texts: Using method of image to find potential difference and electric field

texts:
A point charge of 10nC is located at point P(0,0,3) while the conducting plane z=0 is grounded. Calculate
a) V and \$\vec E\$ at R(6,3,5)
b) The force on the charge due to induced charge on the plate.
Here, I used the method of imaging. At first 10nC charge on the \$z=0\$ plane at \$(0,0,3)\$ and then assuming a -10nC charge at \$(0,0,-3)\$ I calculated V, at \$(6,3,5)\$.
For \$10nC\$, \$\begin{align}\\
\vec R_1&=(6\hat a_x+3\hat a_y+5\hat a_z)-3\hat a_z\\
&=6\hat a_x+3\hat a_y+2\hat a_z\\
\end{align}\\\$
For \$-10nC\$, \$\begin{align}\\
\vec R_2&=(6\hat a_x+3\hat a_y+5\hat a_z)+3\hat a_z\\
&=6\hat a_x+3\hat a_y+8\hat a_z\\
\end{align}\\\$
\$\begin{align}\\
V&{\begin{aligned}\\
=\frac{1}{4\pi\epsilon_0}\frac{10\times 10^{-9}}{\sqrt{6^2+3^2+2^2}}&-\frac{1}{4\pi\epsilon_0}\frac{10\times 10^{-9}}{\sqrt{6^2+3^2+8^2}}\\
\end{aligned}\\}\\
&=4.23V\\
\end{align}\\\$
And
\$\begin{align}\\
\vec E&{\begin{aligned}\\
=\frac{1}{4\pi\epsilon_0}\frac{10\times 10^{-9}}{(6^2+3^2+2^2)^{3/2}}(6\hat a_x+3\hat a_y&+2\hat a_z)-\frac{1}{4\pi\epsilon_0}\frac{10\times 10^{-9}}{(6^2+3^2+8^2)^{3/2}}(6\hat a_x&+3\hat a_y+8\hat a_z)\\
\end{aligned}\\}\\
&=1.1\hat a_x+0.55\hat a_y-0.108\hat a_z\\
\end{align}\\\$
The force on the charge due to induced charge on the plate\$\begin{align}\\
&=-\frac{1}{4\pi\epsilon_0}\frac{(10\times 10^{-9})^2\times 6}{(3+3)^3}\hat a_z\\
&=-2.5\times 10^{-8}N\hat a_z\\
\end{align}\\\$
But, in my book answer is \$-25N\hat a_z\$. Which one is correct? Please anyone confirm  it.


texts: Understanding Proper Implementation Of Open-Collector

texts:
I am confused about the implementation of an open-collector circuit. From what I've read, there are many ways to incorrectly wire up an open-collector circuit. Before I explain my confusion, let me explain how I understand the term open-collector:

My Explanation Of An Open-collector:

The output of an IC is connected to a transistor. The base is connected internally to the circuit, the emitter is connected to ground and the collector is connected to the output pin (hence open-collector)

Therefore, the main purpose of the IC is to sink current externally and not to source current

My Confusion:

I've read from an article online that the proper way to implement the function of an open-collector is in the attachment of the image below:

This is basically a Quad, 2 input AND open-collector. It works and functions like a AND gate. 1A and 1B represents Input A and Input B respectively and 1Y represents the Output.

However, the textbook I am using takes a different approach as such:

This is a NAND gate. I am really confused about this implementation as it defies the truth table of a basic NAND gate. If both the inputs are high the output is HIGH, otherwise, the output remains LOW for all other inputs. This would be the traits of a typical AND gate.

I need some help clearing up my confusion as to why my textbook took that approach. Is my 74LS09 circuit configured the correct way?


texts:
The circuit is designed to control the power to a load via a single momentary push button switch.

K1 and K2 are miniature DPDT relays with dc12v coil resistance of 1.2k ohm. K2 coil is time delayed via the external resistance and capacitance.

If the push button is pressed momentarily K1 should turn on and stay on. When the push button is held longer than certain time constant, K2 will turn on and drop the K1.

The question is how do I determine proper values for R and C if the required long press is about 1.5 second?

Simple RC time constant doesn't seems fit because of the influence of the K2 coil resistance.


texts:
So, Im wireding this

Edit:
Everyone switch ON for good reading

And the output is the green leds of each protoboard, 2bits for each protoboard, and with those bits, I have to do a "AND" or "OR" so, to do that, 1 bit of my switch is connected to a NOT, in order to send voltaje to the 7432 or 7408, depends on that bit... The AND is working perfectly, but the OR isn´t

Green cable, input for 7432(Not working as expected)
Yellow cable, input for 7408(Works fine)
Blue cables, output of each result
Large Yellow/Orage cable voltaje to each logic gate
So, on the 7432 I have a input of 0´s(from the green bits) and the output is 1, as far as I understand, this is sendind 0´s, so the output should be 0, but only if I connect ground directly outputs the correct bit.

Status input: 0-0 / 0-0
excpected output: 0-0

red led indicates which logic gate is on

I add a NOT that is not connected, since this emulator do not recreate the logic gate, this NOT is the one who allow the "AND" or "OR" to turn on(Large Yello and Orange cables or the red LED)


texts: I recently bought two XBee Series 2 Pros, and I want to increase the range on them. I found an appropriate 2.4GHz antenna with a U.FL connector. I already have one XBee with a U.FL connector and from what I can tell the PCB layout is exactly the same except for the absence of the connector. Would I be able to remove the two wire antennae and solder U.FL connectors on and use them instead?


texts:
I want to create an Led Cube 4x4x4 with an ATMEGA 16 chip.
Because is my first electronic project, I connect leds on layers(horizontally) with     common anodes and vertically with common cathodes.

Can you tell me please, what's the differences and how can I continue(if is possible)?
I have bought 16 resistors of 220 ohms and 4 transistors 2N222 instead of BC337. Can you tell me, please, if I can use these components without recreate the Cube?
Thank you.

Edited:
This is the schematic I followed at the beginning of the project but now I don't know if is possible anymore.I'm sorry that isn't in that format, but it takes a lot of time to add all leds and pins of uC.


texts:
I want to interface an encoder based on the SSI interface with a microcontroller and only an SPI interface is available (I can't use other interfaces than SPI). As far as I see, SSI has a lot in common with RS422. I wonder if it is possible to convert RS422 to SPI.
What do I mean?
I would connect CLK to DI, MISO to RO and CS to DE and RE with a transistor which allows to put two elements into High-Z state at once.
The IC below is a MAX491.

Is it possible at all? What do you think?


texts: Butterworth and Chebyshev filter problem

texts:
Find the minimum order Butterworth lowpass filter whose attenuation isn't bigger than 2 dB at 5 rad/s and has 10 dB at 8 rad/s, 20 dB at 10 rad/s, and 40dB at 30 rad/s, then do it for Chebyshev filter.
$$
\omega_p=5 \frac{\mathrm{rad}}{\mathrm{s}}\,,\,
\omega_1=8 \frac{\mathrm{rad}}{\mathrm{s}} \,,\,
\omega_2=10 \frac{\mathrm{rad}}{\mathrm{s}} \,,\,
\omega_3=30 \frac{\mathrm{rad}}{\mathrm{s}} \\
A_p=2 \mathrm{dB} \,,\,
A_{s_1}=10 \mathrm{dB} \,,\,
A_{s_2}=20 \mathrm{dB} \,,\,
A_{s_3}=40 \mathrm{dB}
$$
$$\begin{align}
A_p&=10\log(1+\varepsilon^2-1) \\
\varepsilon^2&=10^{\frac{A_p}{10}}-1=10^{\frac{2}{10}}-1=0.5849 \\
A_s&=10\log(1+\varepsilon^2 V_s^{2n} ) \\
n&=\frac{\log\sqrt{10^{\frac{As}{10}}-\frac{1}{\varepsilon^2 }}}{\log V_s} \\
n_1&=\frac{\log\sqrt{10^{0.1*12}-\frac{1}{\varepsilon^2}}}{\log\frac{8}{5}}=2.8\rightarrow 3 \\
n_2&=\frac{\log\sqrt{10^{0.1*22}-\frac{1}{\varepsilon^2}}}{\log\frac{10}{5}}=3.6\rightarrow 4 \\
n_3&=\frac{\log\sqrt{10^{0.1*42}-\frac{1}{\varepsilon^2}}}{\log\frac{30}{5}}=2.6\rightarrow 3
\end{align}$$
I think I got Butterworth results OK, but how do I do Chebyshev?


texts:
I have a datasheet of a CD74HCT86E XOR gate. Under Absolute Maximum Ratings, it says

  DC Output Source or Sink Current per Output Pin, IO

  For VO > -0.5V or VO < VCC + 0.5V . . . . . . . . . . . . . . . . . . . .±25mA

How should I interpret this? I'm thinking of two options:

Make sure that the sink or source current never exceeds 25mA. However, then I'm wondering why there are specifications on the output voltage: I should think these voltages follow from the current draw and the output impedance - you can't have a current independent of output pin voltage
Make sure VO never goes below -0.5V or above Vcc+0.5V. As long as this is the case, the device will not source or sink more than 25mA. Do not exceed these voltages, or the device will sink/source more than 25mA, and magic smoke will happen.

Which is it?


texts:
From a fundamental/general perspective I am looking to better understand why parallel diode clippers work the way they do. I understand in general how parallel configurations work (such as voltage is shared across each branch, but each can have varying current).

Where I am getting confused is that I thought the voltage shared among each branch is defined by the voltage beginning at the start of the branch.

However, in the case of a simple forward-biased diode (silicon, 0.7V) in parallel with a load resistor, the voltage across the load resistor matches that voltage drop across the diode, in this case 0.7V.

Why exactly is the voltage across the load "clipped" by the diode instead of being the voltage from the source less the current limiting resistor?

***EDIT: I apologize my question isn't clear. I have a lot to learn! I have attached an image below which hopefully will clarify what I am looking at. A diode is in parallel with another load resistor, with a current limiting resistor in series.  I suppose what I am attempting to figure out is why the diode limits the voltage drop across the load resistor to 0.7V, regardless of the value of the resistance of the load resistor.


texts: Current and voltage dividers with multiple sources

texts:
In a practice problem for my ECE class I am told to use a voltage divider to find \$v_1\$ in the circuit below

And to use a current divider to find the \$i_1\$ in this circuit

I am given the answer to each problem as these are just for practice, and so I know that \$V_1=2V, i_1 = 27mA\$ And I know the formula for a voltage divider or current divider as

For n resistors in series: \$V_n = V_{total}(\frac{R_n}{R_1+R_2 + ... + R_n})\$

For n resistors in \$\parallel\$ : \$i_n = i_{total}(\frac{G_n}{G_1 + G_2 + ... G_n})\$ Where \$G\$ is conductance is \$\frac1R\$

I have tried to use these formulas, but I don't know what to do when there are multiple sources in a circuit. I could use a KCL or KVL to analyze the circuit but I'm asked specifically to use a divider.


texts: How do you make crossing wires not connect in EAGLE?

texts:
I am brand new to PCB designing (started yesterday) and am doing it as a fun little side project. My goal is to produce a working PCB that has a very basic function. My problem is this:

I have no idea how to make wires (I think called a net in EAGLE) "cross" without connecting to each other. I was thinking of having little soldering hole type things either side of the wire (the one that is part of the PCB), and soldering another wire to them to jump over the other wire inside the PCB (hopefully, that made sense), but I would have to have 100 holes and 50 wires for this project.

