texts: Replacing a hard to get BGA part with a small circuit board?

texts:
We have a production design PCB with suddenly hard to source BGA part. It could be replaced with a much easier to source device, but we'd prefer not to go back to layout and redo/reverify the board and so on.
So my crazy idea is to make a small PCB with the new part on top, and create a BGA array on the solder side that is compatible with the old part. Since BGA parts are actually not that challenging of a tolerance I figure this could be done if I can source a small container of BGA sized solderballs, and stick them on the new module, then reflow the board with the PCB module instead of the hard to get BGA part.
The whole idea needs to cost less than redoing the board design of course..
A few minutes with Google got me nothing but hobbyists trying to solder BGA parts at home..
Any PCB fab services out there doing this sort of thing, other than the IC manufacturers themselves?


texts:
My teacher of Electronic Instrumentation's course presented me on an exam the following problem:
\$\hskip{75pt}\$

a) What is the importance of making the parallel between \$N7\$ and \$N8\$ logic ports for this circuit?
b) What is the effective tension applied on the emissor of the circuit if this is stimulated by a simetric PWM (duty cycle=50%)?

I'm studying Physical Engineering, and I never heard about this, even on the classes of the course. After the exam my teacher said that, putting two inverters in parallel reduces the impedance for half, which duplicates the current to the emissor, which also duplicates the power. I know that this characteristic is analog to the parallel of two resistances of the same value. My problem is how to visualize this. Inverter ports are too complex to be compared to resistances.
How would you  answer those questions?


texts:
How to measure the power consumed by a temperature sensor theoretically?

The datasheets mention the supply voltage range and output current.
So, to calculate the power supply current will be used in P=VI. The supply current is not mentioned in the datasheets. What is the way to calculate this value?

The supply current will depend on the resistance.

The datasheets mention a number of thermal resistance value. Is there any relation between these resistance values?
and will this information help in finding out the power consumed?
If the temperature sensor is being used for continuous monitoring, does the power consumption vary?


texts: I have ~26 parallel inputs that I would like serialize and send to a computer over USB. I decided to chain together 4 LS165 parallel-in serial-out shift registers, but I don't know how I would send this serial signal over USB. I considered using an FTDI FT232RL, but I'm not sure how I would make my serial signal into UART. I would like to avoid using a microcontroller in the middle if possible, but I will if it will make my life easier. Is there a simple way to take this basic serial stream and send it over USB?


texts: Can anyone identify this component? (possibly counter)

texts:
I recently acquired this device, and I have no idea what it does, or how it works (or how to make it work). The guy who I got the device from told me that it was some kind of counter, but he could not tell me much more. Trying to figgure this one out has taken me the better part of the day, and I need some help please.

The device displays two small diamonds on the lcd display when you rub the middle contact. It also clicks when you shake it. The contacts look like some kind of rubber or fabric with embedded metal. The device is encased in plexiglass, and does not appear that it is open-able. The writing on the device is:

056 (in white screen print on bottom left)
MB0956 REV X (Possibly
MBO956, on bottom right)
hy (appears to be a logo, on middle right)
9440 (under hy)
hy-212 (under 9440)

Pictures of the device are shown below.


texts: Sample application for generating energy from Piezeo Electric Crystal.?

texts: I am working on a project where I need to prove that Piezeo electric crystal can help us to generate electricity and can be applicable on streets.My question is that where can I find suitable transcendence or Piezeo electric energy generating unit.I would also like to know if such things are already implemented. I am also seeking for proper elements to make this things happen. Since I live in India the local markets are really poor having such sophisticated equipment. I would also like to know if I could order the parts online. All suggestions are welcomed.Thanks


texts: How do I implement the clock into this testbench?

texts:
I am trying to write a testbench for an adder/subtractor but when it compiles the clock does not shift.

Here is the verilog for the adder/subtractor:

module adder_sub(

input [7:0] dataa,
input [7:0] datab,
input add_sub,
                        // if this is 1, add; else subtract
input clk,

output reg [8:0] result);

    always @ (posedge clk)
        begin
            if (add_sub)
                result <= dataa + datab;
            else
                result <= dataa - datab;
        end

endmodule

And here the code for the testbench:

module adder_sub_tb;

    reg[7:0]dataa;
    reg[7:0]datab;
    reg add_sub;
    reg clk;
    wire[8:0]result;

    adder_sub dut (.dataa(dataa), .datab(datab), .add_sub(add_sub), .clk(clk), .result(result));

    initial begin
    dataa <= 8'b00000000;
    datab <= 8'b111111111;
    end

    always@(clk) begin
        clk = 1;
        #20;
        clk = 0;
        #20;
    end

    always @(posedge clk) begin

    repeat(16) begin
        add_sub = 1'b0;
            $display(result);
        #10;

        add_sub = 1'b1;
            $display(result);
        #10;

        dataa = dataa + 1'b1;
        datab = datab - 1'b1;

        end
        end

        endmodule

This compiles just fine, but in the simulation clock does not change at all and I don't know how to fix it. I tried nesting always loops but that is a big no no, as I've learned.

Additionally, I am trying to do is get the dataa and datab waves to change which in turn changes result, but I would also like to see the result ticking with $display but I don't know where that outputs to. I am using modelsim-altera as my simulation tool and quartus prime lite for verilog.

Thank you


texts: How is air conditioner room unit fan motor controlled?

texts:
I have a custom project where I need to control fan speed with Raspberry Pi according to data it gets from various sensors. At first I need to know what my motor needs. For fans I use old air conditioner internal (room) modules. Electronic part is faulty, but motor works fine and would perfectly suit my needs. Only, if I could control its speed.

My motor is Guangdong Welling Motor Manufacturing CO model is RPG20E. Wiring diagram looks similar to many other air conditioner motors.

Currently I do not pay attention on FG part of the diagram as I found it is just a tachometer.

A person here has pretty much the same question as I, but not a clear answer on that tread.

I decided to experiment and risk blowing one motor to see what it does if I just give it 230 Volts. Well, nothing exciting – fan started to rotate at low speed. I looked at original control board that was inside air conditioning unit and found a capacitor that is mentioned in diagram. I soldered it out and connected to motor as required. Fan started to blow at its full speed. Removing a cap slowed down fan speed, but amperage did not really change. So, a capacitor must be always there. Didn’t check motor temperature at that point.

Next test was to use just a regular resistive light dimmer that gave me an option to reduce voltage for the motor. Results were exactly what I needed. Motor slowed down according to resistor position. At around 80 Volts motor stopped completely. Regulating the voltage from 110 to 230 gave nice and smooth speed control.

I thought at the beginning that this is what I need, just to regulate voltage with my Raspberry via some extra module, but I recalled, that to control the speed of AC motor can be changed by changing the frequency. I searched the internet to find out how I achieved my goal without changing any frequency. I have been surfing the net for this topic for a week now and found way too many opposite opinions. I fount that lowering voltage by resistor is possible, but that will burn the motor as it will draw higher current. My measurements did not show me significant rise in current and motor temperature was fine at low speeds with low voltage. And as I found many fan controllers use similar controller, some have capacitors instead of resistors, some have both.

Perhaps this AC motor works differently? How did the original controller (that was in AC internal unit) control motor’s speed? Did it use resistors to lower voltage, changes frequency or used some electronics called TRIAC?

By the way, I found a datasheet for another AC motor from Wellington. Where it states for voltage range 190-254V. So this means that it could be ok to control the speed just by adjusting the voltage.

Before I build my prototype, I would know for sure what would be the proper way to control the speed of this particular motor without burning down the motor or the whole facility.

Any help is appreciated.


texts: Wiring a Key Switch to Control USB Power?

texts:
So I'm working on a project, and I'm a bit stumped on this problem I ran into. Brief explanation, I have wired a key switch into the power pin of a USB extension cable, which will allow the female end to be toggled on/off depending on the key position.

My problem is that this specific switch has a .7 ohm resistance. My initial solution was to solder a button cell battery to the cable to provide the extra volts. My question is whether or not supplying more than the 5 volts expected from the USB port will damage either the port or the device on the receiving end (I'm using a USB drive, and the .7 ohms prevents readability of the drive).


texts: Do these SSR terminals have a specific name?

texts: Right now I examine some SSRs, and most of the samples I have are equipped with these metal "pads", with screws with square washers to squeeze the cable. I know it sounds silly to ask their name, but if they do have a name & are commercially available products it would be appreciated, because then I will be able to prepare a prototype of a product without having to manufacture these parts.


texts: Long term reliability of addressable RGB LED strips? How do WS2812B, APA102, and SK6812 compare?

texts:
I'm about to order a lot of RGB LED strips for a project that will hopefully be running for years if not decades.

I used to have very good luck with strips using the WS2812B chips, but in recent years the quality seems to have dropped significantly. A recent batch had a failure rate of about 1 in 1,000 after 100 hour burn-in, whereas old batches had effectively no failures even after running for several years. I assume this is due to the availability of knock-off chips now that the WS2812B's have become so popular.

Has anyone had any long term experience with running very large scale installations of these strips?

Any advice on which chip line is least likely to have failures?

Any advice on finding suppliers who use genuine article chips rather than knock-offs?


texts: Slow down stepper motor's speed using stepper driver DRV 8825

texts:
I've got a Nema 17, rated at 0.8Amps, stepping angle of 1.8 degrees.

The motor looks like this, and has six wires coming out of it:

The four wires I've used are the ones labeled below (I was instructed to use everything except the black and the white one by my seller):

My current wiring:

Both the A+ and B+ wires are connected to A1 and B1 respectively. Likewise, A- and B- are connected to A2 and B2 respectively.

I'm trying to use this motor with an Arduino Uno and a Polulu DRV 8825 driver. The power supplied to the motor is 12V, 500mA via the stepper driver.

I drive the stepper driver with two wires (one for the step, one for the direction). All my wiring is verified to be correct.

I'm trying to use this motor for my camera slider, but with no luck.

The problem

I want to achieve some really slow, yet smooth rotation with my stepper, but am unable to do so. Ideally, I'd like to reach speeds as low as shown in this youtube video.

When I try to vary the speed of the stepper speed through my code, it only marginally reduces in speed (definitely not as slow as I would like), and even when it does, there are a lot of vibrations at those particular speeds. However, there is only a (small) range of speeds wherein the motor is quiet. I'm afraid these vibrations may make my slider setup completely unusable.

Gearing isn't really an option either, due to the lack of space constraints (I want this slider to be lightweight and be able to fit inside a travel suitcase without much trouble.)

I've tried microstepping through my driver (DRV 8825), too - For the same speed values (as used with full steps), the motor coil can be heard to vibrate. And if I tweak the values to make the motor rotate, it seems to be some (approximate) multiple of the values I used for full steps previously, thus, again, making the motor usable only in the same ranges as it was in full step mode. Otherwise, the motor either vibrates fiercely or slightly, but without any rotation.

