texts:
I am in general interested about how compiler and linker handle global variables. Here click it is explained that additional ROM is needed in case variable is initialized and not 0.
So wondering, why is it so. Excuse me for a newbie question, but why are they using the word "ROM" here. Or are they referring to the memory of flash, which acts like ROM?
As you see, I am having a bit of confusion. So any help would be appreciated.
Best regards


texts: Above is the output characteristics graph of IRFZ44N mosfet. As we can see, the output for various Vgs values are plotted. The highest two Vgs values (10v, 15v), have their Vds points halted below 10v whereas other Vgs values have their corresponding vds output going all the way above 10v. So is that means at vgs above 10v, the corresponding Vds output will be limited at that voltage range? Or else they are for some other reasons?


texts: Altium trouble between Schematic and PCB Design

texts:
Good morning!

First time poster, long time reader here. I am in the process of wrapping up my first Electrical Engineering internship with my final contribution to a product. This is the first time I've ever used Altium, and to be honest, I think it's terribly organized with all these libraries and rules that the program uses to stop even a simple design. I prefer Multisim and Ultiboard any day of the week, but alas, I had absolutely no say in which PCB design software this company chose to purchase a license for.

Anyways, to my problem. I am creating an LED circuit that's has a yellow/green pair of LEDs that alternately flash when AC power is allowed through. Extremely simple project, right? I thought so before having Altium dumped on me with no one here having much experience with it.

In the schematic below, I have a voltage input leading to a switch, the switch then branches out to the 2 LEDs. The logic behind the circuit is when the current is positive from the power source, the current is forced through the green LED pair, and if the current is negative from the power course, the current is forced through the yellow LED pair. Add in the high frequency that the equipment is providing for this portion of the circuit and you get quickly flashing green/yellow LEDs.

My problem arises when I try to transfer the schematic to the PCB design area. The ECO never allows me to have both the "Positive Current (switch-LED)" and the "Negative Current (switch-LED)" nets in my design. I'm guessing that the program thinks these nets are the same thing and is ignoring one of them.

The worst, and most frustrating for me, parts of this program is that it doesn't allow you to design as you please. Obviously there's a disconnect between me and this program, but that could be ignored if I could simply add the copper runs that I want without the program redirecting them from where I want to go.

Frankly, the problem I'm having could be stemming from anywhere and I can't find any proper help for this program. Any help you fine ladies and gents could provide me with would be absolutely wonderful. Until then, happy engineering!


texts: Measuring technique for bridge rectifier driven by function generator

texts:
I am confused about a problem I am having measuring the output of a full wave diode bridge rectifier driven by a function generator. I am only getting half of the output as if it where a half wave rectifier. This is only a problem when I hook up my o-scope.
This is just an experiment. I don't plan on driving any sort of real load.
Now the obvious answer here was that the both the generator and the scope where referenced to earth ground. I tried to solve this problem by floating the function generator through a 1:1 isolation transformer. I also used an adapter to prevent earth ground from being connected through. I confirmed there was no continuity between the ground shields of the BNC connectors of the generator and o-scope yet I got the same result.
At this point curiosity/frustration caused me to put caution to the wind and I tried to drive the rectifier directly through a toroidal transformer I had salvaged from some strip lighting that was rated for line voltage with 12V out. It worked as expected. I had both sides of the rectified signal.
So what is the difference between using this toroidal transformer and driving it from a function generator that I have floated using an isolation transformer.
I just ordered a caltest differential probe. I figure it will be a useful piece of gear to have one way or the other. Im hoping this might help to float the ground of the probe.
Update
I cant seem to reproduce the problem today. So I guess the problem was between the chair and oscilloscope. Sorry...
Just for the sake of completeness this was the setup:
Wall -> Powerstat 3PN1168 Variac -> Triad N-59MG Isolation Transformer -> (adapter to lift earth ground) -> SDG2042X Waveform Generator -> Diode Rectifier
Wall -> Rigol DS2202A -> RP3300A 10x Probe -> Diode Rectifier.
Lifting the earth ground with an adapter is necessary. Perhaps I was somehow missing this yesterday in swapping between different configurations. It does add a significant amount of 60Hz noise to the output of the function generator regardless if the output is turned on or not.


texts:
Why there is no general definition of time constant for 2nd or higher order systems , while 1st order systems have a proper definition of time constant.
is Time constant defined for every systems irrespective of their orders or it's only defined for 1st order systems ?


texts: How to make a circuit for DMX splitter notification LEDs?

texts:
I am trying to make a DMX splitter. Everything works now, but it would be somewhat useful to have notification LEDs, like in the example below.

For the input I could use one LED, which I either connect to the RS485 + or -. Which one does not matter, because if a DMX cable is connected the LED lights up.

However, for the outputs it does not matter if a DMX connector is attached, the LED always is on (because there is signal on the input going to the output).

How could I make a red/green or single color LED that would light up when an output connector is inserted to a DMX device?

(btw, for the input I used a transistor, to prevent a significant voltage drop from the real signal going to the LED).

I'm not asking to recreate it exactly, I just want to have a LED that lights/blinks when a signal is sent to a DMX output.

Update

I created a new question (Prototyping a DMX splitter, the schematics I copied here for completeness:

Circuit where the above is based upon (for the sake of this question there is no functional difference)

Credits to J. Mack.


texts: What is the equivalent of compile of modelsim in quartus prime?

texts:
In ModelSim, I can click compile and ModelSim will compile it quickly, around 1 or 2 seconds.

But in Quartus Prime, I need to run Analysis & Elaboration or Analysis & Synthesis which runs more than 40 seconds for the same code which takes only 1 or 2 seconds to compile in ModelSim.

I know Analysis & Synthesis will perform Synthesis as well, but sometimes I need to just check whether my code has error or not without the need to synthesis.

Until now, I have been going back and forward between those two CAD tools.

Any suggestion will be appreciated.


texts: spy/monitor and decode spi protocol between master and slave

texts:
I often find my self in a situation when i need to debug systems of a MCU and other device which comunicate by SPI interface.
most of the times we use a logic analyzer between the master and the slave , which can decode to hex or binary , its very time comsuming.
is there a tool where i can define a custom protocol , so the frames are decoded and automaticaly?


texts: Controllability and Observability of SFG by intuition

texts:
For the below block diagram is it possible to conclude controllability by tracing the path from inputs to state variable , similarly to conclude observability by tracing path from state variable to output ? Im looking for this intuitive method based on definition , the matrix check for C and O for the problem gives the answer to be B.

Adding one more similar problem where the matrix check concludes that the system is controllable but I dont see any path from input to the state variables rather only path from SV to outputs.


texts: Is it possible for a circuit to heat up enough to bridge solder?

texts:
I have two lights that I use for working on stuff in my shop, and it seems like the PCB heated up enough that solder between two leads actually melted and bridged itself.
The light was working great until today, and suddenly got very dim - so I cracked it open to check.
Is there any reason besides heat and extra solder that this would happen?
I'm not sure what to think otherwise, but it does seem like there should be a heatsink on that LM317 at the least. Curious if this is a common occurrence that can be avoided or if it's a fluke.
Here's what the bridge of the bad light looks like:

Here's the bottom of the good light PCB:

Here's the board itself. Its used to drive 90 SMD LED's in series with ~250VDC from 120VAC/58mA

Here is a better lit picture of the top of the board. This is a picture of the actual bad board. The first one was a top image of the good board - which is the same but different color and brand components for some reason. The leads going to the LED's are disconnected so I could move it around easier.

Here's a closer closeup by the LM317 where it bridged as requested.

Edit: For anyone curious, I did fix the bridge and it seems like the 317 is bad. Lights are still dim, and DC output is at ~325 where the working one is at 250.


texts: Some pads on a PCB are marked in clusters and I can't understand which one is which

texts:
I'm trying to find some certain pads on a monitor circuit board.

I found a cluster of pads that's marked as "A", I assume because there's no space to write what every single one is. And on the far right of the pad, there's a marking that says "a", and there are all the markings listed. The problem is - they're formatted as a list, so basically just one under another. How should I know which one is which? They're not just next to each other, some are on top or on bottom. So I can't just count them and proceed. Please, can you tell me which one is which? (Screenshot below)

I searched for "reference designators clusters" but found nothing.


texts:
I am searching for a method for multiplexing 3 DC voltage sources (each ±10V p-p) to my ADC pre-amplifier circuit.

My requirement is that the multiplexer should not inject excessive noise into the readings. It should be as noise free as possible, like 1 µV peak to peak max.

I'm considering building my multiplexer with switches or relays. For switch ADG1401 looks promising (however, in the data sheet I couldn't find noise related data)

Can a relay be more noise free? Do you have advice about other solutions for this requirement?


texts: How to interpret the stepper motor voltage requirement?

texts:
I have a 8HS11-0204S stepper motor and need to match a driver to it. HERE it says that the recommended voltage for driving it is 12-24V. But if you open the (feeble) DATASHEET, it says that the rated voltage is 4.8V, which is confirmed by multiplying the operating current with phase resistance. If this is true, then as I understand any driver that requires higher minimum input voltage than 4.8V is unsuitable.

Which value should I look at when choosing a driver? Is looking at the rated voltage enough?


texts: I create a arduino robot car and I used the power bank for the supply of arduino. And I used L293D Motor shield arduino and the supply I used is the 4pcs of 18650 battery, I series the 2 pairs of the battery and parallel the pair. In calculation, 3.7V x 2 = 7.4V and the current increase. I want to have a charger of my 7.4V battery and how to charge it?


texts: Low Noise Amplifier and Input/Output Phase

texts:
I've been designing LNAs for a brief time and I was wondering why the input and output phases is usually never cared for or measured when measuring the specs of the LNA. For example, the only specs we cared about when designing the LNA were gain, intermodulation point (3rd), and power.

I guess this question would also apply to general use of amplifiers such as Op-Amps (with feedback) but why is phase for different frequencies not cared about (except for 180 deg frequency point for checking stability) or is never measured? I would assume that if a signal consisted of a bandwidth from freq 'a' to freq 'b', you would need the entire bandwidth of frequencies, from input to output, to all have the same phase (i.e., not a single or more frequencies are delayed/ahead) in order to demodulate the entire bandwidth of signal.


texts: Meanwell LDH-45 LEDs Glowing When Controller is Off

texts:
I'm using a Meanwell LDH-45B-350 Dali driver for currently 4 Bridgelux BXRE-30G0800-D-73 LEDs with forward voltage of 18v at 350mA. The problem is when I switch off the driver, the LEDs still glow a little bit.

I saw in the datasheet today this paragraph in really bad English:

  At dim off,LDH output  voltage  will  drop  to  the  same  level  as  input  voltage.To  get  luminaires  complete  dark, A please make luminaires  are  light  off  when  they  are  driving  by  the  input  voltage.

The driver is fed by 24V, does this mean that with these LEDs there is no solution for this problem?

