts: I have a pair of Samsung headphones with a mic, volume control, and pause/play button. I have used these headphones for over a year. They worked perfectly. Then one day, the right side decided to quit on me. The right side of the headphone is the one with the little control box. The left side plays sound perfectly fine. When I hold the volume button or pause/play button the right side turns on and I can hear out of both sides. There is no problem with the cord, just the right side.


texts:
Trying to make a simple but reliable 15-12v to 5v circuit to power the ATTINY85 from an automobile (15v-12v), wondering if I have the right components and ratings, I don't know a lot about circuit designs so I've been living through google and google images to get to this point.
I originally was going to use the LM7805 but the R-78E was recommended after much searching and states a 91% efficiency, with no heatsink required but similar size and same pinout. This will be housed inside a project box and mounted inside/behind the dash and powered when vehicle is on/running, also the ATTINY does not require a shutdown time its acting as a switching mechanism. LED is merely to show the unit is powered.

Ultimately I'm confused on if this circuit will work as planned and if the components are rated properly also what type of capacitor should be used, was planning on Alumnium Electrolytic but I'm open to anything thats through-hole soldered, or an easy to solder SMD.
Any suggestions or insight would be greatly appreciated.

Diode - 1N4001

Capacitors - P975-ND

Datasheet for the R-78E5.0-1.0 - https://www.recom-power.com/pdf/Innoline/R-78Exx-1.0.pdf


texts: (ARC WELDING) Why does voltage DROP with increasing current?

texts:
I hope I'm asking in the right place!
I worked with automated TIG (GTAW) welding equipment. I'm confused about how the welding power supply controls the current applied through the work piece. If the entire circuit was a simple static load, with a known resistance, it makes sense that voltage across the load could be controlled to keep the current constant. If I want more current, I increase the potential.
In this case, the arc voltage will drop with increasing current. This can be seen clearly on a diagram of voltage vs. amperage for a constant current welding power supply and is consistent with my own findings. If, during the middle of a weld, I command the machine to produce more current, will the machine increase the potential across the output terminals? I have a suspicion that the dynamic nature of the arc welding aspect of this comes into play. I.E. the conductive plasma region becomes larger once it reaches a steady state at a higher current?
Please let me know if my question makes any sense.
Thanks!


texts: Digital Potentiometer: wiper voltage higher than control voltage

texts:
I'm trying to use digital potentiometers, controlled by an arduino, as drop-in replacements for a number of 10k pots in a circuit in a piece of audio equipment.

I've been looking at datasheets for digital potentiometers, and all the ones I've found will not allow you to control resistance in a circuit with greater voltage than the supply voltage sent to the chip. For instance, the MCP4131 (datasheet here) states maximum voltage at P0A, P0B and P0W (pot terminal 1 2 and wiper) not exceed Vdd + .3v

I had assumed that, digital control aside, a digital potentiometer would operate like a plain one; with a maximum voltage and current that would probably be much higher than what I'd have to worry about (I'll be working with up to 12.5v). I didn't realize the control voltage would be a limiting factor for the voltage going through the potentiometer.

Are there digital potentiometers that allow control of circuits with higher voltage than the control/supply voltages?

If not, what would be the simplest solution for my application? (ie fewest components and connections), find a digital potentiometer allowing Vdd up to 12.5v, and then boost the control signal from the arduino? Something to do with a transistor added to the potentiometer side of the circuit? something that doesn't involve a digital potentiometer at all?

Thanks


texts:
I am building a simple debouncer with decrementing counter. The syntitizer is yelling that there are latches. I don't need latches. I just need flipflops. WHich part in the following code is creating latches?

Design: The block receives a value and if the value is different from the stored one, it starts to count down. As soon as the counter reaches 0, the block outputs the new value.

library IEEE;
USE ieee.std_logic_1164.ALL;
USE ieee.std_logic_unsigned.all;
USE ieee.numeric_std.ALL;

entity Debouncer is
    Generic (
          DB_DATA_WIDTH             :   integer range 1 to 8   := 8;
          DB_CLOCKS                 :   integer range 0 to 1023   := 3
    );
    Port(
        clk : in STD_LOGIC; --clock
        Sig : in STD_LOGIC_VECTOR (DB_DATA_WIDTH-1 downto 0);   --raw input signal
        Deb_Sig : out STD_LOGIC_VECTOR (DB_DATA_WIDTH-1 downto 0);
        Deb_Rdy : out STD_LOGIC;
        rst : in STD_LOGIC
    );--debounced output signal
end Debouncer;

architecture Behavioral of Debouncer is

    signal value_reg :STD_LOGIC_VECTOR (DB_DATA_WIDTH-1 downto 0);
    signal tick_counter : unsigned (9 downto 0);

begin

    process (clk, rst) is
    begin

        if (rst = '1') then

            --TO_UNSIGNED(DB_CLOCKS, tick_counter'length)
            tick_counter <= TO_UNSIGNED(DB_CLOCKS, tick_counter'length);
            value_reg <= (others=>'0');

        elsif (clk'event and clk= '1') then

            if (value_reg = Sig) then

                if (tick_counter /= 0) then
                    tick_counter <= tick_counter -1;
                end if;

            else

                value_reg <= Sig;
                tick_counter <= TO_UNSIGNED(DB_CLOCKS, tick_counter'length);

            end if;
        end if;

    end process;

    Deb_Rdy <= '1' when ( tick_counter = 0 ) else '0';--debouncing logic is assigned to the output Deb_sig
    Deb_Sig <= value_reg;

end Behavioral;

Log:

WARNING:Xst:1710 - FF/Latch <Inst_Debouncer/tick_counter_9> (without init value) has a constant value of 0 in block <led_switches>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <Inst_Debouncer/tick_counter_8> (without init value) has a constant value of 0 in block <led_switches>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <Inst_Debouncer/tick_counter_6> (without init value) has a constant value of 0 in block <led_switches>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <Inst_Debouncer/tick_counter_5> (without init value) has a constant value of 0 in block <led_switches>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <Inst_Debouncer/tick_counter_7> (without init value) has a constant value of 0 in block <led_switches>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <Inst_Debouncer/tick_counter_3> (without init value) has a constant value of 0 in block <led_switches>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <Inst_Debouncer/tick_counter_2> (without init value) has a constant value of 0 in block <led_switches>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <Inst_Debouncer/tick_counter_4> (without init value) has a constant value of 0 in block <led_switches>. This FF/Latch will be trimmed during the optimization process.


texts: Total current drop when using leds in parallel

texts: I'm making an led light for video shoot purpose. It's an array of 20, 5w led in parallel. The problem I'm encountering is, current drops when I'm connecting them in parallel. My power supply is adequate, it's a 12v 10amp power supply. When I connect a single led directly to 12v supply, the current I get comes to be .8 amps. So .8amps X 12v ~ 10w, which is higher than the led's output rating, but when I connect 20 of them in parallel, the current flowing through is  4.12 amps. So 4.12amps X 12v ~ 50w. When logically the current flowing should at least be 8.2 amps. What is happening here? Kindly help.


texts: What is the purpose of having two type of output interfaces on this ADC?

texts:
The ADS4126 comes with a Double Data Rate (DDR) LVDS output interface and a

I have following questions:

What criteria is used to decide which one of the two to use?
Can both be used to read the ADC at the fastest data rate of 250MSPS?
Which of these is more power efficient and why?


texts: Is there a way to way to calculate the draw limit on a battery, using any of Amp-Hour, C-Rating, etc... values to solve for the unknown? If so how do you do it?


texts: Inferior limit of output voltage in op-amp low-pass inverting amplifier circuit

texts:
I'm simulating the low-pass inverting amplifier circuit using LTSpice:

I put a sine of amplitude 4 as input to see the behaviour of the op-amp in the non-linear zone. I was taught that the output voltage, in non-linear zone, can't exceed the positive supply voltage and can't be smaller than the negative supply voltage:

However, when running the simulation I get that the output, i.e. the voltage on the load resistance (V(3) on the simulation), gets smaller than the negative supply voltage (0):

How can this happen?


texts: How to shut off a valve safely in the power outage

texts: In a scenario of sudden power loss, my latching valve will be still open by default. That valve operates with 5V, and needs 0.5A current with duration of 0.1s to be shut off. How to do that in a cost effective and safe way?


texts: Not gate that differentiates between 0V and GND

texts:
A not gate typically just inverts the signal, so that V would turn into GND, and GND into V. Is there a not gate using transistors that would switch GND into V, but not switch 0V into V? (preferably using common transistors like npn and pnp)

By GND I mean having it connected to the ground pin of the power supply, and by 0V I mean not having it connected to anything at all.


texts: Does combining two separate transformers double the voltage?

texts: Can I wire the outputs of two separate transformers to get twice the voltage? I have two separate, identical transformers from neon signs. Both put out 6000 volts at 30 mA. I would like to use 12000 volts for my project.


texts: modelling of solar cell: offset in short-circuit current

texts:
I am trying to simulate the IV curve of a solar cell in reverse and forward bias. I have used bishop equation that you can see in the following picture.