Solutions tried:

1) Microstepping (No luck)

2) Gearing (Tried and works, but can't use for my use case)

3) Different stepper libraries (Accel, PWM, etc.)

4) Variable resistor control (No luck)

At this point, I'm completely lost and clueless. Could it be something simple that I may be missing out? Or could it be something drastic, like having to change some main component (like the motor itself, or the driver)? Any help would be much appreciated and if any clarifications are required, I will be very happy to provide them.

Thanks!

My current code for Reference:

#include <AccelStepper.h>

AccelStepper stepper (1, 9, 8);
int MODE0 = 7;
int MODE1 = 6;
int MODE2 = 5;

void setup()
{
   stepper.setMaxSpeed(15000);
   stepper.setSpeed(12000);
   pinMode(MODE0, OUTPUT);
   pinMode(MODE1, OUTPUT);
   pinMode(MODE2, OUTPUT);

   //Motor is now running in Microstepping mode (1/16)

   digitalWrite(MODE0, LOW);
   digitalWrite(MODE1, LOW);
   digitalWrite(MODE2, HIGH);

}

void loop()
{

   stepper.runSpeed();
}


texts: How can I use electronics right below their operating temperatures?

texts:
Where I live (south of Sweden) is usually just below 0 Celsius night/day entire dark winter. I would like to set up a network in my garage which is wood and doesn't have any heating system.

The electronics I am planning to use (like powerline, switch etc) have operating temperatures between 0-40.

Should I use electronics without worrying about their operating temperature in my garage?

Other option I have been thinking is using the heat generated by electronics to heat up their environment. For example, if I could put all of them into a glass/wood box, the heat generated by them will be enough (I think) to keep the machines in their operating temperature. Is this a good idea? Any other suggestions?


texts:
I'm looking at this development board from Altera:
https://www.altera.com/support/training/university/boards.html#de1-soc

It says it has an ARM processor - this has me confused; does it mean the FPGA is programmed with a microprocessor? In other words, if I program the FPGA with my own Verilog, will it erase the processor and cause the ARM to cease to exist?

If not, why does this board need a microprocessor in the first place? Had one wanted a microprocessor, wouldn't one buy a Raspberry Pi for less, instead?

Thanks for helping me to understand this.


texts:
I am using freeRTOS in Zedboard. I am able to enable the PL-PS interrupt in bare-metal program. I couldn't really find any documentation/tutorial on how to link the FreeRTOS and the PL interrupt system. I am currently migrating my software to freeRTOS but I am not sure how to "connect" the interrupt between the freeRTOS and the PL interrupt. Here is what I have done and I am sure it is totally wrong.

In the main:

xTaskCreate(InitInterrupt, (const char * )"Init Interrupt",
            configMINIMAL_STACK_SIZE, XPAR_PS7_SCUGIC_0_DEVICE_ID,
            tskIDLE_PRIORITY, NULL);

Interrupt Enable Function:

XScuGic InterruptController;
static XScuGic_Config *GicConfig;
xSemaphoreHandle DMATransfer_trigger = 0;

int SetUpInterruptSystem(XScuGic *XScuGicInstancePtr) {
    Xil_ExceptionRegisterHandler(XIL_EXCEPTION_ID_INT,
            (Xil_ExceptionHandler) XScuGic_InterruptHandler,
            XScuGicInstancePtr);
    Xil_ExceptionEnable();
    //enable interrupt in ARM
    return XST_SUCCESS;
}

static void InitInterrupt( deviceID) {
    while (1) {
        int Status;

        GicConfig = XScuGic_LookupConfig(deviceID);
        if (NULL == GicConfig) {
            xil_printf("Interrupt Initialization FAILED!!\r\n");
            vTaskDelete(NULL);  //delete InitAXIDMA itself
        }

        Status = XScuGic_CfgInitialize(&InterruptController, GicConfig,
                GicConfig->CpuBaseAddress);
        if (Status != XST_SUCCESS) {
            xil_printf("Interrupt Initialization FAILED!!\r\n");
            vTaskDelete(NULL);  //delete InitAXIDMA itself
        }

        Status = SetUpInterruptSystem(&InterruptController);
        if (Status != XST_SUCCESS) {
            xil_printf("Interrupt Initialization FAILED!!\r\n");
            vTaskDelete(NULL);  //delete InitAXIDMA itself
        }

        Status = XScuGic_Connect(&InterruptController,
        XPAR_FABRIC_AXI_DMA_0_S2MM_INTROUT_INTR,
                (Xil_ExceptionHandler) InterruptHandler,
                NULL);
        if (Status != XST_SUCCESS) {
            xil_printf("Interrupt Initialization FAILED!!\r\n");
            vTaskDelete(NULL);  //delete InitAXIDMA itself
        }
        XScuGic_Enable(&InterruptController,
        XPAR_FABRIC_AXI_DMA_0_S2MM_INTROUT_INTR);
#ifdef DEBUG
        xil_printf("Interrupt Initialization Complete\r\n");
#endif
        vTaskDelete(NULL);  //delete InitAXIDMA itself
    }
}

In the interrupt Handler:

void InterruptHandler(void) {
u32 tmpValue;
//xil_printf("Interrupt acknowledged...\n\r);
//clear interrupt just perform a write bit to no 12 ofS2MM_DMASR
tmpValue = Xil_In32(XPAR_AXI_DMA_0_BASEADDR + 0x34);
tmpValue = tmpValue | 0x1000;
Xil_Out32( XPAR_AXI_DMA_0_BASEADDR + 0x34, tmpValue);
//Process Data Here!!

//initialize another transfer
    xSemaphoreGive(DMATransfer_trigger);
}

The interrupt source is from the AXI DMA Controller IP.
This is what I have tried but it doesn't work. Can anyone please give me some guide on how to modify the code to handle and setup FreeRTOS interrupt from the PL.
Thank you!


texts:
I am using Xbee S8 (XB8-DMUS). and trying to implement Led-Switch example http://examples.digi.com/lights-motors-more/802-15-4-digital-output-with-an-led/

But xbee S8 returns ERROR on AT command console.


texts: Why do some of my devices turn off and then back on when I turn off my space heater?

texts:
I have a small portable heater which is connected to the second outlet at the wall where the power strip for my computer is also connected.

Here is a link to the heater I use:
http://www.viewpoints.com/Sunbeam-Portable-Compact-Ceramic-Heater--446866-reviews

Whenever I turn OFF the heater, one of my monitors (I have three on the same strip) turns off and then back on and the USB web cam which is connected to my computer disconnects and reconnects (there is a blip-bloop sound from my computer).

Why is this?


texts: Replace DPDT on-on-on switch with relays

texts:
I want to control via Arduino a peltier cooler/heater that uses a DPDT on-on-on switch to set the voltage at the terminals of the peltier cell to +12 V, 0V or -12V. I have measured the voltages at the six terminals of the switch and the voltages in the three configurations are as shown in this figure:

The terminals at the top and at the bottom of the switch are set to either 0V or 12V as in the figure (voltages written in black). The position of the switch forms the colored junctions that set the voltages in the central terminals.

I would like to use an Arduino to control the voltages of the central terminals in a way analogous to the switch. I was planning on doing this by using relays, but I'm unsure how to do the wiring and if I need a 4-channel relay of if a 2-channel relay is sufficient. Do you have suggestions? Thank you.


texts: Powering an ESP32-DevKit with 3 AA batteries

texts:
for my project i have to put quite some stress on my ESP32-devkit in addition to it needing to be a mobile device. I need to power the esp32, an SD-card reader, an LCD-display, two I2S-MEMS-mics and an LED. I want to use 3 AA batteries, meaning 4.5V. The current i need while the device is fully engaged is around 118mA peak.
my plan:
use an LDO-regulator to step down the 4.5V to 3.3V and power the whole system with that.
my problem:
Most if not all SD-card breakout-boards run on 5V into an internal regulator, because for some reason SD-card readers are only manufactured for arduino users it seems (why?). So i thought i should use a boost-regulator and step up the whole thing to 5V, feed the 5V to the ESP32-devkit's VIN pin which then transforms it back to 3.3V where needed, while the SD-card can run on its desired 5V.
my questions:

Does a good boost regulator for 4.5V to 5V even exist, because i'm having
a hard time finding it (i cant be the only one with this problem)
Is there a 3.3V powered SD-card? This would cut down the problem immediately
Is 5V even enough for the ESP32's VIN pin? I read that it can take 12V max, but 10V is more efficient than less than that, so i'm really not too excited about being less efficient than i could be.

thanks for any help.


texts: All RTCs I've seen so far operate from a 32.768kHz crystal, which can't be divided to 100Hz. Are there 32.000kHz RTCs?


texts:
1I'm using class 2 medical graded SMPS in our device. So earth connection not recommended. When connecting SMPS to load (contains capacitive touch LCD),
touch function is affected by SMPS noise. When connecting SMPS earth point to protective earth, LCD touch function working properly.

I don't want to use earth connection because of class 2 constraints. I want to bypass that noise. I have added few decoupling ceramic capacitor at touch input supply to avoid high frequency noise to touch input. Still am facing issue.

Can anyone give me some idea to overcome above issue ?

SMPS Datasheet


texts: When two transistors connected which one is on and which one is in cutoff from given circuit condition?

texts:
here in this question's solution, given that upper BJT is on while lower one is in cutoff region for Vbb = 2.7 V and viceversa for Vbb = -2.7 V and both will be in cutoff for 0 V.
While in other problem Q1 is on and Q2 is in cutoff.

So my question is how to decide which one will be conducting and which one will be off and why? Is there any general procedure?


texts:
I am researching the lifespan of Arduino sensors underwater. I want to measure the water quality of a lake using an Arduino. I have seen that turbidity, temperature, ph and conductivity sensors don´t last long underwater but I can´t find any research on google scholar about the possibles sensors for a 24/7 sensor underwater.
There are some sensors probes available that are robust and they can last up to 3.5 years underwater but the cost is very high. I want to know if there are sensors that can be underwater for long periods of time.


texts: Continuity test buzzer sounding continuously

texts:
I have a  digital multimeter (DT 9205) which went on the blink recently. I was using the continuity function to check a circuit. With the wisdom of hindsight, I think it is possible that the cicuit might have been “live”, although none of the two fuses of the DMM blew.  In any case after the test, the buzzer sounds continuously & the LED comes on as soon as I switch the instrument on. The other functions however, still appear to be working as usual.

I shall appreciate if someone could point me in the right direction for where to look for the fault.


texts:
We have a 480V 3-phase connection for a borehole pump, and we need to get a temporary 240V connection for lighting, no more than a few hundred watts.

We are in South Africa which operates at 240V, and when measuring each phase on the 3-phase line we get 480V RMS.
To get 240V, we measured one of the phases and neutral, which gives exactly 240V RMS as we want, however this goes against my research online that it should be 277V RMS.

Is it safe to use this? Is this normal, or are the phases at a different angle perhaps? All three phases give 240V in reference to neutral.

