texts: What can you tell about our circuit diagram? Any suggestions?

texts:
This is our circuit for our research which is the conversion of heat to electricity. The TEG module will convert the heat to direct current. It will give energy to the voltage booster moduleto and the voltage booster module will boost the electricity to 5V to charge mobile phones. If there is no mobile phone, the electricity will go to battery so that it will charge. We also want to charge the phone by using the battery thats why we have 2 switches. We are not confident in this circuit diagram. Can you help us please?

Note: We know just the basic of electronics here and as much as possible just simple bu effective diagram. Help us please!


texts: what is logic contention when using a voltage supervisor?

texts:
I am using a voltage supervisor from MAXIAM (MAX6734A).I am confused about design notes in page 11.

so,what is logic contention? the uP that I want to monitor is STM32F103ZET6.I read its datasheet:STM32F103.On page 30, it says that NRST pin is a IO type. Does it mean that I should consider it as a bidirection pin and use a resistor in series? what if I do not follow this design? I have no idea what the logic contention is.


texts: Emergency 3-phase power supply in the event of power failure

texts:
I have two Magnum 400 10/20 drivers running two stepper motors. Peak power consumption is about 2 kW.

In the event of a power failure on the 3-phase supply, I'd like to trigger a controlled emergency stop. Sudden uncontrolled stop could be fatal to the worm drive in the equipment, due to inertia on the other end.

But that means I have to supply power for an additional two seconds or so to control the motors during deceleration ramp.

How can I do that? Is there some sort of 3-phase UPS or generator that can kick in and do the job?


texts: What is that component alimenting a motor?

texts:
I'm building a mini backyard forge and need some air flow. I took apart an old hairdryer to remove the heating coil (to prevent it from overheating over long usage).
I found this component inside and I struggle to identify it.

What is that ?
Does removing the heating coil possible ? I recon it also act as a resistance, and I'm not sure what would append without it.
Here a crude schematics of the electronics:

simulate this circuit – Schematic created using CircuitLab
Thanks for your help.


texts:
I have a code that prints what's in the memory of my PIC18F4550 to the serial port. I'm trying to do this in two ways but only one is successfull. Can someone enlighten me why

Version one (functional, I think atleast..)
I've done some initializations and configurations prior to the code below

loop:
    btfsc TXSTA, 1
    movff POSTINC0, TXREG
    bra loop

Version two (not working..)

loop:
    movf POSTINC0
    btfsc TXSTA, 1
    movwf TXREG
    bra loop

Any ideas?

//Red


texts:
I've got a TI LM3S Cortex-M3 Development board with USB host. I've done quite a bit of TCP/IP programming through the Ethernet and using SPI/UART GSM modems, but I was wondering the feasibility of getting web access through a USB 3G 'dongle'.

From my brief bit of research, I can see most of the modern modems support this through CDC-ACM and/or RNDIS but having only 256k flash and 96k of RAM am I being a bit too ambitious? So far I've only found commercial libraries for this and I haven't looking into the complexities of doing myself.

Should I just be looking at ARM9 and Linux?


texts: Reading a resolver sensor with a long cable

texts:
I am trying to read a resolver sensor attached to a stepper motor through a long cable (500 meters). More specifically with a resolver to digital converter.

However I get an error respect to the actual position like in the figure, error that is not present using a short cable instead of the long one.

In the right figure, the error in degrees is represented against turns of the motor (1 turn=360 degrees). It is clear how the error is repetitive. In fact the error is very close to this one at different rotor speeds, and with different excitation signal (7.5 kHz) peak to peak voltage values.

Assuming that in the cable there is coupling between the sine and cosine signals from the secondaries, I can reach only an expression explaining a second harmonic error with the motor position, but not the first harmonic. And the error fits quite well with a 1st + 2nd harmonic of the motor position, as shown in the following figure:

Any idea of what effect might be producing this kind of error?


texts: Esp8266 - can I use a 3.7v liion cell without a regulator

texts:
I'm more of a hobbyist than a pro so forgive me if I'm asking the wrong questions however I have put some time into finding a solution to this problem.

In essence I want to run an ESP8266(esp-12f to be specific) on a single 3.7v liion cell. However reading into the esp's voltage tolerances it appears as though it's important to use 3.3v to prevent damage or browning out. As such do I need to use a voltage regulator like the lm1117 or would be acceptable to run the esp directly from the cell.

If the latter is acceptable, would I need some form of low voltage cut off circuit to prevent draining the cell too much?

Thanks in advance


texts: STM32 HSE clock is affected by LTDC_DE signal?

texts:
My STM32F429  project works fine before I added the LTDC module generated by CubeMx. After I added LTDC, the FMC interface began to lost data occasionally which was good before. I thought it may be caused by HSE instability. In order to test the HSE clock, I measured the MCO signal which shows the greate difference after LTDC is added.

Before:

After:

I comment HAL_LTDC_MspInit() line by line and find the cause of HSE instability is LTDC_DE signal initialization. When I comment following code off(PF10: LTDC_DE), the MCO clock show correct.

GPIO_InitStruct.Pin = GPIO_PIN_10;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
GPIO_InitStruct.Alternate = GPIO_AF14_LTDC;
HAL_GPIO_Init(GPIOF, &GPIO_InitStruct);

However, I still cannot understand why this signal makes HSE failure and how can I fix this issue because LTDC is needed in my design?

This is clock configuration

Edit1: Add zoomed-in waveform before and after LTDC added.

Before:

After:


texts:
There was a wide GPIO functions in the CMSIS initial versions which made easy setting and initialization of interrupts,like:

void    GPIO_IntCmd (uint8_t portNum, uint32_t bitValue, uint8_t edgeState)
Enable GPIO interrupt (just used for P0.0-P0.30, P2.0-P2.13).

FunctionalState     GPIO_GetIntStatus (uint8_t portNum, uint32_t pinNum, uint8_t edgeState)
Get GPIO Interrupt Status (just used for P0.0-P0.30, P2.0-P2.13).

void    GPIO_ClearInt (uint8_t portNum, uint32_t bitValue)
Clear GPIO interrupt (just used for P0.0-P0.30, P2.0-P2.13).

Above functions made easy enable interrupt for LPC1768 MCU,but know i want do same for LPC1788, I am using latest CMSIS version which does not support none of the above functions(there are only direction definition and read/writing functions).
whats their alternative in the new versions?


texts:
I was writing Verilog code for an ALU from the nand2tetris course
This code compiled without any errors in ModelSim but when I try to start simulation it throws an error
Error loading design Instantiation of 'addtwobit' failed. The design unit was not found.
P.S- Kindly ignore the use of many always blocks.
module alu(x,y,zx,zy,nx,ny,f,no,op);

    input[1:0]x,y;
    input zx,nx,zy,ny,f,no;
    reg [1:0]zxx,zyy,nxx,nyy,fo;
   wire [1:0] zxxn,zyyn,anf,adf;
    wire zxx1,zxx2,zyy1,zyy4,fo1,fo2,co;
    output reg [1:0] op;

    always @(*)
    begin
    case(zx)
    1'b0:zxx=x;
    1'b1:zxx=0;
    endcase

    case(zy)
    1'b0:zyy=y;
    1'b1:zyy=0;
    endcase

    end

    not n1 (zxx1,zxx[0]);
    not n2 (zxx2,zxx[1]);
    assign zxxn={zxx2,zxx1};

    not n3 (zyy3,zyy[0]);
    not n4 (zyy4,zyy[1]);
    assign zyyn={zyy4,zyy3};

    always @(*)
    begin
    case(nx)
    1'b0:nxx=zxx;
    1'b1:nxx=zxxn;
    endcase
     case(ny)
     1'b0:nyy=zyy;
     1'b1:nyy=zyyn;
     endcase
     end

     and a1(anf1,nxx[0],nyy[0]);
     and a2(anf2,nxx[1],nyy[1]);
     assign anf={anf2,anf1};

    addtwobit(nxx,nyy,adf,co);

    always @(*)
    begin
    case(f)
    1'b0:fo=anf;
    1'b1:fo=adf;
    endcase
     end
      not n5 (fo1,fo[0]);
    not n6 (fo2,fo[1]);
    assign fno={fo2,fo1};

    always@(*)
    begin
    case(no)
    1'b0:op=fo;
    1'b1:op=fno;
    endcase
    end

    task addtwobit;
    input reg [1:0]nxx,nyy;
    output reg [1:0]adf;
    output reg co;
    begin
    //xor x1(adf[0],nxx[0],nyy[0]);
    //xor x2(adf[1],nxx[1],nyy[1]);

    //and a1(coo[0],nxx[0],nyy[0]);
    //and a2(coo[1],nxx[1],nyy[1]);
    //or o1(cof,coo[1],coo[0]);

    //adf={adf[1],adf[0]};
    adf={nxx[1]^nyy[1],nxx[0]^nyy[0]};
    co=(nxx[0]&nyy[0])|(nxx[1]&nyy[1]);
    end
    endtask
module alu_dut2;
reg [1:0]a,b;
reg zx,zy,nx,ny,f,no;
wire [1:0]op;
alu alutb(.b(y),.zx(zx),.a(x),.zy(zy),.nx(nx),.ny(ny),.f(f),.no(no),.op(op));
initial
begin
$monitor($time,"a=%d , b=%d zx=%d , zy=%d , nx=%d , ny=%d , f=%d , no=%d , out=%d",a,b,zx,zy,nx,ny,f,no,out );
#5 a=3;b=2;zx=0;nx=0;zy=1;ny=1;f=0;no=1;
#5 a=3;b=2;zx=0;nx=0;zy=0;ny=0;f=1;no=0;
#5 a=3;b=2;zx=0;nx=0;zy=0;ny=1;f=1;no=1;
#5 a=3;b=2;zx=0;nx=0;zy=0;ny=0;f=0;no=0;
#5 $finish;
end
endmodule

endmodule


texts:
I want to design LED switching circuit using N-Channel(BSS123) MOSFET.  Please find the supply details in the image.

What formula can be used to calculate the value of R1?
How VDS voltage impact here?  How can find that?  What is the formula for that?


texts: Switching 12V vehicle headlights with Arduino / Mosfet combination

texts:
Ground level noob here, started to tinker with electronics at the beginning of this year after I couldn't get any electronics shop in my town replace my bike's gauge cluster SMD LEDs.
I learned few things last few weeks and now I'm at the mosfet stage. I want to control the headlight with mosfet and I managed to assemble a code for Arduino IDE that controls the LED the way I want, tested the 12V 25W LED bulb on my desk with bench power supply and Arduino hooked to buck converter, with the LED bulb controlled with a breadboard size pushbutton and a mosfet. I bought the wrong (high Rds, not logic level) nMOS at first, but learned to read some specs and got IRL2203 that operates the light and keeps cool with no heatsink.
The challenge is how to install it in the vehicle while keeping the original controls intact and without adding anything extra. I am going thru YouTube vids on schematics and trying to figure out where in the "headlight circuit" should I tap in with the Arduino and mosfet. One thing that kind of worries me now, I'm starting to think I planned this wrong going with the nMOS and all, I highlighted all the headlight-relay wires and it seems that pMOS would be the correct choice to tap into these wires, and accessing ground wires for nMOS would be too challenging?
As I'm not well versed in these, please let me know what can I do here.
One idea I had was completely remove headlights from the circuit, from the relay and everything, and run a separate circuit from headlight fuse? Just thinking out loud :D Let me know how would I go about solving this, cheers


texts: How to "auto-disconnect" from rs485 bus when power off

texts:
I have many devices on a RS485 bus.