The mathermatical model is in good accordance with measurement. However, when I simulate it in SPICE, I have an offset in current which I think is related to the way I have added the leakage part.

Here is my SPICE code and the equivalent circuit. I will be thankful to have help for correction.

.param a=1.987261e-01
.param b=2.741757
.param Vbr=-1.865206e+01

.MODEL diode1 D(is={3.71896e-10}, n=1, xti=3)
.MODEL diode2 D(is={1.178667e-05}, n=2, xti=3)

Iphoto 0 internal 8.05
D1 internal 0 diode1
D2 internal 0 diode2
Rsh internal n1 92.3597
G1 0 n1 value={1+a*pow((1-(V(internal)/ Vbr),-1*b))}
Rs output internal 0.00252

.dc Vbias -18 1 0.01


texts: Designing a USB switch, schematic done, wanting a second opinion

texts:
I want to design a prioritized reverse USB hub, where a USB flash drive is connected by default to a device but switches to another when a connection is present.

The setup of my product uses a Raspberry Pi and a USB flash drive inside a box. On the outside of the box I have 2 USB ports, one for power and the other for data, neither of them directly connect to the Raspberry.

By default, the USB flash drive is connected to the Raspberry, but I when I connect a USB cable to the data port of the box, the Raspberry notices it and switches the USB flash drive from it to the USB data port of the box. When I remove the cable, the Raspberry switches again the USB flash drive to one of its internal USB ports.

The schematic for this is the following:

So, I read here in stack exchange that the 4 USB pins must be switched and not only the D+ and D- pins. These are switched via a FSUSB30 USB switch IC, on the top of the schematic. By default, even if USB_SEL is a high impedance, the switch connects the D+D- pins of USB_PEN_DATA (Flash drive) to the D+D- pins of USB_INT_DATA (RPi USB).

For the power side (this is where I have my doupts), I use a two MOSFET IC to switch GROUNDS. Basically, I read that two computers may have slightly different 5V between the VCC and GND of its USBs, so two USB ports of different POWERED devices should not be connected together. Ok, so I just connected the positive terminals in a "VCC_USB_COMMON" net, and I switch the ground of the USB flash drive "MAGIC_USB_GROUND" to the RPi ground "GND" or to the computer ground "PE".

The grounds of the computer and the RPi are isolated through the use of a schmitt trigger output optocoupler that drives the MOSFET that switches the computer side PE ground. On the RPi side, the ground is switched directly with RPI_GPIO_PIN_OUT_X.

Finally, for the RPi to know if a USB cable is connected to the external data port, I've put a second optocoupler that has the IR LED powered by the computer and the schmitt trigger powered by the Raspberry and its output is read by an IO pin "RPI_GPIO_PIN_IN_X".

This all seems like overenginnering, but I think it gives me perfect controll over the timings of the switching of data and power lines. Somewhere I also read that the order mattered.

Is this circuit sound? I didn't check for the typical resistor values yet, I just put something that I thought would work as a ballpark value, but I will check that in detail if this circuit can do what I want. Also, decoupling caps aren't present but they will be on the final design. Are ferrite beads REALLY necessary? I'm only going to require USB2.0 at 480Mbps so...

EDIT: Ok, if I understood correctly from Ali Chen's answer, I am overthinking things and only D+ and D- should be switched. The updated circuit is as follows:


texts: Which library for microSD cards with Arduino

texts:
I'm trying to use a microSD card with an Arduino (ATmega328). I'm using the SPI interface.

I've tried using the Arduino SD wrapper, but whenever I #include the SD.h header file the Arduino continuously resets itself. I think this is a RAM issue and it seems like this is the issue: http://code.google.com/p/sdfatlib/issues/detail?id=15

How would I go about doing this now? What library/method do I use?


texts: Why does a metal sheet block all noise, but not when wrapped around a cable?

texts: If I place a flat sheet of aluminum foil between a near-field probe and a noisy wire, the sheet completely blocks the noise. However, if that sheet is then wrapped around the wire, it seems to have no effect on the noise. Why?


texts: Why is RZ-DPSK more nonlinear tolerant than NRZ-DPSK?

texts: In fiber optics, why would RZ-DPSK be more suited for long-haul transmissions over NRZ-DPSK? Is the tolerance to non-linearity due to the power intensity or something else?


texts: has only one pin and Nets Wire has multiple names in Altium multi Sheet

texts:
I have two sheets which my ports are defined on them. I tried to use multi sheets (two copies from sheet 1 and one copy from sheet2) but I am faced with these two errors :

has only one pin(Sheet4.SchDoc, Net NetU1_29 has only one pin (Pin U1-29))
Nets Wire has multiple names(Sheet4.SchDoc  Nets Wire CLK has multiple names (Sheet Entry U_Sheet1-CLK(Passive),Sheet Entry U_Sheet2-CLK(Passive),Sheet Entry U_Sheet5-Port1(Passive)))

I followed duplicate net names wire  but these errors still available.


texts: How to properly use a relay module with JD-VCC from Arduino/Raspberry?

texts:
I got two 4-relay-modules and I am probably doing something wrong because none of them seems to work:
My first try was using a breadboard 5v power supply, connecting VCC and In1 to 5V and GND to GND. I was expecting the first relay to switch, but nothing happened. I tried with all In pins but nothing
The module seems to have some LEDs to indicate when the relay should be on, they do not light.
I also tried 3v instead of 5, and connecting to another Power supply the JD-VCC. Nothing works
I tested with the multimeter and all the pins I connected are getting power, so either I am missing something (very probable) or I both boards are broken
Another thing i noticed is that if i apply 5v and GND, then all IN seems to have around 3v
The relay model: JQC3F-5VDC-C

[EDIT]
My module is generic, and I couldn't find the official schematics.
Thank you very much @tlfong01 for pointing me to this one, that seems to be the right one:


texts: Detecting when an object with surface mount component?

texts:
We have a pcb that sits close to some hole. When something passes through ( at 2-5cm distance) we have to detect it.

To me it seems that this area is still in the 90's . When I check my options, all of them are large modules of infra red devices, or ultrasonic modules.

These works great, but I was looking for something that can sit on the pcb, small, and simply detect light/sound/etc.

Something elegant , the size of a chip.

Are there things like that ?


texts:
Why is always prefered the value of 0.1u as decoupling capacitors that they placed very close to the chips?
Why don't use larger, like 0.22u, 0.47u, 0.68u or 1u for example?


texts: This is a very simple question but something that I'm not able to wrap my head around. This Energy report states generated electricity. But what does "generated  killowatthours" mean? I know that can't mean that the US produced that much electricity every hour...but what exactly does it mean?


texts:
I want to built a LED panel with a high photon flux, and photon flux density, (the LEDs have a specific wavelength) but when I start to search wich LEDs I am going to buy, all the sellers just give me:

forward voltage;
forward current;
wattage of the LED.

Is there a way to know,(or at lest have an idea) of how much PPF will those LEDs produce ?


texts:
I would like to know what you think about this. Here's a diagram presenting the main modules of the project. Red is 9V unregulated, green is 5V regulated, black is 5V logic exchanges.

I want to turn on/off the circuit. For the moment I'm considering :

Switch between the 9V DC source and the 9V rail.
Put the µC on a separated 5V  rail and isolate the 9V input of the DC Motor driver, keep the microcontroller on standby and implement a soft switch, when pressed he will turn on a transistor and power on the 9V rail of the motor driver and the 5V rail for the other modules.

I prefer the first one as the circuit is already pretty much finished (yeah, I forgot the basic "on/off" functionality...) and the first solution don't require too much changes. One of my question is do I need to do something special to make it safe or can I just put the switch in series between 9VDC and 9V Rail ?

The second question is, do you have any other ideas, not to hard to implement ?

NOTE : I'm more looking for design patterns (not sure if you have something similar in EE) than specific implementation, that's why I've posted the simplified module diagram of the circuit.


texts: How many amps of Current is consumed in this circuit?

texts:
I have this circuit: A battery connected to a DC/DC boost converter, that is connected to a Raspberry Pi computer.

The detailed schematics of the boost converter can be seen here

The rest of it is obvious, we have 2 pieces of 1.5 V batteries, that are 3 Volts of Input Current.
The output is 5.2 V, and since the cable is short, the voltage should not drop significantly.