I was wondering if there is a much more efficient way of doing this? I have heard the term "Air Wires" thrown around a lot but I do not know if this is what I need, as well as double-sided PCBs. At the moment I am using a single-sided PCB but that can change

Edit: Sorry I am bad with terminology for things like this. I have tried to make it more clear but please point out any mistakes I have made or if you need any clarification.


texts: Why does my power supply show a signal on the oscilloscope when off?

texts: Oscilloscope shows a sinusoid V(RMS)=1.67V and V(MAX)=2.48V. I have a GW INSTEK GPS-3303 power supply and a RIGOL DS1052E oscilloscope. The supply is in series tracking mode, with the probe directly connected to the negative CH1 and ground of the probe connected to ground of the supply. The "output" button of the supply is in the off position. Master V=6.9V and I=1.06A.


texts:
I am trying to read analogic signal for a sort of mouse with a pic18f14k50 controller. Here the simple circuit: http://dl.dropbox.com/u/14663091/schematiconew.pdf . I have to read analogic signal from AN9 circuit port. Main function reads from the port, and blinks 30 time if threshold is reached:

void main(void)
{
    InitializeSystem();

    #if defined(USB_INTERRUPT)
        USBDeviceAttach();
    #endif

    while(1) {

        if ((USBDeviceState < CONFIGURED_STATE) || (USBSuspendControl == 1)) continue;

        if (!HIDTxHandleBusy(lastTransmission)) {
            int readed = myReadADC2(); //Here i tried both myReadADC2() or myReadADC1()
            if (readed > 40) { //If read threshold > 40, blink led 30 times
                int i;
                for (i = 0; i < 30; i++) {
                    Delay1KTCYx(0);
                    mLED_1_On();
                    Delay1KTCYx(0);
                    mLED_1_Off();
                }
            }
        lastTransmission = HIDTxPacket(HID_EP, (BYTE*)hid_report_in, 0x03);

        } /* [Ed: added] */
    }//end while
}//end main

I used two method to read from the AN9 port, myReadADC() that uses OpenADC() API method:

int myReadADC(void)
{
    #define ADC_REF_VDD_VDD_X 0b11110011
    OpenADC(ADC_FOSC_RC & ADC_RIGHT_JUST & ADC_12_TAD,
            ADC_CH9 & ADC_INT_OFF,
            ADC_REF_VDD_VDD_X & ADC_REF_VDD_VSS,
            0b00000010); // channel 9
    SetChanADC(ADC_CH9);
    ConvertADC();                 // Start conversion
    while (BusyADC());             // Wait for completion
    return ReadADC();           // Read result
}

and myReadADC2(), that implements manual read from the port.

int myReadADC2()
{
    int iRet;
    OSCCON = 0x70;         // Select 16 MHz internal clock
    ANSEL = 0b00000010;  // Set PORT AN9 to analog input
    ANSELH = 0;          // Set other PORTS as Digital I/O
    /* Init ADC */
    ADCON0 = 0b00100101;   // ADC port channel 9 (AN9), Enable ADC
    ADCON1 = 0b00000000;   // Use Internal Voltage Reference (Vdd and Vss)
    ADCON2 = 0b10101011;   // Right justify result, 12 TAD, Select the FRC for 16 MHz
    iRet = 100;

    ADCON0bits.GO = 1;
    while (ADCON0bits.GO);   // Wait conversion done
    iRet = ADRESL;           // Get the 8 bit LSB result
    iRet += (ADRESH << 8); // Get the 2 bit MSB result
    return iRet;
}

Both cases doesn't works, i touch (sending analogic signal) port AN9 but when I set high threshold (~50) led don't blinks, with low threshold (~0) it blinks immidiatly when i provide power to the PIC. Maybe i'm using wrong port? I'm actually passing AN9 as reading port? Or maybe threshold is wrong? How can i found the right value? Thank you

Here the MPLAB C18 Apis http://dl.dropbox.com/u/14663091/API%20microchip%20C18.pdf .


texts: What do I need to look out for when selecting a relay for switching audio channels

texts:
So I heard that when using DPDT relays for something related to audio I would need to look out for what exactly to get so I don't have humming or other electrical noise while the device is in use.
The relay would be used to switch an analog signal coming from a PC between two analog audio outputs
What is it I need to look out for so I don't get electrical noise or humming?


texts:
Is it true that transformer's oil shouldn't be circulated (for cooling) cause it will change its properties and may cause a failure in isolation, if so does water cooled transformers has a special oil or two separate oils ( one in the core for isolation and one in the shell for cooling) ?
( the oil is cooled by heat exchanger by water )


texts: Operating Temperature Range question for Inrush Current Limiting Thermistors

texts:
I have a friend who has brought me a circuit board from her flat screen TV. She assumed it was bad because the TV no longer turns on and there was off-white stuff leaking out of some of the components. When I got the board, the off-white stuff turned out to be that adhesive they use in asia to secure components, so I explained this to her.

But I did notice something strange about the board. On one of the components, the off-white glue was blackened as if it were burnt. The component in question was marked DSC 5D-15... which turns out the be an Inrush Current Limiting Thermistor.

Now, I would expect this thing to get kind of hot, (being a thermistor) and I understand that it provides a different amount of resistance depending on what temperature it is (being a thermistor). But should it really get hot enough to burn the glue?

I tried some tests on some glue I peeled off from another area of the board, and it took much more than the mean max operating temperature (280C) to make the glue burn or turn black.

She also reported that the TV wouldn't turn on until you repeatedly hit the power button... but after a few months of operation like this, it wouldn't turn on at all. I would assume that the action of repeatedly hitting the power button probably caused this inrush thermistor to stay hot and therefore, not protect anything any more.

I was hoping I could just replace the inrush thermistor (if it is damaged). But I suspect there is more damage than this. Currently, I only have the Power supply board.

So, my question is, should the thermistor get hot enough to burn asian component glue? And also, any suggestions on how I can test the thermistor to verify if it is working? And any other suggestions would be appreciated.


texts: Eagle automatically making connections to layers of PCB?

texts:
I'm designing a 4 layer PCB, using positive and negative power planes along with a ground plane and a top signal layer. While making the schematic I've notice strange little Xs in some of the through holes of my through hole parts. Here is an example.

I'm wondering if the little cross in the middle of the through hole means that a connection is being made from pin 4 of this chip to the VS- layer. In other words, is the via connecting the VS- layer (layer 15) to pin 4 unnecessary?

Also, I know that the via shows up as a design rule violation. I need to change the minimum blind via ration for this board, and I'm not looking for advice about this.


texts: 3.3 powered microcontroller interface with 5V powered ADC

texts:
I want to use uC LPC1769 (3.3V powered) for interfacing with 5V or 3.3V powered ADC.

Controller --> LPC1769

ADC          --> AD7705

If we power ADC7705 with 5V, then Vref = 2.5V. But,
if we power ADC7705 with 3.3V, then Vref = 1.25V.

Since my application is biomedical instrument where sensor used is photo diode followed by op-amp as I to V converter,high precision is needed.
And I need wide range of analog input for optimum results.

CASE1:
If we keep both (uC and ADC) 3.3 volt powered, Vref=1.25V and analog input range is reduced and hence resolution also.

CASE2:
If we keep both (uC and ADC) 5 volt powered, Vref=2.5V and analog input range is higher than 3.3Volt case and hence resolution also better. This is preferable scenario.

What are possible configuration I can implement? Thanks in advance.


texts: Are harmonics going to be introduced if we add capacitor to correct the power factor of a plant?

texts: Suppose there are no harmonics in our installation,  will adding capacitors  introduce harmonics to our installation ?


texts: Input impedance of lossless transmission line

texts:
I'm having trouble understanding the following formulas (highlighted) and their corresponding solutions.

I first added up the impedance of transmission lines and found \$Z_{in}\$, but it seems to be wrong. Any explanation will be appreciated.


texts: Commutation of BLDC motors with respect to number of poles

texts:
I have a BLDC motor with HALL sensors. Datasheet reads the motor is 4 pole technology. Somewhere else it says "Number of pole pairs = 2". I can only assume that they both mean the same thing. It also features 3 HALL sensors at 120°

My question is, what would be fundamentally different in commutation of a BLDC motor with respect to the number of poles, like sequence or number of switching on/off for driver transistors?

For example, If I have a fully working code for a 6 pole or 8 pole motor, what would I need to do to make it work with 4 pole as well?


texts: Simple question about flow of electricity

texts:
I wanted to modify my power-on switch on my PC and decided to add few switches and LEDs before it powers up. Its more of an aesthetic modification but I have encounter one problem which is, shown in the diagram (red arow), will the negative part of the `battery have an effect on my motherboard power-on switch/port?

I mean I know the positive part wont touch the motherboard due to the LEDs but I have doubts about the negative part mixing up with the flow of electricity
`The "battery" comes from the motherboard USB port(It has power regardless of whether the PC is on, in standby mode or even off )


texts: Using VHDL code to design a JK Flip Flop

texts:
I'm using quartus II to design a JK Flip Flop. However, my results show unknown output. Why is it?

Intended design circuit:

VHDL code:

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

entity JKFlipFlopGate is
    port(
        J,K,Clk : in std_logic;             --JK Flip-Flop gate input 1 & 2
        Q,Qbar : out std_logic              --JK Flip-Flop gate output
    );
end JKFlipFlopGate;

architecture result of JKFlipFlopGate is
signal out1,out2,out3,out4 : std_logic;

begin
    out1    <= NOT(J AND Clk AND out4);
    out2    <= NOT(K AND Clk AND out3);
    out3    <= out1 NAND out4;
    out4    <= out2 NAND out3;
    Q       <= out3;
    Qbar    <= out4;
end result;


texts: I have a simple circuit as in the picture below. My question is why the negative charge -Q at the bottom plate of C1 moves and neutralizes with the positive charge +Q at the top plate of C2?


texts:
I am trying to connect a microcontroller(cortex m3) and a fpga(actel a3p060). I am able to read/write successfully with 16 bit databus. My modules in vhdl is structured as follows:

Top module(interface with controller)
sub module where I am having a frequency divider.

The idea is to generate different frequencies fed by the controller to the fpga. In the main module, I'm passing a signal called as the Load_Divider which will be checked in the frequency divider module as follows:

process(Load_Division)
if(Load_Division='1')
   Data_Buffer<=DataBus;
   Load_Divider <='0';
end if;
end process;

if(Counter = X"0000") then
   Counter <= Data_Buffer; //reloading counter

And in the main module :

case Address is
   "00100"=>Load_Divider <='1'; // generating load signal when proper address is found

But what happens is my Load_Divider is not going '0' when driven from the sub module.

Is it not possible to drive a signal from two modules?


texts: Why is U used for ICs on circuit diagrams?

texts: On circuit diagrams, C stands for Capacitor, R for Resistor, L for inductor (for Lenz) as explained here, but why is U used for ICs on circuit diagrams?


texts: So why do battery chargers need two prongs? Why not just one?

texts:
Electricity flows from area of highest electric potential to lowest, I get that. What I don't get is why any battery charger would use two prongs on an outlet (or a few other items of similar purpose). Hypothetically, it's a below fully charged state that's filling up. It should just have an intake and then once it's full, flip that off.