When I disconnect power from one device,
the rest of the (powered-on) devices seem to communicate with each other just fine.
At least it seems to be working today.

Is that a standard feature of most RS485 transceivers -- when the power goes off, let the other devices on the bus keep talking?

Or am I lucky today, and there is something else I need to do (what?) to guarantee the powered-on devices can continue to communicate tomorrow, even when powered-off devices are connected to the bus?

Is a RS485 transceiver that specifically spells out in its datasheet it's worst-case load on the bus, when the chip loses all power?
(I don't see any such specification in the datasheet for the
Exar SP485E (datasheet) transceiver
I'm using today,
but perhaps I'm overlooking something?)

(My understanding is that RS485 is specifically designed to run on long cables between boxes that are unlikely to both be turned on and off simultaneously, unlike the bus in How to interface with a bus that's powered when the rest of my circuit is off which was designed for all-or-nothing everything-on or everything-off systems).


texts: Verilog implementation - variable range error for a register assignment

texts:
I am trying implement the following idea in Verilog. I tried giving variable range and got an error that error must be bounded by constant values.
There is an 8-bit register which gets updated on every clock cycle. I am required to incrementally take values from this register i.e.
reg[0] in the first iteration,
reg[1:0] in the second iteration,
reg[2:0] in the third iteration
and so on. The output from this register along with a decreasing number of zeros are given to a 12 bit register i.e
{reg[0],11'b00000000000} in the first iteration,
{reg[1:0],10'b0000000000} in the second iteration,
{reg[2:0], 9'b000000000} in the third iteration.
How do I generalize this ?
My original code:
module FGen (Clk, Reset, F, Aplusone, sjplusone);
input logic Clk;
input logic Reset;

input logic [1:0] sjplusone;
output logic [11:0] F;
output logic [7:0] Aplusone;

logic [7:0] K, A, B, Bplusone;
logic [7:0] Z;
logic Kout;
int count = 0;

assign A = 8'b00000000;
assign B = 8'b00000000;
assign Z = 8'b00000000;

shiftreg #(8) shr (Clk, Reset, Load, 1'b1, 8'b11111111, K, Kout);
mux2 #(8) m1 ({A[6:0], Kout}, {B[6:0], ~Kout}, sjplusone[1], Aplusone);
mux2 #(8) m2 ({B[6:0], Kout}, {A[6:0], ~Kout}, ~sjplusone[1], Bplusone);
mux2 #(12) Fmux ({2'b11, ~Aplusone[count:0],Z[8-count:0]}, {2'b00, Bplusone[count:0] - 1'b1,Z[8-count:0]}, sjplusone[1], F);

assign count = count + 1;

endmodule


texts:
I am working with ADC on MCU SH7147 (Renesas).

I have a problem with a sensor as outlined below.  How do I detect a disconnect of the sensor cable on the analog input pin on the MCU?

I tried to check it by cutting the the wire and seeing the analog data display in LCD, but it is  random data, it is difficult to make a rule to detect disconnect.


texts: What is the maximum power transmitted through NFC that can be harvested?

texts:
What is the maximum power an NFC-enabled card can draw from a contactless payment terminal? What are the determinants (i.e. card reader voltage)?
What techniques are available for harvesting this current?
Background: Trying to figure out what the power threshold is for say a biometric sensor on a payment card is.

Thanks!


texts: Which relation in the data-sheet shows the frequency vs gain relation explicitly?

texts:
This opamp output starts getting distorted at around 10kHz and the amplitude halves around 25kHz.

Where in the data-sheet shows the relationship between the frequency ant the attenuation? Something same with Bode plot.

EDIT:

To clarify I had to simulate the circuit what I observe via a scope:


texts: Does switching off electrical devices while the main switch is still ON do any good?

texts: Suppose the main switch of a TV is ON, but the TV is OFF, will it make any difference than when the TV is ON. If the switch is ON, but I switch OFF the TV, will it save electricity than when the TV is ON? Thank You.


texts:
I have this Polycom conference phone and the plug came off when someone tried to plug in the battery. It looks like it was kept in place with some kind of double sided tape instead of solder.

I can't really solder, so I wanted to redo the tape, but could you advise what kind of tape should I buy?

Picture attached.


texts: I want to analyze transistor transient characteristics. What should I do first?

texts:
It's a new task for me, so I want to ask more experienced engineers. I make a "soft-start" circuit for laser driver. And I got more problems with transients. This circuit must be works like aperiodic link with slow current increase. I don't know how to proceed for mathematical computations of tranisients in bipolar transistor. What I have to do at the beginning?

This is my circuit.


texts:
Lately I have been studying the BJT and its respective Transport/Ebers-Moll models with the equations for the Base, Collector and Emitter currents. Assuming an npn transistor, applying a constant forward bias to the Base-Emitter junction and very slowly raising the collector voltage in respect to Emitter, there is a voltage on the Ic(Vce) output characteristic curve for this given Base current, beyond which the Collector current is no longer a linear function to the applied Vce. Instead, it starts "curving"(sorry, english is not my first language), tending to become constant. The point which the current becomes constant is when Collector and Base Voltage difference is 0, Vbc=0, but this point is reached for a higher Vce  than Vce,sat. The regime between Vce,sat and Vbc=0 is called "quasi-saturation" I think.
There is a formula for the saturation collector emitter voltage which I don't know where it is derived from. See picture. it is taken from the book of U. Tietze Ch. Schenk Halbleiter-
Schaltungstechnik. beta_n and beta_i are the current amplification parameters for normal and inverse Operation respectively.
Any ideas which condition is assumed for the derivation of this formula?


texts:
Just wanting to learn more about this stuff but can't find any resources based on what i know to ask.

This tower has several of these strange looking sets of 2 bent tubes all facing the downtown area. What are they? On an FM tower. Just wondering the function of such strange configuration since all FM transmitter picture i find look nothing like them.


texts: I was testing few types of transistors on my newly acquired peak atlas pro and came across some N-channel depletion mode JFETs marked 2n3819. To my surprise the device indicated they are NPN BJTs. Using my fluke multimeter in diode mode, the voltage drop from centre pin (2) to other two (1,3) was a normal diode voltage drop for each pair and also resistance between 1 and 3 was OL. I understand that if they were real JFETs, the resistance between drain and source would be low, which is not the case for these transistor as they showed OL. Additionally, Peak atlas showed the parameter as hFE=286 at Ic=5mA, Vbe= 0.749v at IB=5Am etc. I am confused, according to the peak atlas manual, the analyser should be able to identify and analyse JFETS. Are my transistors faulty or fake ?


texts: Low-cost, low-current solution for dropping 1V from a battery

texts:
I have a 3 x 1.5V NiMH battery pack giving a supply voltage in the range [3.0V ... 4.5V] depending on the remaining capacity. In order to prolong battery life I need to cut power from the entire PCB except for the MCU sleep module that consumes a few uA. The catch is that the sleep module is rated at [1.8V ... 3.6V] and I cannot afford an LDO for this purpose.

Is there a way to achieve a voltage drop between 0.9V and 1.2V without any significant current draw?


texts:
I have a power transformer from an old solid state guitar amp from the 70s and it is extremely noisy. I isolated the issue in the sense, that I took it from the device, stripped it from its case and powered it without load. The loud buzz still occurs.

Now it seems difficult to find a direct replacement transformer that delivers 52VAC on the secondary with 230VAC on the primary and the right power rating. Therefore I see two options. Either pot the thing or rewind it all together.

What would you suggest? And depending on your answer, could you point me to appropriate resources?


texts:
In a circuit I design, there is a moment, when a capacitor should be discharged through a resistor.

The power dissipated in the resistor has the format of the screenshot in the LTspice.

Should I select the average as a power rating and thus choosing a 1/4 watt resistor or should I select a bigger value?

As it can be observed, the power will reach 4 watts at the starting of the discharge phase.

Thanks a lot,
George


texts:
I'm new in Verilog and I need to create a module that when Entry=1, it will increment 5'b000100 in the "Money" output.

This is the code that I made, but it's not working properly. The program it's not storing the total of the money(that's what I want my program to do).

For example,
Everytime a person enters a football stadium, she pays for the ticket, and my machine will store the total money gained. The maximum of people that can enter the stadium is 15 (thats why I used 6 bits, because 4*15=60)

My "machine" isn't storing the total earned.

My code

    module Machine_Money(Entry, Money);
         input Entry;
         output [5:0] Money;
         reg [5:0] Money;

            always@(Entry)

                begin
                Money = 6'b000000;
                    if (Entry)
                    Money = Money + 6'b000100;
                end
   endmodule

Thanks.


texts: Which 74xx logic families are overvoltage tolerant on their outputs?

texts:
Here's my dilemma: I have a 3.3v active-low logic line, and I want to use it to drive a 5v active-low logic line. The 5v line already has a pullup, so my plan was to use an open-collector buffer IC like the 74LCX07, with its VCC at 3.3v, as a buffer.

This seems fine, but I've read that many 74xx logic families have ESD protection diodes on the output, meaning that applying >VCC to their output pins - even open drain ones - will feed current into the chip's VCC via the ESD protection diode.

Is this the case? If so, which if any of the 74xx families are safe to use like this?


texts: Why is LED lighting up despite Supply voltage < Forward voltage

texts:
I have an LED which has specified Typical forward voltage of 3.5V and Maximum forward voltage 3.9V.

I applied 3.3V across it with a 300 Ohm resistor in series. Why did it light up?

I am wondering if I can pick this LED as a reliable choice for my design (which as noted runs at 3.3V supply across the board).

My thinking:

The LED datasheet has a curve of Forward voltage vs current (I'm also confused why they put Forward current on the Y-axis instead of X, given that current is what one would vary here). Anyway, the curve shows a decrease in the forward voltage at smaller currents; perhaps this is the explanation?

Here is the downloadable PDF datasheet for this LED (it's a tricolor LED and in this question, I was referring to the specs for Blue and Green).


texts: Does a resistor block or dissipate electricity?

texts:
Say, I am using a Red LED which takes 20mA current from 2.0V battery. (I don't know if its the right specifications but I checked from this PDF I found on Google.)

So, since I will be using a 9V battery so, I will need at least a 350 ohms resistor to resist the 7V coming from the battery.

What happens to this extra 7V of power? Does it go unused, dissipates as heat, or simply gets blocked from resistor such that it draws only 2V from battery?


texts: Identify PCB power connector for LED light

texts:
Recently, a rubber ring around the LED light inside my dishwasher broke, causing water to leak through. When it was replaced, I kept the old LED and I want to install it inside a closet, but I don't know the power connector to it.

Can anyone tell me what this connector is called and possibly what male cable I would need to connect to it?

There seems to be a place for 4 pins, but I don't know if it's in any way related to Molex.

Thanks in advance!