The three phase line has the following colours, the same as the UK:

Edit: To clarify, I'm 100% certain that any connection between the three phases is always 480V and at least one connection between a phase and neutral is 240V, I'll do some more testing with the other phases to see if they also give 240V when measured against neutral.

Edit 2: The supply turned out to be a High Leg Delta type, as mentioned in the answer, and I am getting 240V successfully, working great.


texts: Common mode filtering for three DC lines

texts:
I want to filter common mode noise on three DC lines: +5V, GND, -5V at 1A.
Why are there so few options for common mode chokes with three lines? What is a good topology for this situation when using common mode chokes with two lines?


texts: I am trying to implement a datapath using sequential logic . Trying to implement this C program

texts: I was thinking of creating three registers , namely X, Y and Z. I initialize x and y to constants of '0', then I make register Z an active low register. I send a constant ' 0 ' to the input line of that register, and not the input. So it sends a 1 to the Write , Read Enable of the register so it doesn't function when it's high. I'm a bit confused on how to implement the rest of the code. Any ideas (even altering what I've thought about) is welcome! Thank you!


texts:
In the above circuit I was asked to find the input capacitance at the gate of Q1, Cg1, using the Miller approximation, to determine the frequency of the pole formed at the amplifier input in terms of Rsig,  use the Miller approximation to find the input capacitance of Q2, and hence determine the total capacitance Cg2 at the drain of Q1, finally to use Cg2 to obtain the frequency of the pole formed at the interface between the two stages.
Below's my attempt. Unfortunately I got stuck trying to find the frequency of the pole formed at the interface between the two stages. I'd appreciate some help with that.

\$M_{in}=[1/(j\omega C_{gd})]/(1-K))\$, where \$K=-g_m r_o\$ for CS.

Hence, the frequency of the pole formed at the amplifier input in terms of Rsig:

\$f_p=1/(2\pi R_{sig}(M_{in}+C_{gs}))\$

I think the input capacitance of Q2 would be:

\$C_{g2}=C_{gs} + C_{db} + K/[(j \omega C_{gd})(K-1)]\$

The big question -- in order to obtain the frequency of the pole formed at the interface between the two stages, do I now simply multiply \$C_{g2}\$ by \$r_o\$ to determine the time constant?


texts: Motor/MOSFET does not react to input on breadboard

texts:
I have tried so many different variations on breadboard of this circuit but the motor seems to just be powered by the power rail on the breadboard. It does not react to any change in the input and seems that the whole input is redundant to the MOSFET. (The MOSFET that I am using is WH50 2N7000.)
Essentially, if the thermistor is increased and exceeds the threshold of 25℃, the motor activates. If below the threshold, the motor will not operate. Theoretically it works but on breadboard it does not. Is there any reason for this?


texts:
I have been trying to work out a circuit something like the following:

simulate this circuit – Schematic created using CircuitLab

I want VOUT to be 3V when the switch is open and 5V when the switch is closed. The simulation seems to give me what I want when the switch is open, but not when it's closed. What am I doing wrong? Is there a better way to do this? I was avoiding a common cathode diode pair to avoid the forward voltage drop.


texts: Full wave center tapped transformer output voltage

texts:
I have a full wave center tapped transformer circuit with input voltage of 220V
How do I get an output voltage of 15V. What equations should I use ?

Here is the circuit:


texts: Can we use battery in reverse to step down a dc voltage

texts:
Lets suppose, i have a 12 v battery and i want to give 9v to my variable load.can i use a 3 v battery in reverse to get that output ?.
If yes, what are pros and cons of this method?
Why can't we see such method implemented anywhere?


texts: I bought an air conditioner in Thailand rated 220v-240v, 50 Hz. What could happen if I use it in our country which uses 220v, 60 Hz?

texts: I bought an air conditioner (split type) rated 220v-240v, 50 Hz. What could happen if I use it in our country which uses 220v, 60 Hz? A lead technician from a refrigerator and air conditioner shop told me that there's no problem which means they could install the unit and it will work properly. But another technician from another shop informed me that it's not possible. If they install it, there's no assurance that it will function normally. Another technician also suggested that I might need to buy a transformer or AVR. Who is telling the truth? Is there anyone who could give me "professional" advice about this?


texts:
I'm making a simple circuit for driving a fan based on temperature. Given that the LM339 needs  a pull up (R5) do I need to put a series resistor in between the LM339 output and the gate of the mostfet? The connector X1 is a KK Molex type connector with 12V on it but but D2 is there to protect for reverse polarity. X2 is the fan connection.

Any other improvement suggestions welcome

UPDATE:

For future reference, if you (like I couldn't) get the power and gnd inputs up for a chip then use the invoke command to force it to reveal these pins.


texts: What type of capacitor do I need to stabilize USB voltage?

texts:
I am trying to use a "FET" (https://elinux.org/RPi_GPIO_Interface_Circuits#Using_a_FET) to switch the power supply to a USB speaker from my Raspberry Pi.

It's working well, however when I turn the volume to greater than 60%, the speaker plays a sound but then dies and disconnects, only to reconnect via USB 2 seconds later.

I'm thinking that the voltage is probably dropping too much, but I'm not sure.

I'm using the NTE2987 Logic Level MOSFET N−Channel and a 100k resistor to switch the USB ground, just as described in the above link.
I've tried to use multiple 100uf capacitors to "smoothen" the voltage, with no effect.

Appreciate advise on how I can make this work!


texts:
I use LTSpice XVII in macOS. I want to create a symbol from a schematic so that I can instantiate that symbol wherever I want. I tried this tutorial but I can't get it working.
Any help?
Thanks in advance!


texts:
If I were to have an IC (Just some standard 5v microcontroller), and for some reason I only had a -5v supply, could I technically connect -5v of the supply to the GND pin of the micro and the ground of the supply to the 5v pin on the micro? I've always thought this would work, but everybody I've talked to has said it's a bad idea. I assume they say it's a bad idea because if you had a device on the same system that was spitting out voltage spikes down the central ground, it could overvolt your micro.

So, more of a 2 part question

Is powering a 5v micro with a negative voltage on the GND pin possible?
If so, what are the downsides of doing it this way?


texts: I am new to electrical design. I am experimenting with op-amps on LTspice, I cannot seem to figure out why my output signal is smaller than my input. I chose Rf to be 10k and Rin as 1k. The gain should be 10. Can someone explain what I am doing wrong?


texts: how to find out wether the stepper motor is working or not?

texts:
I have unipolar stepper motor with 6 wires and i have made controller circuit but when connect controller to stepper motor it is not working.. So i want to know weather stepper motor is working or not.  Is there any simple method to test steeper motor?
Thank you!

ADDED: olin lathrop i have added digram. The other comination such as AB,AC, AD,BC,BD etc  gives 50 ohms in multimeter.


texts: How would I place CAN termination resistors in a 3 ended configuration?

texts:
I have a project for which I have one central circuit board which has a can node on it, this central circuit board has three connectors on each of which a node could or could not be plugged in with a cable (max. 2m). A simple diagram of the setup would look something like this:

Any off the connectors could or could not be connected to a node depending on how many peripherals are connected. And FYI the nodes are never connected or unconnected while the system is running.

My question is, where would I place termination resistors and why would I put them where you suggest ?

Thanks for all answers in advance.


texts: Is it possible to transfer a bluetooth signal via something else?

texts:
Problem: For example, I have 2 devices communicating with each other via  bluetooth. But there is a thick metal wall between these devices and this makes a difficulty between them.

To fix it, can I use a reference bus,sensor or any device? This (third one) thing will be able to reach both devices and will help them to communicate because they cant communicate with each other easily because of the wall but this new third thing is able to reach both of them.

My question is what is this third thing? Or is there something like this?

Here is also an illustration to understand:


texts:
I would like to bring this formula in the form Re(D) + jIm(D):

This is my current progress:

My question is:

How can I get rid of the imaginary part jωC2*R?

When the denominator is completely real I can just split up the formula and have an imaginary and a real part.


texts: Digitally controlled smoothly variable gain?

texts:
I have a circuit that outputs about 600mVpk wave shape. I need to be able to output between 10mVpk to 10Vpk accurately, preferably with no calibration but a known error. The whole process should be supervised by digital means.

The general scheme I was thinking about is amplifying the signal to 10Vpk and some attenuation device to set different gains. This could be a series of resistive dividers that can be inserted in line. Each one is attenuating the signal by a different amount like -2dB,-4dB,-8dB,-16dB and they can be combined to create more attenuation points like -6dB or -30dB. This can be done using 4 SPDT relays but this is not enough. What additional element can I use to make up the spaces. I would like a high resolution. Possibly 10mV if possible.


texts: What use is the copper foil between the primary and secondary windings of a transformer?

texts:
I took apart a small transformer. It is of shell construction type. Beneath the primary windings, I found a strip of (floating) copper foil wrapped around the secondary windings. Of course there is mylar insulation between those three components.

Based on what I read here: Magnetics Design 4 - Power Transformer Design, small transformers have the problem of limited space, taken up by insulation and voids between round wires. A copper foil increases the copper volume that can provide better magnetic coupling.

Am I right in my explanation? Or is it something else?


texts:
I am very new to electronics so please go easy on me.

Whilst I have read a couple of electronics fundementals books so far, one of the things that confuses me the most about electronics is how voltage and current is managed based on the fact that current affects the whole circuit.

Here is a very simple explanation of a situation that would confuse me.

Say I had an LED which had a 330R resistor on a 5V DC supply and I decided to connect 4 more in parallel.  According to the laws of electronics, this should increase the current going into each LED (as according to my calculations, each LED now has a resistance of 66R - raising the current to pop levels).

What would be the best way to solve this?

A more complex example would be where I had a PIC driven circuit for detecting voltage and checking for a specific combination of keys (an electronic keypad).  I then decide to add in a power LED, in parallel, to determine if the circuit is even on.  I assume this would affect the voltage and current delivered in my original circuit and potentially break things, would it not?

If so, again, what would be the best way to solve this?

I think, to sum it up, I am confused as to how circuits of any complexity are managed when adding a component can completely upset the balance of voltage and current.


texts: Why do two different multimeters show completely different resistance readings?

texts:
I just received a brand new Brymen 869s and I'm concerned it may be broken as it's giving a strange reading.

When measuring a 100k 0603 resistor which is soldered into a PCB (forming part of a larger circuit) I get the following readings:

Direction away from J1: 3.29MΩ
Direction towards J1: 2.02MΩ

I took some the same readings using a different multimeter, a Proster VC99 and got these readings:

Direction away from J1: 100kΩ
Direction towards J1: 8.66kΩ

At J1 there is a 10kHz 2Vpp sine wave.

Why would the Brymen show a value above 100kΩ whereas my cheapo Proster VC99 does not? Surely there's no way that the resistance can be larger than 100k in this circuit.