I've often been taught to envision electricity flow similar to water flow, flowing downhill from high potential to low potential... but when filling a bucket, we don't put holes in the bottom of buckets, so why do we need outflow for battery chargers?


texts: Why can't I use Ohm's Law on my circuit?

texts: In my circuit, I have 5V power supply and I have 200 ohm resistor. When I measure the current, it's 14.8 mA. Why can't I use the equation I = V/R, which is 5/200 =  25 mA?


texts: Calculate base current NPN high side transistor

texts:
Say I have this configuration:

simulate this circuit – Schematic created using CircuitLab
I want to calculate the current going to the base of the NPN transistor.
Specifically for PMBT3904,215 transistor, but I am trying to figure out a general rule for calculating the Ibase.
Because of R2 and the 0.7V voltage drop of the NPN and the 1.2V drop of the LED, the current will be I=(5 - 0.7 - 1.2V)/(100+400[Ω]) =6.2mA right?
I do not know if there will be any "surprises" for using the transistor on the high side.


texts: Discrepancy between calculated rectified voltage and measured value

texts:
I'm experiencing some problems with a simple task.
Assuming we have a circuit like this:

simulate this circuit – Schematic created using CircuitLab

To calculate the rectified voltage I'd use
$$U_{d} = \frac{1}{2 \cdot \pi} \cdot \int_{\alpha}^{\pi}{\hat{U} \cdot sin( \omega t) \cdot d \omega t}$$
or as mentioned here
$$U_{d} = \frac{1}{2 \cdot \pi} \cdot \int_{\alpha}^{\pi}{\hat{U} \cdot sin( \gamma) \cdot d \gamma}$$
$$U_d = \frac{\hat{U}}{2\pi} \bigg[ -cos(\gamma) \bigg]^{\pi}_{\alpha}$$
With $$U_\sim = 40V, \alpha = 40°$$
I measured \$23.25V\$ but using the equation I got \$11.243V\$.
I suspect the equation (or my usage of it) to be faulty. But as the equation should be correct now (according to the linked question) and the measurement should also be reasonably correct I can't say what's wrong.


texts: How to display a custom parameter value in the PCB footprint of my Altium component?

texts:
Suppose my component has a string-valued parameter named "Label". I'd like the PCB footprint for this component to automatically display whatever value was set for this parameter in the schematic view.

I've tried placing a text component with the value ".Label", and I've enabled "Convert special strings" in the PCB view configuration, but the text still shows as just ".Label".

Can I somehow get it to show the value of the "Label" parameter as set (and displayed) in the schematic view?


texts: PSIM : I'm trying to make a current zero crossing detector

texts:
So I'm trying to make a current zero crossing detector but i want a short impulsion every time the current cross 0 so the switch is up for a very little time.
As I started PSIM not long ago, i'm not sure if the bidirectional switch is the one to use there and I'm missing something such as an edge detector (in the part circled in red).
Could anyone help me please ?


texts: How to build a simple waveguide and start on microwave electronics?

texts:
I have an electrical engineering qualification and new to microwave engineering, but really never did much RF or microwave when studying.

I want to build a very basic and simple waveguide microwave system say using  WR 340 waveguide  to produce a plasma. I am fully aware  of the dangers of microwaves.

My ultimate aim is a very rough first attempt without a circulator and isolator but hoping to generate a plasma.

Can this be done without gear like meters for power measurement and use of HFSS etc? It doesn't have to perfect...just a basic long rectangle box waveguide with a rectangle WR 340 cross section waveguide.

Where do I start? I'm very committed to do this.


texts: Why Fault pin of IR2136 gate driver is getting low at high voltage?

texts:
I am implementing a variable frequency drive for a three-phase induction motor.  I used IGBT module fs25r12w1t4 with gate driver ( three phase, six Channels IR2136). When I increase the voltage, the fault pin receives a noise or anyway it goes to zero. The controller reads it as zero. so Fault interrupts become active as it considered that the fault has occurred.

Then I checked the fault pin of IR2136 through Oscilloscope, it goes to low at 170 V. It remains active below the voltage level of 170V.
please, can you tell me what may the issue with the gate driver IR2136? why it goes to low at high voltage.
This problem happens at high voltage.


texts: Output of Inverting opamp with single supply

texts:
I have the following circuit I'm looking into (it's actually a section of a larger design)

simulate this circuit – Schematic created using CircuitLab

V1 has an input range of 0 to 4V.
Vout I suspect, would be 0V for the entire duration.

However, when I simulate both here and using LTSPICE, I get a non zero answer.

I am unsure as to why.

It would seem that I am in fault since two simulations do not give me a non zero answer(although the simulation done here and on LTSPICE are also different from each other) and this circuit is "known" to work.

What am I missing ?

edit
Updated schematic with R3.


texts:
So I'm trying to connect CS4270 codec to STM32F446RE. I managed to drive DAC part using SAI sublock B, but when I enable sublock A for receiving the sent data becomes corrupted (instead of L R L R on data line I get L R 0 0 L R 0 0).
I wanted to verify if analog section works but enabling digital loopback returns noise. When I hook up logic analyzer to data output it indeed shows that there's byte swap in ADC datastream.
Below is the code of SAI initialization. When commented part gets uncommented the described issue is generated.
The code is more or a less cubeMX output as I hoped it would work out of the box.
static void MX_SAI1_Init(void)
{
    hsai_BlockA1.Instance = SAI1_Block_A;
    hsai_BlockA1.Init.Protocol = SAI_FREE_PROTOCOL;
    hsai_BlockA1.Init.AudioMode = SAI_MODESLAVE_RX;
    hsai_BlockA1.Init.DataSize = SAI_DATASIZE_16;
    hsai_BlockA1.Init.FirstBit = SAI_FIRSTBIT_MSB;
    hsai_BlockA1.Init.ClockStrobing = SAI_CLOCKSTROBING_FALLINGEDGE;
    hsai_BlockA1.Init.Synchro = SAI_SYNCHRONOUS;
    hsai_BlockA1.Init.OutputDrive = SAI_OUTPUTDRIVE_DISABLE;
    hsai_BlockA1.Init.FIFOThreshold = SAI_FIFOTHRESHOLD_EMPTY;
    hsai_BlockA1.Init.SynchroExt = SAI_SYNCEXT_DISABLE;
    hsai_BlockA1.Init.MonoStereoMode = SAI_STEREOMODE;
    hsai_BlockA1.Init.CompandingMode = SAI_NOCOMPANDING;
    hsai_BlockA1.Init.TriState = SAI_OUTPUT_NOTRELEASED;
    hsai_BlockA1.FrameInit.FrameLength = 32;
    hsai_BlockA1.FrameInit.ActiveFrameLength = 16;
    hsai_BlockA1.FrameInit.FSDefinition = SAI_FS_STARTFRAME;
    hsai_BlockA1.FrameInit.FSPolarity = SAI_FS_ACTIVE_LOW;
    hsai_BlockA1.FrameInit.FSOffset = SAI_FS_FIRSTBIT;
    hsai_BlockA1.SlotInit.FirstBitOffset = 0;
    hsai_BlockA1.SlotInit.SlotSize = SAI_SLOTSIZE_DATASIZE;
    hsai_BlockA1.SlotInit.SlotNumber = 1;
    hsai_BlockA1.SlotInit.SlotActive = 0x00000000;
    /*if (HAL_SAI_InitProtocol(&hsai_BlockA1, SAI_I2S_MSBJUSTIFIED, SAI_PROTOCOL_DATASIZE_16BIT, 2) != HAL_OK)
    {
        Error_Handler();
    }*/
  hsai_BlockB1.Instance = SAI1_Block_B;
  hsai_BlockB1.Init.AudioMode = SAI_MODEMASTER_TX;
  hsai_BlockB1.Init.Synchro = SAI_ASYNCHRONOUS;
  hsai_BlockB1.Init.OutputDrive = SAI_OUTPUTDRIVE_ENABLE;
  hsai_BlockB1.Init.NoDivider = SAI_MASTERDIVIDER_ENABLE;
  hsai_BlockB1.Init.FIFOThreshold = SAI_FIFOTHRESHOLD_EMPTY;
  hsai_BlockB1.Init.ClockSource = SAI_CLKSOURCE_NA;
  hsai_BlockB1.Init.AudioFrequency = SAI_AUDIO_FREQUENCY_MCKDIV;
  hsai_BlockB1.Init.Mckdiv = 7;
  hsai_BlockB1.Init.SynchroExt = SAI_SYNCEXT_DISABLE;
  hsai_BlockB1.Init.MonoStereoMode = SAI_STEREOMODE;
  hsai_BlockB1.Init.CompandingMode = SAI_NOCOMPANDING;
  hsai_BlockB1.Init.TriState = SAI_OUTPUT_NOTRELEASED;
  if (HAL_SAI_InitProtocol(&hsai_BlockB1, SAI_I2S_MSBJUSTIFIED, SAI_PROTOCOL_DATASIZE_16BIT, 2) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN SAI1_Init 2 */

  /* USER CODE END SAI1_Init 2 */

}

What's wrong with my initialization code, how can I get SAI to receive & transmit I2S data at the same time?
Also why are the bytes swapped?
EDIT
my cubemx config


texts: Advice on precision CNC milling machines for PCB prototyping

texts:
I am an EE professor at an University and I was asked to provide a solution (machine) for PCB prototyping. Specs are milling down to about 8 mil (0.2032 mm) trace thickness, 8 mil trace clearance, 8 mil drilling/hole size, just 2 layers, material is standard FR-4 PCB. Vias and holes can be fulfilled with conductive epoxy if needed, although metal plating is of course a better choice. Finishing is not a concern, really.

Students and professors will use this solution. A dedicated technician will account for the operation, no students will lay hands unless authorized and accompanied. Before you say board houses are a no brainer, I am in South America and pcb houses are not that cheap or common as in USA or Europe. Also, it is a chance for students to get in touch with the full process.

Chemicals are absolutely off list. I also put aside all of those desktop lpkf, t tech, etc machines. All reviews I've seen show they are impractical, lousy software, parts break easily, double side is still a pain, etc.

Our budget, although not really set, is actually interesting: I'd say we are around USD 12k top. Demand is not high, there is no need for large output, just small volumes, but I can't account for a solution at this price range that brings us problems: it has to work fine and up to specs!

Given the budget, I am also considering a different approach: a full CNC milling machine, capable of mechanical works and capable of working on steel and wood - given the right drill bits and tools. PCB prototyping needs are fulfilled (?), and the investment is not restricted to that purpose.

Advice on the approach?


texts:
In looking for a 64K x 8 Parallel EEPROM, one of the most available chips is the 27SF512. Google would indicate this is commonly used by auto enthusiasts to replace chips in various cars. I have found dedicated programmers that cost up to hundreds of dollars, but I don't really want to do that. I would like to program it from my computer via an Arduino on a serial connection.

From the datasheet:

  The programming mode for SST27SF512 is activated
  by asserting 11.4-12V on OE#/VPP pin, VDD = 4.5-5.5V,
  and VIL on CE# pin. These devices are programmed byteby-byte with the desired data at the desired address using
  a single pulse (CE# pin low for SST27SF512 and PGM#
  pin low for SST27SF010/020) of 20 µs. Using the MTP programming algorithm, the Byte-Programming process continues byte-by-byte until the entire chip has been
  programmed.

I get that I need to apply high voltage to the VPP pin, and that CE then becomes a clock pin of some kind. I just have no idea what the MTP programming algorithm is.

Best case I can just put the address I want to write and the data on the appropriate pins and put CE low to store the data. It appears that maybe I have to write every byte in sequence though. Thats ok too, but I have failed to find any firm details on the exact protocol to use.

It also looks like I need to fully erase the chip to all 1's before any programming, but that seems much more straightforward.

I would like to make sure I understand what I'm doing before I shell out for a batch of chips.


texts:
I'm trying to make a zero cross detector. I used the schematic below as a reference.(schematic from http://microcontrollerslab.com/zero-crossing-detector-circuit-using-pic-microcontroller/)

However if I hook up my scope then I get the following image:

You can see that ther is only 1 zero cross detected while there should be 2. Can someone explain why this happens?