EDIT

Two images of the top and bottom of the PCB


texts: How to find electrical conductivity from frequency in my PLC project

texts:
I am using a 555 timer which is supposed to measure the electrical conductivity of milk. Here's a circuit for a conductivity sensor:

It provides the needed isolation, uses AC measurement, and the output is a frequency which I have wired into my PLC digital input port. When the 2 probes are held in air, the frequency output is 42 Hz. When the probes are inserted in water, the frequency changes to ~8000 Hz depending on the length of probe inserted in water. My question is: How do I convert (mathematically) my frequency measurement to conductivity measurement in terms of siemens?


texts:
I’m trying to simulate thermal (Johnson) noise. As I understand it, thermal noise follows a Gaussian distribution, power at the receiver is given by:
$$
P = 4kTB
$$
And the RMS voltage is given by:
$$
2\sqrt{kTBR}
$$
(See https://www.sciencedirect.com/topics/engineering/thermal-noise)
Let’s say I wanted to produce some simulated thermal noise (a voltage vs time plot, given some digitization rate) in, say, MATLAB or a similar software. How would I go about this? Is the mean of the Gaussian given by \$V^2/R = 4kTB\$? Or should I generate Gaussian distributed random power values, with a mean given by \$4kTB\$, and then calculate the voltage? But shouldn’t the mean of the Gaussian be 0? I guess I don’t entirely understand what exactly is distributed as a Gaussian, about what mean it’s distributed, and how to calculate voltage.


texts: How to use mikroC oscillator frequency in my code?

texts: I am using mikroC pro for PIC. In the "Edit Project" window there is an option for setting oscillator frequency. I want to use that value in my code. I think it can be used like something that is defined using #define, but I don't know the name of it. Does anyone know it?


texts: Can a piece of metal with a specified shape resonate at a certain frequency?

texts:
I asked this question because I've read that antennas resonate at a certain frequency depending on its length. However, they are connected to some wire or coaxial cable, which I thought might be the reason why they are able to resonate.
What I am asking is whether we can say the same (it resonates) for a piece of metal rod with a specific length, but unconnected to any cable or wire whatsoever, If they intercept electromagnetic waves?


texts: Can I use any HV Probe for a Voltmeter/Ampmeter gauge?

texts: I purchased the multimeter pictured below for a high voltage power supply I'm working on. It's rated for 100V DC and 10A, but I hope to measure several thousand volts. Is it possible to use a HV voltage probe like I would use with a regular multimeter on this component, or no?


texts: Circuit protection - Is this sufficient?

texts:
I have a situation where I need to test a PCB to make sure it is working correctly. This PCB has 2 power and 2 signal lines (and GND). The 2 power lines are 12V and 3.3V. The signals are all 3.3V.
Basically, I plug this board into my test jig, and a microcontroller checks all the signals are sending the correct stuff.
The issue I am having is the PCB placement company made an error and managed to short out the 12V to one of the signal lines. This completely took out the microcontroller of the test jig. This happened 3 times, which meant replacing the micro each time, before I managed to trace the exact cause.
Hopefully, this issue is now resolved, but it has shown me that it is possible this could happen again, so I want to put in some sort of protection circuit so if either of the signal lines are shorted to the 12V, the jig will be fine. The circuit I have come up with so far is this:

simulate this circuit – Schematic created using CircuitLab
This seems to work well. If there is a short between the 12V and any of the signals, it brings the inverting input of the comparator higher than the non inverting, and stops the signal passing through to the jig. I purposefully haven't included part numbers or values for anything as I am yet to get to the part selection phase.
My question is, will this circuit be sufficient to protect the test jig? Or is there something I am missing? Would perhaps some form of isolation be more appropriate?


texts:
I recently received a variac variable ac transformer. It is a older model so I decided to modify it a bit. I will add analogue amp and volt meters to show what the "current" out put is(pardon the pun) and add a bridge rectifier in parallel to the ac output so I also have a (diode and resistor stabilized) DC output. My question is if it is sufficient to have a automatic fuse(at the rated output amp) on the ac output from the variac before dividing it to go to the ac socket and the rectifier  and dc socket (only one to be used at a time)or will the amperage change with the voltage level and requiring a dc fuse after the rectifier and at what amp rating?

I borrowed and modified this picture.
Is this a good way to do this or is R1 not needed or even a mistake?

Update. I finished the variac build but did not have room for the dc side, I did run in to a problem however the automatic/resettable fuse I used in series with my output in order to protect the variac will not trip at (or near) the rated 2,5A (250 vac). I tested with a near short through a 1 ohm 100w resistor and the 0-3A meter went of the scale yet the fuse did not trip, any idea why?


texts: Can the coil in a magnetic field be replaced by a copper mesh?

texts:
From theory, I remember that EMF induced is a function of the rate of change of magnetic flux. A generator is typically a changing magnetic field applied to a bunch of diamagnetic wires wound closely together over a laminated core. Part of the reason for the close winding is probably to expose as many turns as possible to the changing flux.

I'm thinking about using a fine copper mesh like this one:

That mesh was earlier an antenna on an old old old valve radio instead of a coil.  It's also used in Faraday cages.

What would happen if I used this the micro turbine I'm thinking to attempt? Worst condition is probably a brown-out if the induced current follows different paths ....

EDIT: The intent with using the mesh is as an experiment to try something different (+: A friend has a repair shop, and the facilities to do the winding if required


texts: can connecting a tristate buffer output to 0 or 1 make problem?

texts:
in this circuit the control line is connected to GND so the output is Z. is there any problem to connect the output line to 1 or 0?
if the control line turns to 1, what happen to the circuit?
what is your answer about the second circuit which is made with transistor?


texts:
I am building a street lamp controller that should be able to set a street lamp to on, off, or dim state. I have successfully built an incandescent lamp dimmer (phase dimming - using zero cross detector, AVR microcontroller, and controllable TRIAC driver). Now I am interested in building a similar thing for street lamps.

From my reading most street lamps still use HID lamps (metal halide, mercury, high pressure sodium) and they are not purely resistive so that some people in other forums state that they cannot be dimmed using phase dimming method. For example see http://www.edaboard.com/thread115980.html

My question is how should these kind of lamps (metal halide, high pressure sodium) be dimmed. This seems possible since I have seen such dimmer products in the Alibaba store but the manufacturer cannot tell me their method. What waveform should be expect?

Update 26/3:

Based on NEMA standard, HID lamps can be dimmed: step level or continuous (phase control, high frequency shifting). The limitation is: power level and RMS voltage: cannot below specified value (determined by ANSI or lamp manufacturer)
Phase control is somehow unsuitable (leading phase control may introduce flickering while lagging phase is dangerous for inductive load such as HID ballasts)
High frequency shifting is a method that is so far, according to NEMA, seems safe enough for dimming.
So far, the recommendation is to use step level switching (be aware of minimum power requirement) and, most importantly, consult lamp manufacturer

My question is, according to Russell's link here, HID lamps is operated at low frequency to avoid acoustic resonance (may ended in damage or lamp explosion). So, if I apply high frequency shifting on the ballast input, this will not affect the low frequency output of the ballast. Is this true?


texts:
I'm looking for a particular type of mini SPDT switch, it has 3 poles (if memory serves correct, could be 2 pole) and has 3 total positions. By default it's centered and is set to an off state. If it's toggled up, it remains ON, if it's toggled down, it will function as a momentary and will spring back to the center off position once released.

I'm not sure what this switch is referred to as and have had a heck of a time finding them in electronics hobby stores and even online.

Does anyone know what these switches are referred to as?

Thank you.


texts: Charge a supercapacitor safely using mobile charger

texts:
I am not much experienced with electronics. But I am aware that supercapacitors must be charged with lower voltages than rated. I want to make a simple spot welder using this capacitor.

I have the following things. Can someone tell me what is needed (resistors/Schottky-diodes) and how to connect them?

100F 2.7V super capacitor
5V 1.0A mobile charger, non branded
multimeter for measurements

I want to charge the capacitor at 2V and then short it over nickel strip to weld the strip to 18650 battery terminal.


texts: Disciplined oscillator using counter+micro

texts:
I am working on implementing a disciplined oscillator to increase the accuracy and long-term stability. The oscillator would be a VCTXO running at about 25 MHz. My thought is to have a 32-bit counter that would count each clock cycle. A GPS 1PPS would be used as the time reference and counting would begin on a given pulse. After a number of pules (maybe one, maybe 100, maybe some other value), the count would be read out by a micro controller and a feedback signal generated to either slow or speed the frequency of the VCTXO.

As a more concrete example, a 25 MHz oscillator would ideally have exactly 2,500,000,000 pulses in a 100-second period. But the actual count will certainly be either high or low. Based on the actual count, a correction signal would be applied to the VCTXO to speed it up or slow it down. The long term oscillator stability and accuracy would thus be linked to the time reference

My main difficulty is finding a suitable counter.

I would like something that is 32-bit (gives something like 200 seconds between rollover).
The counter should be small. I'm developing for a low-power mobile device. A single ic 4 to 7 mm in size would be ideal.
Ideally, counter readout would be over SPI to support the current micro controller. For size and simplicity, I would prefer not to use a parallel bus to read out the counter value.
Thoughts on synchronous vs asynchronous counters?

I am open to different technologies that could be used as the counter (separate micro, FPGS, CPLD, Flip-flop array, etc.) Please give suggestions on how to implement.

I did come across the LS7366R-TS (http://www.lsicsi.com/pdfs/Data_Sheets/LS7366R.pdf) which seems like something that might work, but I cannot seem to find it for sale anywhere. I've contacted the company and not yet heard back. But I also wonder if there are alternatives ic's and methods that might be better suited and more readily stocked. Please let me know if I need to further clarify the problem.


texts: ESP32 Sample a 1kHz square wave (10%-90% duty cycle) with analogRead()

texts:
I need to sample the peak voltage of a 1kHz square wave. The duty cycle varies between 10% and 90%. I am using an ESP32 and hoped to use analogRead() to sample the data.

My first idea was to attach an interrupt to a digital pin being fed the square wave. It seems that the analog read only sometimes happens on time. The first signal in this image is the input signal at roughly 50% duty cycle. The second is the start and end of the analog read:

  digitalWrite(32, HIGH);
  int level = analogRead(CP_READ);
  digitalWrite(32, LOW);

As you can see, the reads sometimes occur after the falling edge of the input signal even though the interrupt was attached to RISING. Curously, setting it to FALLING yields exactly the same result as above. Also, it doesn't even seem to trigger on each rising/falling edge. As you can see, it skips 2 pulses...

Here is a small sample of the output:

Current CP voltage level is: 4095
Current CP voltage level is: 2925
Current CP voltage level is: 955
Current CP voltage level is: 3687
Current CP voltage level is: 1344
Current CP voltage level is: 0
Current CP voltage level is: 4095
Current CP voltage level is: 4095
Current CP voltage level is: 4095
Current CP voltage level is: 4095
Current CP voltage level is: 3149
Current CP voltage level is: 1044
Current CP voltage level is: 0
Current CP voltage level is: 4095
Current CP voltage level is: 4095
Current CP voltage level is: 4095
Current CP voltage level is: 4095
Current CP voltage level is: 2737
Current CP voltage level is: 784
Current CP voltage level is: 3423
Current CP voltage level is: 1198
Current CP voltage level is: 0

In my test case, it should always be 4095...