Here's the signal processing part of the circuit with the 100k resistor marked by the blue arrow. There are 4 similar circuits in the whole PCB since this is a 4 x voltage controlled amplifier circuit.

There's also a power supply.


texts: Bluetooth Controller using Arduino Uno and HC-05 doesn't work when connected to PC

texts:
I had an old Guitar Hero guitar that had the circuit board on the inside broken, so I decided to replace it with an Arduino Uno and an HC-05 to make it work over bluetooth. I installed the HID capable RN42 software onto the HC-05, then used the commands to set it to HID mode. Then I wired it according to this schematic, but didn't wire any of the joysticks and only wired 5 pushbuttons out of the twelve in the sketch.

With this sketch uploaded to the arduino, I connected it to a laptop, but when I open Joystick Properties on Windows, the buttons don't respond. I've looked for hours trying to find out if the code I used was faulty and making sure I wired the buttons correctly. Could the missing joysticks and buttons be causing this, or is there another aspect I should check?


texts:
I am reading about Thévenin's theorem on the page.

As you can see from the Practical limitations section, there is a one shortcoming that I don't understand.

  The Thévenin equivalent has an equivalent I–V characteristic only from
  the point of view of the load.

Could anyone explain it more?


texts: Use of RC circuit in amplifier output stage

texts:
I have to use a LM384 amp circuit (shown below) for a school project and need to explain how it works.

I've read the datasheet (http://www.ti.com/lit/ds/symlink/lm384.pdf) and thus have a guess about some components but others remain a mystery.

Vin potentiometer is only a voltage divider to adjust input voltage
.1uF capacitor (above) is a decoupling capacitor to avoid noise in the power supply
5uF capacitor has the same purpose
RC branch + 500uF capacitor : That is the question. I don't really get the purpose of this.

Is the 500uF capacitor combined with 8 Ohm load just making a high pass filter with a cutting frequency of 1/(2*piRC) = 40 Hz ? Then what would be the point of this parallel RC branch?

Any help appreciated, thanks a lot!


texts: Is it legal to reverse-engineer an integrated circuit (IC) belonging to a manufacturer

texts: Can anyone tell me whether it is legal to reverse-engineer a chip to prove the existence of possible backdoor technologies in which the device or IC manufacturer likely is unaware of?


texts:
The amplification of this amplifier is 1. So we have a buffer. But the question i wanted to ask was.

What can we tell about the current amplification of the circuit below? Is this circuit useful?
I also found out that when i apply 8Vp-p at the input, i have a distortion at the output. Why does it happen around that voltage? or a basic explanation on it!


texts:
Basically, I'm an amateur rower with mechanical engineering experience, however I am lacking in electronic knowledge. I need to find a way of measuring the pitch of the boat whilst I'm rowing, the reason for this is that I'm informed the balance of the boat affects the speed.

I was thinking of using an accelerometer.

Just wondering if there are any other viable ways of doing this, as I want to be sure this is the best way of doing so.


texts: DIY high fidelity audio using delta sigma adc

texts:
This question may be too general, but I will include all the details that I can. My end goal is to achieve a super high-resolution spectrogram of any recording I choose to make. By doing some tests I realized that the higher the sample rate the higher the spectrogram resolution which makes sense because with a higher sample rate the same size bin will correspond to a finer time resolution. However, after looking for the highest sample rate ADC I realized that there is another parameter called resolution in the ADC world that corresponds to the resolution of recorded signal power. I supposed that increasing this parameter would also increase spectrogram resolution because there would be less of a color jump from pixel to pixel. I have tried to understand the ins and outs of sigma-delta ADC modules but I can't seem to get a solid grasp because there are so many parameters.

Note* Before I launched into my ADC investigation, I tried going the consumer route and just buying a good audio ADC. I found that most of these consumer devices were overpriced and under specced (probably because most people would like to record sound for the sake of listening to it not looking at it). I did find some promising products like this one from Korg https://www.korg.com/us/products/audio/ds_dac_10r/, but my suspicion is that a higher sample rate and resolution are physically possible and are obtainable for less money. Also, I have minimal EE experience (competent with Arduino projects and general coding).

So my question is this. What ADC parameters should I look for to fulfill my goal? Here are some that I am looking at:

https://www.digikey.com/product-detail/en/texas-instruments/ADS7886SDBVT/296-19307-1-ND/948628

http://www.ti.com/lit/ds/symlink/ads1605.pdf

I realize I am way out of my depth here. I would appreciate any advice or ways of recording the quality of audio that I need without building an overclocked ADC or buying an overpriced sound recorder.


texts: Neophyte question about AC vs. DC (especially for powering a home)

texts:
Here in the United States the electricity grid is AC.  I have heard that AC allows transmission of power at greater distances with less loss.  However, with the advent of solar panels, it would seem that one could generate DC power directly and power the home this way.  There are no great distances involved.

Why is this not done?  As far as I know, solar panels feed back into the main electricity grid.  This means they convert dc to ac, presumably at some loss.  Could you power your whole house using DC?  Assuming you lived in a sunny area and had sufficient roof space, could you power everything (fridge air cond. etc), perhaps storing the power in batteries for use at night time?  I assume you'd need all new appliances that work with DC?

It would seem a small price to pay to be energy independent.  Could you reuse your existing house wires?  I've never heard of this, so I assume there are major obstacles.  Could someone give me the layman's explanation as to why it's a bad idea, or impossible, or just not done?


texts:
I'm new designing printed circuit. I designed some 2 layers PCBs (not too complex).
I would like to know maybe a list of concepts that I need to check in my PCBs, or to know.
I would like to jump to 4 layers pcbs, but everytime that I've looking in Google information, it's much complex than 2 layers. Impedance tracks, resistance of the tracks, decoupling capacitors for some impedance, EMIS, and the stack of course. I know this concepts separately, but when I'm designing I don't really know much more than the datasheet can tell me.
I want to put a capacitor for decoupling some signal in a four layer PCB, but I want to know how it's affecting to my circuit and why I'm placing it in this place.
Any book or course or reference will be very helpfull for me.
Thanks in advance.
Edit: I read in other post this two books that can help me

Eric Bogatin's Signal and Power integrity Simplified
High Speed Digital Design: A Handbook of Black Magic


texts:
Specifically, a 2pin and 4pin quartz crystal oscillator.

What I know: current is applied and the crystal oscillates in order to provide an oscillating signal.

What I want to know: How does the vibration cause an oscillating current? How are 2/4pin crystals different? Lastly, why can a 4pin run alone and a 2pin needs capacitors.


texts: What are the values of these 2 resistors?

texts:
What are the values of the two highlighted resistors?
Considering the brown band as tolerance and ignoring the first (black) band, I came to the conclusion that the values are 680 and 220 milliohms. Is that correct? Thanks.


texts: Why can the polarization of an antenna array be determined by the polarization of its individual elements?

texts:
In problems determining the polarization of an antenna array I've looked at, the polarization of the total array is determined by finding the polarization of a single element and then extrapolating that polarization to the whole array?

I'm not sure why this can be done. Is it because the elements in an array are all parallel to each other so the polarization would be the same?


texts: If a capacitor has a low voltage rating, why isn't it damaged by low current, high voltage static charge?

texts:
Capacitors usually have a voltage rating marked on them. From what I gather, it's the maximum voltage it can withstand without being damaged.  Let's assume you have a 35V capacitor and you rub your feet on the carpet to build up several thousand volts.  If you connect one terminal to ground and touch the other terminal with your finger, why doesn't it damage the capacitor?

Given static electricity normally has small amounts of current, if you repeatedly statically charge the capacitor, will it eventually fail?  If so, shouldn't a capacitor also also have a current rating as well?


texts: What kind of microcontroller is suitable for call with home phone network (NO SIM-CARD)

texts:
For a educational purposes, I want design a security system which works with a PIR sensor.  The application is after detection of movement the processor will call a telephone number that defined.
I know approximately everything except module for calling.
I don't know how the application of home phone networks (which work with RJ11)
What kind of micro and modules are suitable?


texts: What to consider when designing a pcb for HV?

texts:
The question is already in the title: What should I consider when I want to design a PCB with a voltage output up to 2 kV? Only the output lanes are going to be on this level, the other lanes are on 5-10 V.
Can I still use a 4-layer PCB? Should I use special materials, and if yes, which one? The maximum amount of current on the HV lanes is in the nA range, thus not important (afaik).


texts: Why aren't 1Hz crystals used to measure seconds?

texts:
According to Wikipedia:

Many clocks use a 32.768KHz crystal.  Is this because the crystal is smaller than a 1Hz crystal?

If 1.0 Hz == 1.0 second.  Then, why the need for the division?


texts: PC Power supply for a PC/104. Current output

texts:
I have to do some work on a PC/104 CPU board. Until now I have been powering this from a separate power module (acs-5151 at the same link) that took in 8-40V and gave +12, +5, and +3.3 out. Until now, I was able to power the CPU module with the 5V line but don't have access to that anymore. The CPU module is an 8W system and in the past we were able to see that it was only drawing about 0.5A. I tried using a small lab power supply but it didn't boot up the CPU (although some of the LEDs did light up). As this supply says it is only capable of 0.75A continuous I thought that perhaps this wasn't enough to boot the it up. Then I was thinking that I could use the 5V line from a normal PC power supply. When I check the supply though it says 5V /22A. A friend suggested that the CPU might only draw what it needs but wasn't sure. I'm afriad to try it as it's a very expensive piece of hardware and can't afford to damage it.
I was wondering if anyone could tell me whether a PC power supply will only give the current needed or if there a danger of it damaging the PC/104 module?


texts: I have some problems obtaining the thevenin equivalent with op amp. The next example is in Fundamentals of electric circuits of Sadiku. Can you help me get thevenin equivalent from the example?


texts: Is there a cheap thermally conductive, electrically insulating potting compound?

texts:
I've got some some ready-made 12v LED units. I wanted to pot each and put it in a metal container for robustness and to try and dissipate some heat.

I'd like to pot the circuit but was hoping to avoid expensive potting compound. Is there something cheap I could pot the circuitboard in? It would need to be electrically insulating but have better thermal conductance than air. Not necessarily that much better, I assume these units are meant to be used in enclosed spaces like desk lamps.

I was thinking of silicone sealant or clear casting resin but I have no idea of their properties. Bonus points for optical transparency but it's not a requirement.

Any suggestions?


texts: Bluetooth Modules in a plastic enclosure

texts:
I would like to implement a bluetooth functionality in my project, preferably using STMicroelectronics SPBT2632C1A.AT2, with a protective enclosure. But I read from multiple sources that bluetooth antennas get detuned if they are surrounded by a plastic material.

My question is, are these bluetooth modules (like the one I mentioned above) subjected to the same problem? Would the attenuation be too much to the point that the communication would become unstable? My application requires fast (500k baud) and reliable communication within a few feet. Is this possible?