I am using 1n4007 diodes and a bc547 npn transistor.

When a 10kOhm resistor is applied at the output of the bridged rectifier:

Many thanks in advance.


texts: Formula question about the Bridge and full wave rectifier,where are these number from?

texts:
i learn something formula of Bridge and full wave rectifier from my book

DC voltage \$V_{DC}=V_m-\frac{V_{r_{(pp)}}}{2}\$,\$V_m\$ is the amplitude of sine wave voltage, \$V_{r_{(pp)}}\$ is the peak to peak voltage of ripple wave
The RMS voltage value of ripple \$V_{r_{(rms)}}=\frac{V_{r_{(pp)}}}{2\sqrt{3}}\$
If \$f=60Hz,V_{r_{(rms)}}=\frac{2.4V_{DC}}{R_L C}\$
Ripple factor \$ =\frac{2.4}{R_L C} \times 100 \% \$

i have some questions about the formula above

Q1

In the 2. formula,how is the \$2\sqrt{3}\$ calculated?i mean,based on what reason,so we can say \$V_{r_{(rms)}}=\frac{V_{r_{(pp)}}}{2\sqrt{3}}\$,not \$V_{r_{(rms)}}=\frac{V_{r_{(pp)}}}{any \ number}\$?

Q2

In the 3. and 4. formula,how is the \$2.4\$ calculated?
i mean,based on what reason,so we can say \$V_{r_{(rms)}}=\frac{2.4V_{DC}}{R_L C}, \$and Ripple factor   \$=\frac{2.4}{R_L C} \times 100 \% \$
not \$V_{r_{(rms)}}=\frac{any \ number \times V_{DC}}{R_L C} \$ or Ripple factor   \$=\frac{any \ number}{R_L C} \times 100 \% \$ ?


texts:
I'm controlling three 4066 (Quad Bilateral Switch) with two chained 74HC595 (8-bit serial-in, serial or parallel-out shift register with output latches; 3-state)

Do I need to use pull up resistor with the 4066 in that cas ? I can't found on the web or datasheet application with them. So do I need to put a grounded resistor connected betwwen the 74HC595 outputs and the associated 4066 inputs ?


texts: What is T1 in this circuit for 'Mains power failure alarm'?

texts:
I know it is a transformer, but is it a transformer that looks like an IC? Or just a regular step down transformer? (Transformer 12V (1A)). This will be built on a breadboard.

Also can I use 1n4007 for the full wave rectifier diodes?

I would also appreciate any feedback on this circuit.


texts:
I am new to PCB routing. In one of my projects, I need to be able to exchange data between nano-computers (https://www.variscite.com/wp-content/uploads/2018/01/DART-6UL_DART-6UL-5G_Datasheet.pdf) using an Ethernet connection. I will use a simple RJ45 connector soldered on my card (https://docs-emea.rs-online.com/webdocs/0fae/0900766b80fae0ad.pdf).

My question is now : how am I suppose to route the 8 Ethernet pins to my nano-computer ?

I do not want to route differential pair all the way to the nano-computer. I have searched and read about magnetics, transformers, rmii, PHY, MAC... But it is all confused in my head and I don't know which one I should use.

Is there a classic way to achieve this PCB routing ? (at least schematic routing first)

Thank you all


texts: triggered PWM from ADC end of conversion

texts: I am making a full bridge control on D-SMPS and I want to trigger PWM from ADC to keep output voltage constantly stable. I am using STM32f103xx as microcontroller. The problem is that looks like in ST's MCUs does not provide a trigger for PWM from ADC. So how can find the right path?


texts: Eco-roof flow meter with "counter channel" output - what is that?

texts:
Some background:

I'm working on an eco-roof flow monitoring project and we want to hook up a Unidata 6506G tipping bucket flow gauge (our effluent flow is in a strange low range range where we needed a large tipping bucket) to a Steven's data logger.

Data Sheets:

Flow Meter
Data Logger

Real Question:

What's with the output from this flow meter? It just says "a series of digital pulses." What is a counter channel, what is a pulse channel, and how do they differ from analog? Do you think it will be necessary (or possible) to have, say, a microcontroller translating the data from the flow meter to something the data logger can handle?

Apologies for broad question, I am an environmental engineering student. Anything to get me on the right track would be awesome. Thanks!


texts: Questions About Wiring High-Power Robotics Motor Chassis

texts:
I recently ordered a Wild Thumper 6WD robot chassis to build for a school robotics club project. I've built smaller, simple robots before, but I haven't built one with such high power requirements before.

I bought this from Sparkfun, along with a recommended battery - a 7.4V 2200mAh 35C discharge rate LiPo with a Deans connector for output and a jst connector for recharging. I also got their recommended charger/balancer. I plan to get an identical second battery soon, if this one works out. Additionally, I have a Sparkfun Monster Moto shield that they say handles the Wild Thumper well in their usage. It can handle 14A continuous and 30A max per channel.

Each motor has a 420mA no-load and 6.6A stall current draw. So, that means I'll need both wiring and a motor controller that can withstand up to at least 19.8A per channel

So my questions are about wiring the motors to the motor
controller and to the battery. The six motors are wired in two groups of three motors, one group per side, to make driving the robot with a differential drive system using a two-channel motor controller.

Pictures are here:
http://campl.us/GVZsJcecyGW

First question:
What minimum gauge should I use for connecting the battery and motor controller to the motors? The battery uses 12-gauge wire, but the chassis' own wiring harness for the motors uses 20-gauge. So, is mixing different gauges ok?

I would like to use connectors, like the Deans connectors that came with the batter to facilitate unplugging / changing components, as well as a nice switch. I know the chassis power connectors are difficult to see, but can anyone recommend a good connector to fit those?

Third question:
Is the Sparkfun Monster Moto shield adequate for the motor performance ratings? The motor datasheet doesn't say what the typical operating current draw would be, presumably because it varies with speed an other usage factors.

Also, would powering the motors with a reduced voltage, say 5V, reduce current enough to use a less expensive motor controller? I don't need it to go fast; just to carry a lot of sensors. The motors have a 34:1 gear ratio with a stall torque of ~ 5kg/cm and a top speed of 7km/h at 7.4 volts. Besides reducing the speed, what effects would restricting the voltage have? I'm not sure how to figure out the changes in current because I'm not sure what the resistance would be at 7.4V

Thanks in advance!


texts: Using Arduino UNO as a USB to TTL converter for unbricking a Seagate Barracuda 7200.11 Hard Drive

texts:
Is it possible to use an Arduino UNO as a USB to TTL converter for unbricking a Seagate Barracuda 7200.11 Hard Drive

And if it is possible : how to program it?

The Arduino UNO has no FTDI chip.

In this video, they have done it with a Arduino clone with a FTDI chip :
http://adaptorforrs232cserial.blogspot.com/2012/02/seagate-720011-hd-unbricking-with-mac.html


texts: Jacob Shekel's method for ideal transformer

texts:
I would like to ask some questions relating to the thesis "Analysis of Linear Network" by Jacob Shekel.

From chaper III - "The Network", section 3.6 - Network Transformations, the author explains theory to deal with components such as an ideal transformer, ideal voltage divider.

Then in section 3.7 "How to Write the Y Matrix of a Given Network", he gives an example to show how to apply this theory to a circuit including two triodes and one ideal voltage divider.

I follow the example and understand how it is used with the ideal voltage divider but I am wondering how to apply the theory to an ideal transformer.

The ideal voltage divider draws no current so it has only voltage constraint.
However, the ideal transformer is different. It has both voltage and current constraints. So how to use these constraints to create admittance matrix for a circuit including ideal transformer?

Hope someone could shed some light on how to apply this theory to a circuit containing an ideal transformer.


texts: Is power draw always modeled in Op-Amp SPICE models?

texts: I know op-amp models are simplified versions of the actual op-amp, is it safe to say that the power/current draw is nearly always modeled?


texts: Understanding how One-BJT CW transceivers work

texts:
These days, I have been looking around some schematics for building a minimal CW transceiver. However, I do not fully understand their principle of operation.
As an example, here is the Pititico transceiver by PY2OHH:

There are many similar designs around (see the one by HA4OO or this list), but I prefer to focus on this one as of now in order to try to fully understand it.
As far as I know, in the previous schematic the crystal must act as the signal generator and, the BJT, as an amplifier (maybe a class-A amplifier, but I do not fully understand the feedback connecting the emitter with the base). C4 seems to me to be related with matching the output impedance of the antenna, but it is just a guess. U1 is a high impedance headphone and C3 is just a decoupling capacitor, and I cannot name the use of the rest of the components of this circuit which I am trying to decypher.
The thing I find the most disturbing on that schematic is how the separation between TX and RX is done. I read that the network C1-L1-C2 creates an offset of less than 1KHz to diplex both signals. How is this possible? Moreover, how is downconversion perfomed? Isn't there any mixer?
Thank you in advance.
Edit 1: Thank you to the people that answered; I know understand that the TX is a Pierce oscillator directly connected to the antenna, and that the RX acts as a regenerative receiver.
It would be great if someone could explain how TX and RX are combined, namely, how those capacitors (C1, C2 and C4) produce (demodulate in a direct downconversion) an offset signal at the headphone output.


texts: Biasing with Negative value of Vgs in NE76038 GaAs MESFET

texts:
This is the value of Idss (drain current with Vgs = 0) and value of Vp (pinch off voltage) :

I want to bias the transistor using common source with Ids (drain current) = 10 mA and Vds = 3 V.By using this formula we can calculate the value of Vgs.

By using Idss = 30 mA and Vp = -0.8 V from the datasheet, we obtain the value of Vgs = -0.338 V. How can I design the bias circuit with the negative value of Vgs?


texts: Oscilloscope cap replacement - Panasonic vs Nichicon

texts:
I have to replace a bunch of capacitors on the acquisition block of a portable digital oscilloscope and one of the requirements is that the capacitors have beto be small.

I am trying to decide between Panasonic KS/KA series and Nichicon UMW.

Can anyone advise which one suits better my application?

Panasonic KS/KA is a standard series. Nichicon UMW is an audio series.

I have a preference for Panasonic as I can buy locally. But not sure Audio would be of any benefit here.

Panasonic https://docs-apac.rs-online.com/webdocs/0027/0900766b800274c4.pdf

Nichicon http://nichicon-us.com/english/products/pdfs/e-umw.pdf


texts:
I an trying to connect a 16x2 LCD text module with Arduino and it continuously shows only the green backlight. My code is correct and my connections are also correct. I tried the same project on Proteus and it works fine.

Thanks for everyone issue is solved..i buy new LCD and everything is fine.

#include <LiquidCrystal.h>

LiquidCrystal lcd(1, 2, 4, 5, 6, 7);

void setup() {
   lcd.begin(16,2);
}

void loop() {
    lcd.print("Sanjeev");
    delay(3000);
    lcd.setCursor(2,1);
    lcd.print("LCD is working");
    delay(3000);
    lcd.clear();
    lcd.blink();
    delay(4000);
    lcd.setCursor(7,1);
    delay(3000);
    lcd.noBlink();
    lcd.cursor();
    delay(4000);
    lcd.noCursor();
    lcd.clear();
 }


texts: Connecting the linear regulator directly to AC line

texts:
There are several out of the shelf solutions: LR8 from Microchip (formaly known as Supertex product) and NCP785 from ON-Semi. The last one is able to handle up to 700 volts at the input which is impressive.

Both components is very attractive to be used in my application. However, LR8 does not have enough voltage strength (I need to withstand 400 VAC = 625 VDC) and NCP785 is not easy to buy in my country (Russia).