This is the whole interrupt:

 void IRAM_ATTR isr(){
      digitalWrite(32, HIGH);
      int level = analogRead(CP_READ);
      digitalWrite(32, LOW);

      Serial.print("Current CP voltage level is: ");
      Serial.println(level);

}

Is there anything I should know about the ADC? is there a sort of "setup" time that is required to get it going that I can account for?


texts:
i am trying to create a digital logic trainer. to provide inputs through switches and outputs through LEDs, however when i connect the logic gates to the switches they don't work the way they are supposed to do. i am guessing that the gates need high or low not on or off.
can you guys explain or direct me to a link to a switch that can provide high when activated and low otherwise.
for example this is the scehmatics :

simulate this circuit – Schematic created using CircuitLab

thank you!


texts: How can I use my Arduino together with an external power supply?

texts:
I am trying to design a simple square wave inverter (15V input from my power supply). For this purpose I will design a H-bridge with 4 MOSFETs controlled by the Arduino (5V or 3.3V output). The thing is, how can I make my power supply and Arduino work together? I only need the Arduino to control transistors (to make them let current pass).

Sorry for the bed design, as it is my first year in Electrical Engineering. This is the incomplete circuit design. The transistors in the scheme will be controlled by the Arduino. It will make blue ones OPEN first, then it will make red ones OPEN. So polarity will constantly change for the "Device." But I don't know how I can integrate the 5V Arduino here.


texts: Capacitor as Noise removal (Theoratical)?

texts:
I am reading about the capacitors. I have read that the capacitors block DC and behaves as open circuit in DC while short circuit in AC. The reason behind this is the charging and discharging of the capacitor. What is my perception about it, I will mention about it.

"
During the DC voltage the capacitor charges up. During this charge process the negative charges from the battery comes in the wire and then get store on the plates and on the positive side there is a deficiency of charges on the plate as the electrons are attracted by the positive terminal of the battery. Due to this deficiency of charges an Electric field is generated that opposes further movement of electrons towards the positive side and stop the excess amount of electrons on the negative plate side. When this potential strength is equal to battery potential then the  the impact is neutralized and no further movement happened and thats where the electrons started flowing on the other path and capacitor behaves as open circuit"

Now for the noise filtering capacitor they are actually connected for noise removal so that the current can safely go out. It makes sense that the noise in the form of sudden spikes comes from power supply. What I am confused is the statement about the capacitor behavior for this sudden spikes. I have read the capacitor gives the path of the Ground towards sudden spikes which is according to me is utterly wrong. Because no electrons pass through the dielectric material.

According to the above explanation for the DC voltage, the capacitor is in stable state. If the sudden spikes of voltage come in (Obviously High Frequency) then the equilibrium of Electric field between the plates and voltage is disturbed and capacitor started charging again with the access charge (More electrons come in from the negative side and more positive charges or electrons departure from the positive plate). But when the spike is over the capacitor is required to discharge in order to reach to that equilibrium again. Now there are two ways of going back towards equilibrium.
    1) If the capacitor negative plate loose electrons and positive plate gain some electrons  (This is not possible)
    2) If the electrons cross the dielectric and reach towards positive terminal of the battery (This is again not possible)

My logic is not conventional flow, it is electron flow. May be I am totally wrong but please help me to solve this dilemma.


texts:
I am using an Arduino uno R3 with the motor shield R3 with 1 DC motor (http://www.maplin.co.uk/small-motor-3738) pluged in by the USB port (because I dont have a proper power cable). When i first used the DC motor it went way too fast so i turned the speed down but then it didn't start so I turned it back up to 255 the speed I started with. The motor still didn't start so I tested the motor with a 1.2 volts fully charged rechargeable battery and it worked fine as before but when I plug it into the Arduino it only makes a quite noise. The LEDs on the shield also seem to be dimmer than before.

This is the code I used

const int pwm_cha = 3;
const int dir_cha = 12;
const int brake_cha = 9;
const byte motor_speed = 270;

void setup()
{
    pinMode(pwm_cha, OUTPUT);
    pinMode(brake_cha, OUTPUT);
    digitalWrite(pwm_cha, HIGH);
    digitalWrite(brake_cha, LOW);
    pinMode(dir_cha, OUTPUT);
    digitalWrite(dir_cha, LOW);
}

void loop()
{
  analogWrite(pwm_cha, motor_speed);
  delay(2000);
  analogWrite(pwm_cha, 0);
  delay(2000);
}

Please give ideas on what I can do to solve this, thanks.


texts:
I tried to transmit "S" using De0 nano FPGA board and UART over USB module . The problem is i am not receiving "s" constantly . I am using the software Called Hterm to see receiving data.
When i remove the USB to UART module from the PC and reconnect the receiving value changes.

After removing the Module and plug it again the value changes.

And after this is received "S"


texts:
In a typical, simple solar power collector system (solar panels > battery > electric motor), what losses can be expected for a rated wattage of the panels to the charging of the battery?
If a panel is rated to provide 200W (ideal conditions considered) would there be any losses in the wiring to the battery, a few percent? Are there any other losses I should be aware of? (Ignoring the variability of sunshine & atmospherics)


texts:
I'm using a TUSB2046B hub connected to a raspberry pi zero.  The hub circuit looks like this:

There appears to be a 12MHz sine wave coming from the crystal (as counted by my scope) and 3.3V on the VCC, /EXTMEM and EEDATA pins.  If I connect a device to the Pi using a USB OTG micro-to-micro cable, lsusb shows the device.  But if I connect the hub shown in the diagram, it shows nothing.  And I don't see any signalling on the USBDM / USBDP lines when I inspect them with the scope.

Have I got something seriously wrong?  Is there some good reason it's not talking back to me?


texts: Increase rotational velocity of synchronous motor

texts:
I recently got my hands on a Philips PM8110 (a single pen recorder which is basically an analog printer for voltages) which sadly provides paper with a velocity of 8 cm/hour. Although this would be ideal for measuring temperatures of the environment, it's not really efficient for what I want to use it for (toying around with it since this is an old inefficient technology but I just love the device). Now, I figured out that the paper supply is driven by a synchronous motor which, when supplied with a 50 Hz 100 V signal (supplied from wall via transformer) rotates once per hour.

Since I want to increase the paper speed to around 8 cm/min, I would need to supply the synchronous motor with a 3000 Hz signal [a high accuracy is not really required].

Question 1: Not looking at how to obtain this signal yet, is this even a possible method? Can the synchronous motor even handle such a huge increase in frequency?

Question 2: Suppose the answer to question 1 is yes, how can I multiply the incoming frequency by 60 (or about, so it might become x64 if multipliers would be used). Is there an IC for this? In the ideal situation, I would like to keep this motor (since it's the original) and with a switch, switch between the original 8 cm/hour to a side with a potentiometer for a variable paper speed. I looked on the internet of course but could not find a definitive answer on whether or not there is actually a really simple, small, realizable method.

I guess that if the answer to question 1 is 'no', I would have to search for another motor with the desired rotational velocity (whether this would still be a synchronous motor or not) and install it in the device which, as mentioned previously, is not preferred. Any other methods or some inspiration is also really appreciated.

I would love to get some insight into this,


texts: Varying resistance on same types of capacitors

texts:
Just tried to troubleshoot the following pcb

I am checking the capacitors first, none of them have any marks of them so I'm using my multimeter to check their resistance.
(I've checked online and found at least one site that says they can be tested by checking the resistance, however I found other sites that say they simply can't be tested using a standard multimeter.)

When reading the resistance of the top 4 capacitors, the leftmost three have the same reading; 18.73kΩ, however the last one reads 2.2kΩ. They all have the same markings on them, so I assumed the readings should be consistent.

Does this mean this capacitor needs replacing, or am I barking up the wrong tree?

Thanks.


texts:
What is the significance of these floating capacitors in this schematic ?
This schematic is created by Great Scott and is available here, http://www.instructables.com/id/DIY-Wireless-Energy-Transfer-System/


texts: Choose precision current source mosfet and opamp

texts:
I am working on simple precision current source figure below, I need figure out how to choose correct Opamp and Mosfet to have most accurate result (Linear).

So how do I calculate (or choose) Opamp and Mosfet requirement , to be able to get 1nA to 1uA.

 Green Is current and Red is input voltage

The R1 value could be change (Iout = Vin/R1) but I am more interested on linearity and choosing correct Opamp and Mosfet.

Vin = 0-3V variable (From DAC)


texts:
I have instantiated a block RAM module using Block Memory Generator segment of the Xilinx IP Core. Alternatively, I have coded my own simple single-port RAM module, much like on page 33 of these lecture slides (http://www-inst.eecs.berkeley.edu/~cs150/fa11/agenda/lec/lec10-sram1.pdf).

With each clock tick, I'm constantly updating the address and simultaneously writing to that block of my RAM module. Like this:

reg [5:0] address;
initial address = 6'b0;
always @(posedge clk)
begin
    address <= address + 1'b1;
end

block_ram uut (
    .clk(clk),
    .write_en(write_en),
    .address(address),
    .datain(datain),
    .dataout(dataout)
);

After populating the appropriate RAM addresses, what I would like to do is read back specific addresses and concatenate them together to make one larger wire, like so:

wire [624:0] concatenated_ram;
assign concatenated_ram = {ram[0], ram[1], ram[2], ram[3], ...}

The only way I can conceptualize this is by assigning the singular 'dataout' port of my RAM to a different wire depending on the address:

always @(*)
begin
    case (address)
        0: dataout1 <= dataout_from_RAM;
        1: dataout2 <= dataout_from_RAM;
        2: dataout3 <= dataout_from_RAM;
        ...
    endcase
end

Can anyone think of other options? Using a case statement to grab the data doesn't seem that efficient to me.

Thanks for any assistance in advance!!


texts: Relationship between switching pattern and the harmonics generated

texts:
Is there any relationship between the switching pattern of a power converter and the harmonics generated (amplitude & phase) ?

i want to predict the generated harmonics based on the switching pattern.

NB : i need also any kind of documentation about that topic


texts:
Is there any rule on how to choose the power rating of a bi-directional TVS diode which will be used in automotive 12V system as an ESD protection?

They range from 20-40W all the way to 1000W and more, how to choose the right one?


texts: Performance comparison of dual core and quad core processors with same TDP

texts:
Athlon X2 340 (dual core) and Athlon X4 740 (quad core) from AMD have same architecture and both have same TDP (65W).  They also have roughly similar frequency.  Does this means that at full load, the quad core processor is more efficient in calculations/watt than the dual core processor?

I know that TDP is not max power consumption.  For the above processors, at peak load, I would expect dual core to use roughly half the power to that of a quad core, but doesn't the same TDP mean that the dual core and the quad core processors will have similar power consumption at peak load?


texts: Is this fuse on a mains switch adequate?

texts:
Given this diagram for a section of a mains circuit (seems like there's no varistor symbol) -

simulate this circuit – Schematic created using CircuitLab

I gather that it's important for this fuse to be present if the MOV short-fails. The fuse "time current characteristic curve", which I assume indicates when the fuse blows given a certain current and time:

It seems the "rated" current is not the melt current, but rather the current that the system is expected to typically draw; and that the melt current is much higher, dependent on time applied.