Thanks in advance.


texts:
I want to wire an emergency shutoff button to switch off the circuit of one room.
While I understand what to do in theory, I am not quite sure how exactly the button needs to be wired.
It is one of these that needs to be pulled out manually and stays there until pressed or power runs out, so the machines also don't restart if the power was cut externally and comes back.
It has 4 terminals, and I suppose I need to connect it to neutral, incoming phase and the outgoing phase (which is going to the switch,) but am unsure of the exact wiring.
I suppose to do it safely I need a 5-wire cable between the button (which is on a central location in the room) and the switch (which is at the position where the power is coming out of the wall,) so I can send both phase wires over it without "relabeling" a ground wire as phase.
I made some pictures of the switch, maybe it's more clear from them.
Also, I am from Germany (I know there are some local laws/rules regarding that.) That combination of switch/button has worked before, but unfortunately I did not remember the exact wiring.


texts:
I have a 12 V power supply that's not working anymore, so I opened it up and checked for faulty components with a multimeter, and I found two of them so far. One was a 1000 µF 25 V electrolytic which I quickly replaced with a new one, and two was an X2 capacitor with 0.33 µF 275 V rating.

My problem is I don't have an X2 capacitor with that value. All I have is a 0.1 µF 275 V X2. But I do have a 0.33 µF 400 V polyfilm (Mylar) capacitor with me. Can I use that instead of an X2?


texts: Arduino PWM to analog: RC filter vs DAC?

texts:
I want to use an Arduino to control the throttle signal going to a high power motor ESC. The problem I have is as the Arduino outputs a PWM, the ESC reacts by pulsing the power to the motor. So I searched a bit and I understand that to convert the PWM output of the arduino to an analog signal I can use a RC filter. Also I was wondering whether DAC ICs actually convert PWMs to analog. Knowing that the Arduino has a PWM frequency of 490Hz, which of the two methods would you recommend?
Thanks for your help!


texts: Adjustable voltage doubler circuit across resistive load...doable?

texts:
Disclaimer: what I am proposing is dangerous, and I know that. I would discourage anyone, regardless of expertise from undertaking such a pointless risk to their health and home.

After my recent (mis)adventure with the dryer, I now have a physically intact, technically functional heating element. I've been looking for an excuse to repurpose it for a DIY project, and then realized I've wanted to try making my own 2 stage Cockroft-Walton voltage doubler for a while. Seeing as the element itself runs on 240 volts, and the current running to my house is 120, I thought, "Maybe I could run a voltage multiplier off one of these transformers I have lying about, hook a potentiometer up to it with the wiper running to the input side of the element, and then run it to ground."

This is, inherently, a bad idea. I know. But can it be done? I have drawn here a pretty common depiction of the circuit, with the addition of the voltage divider and element attached as a load.

Upon re-examining it, it occurred to me that I probably couldn't return the 240 volt DC output to the same ground connection the circuit used without something very very bad happening, so I am a bit stumped there. How would I properly terminate this, seeing as I need some sort of ground to reference from? Other concerns I have are what AC input source should I use -- transformer, or main?

What effect will arbitrarily changing the output voltage of the circuit have on the circuit itself?

Is using a pot even feasible here?

Here is a horrible drawing of the circuit I am suggesting


texts: ARMCC dependency on ARM processor on the board

texts: Is armcc dependent on the type of ARM processor on the hardware board ? Example: while I compile my code (using a make file) where option CPU=CORTEX-A9 is given , it errors out stating argument CortexA9 not permitted for option cpu.  The armcc version I am using is 3.1


texts: PC14 and PC15 on STM32F401 not working as inputs

texts:
I'm trying to use PC14 and PC15 on Nucleo F401RE board, as inputs using this simple code:

  RCC_LSEConfig(RCC_LSE_OFF);

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);

  // initialize ID pins as inputs
  GPIO_InitTypeDef gpio_init_struct;
  GPIO_StructInit(&gpio_init_struct);
  gpio_init_struct.GPIO_Mode = GPIO_Mode_IN;
  gpio_init_struct.GPIO_PuPd = GPIO_PuPd_UP;
  gpio_init_struct.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
  GPIO_Init(GPIOC, &gpio_init_struct);

  // read ID pins
  uint8_t inputs_state = 0;
  inputs_state |= GPIO_ReadInputDataBit(GPIOC, GPIO_Pin_13);
  inputs_state |= GPIO_ReadInputDataBit(GPIOC, GPIO_Pin_14) << 1;
  inputs_state |= GPIO_ReadInputDataBit(GPIOC, GPIO_Pin_15) << 2;

Unfortunately, while PC13 works as expected, PC14 and PC15 always stay high in case of pull-up configuration or low in case of pull-down.

The reference on page 155 states:

  The LSE oscillator pins OSC32_IN and OSC32_OUT can be used as
  general-purpose PC14 and PC15 I/Os, respectively, when the LSE
  oscillator is off. The PC14 and PC15 I/Os are only configured as LSE
  oscillator pins OSC32_IN and OSC32_OUT when the LSE oscillator is ON.
  This is done by setting the LSEON bit in the RCC_BDCR register. The
  LSE has priority over the GPIO function.

So I'm setting LSE off, but still no result. What am I missing?


texts:
I'm currently trying to create a 4 bit ALU using the CD4011BE quad 2-input CMOS  NAND gate ICs. However, I'm having some trouble when creating the full adders. Sometimes, when the IC outputs logic low, I'm getting 2.5V, which causes the next NAND gate to also output something like 2.5V. This carries down to the sum, which is 2.5V when supposed to be under 0.5V. I've read that ICs need decoupling capacitors, but I'm not sure if that would cause this problem

I'm testing this on a Breadboard, and running 5V rails.

EDIT: I've tried testing the voltage of each pin. Strangely, the ground pin had 1.5V while only being connected to ground. I tried replugging everything in, and it worked perfectly now.


texts: Monitoring two serial lines at the same time

texts:
First this is the setup:

(please note that one of the grounds is not connected, both FTDIs working properly)

Now, I have used PuTTY to look at these two serial streams, both exchanging data at 9600 bauds, but my problem is logging the activity time-wise.

I've also tried some serial monitors that I found on the tubes, but the time resolution is in seconds.

Is there a tool for monitoring these two streams at the same time? If there is not, I should program one myself in Processing (it will take less time in this language I suppose).

PS: the ultimate goal of this is to replace the remote device (an actual wired remote) with a little MCU like the ATtiny85 or ATtiny2313 with a simulated input.

PS2: I only have these two FTDIs, an analog oscilloscope and a multimeter.


texts: How to simulate an external piece of hardware during the development of a LabView FPGA project

texts:
I am working on a PXI system from National Instruments. It has an FPGA card that I have connected externally to a sensor.

I would like to know how to perform a "cycle accurate" simulation that includes a custom external stimulus that emulates the sensor.

There is a lot of example for simulating the labView -> FPGA -> labView interfaces, but nothing for LabView -> FPGA -> external hardware.

If it hasn't been a NI FPGA system, I would have written an HDL test bench for that, but within the NI FPGA framework, I can't figure out where to put my test bench.

In fact there is a place to put an HDL test bench, but as I said, the only available interface to test is the one between the labView code and the FPGA, and not between the FPGA and the external FPGA pins.

Maybe one of you already faced that issue.

I have some ideas such as : Custom CLIP that embedded the VHDL for simulation of the interface?

I already posted on StackExchange, but only EE's play with FPGA... ;-)


texts: It's inductor or diode in LCD PSU [repairing]

texts:
I have a little problem repairing my LCD power supply (22 inch old monitor). I already change the damaged capacitors (one is good but i change all 5 anyway, last image bottom right).
The problem didn't solved then i continue searching why don't turn on the monitor.

Now i find a component that appears to be bad, it looks like a diode, but the symbol is for inductor if my memory dont fail.

It's completely black, and i cant figure what is it. I tested and is in short circuit without any resistance.

Somebody know what is it?

Anyway the PSU is this one: YP1504PG 6871TPT318G 207.01.03 REV 1.3

I checked the voltage in  the output and must be 2x 5v and 2x 15v but no one give current. Anyway the monitor dont start, but the filter fills and remains with about 340V (the two at bottom left).

Thankyou in advance


texts:
I'm a total newb, but I'm learning fast.

Is there any easy way to get this nichrome wire to fasten to the plate below it?  Could I just tuck it underneath the plate, between the mica board?


texts: Arduino sensor ground isolation on motorcycle

texts:
I am attempting to use a 5v Arduino pro mini to display the current gear on a 2005 Kawasaki Ninja based on the ratio of the wheel speed and the engine RPM. The display is a single digit 7-segment display. The RPM input is coming from the 12v coil signal wire. The wire provides 12 volts and then goes to 0 volts to trigger the coil to fire. I have no problem reading the 12v-0v-12v pulses with the arduino. The Arduino groud is connected to the motorcycle's ground and the coil signal wire is going to digital pin 2 via a 1k ohm resistor.

The wheel speed is coming from a hall effect sensor provided with the TrailTech gauge pack I already have on the bike (http://www.trailtech.net/digital-gauges/vapor/752-300). The voltage difference in between the two wires is 3 volts except when the magnet passes by where is goes to 0 volts. I have been able to read the 3v-0v pulses by simply splicing two wires off of the sensor leads and connecting the positive wire to digital pin 3 and the other wire to the arduino's ground. With the sensor connected like this, the arduino can read the pulses from the sensor and the gauge pack can read wheel speed without any problem.

The problem comes in when trying to read both wheel speed and engine rpm. I have the coil signal wire and the wheel speed sensor connected as described above and am able to read the coil pulses but not the wheel speed pulses and the gauge pack is also not able to read wheel speed.

I believe this is because of a lack of isolation and the noise from the motorcycle's electrical system but I am not sure. My first thought is to use an optoisolator to send the wheel speed signal. My (possibly naive) thought process and limited understanding of optoisolators lead me to believe that I should be able to connect the two wires from the hall effect sensor to the input for the optoisolator and use the output from the optoisolator to trigger the arduino.

Can anyone tell me if my assumptions are correct? Are my issues reading wheel speed likely caused by a lack of isolation? Is an optoisolator the way to go?


texts: Is using a ground AND supply pours on a 2-layer PCB a bad design decision?

texts:
Ground pour on the top, supply pour on the bottom. Does this typically increase noise? Is it considered a poor design decision?

It's certainly makes things easier from a routing perspective to pop a via down when you need to supply a pin with power.


texts: T-type Flip-Flops with state-dependent switching times

texts:
A simple "On-Off" push-button circuit is easily implemented with a D-type flipflop. However, I need my flipflop to turn ON when the push-button is pressed and OFF when the push-button is pressed and held for several seconds.

The few simple criteria as follows. The last criterion is there to remove any ambiguity in the scenario:

The momentary push-button is part of a rotary encoder and shares its common anode;
The ON 'press time' should be under 0.5 seconds, but still incorporate some debounce;
The OFF 'press time' must be at least 5 seconds;
The current draw when idling must be as low as possible;
The solution must be purely hardware - I cannot use a uC.