I got the B version and 24v supply because it can drive my 7 LEDs together. The A version can only drive 4.


texts: Getting Strange Readings From a Multiplexer

texts:
I'm trying to build a simple gamepad controller to learn more about multiplexers (in this case a SN74LS251. This is how I'm wiring it:

And this is the code I'm using to get the button states:

// Pins.
unsigned int y = 8;
unsigned int a = 9;
unsigned int b = 10;
unsigned int c = 11;

// Gamepad states.
unsigned int gamepad[2][4];

/**
 *  The usual Arduino setup.
 */
void setup() {
  // Set pin modes.
  pinMode(y, INPUT);
  pinMode(a, OUTPUT);
  pinMode(b, OUTPUT);
  pinMode(c, OUTPUT);

  // Set select pins LOW.
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);

  // Begin the Serial connection for debugging.
  Serial.begin(9600);
}

/**
 *  Set the select pins in the multiplexer.
 *
 *  @param a_stt Select pin A state.
 *  @param b_stt Select pin B state.
 *  @param c_stt Select pin C state.
 */
void multiplex_set(unsigned int a_stt, unsigned int b_stt, unsigned int c_stt) {
  digitalWrite(a, a_stt);
  digitalWrite(b, b_stt);
  digitalWrite(c, c_stt);
}

/**
 *  Get all the Gamepad states and put them into the result array.
 */
void get_gamepad_states() {
  // Left Gamepad.
  multiplex_set(LOW, LOW, LOW);
  gamepad[0][0] = digitalRead(y);
  multiplex_set(HIGH, LOW, LOW);
  gamepad[0][1] = digitalRead(y);
  multiplex_set(LOW, HIGH, LOW);
  gamepad[0][2] = digitalRead(y);
  multiplex_set(HIGH, HIGH, LOW);
  gamepad[0][3] = digitalRead(y);

  // Right Gamepad.
  multiplex_set(LOW, LOW, HIGH);
  gamepad[1][0] = digitalRead(y);
  multiplex_set(HIGH, LOW, HIGH);
  gamepad[1][1] = digitalRead(y);
  multiplex_set(LOW, HIGH, HIGH);
  gamepad[1][2] = digitalRead(y);
  multiplex_set(HIGH, HIGH, HIGH);
  gamepad[1][3] = digitalRead(y);
}

/**
 *  The usual Arduino loop.
 */
void loop() {
  get_gamepad_states();

  for (unsigned int i = 0; i < 2; i++) {
    if (i == 0) {
      Serial.println("LEFT");
    } else {
      Serial.println("RIGHT");
    }

    Serial.print("  Up: ");
    Serial.println(gamepad[i][0]);
    Serial.print("  Right: ");
    Serial.println(gamepad[i][1]);
    Serial.print("  Down: ");
    Serial.println(gamepad[i][2]);
    Serial.print("  Left: ");
    Serial.println(gamepad[i][3]);
    Serial.println("");
  }

  delay(500);
}

It was working last week when I tried it for the first time, but when I went to rebuild it today I started getting strange (and completely incorrect) readings like these (no buttons were pressed during this test and I still got some HIGHs for no reason):

LEFT
  Up: 0
  Right: 0
  Down: 0
  Left: 0

RIGHT
  Up: 0
  Right: 0
  Down: 0
  Left: 1

LEFT
  Up: 0
  Right: 0
  Down: 0
  Left: 0

RIGHT
  Up: 0
  Right: 0
  Down: 0
  Left: 0

LEFT
  Up: 0
  Right: 0
  Down: 0
  Left: 0

RIGHT
  Up: 0
  Right: 0
  Down: 0
  Left: 0

Also if I press a button nothing happens. Even if I put the Enable pin HIGH I'll still get the same pattern. What's wrong?


texts: Advice Running 3 10W 12V COB LED on a 12v7AH lead acid battery

texts:
I am planning on buying this LED

http://www.ebay.com/itm/Hot-10W-12V-24V-1000LM-Warm-Pure-White-COB-LED-Lamp-Light-Bulb-120x36MM-THUS-/261502498315?pt=LH_DefaultDomain_0&var=&hash=item3ce2c3760b

This is for my my project of doing a video light that I can carry to the field. Since these are 10W 12V-14v, my math (P/V = I) (10/14) equals to 710mA (assuming 10W is achieved at 14v).

My plan is to buy 3 of them and wire them up in parallel. That means, (.71mA * 3) I will have a load of 2.13A for the project. If I compute this correct (7A/3.2A), I will have around 3.2Hr of use before I run out of juice. The 7A in the eq because I'm planning on using a 12v7ah lead acid battery, its a deep cycle battery. The reason I am going to use this is because they are cheap and available, though heavy, it's tolerable.

Although these computations is accurate if I'm going to use it at full capacity. But since I can't drive the LEDs at full capacity because my supply is only 12v. Also, I'm going also to use a step-down motor with a potentiometer to dim it when needed.

http://www.ebay.com/itm/1-25V-36V-5A-DC-DC-Step-Down-Adjustable-Power-Supply-Module-Buck-Converter-/191376540796?pt=LH_DefaultDomain_2&hash=item2c8eee447c

All-in all, I'm hoping if anyone can advise me of anything I had missed? Are my computations correct?


texts: Electronic circuit simulator for tracing current paths?

texts:
I've started learning electronics a few weeks ago and almost everything was pretty straightforward to me. I was able to understand with relative ease the fundamentals of a basic circuits and there working process. However, recently all the schematics in my textbook became a lot more complicated and all of a sudden a new symbol begun to appear more and more often ( the ground symbol ), I am no longer able to trace the paths of the current in those schematics, because to me they look incomplete ( like there is no wires closing the circuit ).

I can't determine current flow and it's direction anymore and where it started in the first place, also, it appears to me that with such more complicated schematics more than one current can flow in a wire at the same time, sometime in opposite directions, so, basically it's pretty messy. I Google searched for techniques regarding my issue and many people who were sharing their thoughts over it said that it is a good idea to buy a electronic circuit simulator. Well, I did, I bought this one TINA and I spent $239. It turns out that it doesn't actually trace the paths, all it does is, for a given values of different electronic elements connected in the circuit, to compute the output and that's useful but it it is not what I am looking for. I am looking for a software which, for instance,  to do something like this but in a more accurate fashion:

If there isn't any application able to perform this task, can you favor a technique which can help me. Thanks in advance.


texts: Can i use a single NodeMCU IO pin to give select input to multiple 74HC157 ICs(2x1 mux ic)?

texts:
I have atleast '6' 74HC157 ICs in my design, with the select lines of all the 6 ICs tied up together(Fig1).I wish to give a logic high or logic low to the select line using just one NodeMCU IO pin. Can I do that?

I am doubtful as the maximum drain/sink current of a NodeMCU IO pin is 12mA and the datasheet of the IC says that Iol and Ioh for the IC is 5.2mA.

Hence if all 6 ICs were to be connected to a single IO pin, does that indicate a possibility of (5.2*6)mA of current sinking or sourcing from the NodeMCU IO pin?


texts: Given ± 15 is the supply voltage for two opAmps, what will Vo be for the following specific equation?

texts:
I got this equation for a summer circuit output voltage fed into an inverting opAmp. Both opAmps have supply voltage of ±15 V.

Vout = -6*V1-30*V2-60*V3

I got Vout = -390 mV.

I know that the ± 15 volts is there to tell a range of possible voltages; Vout cannot be out of the supply range.

However, I don't understand whether the range for possible Vout is 0-30 V or -15V to +15 V.

Here is the question.


texts: What is the transfer function of n-cascaded RC filters?

texts:
Is there an explicit formulation for n-cascaded RC filters?

The resistor and capacitor values are not necessarily same. Assume that:
\$ R_i \neq R_j \$ and \$ C_i \neq C_j \$ for \$ i \neq j\$ and \$ 1 \leq i,j \leq n \$.

I built a 5th degree filter with \$R_i=1k\Omega\$, \$C_i=1\mu F\$ and \$V_{in}=1\sin(2\pi \times 1kHz) \; V\$. The output signal was nearly smooth for a \$1k\Omega\$ lead. And rise of the output signal was visible by eye when the input was a step signal.

I tried to find transfer response of this 5th order filter, but after the 3rd order, the size of A4 paper became insufficient for writing the expressions.


texts: How to choose protection resistor for I2c devices

texts:
Note : I am a beginner.
I noticed on the STM32-410RB datasheet page 100 (https://www.st.com/resource/en/datasheet/stm32f410rb.pdf), protection resistors were used in series on the SDA and SCL line.

Further research showed that using protection resistors for devices connected to I2C is commonplace. How would I choose/calculate what resistor to to "protect devices" on the I2C bus or generally?
Could this method be: (input voltage  - Forward voltage)/ Forward current ? This was the method I found for protecting and LED using a resistor in series, would this be the same for the I2C bus?


texts: What can happen if 24vdc is applied to an Ethernet port?

texts:
We have a device with two RJ45 ports. One of these ports is for receiving 24vdc on pins 7(-) and 8(+) to power the device. The other RJ45 port is an Ethernet connection. The ports are of course labelled to advise against such a thing, but is there guaranteed damage if someone accidentally plugs the RJ45 power cord into the Ethernet connection. Or, would it depend entirely on how robust the implementation of the NIC card is?

This strange situation is due to this being an engineered system of several different products from different companies.


texts: Reflow oven - resistive heating element or infra-red

texts: I'm looking at making a reflow oven and have just found out the toaster oven I have bought uses a standard conduction heating element rather than infra-red. The knob used for temperature control goes up to 250˚C - so should be high enough for the lead-free solder-paste I have access to. Will using a reflow oven with a standard heating element work? Most of the guides I can find on the 'net talk about infra-red versions.


texts:
I've built a RAM expansion cartridge for my VIC-20 computer.

It uses the CY62256L 32KB SRAM chip.  It has been working fine except there's a quirk.

If I power off the computer, but leave the external disk drive powered, there is a small amount of current (apparently through the drive's reset line into the main Vcc) supplied to the expansion board still.

It is in the micro-watts but it is enough to keep the RAM chip in low-power standby.

Is there a way I can prevent this small amount of current from flowing?

Here is my circuit (please excuse its messiness):

EDIT:
Here's a clarification of what is going on.  Here is a page from the schematic of the computer, which is powered off when the current leak happens.

The external drive is powered externally.  The red circle is where it is sending +5V into the serial port while the computer is turned off, i.e. the reset line.  The blue circle is where the reset line connects to my board.

However, the green circle is where the reset line is usually pulled up by the computer, and here I think is where it is leaking onto the Vcc.  Which enters my expansion board at the purple circle.

It's Vcc that has current which is powering the RAM.  The board's reset line is high too, but it's only connected to a switch.

Does that help explain?


texts:
Need formula to selecting coaxial cable type and GSM antenna

I'm using a GSM modem for my application which is often installed at a basement where there is no GSM signal so I will need to attach it to an external antenna that is placed outside of the building.