Are the circuit values appropriate? Is this compatible with residential mains?

Edit: I had been considering a PPTC fuse, but that idea was somewhat dead-on-arrival. To accommodate an AC motor with a startup surge potentially above 4A, the PPTC options are very limited, bulky, slow-acting and expensive. In comparison, filament fuses seem cheap, abundant and fast-acting.


texts: Correct AC input wiring for electronic door lock PSU

texts: I have a small PSU that outputs 12v DC for use with electronic door locks, but I'm a bit uncertain about the AC input. From the diagram it looks like there is two AC live wires, and a single earth. Does this mean I can use either red wire for the neutral? Ie, Live (1), Neutral (2), Earth (3)? Or is this circuit not earthed (!) and neutral is the green/yellow pin (3)?


texts: How to calculate the cutoff frequency for this low pass filter?

texts:
I have to calculate the cutoff frequency for this low pass active filter.
I know the formula is:
$$ f=\frac{1}{2\pi \sqrt{R_1R_2C_1C_2} }$$
I don't really know if I should multiply it by 2 since there are 2 stages.


texts:
I am working on a project, which is to make a PID based line follower but the constraints are:

5 IR sensors are allowed
Only 9V battery
No microcontroller, only discrete components

I though of input block, which takes input from IR sensor and converts it to analog signal, which is then fed into a PID controller.
For DAC I am using a R-2R ladder DAC.
Can anyone please suggest an alternative to using relays as used here.
My control signal will have 5V.


texts: Building analog representation out of digital lines in PulseView

texts:
I am not sure if I am posting this in the right forum so if not, please let me know so I'll can post it somewhere else.

I want to monitor an analog signal but I only have a logic analyser at home, so I want to deconstruct it using an ADC in order for my analyser to read it. The software I use is PulseView and I want to combine my 8 digital signals in one analog one.

I know that PulseView has several decoders but I didn't found any that could help me for that task.

If you need more information to help me or any tips where I should post this, let me know and I'll be happy to modify my question.

Thanks


texts: Altium Draftsman Error: "Object reference not set to an instance of an object"

texts:
I am trying to create a Draftsman template that includes the parameter names, view locations, etc already built-in. This way when I set the Draftsman drawing template, the views are automatically populated. Altium claims this can be done by editing the DwfDot template file. I created a drawing based on an actual board and set the locations of all the views, and also created the parameters I wanted. I then saved the file as a DwfDot. When I set the template of the Draftsman document for a different board, the views are populated as expected but the parameters have problems. Some of the parameters don't "stick" (I set them but when I close the parameter dialog they are automatically cleared). I re-opened the DwfDot template file for editing and now when I try to edit the parameters I get the error "Object reference not set to an instance of an object".

So at this point I'm stuck -- trying to add the value for the parameter in my actual drawing does not work as it automatically clears when I exit the parameters window, and I am unable to edit the template because of the object reference error. What is the cause of this error, and how might it be resolved?

EDIT:

I managed to solve the problem with the parameters being automatically cleared. It turns out I had some parameter names in my document that matched the names of some of the project parameters. When I added the parameter to the project options parameter dialog, the field in the Draftsman document filled in. To combat this issue I simply prefaced all document parameter names (that I only wanted visible in the Draftsman documents) with "Doc" and adjusted the document parameters to reflect the change. For example, "Title" is a system project parameter, and I had a document-specific "Title" parameter. The system project parameter was overriding the value I placed in the document "Title" parameter. I changed the Draftsman template so that instead of showing "=Title" it now shows "=DocTitle", and added "DocTitle" as a document parameter, and this is working perfectly. Unfortunately the other issue I mentioned still exists, and that is I can't seem to clear parameters in the template created from another document.


texts: Need to Identify the Part Below , Try to search & Read Catalogs but still can not Identify it. W267J Need to replace it What is the Model Number?


texts: Using two DC Voltage Doublers in series to Quadruple the voltage?

texts:
Are there any unexpected dangers or hurdles in using two capacitive voltage doublers in series to quadruple a DC voltage? The DC voltage originates from a LiPo battery and is then injected into the body as part of a biomedical device. The required current to go through the body is only 1mA, but you need a higher voltage to get there (6 to 12V).

Is this a better option than a boost converter in terms of cost? I am not sure efficiency is a factor here, since the device uses such a small amount of current and only needs to last for a few hours. Thanks.


texts:
I'm a hobbyist/newby and I buy some items to build a cheap nichrome wire heater.First I buy a 50feet of 22gauges nichrome wire. For 120V AC source , I need 8feet of this nichrome wire to get desired temperature and this consume near 13A. Second I buy a SCR voltage regulator to controle the heat of my wire. And recently I buy a two others items , one to keep a eye on volts with a analog voltage indicator (150V AC max) and another one for amps with a analog amps indicator (35A AC max).

I wire for testing purpose the SCR regulator to a AC motor and put the volts indicator in parallel. Everythings goes fine from here. But when come time to connect amps indicator , I don't what to do exactly with it. I rectifying the current with a diode before does in the amps indicator in series ... the needle stop to giggles but snaps really fast at the maximum ( 35A ) end. If I put a 0.15omhs resistor in parallel to the amps indicator , the needles move more slowly and stop at ~20A ... but with a Multimeters I know the true value is ~2A for now.

So there a way to connect correctly this kind of indicator ? I going in wrong way to find the good resistor ohms value until I get the good reading value ? No instructions come with the amps indicator.  Here is a shematic of what I'm doing with the diode and the resistor :


texts: Is kapton suitable for use as high voltage insulation?

texts: I need to solder together some wires which will eventually run at about five kV, and I'm trying to figure out the best way to insulate the exposed leads.  Heat shrink (my usual go-to) is apparently not rated above about 600 V.  Kapton seems to be rated much higher (100's of kV/mm), so I am thinking of wrapping the leads in several layers of this.  Given the high voltage hazard, I'm looking for advice: Would this be a good solution, or is there a better way?


texts: How do I calculate a PID controller gain for a certain damping coefficient?

texts:
I have a third order process and I have to design a PID controller by cancelling out the two most dominant poles of the process. The process transfer function is:

The controller is of the form, where Kc is the controller gain:

To cancel out the poles the controller becomes, this is multiplied by Kc:

Now I have to cascade the controller and the process and calculate the transfer function with feedback (negative feedback), the feedback gain is 4.
The problem is that I'm supposed to calculate the value of Kc using the standard second order transfer function, but that is not what I get, because of the feedback gain being 4 and not 1.


texts: Why my Battery Protection + Charging + Buck/Boost design doesn't work

texts:
Disclaimer: I am a total beginner in electronics, no professional degree whatsoever.

I have designed the below 1 cell Li-ion battery protection/charging/buck-boost circuit and I've also designed the PCB for it too.

See design detail in EasyEDA

I am really new in electronics and from what I can see after assembling the PCB:

The charging circuit seems to be working. I can connect a Li-po battery and it will charge to 4.2v following the charging curve. The Red and Green LEDs are lighting up correctly.
The Buck/Boost circuit doesn't work, and I have no idea why. The symptom is that when I connect the lab bench power supply and set it to 4.2V the output is 3.4V, but the output voltage seems to be dropping with the input voltage instead of staying on ~3.3V.

Related Datasheets for the design:

U1 Protection IC
Q1 Dual N-channel MOSFET
U2 Buck/Boost IC
U3 Charging IC (sorry this one is in Chinese)

Few things I can think of:

The Buck/Boost IC is too far away from the inductor?
I didn't properly solder the QFN10 3x3 converter?

A screenshot of the schematics is attached here, for PCB design please check the EasyEDA link.

Thanks everyone in advance!


texts:
I'm facing some problems with my log amp circuit. My configuration is this:

The "gain" function in case of ideal op-amp is:
$$V_{out} = -V_t \cdot  log\frac{V_{in}}{R1 \cdot I_{es}}$$
with \$I_{es}\$ saturation current at the emitter.

First plot:
(red fit excludes the first measures)

1) The log behaviour is good, but it's not similar to the predictions (cyan color) where the range for \$V_{out}\$ is of hundreds of millivolts.

2) Despite there's a good log behaviour, there's an exaggerated offset. I tried to consider the input bias current but it should just give me an error of +/- 1mv in \$V_{in}\$. And, if I'd like just to put to my data another offset to correct the first, how I should choose it?

Second plot:

3) With greater R1 = 470 kOhm, I've a like a linear increasing trend for low V. The reason could be that the transistor is not working in that range? How I can predict this?


texts: How to prevent voltage drop when a Motor turns on?

texts:
In my arduino project I have 2 motors connected to a 9V battery ,  Motor A is switched on and Motor B is switched off, when I turn on Motor B motor A's speed slows down and When I turn motor B off motor A speed is back to previous speed.

How to prevent this behavior ? , How to keep motors running at same speed no matter other motors on or off ,

The motor i am using

Please help. :) thanks :)


texts: A question about amplifying low level strain gauge voltages

texts:
I'm having difficulty in deciding about implementing an amplifier and whether I need it at all for a strain gauge. I never dealt with such situation before and would be very glad to have your opinions.

I will have the following strain_gauges: http://bridgetest.com/wp-content/uploads/ST350-Operations-Manual-v2.2.pdf

Here what I found so far as an amplifier topology:
http://www.linear.com/solutions/1183
In my case the output of the straingauge will be very low; in the order of 1mV.

But there is a possibility I might use this device: http://www.microstrain.com/wireless/v-link-200
Im not so familiar with terminology in datasheet much.

Do you think I would still need to implement the LT’s strain gauge amplifier if I buy this wireless device for these straingauges of 1mV level variation? I was wondering would noise be a problem at this signal level if I don't amplify.


texts: Difference between a series circuit or parallel circuit in power generation?

texts:
I wanted to know the difference between the induced-EMF and current, in a series circuit layout, vs a parallel circuit layout.

In a series the current would stay the same,however, the induced-EMF would increase? While as a parallel circuit is opposite to that? Same voltage while the current increases?


texts:
I am trying to to use I2C to communicate with a sensor. I have a 2.2k pull-up resistors to a 3.3V supply for my SDA/SCL. The microcontroller I am using is a PIC16F18324. In my tests I do not have the slave connected. Apparently, my SDA line is being pulled low by the microcontroller and I am unable to transmit any data through the lines.