One of the solutions is to put an external transistor like this:

However I think that it should be possible to add an external transistor to linear regulator (LP2981 in my case) without additional components (zener, resistors...) - this would be perfect as I need to reduce PCB size.

From my early engineering career I remember that the external transistor can be used to increase the current of the regulator, something like this:

Is it possible to do same thing to input voltage?


texts: AC constant current (6 A rms) to 12 V DC

texts:
How to convert AC Constant current 6 A rms to 12 V DC (or 24 V DC) ?
I want this circuit for LED power supply.
In addition the circuit has 2 steps to control illumination of LEDs.


texts: Possible capacitive coupling on soldering iron

texts:
I have bought a cheap soldering iron. It seems to work fine.
Out of curiosity I tested the metal enclosure (and thus also the tip) with an electric tester and it lit up. Then I tested it with a multi-meter and it shows about 120V with respect to one of the mains and 0 with respect to the other. Mains is 220V where I live.
Then I tested the resistance between the metal enclosure end both of the power socket pins (it has only two pins, no ground wires.) It shows infinity. The metal enclosure gave no shock while connected, though I was heavily isolated from the ground.
I am interested in knowing what is happening.
My guess is capacitive coupling. Will I get a shock if I am somehow connected to the ground? Is the soldering iron ESD safe? If I ground the tip (and thus also the enclosure,) won't it trigger the ground fault detector?


texts: What causes a potentiometer to get "jittery" after cleaning?

texts:
I recently cleaned a potentiometer's resistive element by using general purpose contact cleaner (CRC).  I now find that there is "jitter" or non-linear increase in the resistance as I rotate the shaft.  For instance, the resistance might momentarily drop while increasing the resistance, but this only appears to happen if I rotate quickly.
I'm curious what causes this as I suspect I may have damaged the resistive element on the potentiometer.  I cleaned two potentiometers with the same cleaner and the effect is present on both (one worse than the other).
For reference, I am working with Atari Paddle Controllers, which are basically a potentiometer and push button.  The game input and jitter was tolerable prior to cleaning, but now it almost makes the game unusable; the in-game paddle/icon jumps all over the place as the physical potentiometer is rotated.


texts: critical inductance value when designing a buck converter

texts:
From the formula used in this literature from Texas Instruments
http://www.ti.com/lit/an/slva057/slva057.pdf - Page 15

Here are my requirements:

Vo-Output voltage(v)    98
Vi(max)-Maximum input voltage(v)    120
Ts-Time period(sec) 0.000001
Io(crit)-Minimum current to maintain continuous conduction(A)   0.1

Calculating the inductor value i get it:
L(min)    8.98E-05 H

So am i correct in assuming that any value of inductance above L(min)will ensure BUCK operation in continuous mode?
If that is the case ,can i remove the catch diode/free wheeling diode,without causing damage to my MOSFET during operation?


texts: Pin of micro USB connector in Smartphone

texts:
The image below shows a Micro USB connector in a smartphone. I understand what the first 5 pins of the USB are i.e. USB_DM, USB_DP, USB_ID , VBUS and GND.

The pin S1 is connected to VBAT (battery voltage pin) through a load switch.

Can anyone explain to me the function of the S1 pin?


texts: Diagnosing slow / gradual electric motor startup

texts:
I'd like to improve the very slow startup of a bench grinder motor. I have linked a video which shows its current behavior:
https://youtu.be/KPIgmcJJi5E
The video shows the grinder being switched on from 'cold' and taking a few seconds to accelerate up to full speed. Note that the (LED) lamp doesn't light until its close to full speed.
In my experience with other motors, this is pretty strange. Generally they go to full speed extremely quickly, even under load.
Its a single-phase 120V motor. The bearings seem fine - it rotates normally.
It has a run capacitor but no start capacitor.

What I have done so far:
I thought it might be a bad capacitor - when I replaced it with one having the same specification as the original (25 uf), there was no change. So I assume the original was OK. When I tried a much larger capacitor (300-360 uf) it accelerated instantly; but that cap was clearly much too large as it seemed to trigger the thermal overload.
Its possible the original capacitor was not OEM (the grinder is second-hand). But according to Electric Motor Starting Capacitor Selection table "Estimated Small Motor Capacitor "Ballpark" Sizes Based on Motor Type" on  it seems roughly OK. Its also a bit larger than the recommended info in table "Estimated Small Motor Capacitor "Ballpark" Sizes Based on Motor Horsepower".

Can I select a larger capacitor to improve startup, but without causing other problems? Or is there some other (electrical) update I could make?

Original capacitor:

Same-sized replacement capacitor:

Oversized replacement cap:

Nameplate:


texts:
what is the Input impedance of transmission line, when source frequency contains two frequency components?

I know the expression of input impedance of a TL, but it assumes that only a single frequency component is present in the source. What if source is providing power having two frequency components?

S1 and S2 are sources, l1,l2 are self inductance of coil and M is the mutual inductance. Zin1 and Zin2 are the input inpedance of TL.

S1 and S2 have diffrent frequency.


texts: Low frequency PWM Brushless DC Motor Speed Control

texts:
I am programming a L293D motor driver with a BLDC motor to spin at speeds of 60-300 RPM. It is for a hybrid drone/car where I want the motors to spin slowly while having the necessary torque to drive.

So far, I've followed instructions in the spirit of this guide in MatLAB:

http://www.berryjam.eu/2015/04/driving-bldc-gimbals-at-super-slow-speeds-with-arduino/

I've attached a picture of my coding, where i tried various methods of controlling the motor, via "micro-stepping", spwm signals, and simply a sine wave function.

I've had the most success with the sine wave function, where the motor initially runs smoothly, but progressively the motion becomes jolted. On the oscilloscope, there was also a lot of voltage spikes, which I request your help in understanding and fixing. Perhaps I can somehow implement some diodes into the circuit? Also, the torque was non-existent.

I used a 12 volt DC supply, which gave out 0.5 amps to the driver.


texts:
I am using an Audio Module. The schematics of the module can be found below. The module uses a audio amplifier (TS4990IST) and STM32F0 MCU.

I found out when powering up the module, the module start heating up. In my module, capacitor C10 is not soldered. Can someone help me to rectify the issue?

EDIT:
I have been reading the datasheet of TS4990 and found out it may require Cin capacitor at the input (Page 4). Find the screenshot of page 4 below:

Looks like the manufacturer of these modules has forget to add the Cin Capacitor and may be that's why the module is amplifying DC voltage and hence heating up the module. Am I right?


texts: How does this T-network op amp function as a boost filter?

texts:
Supposedly this circuit is supposed to be a bass frequency booster.
I've been using this article as a reference, although the circuit they analyze is a different layout than mine.
I apologize if my work is hard to read or follow, but I'm getting something in a (1 - BPF) form for a transfer function (I struggled to get this into anything slightly resembling standard form, so there may be some calculation errors).

This looks like a notch filter to me, rather than a boost.
The article the original image is from says

A bridged-T feedback network is basically a low-pass filter mixed with a high-pass filter. It's usually a passive filter that creates a notch (cuts the frequencies) but when it's in a feedback loop it becomes a boost.

But I'm not seeing why or how that's the case. They also link to a site with the same T-network form that has the transfer function in a different form than I have mine in, but also concludes that it's a notch filter.
Is someone able to help me understand why the feedback network turns this notch into a boost?


texts: Maximum clock frequency for multi-cycle vs pipeline

texts:
Suppose you have latencies:

IF: 10 ns
ID: 11 ns
EX: 12 ns
MEM: 13 ns
WB: 14 ns

What is the maximum possible clock frequency for a pipeline with this design?  I found information online that suggests the maximum possible clock frequency is 1/c, where c is the latency of the slowest stage.  Thus, we have 1/14 GHz.  Is this correct?

Also, how does this differ from a multi-cycle design?  If we had latencies:

Register read: 1 ns
Register write: 2 ns
ALU: 3 ns
Memory read/write: 4 ns

Wouldn't the maximum clock frequency also be 1/c, where c is the latency of the slowest stage?  Thus, we would have 1/4 GHz.

In total, if my above calculations are correct, I'm curious as to why the multi-cycle and pipeline design internally depend on the same latency delay (the one that's slowest).  Thanks for any help.


texts: Transfer function for controllable part of a linear system

texts: I understand that for my linear system $$ \dot{x} = Ax + Bu ;\quad y = Cx$$ the transfer function expression $$ C(sI-A)^{-1}B = C_c(sI-\hat{A_{11}})^{-1}\hat{B_{11}} $$ where the latter exposes the controllable part of the system. Is this because a pole-zero cancellation exists?


texts: Touching SPI clock pin results in loss of sync

texts:
I've connected a Rasperry Pi to a MSP430 uC using a 3 wire 8bit SPI interface.
The SPI communication seems to work (I've checked on both ends and the data is correct).

On the PI I communicate using a user-land spidev client (no persistent state machine). On the MSP430 the SPI state machine is only initialized at startup.

If I touch the SPI clock wire with one of the multi-meter's connectors (+ or -, doesn't make a difference) the SPI connection goes out-of-sync (I see garbage data on both ends) until I reset the MSP.

Is this normal behavior or am I facing a connectivity/grounding problem?


texts: H-Bride Implementation with minimum voltage drop using Raspberry Pi

texts:
I am using the Raspberry Pi's GPIO pins to switch transistors in an H-Bridge. This circuit is designed to allow a path to ground that will reverse the polarity of the motor without the wires being physically switched. The circuit operates as intended, however there is quite a significant voltage drop with nearly half the voltage being dropped across the load. I have used LEDS in this schematic to demonstrate the reverse polarity property of the circuit, however the load will be a dc linear actuator. If the LED is replaced with the actuator it adds .7V to the circuit, however this isn't enough. This circuit is sufficient to run the actuator at full battery, however I would like to have it be faster. Another issue, is that when the battery voltage begins to drop this circuit will no longer work due to the voltage drops across the transistors. Is there a way to turn these transistors on without diminishing the batteries voltage? The raspberry pi gpio pins supply 3.3v at the base to turn the transistor on, however it seems that there is a total 1.4 voltage drop from the battery. Is there a way to have this voltage drop come from the raspberry pi, or another way to design this circuit? Any help is appreciated.

I tried using this circuit which was an improvement, however when battery voltage drops below 2V it no longer works. Is there any way to amplify the voltage from the gpio pin so that this circuit would work with a battery voltage of around 1 Volt using the circuit below?


texts: How to run electricity through metal wire to (safely) act as a stylus?

texts:
I’m trying to make a robotic arm draw a lowercase ‘i’ on my iPhone’s drawing app without lifting the stylus. The robot arm bit is another story, my current focus is trying to make a stylus out of a metal wire.

I think I can break this question down further:

What material is best to use? Any sources or charts I should look into?
How much current should be applied to this wire to safely interact with the average capacitative touch screen?
Does thickness of wire matter in respects to precision and current needed? Stated differently, if the iPhone X’s pixel size is about 0.05mm, what considerations do I need to make regarding the thickness of the wire?


texts: How many 12 V 100 Ah batteries do I need for overnight?

texts:
I actually want to upgrade my existing solar power system at home with new set of batteries that could live up the night when solar arrays are unable to charge but I am getting confused on how many I actually need to achieve this. My current inverter max draw is 1500 W though I am planning to replace it with 3000 W along with new battery replacements

What I have currently are:

Fridge: uses 0.48kWh within 16 hours from sundown till next sunrise the next day
PC: uses 0.308kWh within 8 hours starting from sundown
a 5W light bulb
a Internet modem
a few number of phone chargers

As for battery decay over time, the most optimal time I guess for replacement is around every 3 to 4 years.


texts: RCA AH5 AC/DC adapter switch polarity question

texts:
I apologize in advance for asking this, as this should be answered via Google search but I'm not finding the correct manual for the RCA AH5 power adapter. And before I fry anymore instruments by using the wrong polarity (which I've done twice before) I'll risk the embarrassment.