Since low loss coaxial cables are very expensive, I'm trying to find a rough formula that will allow me to calculate the maximum loss/attenuation in dB per 100 feet of the coaxial cable that I can use, given my Antenna gain (DBi), cabling distance (in feet) required and GSM signal strength (RSSI ASU) obtained by the modem placed at the antenna location, and the minimum GSM signal strength which I can tolerate after cable loss.

For example, I'm using a 5DBi Antenna which has to be connected to the GSM modem 100 feet away in the building.  If the GSM modem were to be placed at at the antenna, it could achieve a RSSI of 23 ASU which translates to -67dBm. I can tolerate a minimum GSM signal strength of 15 ASU (-83dBm). The formula should allow me to calculate the maximum loss/attenuation in dB per 100 feet of the coaxial cable that I can use.

Grateful for any thoughs.  Thanks.


texts: Foster - Seeley FM Demodulator Explanation

texts:
Consider this Foster Seeley Demodulator

If I have correctly understood, its basic working principle is the fact that at the secondary coils (L2) of the Balun there will be two signals equal and opposite. They are  added to the signal applied to L1 through C8. This means that the 2 diodes will receive:

+V2/2 + V1 and -V2/2 + V1

During the instants in which the RF input's frequency is equal to the carrier, C1 and C2 are sized to realize resonance and so V2 phasor will be orthogonal to V2 phasor. This, in addition to the previous relationship, will mean that the signals applied to the diodes will have the same absolute values. And so? Which is the role of the diodes?

Reference: https://www-elec.inaoep.mx/~rogerio/DemodulationGeneral.pdf, page 13


texts: How to control the output voltage of a solid state relay

texts:
Considering this solid state relay:

The output voltage can be from 24 to 380V. How can I control this voltage? Is it proportional to the input voltage?

What I need is a voltage regulator that can be controlled from a Raspberry Pi in order to control the speed of a fan. Currently, I use something as below that works as expected.

I am completely new in electrical engineering, so please be kind with me...


texts:
I need to find the voltage Vi for Q3 saturated
with B = 100 for transistors.

I did the calculations and then simulated the circuit and i had similar results.
the Question is: the analysis is right ?

My calculations:

If Q3 is in saturation then vce3 = 0.2v
    and with: 20 - 0.2 = 5kIc3
    Ic3 = 0.00396 A, also Ib3 = 39.6 uA

If i suppose Vce1 aprox 0.2v and vcb3 = -0.5v:
   19.8 - 0.2 - 0.5 - 1.98 = 5kIe1

then:

5kIe1 = 17.12V    and  Ie1 = 0.003424 A,  Ib1 = 34.24 uA

but: Vcb1 = 1.712V and Q1 is not in saturation. Because: Vcb(sat) = -0.5v

Using:

5kIe1 + Vce1 = 17.32v , Vcb1 = 500Ie1 , Vce1 = Vcb1 + 0.7

solving:

      5KIe1 + Vcb1 = 16.62
      500Ie1 - Vcb1 = 0

Ie1 = 0.003A, Ib1 = 30 uA, Vce1 = 2.2 v, Vcb1 = 1.5v

For Q2 i can say that Vce2 = 2.68v and Vcb2 = 1.98v  from  50kIb3 + 0.7 = Vce2
 I3(5k) = Vce2/5k = 0.000536 A

With Ib1 + Ic1 = I3 + Ie2 + Ib3
      Ie2 = Ib1 + Ic1 - I3 - Ib3

Ie2 = 2.4544 mA, Ib2 = 24.544 uA

Ending with:

     Vi = 1.98 - 100kIb2,

     Vi = - 0.4744 V

are the calculations right ?.
 I doubt about the ecuations:

        5kIe1 + Vce1 = 17.32V
        Vce1 = Vcb1 + 0.7
        Vcb1 = 500Ie1

Seems right, but i didnt take in consideration the rest of the circuit.

Thanks a lot for your help and time.


texts:
I'm trying to make a 300V H Bridge for an electrostimulator. The circuitry is as posted here, using MOSFET P20NM60GP:

When I tested it with low voltage supply (just for the sake of safe testing), and a 15 Watts 1kOhm resistor I get the output waveform I desire, that is:

However, when I try to change the supply voltage to 300V (galvanically isolated, safety first!), with the same 15Watts, 1kOhm resistor I get this output:

The probe is set to x10, corresponding with the x10 oscilloscope, so those are real 500mV per division. The frequency and waveform are fine, it's just that the voltage output is hyper low- was expecting to get about 300V peak.
Any ideas as to why is this H Bridge misbehaving on High voltage? Thanks in advance!


texts:
I've currently have an Intel Hex file that is 109kb, but with AVR-SIZE and FLIP I see that it's actually only going to take up 37,344kb of space on the chip, unless I'm making a false assumption there.

Issue:

I have an AT89LP51RD2 which has 64k of flash memory used for ISP. I can program a Hex file that windows says is 49KB, and AVR-SIZE says is 19,129kb, and everything works beautifully. When I go to flash the larger (109kb/37kb) file I originally mentioned, FLIP doesn't bark at all yet my chip doesn't get programmed properly? well it at least doesn't boot up like the other, smaller, firmware does.

I feel like I'm missing something with these HEX/bin/data sizes, and maybe someone could clarify where I'm going wrong.

Any help would be amazing! Thank you!


texts:
Is there a company that will sell me a touch panel similar to the IPhone or IPad surface, in single quantities, complete with a Developer Kit?

Can I get it in a specific form-factor (say, 2x7 inches)?


texts:
I used this schematic to build a half bridge power supply, but I have some problems and need some help.
The first problem is feedback.
I think this feedback is not good because with this feedback the transformer produces a noisy sound like "tik-tik-tik"about twice every second and the voltage changes beetwen 40 to 45 in each rail.
I read some where that this feedback doesn't control the duty cycle and it just turns the PWM on or off but I need a feedback that controlx the output voltage by decreasing or increasing the duty cycle.
Without feedback there is no noisy sound and the SMPS works fine. When I connected a 300 watt load the voltage dropped about 20 volts.
Pleasehelp me to change the feedback.
What should I do?

I changed this schematic a little bit.

My primary winding has 19 turns. The secondary is 8*2.
I used an ETD 39 core.
The target output voltage is 45*2.
I changed the frequncy to 80 kHz.


texts: Electric Skateboard Remote Control Schematic

texts:
Picture below is the PCB of Xiaomi Acton Electric Skateboard Remote Control.
Basically it is 2,4 GHz transmitter, transmitting the value of a potensiometer (throttle). Normally when the switch ON, the blue LED will blink.
At sudden the remote controller stop working, the LED not blinking anymore and I found out the 2 IC's circled RED in the picture below is way too hot, probably broken.

I don't know what are those two ICs. The IC on the right (labeled Q1) seems like a voltage regulator but I'm not sure. There is a printed label on top of the IC (Al2RD) -> the Al seems like a logo.
The IC on the left (labeled U3) printed X7DP88.
I couldn't find those texts in online search.

The remote cont. powered by 2xAAA 1.5V batteries yield ~3Volt at the Vbat.

Could you help me find out what are those ICs ?  Or at least what is function (i.e voltage regulator, diode, transistor)

Update
A quick connectivity test with a multimeter, I came to this schematic below :

It seems like Q1 is some kind of regulator. If it is then to what voltage it regulate the 3V battery? I thought the logic level of most MCU is 3.3V. Now what if I use super new 3V battery? Could I just bypassed this regulator, just to verify if it will turned ON.

The U3 seems like an LED controller (make it blink? Is it? ).
Please CMIIW


texts:
I have a Home Automation Motion Detector Project. I am to light a LED strip of 1meter when motion is detected. My arrangement is posted as an attachment. The transistor is attached to a microcontroller output through a resistor and diode.

My Question is: is a LED Driver compulsory in this arrangement?

Another option that can be implemented is Using a Relay. The relay will act as a driver.

Please refer to the attached image and give your valuable advises

Edit: These are the Relay Ratings that I have found in the datasheet. These are the only rating given in the entire datasheet.


texts: Battery Monitoring to detect low power state?

texts:
Our problem is corruption of battery due to reaching zero level of charge. We have tried many methods to monitor the battery as:

How to detect low battery of a lead-acid battery?

(using ADC and micro-controller). Now, we are using (IC - DS2788 E+) however though this type of monitoring circuits consume power. Is there any way to monitor the battery with minimum power overhead (e.g a couple micro-watts) and disconnect the battery?


texts:
I've been having a hard time finding a solution to this problem.

I recently ordered a 5 Volt 2Amp AC to DC switching power supply from adafruit.cc

When I connect my Arduino's analog sensor to the ground of my switch mode power supply my Arduino detects that it's oscillating.

I thought the voltage on the ground pin would always be 0 and not oscillate. The power supply on the Arduino does this properly. Why am I having this issue with the switching power supply and is there any way to to make the circuit have a consistent ground?

EDIT: Links to info
http://arduino.cc/en/Tutorial/AnalogInput
https://www.adafruit.com/products/276

I don't know how useful that analog input info will be I'm more of a programmer.


texts: FMS Standard Dash Display not reported on SAE J1939 data link

texts:
I have a listen-only device plugged into SAE J1939 data link in Volvo FH440 (2014). So far I managed to collect HRLFC, TCO1 and some other, but no Dash Display (PGN 0xFEFC). I collected data in stationary conditions (no vehicle motion, ignite on), so far I had no opportunity to collect them during motion, but judging by the fact that other PGNs are reported normally I would expect this one too.

Is there any special condition under which this PGN (0xFEFC) is reported on the bus?


texts: Is it viable to power a circuit board featuring an SD card using a coin cell battery?

texts:
I'm currently working on an electronics project implementing an SD card. It is also required that this device be portable and small, thus I'm attempting to use a coin cell to power the board.

However, I'm finding out that this is more difficult than I had originally assumed. In my testing, I've been using this Panasonic BSG CR2032. Doing some research, it states that the maximum SD card current is spec'd at 100 mA (which is a lot), however, I am expecting on average that those read/writes only be 30 mA. Furthermore, that will not be a constant 30 mA, but only when doing a read/write.

Now the obvious problem is that even though the coincell is rated at 225 mAh capacity, that's spec'd at the continuous drain current of 0.2 mA. Referring to the data sheet, even if I were to only run continuously at 2 mA, my capacity would drop down to ~175 mAh. The relationship between current draw and capacity does not appear to be linear, thus doing the math at say a continuous current of ~15 mA would be even more drastic than the linear extrapolation...

My tests confirm this that I am only able to interface with an SD card for about 3 minutes before the coin cell does not have enough power to continue communications.

So my question: Is it viable/realistic for me to think I can power a circuit board featuring an SD card using a coin cell? Do they have coin cells rated for higher continuous current drains (in the mA range)? I'm not well versed in the battery types out there, thus I'd appreciate any recommendations!