Here are two references I have been using:
https://www.8051projects.net/wiki/I2C_Implementation_on_PIC
https://electrosome.com/i2c-pic-microcontroller-mplab-xc8/

#include <xc.h>
#include <stdint.h>
#include <stdbool.h>

#define _XTAL_FREQ  4000000 //4 Mhz

uint16_t count = 0;

void I2C_Master_Init(const unsigned long c)
{
    TRISC = 1; // Enable TrisC RC0-SCL/RC1-SDA

    SSP1STAT |= 0b10000000;
    SSP1CON1 = 0b00101000; //Configure for master mode
    SSP1CON2 = 0b00000000;
    SSPADD = (_XTAL_FREQ/(4*c))-1;
}

void I2C_Master_Wait()
{
  while ((SSP1STAT & 0b00000100) || (SSP1CON2 & 0x00011111)); //Check if busy
}

void I2C_Master_Start()
{
  //I2C_Master_Wait();
  SEN = 1;             //Initiate start condition
  while(SEN);
}

void I2C_Master_RepeatedStart()
{
  //I2C_Master_Wait();
  RSEN = 1;           //Initiate repeated start condition
  while(RSEN);
}

void I2C_Master_Stop()
{
  //I2C_Master_Wait();
  PEN = 1;           //Initiate stop condition
  while(PEN);
}

void I2C_Master_Write(unsigned data)
{

  SSP1BUF = data;         //Write data to SSP1BUF
  while(BF);
  I2C_Master_Wait();
}

unsigned short I2C_Master_Read(unsigned short a)
{
  unsigned short temp;
  RCEN = 1;
  while(!BF);
  temp = SSP1BUF;      //Read data from SSP1BUF
  I2C_Master_Wait();
  ACKDT = (a)?0:1;    //Acknowledge bit
  ACKEN = 1;          //Acknowledge sequence
  return temp;
}

void main(void)
{
    OSCCON1 = 0x60; // HFINTOSC   Higher, faster
    OSCFRQ = 0x03;  // HFFRQ 4_MHz; Enables 4Mhz for Register HFINTOSC

    I2C_Master_Init(100000); //Initialize I2C Master w/ 100Khz Clock

    while (1)
    {
        I2C_Master_Start();         //Start condition
        I2C_Master_Write(0x05);     //7 bit address + Write
        I2C_Master_Write(0xFF);     //Write data
        I2C_Master_Stop();          //Stop condition
        __delay_ms(200);

    }
}


texts: Common mode inductance of a three-phase reactor

texts: I have designed a three-phase differential mode reactor on a 5-legged core.  I am trying to calculate the common mode inductance of this reactor.  Does anyone know how to do this?


texts: How to find coupling and decoupling capacitor values?

texts: I am trying to learn receiver design, one thing I noticed is the use of coupling capacitors and decoupling capacitors and incuctors. There were set of standard values such as 100 pF, 1000 pF or 0.1 uF (at decoup). My doubt is how do we choose those values exactly? I have asked few and they tell about the formula XC=1/2*PIFC but even if I am using that formula, how to know the value of Xc? For example consider I am working on 1 GHz, now how to calculate those values?


texts: Where will the grid-tie power go if it's not connected to the grid?

texts:
What will happen to the extra power that the grid-tie inverter is producing if the demand is less than what the load needs?

I have this planned system that I will be implementing soon. The good thing about connecting the solar panel to the grid-tie inverter is that there is already a built-in MPPT in it, eliminating the need for a solar charge controller. However, I am a bit concerned on what will happen to the extra power that the grid-tie inverter is putting to the system if I am disconnected to the grid e.g. black out and I'm using my off-grid inverter to power my house.


texts: Does coiling and straightening a wire change its resistance?

texts:
I’m looking to make my own kiln coils and I wanted to know

why are the coils coiled?
When the coils are stretched too far apart they run cold and when they are close together they run hot. What is the reason for this if resistance doesn’t change whether a wire is coiled or straight?


texts:
I've got a 4 digit green 7 segment display (technically 5, it's from a microwave and the "5th" digit is the function lights on the top and bottom). I don't have a datasheet for it. It's common cathode, the first 2 and last 2 cathodes control the digits and the middle controls the function lights. I'd like to figure out an ideal driving current so I can drive it from an Arduino safely. If I assume that each segment takes, say, 10mA, then if that segment on all "5" digits is lit, then the arduino is sourcing 50mA of current through a single pin, more than the recommended max of 40mA. Rather than just settle for no more than 8mA for a total of no more than 40mA, I'd like to actually do some math. I'm driving the display with a buck regulator set to 2.2V for testing

Now, my multimeter sucks. It's one of those free pieces of crap from harbor freight. I like it because it's free and I can abuse (and break) it without really caring because I can get another, but I hate it because it's SO inconsistent with small measurements. It has a 20mA, 200mA and 10A current setting. If I set it to the 10A setting, the maximum resolution it has is tens of mA, and it goes between .01 and .02A. If I change it to the 200mA setting, it says 5.6mA, and on the 20mA setting it says 4.8mA. This is frustrating, so I tried reading the current by converting it to a voltage across a resistor. I used a 100 ohm / .1% resistor, put it in series and connected the black lead from the DMM to ground and the red lead between the LED and the resistor, and read the voltage in millivolts. I got 130mV. So, ohms law: $$\frac{.130mV}{100Ω} = .0013mA$$ ...1.3mA?! I can understand the crappy multimeter being bad at measuring current, but it's usually spot on with voltages, which it why I did it like this. I can't understand getting that many different measurements though.

So, my question is two-fold. First, did I do the ohm's law measurements right, or was there something I missed? Second, given that I don't have a constant current LED driver, nor do I have a way of making one right now, how would you recommend I accurately measure the current of these LEDs? I will be driving it from the arduino directly, so I'll be using resistors. And please, be nice. I don't have a lot of money for things, which is why I have a crappy free multimeter instead of a better, more expensive one.


texts: Do I need to connect the vias of a shield to a net(the ground layer)? Or do just through-hole vias act as a shield? I have stitching as well that obviously connects to the ground layer but I wasn't sure about shielding.


texts:
We are trying to design a PCB antenna for wifi application. This is a verified PCB antenna design for 2.4 GHz band from texas instruments.

Their PCB's stack up is like this:

--------- 15 um copper layer

1.47 mm substrate FR4 with 4.2 Dielectric coefficient

--------- 15 um copper layer

when I simulate this exact design in HFSS with exact PCB model of TI's, it gives fine results. s11 has a down peak at 2.45 GHz and VSWR is below 1.2 between 2.38 and 2.52 GHz.

However, when I use the same antenna design with our PCB stack-up:

--------- 18 um copper layer

0.87 mm FR4 with 3.95 Dielectric coefficient

--------- 18 um copper layer

the center frequency of the antenna shift very much above 2.7 GHz.  Of course I figured it is related to difference in substrate height and dielectric propoerty but I don't know how should I modify this. I feel like I have to decrease the width of the lines somehow, so I did. But it did not wok, infact, it shifted the center frequency to 2.8 GHz. Can you suggest me some intuitive approach to modify this antenna so I can use it in my wifi application? I would not ask this if I have much time but I don't. I need to figure it out in a week I guess.


texts: What is "x Us" in a contactor coil specification?

texts:
I have a data sheet that gives the coil pickup voltage as "0.85…1.1 x Us] and coil dropout voltage as "0.3…0.6 x Us".

I am assuming that Us refers to the nominal or specified coil voltage, but why is it "Us"?

Thanks


texts: Measuring voltage from automotive PWM dimmer circuit

texts:
I am building a gauge to replace another in my instrument cluster. I am adding some LEDs and an OLED screen and I would like them to have adjustable dim with the old incandescent backlight bulbs. I plan on using a voltage divider and low pass filter, as well as averaging the ADC value to compensate for voltage swings as the alternator, alternates? (programmed to vary voltage pretty widely in operation)

My car has a low side switch for controlling the dimming, that is all bulbs are directly connected to the +12V headlight/indicator relay/fuse, all then go to the dimmer switch which has an oscillator and some sort of switch, also powered by the +12V from indicator fuse.

If I am not mistaken, if I measure the lead before the PWM switch and pass it through a low pass filter I should get a voltage, right? If the dimmer is at minimum pulse width, minimum brightness, I would expect to read nearly 12V, and if the dimmer was at full brightness I would expect to read much lower voltage, pretty much the resistance of the PWM switch times total circuit current? (was also hoping to use this ADC to detect when the headlights are on!)

I have attached a schematic of my dimmer circuit. The wire I think I should measure is GY/R

Thank you in advance for any advice!

Edit: I went ahead and measured the frequency and duty cycle of the dimmer, it varies from 60Hz 1%DC at minimum dim, and maxes out at 100hz and 80%DC.

I am trying to cram this all in place of a factory gauge, I can't really fit any easily available opamps. Instead, I plan on using a rail to rail opamp.

Here is my proposed schematic, the response time is slow, but not so slow to be unmanageable for this application. The high impedance of the divider circuit and opamp input should keep any ground leakage to a minimum when the lights are fully dimmed. The divider is set for a maximum of 14.7, and I plan on letting the opamp manage any extra overvoltage from there. The divider circuit and RC should limit current to a level the internal clamp diodes should handle.

Thank you for the advise!


texts: Feasibility of very high temperature ac-dc switching power supply

texts:
I'm involved in a product design (on the mechanical side, to be clear that I'm not an EE) where we need a very compact ac-dc switching power supply that will take 90-300vac, 50-60hz and output 5 watts at 12 volts. From a mechanical engineering perspective, it would be extremely advantageous if this power supply could deliver this power while operating for extended periods of time (many hours) at up to 105 °C ambient air temperature.

Just to make this more challenging our module would need to fit into a space about 15mm high, 25mm wide, and around 50mm long—so a really tight fit. The supply will need to be certified, so details like isolation (3000VAC) and noise that would effect wifi and Bluetooth radios needs to be controlled.

What I would like to know is what kind of considerations would go into whether designing such a power supply is feasible? For example, my limited understanding is that the capacitors are usually the components that limited temperature rating and reliability, but it also seems like there has been significant advancement in high-temperature ceramic and tantalum capacitors that would make such a power supply feasible today (although perhaps relative expensive).

Thank you in advance for any perspective you can provide.


texts: Why is this derivation of Schmitt trigger circuit's output signal, incorrect?

texts:
This is the reference Schmitt trigger circuit. Using KVL, \$V_x\$ turns out to be \$\frac{R_1}{R_1+R_2}V_o\$. Also,
$$V_o = A\left( V_x - V_i\right)$$
$$V_o = A\left( \frac{R_1}{R_1+R_2}V_o - V_i\right)$$
$$\left( \frac{R_1}{R_1+R_2} - {1\over A}\right)V_o = V_i$$
$$V_o = \frac{V_i}{\left( \frac{R_1}{R_1+R_2} - {1\over A}\right)}$$
Since A is a very large number, \$\frac{1}{A} \to 0\$
$$V_o = \frac{V_i}{\left( \frac{R_1}{R_1+R_2}\right)} = \frac{R_1+R_2}{R_1}V_i$$
If \$R_1=R_2=1k\Omega, A=2\times 10^5, V_i=2\sin\left( \omega t\right) V, V_{cc}=3V\text{ and }V_{EE}=3V\$, then the graph would look like this (according to the above formulation),

A rough representation of input and output signals
In reality the output signal is completely different. I know how OP-Amp with positive feedback work. But I am just curious as to why the above derivation is incorrect. Particularly which step.


texts:
I have some questions regarding TEC.

What if, I operate TEC without any cooling fan both side. In this condition for how much time it can run.
What if, I operate TEC with one cooling fan at cold side and other side is heatsink only.
How can I get 0 degree temperature continuously using PWM or other temperature controller device.

