texts: Where to find Advanced Schottky TTL Schematics

texts:
I am currently having difficulty locating the circuit diagrams/schematics for the Advanced Schottky versions of the 7400 IC series.  While the standard TTL data books seem to have depictions of the L,LS,H, ect, the volumes dealing with both ALS and AS do not seem to contain circuit diagrams.

As http://www.slideshare.net/Ajlaaa/logic-families-16246507 seems to have a diagram for the NAND gate (SN74AS00) (unfortunately does not contain a reference) there should presumably be the others published somewhere.

Does anyone have any idea where these might be published so I can get a look at them?


texts: Convert 48V battery bank to 12V for boat appliances - Inefficient?

texts:
I need a 48V bank for an electric motor on my boat. I also need 12V for my appliances. Obviously keeping both a 48V and 12V bank would be most efficient but the space required and cost of maintaining 2 banks is a bit much. So I was thinking of using a 48V DC to DC convertor to convert a 48V bank to 12V for my boat appliances(lights, pumps, etc.)

http://pt.mouser.com/ProductDetail/Murata-Power-Solutions/HPQ-12-25-D48N-C/?qs=sGAEpiMZZMtwaiKVUtQsNaluUzA10QGezHFBNv8sYMI%3d

But how much would I lose in terms of efficiency? Would the losses be too great?

Would the bank of 4 x 12V 100AH batteries connected in series give me roughly 400AH of use when drawing only 12V after the conversion? Or would the available AH be much less due to the losses from the conversion?


texts: How much AC will I need for my 12v DC transformer?

texts:
I feel like my question probably has a simple answer, but I don't deal with the back end of electricity often, so I want to make sure I do things right.

I am building a series of LED RGB light boxes for my wife for a trade show background.  They'll need a total of 850 watts separated semi-evenly across five LED decoders.  This is the decoder I am using (http://www.amazon.com/gp/product/B00PQASR9K?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00).

I am planning to buy five 12v 30a transformers, which I believe will be plenty sufficient for this load.  This is the transformer I'm planning to get (http://www.amazon.com/Singpad-Supply-Regulated-Transformer-360Watt/dp/B00N2PRMWY/ref=sr_1_1?ie=UTF8&qid=1433898154&sr=8-1&keywords=Singpad+new+style+led+power+supply).

My question is this.  How much AC power will I need?  Is it a 1 to 1 ratio (so the AC would also need to be sufficient to handle 850 watts)?  What phase do I need?

My options for electrical power that I can purchase for the trade show are:
1) 20 amps single phase 120v
2) 30 amps three phase 208v

There are a couple of additional options with more amps, but I think one of these should be sufficient.  Which will I need?

Also, I've never hooked up a transformer of this kind, so bonus points if you can point me to an online tutorial.

Thanks!
Nick


texts: Library file error while using a Third party component( INA138)

texts:
I want to use the INA138 as a current sensing amplifier but its symbol is not available in Ltspice so I downloaded the .lib File from https://www.ti.com/lit/zip/sbom140 here.
I then opened the file in Ltspice and clicked on the (.subckt INA138  + - Vs GND OUT) name of the component besides the subckt title and thus right clicked on it to create a symbol. I updated the model file for the symbol and saved it but when I use it I am getting an error stating
"Could not open the library file"
If anybody knows how to solve this please respond. Thank You


texts: Designing Board for ARM M0, How to Program

texts:
I am attempting to design my own microcontroller board with various sensors and peripherals.  I plan on using the board found here (https://www.digikey.com/product-detail/en/stmicroelectronics/STM32F030C8T6TR/497-17331-1-ND/7650387) as the MCU, or another board if it is better/easier to use.  Reading the datasheet, it seems that I can boot from user flash, system memory, or embedded SRAM, and the bootloader will program the flash using USART, and and ARM SW-DP interface exists to connect to the MCU.  I'm not entirely sure how interface so I can program it.

In Essence: What pins should I be looking at to connect to to program the chip?   What external circuitry (if any) do I need?


texts:
We need to use the audio output of a wireless doorbell to trigger a stable DC voltage which is going to keep switched a 3.3V DC relay as long as the audio output is present.

The relay is supposed to power/open an electronic lock until the doorbell audio finishes.

The doorbell I'm using is also a 3.3V device.

When applying the audio output directly to the relay, the relay was playing the audio just like a loudspeaker. This happened even when I tried to even out the audio using capacitors.

Here's an image of the Doorbell used

And this is the wireless switch for the same doorbell

These are the capacitors I tried for smoothing away the audio

The relay was still playing the audio like a loudspeaker (instead of being switched) even after I used these capacitors. do you think capacitors with different values could help or are there better solutions?


texts: Strange capacitive soil moisture sensor readings

texts:
I am in the process of building an automated irrigation system using capacitive soil moisture sensors and Arduinos.