I have the following questions:

What is the maximum mA of current that the batteries can supply to the Raspberry?
(My understanding is that it can supply 500mA at 1.8 V, but what happens when the voltage is lower, is there some formula that I can use to calculate how much voltage is needed for X mA of current?
How many mA are drawn by the input side (from battery to boost converter) in order to produce X mA of output current for the Raspberry?
What is the 2A internal switch, and what is it's function, I don't understand what that is?


texts: Problem connecting DC motor controller with AC / DC power supply

texts:
I am trying to power two 125 W DC motors using an Arduino Uno, motor controller and power supply. Frustratingly, I have previously had everything working smoothly but everything has since stopped.
I power the motor controller from the 5V and GND on the arduino pin. Power LED comes on.
Separately, I connect the earth, line and neutral into the power supply and turn on the mains (without any connections to the V+/V- pins) and the power LED on the power supply comes on. Using a multimeter I get 24V between the V+ and V- pins.
So far so good. This makes me thinks independently both bits of kit work.
I then plug the V+ into + terminal on the motor controller and V- into - terminal on motor driver. When I then power everything on the motor driver LED is on but the power supply LED doesn't. That makes me think something is shorting out on the motor driver and the power supply is protecting itself by turning off? Does that mean the motor driver is broken and I need a new one? (I have redone the connections countless times.) My only other thought is that something is required to match the earth of the arduino (low power) circuit to the earth of the motor/power supply (high power) circuit?
If anyone could help me that would be amazing!
Motor controller:
https://www.droking.com/DC-Brush-Motor-Controller-16A-Power-Supply-Module-Dual-way-motor-drive-module-forward-reverse-PWM-Motor-Controller-H-Bridge-Control-Board-For-Arduino
Power Supply:
https://www.amazon.co.uk/Surom-Universal-Regulated-Switching-Computer/dp/B071W121H7


texts:
I want to control the current on an inductive load (electromagnet) by the means of PWM switching. I have done some research and saw a lot of different circuit configurations.

The electromagnet will act on a metal rod so changing polarity is not of interest.
A capacitor should handle the reactive currents when switching (there will be a lot of wasted power if not)
I want to control the PWM with an arduino micro-controller so logic level mosfet or gate drivers. I think I will need gate drivers anyway for high side switching
Power is relatively low maybe 12V power supply and 3A max. and PWM switching will be just above audible frequencies ~20 kHz.

My initial idea was to use only one N-channel MOSFET on the low side, plus a diode but I found more interesting circuits that are maybe more efficient.
This is the circuit I am going with:

simulate this circuit – Schematic created using CircuitLab
When MOSFETs are switched on the current flows from the capacitor to inductive load and when they are switched off the capacitor recharges. The power supply will give only active power.
I am aware that I have a high side N-channel MOSFET that needs a driver. I have seen some high-channel and low-channel drivers on the net but It is not clear for me how the bootstrap capacitor is getting charged

How does a bootstrap solution gets charged in this configuration? when both mosfets are off there is no link from V1 to charge the capacitor, it will leak charge with time. Maybe I am wrong?
Also, what is really the advantage of this Half H-bridge over a single MOSFET in the low side?
What is the best way to do a current sensing feedback to the Arduino? A shunt?


texts: Can all Wifi emitters dynamically select frequencies? Or is specific hardware support needed?

texts:
Using the linux kernel and a wifi adapter I was able to emit a signal and read it from other devices, however my software only allows to transmit over a preset channel of the 2.4GHZ frequency. Most routers change frequencies dynamically based on the amount of interference present, this is called Dynamic Frequency Selection.

Since most of the neighbouring routers use Dynamic Frequency Selection, I'm forced to implement it, however I need to know whether dfs requires any type of hardware support that might not be present in my adapter. Am I safe to rule out hardware limitation and freely attribute my issue to missing software support?


texts: I have a USB powered device with an internal Li-Ion battery that has overheated and died.  After looking for similar events online I found that charging on a 2.1A charger can damage or destroy the device.  I thought that chargers rated for 2.1A means that is maximum output.  What could cause this kind of failure?


texts: unable to charge the powerbank in this setup

texts:
The main objective is to make a perpetual powersupply (uninterrupted power supply) for a raspberry device. However, in the schematic below I have replaced the pi with a simple LED resistor since I was just prototyping the basic circuit.

Below is how it looks on the breadboard.

The micro usb terminal on the bottom is connected to the mobile charger. The terminal on the top is connected to the powerbank output. Further, the screw terminals are meant to charge the powerbank; it is connected likewise.

When there is no load on the screw terminal, it reads a voltage 4.5V. Not sure why the drop! And when under load, it drops even further, 3.6 V. This is not allowing me to charge my powerbank.

Of course, I can charge the powerbank separately, but theoretically this circuit should work, according to me. I just can't troubleshoot why this setup won't charge the powerbank.


texts: Board to Board connection for RF and high-speed digital signals

texts:
(I hope this is not regarded a "shopping or buying recommendation" question - in my opinion it is not).

In order to split a larger project into more tractable and flexible sub-blocks I create two PCBs (motherboard/daughterboard).

This is a very common setup in the digital world (PAM2-PAM4) and there are high-end connectors for high speed digital (Samtec, FMC).

However, in my project I also need to "flawlessly" connect RF signals between the boards. In summary - these connections have to be made between the boards:

ground plane, power (easily solved)
high speed digital, ~100 MHz, ~50 I/Os (easily solved with Samtec connector)
Analog clock, ~200 MHz
4x RF signals, up to 3 GHz

For 3-4 I would use SMA connectors - if it would not be a daugher board. However, I would prefer a more solid connector - ideally just one for 1-4.

I found RF board-to-board connectors but they tend to be single signals. Even if I could get an RF connector with multiple signals, physical alignment together with an FMC connector for the digital lines is painful.

So I am really looking for a board-to-board connector solution that faithfully connects 1-4.

If I can use high-speed digital connectors also for the RF signals - are there any issues or disadvantages using them compared to SMA, e.g. insertion loss, return loss/matching, isolation? Or stated differently: Why are these connector usually not used for carrying RF signals?


texts: Beginner electronics hobbyist needing my schematic looked over

texts:
I only very recently started getting into electronics as a hobby, and the little amount of theory I got in college did help, when I actually started remembering things :P

Anyway, my next project is a regulated box mod for electronic vaping, as I have been off cigs for 2 years now, and really want to make something my own(though I don't care if you want to use anything I have made if it is even worthy).

The goal was a regulated box mod with a linear and flat dc voltage control, down to 0.2 ohms are 5V.

Obviously this means I will need high rated batteries, fuses, and running them in series, but a few other challenges, like keeping the voltage control off the high current. This is what I have come up with. (The labeled test points and meters hooked up will make sense later).

Flipped around to make it easier to read:

If there is anything obviously glaring, please educate me on issues that I may see in the real world. I have ran this schematic through all the simulations I could think of and everything seems to look fine, but let me know if you see anything I did not notice, or am simply ignorant of :P

This shows the harsh voltage drop out occurring at 6 volts, and although it is a consequence of the op amp I chose, it is actually a very good thing as it'll make it obvious when I need to change batteries. I may actually use a diode to intentionally drop the voltage a volt, as I currently have about 1 extra volt of headroom in the way I like to vape anyway.

This shows how well it should handle the load depending on the resistance of the coil. Obviously 0.1 ohms is when things start going wrong.

This shows how linearly it regulates the voltage, and the point in which the op amp can no longer keep up. 6V is out of the range I would ever be vaping at anyway.

Finally, this shows the voltage leakage when the mod is left on but without the fire button pressed. Seems pretty small to me, but if I did/didn't do something that made this worse than it should be, let me know.

EDIT: Sorry about the schematic being backwards and inside out LOL. The location of the components are relative to the location when assembled to make following it easier when assembling. I did not think about it being so difficult for  the vets to 'proofread' because of that. I flipped it around so maybe it is a bit less confusing to read on the updated version above.

EDIT 2: So I believe I have finalized everything at this point. All I have added is an upper limit on the voltage, to take some stress off the off amp and fuses in case mistakes are made, as well as a cutting the voltage if the batteries are too low, to prevent accidental over-draining. If you are interested, here is the updated schematics with sweeps:

Showing the now pseudo-linear voltage voltage delivery with the sharp voltage drop when batteries are low.

The voltage curve maxes out due to a 5.6V zener reference. Turning the potentiometer so it approaches 100 bypasses the zener, didn't worry about it as I may find it useful.

No more sharp voltage drops using 0.1 ohm coils.


texts:
Right, I have a very simple circuit that I aim to use as a delay circuit, everything was going fine until I started to over think it all and now I have totally confused myself and it is slightly embarrassing.

This is my circuit:

simulate this circuit – Schematic created using CircuitLab

As you can see, nice and simple. I know the time constant of the capacitor is RC to reach 63% of the voltage, but my issue is what is the voltage that it is reaching 63% of? I initially thought the 2V supply (capped at 1V though) that I am using at R2, but then it would charge to 1V in less than RC (not what I want).

I take the time constant as \$1M\Omega \times 1 \mu F = 1\$s but would that be the time to charge to 63% of 2V (but cap out at 1V) or 63% 1V (i.e. take 5 times longer to get to 1V)?


texts: Communication between different Baud rates

texts:
I am totally new to just about all of this, first off.

I have two boards that I want to be able to communicate. Both are using half-duplex serial connection, but one is fixed at 4800bps, and the other is at 57600bps.