Br//
Deepak


texts: Need help identifying AC power connector

texts:
I picked up this (rather unique?) Tektronix spot welder at a sale a couple weeks ago. I haven't figured out whether it needs 120V or 220V service, and it didn't come with a power cord. The power should come through this male socket in the photograph.

Let me know if further details are needed. Thanks!
Edits:
- added front panel image. M


texts:
I have a small signal Vs at the input and I want small signal -Vs at the output using an inverter. How can I do it?

simulate this circuit – Schematic created using CircuitLab

This is the circuit of the inverter and It has a small signal Vout= -gmRVs
where gm is the gain. If I can put R=1/gm, I get the output I want. But, that doesn't work in the circuit. Is there any other modification I can do to the circuit to get an inverting stage?

Thank you


texts: Altium - Use an existing component symbol for another component

texts: Altium designer (without vault) only comes with through hole components (resistor, capacitor) in the component library. I want to design SMD capacitors and resistors on my own but I want to reuse the schematic symbol of the default Altium components. How can I do that?


texts:
Is it possible to make text inside a shape on the silkscreen layer in Eagle? I'd like a white rectangle with text inside that's the color of the solder mask.

(I see this post but not sure if I can do this with text?)


texts: are there differences in energy consumption for displaying color?

texts:
The question stems from wanting to design UI's for mobile devices that consume the least power.

I'm assuming a dimmer screen will consume less power..but would, for example, green use less power than red?

Or maybe it'd be best to stick to grayscale?


texts: How many PWM output channels does the Atmega4809 really have?

texts:
How many PWM outputs does the Atmega4809 really have? The Microchip site claims it has 8.

The datasheet for the Atmega4809 microcontroller is split up into two pdfs. This one is for the megaAVR family. It describes the timer configuration for generic timers used in PWM. This one describes a few specifics of the pin layout for the Atmega4809.

For PWM, the Atmega4809 has:

One 16-bit Timer/Counter type A with dedicated period register, three compare channels (TCA)
Four 16-bit Timer/Counter type B with input capture (TCB)
One 16-bit Real Time Counter (RTC) running from external crystal or internal RC oscillator

From what I understand, the one TCA timer has PWM 3 output channels and TCB timers each have only one output channel. That makes 7 PWM output channels. Does that mean the real-time counter (RTC) can be configured as a PWM output?


texts: How do you compute the DC operating point (IC,VCE) and draw an AC equivalent circuit?

texts:
I just started learning about electronics and decided to quickly sketch a circuit. When it comes to OP and changing the said circuit into an Ac equivalent, I got stuck.
Sorry in advance if this is considered a basic question.


texts:
I'm cracking my head at this problem, right now. It is the continuation of the work that I'm doing with this: Relation between group delay, pole frequency and quality factor.
So, as I said this is a Bessel second-order lowpass filter, with gain \$ K_0 = 0.5 \$ and gorup delay in the passband of \$ \tau_0 = 259 \mu s \$
$$T(s)=\frac{V_o(s)}{V_i(s)}=\frac{K_0\omega_0^2}{s^2+\frac{\omega_0}{Q_0}s+\omega_0^2}$$
Now I was supposed to design an LC low pass filter equally terminated and adapted to a load of \$600 \Omega \$.
I used a normalized table considered a normalization to the -3dB frequency of the filter (cutoff frequency) coming up with the following normalized filter:

Fantastic. Now I need to determine the cutoff frequency so that I can perform frequency scaling and impedance scaling
$$R \longrightarrow \alpha R_n$$
$$L \longrightarrow \frac{\alpha L_n}{\omega_{-3dB}}$$
$$C \longrightarrow \frac{C_n}{\alpha \omega_{-3dB}}$$
We already know that \$ \alpha=600 \$. Now for \$  \omega_{-3dB} \$.
Well we know the normalized frequency relates to the frequency like:
$$\Omega=\frac{\omega}{ \omega_{-3dB}}$$
Therefore:
$$\Omega_0=\frac{\omega_0}{ \omega_{-3dB}}$$
And using the conclusion from my last question that:
$$\tau_0=\frac{1}{Q_0\omega_0}$$
We arrive with:
$$\omega_{-3dB}=\frac{1}{\Omega_0 Q_0 \tau_0}$$
Nice! So now we need the values \$ \Omega_0 \$, \$ Q_0 \$, and \$ \tau_0 \$ is given.
From circuit analysis we come to:
$$T(s)= \frac{\frac{1}{L_nC_n}}{s^2+\left(\frac{1}{C_nR_{L_n}+\frac{R_{S_n}}{L_{1_n}}}\right)s+\frac{R_{L_n}+R_{S_n}}{R_{L_n}L_nC_n}}$$
Therefore we conclude that:
$$\Omega_0=\sqrt{\frac{R_{L_n}+R_{S_n}}{R_{L_n}L_nC_n}}=1.12702$$
$$Q_0=\Omega_0*\frac{1}{C_nR_{L_n}+\frac{R_{S_n}}{L_{1_n}}}=0.57735$$
We arrive to $$\omega_{-3dB}=5923.752705\text{ rad/s}$$
Which leads to the final circuit of:

Simulating this circuit I obtained a constant group delay of \$ \tau_0 = 229 \mu s \$, which has like 12% of error which I think is a fair enough result giving all the approximations we did in the calculations.

However the author of the problem for some reason considers \$ \tau_0 = 55 \mu s \$. Am I misinterpreting the group delay? Is there any extra calculation to arrive to this or is it a mistake?
We arrive to $$\omega_{-3dB}=24.757\text{ krad/s}$$
And the circuit:

Which indeed, simulating, we arrive with a constant group delay of like \$ \tau_0 = 57 \mu s \$.
But why? Is this a mistake from the author? This circuit is far off the original specifications unless I am actually not interpreting them correctly? Can someone help me to verify my work?

Original problem (in Portuguese):

Original Tables that I used and their context:


texts:
If I use the 74HC595 output shift register, and I don't use the latch pin, would it still work as shift register, like the 74HC164, that doesn't have that pin at all?
The shift register is going to be used to reduce the output pins needed to drive the colums on a switch (pushbutton) matrix.


texts: How to make use of Internal Oscillator in PIC16F676?

texts: Im a beginner in PIC and using PIC16F676 for making an LED blinking program. But every tutorial uses an external oscillator. I want to make use of the internal oscillator to do this, so can anyone guide?


texts: QUCS simulation of simple capacitor/resistor circuit - strange results.

texts:
Hi I have just started to learn electronics. In order to understand the RC constant I have built the following very simple circuit in QUCS simulator.

 According to the formula

RC time constant = R x C = 2,000,000 ohms x 0.000015 farads = 30 seconds

I would expect the graph of voltage on capacitor C1 rise steadily till it reaches 2/3 of 1.5 after 30 secs . However as it can be seen the the simulation shows straight graphs of both current and capacitor's voltage without any difference in time.

Can someone explain these results


texts: 7 segment led light up specific decimal point

texts:
I have a 12 pin 7 segment led (ATA8041AB) which is working fine using my code, it just that when I try to light up the decimal point led, it either light up all dp or dont light up at all.

here is my code

int segA = 3; // top
int segB = 4; // right-top
int segC = 5; // right-bottom
int segD = 6; // bottom
int segE = 7; // left-bottom
int segF = 8; // left-top
int segG = 9; // middle
int dp = 10;

int digit1 = 14; // common cathode for digit1 (i.e. sambung A0)
int digit2 = 15; // common cathode for digit2 (i.e. sambung A1)
int digit3 = 16; // common cathode for digit3 (i.e. sambung A2)
int digit4 = 17; // common cathode for digit4 (i.e. sambung A3)

// Number to display
static int number = 0;
static int ms = 0;
String inData;
int collectedNumber;

int   blinkRate=0;

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

    // All pins in digital mode
    pinMode(digit1, OUTPUT);
    pinMode(digit2, OUTPUT);
    pinMode(digit3, OUTPUT);
    pinMode(digit4, OUTPUT);

    pinMode(segA, OUTPUT);
    pinMode(segB, OUTPUT);
    pinMode(segC, OUTPUT);
    pinMode(segD, OUTPUT);
    pinMode(segE, OUTPUT);
    pinMode(segF, OUTPUT);
    pinMode(segG, OUTPUT);
    pinMode(dp, OUTPUT);

}

//==============================================================//
void loop() {

digitalWrite(dp, HIGH);

//as a test, aku letak nilai 9999 display dekat led

number = 4268;

    digitalWrite(digit1, LOW);
        // light on segments for 'thousands'
        drawDigitFast( (number/1000) % 10 );
        // wait 2 ms
        delay(2);
        // turn off all segments
        drawDigitFast( -1 );
    // turn off cathode for digit1
    digitalWrite(digit1, HIGH);

    digitalWrite(digit2, LOW);
        drawDigitFast( (number/100) % 10 );
        delay(2);
        drawDigitFast( -1 );
    digitalWrite(digit2, HIGH);

    digitalWrite(digit3, LOW);
        drawDigitFast( (number/10) % 10 );
        delay(2);
        drawDigitFast( -1 );
    digitalWrite(digit3, HIGH);

    digitalWrite(digit4, LOW);
        drawDigitFast( number % 10 );
        delay(2);
        drawDigitFast( -1 );
    digitalWrite(digit4, HIGH);

}

//-----------------------------------------------------//
void drawDigitFast(int n)
{
    const byte aPins[8] = {
        segA, segB, segC, segD, segE, segF, segG
    };
    const byte aSegments[11][8] = {
        //  A     B     C     D     E     F     G
        { HIGH, HIGH, HIGH, HIGH, HIGH, HIGH,  LOW }, // 0
        {  LOW, HIGH, HIGH,  LOW,  LOW,  LOW,  LOW }, // 1
        { HIGH, HIGH,  LOW, HIGH, HIGH,  LOW, HIGH }, // 2
        { HIGH, HIGH, HIGH, HIGH,  LOW,  LOW, HIGH }, // 3
        {  LOW, HIGH, HIGH,  LOW,  LOW, HIGH, HIGH }, // 4
        { HIGH,  LOW, HIGH, HIGH,  LOW, HIGH, HIGH }, // 5
        { HIGH,  LOW, HIGH, HIGH, HIGH, HIGH, HIGH }, // 6
        { HIGH, HIGH, HIGH,  LOW,  LOW,  LOW, LOW  }, // 7
        { HIGH, HIGH, HIGH, HIGH, HIGH, HIGH, HIGH }, // 8
        { HIGH, HIGH, HIGH, HIGH,  LOW, HIGH, HIGH }, // 9
        {  LOW,  LOW,  LOW,  LOW,  LOW,  LOW,  LOW }  // all off
    };

    if( n < 0 || n > 10 )
    {
        n = 10;
    }

    for( int i = 0; i < 7; i++ )
    {
        digitalWrite( aPins[i], aSegments[n][i] );
    }
}

what I'm trying to write is 4.268, but the best I could do is 4.2.6.8 . can help me please?


texts:
I'm about to layout the USB connection on our boards and wondering whether the termination resistors and pull-up on D+ are necessary when using the STM32F437xx. The datasheet tells:

No external termination series resistors are required on DP (D+) and DM (D-) pins
since the matching impedance is included in the embedded driver.