My challenge comes in with the soil moisture sensors bought from Banggood.com.  I attempted to waterproof the sensor by sealing the the top-part of the sensor with bathroom silicone, and in another attempt, using a combination of heat-shrink and silicone.  The sensors work nicely and still give accurate readings while being waterproof.

The challenge comes in when the sensors are buried or placed in the field.  I want to measure moisture at 20mm underground.  When I buried the sensors, strange readings started occurring.  The readings are erratic and in most cases completely outside of acceptable ranges (acceptable ranges are 300 - 750 analog readings using an Arduino Nano).  This happens when I insert the sensors into soil or when moisture touches the silicone cover of the sensors.  This situation also occurs when I activate my sprinklers (leading to the above case where water touches the silicone).

My setup includes 4 Arduino Nano's, 2 x 12V solenoids connected to relays controlled by 2 Arduinos.  The entire setup is powered by a single 12V 60W power supply.  A 5V regulator is used to power the Arduino's from the main 12V line.

I've tried covering the sensors with a bucket to prevent moisture contact, but the invalid readings still occur.  Could it be that minerals inside my soil are affecting my readings?  What could be causing these strange readings?

Edit 1: I should mention that the erratic readings are always at the drier end of the spectrum. Thanks @Reroute for the advice


texts: If I lower the volts on a computer fan will the needed amps increase? Im new too electrical engineering (updated)

texts:
I have a computer fan that I am using for a school competition. The rules state that voltage used can be no higher than 9 volts but most fans are 12 volts. The fan that I have is has a recommended 12 volt 4.5 amps. So if I used a 9 volt battery or 7.2 volt how many amps should that battery be? How do volts effect amps in motors? I am new to all this and so a simple answer would be appreciated. Also I need it only to run for about 10-15 minutes at most so if you have any battery recommendations that would also be helpful. The rules for batteries are no lithium or lead allowed. The rules are very prohibitive.

Newly Added Information

I am building a small scale hovercraft that has to be as light as possible. However I am awarded points for amount of weight it can carry. I am using this fan to fill the hovercrafts skirt. I have to use a computer fan because the rules state I can only use brushless motors if it is in a computer fan otherwise motors have to be brushed which I have had issues with. I found this fan in my house and found it very powerful. Here is a link https://www.digikey.com/product-detail/en/delta-electronics/PFR0912XHE-SP00/603-1707-ND/3078695 Here is a full copy of the rules its under hovercraft http://api-static.ctlglobalsolutions.com/science/SO_C_2018FINAL.pdf


texts: Does a dangling wire really electrocute me if I'm standing in water?

texts:
We've all seen this scenario in movies; somebody has to cross a room half filled with water and there is a dangling electric wire that shoots sparks everywhere. The poor person has to cross the room but cannot do so because if the wire hits the water he is obviously electrocuted since water is a conductor.

But is it so simple in real life? If I'm really standing in water in a room, and a high voltage wire hits the water, how does the electricity flow through me to electrocute me? Only my feet are touching the water, no other bodypart of mine is touching anywhere. And realistically there probably would be some piping etc. connected to ground somewhere that would conduct the current to ground. How would I be electrocuted if the current just flows past me?

I suspect this is similar to the well known situation of somebody dropping a hair dryer into a bathtub with a person in it. Why doesn't the current in this situation flow either from the live wire to the neutral wire or through the drain to the ground? Why does simply being in "high voltage water" electrocute me? (And yes, I know the scenario is not so likely with modern appliances but let's consider this in theory).


texts: Op amp picks up power rail oscillations from boost conveter

texts:
I've built a circuit which detects ambient audio through an electret microphone, amplifies the audio signal using a LM386 op amp (gain = 200), and then processes that audio information. The board is powered through a LM2623 boost converter, which ramps up a 3.7V LiPo battery to 5V for the power rails on the board.

The op amp circuit is set up like the gain=200 diagram in its datasheet. The converter is set up according to the typical application schematic in its datasheet .

The LM2623 (and, from what I understand, many boost converters) produces small oscillations on the 5V-GND rails - typically no more than 1% peak-peak. This wouldn't pose an issue at all, except that the audio signal my op amp is supposed to amplify is also very small.

I have 100 uF and 1 uF capacitors between 5V-GND before and after the converter, as well as near the op amp.