Also, it is very important that this circuit board be small and compact, thus I'm trying to avoid stepping up to a bigger 'box shaped' battery.


texts: SPI interface, ESP 07 connect to MCP 3008

texts:
I'm trying to connect an MCP3008 to an ESP07 through the SPI interface. (A bidirectional level 5V - 3.3V is used in between but it doesn't matter)

However this is not working because:
The CS pin is the pin 15 of ESP07 which needs to be GND otherwise it doesn't boot.
The MCP3008 CS is on HIGH.

I'm trying to connect several analogue sensors to the ESP. Is there an workaround? What is to be done? Am I missing something?


texts: Any problems with "floating" an oscilloscope?

texts:
I have a Chinese scope with a two-pin power cord and a plastic body, and measure megaohms between its ground terminals and the actual earth, so I believe it has an internal isolation transformer (I suppose I could open it to confirm...)  I've used it to measure small floating voltages before without problems (connecting the ground to +5V relative to earth, and the probe to a current sensing resistor also around +5 V), but now I want to measure power supply voltages where the ground of my scope will be connected to a rectified wave at maybe 200 VAC relative to Earth.  Any problems?  Does an isolation transformer make everything good?

I know that what you're supposed to do is use two separate probes and use the Math function to subtract them, but that doesn't work in practice because the common-mode voltages are so much higher than the differential voltage.

... Oh.  Besides the, um, safety reasons.  The whole scope will then be at 200 VAC relative to Earth ground, so if I touch one of the scope's BNC connectors and a real ground at the same time I'm in trouble.  I guess that's a big problem, but is it the only problem?  Floating the device under test with an isolation transformer would not have this problem?  But that transformer would have to be a lot bigger to handle the high power.  Does it have other problems due to parasitic capacitance, etc.?

Is there any trick to using the differential math function method by reducing the common-mode voltage with a capacitor or large resistor, but not connecting it directly enough to produce a safety hazard?


texts: Required math for setting up a laser diode

texts:
I'm new to electronics and come from a software background.  Recently I got a laser diode that I would like to use with my arduino.  The manufacturer says it is 5mW and draws 2.8-5.2V.

I'd like to learn how to decide which components I need for a project (i.e. their specific ratings).  I know I need a diode and a capacitor for this "circuit."  What maths would I need to do to figure out the rate of the capacitor and the diode as well as any resistors that I would possibly need.

Edit: The manufacturer says === the specs on the web site.  Also as far as the math, I'm asking more so for the functions needed/ algorithms to compute which parts need to be what strength.


texts: Equivalent Series Resistance of 13.56 MHz RFID Antenna

texts:
I am designing a system that uses the MFRC522 by NXP Semiconductors and I am having a bit of difficulty designing the antenna.

NXP provide an antenna design guide under the application note AN1445 although I am stuck on Page 8 as I cannot find any formulas for calculating the equivalent series resistance (Ra) of the antenna. I am wanting to use a rectangular microstrip antenna and found the equivalent series inductance (La) using eDesignSuite by STM (see image below).

The application note provides details on matching network and matching requirement (50-Ohm) but in order to calculate this, the value of Ra must be known.

I am aware that there are plenty of hobbyist modules available called 'RC522' or similar but my space requirements something a little more compact which is why I would like to design the antenna myself.

Any advice would be greatly appreciated. I am not a specialist in RF and microwave engineering so I apologise in advance if this question lacks clarity.


texts: What is the purpose of R6 and R7 in Grove sound sensor?

texts:
Looking for how this sound sensor works, I found this: "This sound sensor is used to detect whether there’s sound surround or not, please don’t use the module to collect sound signal. For example, you can use it to make a sound control lamp, but not as a recording device."

Here are my opinion and doubts. Can anyone clarify this for me?

C3 is used to filter VCC from the non inverting input of U1B and allow only the voltage changes of MIC1
Since all this voltage difference will go to R6, why R7 is needed?
Why put 2 series op amp which have the same specs?
Why C2 is needed?
Why it cannot capture frequency sound but it can capture intensity?


texts: Which electrical characteristics of stator and rotor windings influence the mechanical power of a single phase induction motor?

texts: I wish to find the values of resistance, inductance and mutual inductance of stator and rotor windings of a single phase, two poles, capacitor-start, capacitor-run induction motor with 1/2 Hp mechanical output power. The mains voltage is 230 V with frequency 50 Hz. The slip is 2.78%. I have successfully done this using genetic algorithms achieving high efficiency and balanced operation of the two stator windings at operation at nominal rpm. Nethertheless I would like to know the most salient features that determine the output power from a physical-electrical engineering point of view.


texts: Understanding branch delay slot and branch prediction prefetch in instruction pipelining

texts:
Let me define:

Branch delay slot: Typically assemblers reorder instructions to move some instructions immediately after branch instruction, such that the moved instruction will always be executed, regardless whether branch is taken or not, without leaving the system in inconsistent state.
Branch prediction prefetch: predicting what will be the outcome of branching condition and then prefetching instructions from the resultant location, so that they will be immediately executed after branch instruction.

Now, lets consider below execution sequence (below, F: instruction Fetch, D: instruction Decode, X: eXecute, M: Memory access, W: Write back):

BRANCH   F   D   X   M   W
INSTR1       F   D   X   M   W
INSTR2           F   D   X   M   W
INSTR3               F   D   X   M   W

Usually branch condition is evaluated and executed in X stage. By this stage, INSTR1 and INSTR2 are already started and these are the instructions which can be affected by out choice of whether to use branch delay slots or branch prediction prefetch or both. I did not find any text to discuss this clearly. SO I tried to guess it as below:

  When we use both, then instruction sequence would be:

BRANCH: branch-instruction
INSTR1: branch-delay-slot
INSTR2: branch-prediction-prefetch

  When we use only branch prediction, then instruction sequence would be:

BRANCH: branch-instruction
INSTR1: branch-prediction-prefetch-1
INSTR2: branch-prediction-prefetch-2

  When we use only branch delay slots, then instruction sequence would be:

BRANCH: branch-instruction
INSTR1: branch-delay-slot-1
INSTR2: branch-delay-slot-2

Am I correct with this? Is it how this happen actually for different cases? Or there are some more details?


texts:
I have a noise output of 35nv / (sqroot (hz))
So in dbm this is just 20*log(35nv) = -149.1 dbm/hz ?
Is that correct ?


texts: Full bridge driver capacitor ringing problem

texts:
This is my first time designing a full bridge driver. I am experiencing problems with ringing on the output. I have made a pcb for it. This is a picture of the top side of the board.

Backside

Input to L6498 Drivers, 250ns dead time

Unloaded output voltage of the full bridge

Output with unloaded transformer attached
CH1: Transformer Voltage CH2: Transformer current

Full setup

The problem I have is with the oscillation at the top of the output waveform when a load is attached. Applying a load to the transformer only makes ringing worse. I have tested the gates of all the mosfets and the waveforms are very clean with no spikes even when the transformer is loaded. The only problem is with the bridge output waveform. The board has a 1uf film capacitor in the center of the board. I have tried adding a 2200uf capacitor right at the main voltage rail next to the mosfet as shown in the image below. I also have a current transformer to measure the capacitor current.

The output waveform improves with transformer still connected when electrolytic cap is added. CH1 : Full bridge output voltage CH2: Electrolytic capacitor current.

The problem with this is: the electrolytic cap gets warm under very light loading of the full bridge. At high loads the current through the capacitor was about 30 amps at the peak. The capacitor was very hot. If adding more capacitance to the supply rail would improve the ringing, what kind of capacitor should I use? Would a larger film capacitor help the ringing? Is the ringing a layout problem? If so, should the pcb power traces be shorter?


texts: Difference between single and dual rail op-amp

texts: I don't understand why some op-amps are specified as being dual rail, and others as single rail. Since (AFAIK) none have a ground pin, there is no difference between connecting the positive supply to +10v / the negative supply to -10v, or the positive supply to +20v and the negative supply to ground. Either way, the difference is 20v!


texts: In a multiplexer, can you direct the input into all the outputs at the same time?

texts:
I need to direct a single line into multiple outputs, so I'm using a MUX to direct the input into the desired outputs (one at a time). However if i ever wanted to do a broadcast to all my output lines at the same time, is there any MUX which allows it ? Can I connect the input to ALL the outputs directly?
Thanks in advance


texts:
I am an undergrad electronics student , so I have some knowledge about why certain resistors and caps are used with processors but still aloof to majority of them . When one takes look at a raspberry pi board you see a range of resistors and caps , is there any online documentation from Broadcom that instructs these resistor and caps to be placed ? If not how would one go about testing a processor ? I'm currently building an FMCW radar system and I need to develop a board containing Broadcom processor .Time isn't an issue , i'm prepared to devote my complete resources if given a hint or direction to proceed .

Thanking you


texts: Sound level meter using a microphone with ADC

texts:
I'm working with STM32F4, MAX4466 amplifier and a condenser microphone. In other words, Adafruit 1063. I want to get the sound level in dB unit. I know:

Microphone sensitivity: 0.0063096 V/Pa
Amplifier gain: 41dB
Amplifier voltage bias: Vcc/2

STM32F4 ADC resolution is setted to 12 bit, so the max value is 4095. Vcc = 3.3V.
To reach the goal, I collect 800 samples (with a sample frequency equals to 8kHz) and make the RMS in this way:
\$V_{RMS} = \sqrt{\frac{1}{N}\sum_{i=1}^{N} \left(\frac{x_i}{4096}  V_{cc}  - V_{bias}\right)^2}\$
where \$x_i\$ is the ADC input value. Now, to find the sound level, I'm using the following equation
\$L_{p} = 20\;\log_{10}\left(\frac{p}{p_0}\right) - gain\$
where \$p = \frac{V_{RMS}}{S}\$, \$S\$ is the microphone sensitivity, \$p_0\$ is the sound reference pressure (0,00002 Pa) and gain is the amplifier gain (41dB).
Here is my problem. The value I get, seems to be different from the sound level measured with other tools for at least 20dB. Unfortunately, it is not only a shift, because this value changes when the sound level changes.
Exploiting the properties of logarithms, is possibile to write \$L_p \$ in a different way.
\$L_{p} = 20\;\log_{10}\left(V_{RMS}\right) - S_{dB} - p_{0_{dB}} - gain \$
where \$S_{dB}\$ microphone sensitivity in dB (-44 dB) and \$p_{0_{dB}}\$ is the sound reference pressure in dB unit (-94 dB).
Both equations return the same wrong result.
Now, if I try to multiply the log function by 30 instead of 20 in the second form, the final value is correct and very accurate. In order to understand more, I tried to use another microphone with a different sensitivity, and another amplifier (MAX9814) with differerent gain. Same result. My question is, why? Maybe something is wrong somewhere else?
Edit
Here's my code:
#define AMPLIFIER_GAIN          41.727F // dB
#define MICROPHONE_SENSITIVITY  -44.0F  // dB
#define AMP_BIAS                1.65F   // Volts

#define SM_ADC_MAX_VALUE                4096.0F
#define SM_VOLTAGE_REFERENCE            3.3F         // V
#define SM_REFERENCE_SOUND_PRESSURE     -93.979F // dB

float SM_Get_Sound_Level(sound_meter_t* sound_meter, float *input, size_t n)
{
    float amp_out_rms = 0.0;
    for (size_t i = 0; i<n; i++)
    {
        float amp_out = ((input[i]/sound_meter->adc_max_value)*sound_meter->voltage_reference - sound_meter->amp_bias);
        // Calculate the average for RMS
        amp_out_rms += (amp_out * amp_out);
    }
    // Get the RMS value
    amp_out_rms = sqrtf(amp_out_rms/((float)n));

    // Avoid to compute log(0)
    if (amp_out_rms != 0.0F)
    {
        return 30.0F * log10f(amp_out_rms) - sound_meter->microphone_sensitivity - sound_meter->p0 - sound_meter->amp_gain;
    }
    else {
        return 0.01F;
    }
}

void SM_Init(sound_meter_t *sound_meter, float microphone_sensitivity, float amp_gain, float amp_bias)
{
    sound_meter->microphone_sensitivity = microphone_sensitivity;
    sound_meter->amp_gain = amp_gain;
    sound_meter->amp_bias = amp_bias;
    sound_meter->adc_max_value = SM_ADC_MAX_VALUE;
    sound_meter->voltage_reference = SM_VOLTAGE_REFERENCE;
    sound_meter->p0 = SM_REFERENCE_SOUND_PRESSURE;
}

...