After much deliberation and shouting I came up with the following circuit. It performs to the specification, except I'd like to know if there is a way of doing it with a lower component count.

Vcc = 3.7V. U1 (MAX942) is currently a simulation stop-gap and will likely be replaced with a lower-power equivalent, if there is one. The R/C values give suitable timimgs at present.

The circuit is quite simple: Q2 charges C1 and C2 through 1k resistors. When 'SWITCH' is pressed the caps will discharge through R3 and R5, respectively. When a capacitor's voltage drops below THR the compartor will go HIGH, providing a rising edge to CLK. However, when the flipflop is ON, Q4 shorts the output of U1:A, denying CLK of said edge. If the button is held down for long enough then C1 will eventually discharge below THR and U1:B will provide the rising edge to CLK.

I can't think of a simpler solution; everything I've tried ends up spiralling into complexity. Any recommendations would be appreciated.


texts:
Why are capacitors available with values like 378 µfarad and 0.22 farad which have prime numbers like 11 and 7 in factorization instead of values like 375 µfarad and 0.2 and 0.25 farad which are nicer in factoring and addition?

What makes the manufacture of former advantageous than latter?


texts:
I just added the ICSP port on this schematic here

however, when the programmer powers the circuit from the ICSP (pin1 +5V, pin6 GND) it also polarizes the relay and the bs170. If for some reason the BS170 triggers the relay will start to draw a lot of current straight from the programmer (pickit2, 3 or whatever). Is it a concern? I'd like to avoid a physical switch to isolate the relay from the circuit when in programming mode.


texts:
I was tearing open an old ATX power supply from one of my old computers today, because it was making a funny high-pitched wining noise.

I noted that several of the components within were starting fuse together into a sort of electronics mush.

My thought is that it's probably no-longer safe to use this power supply, so I swapped it out in the old computer I was using.

Here are a few photo of the component mush:

Now I guess my question is:

Can I fix this?
How long do I have to wait before the capacitor within has indeed run out of power?
(it's a 350W ATX Power Supply)
Is there any place to find out what components I need to replace them?


texts: Spec'ing power supply to replace a battery pack in a DIY project?

texts:
I am attempting a DIY hack that involves (among other tweaks) replacing a battery pack with a PoE power supply. The battery pack in question uses 8 1.5v D-cells in a series-parallel configuration that produces 6v.

How do I go about figuring out how many amps my power supply will need to support? The device in question is an LED lantern, and the only likely-looking spec I can find is the marketing claim that 8 alkaline D-cells will last 32 hours on the high setting.

Also, am I correct in my vague understanding that amperage is generally a capacity, and thus more amperage is generally not harmful? Whereas too little amperage will result in a voltage drop? (I did study basic electronics in the military, but that was a very long time ago…)


texts: Livewire - Emulating geardrive current peaks

texts:
I'm trying to simulate a very simple Darlington circuit w/ the Livewire software, including a 24 VDC gearmotor on collector (plus capacitor and diode). The fact is I would like to emulate some collector current peaks as a result of gearmotor load variations.
To emulate that, I havent had a better idea than include a variable resistor on collector, and manually force current variations. Is this procedure ok or do I have to solve it in a different way?
Many thanks!
Cheers


texts:
This is the "Automatic Ink Detection” PCB from an Epson inkjet printer. According to the service manual, it either detects or cleans clogged nozzles (this is not clearly explained). The service manual does say that high voltages at a few microamps are present on this board. The board is connected to the main control board through a flat flexible cable and to a wire grid on top of the waste ink pad/nozzle cleaner assembly through a silicone insulated high voltage wire. The smaller board attached to it with the Matsushita logo and the transformer seems to be some kind of self-contained flyback converter but I could not find a datasheet.

In terms of design, I’m primarily wondering about the irregularly patterned via stitching all over the board and the loops in the PCB traces areas marked L1 and L2. Since nothing on the board seems high-current, the via stitching is probably not for heat dissipation. If anyone knows what exactly the “Automatic Ink Detection” feature does, that would be helpful too.


texts:
this  sub-code  that read the selection line s4-s1 and take the summation of a,b in the selection line =0000,  When running this code in ISE project negotiator  it gives syntax error tell " Syntax error near "=" " in the line z=0 in the if statement

can you tell me why ?

module one1(a,b,s1,s2,s3,s4,f );
  input s1,s2,s3,s4;
  input [3:0] a,b;
  output reg [3:0] f;

  reg  z,n,c;

  //0000

  if ({s4,s3,s2,s1} == 4'b0000)
  begin
    assign {c,f}= a+b;
    if (f==0)
      z=1;         //here is the error
    else z=0;
    n=f[3];
  end

endmodule


texts: What is the difference of a loadell input and output resistance?

texts:
I am trying to understand the specifications of a load cell and there are the input and output resistance as you can see here, it says 1090±10Ω for input resistance and 1000±10Ω of output resistance.

This document says the following:

  OUTPUT BRIDGE RESISTANCE -
  The output resistance of the cell. It is measured by placing an ohmmeter
  between the signal or output leads

  INPUT BRIDGE RESISTANCE -
  The input resistance of the load cell. It is measured by placing an ohmmeter
  across the input or excitation leads. It is usually higher than the output bridge resistance because of the presence of compensating resistors in the excitation circuit.

Then I understand the output resistance is the measured resistence between the S+ and S- (see representation of the bridge below), that is 2R/2 = R (two resistor and series = 2R, and then 2R and 2R in parallel).
But in my first read of input bridge resistance definition I understood that it is the value that I measure between E+ and E- (that AFAIK is R too). The part that I don't understand is about the input bridge resistance being "usually higher than the output bridge resistance because of the presence of compensating resistors in the excitation circuit."

I would appreciate if somebody could explain me this? I would say the contrary, if I have other resistances in parallel with the nodes E+ and E- the measured resistance between this nodes would be lower and not higher than the resistance measured between S- and S+, but I am wrong, why?

Thanks a lot.

simulate this circuit – Schematic created using CircuitLab


texts: Is it possible to solder or otherwise connect to this camera chip by hand?

texts:
[Disclaimer: I'm a beginner.] I ordered this OV7740 camera chip from Digikey without really researching it, thinking maybe I could connect to it with a microcontroller. (I have only Arduino at this point).

Digikey part page
"Datasheet" link

I just took these photos, next to a penny.

How do you connect to that? Is there a name for that type of connection? Can it only be handled by robots, or is there something I can learn to do by hand that could connect to those 32 contact points?

The sides of that chip are about 2-3 mm.


texts: Diagnosing potential damage to garden solar light

texts:
I'm just getting started with electronics and so for a simple project I tried to desolder the LED from a garden solar light in order to attach a female header (I trimmed it to 2 pins). My intention was to use the header as an easier way of experimenting with different 'loads', with the benefit of being easy to plug the LED back in when desired.

But after desoldering the LED and soldering on the header, when I attach the LED to the header it doesn't light (the battery was disconnected when soldering).

The voltage I measure across the header with the LED plugged back in is 1.26V, but in series with the LED I measure no current. When the LED is not connected, I measure a current of 46mA across the header.

(the original 1.2V 2/3AA Ni-MH battery is connected when measuring)

(the LEDs that were removed all work in a separate circuit, so the LEDs are not damaged - at least not obviously to me)

Another unmodified light I bought at the same time measures 1.2V across the LED and a current of 3.46mA.

I think I've damaged the circuit somehow (I suspect whatever is underneath the black blob), but I'm not sure how to diagnose the problem. Are there any tips I can follow here?

Could it be that I applied too much heat during soldering and the circuit was damaged? It is a small board and so I guess the heat isn't spread out a lot.

Thanks.

The inductor shown below is 56uH (green-blue-black-silver) and I measured its resistance to be 3.5 ohms (using the resistance setting on my multimeter).


texts: Connecting arduino and separate power supply grounds

texts: I am working on an arduino project that uses transistor switches to power on high power leds that are powered by a separate 24 volt power supply.  My issue is that I have two different grounds, making it difficult to bias the transistors.  Can I just connect the arduino ground pin to my external power supply's ground or will this damage the board?  How can I end up with just one ground? Thanks.


texts: What is the function of Zener diodes in an astable multivibrator?

texts: I came across this schematic in my textbook which has back to back Zener diodes connected to the output of an astable multivibrator using op-amp which apparently varies the peak to peak output amplitude. Would really help if someone could provide a clearer explanation.


texts: charging super-capacitor with cosntant current

texts:
I want to charge a super-capacitor with a LiIon charger circuit like this one
http://www.mouser.com/ds/2/472/AAT3693_201896C-533711.pdf

Basically, capacitor is 50F (2 x 100F in series) and will be charged with constant current until 4.2V. I am not sure I calculate right the charge time, based on this:
Calculate charge time of a capacitor through a current limiting power supply?

Q = C * U = 50 * 4.2 = 210
t = Q / Ilim = 210 / 1.6A = 131.25s = 2.1875 minutes

For deep discharge (thanks @jms) will be 10% of current (0.16A) until trickle threshold (2.9V) enforced by charger. This will yields to 15 minutes according my calculations. (correct?)

Thank you


texts:
While trying to use Atmel's ASF library, they say

  __FPU_PRESENT:
  Initialize macro __FPU_PRESENT = 1 when building on FPU supported Targets. Enable this macro for M4bf and M4lf libraries

So I guess I need to check the datasheet if my uC, ATSAM4S16C AU has a floating-point unit and if so, define the macro before including the header inside my project.

But I can't figure the datasheet. Section 12.4.6 lists entries like

  VADD.F32    |   {Sd,} Sn, Sm |  Floating-point Add

However, no clock cycles indicated. Searching the document for FPU or F32 yields nothing. Checking the instruction, only ADD is documented, no VADD.32. So I do not know if this is computed in hardware or in software (in libm.a).

How do I know if the SAM4 has an FPU?


texts: I am designing the Vishay VCNL4010 proximity sensor into one of my PCBs. This sensor has an interrupt pin that I don't need to use. Is it OK to just leave this pin floating ("unconnected"), or will this cause problems somehow?


texts:
Is there a VHDL (or Quartus2-specific) compiler directive for disregarding certain lines of code for synthesis?

I want to have certain signals going out for my simulation, but Quartus2 throws errors about insufficient numbers of IC pins, and besides it would be more correct to not have them in the synthesized design.


texts: DRAM Self-Refresh not the Lowest Power Mode

texts:
I have a DDR3L Samsung DRAM on my Laptop. Based on page 23 of its datasheet, IDD6 or the Self-Refresh current is much higher than IDD2P0, IDD2P1 and IDD3P, which are the Precharge/Active Power-Down modes. Of course, IDD5B (i.e., the Burst Refresh current, which is responsible for refresh when Self-Refresh is not used) should be scaled based on the refresh period and added to the latter three values. But, even after that, it seems that the Self-Refresh power mode, is not the deepest power mode in this DRAM device. Am I missing something?