It seems that my op amp is amplifying the oscillations on the 5V-GND rails, thereby ruining my audio data. I've confirmed that it is indeed the oscillations because the oscillations and op amp output are in sync and have the same frequency. I am wondering how I can avoid this problem. Since the boost converter cannot get away from rippling the output, I would like to know how to prevent the op amp from picking up this noise, or if there is something more crucial I may be missing.


texts:
I need a circuit to toggle an control line on a PSU. The existing control line  turns the PSU OFF when pulled to GND, the PSU is ON when the control line is floating or between 2.5V to 5.5V. I want to toggle this from an external device that has a open collector output which pulls to GND, except I need it to be ON when pulled to GND instead of OFF. My current thought is to use the following circuit, will this work as I intend it too? is there a better way to do this? The circuit is used to disable the power supply on a schedule in order to save power for a solar/battery application so current draw need to be as low as possible. The Datasheet for the PSU states the input current for the control pin is -400uA, if this is sourced from an internal pullup, would that be enough to bias the PNP and pull up the base without needing the 10-30V connection and zener?
Thanks,
-jER

simulate this circuit – Schematic created using CircuitLab


texts: How to keep decompensated op amp in linear region?

texts:
Background

For transimpedance applications, you want to keep op amps in their linear region and avoid  op amp saturation and overdrive recovery.

This can be done with a simple automatic gain control circuit when using a unity gain stable op amp e.g.

simulate this circuit – Schematic created using CircuitLab

When the diode switches on, the closed loop response maintains the same bandwidth, but its magnitude is decreased. The high frequency feedback factor Cfeedback/(Cfeedback+Cin) approaches 1, but its not a problem because the op amp is unity gain stable. I have implemented this with an OPA656, and it works well.

This won't work with a decompensated amplifier. It will oscillate when there is too much high frequency feedback. I have seen this with the OPA846.

Question

How do you keep a decompensated amplifier in its linear region in a transimpedance application?

I have tried simulating the circuit below, with the hope that switching in extra input capacitance would decrease the high frequency feedback, but the results are poor.

simulate this circuit

The component values in the schematics are not what I am using in my actual circuit. They are round values to simplify discussion of the circuit e.g. the high frequency feedback factor of the first circuit when the diode is off is 1/101. My actual component values are tuned for maximum speed, close to the edge of stability, not exactly known due to board parasitics, and would be distracting from the question.


texts:
I want to port a RTOS in STM32F4Disco board. I'm a newbie in this area and unable to understand how to adjust the configurations according to a new target and the whole porting process. So right now, I need to understand from where should I start and resources I've to go through to accomplish this. I've searched for documentation and guides which will enrich basic level knowledge in this purpose but couldn't understand which one to follow, what will be the first step to dive into it, what will be the flow of tasks I should follow. Also if I need to learn any script or language, please let me know.

Is there anyone who could provide me any direction regarding this?

Edit: I've got this guide but I need something detail. I'm not trying to write any RTOS, I just want to port Tizen RT in a new target i.e. STM32F4Disco board.


texts: What is "ripple bandwidth" in filter terminology?

texts:
I'm told "ripple bandwidth" is different from a "-3dB bandwidth" or corner frequency. How is this commonly defined, and how do I derive it?

My application:

There seems to be a discrepancy in the way  Elsie (a filter design package, mine  v2.75, fully registered version) defines corner frequency, \$f_c\$ , at least for an LPF.

Normally \$f_c\$ defined as -3dB \$S_{21}\$ point.

In Elsie, If I set \$f_c\$ at 30MHz, \$S_{21}\$(30MHz) = -0.5dB, but \$S_{21}\$ = -3dB point at about 38 MHz, VSWR = 1.1 at 30MHz, for a 0.01dB ripple, 5-pole Chebyshev capacitor-input LPF.

If I set \$S_{21}\$ = -3dB at 30MHz, I get \$f_c\$ = 23.686MHz, VSWR(30MHz) =4.1

I'm told that Elsie is defining \$f_c\$ in a different way, based on the "ripple bandwidth".


texts:
I'm stuck with a question when reading a textbook:

The question is a situation as follows:

The very high internal resistance of digital multi-meters, in their voltage measuring ranges, can be used to measure extremely low currents (even though the DMM may not offer a low current range explicitly).

Suppose, for example, you want to measure the small current that flows through a 1000 Mohm "leakage" resistance (that term is used to describe a small current that ideally should be absent entirely, for example through the insulation of an underground cable).

You have available a standard DMM, whose 2V DC range has 10 Mohm internal resistance, and you have available a dc source of +10 V.

How can you use what you've got to measure accurately the leakage resistance?

Anyone can understand this question and have an idea?

edit:


texts: Short circuit protection in simple audio current amplifier

texts:
In my class, we are to design a current amplifier with short circuit protection.