I've dug in, and to the best of my understanding, I'll need something with 2 UARTs to more or less convert the signal from one to the other. That is about where my understanding has hit a wall.  I'm unsure what chip would work, how to setup the chip, or if there are other, simpler options. I just need a bit of direction from someone with some experience!


texts:
I'm designing my own computer based on the Zilog Z80. It has 256KiB of static RAM with paging as well as a few megabytes of flash memory. Everything is going along pretty well until * BAM * I hit a dead end.

The problem that I am having is designing a video controller. I was thinking about some kind of a terminal or display. A 24x80 or 25x80 terminal would be wonderful. However, even a 640x480 VGA display would take up enormous amounts of memory.

640 * 480 = 307.2 Kbits

That is even more than the amount of memory addressable by the Z80 at one time!

Also, if I want color, say, one bit per color, I would need 3 bits per pixel.

307.2 Kbits * 3 = 921.6 Kbits

In addition, wouldn't it need to be dual-ported to allow access from Z80 and the monitor?

Because this is extremely difficult to implement in software and hardware, would it be a good decision to use a character ROM? It would be very difficult for me to get fuse-link PROMs or UV EEPROMS. What should I do? Can I put a character ROM in flash memory? How would I implement it in the controller? How do I tell the character ROM which character to spit out? Should I even use VGA? Would component video (NTSC or PAL) be easier than VGA?

If a good system can be designed, perhaps we can even use it for microcontrollers! Give me all you got, I need as many ideas as possible.


texts:
In my current project, I need to communicate between a microcontroller and some sensors over I2C. One of them is a temperature sensor, it needs to be placed at approximatively 2 meters far from the microcontroller. I cannot choose another protocol (the sensor is on a module with given connector/pins/protocol).

Do you think it is possible to communicate in this configuration? What information should I look up to ensure it can or can't be possible? Do you have some advice?

It is my first time communicating with IC outside the PCB.


texts: Proper Method of Powering Nokia 5110 LCD

texts:
I am considering getting some Nokia 5110 displays for use with my Arduino Nano board but I am in a pickle because I can't tell the correct way to wire it.

Some people say to power it with 3.3V and only 3.3V and to use 3.3V logic or else. But other people claim running it on 5V just fine. The data sheet for the Philips IC that controls it says that it can have a maximum input voltage of 7V so it looks like I would be fine. However, some people report abnormal behavior and short life span of the screen. If I used the circuit below except with Vcc and LED going to 3.3V, would that be OK?

The nano runs on 5V logic so I would keep the 10k's. If that is correct, is it saying I need the equivelent of a 40k on the RST pin of the LCD? Why? Any ideas much appreciated!


texts: How to find a saturation current for BJT from datasheet?

texts:
Saturation Current is one of parameters in Ebers Moll Model, but I can't find it in datasheets. I explore SC1627 and BC856 datasheets. How to find it?

As opposed to How do I saturate an NPN transistor? I want to know influence of saturation current for value of collector current at real conditions in compliance with Ebers Moll model


texts: Is show waveform always referring to current?

texts:
In EveryCircuit, it allows you to "show waveform" for a particular component. For example:

Does waveform always refer to the current that is going through that component or are there ever alternate waveform-types?


texts: connecting Open drain and Push pull outputs to drive the same pin

texts:
I am designing a circuit in which has a voltage supervisor (MCP121-33)with active low output nRST connected to RESET input of the microcontroller which is straightforward. Also, there is a another requirement in which the RESET input of the microcontroller has to be driven by one of the GPIOs of MCP2221 (USB to I2C/UART).

The GPIOs of MCP2221 are all push pull and not open drain.

How to connect MCP2221 GPIO and nRST from the regulator such that we can RESET the microcontroller using either of the sources.?

Any buffers with open drain is required on the push pull GPIO? please clarify.

Thanks in advance....

Datasheets: MCP2221 (USB to I2C/UART) AND Voltage monitor


texts: mini Tesla PN2222A transistor getting hot

texts:
I am helping my son make a mini-Tesla for his science fair project and came across a problem I can't figure out.  I am following this diagram (pretty much, but without the LED):

Also, I am not sure of the exact number of windings - around 300 of 27 AWG wire.  I have experimented with 2 to 6 primary coil windings and can make this work with 3 windings of the primary coil. My problem is that I have burned up two transistors already - not right away, the circuit works and I can turn a bulb on but the transistor is getting VERY hot.  Why?  Do I need

fewer or more primary windings?
a different type of transistor?
a heatsink?
a different value resistor or an additional resistor or capacitor (don't ask, but I have seen other versions of this mini Tesla)
just need to buy more tansistors and hope for the best?

Thanks in advance.

LTR


texts: Does a bias resistor determine the forward voltage drop across an LED?

texts:
I hadn't really given this much though before but when I look at the forward voltage drop of a LED, it gives a graph such as

Can I simply set the resistor to a value produce a current and get the corresponding forward voltage drop or is there an associated resistor within the LED for which I need to account?


texts: lowering AC ripple in a non switch mode power supply?

texts: In a non-switching, regulated power supply, with a full bridge rectifier, what can we do to minimize AC ripple within reason? Is going to a larger cap the general way that this is addressed? What are additional design considerations to deal with ripple if we can effectively negate it?


texts: How to make an h bridge using only comparators

texts:
I discovered I could easily make an H-bridge (or something that effectively behaved as one) by cross coupling the inputs of two op amps. So for op amps 1 and 2, 1+ is connected to 2- and 1- is connected to 2+. This worked great, but since I am not really amplifying a signal so much as comparing them, this seemed like a better job for comparators. However, when I tried the same thing with comparators, it did not work. After studying comparators a bit, I realized the problem had to do with the fact that a comparator's output cannot not reverse polarity like an op amp, but can only act as a switch. I get the feeling I would need four comparators for this to work, but I could use some help. Since I am using them in an odd way, the recourses online did hot help much.

My comparator is LM2903P. My op amp is TL082.

Here is the circuit I am using:

It is being used as a multivibrator. I would like to be able to get higher frequencies, so being able to use comparators would be useful.


texts:
For an RC (model) car, I'm trying to make reversing lights, brake lights and indicators. When the car is going forwards, the brake lights need to go off, and when it reverses then both the brake lights and the indicators need to turn off. I'm using the ESC (Electronic Speed Control) output and an IC(Integrated Circuit) to determine which lights should be on when the esc output is one way or another. This is the (relevant part of the) circuit diagram:

At the moment, the circuit works but at low input voltage to the IC (i.e. at low revs) the brake and indicators don't turn off completely, but flash. At max. revs the both do turn off though. I've adjusted the IC input (am using an ADC port to be able to detect the low voltages) to a very low input, so this is not the problem.

My question: what is the best way to smooth out the DC signal coming from the ESC, so I can make the inputs to the IC more responsive? I've looked at rectifier circuits but they all seem to apply for AC. There must be a similar kind of idea for DC circuits surely.

Thanks in advance


texts: Debugging simulation error in Xlinx for VHDL

texts:
I used Xilinx to simulated Logic And Gate, and it worked fine. I followed same procedure to simulate Half-Subtractor, but got stuck in between.

When I checked Xilinx window for two codes I found two differences (please see red boxes in the following figures).

Above program worked fine without any problem.

Can anyone check my figure and find out where I went wrong?


texts: Second-order Band-Pass Filter Gain Confusion

texts:
If I derive the equation for a bandpass filter (in this case, critically damped) from the RLC transfer function, I get a different result than I would get otherwise by combining the transfer functions of a highpass and a lowpass filter.

$$H(s)=\frac{\frac{R}{L}s}{s^2+\frac{R}{L}s+\frac{1}{LC}}=\frac{2 \alpha s}{s^2+2 \alpha s+\omega_0^2}=\frac{2 \omega_c s}{s^2+2 \omega_c s+\omega_c^2}$$

Versus:

$$H(s)=\left(\frac{s}{s+\omega_c}\right)\left(\frac{\omega_c}{s+\omega_c}\right)=\frac{\omega_c s}{(s+\omega_c)^2}=\frac{\omega_c s}{s^2+2 \omega_c s+\omega_c^2}$$

As you can see, the two formulae differ by a factor of two.  Which one is correct/why do they not agree?


texts:
Is it possible to boot a pc with a second BIOS on a spi chip which is connected to the one soldered to the motherboard?
Of course the right pins would have to be connected but I'm unsure about CS and Hold.
Some mainboards from gigabyte already have a second bios but I don't know how this works under the hood, some others have a special header where you can attach a programmer or SPI chip like:

http://pcengines.ch/spi1a.htm
or
https://www.thelabeshop.com/files/5/3106/Universal_SPI_Pin_Header.pdf

So this already goes in the right direction.