UPDATE:
This is a simplified state diagram of a Micron 1Gb DDR3 SDRAM device.

There exists a Refreshing and a Self-Refresh state. Periodic refreshes during normal device operation are done in the former state. Self-Refresh is a low power mode (similar to Precharge Power-Down, etc) in which no I/O is possible and any exit from this mode requires a relatively long resynchronization delay.
Here is a figure from IAMEM: Interaction-Aware Memory Energy Management:

As can be seen, Self-Refresh is the deepest power mode and has a small power consumption of 22mW. But in the Samsung DRAM that I mentioned at the beginning of the post, Self-Refresh does not seem to be the deepest power mode (based on the current values in the referenced datasheet). This seems counter-intuitive.


texts: Limiting the speed of an induction generator

texts:
A turbine (whose angular speed must not exceed \$\omega_{max}\$) is driving a 3-phase induction generator.

I envisage the generator's electrical output being monitored by a circuit that reacts to frequency \$f\$ approaching \$\frac{\omega_{max}}{2\pi}\$ by manipulating the generator's electrical load (and/or introducing power) in order to induce a "braking" EMF.

If power is introduced, it must only resist the turbine's mechanical drive—and never drive the turbine itself.  Therefore, because the fluid flow that actually drives the turbine is erratic (and could cease at any moment), any applied power must instantly respond to fluctuations in the mechanical drive.

Could this approach work?  Does it already exist in reality and/or have a name?  Are there any limits to the braking torque that a given such system could deliver?  How might the control circuit look?


texts: Identify small black cubic component with 2 pins

texts:
I found this component between my supply of resistors, motors, Arduino etc: (ruler for scale)

It is a small black cuboid (.4cm x .4cm x .2cm) with 2 pins (1.7cm) connected to it. On the front face is written in white:

2C1
100V
83 26

On the top:

470pK

Does somebody know what component this is and what the numbers written on it mean?


texts:
Good day.

I created schematic with diode on it:

But on board are anode and cathode connected.

I dont understand why.

Thanks.

Update:

Full schematic:


texts: VHDL Finite State Machine Pattern Checker

texts:
I'm trying to write some vhdl that detects a given pattern in a string of bits. The circuit should output 1 when it finds the pattern "110" in the input stream. My input is "X" and my output is "Z".

For some reason when I simulate the results, I'm not getting any output for "Z". It just stays low. This is what I have so far:

library IEEE;
 use IEEE.STD_LOGIC_1164.ALL;

 entity checker is
     Port ( clk : in  STD_LOGIC;
            x : in  STD_LOGIC;
            z : out  STD_LOGIC);
 end checker;

 architecture Behavioral of checker is

 type state_type is (S0, S1, S2);
 signal pr_state: state_type := S0;
 signal nx_state: state_type := S0;

 begin

 process(clk) begin
     if (rising_edge(clk)) then
         pr_state <= nx_state;
     end if;
 end process;

 process(pr_state, nx_state) begin

case (pr_state) is

    when S0 => z <= '0';
        if (x = '1') then
            nx_state <= S1;
        else
            nx_state <= S0;
        end if;

    when S1 => z <= '0';
        if (x = '1') then
            nx_state <= S2;
        else
            nx_state <= S1;
        end if;

    when S2 => z <= '1';
        if (x = '0') then
            nx_state <= S0;
        else
            nx_state <= S2;
        end if;

    when others => z <= '0';

end case;

 end process;

 end Behavioral;

Any thoughts? Appreciate your feedback.

Test bench Code:

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;

ENTITY checker_tb IS
END checker_tb;

ARCHITECTURE behavior OF checker_tb IS

-- Component Declaration for the Unit Under Test (UUT)

COMPONENT checker
PORT(
     clk : IN  std_logic;
     x : IN  std_logic;
     z : OUT  std_logic
    );
END COMPONENT;

    --Inputs
   signal clk : std_logic := '0';
   signal x : std_logic := '0';

--Outputs
   signal z : std_logic;

   -- Clock period definitions
   constant clk_period : time := 10 ns;

   BEGIN

-- Instantiate the Unit Under Test (UUT)
   uut: checker PORT MAP (
          clk => clk,
          x => x,
          z => z
        );

   -- Clock process definitions
   clk_process :process
   begin
    clk <= '0';
    wait for clk_period/2;
    clk <= '1';
    wait for clk_period/2;
   end process;

   x_process :process
   begin
    x <= '1';
    wait for 100ns;
    x <= '1';
    wait for 100ns;
    x <= '0';
    wait for 100ns;
   end process;

   stim_proc: process begin
  wait for 100 ns;
  wait for clk_period*10;
  wait;
   end process;

END;


texts: How to calculate RPM, given timer frequency and counter on STM32

texts:
on my STM32F103, I use a timer to read rotary encoder

Prescaler = 71
Period = 20
Clock = 72MHz
Rotary encoder: 2000 ppr

Given the formula:

TIMUpdateFrequency(Hz)=Clock/((PSC−1)∗(Period−1))

I obtain an update every 54'135Hz
Each update, I read the encoder value and compare to the previous one. Very stupid question: how can I get à RPM figure with that?


texts: Ac suppy provide to dc ammeter then what is the result

texts: Suppose if 220v and 50Hz voltage provide to DC ammeter then what will shows output?


texts: relationship between frequency and signal strength

texts:
I know that [the commercial broadcast] radio spectrum is divided into several chunks and each chunk is assigned to be used by different radio stations. Suppose that radio station S1 is using 93MHz and radio station S2 is using 94MHz. My question is, which radio station's signal strength is higher? As far I know:

signal strength is high if wavelength is high
wavelength is low if frequency is high
So signal strength is low if frequency is high

Is my understanding correct? If so, why would some radio stations pick a higher frequency? Is there a competition among companies to acquire lower frequencies? I am a computer science student and only have a bit of knowledge in signals.


texts: I want to build an oscilloscope preamp and wonder what sort of op amp should I use? What's the maximum input level a smartphone can handle and should I bias the signal (for instance -5V/+5v to something like 0-1V)? What means of circuit protection should I use? Can I use diodes?


texts: Eagle create custom size SMD pad for new library part

texts:
I am working on new Eagle part in custom library on page 7 of its datasheet there are visible dimension of IC:

The part is SMD and how I create custom pad sizes for this element using Eagle? I've created Polygons:

but Polygon is not (SMD) PAD on a Top Layer.


texts:
I'm trying to replace an avalanche photodiode board + external voltage amplifier combination that suffers from RF pickup due to cabling between the diode and the amplifier as well as low bandwidth due to the 50 ohm termination with a single board that has the diode on one side (behind an optical system) and the amplifier and electronics behind/around the diode.  By putting them close, I think I should be able to greatly reduce cable capacitance and RF pickup.  I've designed a simple transimpedance amplifier by looking at some reference TIA designs people have used for similar diodes and then reading the TI manuals:

The amplifier takes a 350 pF source diode and provides 750 ohms transresistance.  The target bandwidth is 50 MHz, and I using the OPA847 with 3.9 GHz GBW product.  The TI manual gives a feedback capacitance of 6.2 pf for this configuration.  On the right side of the schematic is a diode (in this case drawn as BJT because the pin out matched a stock model in Altium) and some filtering capacitors on the bias (provided between pins 1 and 2).  Pins 3, 4 and 5 on the connector J1 provide the +/-5 and GND required by the TIA.  I used larger 1206 SMD parts because I expected to have to resolder around mistakes and because the source capacitance is already large and the bandwidth relatively low.

Here are the layouts I came up with on FR4 using a 2 sided, 1" diameter PCB.  Front (diode) side with the dead space filled in and grounded (left) and omitted for clarity (right):

Back (opamp/connector) side:

I've never designed something with more than a few MHz bandwidth, so I have a few questions:

Should I be using seperate grounds for the Opamp and Bias circuits?  I debated cutting out the area around the high voltage bias circuit (C3, C4, R5, labeled 'diode bias') to isolate it from the amplifier, but I have no idea if this matters or is even a good idea.  Right now separate ground wires are provided, but I would short them externally to the board.  I will be using an external ultralow noise power supply to drive the avalanche diode through connector pins 1+2 at around 50v.  Edit:  Answer was YES.
How bad is my layout and how can I improve it?  I am concerned that I had to route the output of the amplifier in the gap between the filter capacitor terminals on capacitor C1 (amplifier positive supply voltage, green box).  Is that as bad an idea as it seems?  Size was very limited by the diameter of the optical system it fits into, but I could use smaller 0805 or 0603 parts if necessary.
The decoupling capacitors on the OPA847 were copied from another design with this opamp.  They seem to work, but I am open to suggestions if they are not correct.

Edit

Revised design with the merged ground planes.  This greatly simplifies routing.


texts: LED-strip PWM works with Raspberry Pi, doesn't work with Attiny45

texts:
I'm trying to control an RGBW analog LED-strip by PWM modulation.

When using an Attiny45 the LED-strip just blinks at a low frequency (approx. 2-3 hz). However, using a Raspberry Pi 3 to control PWM works without a problem, and at any frequency of PWM I try.

Any ideas as to why that could be?

Additional information

In my test setup I power the Attiny45 by connecting to the 3.3V pin on the Pi (for now, will change later).

I have programmed the Attiny45 via SPI on the Pi using the Avrdude linuxspi module, following this instructable.

The setup is the same for both tested controllers:

The control pin with PWM output drives a MOSFET (IRLZ34NPBF), which connects one of the color leads on the strip to ground (which is connected to the Pi's ground).

An external power supply, rated for use with my LED-strip powers the strip, with the ground connected to the Pi's ground.

I have tried all different PWM frequencies on the Attiny45 (by default clocked at 8MHz, so I shouldn't even see a flicker on the lowest PWM frequency, which is 8MHz/(256*1024)=~30.5Hz (according to the official Datasheet, page 74)) and the same frequency on the Pi, which works without flickering.

The Attiny45 can drive a single LED using the same MOSFET setup without flickering.

Schematic:

simulate this circuit – Schematic created using CircuitLab

I tried adding a small value resistor (R1, 620Ohm) between gate and source of the MOSFET to counteract a floating state when the PWM is off, but it doesn't make a difference.

I'm looking forward to your input!


texts: Tuning a potential sensor using a source-follower MOSFET

texts:
I am interested in building a simple but sensitive setup that would allow me to detect small potential changes (adsorption of ions) on the surface of the gate of a MOSFET - what is commonly referred to as an extended gate FET.

As a reference, see for example this figure from a research article (Song et al, Phys Rev E, 2006):

The idea is to shift Vth and detect that change because Vgs remains identical.

The extension of the gate is in contact with a solution containing the analytes, and the bias is provided at a reference electrode in the same solution.

From what I have understood, a common drain amplifier seems to be the best option to have a straightforward relationship between Vg and the measured Vs. A large resistance (R) is used to maximize the voltage drop across R. Stop me if anything makes no sense here.