Concerning the pull-up resistor on D+ it is stated:

HNP/SNP/IP inside (no need for any external resistor)

However, all development boards I checked (Olimex STM32-H407 and ST STM32F4DISCOVERY & STM32439I-EVAL) seem to include at least the termination resistors of 22Ohms. The Pull-Up on D+ is not included.

For now, I will simply place the two resistors and go with it. Still, I would like to understand the reason why one would "double-terminate" the lines.


texts:
I'm seriously thinking about (practically committed to) taking one of my products through FCC and EC testing and it's my first time doing so. It's Arduino based electronics running off a 16MHz crystal with an Ethernet Controller running off a 25MHz crystal and an RFM12B 433 MHz radio module. The Radio Module, as far as I can tell, doesn't have an FCC ID, but they have published data on their website that suggest compliance to FCC part 15 requirements. Everything is pretty low power here, and I'll be using an US/EU approved wall-wart power supply to provide power to the board.

So what I'm worried about is what happens if my boards fail the tests? Best case is it passes and we move on, which would be great. But I'm really honestly terrified of what happens if it fails and I'm not sure how to fix it from an engineering standpoint? I've tested the boards various functionalities and it works great, I would really hate to have to go back to the drawing board especially given that I won't really know what changes might be made to fix it.

I don't have a specialized staff; it's basically just me. I'm producing open source hardware and software. Most people take the really conservative and pessimistic approach when answering questions like this are not really encouraging or supportive. Can anyone give me some insight into what to expect from this process, and constructive experience on how to get through this process and resolve the types of issues that might come up?

The whole thing just seems really unfriendly and forbidding to me. I know I'm not the only one out there who feels this way. I hope there are some community members who can shed light on it besides the usual gloom and doom perspective. Basically I want to be prepared for reality, but I want to know there is a light at the end of the tunnel too.


texts:
For homework I have to design a circuit which will take as input ultra violet light , it will convert it to an electric signal and then it will amplify it .Here is what I have done so far:

simulate this circuit – Schematic created using CircuitLab
Do I need to connect R1 to ground or not? Note that the VEE pin of the opamp is connected to ground.
This is what I think happens: When light is absorbed by the photodiode a voltage is created between the non inverting and the inverting pin.
In most of the projects I have seen the voltages in the inverting and in the non inverting pin of the opamp close loop with the ground and this doesn't close loop with the ground that is why I am asking if I need to connect it to R1 to GND.


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I just wanted to double check my understanding of the diagram as in my mind the "visual clues" related to the way the cap is drawn seem to contradict the actual instructions of the diagram.
If this capacitor only had 2 connectors on it  would it be correct to wire the neutral (black) terminal to the neutral (black) wire?
From a logical POV would I have a single connection joining neutral black, neutral terminal and capacitor to the 1 leg of the capacitor, and the capacitor/grey wire to the other leg?
Another, simpler way of asking this - should all the black wires be connected together on 1 terminal and the grey one on the other?
Assuming the aerator to be a standard single phase AC motor, if the connection is fused (and has an RCD on it), and if the wiring were round the wrong way, would turning the motor on simply trip the fuse or could it damage the motor or capacitor?

In the picture of the Capacitor below, the 2 lugs on the left are connected together and the 2 on the right.   (This looks to me to be 90 degrees to the way it has been drawn in the diagram)


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I have keypad with for buttons and common signal connected to ground..

I noticed two configuration for debouncing as shown bellow..

Question:
- Will the both configuration work correctly?
when button (pressed > Low) (released > High)
- How to select the pull-up resistor ( R1 - R4) and debouncing circuit (R5 - R8 / C1 - C4)?


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How much current does this read?
How much current is flowing here?


texts: Components needed to determine position in 3 dimensions?

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I'm trying to make a quadcopter using an arduino as a base. I've read on some physics involving determining pitch, yaw and roll and it seems like I'll need a gyroscope and a accelerometer. However, it's my understanding that this only gives me my orientation relative to a "flat" base (usually the ground). What type of component is needed to determine the elevation of the copter? Would a barometer work?

Is my understanding here correct or am I way off?


texts: Using a "Normal" powerbank for a "Super Fast Charging" phone, are there any potential damages?

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I have an Anker Redux 10000 mAh powerbank and a Samsung Note 10 Lite smartphone.

My powerbank is capable of providing an output of 5V ⎓ 2.4A, with only "normal" charging mode (no QuickCharge or other similar charging technologies). That would make its maximum power to be 5V x 2.4A = 12W.

My phone is equipped with Samsung's 25W "Super Fast Charging" capability. According to the information printed on the charger provided with the phone, this is the output specification (which is the one confusing me):

  (PDO) 5V ⎓ 3A or 9V ⎓ 2.77A (PPS) 3.3-5.9V ⎓ 3A or 3.3-11V ⎓ 2.25A

If I understand it correctly, my phone could be charged with a broad range of voltage-amperage values. According to the information printed on the charger, it can receive a wattage as low as 3.3V x 2.25A = 7.425W, which is well within the 12W capability of my powerbank.

So, if I use my powerbank to charge my phone, will I damage my phone or my powerbank or both? Also, am I understanding electricity correctly?


texts: What are some simple and informative beginners projects?

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I'm currently in an "Information Technology" program, and this program includes some electronics courses. So, I know a little bit about voltage sources, current sources, resistors, capacitors, inductors, operational amplifiers, basic first-order filters, and soon I should know a little bit about diodes and transistors.

In class, we hear some theory. In labs, we play with oscilloscopes. And these things are all fine and good, but I'd like to building something.

I'm tapping you fine folks for resources, simple and informative beginner's projects that will help me learn these topics more solidly. Start me with educative tutorials on blinking lights and finish with educative tutorials on line-following robots (or something like that). I'll emphasize that the recurring theme is 'educative'.

I want to make it clear that I do not come from an electronics background. (I just pretend like I do when I'm at school.)


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So I would like to design a device that allows me to send instructions to different devices (each containing a HC-06 Module). I would like to ask if it would be ideal to use a Bluetooth Mesh?
This is the Module I plan on getting:
https://www.silabs.com/products/wireless/bluetooth/bluetooth-low-energy-modules/bgm13p-bluetooth-module


texts: 3 volt string led light adapting to 5v usb charger source

texts: I would like to cut off the batteries, and light these 10 led string light with 5v usb. I dont know how much current flows throught them, and dont know what resistor should I use.  Please help. Im a newbie.


texts: How do I convert poles and zeros of a transfer function into a circuit / required circuit components?

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I have been given a Bode plot of a low pass filter, and tasked with essentially reversing the effects by using a high pass filter. I have solved for the transfer function which is the first equation, and I am assuming the inverse transfer function will give me the information I need to construct the high pass filter.
I know the values for \$z\$ and \$p\$.
Is there a method given any transfer function to realise the circuit elements required?
$$H(s) = 0.17\frac{s-z}{s-p}$$
$$H(s)^{-1} = 5.88\frac{s-p}{s-z}$$


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I wanted to switch an LED ON and OFF using a signal from an Arduino. The LED was a high power LED, which I choose to overdrive with 100 mA with voltage source of 12 V. Forward voltage drop of the LED is 4 V.

The switching was done using a BC547b transistor, which has an 2.5kohm resistance on its base leg to the Arduino pin. Base current is 100mA/200

I choose to use BC547b as it seems an all purpose transistor, but by further inspecting the transistor I saw that its collector Imax is rated to 200mA (good thing I didn't supply it with more than 12 V or designed the resistor not to pull more than 100mA).

Emitter was grounded.

But other than that I can see than efficiency-wise it uses "a lot" of power, it's not fully saturated... The transistor didn't exhibit that much heat? So I am not sure whether it is a good thing, or a bad thing.

But other than that, what parameters should I look into to choose the transistor to switch this form of circuit?

How can I choose, in general, an ideal transistor in relation to speed, power usage and handling of high frequent signals?

I know for certain that my Arduino pin output is 3.3 V (might be a fake model).  But that is for sure.

Circuit

Are my design choices optimal for this application?

R1 =  2500 ohm
R2 =  4 ohm.
V_c = 3.3 v
V_{cc} = 12 V


texts: How to approach diode circuit analysis (novice)

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In my microelectronics course we have just begun learning about diodes and semiconductor physics. We have been analyzing simple circuits with diodes, mostly solving for component values. The approach we have been taught is to simply "guess" how the circuit is behaving, running the math to see if it works out, and adjusting if necessary. For example, consider this circuit:

NOTE: I have already solved this question (I am not asking for homework help).

It turns out D1 is reverse biased and D2 is forward. I only found this out after testing two other assumptions (D1 and D2 both on, and D1 on/D2 off).

Are there any clues that indicate a certain assumption is more likely to be correct? I ask this because we are expected to solve these rather quickly - I know practice is the best, but I am hoping for some tips.


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I built a LM3915 (waiting for LM3916 to arrive) VU meter based on Sparkfun's tutorial.
The problem is, when I plug in the power, only the last LED (LED 10) lights up and LED9 kind of flickers. If I pull pin 9 of the LM3915 to HIGH (+5v) then all of the LEDs are lit up.
I'm providing input to pin 5 (SIGNAL) via 3.5mm audio jack. So I connected GND of the 3.5mm jack to the GND in the circuit, and tried the both the TIP of the 3.5mm jack and the RING. Nothing changes, always the same results.
So if there is anyone that might know whats up with this, it would be much appreciated.
Here is the picture of the problem:

Green wire is GND and the orange one is SIGNAL. As I said, connecting audio jack changes nothing, but for instance if I grab GND and Signal with my fingers, all of the LEDs light up for a short period of time.
Schematic:

This is the schematic from SFE and they way I hooked everything up.


texts: Microcontroller or arduino alternative for small cell-phone sized device?

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I am doing a project in which I need to read RGB values from a color sensor TCS230 and send it to a microcontroller and use an linear equation to get glucose value from it and display it on an LCD.As such this whole thing needs to be packaged into a cellphone sized device.The project needs to be completed in 2 1/2 months. The block diagram is as follows: Cant post image as new user.Anyway, Inputs:optical sensor(6pins),2 buttons(4 pins),sensor to test fit of glucose plug(2 pins).Output:LCD(16 pins). Microcontroller and power supply from battery. Total nearly 30 pins

My questions are:

I am using TCS230 as my optical sensor.I need to read from only 15mm2 at a distance of 1cm matte surface.I propose to use a concave lens to focus.Is this setup good or is there a better sensor I can use?
The device is cellphone-sized. So I thought of using arduino mini but I need 30 io pins where as mini has only 20. I could use a plain microcontroller. I know arduino prog but not avr prog.I did a course on microcontroller but assembly programming.*How hard is it for me to use a microcontroller.I need to complete this in 2 months.Is there any other option for me?Can I reduce LCD pins to fit mini?*Main concern is time arduino I know and can prog quickly but I do not know avr yet.The sensor outputs square waves whose freq gives rgb values.
Which microcontroller should I use?
What type of battery to use Li-ion ?How should I decide on batterygiven size considerations?
*What LCD can I use?*I need to display letters and numbers and it needs to be small-size of cellphone screen.