The ideal case for me would be to just connect a SOIC8 clip to the onboard chip and the pins on the other end from the clip to the ones from the backup chip. The onboard BIOS should just be ignored during boot. However, I don't know if this would work or if other parts are required.
Is this somehow dependent on the software on the chip? If I delete all data from the onboard chip would the second chip automatically be selected or is there more low level stuff going on on the chips which prevents this?


texts:
I had an idea (which probably isn't original) that electronics could harness power from a signal or a wave (like a radio wave) or a ray or something like that instead of having to charge or buy batteries. How possible is this and what could be used to do this?

This would be along the lines of solar powered electronics, but what about other sources? Something that works like a solar panel that collects the rays or waves and converts it into electricity. Is there anything like this available or being worked on? Even something that used to be worked on but was forgotten.


texts:
I did exactly as that picture showed, and I guess how it works is that it charges the AA batteries and then takes energy from them to charge something through the USB hole? Right? (I'm new to electronics), but when I plug in something (my phone charger) it doesn't give a message saying it's charging.. However, when I connect a USB powered fan with LEDs, it starts spinning..

What is the problem?


texts:
This is more a 'presentation' and 'usablity' question.

Is it possible to get an array type socket, prewired and capable of accepting several small (T1 or T1-3/4) led?

Ideally, I am looking to create an array of several led where any led can be replaced easily (by pulling out old and pushing in new), ideally with a matching dome diffuser, and ideally wired in paralell.

Is such a thing available and if not, what are my best options?

The end result should ideally be a bit like the inners of a torch with several led, where each led is individually and easily replaceable by your 2yr old son, or 90 yr old great great grandmother.


texts: determine the Laplace domain of this RL circuit

texts: I am currently learning control system design. I have a lot of confusion about the initial conditions of the inductor in the circuit. Could someone please correctly solve this by getting the differential equations and then take the Laplace transform.


texts: Approximation of internal switching schematic in a LED driver chip

texts:
HT1632C datasheet

I'm trying to figure out what would be an approximated schematic for the LED driver's COMMON pins when in the N-MOS open drain output mode.

The name suggests that there are N-channel MOSFET transistors involved. This is also confirmed by the fact that in the N-MOS mode the ON mode for a COMMON is with the pin pulled to ground.

On the diagram above the OFF state is VCC (3.3V in my case) and the the ON state is ground.

What is not clear to me is what happens in the OFF state for the COM pins on the diagram above. From probing with an oscilloscope I can tell that the COM pins in the OFF state do not have bult-in pull-ups and are in some way connected to ground because with no pull-ups attached externally the volate on the COM pins is floating near ground chaning only very insignificantly between the ON and OFF states.

When I add a 100K pullup to 5.1V (this is intentionally higher than the 3.3V VCC of the chip itself in my case) I get 3.8V for the OFF state. My first guess was that it has a 300K pull-down to ground inside the chip when in the OFF state but when I connect a 1K pull-up I get 4.1V for the OFF state which means this is not just a simple pull-down inside the chip.

What could be an approximate schematic for this swtiching inside the chip that would explain these volatage with these external pull-up resistors?


texts: Opentherm protocol - pcb design question

texts:
I'm challenging creation of PCB that would allow me to talk to my boiler using specifics of so called OpenTherm protocol.

Till now I have learned the following:

  Polarity is interchangeable on 2 wires
  Data is signalled in changes in voltage and current
  Boiler sends data as change in current where '1' is 17..23mA and '0' is 5..9ma
  Room unit (which I want to make here ) is sending data as changes in voltage where '1' is 15..18 V and '0' is max 7V

My problem here is that I would like to understand ( hence asking for explanation ) about PCB design that I have found and would like to use here

Q1 : Could someone verify if this design would work as expected to properly communicate with my room unit ?

Q2 : Any explanation for someone stepping into world of analog components would be appreciated.

Thanks
Raf


texts: Why is my non-inverting band-pass filter not working properly?

texts:
I need to design a band-pass filter with the cutoff frequencies of f1=16384 Hz and f2=32768 Hz.

I calculated the values of the components and it seems right, but when I run the simulation f1=9kHz and f2=58kHz.

What can I do to obtain the cutoff frequencies of f1=16384 Hz and f2=32768 Hz?


texts: I am building a power supply for an ozone generator. It is a simple design, I will add feedback loops later. But for now I am trying to produce 4KV output(40W). But there is a problem with current. Micro-Cap simulations show that current is too much. Goes around 4 - 10 amps. If I put a multiplier to seconder it goes even higher like 20amps. What is the reason. How can I fix it?


texts: Do I use a relay, MOSFET, or just a switch? (5VDC 15A load)

texts:
I have a 5VDC 15A power supply that will be powering both an Arduino and 288 Addressable LEDs. How do I switch the circuit on and off? First I looked at relays. The only relays that I could find that support a 15A load are ones that use High Voltages around 250V. I think they had a minimum recommended load voltage of 12V.
I also looked at mosfets, but I found that many would burn up if I put 15A of current through them.
I have also considered just using a switch, as everything is at the same voltage. In that case, I would need to make sure the switch I use can handle the 15 A of current. Hopefully a switch like that wouldn't be too bulky.
Basically, My load voltage is too low to use a relay, but I'm afraid the current is too high to use a mosfet or normal switch. How should I turn this thing on and off?


texts: Automatic-switching reverse (back up) caravan camera

texts:
I'm wanting to try some electronics trickery after many, many years away from it. Unfortunately many of the rules evade me but I feel like I could pick it up quickly, again.

My goal for my first project is this: I have a vehicle equipped with a reverse (back up) camera that shows on the LCD screen when I put the car in reverse. When I hitch up the caravan to the car, which also has a reverse camera, I'd like the input to the LCD screen to change to the caravan camera.

I know the pinout for the camera on the LCD harness, so I can easily snip that and divert the camera into a circuit, and then the output of that circuit back into the LCD screen. Both cameras are normal composite cameras (signal and earth wires). So what I want to do is somehow see that the caravan camera is now sending signal and then switch the 2-pole feed going into the LCD screen from the onboard vehicle camera to the caravan camera. Maybe I can just switch the signal wire since I could just leave the earth wires connected full-time?

In my head I'm pretty sure I can do this with transistors and a relay but I'm not 100%. What's the simplest way of approaching this? i.e. without microcontrollers? Hopefully once I get down to it, it will all come flooding back to me!

Thanks

Brett.


texts:
I have an accessory battery for powering devices when the vehicle is off. The Secondary battery is connected through a battery isolator. Each battery is separately connected to chassis ground. When the vehicle is turned on the primary(LA,12v,140AH) battery shows 14v across the terminals, the secondary(AGM,12v,80AH) 12.8. Upon throwing the switch, both batteries show 12.8 across the terminals. A meter in my 12v accessory shows 14v out from the alternator.

Measurements are taken across each battery as you would to check the voltage of a battery. All grounds are separate physical connections to the chassis. A Fluke 289 is used to measure voltage. The accessory is the voltage from the cigarette lighter. This runs through a splitter which has a meter on it, measuring its input. No extra load is placed on either battery during the testing. The cable from the primary battery to the alternator is a 2 ft run of 2/0AWG, the cable from the primary to secondary is 10 ft of 2AWG wire.

Shouldn't both batteries still show 14v across the terminals? In either case why is this drop occuring? Additionally, if I do not see the 14v across the batteries this means that niether battery is charging correct.


texts: MOSFET or bipolar to drive a solenoid valve?

texts:
I have to drive a 12V solenoid valve. In the datasheet it's written: Power: 8 W. So the current drawn by the solenoid is 0.666 A.

Usually, to drive small relay (about 10 or 20 mA) I use a bipolar transistor but with this kind of current is it possible? Or do I have to use a MOSFET because my bipolar will be burning?


texts:
I have a rubidium frequency standard which has an 1pps output pin. It provides 1 uS length pulses of +5V. I tried to hook up this pin to LED through a 100 Ohm resistor and also tried to use a transistor as an amplifier to avoid pin overload, but I cannot see LED blinking. My guesses are - my brain/eyes are not fast enough and LED actually lights up, or, second guess - during that 1 uS frames not enough energy goes through p-n junction.

My question is - how can I drive LED with such pulses?


texts: Inferred latch warning on out port in VHDL

texts:
Disclaimer: this is beginner question.

I can't figure out why o_address gives an inferred latch warning in post-synthesis and how to fix it.
When I try to assign it it gives another warning: design project has port o_address driven by constant 0.
I have also tried to assign it in every single case but it still doesn't fix it.

Any tip is much appreciated.