I have a RCA AH5 AC/DC adapter. I need to know for sure which switch is for negative polarity. The manuals online show an "adapter receptacle" and the tip. I am familiar with those. This adapter have a switch, no "adapter receptacle" or a tip that you align it up with.

Isn't the negative polarity with the switch down in this photo? If you can't make it out, it shows a (-) at the tip, and a (+) at the base of the tip. I assume that's it but I'm not taking another chance and going to ask here.

It's a crappy iPhone photo but that's the only camera I have at the moment.

Thanks in advance...


texts: Verilog: MIDI receiver port fails when more than two keys are pressed at the same time

texts:
I'm designing a MIDI receiver port (using Altera CLPD MAX 7000S). The device samples the second byte it receives and outputs the binary value on an LEDs. The device works fine whenever I input MIDI notes (using MIDI-OX software) at a normal speed. However, whenever I input notes too fast, or input two notes at the same time), it doesn't work correctly (outputs to incorrect LEDs whenever I input any note).

This is my Verilog code.
I sample the MIDI bit at the middle.

//using a 4MHz clock using a 31250bit/s baud rate (1 bit -> 32 us; all 10 bits -> 320us  -> 10.3 bits -> 11 bits)
module timer(input clk, input reset, input enable, output [10:0] out);
reg [10:0] timer;
initial timer = 11'b0;
assign out = timer;

always @(posedge clk) begin
    if(!reset)  //if reset is pressed, set timer back to 0
        timer <= 11'b00000000000;
    else if(enable == 1'b1) //if enable is high
            begin
                timer <= timer + 11'b00000000001; //increment counter every time
                if(timer == 11'b11111111111)     //if counter reaches max value (should never reach it)
                    timer <= 11'b00000000000; //set it back to 0
            end
    else
        timer <= 11'b00000000000; // if enable is low, set the timer to 0
end
endmodule

module rx(input clk, input reset, input in, output [7:0] out);

parameter IDLE = 2'b01;
parameter BYTE_CUR = 2'b10;
parameter BYTE_END = 2'b11;
parameter HIGH = 1'b1;
parameter LOW = 1'b0;

reg [7:0] LEDs;
initial LEDs = 8'b0;

reg [7:0] LED;
initial LED = 8'b0;
assign out = LED;

reg [1:0] state;
initial state = IDLE;

reg [2:0] byteNo;
initial byteNo = 3'b000;

reg timer_en;
initial timer_en = 1'b0;

wire timer_en_wire;
assign timer_en_wire = timer_en;

wire [10:0] timer_wire;

timer t(.clk(clk), .reset(reset), .enable(timer_en_wire), .out(timer_wire));

always @(posedge clk) begin
    if(!reset)
    begin
        LEDs <= 8'b0;
        LED <= 8'b0;
        timer_en <= 1'b0;
        state <= IDLE;
        byteNo <= 3'b000;
    end
    else begin
    if(state == IDLE && in == LOW) // if IDLE and detect a LOW on the input line, start bit has arrived
    begin
        state <= BYTE_CUR;  //change state to BYTE_CUR
        byteNo <= byteNo + 3'b001; // increment byteNo
        timer_en <= 1'b1; // enable the timer
    end
    if(state == BYTE_CUR) //currently a byte
    begin
        case(timer_wire)
            11'b00011000000: LEDs[7] <= in; // 1.5 BT
            11'b00101000000: LEDs[6] <= in; // 2.5 BT
            11'b00111000000: LEDs[5] <= in; // 3.5 BT
            11'b01001000000: LEDs[4] <= in; // 4.5 BT
            11'b01011000000: LEDs[3] <= in; // 5.5 BT
            11'b01101000000: LEDs[2] <= in; // 6.5 BT
            11'b01111000000: LEDs[1] <= in; // 7.5 BT
            11'b10001000000: LEDs[0] <= in; // 8.5 BT
            11'b10100000000: begin   // 10 BT
                state <= BYTE_END;
                timer_en <= 1'b0;
            end
        endcase
    end
    if(state == BYTE_END) //if byte has ended
    begin
        if(byteNo == 3'b010) // if byte number is 2, output the lights
        begin
            LED <= LEDs;
        end
        if(byteNo == 3'b101) // if byte number is 5, clear the output
        begin
            LED <= 3'b000;
        end
        if(byteNo == 3'b110) // if byte number is 6, reset byte counter to 0
        begin
            byteNo <= 3'b000;
        end
        state <= IDLE; //set state back to IDLE
    end
    end
end

endmodule


texts: How to connect 5 colored wire headphone to 3.5 TRS jack?

texts:
I have a somictone headphone and I want to repair its headphone jack, It contains five colored wires.
Here are the wire and TRS jack.
Please give me a feedback

Can you please tell me how to wire this?
I really appreciate your help.


texts:
Given I am still learning how to do these Boolean Algebra, I was wondering if someone could tell me if I am on the right track.

All work is pictured. I figured that the circuit drawn is the actual circuit and not simplified using the Karnaugh map. Also does that have 3 gates technically or just two?

Any help is appreciated!
EDIT: I know this is wrong but I am not sure where I went wrong. Has to be in the Karnaugh map but I dont understand why or where.


texts: What is the difference between half controlled and full controlled rectifier?

texts: Half Controlled and Full Controlled Rectifier-Why we go for full controlled while half controlled can control voltage?


texts: How to calculate the total resistance fo a parallel circuit in series

texts:
I have a simple question on resistance calculation but I can't work it out. The diagram is from the site all about circuits.

I can't figure out why the top parallel total resistance for example is 71ohms. I thought the calculation for this would be
1/Rt=1/100+1/250
1/Rt=0.1+0.04=0.104
Rt=1/0.104=9.6?????

Have I missed something obvious? Appreciating that the answer is probably simple but if I dont ask I'll never find out....


texts: Boost converter voltage drop when connected to load

texts:
I have designed a boost converter based around the TPS61200 chip. This is a low voltage boost converter with a varying input of around 1.5V and 400mA.
The output of the circuit is 3.3V. However, when I connect a load (3.3V fan that draws 60mA) the voltage drops to 1.5V output. When I connected a motor (3V that draws 18mA) the voltage dropped to 50mV output!
I've also purchased an off the shelf module which experiences the same issue, so it's probably not my circuit design.
The components I'm using on the board are the following:

Boost IC - TPS61200 (https://www.ti.com/lit/ds/symlink/tps61200.pdf?ts=1598365314165&ref_url=https%253A%252F%252Fwww.ti.com%252Fstore%252Fti%252Fen%252Fp%252Fproduct%252F%253Fp%253DTPS61200DRCR)
1MOhm resistor - RCC04021M00FKED (https://www.vishay.com/docs/20066/rcce3.pdf)
180kOhm resistor - RTT03184JTP (https://datasheet.lcsc.com/szlcsc/1811081933_RALEC-RTT03184JTP_C103362.pdf)
2.2uH inductor - CKCS5040-2.2uH/M-2131 (https://datasheet.lcsc.com/szlcsc/1912111437_CENKER-CKCS5040-2-2uH-M-2131_C354604.pdf)
10uF capacitor - RDEC71H106K3K1H03B (https://www.mouser.co.uk/datasheet/2/281/RDE_X7R_X7S_25V-100V_E-1671041.pdf)
1uF capacitor - RDER72A105K2M1H03A (https://www.mouser.co.uk/datasheet/2/281/c49e-506.pdf)

The off-the-shelf board is from SparkFun: https://www.sparkfun.com/products/10255
I shorted the UVLO as I didn't need it, and set it to 3.3V. I've also tried it on 5V and had the same issue.
The schematic for the circuit I designed:

The schematic for the off-the-shelf module:

Thanks all for your help in advance.
Cheers!


texts: Zero crossing detection circuit correct?

texts:
I am working on a DIY AC dimmer circuit with arduino.
This project is part of the AC dimmer circuit as mentioned here
Since, I was stuck in so thought of retracing my steps and checking each part of the circuit and then only moving further ( to the triac part ).
Turns out I am not able to do zero crossing detection even.
My code in arduino :
int led_to_glow = 12;

void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  attachInterrupt(digitalPinToInterrupt(2), zero_crosss_int, RISING);  // Choose the zero cross interrupt # from the table above
}

//the interrupt function must take no parameters and return nothing
void zero_crosss_int(){
  digitalWrite(led_to_glow, HIGH);
  delayMicroseconds(10);
  digitalWrite(led_to_glow, LOW);
  delayMicroseconds(10);
}

void loop()  {
}

Following is the circuit diagram :

Now, I am a newbie in DIY projects and since this circuit wasn't working so, I thought I would post my breadboard circuit here too.
Please have a look into the physical circuit.

( I have erased the irrelevant parts of the circuit )
A little bit of explanation ( cause maybe the diagram isn't clear enough )
The yellow jumper wire from PC 817 is sent as interrupt to the arduino's digital pin 2 ( as can be seen in the diagram ).
The arduino detects the RISING signal on it and calls the ISR.
I have checked the output on the pins of PC 817 going to the arduino ( using a multimeter ) , it gives ~10 V.
I have added a common ground and VCC from arduino , as later in the AC dimmer circuit it's going to be used ( and my understanding is that wherever VCC is of arduino , gnd also must be of arduino and not from somewhere else , right ? ).
Thanks.
Sizu
Update 1 :
I have changed PC 817 to 4N25 ( as I found later that I had that component )
I have added a resistor to the input of 4n25 which inputs 2 V ( I am considering a higher resistor as the max forward voltage for 4n25 is 1.5V )
YELLOW Wire is directly connected to arduino digital pin 2 ( i.e. INT0 )

Update 2 :
As it turns out, when AC is switched off, voltage drop between yellow wire ( interrupt pin ) and gnd of arduino is 5V DC , whereas when AC is turned on it's 0.54-0.55 V , any reason why ?
I have also tried
attachInterrupt(digitalPinToInterrupt(2), zero_crosss_int, FALLING);  // Choose the zero cross interrupt # from the table above

I changed RISING to FALLING, it still didn't work.
Hopefully Solved :
I got to glow the LED, I forgot to define LED's pin as the output pin in the arduino code but then also it glows very faintly and even multimeter can't find the potential drop across the LED
So the new code looks like this :
pinMode(12, OUTPUT);
attachInterrupt(0, ledBlink, FALLING);  // Choose the zero cross interrupt # from the table above
}

Note :
Falling / RISING / CHANGE ( all 3 worked but I think FALLING should be used cause of the pull up resistor )


texts: Opamp driving 24V signal through long wire

texts: I have an opamp working as comparator that creates a 24V pulse signal (appx. 400ms duration) that needs to go through a wire of 10-20m length. Is a normal opamp capable of driving this or is there a certain common circuit to achieve this?


texts: How can I get the actual heat values from a thermal camera and know the pixel values?

texts:
I'm working the the FLIR thermal camera and using the code provided by Pure Engineering. I've recently run into a problem with the images provided by the camera because I realized that the pixels are relative to each other. Meaning that the hottest object in the image will have the lightest color regardless of what the actual heat of the object is.

This is a major problem for me because I'm trying to determine if someone is in the object and can't do that if the pixel values are changing relative to the amount of heat in the image. I tried looking at the code and figuring out how to modify it to give me actual heat values.