SM_Init(&sound_meter, MICROPHONE_SENSITIVITY, AMPLIFIER_GAIN, AMP_BIAS);

Microphone capsule specifications
Microphone amplifier circuit
MAX4466 datasheet


texts:
I really hope I'm posting this in the right section.

I was strolling down the street and looked up at this massive barrel object mounted to a utility pole.  It's hard to tell from the pic, but it definitely has the brand Siemens stuck to its side.  Being Siemens, I figured the electrical engineering section deemed worthy.  Everything else was illegible due to its height above the sidewalk.  There's what looks like a huge RF antenna poking out of the bottom of it.

I'm hoping that someone who does line work or know RF or something might know what this is?


texts: How To Run Shaving Machine Without Bettary?

texts:
I'm just an amateur in this and I Need Help..

I've drawn this circuit of my Shaving machine
and I want to remove the battery and connect it directly to one of these phone chargers-:

The first: output 5.7v ~ 800mA

or

The second-: output 5v ~ 350mA

or

-The shaving machine charger: 3v ~ 200mA

Will Any Of These Work?


texts: Will beeping dc motors cause damage to the motors?

texts:
I have noticed from a drone (of a friend of mine) it has a feature that lets its motors beep so when it gets lost it can be easily found. I have some searching and this seems to be done by alternating turning forward and backward quickly enough for the motors not be able to spin.

I would hopefully like to exploit this characteristic as maybe a feedback to the user for example a button is pressed and the motors would beep, this would mean that I do not need a piezo speaker.

But will this cause some damage to the motor or motor driver? My intuition is telling me it does, but on some commercial products (drones) or high performance robots (the one used in competitions) I often hear these beeps.


texts:
I would like to know what happens if an Interrupt is enabled(ex:Arbitration Lost Interrupt in CAN module of NXP's LPC1778),but no ISR has been defined for the interrupt.

When such an interrupt occurs,i know that the respective interrupt flag will get set, but since i haven't defined any ISR,there wont be any interrupt vector offset address stored for control transfer for such an interrupt and so the control will pass back to the main routine,and i can reset the interrupt flag by polling it in the main routine (this is what im thinking).Will there be any latency when the CPU is figuring out that there's no ISR to jump to?

Any solutions on what might happen can really help me.

Thanks.

  Update:

I enabled CAN Interrupt on my uC,but didnt define an ISR. When I performed an  internal loopback test,the code entered into an infinite loop.
Here is the disassembly code of the infinite loop being executed on LPC1778:

B       .
ENDP

So ya, if you are using interrupts, use the ISR.


texts: how can i make drone fly in same location? (not go left, right, forward, back)

texts:
I made quad drone that use PID control to fly and drone fly well.
I set the PID values, and the drone always have difference force, so drone always go left or right or forward or back. It can't fly in the same location.

I would like to make the drone fly in the same location. However, I don't know how to make it. Maybe this is hovering. But i don't know any hint about it.
please let me know how to fly drone in same location!


texts: Help with constant current load for discharging Li-Ion

texts:
I'm trying to test the capacity of some 18650 Li-Ion batteries by discharging them to 3 volts with a constant current load. For the load I'm using an LM317 as such:

-Battery +ve to the input pin
-3 ohm resistor between output and adjust (should limit current to 400mA)
-1 ohm load resistor between the adjust pin and battery -ve.

Short circuit current without the 1 ohm load resistor is 320mA, measured in series with the load resistor is 270mA and measured in parallel with the load resistor is 240mA. I'm very confused, I was under the impression that constant current meant constant current. Am I missing something obvious? I know an LM317 isn't the best option for CC, but it's the simplest option I had on hand.

simulate this circuit – Schematic created using CircuitLab


texts: Xbee sends data periodically to coordinator,what will be the interfacing circuit with avr atmega168?

texts:
I want an xbee to do nothing but simply send some data already programmed in the microcontroller (Atmega 168).But what I cannot figure out is how to connect the microcontroller with xbee on a breadboard.will only GND and Vcc be enough?
The mc is programmed externally beforehand by ISP.
Should I connect its pin out to Txd of Xbee module?
Any help will be greatly  appreciated.


texts: Reading a number of voltage samples with Fluke 8845A

texts:
This question is for anyone familiar with Fluke's 884XA-series meters. I am looking to measure voltages with the Fluke 8845A meter. What I would like to do is measure a specified number of samples at a given rate. Here is what I am looking to do:

Measure 500 voltage samples.
Measure each sample at a 1ms interval.

I remember that last time I played around with the 8845A I specified the number of samples but could not get the meter to stop taking readings. So my questions are:

What is the appropriate SCPI command to specify 500 samples.
What is the appropriate SCPI command to measure at 1ms intervals?


texts:
Please suggest any ways to improve punch or bass of the sound for the following audio amplifier using TDA2030A. The sound output of the amplifier lacks some bass. Can I use TDA2050 to improve sound quality?
I am driving a 5W 8ohms speaker.
Note: This is not a subwoofer circuit, it's a normal speaker.
I will be happy to know about some errors and improvements for the circuit.

This is a picture of my speaker


texts: How do the load and the second stage amplifier affect output/input impedances of a bjt multistage amplifier

texts: It is easy to show that the Output and input impedance are in a mathematical relation, but it is not clear to me how that is possible. How is the load positioned at one end of the amplifier able to affect the input impedance which is on the other end of the circuit?


texts: What is the weakness of using Hi-Com TRIAC to drive motor compressor in refrigerator?

texts:
Does using Hi-Com TRIAC to drive motor compressor have a weakness?

Why do most (all) refrigerator manufacture use a relay instead of HI-COMM TRIAC to drive the compressor?

Isn't a [Hi-Com TRIAC more reliable than a relay?

NOTE: The motor compressor is induction motor.


texts: 8-bit shift register Master Reset button not working

texts:
I'm using the 74HC595. The datasheet can be found here.

Everything works, just the only problem is the Master Reset button is not working. Pressing it to LOW doesn't do anything. I measured the voltage while HIGH and LOW. Which is MRh = 4.69V, MRl = 0.04V.

Looking at the datasheet. With Vcc at 4.5V (I'm using 4.98V). The HIGH level input voltage is 3.15vMIN. The LOW level input voltage using 4.5Vcc is 1.35vMAX. Here's the schematic I drew. And the breadboard, although not really helpful. Is it the pull up/down resistor values?

What could be the problem?


texts: Why do diodes adjust to reverse breakdown voltage when we apply a voltage more than the breakdown voltage?

texts:
When a voltage(neglecting sign as I am considering reverse bias region) more than the reverse breakdown is applied then why diodes adjust themselves to reverse breakdown voltage? Please provide an intuitive answer. What is happening physically?
What happens to the remaining voltage applied?


texts:
I'd like to measure queuing time, similar to what they're doing in Finland. Instead of detecting bluetooth (which is disabled in most phones) I thought of detecting EDGE/3G.

I'd like to log the following information:

Phone 1 entered the zone at 14:00 and left at 14:30
Phone 2 entered the zone at 19:05 and left at 19:30

etc.

How do I uniquely identify EDGE/3G/etc phones that enter a zone?
Is there a better/easier way to uniquely identify phones entering/exiting a physical location in a manner that allows them to remain anonymous?

By "uniquely identify" I mean I want to be able to differentiate between the same phone entering the zone multiple times versus different phones entering.

By "anonymously" I mean I don't want to record any information that would allow anyone to track down the phone's owner.

I have no intent, expertise or need to snoop on phone conversations. I just want to identify phones as they pass by.


texts:
I want to create a LISN module in LTSpice. For this I tried to make a subcircuit by first adding the RLC components and saving it as lisn.asy. Then I copied the netlist onto notepad and added :-
.subckt LISN1 line eut lisn gnd
I saved this in the same directory as the lisn.asy and tried to run the simulation of the circuit (shown in figure). I get the error

I thought this was because I had not added the ".lib" line in my subckt definition. I want to add it under [Misc] as a separate component. How do I do this?
This is my netlist:-

EDIT 1:
I followed this link and this approach too, but still got errors. I worked around this problem by simply adding the whole LISN circuit itself in my schematic instead of adding a subcircuit (but I want to know what's wrong anyways).


texts: What does this switch symbol with a triangle on the contact stand for?

texts:
I found this symbol in one of my control circuits.  It is a part of a suction valve operated by a motor overload relay.
I have been pulling my hair out trying to find the meaning of this symbol and searched for this on Google and every possible forum, but with no luck. I am absolutely certain that this must be some silly symbol which I am unaware of and  perhaps be well known.


texts: Problem in AC fan speed control(using ZCD and Atmega8A) when running on Inverter

texts:
I recently built an AC fan speed control circuit using Atmega8a,Triac,2 nos Optocoupler and ZCD method.I am attaching the necessary circuit regarding the triac firing and ZCD.The Atmega is configured to drive the MOC3021 on falling edge detection.Please take a look.The fan speed is controlled in 5 different steps(namely-0,1,2,3,4).In 0,the micro is switching off the MOC3021 completely so the output is 0.Also in '4',the output of the micro is continuously giving '1',so that the MOC3021 stays on and the fan rotates in full speed.The speed control is done in 1,2 & 3.The speed control works perfectly on pure sine wave AC.But whenever electricity goes off and Inverter power takes place,the speed control malfunctions(Either the fan stops or it generates great hum and rotates very slowly or sometimes it work for a short duration and after then the fan stops).I saw with a DSO that the inverter is giving nearly square wave output.My question is,is this normal for the circuit to malfunction in square wave(zero cross is happening in square wave also so why is it malfunctioning??)or I am missing something??There is also external snubber attached using 39R and .01uF.