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_unsigned.all;

entity project is
    Port ( i_clk : in STD_LOGIC;
           i_start : in STD_LOGIC;
           i_rst : in STD_LOGIC;
           o_address : out STD_LOGIC_VECTOR (15 downto 0);
end project;

architecture Behavioral of project is
    type state_type is( RST, S0 );  --other states
    signal CURRENT_STATE, NEXT_STATE : state_type;

    begin
    process(i_clk, i_rst, i_start)
    begin

    if(i_clk'event and i_clk = '1') then
        if(i_rst = '1') then
            CURRENT_STATE <= RST;
        else
            CURRENT_STATE <= NEXT_STATE;
        end if;
    end if;

case CURRENT_STATE is
    when RST =>
        o_address <= "0000000000000000";

        if(i_start = '1') then
            NEXT_STATE <= S0;
        else
            NEXT_STATE <= RST;
        end if;

    --other cases

    when others =>

end case;
end process;
end Behavioral;


texts:
I have a main PCB and 3 button boards. You can see the connection at bottom from my ugly paint sketch. Each button board has 2 push buttons and a power LED. One of the buttons is switching GND and other one is switching 24V. Power and button signals goes together with a CAT6 cable.

The main PCB includes a PIC microcontroller.
Main PCB input circuit for buttons here:

TS for GND switching buttons, ST for 24V switching buttons. To the right side is a ULN2003 connected to the microcontroller with pull-ups.

I tested the circuit with a short cable and it worked. When I tried with longer cables, it fails sometimes.
The main PCB reads a button pressed without the button being pressed.
I also tried to add pull-down resistors on the input side of the main PCB of 24V switching buttons. It is increased accuracy but sometimes still fails.
I can change the main PCB very little (like adding pull-up, pull-down resistors) but not much. I am free to makr changes on buttons.
It may be a basic problem but I could not figure it out. I am open to any solution for proper working buttons.
Edit: I know there is little information but I can not find the cause of the problem.


texts: Convert 2.9V to 5V to operate relay using limited resources

texts:
I brought a relay module which works when 5V are given to its input pin to switch on high voltage.

But my raspberry pi GPIO pins give out only 2.9V (measured from multimeter, it was supposed to give 3.3V).

I have only below mentioned things available in my locality :-
BC-557 (PNP), BC-548b (NPN), LM-317t (Voltage Regulator), some resistors.

How do I operate relay using above mentioned electronics components? Please keep the circuit simple BUT safe for my raspberry pi.


texts:
Please excuse me if this is not the right place to ask this question.
I have been looking for a specific ribbon cable (motherboard to LCD board) for my Huawei Matebook X Pro for more than a year now and I still can't find it.
Now, Im trying to see if someone with good soldering skills and have proper tools would be able to just replace the FPC connector and so I'm looking for this FPC connector below, you can see on the screenshot seem to have 3 broken PINS

I've spent countless hours searching online for this but Im still not sure if its even possible for me to know which one to get. I check on digikey and the result is just overwhelming.
All I know is it has 40 pins, but Im not sure if all the FPC which looks like this and has 40 pins would fit on this. I've seen FPC connector for Smartphones on AliExpress with 40 pins on them which looks like this but I have no idea if they are the same and can be use on my case.
BTW, here is the actual image of the flex connector that I can't find online

I'd appreciate if someone can advise how to get that correct FPC connector.
Cheers.


texts: Is it going to be possible to write code in C++ for PIC microcontrollers in the future?

texts: Is it ever gonna be possible to use C++ for coding PICs? Is there any hardware limitations that prevents us to use C++? How much the size of generated .hex file and running time of the program increase when we use C++ instead of C? Is it practically possible to use C++ for current PICs? Is there any future plans or ongoing development on this?


texts: Evaluate logical expression with a couple NAND gates

texts:
I'm trying to implement a clever way to do error correction of 4 bits with the classic 3 parity bit correction and such.

I'm constrained by the number of logic gates I can use, but I'm trying to implement the following logic expression

OUT = AB(~C) + A(~B)C + (~A)BC + ABC

I have access to A, B, C, ~A, ~B, ~C, (A + B), (A + B + C), ~(AB), ~(BC) from other parts of the circuit. I also have exactly one inverters and 4 NAND gates (2 inputs per gate) to spare. Is it possible to implement the above logic function?

(I am using ~ as logical NOT)

I've messed around with De Morgan and Karnaugh maps but they don't help much when it comes to gate-specific constraints like these.

UPDATE: I've freed up 1 extra inverter and 1 extra NAND, for a total of 2 inverters and 5 NANDs.


texts:
I haven't done a bad job for this amplifier circuit since I got it to work with 470K for RV and 10K for RG but what I'd like to do is create a better quality sound output. Maybe my 1/2 watt 8-ohm speaker is to blame but who knows.

So anyway, I tried a stiffer ratio and used 10K for RV and 10K for RG and I get no sound output. I notice I don't get any sound output for any values of RG until I make RV substantially high (like 470K)

Given the components I chose in this circuit and given each audio device is 8-ohms, how do I calculate the optimal values for RG and RV? I'm trying to avoid the need of tuning multiple potentiometers in the future as I will make multiple sound units later on.

For my tests, AMP_PWR is VCC and VCC is 5V. later on I may make AMP_PWR a higher voltage.


texts:
I want to build a Lead acid battery charger.
for that I want to use a small IC engine coupled to a dynamo and the dynamo I got is rated at 12V, 35A and I want to charge 12V 7.5 Ah Lead Acid battery.
so here are the doubts which arose.

Can I connect the dynamo output directly to the battery(with blocking diode of course) and expect it to charge since the battery's full charge voltage is around 14 V and dynamo is rated for 12V.
And why is there such rating on dynamo, will it not produce more than 12V if it goes faster??
Will I need some sort of current control while charging the battery or the battery will draw required current.?
I just want a brute method which just works, I don't want to go for full charging algorithm stuff.


texts: ULN2003 current flow through non enabled pins

texts:
Edit: solution found

There was some amount of flux residue remaining on the board from when I soldered it. My meter didn't beep in continuity mode, but it did register some resistance, which I didn't notice at the time of soldering because I was only listening for a beep and not watching the meter.

The boards were throughly cleaned with a brush and 100% isopropyl, then checked for continuity between the pins which showed no continuity.

I'm testing a new ULN2003 module I bought with some arduino code. I have it setup as follows to a led for testing purposes.

I have noticed that when pin 1 is connected to a high signal (5v), pin 16 allows for current flow, and the attached LED is turned on, this is expected.

However, while pin 1 is high, and pin 2 is low (GND) the collector on pin 15 is allowing some small amount of current flow, enough to dimly light the attached LED.

Is this the correct behavior of the ULN2003 chip, or am I doing something incorrectly?

Its difficult to see in this photo, but the LED connected to pin 15 is dimly lit, if I switch pin 1 to gnd and pin 2 to 5v, led 2 is fully lit, and led 1 is dimly lit.


texts: Common mode inductors with high pulsed current

texts:
I have an application where I am producing fairly high short duration pulses into a load, 50A and 100us. I am looking for a common mode inductor to help reduce my EMC emissions.

Because these pulses are short and infrequent then from an rms heating point of view this inductor can probably be rated at 5A or less.

Being common mode then the fluxes generated by the outgoing and returning currents will tend to cancel which is the point of a common mode inductor. There must be a point however, where due to slight differences in the coupling between the two windings and the core the choke can saturate and lose inductance.

Does anybody have any experience of this and to what extent you can push the pulsed current beyond the continuous rms rating without loss of inductance.

Are certain types of design better than others in this regard, I would expect toroidal cores to be better than most but I have no evidence to support this. Finally is there any published data available?


texts: Is it possible to get a high efficiency buck-boost converter by switching between the two?

texts:
Many buck-boost converters work by boosting to an intermediate voltage, then bucking to the desired voltage. What if instead, it had a separate buck and boost section in parallel, and switched between the two based on input voltage and desired output voltage.

For example, if the converter is set to 15 volts, and it's being supplied with 12 volts, the buck side would be disabled and the boost side would be boosting the 12 volts to 15 volts. Likewise, if you set it for 5 volts, the boost side would be disabled, and the buck side would drop the voltage to 5 volts.

Could this lead to high efficiency buck-boost converters?


texts: nRF51822 bricked after faulty boot loader

texts:
I have a custom board (a chinese game pad) which uses a chip named n51802, which according to nordic is a “custom” nrf51822 - completely compatible with it though.

I “accidentally” (fiddling around) flashed an image that came with the nRF Toolbox for iOS and i think i corrupted the bootloader.

The device does not respond (it has two LEDs, which stay off, but i don’t know exactly to which pins are they connected to) and no bluetooth is discovered (check with various devices - iOS, android, linux).

I found out that i can force DFU mode by pulling P0.20 low, though it is very difficult (almost impossible) to solder a wire on the chip itself, and it’s not used at all at the pcb.

The only possible solution is to use JTAG flashing, but i’m not sure if it will work and i currently don’t have the required tools to carry out the operation (will test it soon though).

Is there any other way i can save the day and flash it OTA?


texts:
If I obtain the iron core from a microwave oven transformer and strip off all the windings then wind 2 coils, each being 20 turns with 12 gauge wire, will I effectively have made an isolation transformer?

Can I use it with household power without tripping the circuit breaker?