Has anyone here worked with the FLIR before and know how to do this? Or can you try looking at the code, and telling me what I could change to get actual heat values.


texts: Did I mess up my lab experiment ? (active low pass filter)

texts: This is the table of the readings and I have worked out the gain which is $$\frac{Vout}{Vin}$$ and I got all 5 at the beginning ... but I also remember that the values of the resistors in the feedback loop determine the gain, which supposed to be 10, does that mean I totally messed up everything ?


texts: Does this photodiode need an operational amplifier?

texts:
I'm trying to make a circuit for a pulse watch, which should be capable of measuring blood SpO2. I use 2 LEDs for each wavelength (respectively 660nm and 940nm) to shine at the upper wrist.
The reflected light is supposed to be picked up by the following photodiode:
https://dk.farnell.com/hamamatsu/s1223/photodiode-pin-to-5/dp/1495587

Everything should be wired to my Arduino and the supplied voltage is 5V.

Below you can see the circuit:

Do you think I will need any operational amplifier for this photodiode? - In the case of yes, since I'm new to this, which one would you recommend?


texts: What's the requirement to DIY PD aware USB connector?

texts:
According to some research, I should be able to pull +12v from a USB power source assuming my device is some how telling the power source that it is ready to receive +12v?

I've seen a YouTube clip (can't find it conveniently enough tho) of a kid putting a resistor across two wires on a stripped USB cable to achieve something along these lines.

So my question is, how do you instruct the power source to send +12v (1.5A is fine) or is this even possible?


texts: Time constant of inverting amplifier, filter

texts:
simulate this circuit – Schematic created using CircuitLab

I want to calculate the time constant τ of the filter. Can anybody help me?


texts: How to determine the frequency of input signal from Sensor to ADC?

texts:
I am using a Pressure Sensor that gives out an Analog Output of 0V to 10V depending upon the sensed pressure.

I am trying to design a filter (or at least determine some starting RC values) for the anti-aliasing stage before the signal from the sensor is fed into my ADC.

Is the frequency 0V, i.e. DC here?

My specific question is - what is the bandwidth / frequency range at which I need to evaluate the driving Op Amp A1 at?


texts: Why is electron concentration zero at collector side of the base in BJT transistor? And if electron concentration decreases with distance and becomes zero at the end base region how can it produce considerable amount of collector current?


texts: Confusion about connection/symbol to air-flow switch

texts:
I am interested in using an air-flow dependent switch. Luckily, they make those:

http://www.spx.com/nl/assets/pdf/SPX_LS_and_FS_Series_en.pdf

Unfortunately the pinout/internal circuit is not very clear to me, and the documentation doesn't explicitly spell it out:

As I understand from reading the documentation, I need to apply a voltage to the "heater" which heats up an internal thermal element. If the element gets too hot (ie there is no airflow cooling it down), a switch will either open or close (depending on the part number).

Which pins are the heater, and which pins are the switch? I think pin 5 looks the most similar to a relay contact symbol, but then again the symbol between pin 2 and 3 looks like a bimetallic contactor which are also used as thermal-switches.

Any help?


texts: Can I use common cathode PLCC 4 led to replace common anode PLCC 4 led?

texts:
I need to replace the led on my car gear shifter.
From my research, I understand that I need to get the common anode PLCC 4 3528 led with green color.
However, the seller sent me the common cathode one.
The question is can I use the common cathode led to replace the original common anode led?
My idea is to put 1 anode and 1 cathode in correct orientation and left the 2 anode unsoldered.
The circuit board is look like this

Thanks in advance


texts: Connecting a microcontroller to USB interface

texts: Currently I have the following microcontroller Atmel 89C61RD2 through a max 232 chip to RS232 interface. I would like to have an extra connection to a USB interface also. How can I do that? I would like to retain the same microcontroller and change only the max 232 chip.


texts: Interrupt Service Routine in C - function at specific address

texts:
I need to add an Interrupt Service Routine (ISR) to existing code in C for a PIC18F4620 and a PIC18F46K22. As you can see in section 9 (of both datasheets), these devices have multiple interrupt vectors: 0x0008 for high priority interrupts, 0x0018 for low priority interrupts.

I'd like to have an answer which is useful in many cases, so the question would be: how can I make a function on a specific program memory address? For the ISR, this address would be 0x0008 or 0x0018.

If it's of any use, I'm using the MPLAB C18 compiler, v3.44.

Related: C coding design - function pointers?


texts: Do I need to Reduce the Width of a Power Trace for Thermal Relief When it's Passing Through a Pin on the Chip?

texts:
I'm routing a PCB. Currently, all power traces are 20 mils. A QFP chip on the board requires multiple voltage rails to operate, I found the easiest solution is passing a power trace through a pin on the chip (the 1.8VI net in the screenshot).

However, it means the trace is as wide as the pin itself. Will it acting as a heatsink and create a solderability / thermal balance problem in hand soldering or reduce the yield in reflow soldering? Should I reduce the trace width when it's passing a pin for thermal relief?


texts: I was looking around for RF power transistors expecting them to have around the same price as the IRFP250 and I noticed the immense price. A 160 watt UHF dual MOSFET was 70$. What characteristics make the high-frequency power transistors a lot more pricy then others?


texts:
I have been taking current lectures, but I'm confused about how must be taking the reads, using the scale selector as show next

there is 310 number, but this are 310mA?
I almost never take current.


texts:
Below is a CMOS circuit for an inverter (or NOT gate). According to the book I am reading, when \$V_{x} = V_{supply}\$,  \$T_{1}\$ will be turned off and \$T_{2}\$ will be turned on. So \$T_{2}\$ will pull the output \$V_{f}\$ down to 0.
But I have been wondering, since \$T_{1}\$ is turned off, there will be no current from \$V_{supply}\$ through \$T_{1}\$ to \$V_{f}\$. If I consider \$T_{1}\$ as a resistor, there will be no voltage drop through it. So why \$V_{f}\$ choose to be 0 rather than \$V_{supply}\$ ? I guess I missed some important concept.


texts: Setting external oscillator for atmega328p

texts:
I'm trying to use a 8MHz Oscillator on an atmega328p. this a part of the whole schematic :

to that I've set the Fuse byte as calculated

then I've set the calculate values in the project :

To make sure that the uc ist correctly runnion on 8MHz, since I don't have an oscilloscope, I'm trying to toggle a LED each 1 sec, here is the code I've wrote for that :

#define F_CPU 8000000
#include <avr/io.h>
#include <util/delay.h>
int main(void)
{

DDRD |= (1 << PD5);
    while(1){
        PORTD |= (1 << PD5);
        _delay_ms(1000);
        PORTD &= ~(1 << PD5);
        _delay_ms(1000);
    }
    return 0;
    }

As far as I can see the lED take 8sec to change its status ! when I change the value of F_CPU  to 1MHz  the toggle is than correct, which means to me that I'm still running the internal oscillator ?

Any idea what I'm missing here ?
thanks in advance !


texts: Good resources/books for electromagnetics and other advanced concepts

texts:
I'm looking for some good resource that teaches the fundamental concepts behind electronics. I'm not looking for a beginner book. I'm already in the final year of my Electronics and Telecommunication course, so pre-requisites are not a problem.

I'll explain my situation. As long as we're talking about Ohm's law and DC circuits, everything seems to make sense. However, as we introduce inductors, capacitors, AC sources and components, we start talking about fields instead of just "currents" or "charges".

I understand that fundamental laws like KCL or KVL are just abstractions over Maxwell's equations to make our lives easier.

So, I'm looking for a book that will help me understand everything that "happened" in between the simple Ohm's law abstraction and Maxwell's theory. Things like how we can view simple DC circuits using Maxwell's laws. Things like what divergence and curl really represent, and what was the motivation of introducing such concepts.

Is there any such resource/books? I know I'm being a little vague. But I think you understanding what I'm looking for here.


texts: How can I reduce an oscilloscope's bandwidth to that of an Arduino's ADC?

texts:
The typical sample rate of the Arduino Uno's ADC is ~10KSa/s. Yes it can be overclocked, but lets just consider the normal situation.  I'd like to 'simulate' the levels of a large random signal that the ADC might see on a digital oscilloscope. This way I can see the level on screen that the ADC would return from sampling.

So if I manually set my 'scope to 10kSa/s, will that be the same as the Arduino, other than the bit depth?


texts:
I was looking for a way to make the current flow the otherway around through a DC-Motor while only using 1 Relay. Yet after many sketches I came to the conclusion I could not do this without shorting the circuit.

Is this simply not possible? If so I will just use 2 and its very easy.

Why am I trying this? Keeping the circuit simple by using very few parts.

The relay I am using

Thanks in advance,

Anton


texts: Intuition for resonant, natural, and oscillatory frequencies of RLC circuits?

texts:
I can't seem to get these concepts straight.

To start, what are the official definitions of each?

My current understanding is that:
\$ w_0 = \sqrt{\frac{1}{LC}} \$ is the natural (and resonant?) frequency that an undriven LC circuit (or a RLC circuit with no damping) oscillates at. When we add nonzero damping though, we then get that the natural frequency that the system tends to oscillate at is \$ s = \frac{R}{2L} \pm \sqrt{\frac{R}{2L}^2 - w_0^2} \$.

(Then there is the damped natural frequency \$ w_d = \sqrt{w_0^2-\frac{R}{2L}^2} \$ for an underdamped system -- where does this come in?)

Why are there two natural frequencies -- in real life which one does the circuit actually oscillate at? Are these the same natural frequencies for ANY configuration of R, L, C (series, parallel, more complex setups, etc)? Is yes, why does that intuitively make sense? If not, is there any intuition behind the different expressions for natural frequency for series/parallel? (Is the freq greater or less, and how can we roughly judge from a circuit schematic whether its natural frequency will be high/low?)

In the nonzero damping case, does \$ w_0 \$ just become an abstract quantity? Why is it that when we have RLC filters, the peak frequency (where we have the greatest response) is still \$ w_0 \$ and not the more complex expression we have above?

Where does quality factor come into this? Is it always \$ \frac{w_0L}{R} \$ regardless of the circuit setup? (again, what's the intuition to this answer?)

Correct any misconceptions I may have -- I'd love to understand this topic more deeply. Thanks so much in advance!


texts: Programming a microcontroller with another microcontroller

texts:
I'm looking into using a PIC24FJ256GB106 to program three other of the same microcontroller.

So this is how it should work:

The program is sent across through serial to the master/programming PIC
That PIC receives it and uses ICSP to program the other PICs through the five ICSP lines (I/Os)

Before you say it, no, bootloaders are not an option.

Essentially, I'm looking for a program to make a microcontoller act like a PICkit/ICSP programmer. How would one find the code to make this magic happen?


texts: How do I match a battery pack voltage to my solar panels?

texts:
We're building an autonomous boat which should be powered by solar panels. We want to put two 100W solar panels on it. Most panels I see are 18V and for redundancy we want to link them in parallel. That way when one solar panel breaks at sea, we still have the other one to finish the mission.
We're now looking into what kind of battery we are going to build for it. I read somewhere that the solar panel should have a 40% to 80% higher voltage than the battery. That means that a 12V battery pack should be logical. And in between the solar panels and the battery pack we'll put an MPPT charge controller.
My question is; does all this make sense? Is it true that the solar panel voltage should always be 40% to 80% higher than the battery pack? Or can I also use an 18V solar panel to power for example a 5S li-ion (nominal voltage of 18.5V and a max of 20.5V)?
All tips are welcome!


texts: ESD protection for signals routed through multiple boards

texts:
I have a few questions regarding ESD protection:

If a particular signal is routed through multiple boards (through connectors), do we need to place ESD diodes at each port (connectors)? For example, if a keypad button is on a separate board and then the signal is routed through connector on the board to another board, do we need to add ESD protection at both the ports (Considering connectors also have certain current ratings)? Another example can be let us say that there is a sensor connected to the main controller board over I2C bus, does this need ESD protection on the sensor board and the main controller board (as both the boards are connected through connectors on both boards)?