One more point i would like to add that the circuit works while on Inverter power only after Midnight or later for some random duration.How is this even possible???

Any type of help is appreciated.


texts: Computer Science + Electrical Engineering Project, Angle Projection

texts: I'm looking for some help in a project of my own that i can't get off the ground. I wanted to make some mechanism that can automatically shift to a certain angle based on computer input. Ex. On a computer i enter 48 degrees, the mechanism (which is no bigger than a normal protractor) starts off flat at 180 degrees then shifts to 48 degrees after input. What programming software helps with this, how do i build this. If it helps i am a CS Major


texts: Why do semiconductor companies not provide their datasheets publicly?

texts:
Some semiconductor companies such as Broadcom and Microsemi do not publish the datasheets of some of their chips such as networking ones. It seems the companies do not provide the datasheets without an NDA. On the other hand, as far as I know the prerequisite for an NDA is an order for buying a high volume of chips (is it ture??)

So my questions are:

1- While some of the chips can be bought from electronic distributors, why do the companies not provide the datasheets?! What is the reason behind not publicly publishing the datasheets?

2- If I need a low volume of the chips, what should I do to access the datasheets?


texts: USB Send Simple Output or Allow Current Flow?

texts: I need to write a program that will turn on an external power supply by allowing current to flow through. This should be controlled via USB and should let current flow between the PSU pins. I know I could do this with an Arduino, but I'm looking for a simpler and cheaper solution. Is there a cheap USB device for allowing current flow (or outputting power to a transistor that will allow the current flow) that I can program to send an output?


texts:
It's been quite a while since I heard about amateur (ham) radio. I think it's a good hobby to dabble into to develop an understanding of communication technology and electronics. But whatever research I have done to date turns up things that describe it for someone who buys ready made radios. I want to dive into the electronics and understand how all of it works, I don't want to think too abstractly.

Can anyone please guide me to some website or book which can guide a beginner to get started in radio technology but also provide at least a basic understanding of how everything works and how to get your hands dirty? I know I have to get a licence and I am preparing for the exam.


texts:
I need to amplify an electret microphone for use with an Arduino Uno. I have a few capacitors and resistors and several transistors one of which is an N-channel.
Any ideas?
Can you please also provide me with a scheme?


texts:
I am doing my project. and it's about a DC-DC converter.
I am using HCPL 3021 as a driver for the MOSFET IPPR045C7.
in open loop cicuit, I am using Vin=60V, with duty cycly = 60% of PWM signal (F=20KHz).
The output voltage should be Vout=36V. But it's not. I got Vout=16V.
even with a load connected the voltage remains wrong.
the circuit is shown in the joined picture.
Can you please help me and tell me what's wrong with circuit?
Is the ground connection wrong?


texts: Different battery capacities in series is poor

texts: How is the scientific (electrochemistry, physics, electrical, etc) explanation on different battery capacities in series is bad or poor and will damage them ?


texts: Accessing RAM instance from multiple modules in Verilog

texts:
I am trying to make a single instance of RAM  module accessible in different modules without instantiating it in every module.
Since If I instantiate RAM module in each module,  there are two more copies of it, taking up twice or more as much Block RAM as needed.
There is no concern about modules trying to access it in the same time, as they run one after the other.
How can I do it?

P.S. providing memory as input to each module seems like incorrect solution..


texts: sn754410ne driving one motor faster than another

texts: I have a sn754410ne IC (quad half h-bridge). I noticed that whenever driving two motors, one motor is driven faster than the other (with both DC power and a PWM signal from my Arduino UNO). I measured the voltage across each motor and noticed there was a discrepancy of .015V. What can I do to drive the motors at the same speed, aside from sending a smaller PWM signal to the faster motor?


texts: What is difference between resonant and non resonant antennas?

texts: I don't know if it's right place to ask it, but I searched google and books the answer I get seems to be like resonant antenna have small bandwidth and have standing wave instead non resonant antennas have wider bandwidth and travelling waves. What I don't get that how should it affect my choice of choosing one over other for a particular situation, like what I lose when I choose one over other and what I gain.


texts:
Preface: Def a beginner at EEing.

I'm building out a proof of concept where I'm using transistors to create a logical AND gate to control LEDs. I'm using reed switches to trigger the transistors and putting the transistors' collectors/emitters in series so that both transistors have to be triggered for the final LED to light up.

Here's the schematic that made to work out the logic:

And here's the wired up bread board:

And this works ... mostly.

When I trigger the first reed switch it lights up the first yellow LED only. Good.

When I trigger both reed switches the two yellow LEDs come on AND the red LED comes on. Good!

But here's where the bad comes in: if I activate only the second reed switch, the one that leads directly to the red LED there's enough current passing through to faintly light up the red LED. Bad :'(

I'm not sure how to stop the current from the second transistor to the final LED. I'm assuming that it's the current from the gate pin on the second transistor passing through to the red LED, but I'm not sure how to stop it.

I tried adding a pull down resistor on the red LED's anode leg and that does help, but of course the red LED dims since the current has a different option to flow in.

Is there a way to keep the red LED off until both transistors are triggered?

I def want this to work, but I also want to understand why it's happening.

UPDATE

Here's the updated schematic and working circuit based on the replies I got here. Thanks again everyone for the help. It's very cool to see it working and to get it!

https://vimeo.com/394545735


texts:
I am working on a project where I am going to need long distance communication and I am unsure the best way to go about it. I am mainly trying to decide between fiber optic or Ethernet and decide some of the pros and cons of each.

I would be working on a distance of somewhere between 100m-300m. I'm looking to transmit relatively simple controls signals to a remote test setup and have it respond with live data and video from multiple cameras and sensor sources. The control setup and test setup would be custom built by myself so I am free to pick any communication protocol/setup I desire. Oh and the system will be outside so durability is somewhat of a factor.

Does anyone have recommendations for long distance communication? I'm leaning towards fiber because I was under the impression that Ethernet connections begin to breakdown over 100m but I have seen a few posts here that point otherwise. I'm also a bit new to communication protocols and connections so any direction or advice on what is wise to use for long distance connections would be helpful.


texts:
Trying out the LTspice simulator, to test a super capacitor charging circuit. With no load, its showing that its drawing 5A. Surely this cannot be correct?

Not there yet. Using the stock standard LTspice model for the LTC3625, with only one modification, changing the .ic V(out)=4.4  to .ic V(out)=0.0, to show how long it takes to charge the capacitors and reach the correct output, NOW it only reaches a max of VOUT 2.5V. Why?


texts: Reducing cost by eliminating microvias when designing a PCB with buried vias

texts:
I'm designing a 4-layer PCB for a very small adapter from a BGA on one side to several discrete SMT connectors on the other.  Due to space constraints, I cannot use through holes for some of the interior connections; they must be routed through blind vias.

After some discussion with the PCB fab company I'm starting to understand a bit better why blind and buried vias cost so much money and how these complicated boards are constructed.  I also appreciate that microvias add cost to the board.  Is there any way to route a signal from one side of the board to the other without at least one set of microvias?

My current design has three via styles:

                 Layer 1-2
----------+  +------+  +--------------------
          |  |      |  |
----------|  |------+  +------+  +----------
          |  |                |  |
----------|  |----------------|  |----------
          |  |                |  |
----------+  +----------------+  +----------
        Through            Layer 2-4

So the trouble comes with having both blind vias terminating on the same layer from either side of the board.  They can't drill those separately before the layers are laminated together, and so the top one must be bored out afterwards and filled in (at high precision and cost, as I understand it).  But I need these signals the whole way through the board! Are there any tricks to working around this?  Or are my design specs simply too challenging for my modest budget?


texts: Why does rotor of synchoronous generator accelerate during faults?

texts:
I don't understand the electrical torque in a generator.  Isn't the counter torque related to the armature current in the generator?
Why does electrical torque decrease during fault in lines that connects the generator to infinite grid?

Fault means more current in armature winding and more current should mean more counter torque.

Why would the rotor accelerate?


texts:
Stumbled upon this in ZVN4525E6 datasheet:

Zero Gate Voltage Drain Current (IDSS): 35 νA @ VDS = 250V, VGS = 0V

The letter is U+03BD and it is not in any common unit prefixes that I know.

My guess this is either substitute for "nano" (since capital Nu is "N"), or some weird expression of current via power (as in V*A). Both make little sense to me.

Also, while I am here asking anyway, is this FET a good choice for low side switching of small loads in 24V system controlled by 3.3V logic but also compatible with 24V pull-ups? This was actually the only choice left in parametric search after I selected 30V VDS&VGS and 3V threshold.


texts: What is a product ID in USB and do I need to buy it for my project?

texts:
I am trying to develop a portable device that will allow me to transfer data from one USB  storage device to another without a using PC/Laptop.
I was reading the developers guide by Jan Axelson where I came across a section that said that one must buy a USB vendor ID/product ID  in order to make any USB device. I read the same on the USB Implementers Forum.
I am unsure of the importance of this product ID in my project.

Is it something like a MAC address for computers/laptops and will I
need it?
Is it something required only for developing peripheral devices and
not devices like what I wish to implement(which I guess is more like
a host)?


texts: Why are there no FPGAs with built in USB interfaces?

texts:
There is no shortage of micro-controllers with built in USB interfaces, but there do not appear to be FPGAs with built in USB interfaces.

Are there technical reasons for this, or is it just that the companies don't perceive a profitable market for USB FPGAs?

Personally, I can think of many of projects for which a low cost USB FPGA would be quite useful.


texts:
I got a Ni-Cd battery (8 AA) 9.6 V, 700mAh. After a 2 hours charge by an AC/DC adaptor (9.6 V, 250 mA) I take the following measurements by the multimeter:

Voltage: 11.28 V (DC)

Current: almost 10 A (DC)

Is this possible?


texts: Why are ratios relevant, but not the increments when defining center frequency of a band-pass filter?

texts:
First of all, here is my directly related previous question:
Why is center frequency of a bandpass filter is given by the geometric average of the two cutoff frequencies?

Olin Lathrop explained very well why the geometrical mean is taken when calcuating the center frequancy. Because ratios matter when defining the center frequency not the linear distance.