What do I need to do to make sure to not trip the circuit breaker?


texts: Problem driving MOSFET with ACPL 337J optocoupler

texts:
I want to drive a mosfet. I am using an ACPL 337J optocoupler to drive it. Here is the schematic:-

But I am facing problem while driving the mosfet. The signal at gate of mosfet should be a PWM but the signal at gate is nothing like a PWM.

.

Also the drain to source characterstics look something like this:
Please suggest edits in the schematic so as to get the desired result. Also if required, I can provide schematic.

PS: I am simulating the circuit in LTSpice XVII

-------------------------X-----------------------X------------------------------

I generated the mosfet's symbol and now used it in the circuit.. But the plots are same after simulation.

The testing circuit as provided in the application note-

The circuit I simulated-

And the error-

If you want the error list of the simulation, you can find it here.

------------------X---------------------X--------------------

Here is the new schematic. I joined VE to source of mosfet.

Now the plot looks something like this (the simulation was stuck at 40%, so I had to halt the simulation.):

Plots after grounding Cathode:


texts: GPS performance issues with PCB layout with patch antenna

texts:
I am having trouble with the reception of my GPS module - a Quectel L76L. I am connecting the Antenna via a U.Fl connector. I know that the issue is somehow due to my layout because it works on a breakout board that I purchased (which used a chip antenna), but not the PCB I made. I’ve tried a whole bunch of things but none seem to work well. It takes well over 10 minutes to get fixed, and another 10 - infinity minutes to get readings. something is definitely not right.
Things I’ve kept in mind:

Transmission line - keeping the trace length below .25in
Vias - both many vids all around the signal for the coplanar waveguide and more sparse.
Trace width - I’ve used the calculated 50 ohm impedance of 42.2 mil and the 35 mil width that the GPS spec sheet recommends - Since the trace width is larger than the pad, which width should I use? I saw a video recommend to use a trace width as large as possible to match the chip’s pad (this would be 31 mil).
Using active antenna, so I am using a 10Ohm resistor and a 47nF inductor

Please see the layout below that did not work.. is there anything wrong that is glaringly obvious? Is it okay that I put the inductor pad on the micro strip?

Also, please see this design which I plan to send in for FAB. On this one I brought the antenna way closer to the GPS unit, I reduced the trace width to match the pad width of the GPS unit (31 mil), and added a bunch of bias that are a bit bigger. I also added a passthrough capacitor.

Does this design look like it will work? After about 6 iterations, I am at a loss of what could be the issue... Any advice will be much appreciated.


texts: What configuration should I use for a system that includes an ARM and an FPGA?

texts:
I have a design that uses an Altera Cyclone FPGA to implement a Physically Unclonable Function (PUF) and an ARM device to do cryptographic work and I/O with the PUF. The PUF is very large, and takes quite a bit of space (only about 1/4th will fit on the Cyclone)

My question is, would I be best served by getting a large enough FPGA to include both the PUF and the ARM core or a smaller FPGA for the PUF and a second, external ARM chip? Can you provide some suggestions?

If I used two chips, they would communicate with SPI. There is not a lot of communication between the two, nor does it need to be fast.


texts: When injecting a uniform power dissipation in a chip of IGBT power electronics modules by finite element method (FEM) in COMSOL (a good software for thermal analysis), a non-uniform temperature distribution appears in the chip. I mean a uniform power loss injection results in a non-uniform temperature distribution in the chip. I know this is due to thermal conductivity. But, how can I precisely explain the reason for that? I have googled a lot but I could find nothing.


texts: Detecting the distance of my dog to the food bowl

texts: When one of my dogs sneaks to another dog's food bowl, I want to be notified so I can stop it. I have EZ430-RF2500 (msp430) development kit. Is it suitable for such project? I also have Arduino so I could use rfid tag but is the detection distance sufficient? I want to be notified when the distance is ~15-20cm. Or what alternatives exist? And are they risky for the health of the animals? You can explain as if explaining to an idiot.


texts: Which wire is the positive and which the negative on this fan?

texts:
Here is link with the picture of the fan:

The fan name is "ZALMAN ZM-F3(SF) 120MM ULTRA QUIET FAN"

I looked it up online, but I don't understand, I'm colourblind and it's difficult to distinguish the colors.


texts: Why are we not always isolating the mains supply?

texts:
Something struck me: to protect people, the neutral of the supply is connected on the supplier side to Earth, so that leakage through ground is detected when for example someone touches the phase (residual current devices do that). It doesn't protect people who would touch neutral+phase at the same time though.

But wait a minute, if the neutral wasn't connected to earth (which basically is the case when we isolate the mains supply), there would be no path through earth so no chance of leakage. So why is the supply made like this then, what do I miss?

Figure to illustrate - the dashed line separates the supplier side and the user side.


texts: Can I use ST-Link programmer for non-ST chips?

texts: Can I program all kinds of SWD-programmable chips (ARM-MCUs) with ST-Link?


texts: What voltage or node are the BJT substrates connected to in a bipolar process opamp IC?

texts:
I've been recently experimenting with converting transistor-level SPICE models of ICs into subcircuits.  One thing I try to keep consistent with my subcircuits is that they remain floating; i.e. no internal connections to node 0 (aka GND).  This represents the real world more accurately, and also allows for inserting noise sources or series resistances into the ground pin on the subcircuit.  Any internal connections to node 0 would bypass these external effects.  I've successfully made behavioral opamp subcircuits which easily satisfy this.
Then, I moved over to trying my hand at an LM741 since its internal transistor-level schematic is available in the datasheet (page 7).  When I parsed the netlist into a text file to make the subcircuit, I was reminded that all BJT substrate nodes in SPICE are by default connected to node 0.  If I was making a logic IC or regulator IC subcircuit, I would simply remap the node 0 connections to whatever the ground pin on the subcircuit is.  However, this is an opamp and has no ground pin.  Just VCC and VEE supplies.
So this begs the question...what are the BJT substrates in a bipolar-based opamp IC connected to?  Are they connected to VEE?  Are they left floating?  Are they shorted to each individual emitter?  I know next to nothing about IC design, and this situation piqued my curiosity.


texts: What is the maximum number of simultaneous BLE connections?

texts: What is the maximum number of BLE peripheral devices that can be in connected state to a central, according to BLE specifications? Also existing hardware implementations seem to have limitations of usually 8 or 10, where does this come from, and is there a way to overcome this limit, apart from connecting and disconnecting as required?


texts: arduino pulse to transistor power maximum

texts:
Hello I want to get a confirmation that what I am doing is not going to fry my Arduino Mega.

The sketch I am using to send a pulse out on pin 8 to a 2n3055 that is switching 12 volts is this:

int pulse = 8;
int sensorValue;

void setup() {
  pinMode(pulse, OUTPUT);
}

void loop() {
  int sensorValue = analogRead(A0);
  map(sensorValue, 0, 1023, 1, 2000);
  digitalWrite(pulse, HIGH);
  delay(sensorValue);
  digitalWrite(pulse, LOW);
  delay(sensorValue);
}

I am using a potentiometer between the Arduino 5v and ground with the wiper going to pin A0.

simulate this circuit – Schematic created using CircuitLab

I want to know:

could I power this directly from my USB instead of powering the transistor  AND the Arduino from the source battery.
If they have to be both powered from the battery do I need to connect the emitter to the ground of the Arduino AND the battery to stop all the current from flowing through the Arduino ground and get a clean pulse or do I just connect the emitter to the battery negative and the signal will be OK.
In whatever configuration is best where is the best place to put a analog meter that is rated up to 3 amps so that I can see total power consumption of the board and the transistor circuit.
Lastly I am using this to pulse the high voltage side coil in a microwave transformer so it has a lot of impedance and when pulsing it it draws about 300 mA max so could I power the Arduino via USB and the transistor from the battery so that I can reprogram on the fly and have a set pulse instead of using the pot. (as in write the code for a certain delay and upload while running)


texts: Read Signals made of 8V square waves on an arduino

texts:
I am working on putting together an arduino board that would read signals sent between two modules in a car. The signals are sent as 8V square waves. An example of a message sent this way would be a sequence that is 12mS long consisting of a 8V high for 6mS then a 0V low for 9mS repeated back to back 14 times. The problem I am having is that if I put more than 5v into a digital pin on an Arduino I will blow the board. This get worse because with this being in a car it is completely possible that the digital pin might accidentally see full automotive voltage of roughly 15V.

My thought was to use a voltage divider that would bring 15V down to 5V this way even if the digital pin saw the full 15 voltages it wouldn't hurt the Arduino. I would also look at zener or other method for over-voltage protection.

My concern though is the timing is in milli seconds and I don't want the timing to be off or I won't be able to decode messages accurately. What I am really looking for is way to read these signal in real-time just at a lower voltage. Will this work or do I need to go a different direction?


texts: Switch individual MOSFETs connected across lithium-ion cell for passive balancing

texts: I am working on a passive cell balancing circuit using N-MOSFET. The cell voltage will be monitored by the micro-controller and it can also generate corresponding logic level signal according to over charge for a particular cell. I want to build a control circuit that can individually switch the N-MOSFET connected in series so that the a particular cell which is overcharged is discharged via resistor and the overcharge cell is balanced. How can I build a drive circuit for the N-MOSFET?


texts: How can I assemble and control two different hands on a watch face?

texts:
I want to make a device with two hands that rotate independently of each other, just like the hour and minute hands on a watch. I'm struggling to figure out how to actually design and implement this though.