Now, what if these connectors are not exposed to the user at all in the product, do we still need to add ESD protection (considering these ports will be handled and assembled during manufacturing and maybe sometimes very rarely to service). Does this change the answer for question 1?

What if the same signal lines are exposed through 2 different ports/connectors. Would a single ESD for each signal close to both connectors suffice?

Adding multiple ESD protections all increases capacitance on the lines, so need to check that the combined capacitance does not impact the signal (at a particular speed). Am I right?

Do we need to add ESD protection for antenna input as well. How important would this be compared to digital signals? The reason I am this question is because, I have seen some products which are CE, FCC certified without ESD protection on the antenna input (GPS, Cellular, BLE). I know that there are some very low capacitance ESD from Nexperia and other such companies for this purpose. In reality, how important is this?


texts: How do you measure frequency using a microcontroller?

texts: Is it possible to use a microcontroller to read an input frequency? Please explain how?


texts:
I have a source (1) of power which can be adjusted from 1-5 Volts and 40 mAmps.
I have another source (2) of power which delivers a constant 5 Volts and 400 mAmps.

I want to build a circuit which takes source (1) and source (2) as input and deliver a output voltage based on source (1) and amps should be based on source (2).

Input => source (1) [1-5 volts and 40 mA] and source (2) [5 volts and 400 mA]
Output => 1-5 volts (same as what is specified in source 1) and
          400 mA (same as source 2)

I am new to electronics and would need your help with this.


texts: C.P (unknown abbreviation, control cabinet drawing)

texts:
I don't know what "C.P" might stand for in a HVAC control cabinet drawing. Could anyone have a quick look? I'm not an electrical engineer, but a translator. Not sure what electrical component is designated this way. All I know is that the system is manufactured by a Korean company named Kiturami Bumyang Air Conditioning Co., Ltd. Please, see the picture attached, item No.2.
Sorry for poor quality, that's how it is in the manual.


texts:
I have the following simple circuit to obtain characteristics of an N type MOSFET.

The gate voltage will be swept from 3 to 6 Volts while the drain voltage will be swept from 0 to 0.5 Volts to obtain ID VS VDS graph for different VGS values. The threshold voltage is calculated from the SAT condition with a different setup and the MOS will always be in triode region with these voltage sweep values.

I am asked to find "the most precise" Kn which is equal to ID/(VDS *( VGS-VT))(Dropping VDS2 for convenience). But what is meant by "the most precise" value?


texts: Need help with a DC-DC converter using a MC34063

texts:
I'm trying to make a DC/DC converter from 12V to 5V using a MC34063.  I found an old cell phone car charger and removed everything and set it up on my breadboard.  I'm getting 5V out but only  0.12A.  I checked the car charger before I took it out and it was 5V and 1.0A.  I set it up exactly as in this image:

I'm not sure where I could have messed it up.


texts:
I'm searching for a decimal counter ic which I can controll with PWM or another signal.
The basic counting ic is a 4017 I think, but in the Datasheet you can see that every new clock high pulse the ic counts, with no delay between it.

but I'm looking for an IC that counts and sets the outputs like this. Clock high 1 high, clock low 1 low, clock high 2 high, clock low 2 low... and so on

I hope you understand what I mean, and help me to solve my problem.


texts: IRF520 MOSFET Transistor to convert 3.3v to 5v?

texts:
I'm just starting to poke around with ways to turn 3.3v in to 5v and I keep coming across MOSFET transistors.

I happen to have an IRF520 MOSFET N-Channel Transistor lying around and am wondering if I can somehow use that to trigger a 5V relay switch.

If that's doable, jow would I hook that up so I can use a digital out on a 3.3v microcontroller to ultimately trigger that 5V relay?


texts:
I am trying to power a pair of TEC (thermo-electric cooler) using Arduino.  I came across this guide that is used to power one.

Because I have two, I want to know if I can still use something such as this mosfet (we want to supply ~12 A).  It says a drain current of 30 A, so I think that I could, but I have never worked with this high of current or power, and do not want to fry something or destroy the board.


texts: How to configure an opamp for differential mode to trip an NPN?

texts:
I'm learning op-amps at the moment, so try to bear with me because this text will most likely contain a lots of errors.

I have a chip resistor, 10mohm, that I intend to use as a shunt for measuring current. Vcc = 5V, I = 2A normally. I = 2.5A means things are going wrong, 3A = dead wrong. So, somehow I want to watch the voltage drop of the resistor, and when the current goes to high (I haven't set a limit yet, but let's say 2.5A) I want an NPN to conduct, just for the sake of testing.

So, I've got two measuring points on the resistor: Rs1 and Rs2. 2.5A with 10mohm is 25mV. That is, when the voltage drop over Rs1 and Rs2 > 25mV, trip the NPN. If voltage drop < 25mV, do nothing.

Rs1 and Rs2 goes to an opamp's in+ and in-. Other than that, I'm stuck. I am completely clueless what sort of feedback network I'm supposed to use to achieve what I want. Googling for "opamp differential amplifier" gives me http://www.electronics-tutorials.ws/opamp/opamp_5.html which seems to be basic enough for me to understand, but I've been reading this paragraph five times now and I just don't get it:

Then differential amplifiers amplify the difference between two
voltages making this type of operational amplifier circuit a
Subtractor unlike a summing amplifier which adds or sums together
the input voltages. This type of operational amplifier circuit is
commonly known as a Differential Amplifier configuration and is
shown below

This sounds like it's what I'm trying to achieve, but what does it mean that the circuit is a "Substractor"? If I'm supposed to amplify the difference and letting the 25mV-level trip the NPN-base, what's substracting got to do with it?

I'm clueless, really.

Is differential amplifier the kind of feedback type I'm searching for here, for my testing?


texts: How do I find the Millman theorem in this op-amp circuit?

texts:
So I have this circuit and I want to find the millman theorem of it. I started with it and I got here.
I have E2 connected to the ground and E1 connected to a voltage source V1. So V+ = V1; and V- is where i got confused a little bit. So when I want to find V-, I have on the numerator ((0/R + Vs/R0 + Vs/R1 + Vs/R2) / (1/R + 1/R0 + 1/R1 + 1/R2))
Is that right? Is that what I should do or not?


texts: Datasheet specifying less than 0.1 uF decoupling capacitors

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The lmh6550 fully differential amplifier "requires" capacitors as shown:

The 0.1uF between rails makes sense, but I'm surprised at 10nF rather than 0.1uF to ground.  The part is relatively modern (mid-2000s) and anyway they're using 0.1uF elsewhere, so clearly the parts were available. They're also using 0603 in the reference design, so 0.1 uF would be a reasonable value given the footprint.
Is there an electrical reason for some of the capacitors to be smaller than 0.1uF?  I'm not very familiar with fully differential amplifiers, but it would create a lower AC impedance between the rails then to ground, although I don't know why that would be desirable.  Am I missing something or is this just some very specific cost optimization?


texts:
I'm confused.
The datasheet seems to say 3.3v, but I read (e.g., https://techexplorations.com/guides/esp32/begin/power/) that one may apply up to 12V to the 5V pin.
However the car runs at about 14.5V with the engine running.
So:

Will it work to power the ESP32 directly from the car?
Will a voltage regulator do or will it get too hot?
If a voltage regulator won't do then it'll have to be a buck converter, right?
Are there any microcontrollers (preferably with Bluetooth and CAN) that can be powered directly from a car?


texts: BJT how to explain in terms of conventional current flow?

texts:
Conventional current flow always confuses me.

For electron flow, i can explain how the BJT functions.
When there is a small current flow from Base to Emitter, more positive holes are created which reduces the depletion region.
Electrons from Emitter then diffuse across the depletion region and move through the Base-Collector depletion region which is thin.

How do i explain this in terms of conventional current flow?

Thanks


texts: Transformer output connected to another transformer. Measuring 'Real Power' at input of first transformer

texts:
I have a watt meter connected to the primary of one transformer to measure power. The output of this transformer is connected to the input of another transformer.

The watt meter is measuring the inductive load of the primary of the second transformer, as 'real power'. I figured I have to add a capacitor in parallel to the primary of the second transformer to filter out the current at the given frequency but I am not sure.

If I connect a load to the secondary of the second transformer, the reactance of the primary of the second transformer will change, in turn changing it's ability to filter out the frequency with the parallel capacitor.

Is what I am describing true? Or does it work differently? How are power lines avoiding experiencing 'real power' dissipation from transformers of appliances in our homes. I know transformers are inductive and give power back to the source. But in the double transformer test I describe the watt meter was measuring the 'apparent power' of the primary of the second transformer, as the the 'real power' in the 'eyes' of the primary of the first transformer. so if I measured voltage and current at the primary of the second transformer, I would multiply them to get an apparent power of 20VA. The watt meter would show 20Watts (real power) at the primary of the first transformer.

I hope that is clear. Thank you.


texts: Led works fine but Relay not working by bc547

texts: I want to drive a 5v relay with bc547. I am using 1k resistor at base but relay is not working. I replaced relay with a led but it is working fine. Resistance of relay coil is 70ohms. Please help. A rough diagram is shown.


texts: Need advice with pin connection of an LCD module

texts:
Hello. I am working on this LCD module, COG-C144MVGI-08.

Like in the image I uploaded, PIN 1, 4 and 12 are ground.

(Just in case you need the full datasheet :
https://www.avrfreaks.net/sites/default/files/COG-C144MVGI-08%20Full%20Spec.pdf)

The problem is, I overestimated the stress-tolerance of the pins and I broke PIN 1.

I think that I can just connect one of the GND pins, and it will work just fine.

Am I correct? I leave PIN 1 and 4 unconnected. Will the module work?


texts:
This is a simple motor made with a magnet, a battery and a copper coil.
I am curious to know how can it be explained using physics.
I know that the copper is diamagnetic but not enough that it can cause the coil to rotate.
I want to know why the coil rotates as the current flows in it.


texts: How to calculate the resistor value necessary for the columns 8x8 led matrix?

texts:
I am building an 8x8 led matrix using 5mm LEDs (3.2V, 20mA). I connect it to the arduino UNO through the I2C using the GPIO expander MCP23017. The circuit is as follows:

A matrix column is made up of 8 LEDs connected in series (am I right? are they not in series?). The forward current of an Led is 20mA and its forward voltage is 3.2V. I connect the VDD pin of the MCP23017 to the 5V pin of the arduino uno.
So, the resistor value I need to connect to a column so that the LEDs don't die out is (5V-(3.2V*8))/0.02, which is a negative value! Shouldn't I multiply 3.2V by 8? if not, why?


texts: Replacement MOSFET (in a different package)

texts:
I'm looking for a replacement MOSFET for the SI7460DP. It's a 60V 11A 0.0096 ohm MOSFET.

I don't think I can solder the PPAK, but a design I am using requires this fet. So I'd be okay with SOT-89, SOT-223, DPAK, SOIC-8 - anything with exposed leads - if it fits the requirements I'd be happy with it.

Any suggestions?


texts: Suitable protection for elements on power line

texts:
I am working on mini project with 555 timer. The LED diode is not a diode, but a 12V LED string. What happens if there is a sudden drop in voltage?

Motor will induce voltage of opposite polarity. The diode in darlingon transistor will bypass that voltage to the power line away from the IC. Will my diode on LED ring be ok or will be dead?