I am unsure as to how to choose the MOSFET and the various parameters for maximal sensitivity and dynamic range. Importantly I want to use an "almost low-cost" equipment so I cannot observe current changes (usually very small) but rather changes in voltage at the source. Let's assume for the sake of this question that I have a good ADC.

My questions are therefore:

How to rationalize the choice of the hardware? For example, would it make any difference to use a depletion or an enhancement mode MOSFET (except for the fact that the signal would go up vs down, which I don't really care about as long as it changes)?
How to set Vd and Vg to make sure that changes are detectable? Initially I thought I would set Vd to a small value (but not too small, to preserve a decent dynamic range, my ADC operating in the 0-2.5V range it would be great to use the whole range) and then choose a somewhat arbitrary gate voltage above Vth, so that any change in Vgs would cause a change in Id, and therefore a change in Vds; as the drain potential is imposed, I would read a difference in potential at the source. But I also guess there must be some "ideal" set of conditions for that, which I cannot figure out. For example, should I operate in the saturation or the triode/linear mode?
Which brings me to the big general question: How can I know a priori in which region I'm operating and what my device's characteristic voltages are, since I expect the source potential to be variable, and therefore Vds and Vgs to change in potentially unexpected directions?

Thank you for any advice or comments on this question!


texts: Sallen key topology choosing right op-amp

texts:
Welcome all. I designed Bessel low pas filter using Analogue Devices filter wizard. It is a fantastic toll saving loads of time. However, like any tool has its limitations. Upon completion my design I checked datasheet for suggested filter. Sadly, one of parameters voltage offset drift is bit higher than I can accept (2.5uV/*C). Therefore, I am looking for precision op-amp however not sure how to approach swapping AD8642 for precision op amp. What spec should I prioritize? Currently critical spec I am looking at is Gain bandwidth product, supply voltage and offset temperature drift.
Also, can anyone explain flatness of a response between 100KHz and 80MHz? Usually in this type of filter I observed roll-off and peaking and high frequency rather than flat response.


texts:
We know the typical equation for instantaneous power (which can be proven): \$p(t)=v(t)i(t)\$. In sinusoidal steady state (let's ignore harmonics for simplicity), \$v(t)=\sqrt{2} V_{\text{rms}} \cos{(\omega t + \phi_v)}\$ and \$i(t)=\sqrt{2} I_{\text{rms}} \cos{(\omega t + \phi_i)}\$, where \$\omega\$ and \$T = 2 \pi / \omega \$ are respectively the angular frequency and period of \$v\$ and \$i\$. From this, letting \$ \theta = \phi_v - \phi_i\$, it can be shown that
\$ \begin{align} p(t) &= \underbrace{\left[ V_{\text{rms}} I_{\text{rms}} \cos{(\phi_v - \phi_i)} \right]}_{\text{DC component}} + \underbrace{\left[ V_{\text{rms}} I_{\text{rms}} \right] \cos{(2 \omega t + \phi_v + \phi_i)}}_{\text{AC component}} \tag*{} \\ &= \underbrace{\left[ V_{\text{rms}} I_{\text{rms}} \cos{\theta} \right]}_{\text{unidirectional}} + \underbrace{\left[ V_{\text{rms}} I_{\text{rms}} \cos{(\phi_v + \phi_i)} \right] \cos{2 \omega t} - \left[ V_{\text{rms}} I_{\text{rms}} \sin{(\phi_v + \phi_i)} \right] \sin{2 \omega t}}_{\text{bidirectional}} \end{align} \$
where \$2 \omega\$ and \$T' = 2 \pi / 2 \omega = T/2\$ are respectively the angular frequency and period of \$p\$. Now, since \$p(t) \overset{\text{def}}{=} dw(t)/dt\$, then the energy transferred in an integer multiple \$n\$ of the period of \$p\$ is
\$ \begin{align} W &= \displaystyle\int_0^{nT'} p(t) \, dt \tag*{} \\ &= \underbrace{P \displaystyle\int_0^{nT'} \, dt}_{\text{net energy}} + \underbrace{V_{\text{rms}} I_{\text{rms}} \cos{(\phi_v + \phi_i)} \displaystyle\int_0^{nT'} \cos{2 \omega t} \, dt - V_{\text{rms}} I_{\text{rms}} \sin{(\phi_v + \phi_i)} \displaystyle\int_0^{nT'} \sin{2 \omega t} \, dt}_{\text{no net energy}} \\ &=
P \cdot n \cdot T' + 0 \end{align} \$
It's clear that there's no net energy transferred due to the reactive component of a load impedance. However, I've seen three documents (this webpage in section 1.7, this PDF in page 2, this PDF,) talk about reactive energy and their corresponding meters. Since, as shown above, there's no net energy transferred due to the reactance of loads, what energy do those meters actually read? If it's "reactive energy", what do they mean by that? Two documents I found define reactive energy mathematically as
\$ \dfrac{1}{T} \displaystyle\int_0^{T} v(t) i \left( t+\dfrac{T}{4} \right) \, dt =  Q \tag*{} \$
which is non-sense; they're defining reactive energy as reactive power, which is a different quantity; energy has units of joules, yet the right-hand side of the previous relation has units of joules per second (or watts or VArs; they're dimensionally the same). Why do they define it as such? I read these three questions (1, 2, 3), but they don't really address the ones I've asked.
EDIT: My questions are not directly about reactive power, but about reactive energy.


texts: Why does color of addressable RGB LED strip change when dimming?

texts:
TL;DR
I have an addressable LED strip with TM1814 IC's. (So it's actually a RGBW strip. Download datasheet here.) When set to orange at full brightness, it's orange. But when set to orange at 10%, it becomes red. If I were to redesign the schematics of the LED strip, there a hardware fix? Or should the solution be found in software (gamma correction)?
Longer story:
I have two addressable LED strips:

With SK6812 LEDs (similar to WS2812, upper one in photo)
With TM1814 IC's and separate RGBW LEDs (lower one in photo)

I know it's hard to see on the photo above, but on the left you can see 20% orange (R=26, G=7, B=0, W=0) and on the right 100% orange (R=255, G=70, B=0, W=0). On the upper SK6812 LED strip you see that the color is the same, and that the left part is just less bright. On the lower TM1814 LED strip, you see that the left side is not just less bright, but just has a different color. It's more red than orange. I don't want it to be red, I want it to look orange, but less bright.
The problem can be fixed by using gamma correction on the red channel in software. So when going from (R=26, G=7, B=0, W=0) to (R=19, G=7, B=0, W=0) the overall orange color is better (not so red anymore).
Although it is possible to create a nice gamma correction curve, I was wondering if there is also a hardware fix for this problem? Is it because of the choice of RGBW LEDs?
Download the TM1814 IC datasheet here.
I hope someone can help me out! Thanks in advance.
For reference, here is a photo and a typical schematic of the LED strip:


texts: I see some SMT wire wound inductors are named like 3R3 or 4R5, much like a resistor, why so? I expected them to be like 4H5.


texts: STM32F100RBT6 basic initialization code does not work

texts:
I have been currently working with the HAL libraries but I got fed up with it and want to access registers and make better use of the uC itself. So, I have a code that should blink a LED and I have assigned all the necessary bits in order to do so, but it does not work as intended and I don't know why.
Here is the code:
#include "stm32f10x.h"

int main()
{

    // initialize the clock for Port C
    RCC->APB2ENR |= (1<<4);  // enable clock for GPIO C ( check it on memory and bus architecture)
    // set pin 9 of GPIOC to output mode
    GPIOC->CRH |= ((1<<4)|(1<<5)); // PC9 pin will be used as an Output at max speed = 50 MHz
    GPIOC->CRH &= (unsigned int)~((1<<6)|(1<<7)); // output mode in push-pull configuration (set 11 to CNF bits), that is, General Purpose Output
    int i;
    while(1)
    {
        for(i=0;i<=5000000;i++);
        GPIOC->BSRR = (1<<9);
        for(i=0;i<=5000000;i++);
        GPIOC->BSRR = (1<<(9+16));

    }
}
                // keil requires you to leave an extra line after the last bracket

I set APB2ENR which controls GPIOs and CRH in order to set PC9 as output and push-pull mode.
My MCU clock works at 8 MHz and I have set i<=5000000 in my for loop and it the output does not respond accordingly.
The output on the other hand (PC9) is a random signal switching at 5 MHz. Unfortunately I have no pictures to show the results.
So, have I forgotten any initialization code?
Thank you in advance.


texts: It is a typical picture of a shift register. Assuming initially the clock is off, and serial input=1. After a while clock turns on, and immediately Q_2 becomes D_2=1, but since the clock is common to all flip flops, Q_2=1 means D_1=1, and Since the clock is still on D_1 SHOULD BE EQUAL TO Q_1, so, D_2=Q_2=D_1=Q_1=1, Similarly in can be shown that just after one clock pulse the serial input=1=serial output, which is not how the shift register should work. What is missing here?


texts: Shut off circuit when under a certain voltage?

texts:
I have three batteries wired in series, in order to produce 9v. If one of those batteries dies, I need the whole circuit to shut off. The best solution I've found is to use a comparator, but the problem with that is that it requires a separate 9v source in order to have something to compare the voltage with. However, if this second 9v source dies off, the circuit will always let power through, which is not what I want.

Is there a way to shut off a circuit when it goes below a certain voltage?

Thanks!


texts:
The manual for my new laptop clearly states that partial charge cycles of it's (Li-Ion) battery should be avoided. It recommends to always discharge to automatic shutdown and then charge back to 100% in order to prolong battery service life.

What could be the reason for this recommendation?

Are there circumstances where this would make sense?

Update

The (english) manual can be found here: http://download2.medion.com/downloads/anleitungen/bda_40055298.pdf

In section 7 on page 23 it says: "The battery should always be completely discharged before charging and then fully charged again to optimise the service life and performance"

Interestingly, I found there's a software pre-installed that allows me to set upper and lower SoC limits where to stop/start charging automatically.


texts: Trying to multiplex voltage reference gives incorrect output

texts:
I'm trying to make the voltage reference for an INA214 opamp selectable between GND, 4.5V and 10V. I'm using a CD4051B multiplexer.

However, the 10V VREF gets pulled down to 5.84V, and I can't figure out why.

simulate this circuit – Schematic created using CircuitLab

CD4051B has:

INH, Vee, Vss to GND
C to GND
A, B to 5V (thus selecting CH3 as output)
CH3 to GND
CH1 to D1 output
CH2 to D2 output
Output measured by multimeter

Output measures:

4.95V when D2 is connected to any pin on the mux
0V when D2 is not connected
4.54V when B is GND, no matter if A is 5V or GND (D2 is not connected)

which is strange, because CH1 is A=1 B=0.

What is going here? Are the TL431s interfering with the function of the CD4051B, or...?

By the way, am I required to connect the other pins/channels to ground, or can they be floating?