Both hands should be able to rotate arbitrary amounts, either clockwise or counter clockwise, without concern for what the other hand is doing. I have a microcontroller with various I/O pins to send any necessary signals.

The two hands would sit at slightly different heights I assume, to prevent running into each other, but I don't know what to even search for to drive the two. Can you provide some suggestions?


texts: Using a PCA9306 voltage-leveler with an MCU and a 5.5v arduino sensor

texts:
This is what I'm trying to do:

I have an MSP430G2553 chip and I'd like to write an ADC program to translate some input from an arduino sensor (I have a few analog sensors that use 5.5v - some work between 3.3 and 5.5 volts).

I realized that my MSP430 can not connect directly to these 5.5v sensors so I decided to get the PCA9306DCTR voltage leveler from TI to bridge the gap.

My problem:

I'm not sure I understand how these voltage levelers work and if I'm thinking about this connection correctly.

My MCU is powered by a debugger (the MSP-FET) to the DVCC and DVSS and to pin 17 & 16 (for the Spy-By-Wire) protocol.

Considering the fact that the voltage on my MCU pin (say A0 - pin 2) is ~1.4v and the needed voltage into my sensor (say the: ultrasonic distance sensor) is ~5v, I connected the VREF1 pin on thePCA9306

to an external 3.3V supply coming from 2 AA batteries and the GND pin to the DVSS of the MCU (attempting to create a common-ground). In my mind the PCA9306 does not need a 5.5V supplier for the sensor.

Questions:

Do both VREF pins (both sides) have to be provided? Can I just add the ~1.2 - 1.4V from the MCU into VREF1 and expect ~5V coming out of the PCA9306?
Since most application designs include one single voltage power-source (be it 3.3V or 5V, etc.) can I assume that the voltage-leveler will raise the voltage from 1.4V to 5V without an external 5V power-source?
How are the serial-clock and serial-data ports used in my case? After connecting the  GND and VREF1 to 3.3V, do I connect my A0 (MCU pin 2) into the SDA1 and the ultrasonic sensor into the SDA2 of the voltage-leveler?
Am I going about this the right way? If not, what am I missing?


texts: How to design a 180 degree phase inverter for the feedback?

texts:
I am currently working on a multi-stage wideband amplifier (80-110 GHz) design with the goal of having 5-6 dB for each stage. The transistor that I am using has the transit frequency around 300 GHz (so we are not limited by the device). My objective is to use a capacitance and a phase inverter for the feedback to widen the bandwidth, something like this:

(Image source - Figure 5 from paper: Katayama, Kosuke et al. “An 80–106 GHz CMOS amplifier with 0.5V supply voltage.” 2017 IEEE Radio Frequency Integrated Circuits Symposium (RFIC) (2017): 308-311.)

Without feedback, the maximum gain that I could get was around 3 dB (+- 1.5dB) around the desired frequency range (in other frequencies less than 80 GHz, the gain was around 6-8 dB). Now, when I tried to add a feedback with a capacitor (calculated to be 38fF using the formulas and technique described here:
https://www.researchgate.net/publication/280204342_Theory_of_gain_and_stability_of_small-signal_amplifiers_with_lossless_reciprocal_feedback

Then, I tried to add the phase inverter with a simple 90 degree transmission line (microstrip line) that I got with Linecalc tool from ADS (with Zo as 50 ohms), the gain curve almost flat around 80-110 GHz but the gain (S21) is negative (around -5 or -4 dB).

I tried the following:

I noticed that S11 was far away (around 5-j*x) and the feedback signal is not flowing because of the impedance mismatch so, we tried to improve the matching at the input (S11) to 50 ohms by adding a series inductor (around 400-1000 pH) - it did not improve the performance.
Then I tuned the Width, length of the phase inverter (Microstrip line) and the capacitor values. (almost flat around gain around 4-5 dB) but I don't know the logic when I tune.

Could you please suggest some ideas to improve the gain in wideband (without tuning) with this technique?


texts: How to reach a required autonomy with a li-po battery?

texts:
CONTEXT : I'm working on a project consisting of making an underwater robot "fish" for an aquarium . and it is mandatory to get at least 8 hours of autonomy. I'm responsible of the electrical part of the project and during all of my bachelor degree i've never got any lecture on batteries and i have no idea on how to get what is required. But i managed to do some research and try to figure it out :
1- First , I took the power consumption of all the potential componants necessary for the project (motors & pumps, Usound captors, ucontroller and a set of RF reciever and transmitters) from the specs and datasheets available.
2- I Got a battery of a 1200 mAh capacity. The battery is originally used for quadrocopters, i figured it would be good for the project since it's relatively the same thing (a software and motors).

3- Thanks to some references (Battery university, Eletropaedia), I estimated the battery autonomy. I used an ideal estimation [=Battery Capacity/sum of power consumptions] and i supposed all the components worked 100% of the time.
The results i got is far bellow needed :(
Observations :
It seems that the pump is the only component to have an excessive consumption
Difficulties :

Since, like i said, i have no experience in the field. I don't know if the battery i'm using is good.
The pump seems to be necessary and irreplaceable. I talked to the mechanical team and replacing the pump with something else will make the project unrealistic.
The 8 hours autonomy is a necessity to the project's success.
The underwater environment.
Dimensions (less than 8 inches long)

QUESTIONS : First, is the 8 hours autonomy doable ? what should i do to get that ? Change battery ? Change pump ? Use a totally different approach ?
LINKS :
PUMP
BATTERY
Thank you for your time


texts: What's wrong with evaluation boards in production?

texts:
I've correctly tested an ESP32-WROVER MicroController and an ADXL355 sensor. Both these devices are on evaluation boards and the fact is that they are very handy: the MCU include an USB female, a battery case with a recharging system from the USB, a switch for turning on/off the system and most common protection systems for the hardware. The evaluation board of the device includes recommended protections from the datasheet.
If I was to implement all these nice features it would take me years and I don't think I could accommodate them in a smaller space.
That said, now I want to reproduce this system and maybe also sell this: is there something wrong with keeping on using these evaluation boards?


texts:
So, I use Altium 18 and I was checking the Board information for my PCB.

Under Nets, it showed total of 24 Nets and 0 Unrouted Nets. During my checks I found one of the nets was unconnected, yet the Board Information showed "zero" Unrouted nets.

So, I connected the net and then disconnected it. Only this time upon disconnecting the net, the count of Unrouted nets became '1'. Has anyone encountered anything like this? Is this a bug?


texts:
What are the big differences between a Half and a Full Bridge for a controlled voltage source? I know that by the Half Bridge implementation, bus pumping of the voltage source occure, which doesn't happen in a Full Bridge. But in the Full Bridge there is no defined potential. So are there other differences i don't see?

simulate this circuit – Schematic created using CircuitLab

Half Bridge-------------------------------------------------------------Full Bridge

Edit: with no diffined potenial, i ment there is a common mode. sorry english is not my native language.


texts: Arduino Recognizing pre-recorded sound clips from an audio stream

texts:
My project is to control a Nintendo 3DS hand held video game system from my Arduino Mega.
I have all the basic controls wired up and working well.

I need to be able to recognize the state of a video game being played by it's known audio cues.

Specifically, the Super Smash Bros fighting game. At the end of the match there will be a winner. The winner is announced with a known sound clip.

An example is: When Mario wins, there will be a known sound clip that plays with the announcer saying "The winner is Mario!".

To my advantage the "match winner" sound clip that plays are all known and will be EXACTLY the same each time it is played.

I need to recognize this specific sound clip and then have the Arduino press the "Start" button on the Nintendo 3DS to move the game to the next screen.

I have done numerous searches on FFT, FHT, Matched Filters, Speech Recognition, etc and have not come up with a solid way to do this.

I don't think speech recognition techniques work well since the audio is not a regular human voice, but a video game announcer "cartoon" voice with lots of background sound affects.

One theoretical approach I have is to somehow "train" the Arduino with pre-recorded sound clips and have it react when it hears them. Similar to the EasyVR Shield 3.0.

Any thoughts on how to do this?

Video of the sound clips: https://www.youtube.com/watch?v=VzC6psWEGM8

I am a software engineer and I am very comfortable around coding! Any help is appreciated.


texts: What type of Op Amp or comparator has a schematic symbol with hysteresis like symbol

texts:
I already know it is not a schmitt trigger, it looks like it is used as an open loop amplifier taking a reference voltage on the (+) and the V0 is fed into a schmitt trigger.

I have no other data. I wonder if it is "made up" like the symbol in  comparator schematic symbol.