But now what I'm wondering the idea behind defining this center frequency by considering ratios. Why was that defined like that? Is that something to do with half power point? What is the benefit? Anyway to illustratively  or mathematically explain the idea behind?


texts: Driving lamps with the fewest number of NPN switch transistors

texts:
I'm building a small system to drive some Nixie lamps and I'm missing some of the classic ICs that could make this design significant simpler. I ended up with some discrete NPNs to select the lamp and another line to select the digit.
Is there some other, significantly simpler, way to arrange these transistors to make a better use of them and achive the same? i.e. one 5V open drain for lamp and one 5V open drain for the digit.


texts:
https://www.zoro.com/schneider-electric-iec-magnetic-contactor-24v-coil-9a-lc1d093bl/i/G0569497/

Hello guys, I'm very new to relays and practically know nothing about what to look for and how to select one. I'm trying to insert a three phase relay between the inverter output and the electric machine. The voltage during the "blocking mode" will have the inverter switching frequency component.

For a common relay like this, does it matter if the "conducting" voltage and current have a frequency of a few kHz?

In the relay product page I attached above, it only says the coil volt is 24 V. Do relays also have a "breakdown voltage" or "blocking voltage" like IGBT or MOSFET?

Also, what about solid state relays?

Thanks a lot!


texts: Icarus verilog syntax error in a generate block

texts:
In the top level of a module, I have the following block:

   genvar i;
   generate
      for (i = 0; i < DEPTH; i++) begin
       fifo_element #(WIDTH) element (.clk(clk),
                       .d_in(e_qd[i]),
                       .d_in_strobe(e_in_strobe[i]),
                       .q(e_qd[i+1]),
                       .q_ready(e_qready[i]),
                       .in_strobe_chain(e_in_strobe[i+1]),
                       .q_out_strobe(e_out_strobe[i+1]),
                       .out_strobe_chain(e_out_strobe[i]),
                       .prev_used(i == 0 ? 1'b0 : e_used [i-1]),
                       .next_used(i == DEPTH-1 ? 1'b1 : e_used [i+1]),
                       .used(e_used[i]));
    end // for (i = 0; i < DEPTH; i++)
   endgenerate

When I attempt to compile this with icarus verilog (v10.1, using the -g2009 command line option) I get the following errors:

fifo.v:84: syntax error
fifo.v:96: error: invalid module item.
fifo.v:97: syntax error

These errors correspond to the line containing for, the last line of the element instantiation, and the line containing the end that corresponds to the begin of the for block.  If I delete the apparently-unnecessary begin and end markers the third error goes away but the other two remain.

What's wrong with my code?  Or is this a problem with Icarus Verilog?  (A little research suggests that while earlier versions didn't support generate blocks at all, they've been supported for some time now, so what I'm trying to do here should work)


texts:
In Eagle board editor, how to remove origin mark?

Once set, I can move it, but can't remove it.


texts: Single motor driving multiple targets - possible?

texts: I'm a veteran programmer new to the electro/mechanical world and unfamiliar with the terminology and what's already available. I have a single motor that I would like to use to drive a carousel or an elevator (these are very small models measured in inches). I would like to be able to switch between operating either of them so that only one of them is being driven at any time. I have been searching online for the terms "single motor" and "multiple transmission/gears" and other similar terms with no success. Now I have an idea on how to make this happen via swapping gears but I'm pretty sure this must be common so I'm wondering if someone could point me in the right direction; I would hate to reinvent the wheel.


texts: Wien Bridge Oscillator using OpAmp(LM386) works in simulation, but doesn't work in Breadboard?

texts:
This is a simulation of the circuit in multisim. It is a Wien bridge oscillator circuit, tuned at 1844Hz. I am mostly interested in generating sound of that frequency. It seems to work here in simulation but when I connect a speaker to the output, I dont get anything. Connected a LED as well, im getting nothing.

I am not sure where the problem is. Is the supply voltage of  +/- 6V a reason? I am using a 12V power supply, split in half through virtual ground technique.
Any idea on where the problem might be? How can I fix it to make some 1844hz sound with a speaker?


texts: Does anybody know the magic command to set baud rate, parity, flow control, etc. for an RS-232 port on the MacOS X CLI?


texts:
We have two STM32F4Discovery boards with Micro USB's for serial communication.
Is it possible to connect two boards to allow communication between them?

Is there is any different hardware other than the cable that would be required?


texts: Why can stability Factor be defined like this ? What does "stability" mean here? let voltage be stable? or let some of current be stable?

texts:
i saw some information about stability from here : https://www.youtube.com/watch?v=jw_GUiswndw&t=422s ,but i have some problems,why can stability Factor ,\$S\$, be defined like this ?
\$S=\frac{\Delta I_C}{\Delta I_{CO}}\$,
\$\Delta I_C\$ is the collector current changes,
\$\Delta I_{CO}\$ is the reverse saturation current changes
I mean,why is \$\frac{\Delta I_C}{\Delta I_{CO}}\$ has relation with "stability" ?why won't someone define \$S=\frac{\Delta I_{CO}}{\Delta I_C}\$, or \$ S= { V_{out} - V_{in} }\$ ,what does the stability mean in here?


texts: MOSFET channel length modulation - Glossing over physics

texts:
I am having trouble understanding an aspect of the channel length modulation/pinch off of MOSFETs.

My current understanding (For NMOS) is that when a positive voltage is applied to the gate, the P-doped regions majority carriers, holes, are repelled from the gate (Electrons are attracted to the opposite charge and fill the holes), leaving negative ions in a channel for the current to flow across. No PN junction, no problem. Current flows fine.

So when my professor tells us that if we increase the drain voltage, the channel will narrow and eventually pinch off at one end, I think it makes perfect sense. Of course! The increased voltage will move the center of attraction closer to the drain, causing the electrons to be attracted towards the drain and away from the source, so the channel will be narrower at the source and eventually pinch off when the drain has pulled all of the electrons that should have gone near the source closer to the drain.

However, to the professor, it works the opposite way. The channel pinches off near the drain. I can't conceive why adding positive voltage would cause electrons to be less attracted to you. I have asked classmates and the professor and nobody seems to have any idea. Classmates say it doesn't matter, the professor says that what matters is the difference in voltage, not the actual voltage. I found This Youtube Video where at 3:00 he says that the "Positivity" between 0.2V and 0.5V is 0.3V. What on earth is positivity? Why take the difference instead of the sum?


texts: What do I need to trickle charge rechargable batteries with a solar panel

texts:
Hi I have a chicken coop door opener that is battery operated. The batteries tend to run down every other month even though the thing is basically just a digital alarm clock with a stepper motor attached.

Anyway I have some Ni-MH batteries and a 12V car solar panel that would be good to recycle into a solution for powering this door opener.

In full sun the panel seems to put out 22v in shade its about 14v.

The clock is on 24hrs a day. So ideally the batteries would recharge fully during the day while supplying power to the clock and have enough juice in them to get through the night.

I'm really quite a novice when it comes to all this so I was hoping someone could point me to a circuit to charge these batteries with a solar panel or some other advice would be welcome.

I'm pretty sure the charger is this one (I've had the thing for over a decade so can't be too sure, no other markings on it) http://www.jaycar.com.au/Ecotech/Solar-Power/Battery-Chargers/Smart-Solar-Battery-Charger/p/MB3501

The batteries are setup to provide 6 volts (roughly) to the chook door clock.

EDIT

I've added a few more images showing the input values and output values.


texts: exponential term in RLC sinusoidal analysis

texts:
I was learning to work with RLC circuits with sinusoidal excitations and the book I was dealing with showed me that the responses of these passive elements to sinusoidal excitation were themselves purely sinusoidal and hence phasor digarams were the best way to deal with these elements, but then I tried solving a simple series RLC circuit using laplace/complex frequency analysis and I landed myself a sine term, a cosine term and a real exponential term. I don't know what or why I am getting that real exponential term, I tried to do it over and over and I got the same results. I am pretty sure my calculations are correct but the book mentions nothing about the exponential term. Kindly pitch in...

This is the circuit I was talking about

simulate this circuit – Schematic created using CircuitLab

Here is an image for a KVL and laplace transformation

Here is an image for the inverse after separation. I dont think there is a mistake


texts:
I'm trying to simulate a TDR based on the figure below, and one of the scenarios is a short circuit. The simulation should last for 140ns.

The parameters are

\$Z_A = 50 \Omega \$
\$T_A = 5ns\$
\$Z_B = 75 \Omega \$
\$T_B = 10ns\$
Rise time of source signal \$\tau_r = 0.1ns\$

I took this website as reference to come up with the schematic below:

As nothing about the voltage source was given other than the rise time, I didn't really know what to put as its parameters, so I took most of the parameters given in the reference website.
I then probed the wire between R2 and TL-A to get the graph.
First of all, is my simulation even correct? This is the first time I'm using LTSpice, and I'm completely new to this electronics topic.
Second, as I've only seen TDR with one transmission line, I'm not sure how to interpret the graph.
a) I thought this circuit is similar to 3 resistors in series - R2 (\$50\Omega\$), ZA (\$50\Omega\$) and ZB (\$75\Omega\$). So shouldn't the incident voltage at the point between R2 and TL-A be \$\frac{50}{50+50+75} * 2V = 0.571V\$?
b) I understand that the time taken for the signal to come back to the probe point is twice the transmission delay. Isn't this the case be it 1 or 2 transmission lines?
At the probe point, I thought it takes 2(5ns + 10ns) = 30ns for the reflected signal to first reach the probe point, meaning the voltage level at that point is constant until 30ns? Why is the voltage level changing at 10ns already, and for it to actually increase?
c) Why are the next voltage level changes at time intervals of 20ns? Why not at multiples of 30ns?


texts: Antenna matching network. What? Why? How?

texts:
I'm designing a small board featuring a transmitter in the 900 MHz band. Since RF is definitely not my strongest subject, I'm basically trying to follow all the datasheet recomendations regarding proper layout, PCB traces, etc. However, I find puzzling the reference to an "antenna matching network" I "might" need, according to both the transceiver (AT86RF212B) and the W3113 antenna specifications.
Consider the following picture, which can be found in the antenna's reference design:

The picture above mentions said matching network, but says nothing about how to design it.
My board currently looks like this; my traces are supposed to match the antenna impedance (50 ohm), and are really short (2.6 mm. from IC pins to balun, 6.3 mm. from balun to antenna, 11 mm. total):

The component in light blue is the antenna, ZT1 is the balun and U1 is the transceiver IC. The IC output is 100 ohm balanced, while the antenna needs a 50 ohm feed.
Given this, what is exactly an antenna matching network, why should I need one and how can I design it? I've tried searching the internet about it but the references I've found were too complex or too abstract for me.


texts: Is a perfboard made using phenol formaldehyde resin toxic to touch/inhale?

texts:
It seems that perfboard is made of phenol formaldehyde resin.

The substrate is typically made of paper laminated with phenolic resin
(such as FR-2) or a fiberglass-reinforced epoxy laminate (FR-4).

It seems that phenol can be absorbed by the skin and has acute/chronic hazards. https://www.epa.gov/sites/production/files/2016-09/documents/phenol.pdf And isn't formaldehyde the thing that keep evaporating from MDF and causes chronic disease? https://www.hse.gov.uk/woodworking/faq-mdf.htm
So, is a perfboard made of phenol formaldehyde resin safe to touch with bare hands and leave inside a closed room?


texts:
I am currently building an analog signal audio device and am designing a power supply to take mains in and convert it to +/-12VDC.

I have experience designing power supply units but not in the same enclosure as the signal processing components. My concern is the placement of this power supply unit and the effect it will have on the signal lines.

Are there best practices for ensuring there is no noise or mains hum added to the signal by the transformer? I am struggling to find resources available for this.

Thank you!


texts:
Edit: Figured it out. I posted answer.

I have a KY040 rotary encoder hooked up to a 5V source, and the oscilloscope hooked up to the CLK output. When I turn the encoder, CLK goes low as you can see at arrow A in the image. When the turn is done, it goes to ~1.1V which you can see at arrow B, it then immediately begins falling back to low over about 200ms. It stays low about 200ms and then finally goes high again. I'd expect it would just go back to 5V at arrow B and that'd be it. Any ideas what might be causing this? I'm thinking the encoder is simply damaged.


texts: Wiring up the SRD-05VDC-SL-C to an Arduino or Arduino-like microcontroller

texts:
I'm trying to wire up the SRD-05VDC-SL-C mechanical relay to a Particle Photon and/or Arduino (not the version that is on a breadboard), and am a bit confused by the datasheet.

I device I am switching on/off is 12 VDC, and I understand NO vs NC..but am not so clear on Coil 1 vs Coil 2.

What I have so far:

Basically I've hard-wired a 12 VDC source into Coil 1, while Coil 2 is being driven by a DO on the microcontroller through a transistor to bump up the current to the needed 70+ mA. Is that correct? What is common for..?


texts: Is the F.Cu upper layer really on top or just the 'upper layer' but protected?

texts:
I guess these are two very trivial questions, but I couldn't find any conclusive answer.

Below is a part of a PCB I want to create (my first ever), a SOT23 transistor and a 0805 resistor. .

My questions:

Are the red trace lines really on top of the surface, or are they underneath? Meaning, if my soldering wouldn't be so well and I spill a bit over the red traces, would it matter (since they are on top of the PCB) or are they underneath and doesn't matter at all? In case they are on top, I might need to increase the distance between traces and components.
Since pin 5 of the SOT23 is connected to pin 1 of the resistor, can I just put a blob of solder between 1 and 5 (when I put them even closer together) ? Since I'm not sure of above, I will either have one or two paths (which both are ok I guess).

(note: my PCB will have only two copper layers, one F.Cu for signals/VCC and one  B.Cu layer that is mostly ground).


texts: Very small transformer powering a microwave oven

texts:
I have recently cannibalized a 6 year old microwave oven.
I was very surprised to find the following beast at the electrical entry of the oven:

The reason: this small 1:1 isolation transformer was powering a 900W oven, without any switching technology (everything in the circuit remains at the main 50Hz): the big internal high voltage transformer was connected to it.
I have analysed the circuit and drawn the schematic:

If I'm not wrong, the blue cubic component is a capacitor, and so are the two other small blue components (as indicated in the schematic). I guess that the resistor is a bleeder, and that the tank LC circuit is tuned to resonate at 50Hz (in order to block the current in the case where the secondary is opened).
I would like to know if I am missing something, and if not, if this is a well known technique to reduce the size of the transformer connected to the mains supply. Also, what is the essential reason this thing was inserted here? Galvanic isolation?


texts: Powering circuit from output of H-Bridge

texts:
I’ve got an old car that I am building a circuit to add automatic window functionality to.  The circuit operates like this - when the window switch is pressed for less than .3 seconds it continues to run the motor until the window is open or closed.  Window switch held longer than .3 seconds and the motor will stop once the switch is released.  This works well on the driver’s side where it has a constant 12v wire available to feed my circuit.  The passenger side is another story.  On the passenger side door, the switch has 2 wires that are fed from the passenger switch on the driver’s door.  If the passenger switch on the driver’s door is not pressed up or down, both wires are 12v.  If the passenger switch on the driver’s door is pressed up or down, one of the wires leading to the passenger door will be 12v and the other pulled to ground.

My circuit has inputs for 12v, ground, window switch up, window switch down, and 2 outputs from an h-bridge to power the motor.  The motor pulls around 2 amps while running, and roughly 7 amps when stalled or starting.

In order to preserve functionality on the passenger window with both the passenger and driver’s side passenger switch, I think I need to modify my circuit to handle being powered by these 2 wires leading from the driver’s side to passenger switch knowing that both wires can be at 12v or either but not both (at the same time) can be pulled to ground.

Does anyone have a suggestion on how I might power my circuit with these 2 wires?  There is a dedicated ground wire available.  However these wires are OR’d together they will be powering an h-bridge (to drive window motor) in my circuit so there will be up to a peak of 7 amps of current running through them. These window switches form what I believe to be a mechanical h-bridge, so generically what I am attempting to do is power my circuit with the output of this mechanical h-bridge.

As a side note, I'm attempting to design the circuit so it is plug and play and there are no modifications needed to the existing car circuitry.

If anyone has a suggestion, it is much appreciated. Thank you!


texts: What are chances a BJT switch is damaged if a capacitor discharges to ground

texts:
I have a power BJT NPN 2n3055 driven by 12V 25khz square pulses.  The transistor is able to withstand 15A continuous current.

The capacitor is discharged when Q1 is open. Could it create a problem for the transistor?

Can the capacitor discharge be a potential problem for the pulse generator "V2"?

I actually built this cicruit and so far it's still alive.

simulate this circuit – Schematic created using CircuitLab


texts: DC LVDT Excitation voltage to NI CompactDAQ

texts:
I am currently working on getting reading from an LVDT for a project the present model is the DC LVDT model Omega LD620-25

As per it's datasheet the model requires an excitation voltage of 10-30V and a maximum current of 25ma

http://www.omega.com/pptst/LD620.html

as for the data acquisition modules available: the NI 9237 and the NI 9220 using a compactDAQ module

as the NI9237 has an internal power of 150mW the maximum current obtained is 15ma, will it be enough to use?

the NI 9220 will be used for data acquisition but does not provide any excitation ports!

as for another solution I was thinking of using a normal 12Vdc 100ma AC-DC adapter with a variable pot or a voltage divider circuit to provide the needed voltage

but I have several concerns regarding grounding the circuit. in such scheme I will have two independent grounds!

What will be the best solution to connecting the LVDT module to the NI 9220 and providing an external excitation source?

Thank you

* Testing * Can only read a constant value that doesn't show displacement

Hello Again,

I have connected the LVDT to the 9220 Acquisition module with external excitation of 11.5 volts ( measured) the external adapter is connected to a Voltage regulator that output the 11.5V excitation

The connected signla sig+/- are connected to the 9220 differential input on channel 0

The circuit ground is the regulators ground

I cannot get a voltage variation from the LVDT the output is around 10.2 volts and stays that way even if a displacement occured

The following screenshots shows two cases:

1) the circuit ground is connected to the com port of the 9220 and the regulators

2)the circuit ground is connected to the regulators ground and only a0+/- are used on 9220

Is it possible to be a grounding issue ? where the variation is not detected or isolated?


texts:
I live in South Florida an as such need to have generators for hurricanes.

I have 2 Generators, a small 3300 Watt Inverter and a big loud 9000 Watt generators.

Edit:  My plan is to use only 1 generator at a time.  My 2 Generators are:
Small Generator Larger Generator.  I am looking for a solution that will allow me to use the smaller quieter Genset overnight and the more powerful one during the day.  Not looking to use both at once.

The small inverter is what I use overnight to power the necessities, such as Aquarium Equipment, small window AC, Fridge and freezer.  It works great, is very quiet and efficient and runs through the night.  However I would like the option to power some of my bigger stuff during the day off the big generator and some 240 stuff such as Pool pump, stove, etc..

I am planning on having a generator tie in installed in my electrical panel.  along with a disconnect so I do not back feed the grid.

240 power is basically 2 120 circuits out of phase.  What I would like to know is can I consider each leg independent?  Can I connect my 120v Generator to 1 leg and just make sure my 'crucial lines' are powered by this leg.  Over night I would ensure all my 240v Breakers are off.

When I want to power my 240V stuff during the day I could disconnect the small inverter and connect my bigger generator,  then in my panel choose my desired 240 loads and activate the breakers for the 240 loads I want to run?

How would I achieve this...  My Small generator has a TT-30R Outlet.  I would get a cable and connect that to a L14-30 Connector, but only to one side.  The big Generator has native outlet of L14-30 so I could use the same generator tie in for that at full 240V.

I know there is the potential for my load to be unbalanced.  However I would not run the AC during the day and the running amps of the Fridge, Freezer and Aquarium are pretty low.  so in the grand scheme of things I think it would end fairly balanced.  I am not looking to do this DIY, I am gauging the feasibility before I try to hire an electrician.  Additionally I find it helpful to understand things somewhat before I hire someone.  Not all Tradesmen are equal and I what they do needs to make sense to me before they do it.


texts: When using gEDA some components are ignored by the ratsnest. How should this be handled?

texts:
I have noticed that when running gsch2pcb to convert a gEDA gschem schematic to a pcb layout that certain components that are properly connected in the schematic are unconnected in the PCB layout. In particular, transistors from the stock symbol library are affected but this has been seen for some other stock components too. (gschem version 1.6.2.20110115 - Ubuntu x64)

To demonstrate this I created a new schematic as below

Then checked the connections (using gnetlist -g drc2 demo.sch -o /dev/stdout) to ensure everything is connected up. All components have been assigned valid footprints.

pat@frog:/tmp/x$ gnetlist -g drc2 x.sch -o /dev/stdout
Loading schematic [/tmp/x/x.sch]
Checking non-numbered parts...

Checking duplicated references...

Checking nets with only one connection...

Checking pins without the 'pintype' attribute...

Checking type of pins connected to a net...

Checking unconnected pins...

Checking slots...

Checking duplicated slots...

Checking unused slots...

No warnings found.
No errors found.

This is then converted to a pcb layout using gsch2pcb and the netlist file loaded and we see the following ratsnest (I autoplaced the components as well):

So why is the NPN transistor being ignored? It is a standard gEDA symbol (npn-3.sym) and a standard footprint (TO92) from the PCB library. I both loaded the generated netlist file and executed the generated .cmd file and both these files list the pins on Q1. The netlist below has all 3 pins of Q1 connected to something.

pat@frog:/tmp/x$ cat x.net
unnamed_net3    R3-2 LED1-2
unnamed_net2    LED1-1 Q1-C R2-1
+5V S1-2 R2-2
GND R3-1 Q1-E R1-1
unnamed_net1    Q1-B S1-1 R1-2


texts: What is "tracking" on a bench power supply?

texts: I'm looking at buying a bench power supply. Some of them have Constant Voltage / Constant Current (CV/CC) listed as a feature, and that I understand. But some also list tracking as a feature. What does tracking mean in this context? Why would I want that feature?