In our design, we utilized 2 emitter follower amplifiers (Q3, and Q1).
We then added Q4 and Q7 to lighten the current load on Q6 when the output RL is shorted. This worked fine so that none of the output transistors (Q4,Q7, and Q6) were over the maximum power dissipation.

Here is the problem... When the output is shorted, the collectors of Q3 and Q1 have about 500mA going through them. This is clearly too high. If we add resistors, it adds noise to our output. What can we do to fix our amplifier? Do you know of an easier short circuit protection or how to fix ours?

http://tinypic.com/r/166akxd/5


texts: Can static be discharged when removing sensitive electronics from a static shielding bag while you and the bag are at the same voltage?

texts:
Suppose you have a static/ESD shielding grey bag housing electronics sensitive to ESD.  I believe that this type of bag has a static dissipative surface and a conductor on the inside serving as a Faraday cage.  While these bags offer a high level of protection, they don't shield the contents 100% from static electricity.
Now suppose you have a setup where you have a static dissipative mat, you are connected by a static dissipative wrist strap to the mat, and the bag is placed by you onto the mat while wearing the wrist-strap.  However, the mat is not grounded externally to a true ground, but connected to a metal object, e.g. a metal computer case.  As I understand it, after being placed on the mat,  you, the metal object, and the bag are at the same voltage/potential (not zero, and so different from the question in How should I use a static-shielding bag prior to opening, and why?)
My question is: is it safe from an ESD standpoint to then remove the ESD sensitive electronics from the bag (possibly handling them via a grounding plane on the electronics)?  In other words, are the contents of the bag at the same potential as your hands or the mat?  If it's not safe, is there a safe way to do this without potentially causing damage, or does the mat necessarily have to drain charge to a true ground?
The reason I ask is that I see this ESA setup recommended here and there in this and other stack exchanges (https://superuser.com/questions/975427/how-to-properly-use-an-antistatic-wrist-strap-when-working-on-a-desktop-pc), and the ANSI standard S20.20 talks about equipotential bonding.
I am wondering if someone would be able to answer with the appropriate theory, whether or not charges between one's hands and the contents of the bag will equilibrate/equipotential bond when handling a static shielding bag or when it is placed on a static dissipating surface.


texts: If a flip-flop D is given in input D = 1 when the clock is C = 1, and then, when the clock becomes C = 0, D = 0, what will be the status eventually assumed by the flip-flop? Will it be 0?


texts: What is this strange long wire for in a single induction cooking unit?

texts:
Tonight I dismantled one of those single induction hobs:

Inside there were two PCBs. The incoming mains was wired to the top left PCB, while the other contained all the low voltage components, plus some more high voltage parts.

There are two white wires connecting the two PCBs. One is short, as you would expect. The other is much longer, and part of it is covered in heat proof braid, and is held down by a loop of metal.

What is the reason for this piece of wire being so much longer and covered in heatproof braid?


texts: How to calculate inductive and capacitive reactance?

texts:
I am studying a project that calculate reactance power. I can measure apparent power, real power and power factor. Therefore I can calculate total reactance power. But I don't know whether it is inductive reactance or capacitive reactance.
This is my circuit

How can I describe values of inductive and capacitive reactance?
Thanks


texts: Cutoff frequencies of active this filter?

texts: How can I calculate precisely the roll-off frequencies of this configuration? The passband seem to be between 3.1Hz to 78.1Hz. I tried using the equations for the inverting active bandpass filter but they gave different results. I can't seem to be able to get these values with any combination of values, what am I missing out?


texts:
I'm trying to solve a practice problem, which is represented by the schematic below.

simulate this circuit – Schematic created using CircuitLab
We are asked to relate the voltages \$V_1,V_2\$ to the output voltage \$V_o\$. The value of R is considered to be known, and all transistor base voltages are considered zero. The input voltages aren't specified as DC or AC, but previous problems from the set considered them AC. The base-emitter bias voltages are considered to be \$Vbe = 0.7 V\$.
My steps to solve the problem:

The left part of the circuit is a buffered current mirror. This means that the current across the leftmost resistor 2R is reflected across the rightmost resistor R.
The current across the leftmost resistor is \$I_c = \frac{V_1-1.4}{2R}\$. This current is reflected to the rightmost one, R
We can calculate the voltage drop across R to find the collector voltage of Q2.

\$V_C2 = Vce_2 = Vcc - I_cR = Vcc - \frac{V_1-1.4}{2} \$
If my calculations are correct, this is the input at the non-inverting terminal of the opamp. And this is the point where I can't determine the operation of the opamp, and am conflicted. I've seen how the most common configurations are wired, but none of them feature this topology. Textbook inverting configurations require the non-inverting input to be grounded. Inverting configs require the inverting input to feature feedback, but it's input is grounded. Differential amplifiers have another resistor after 0.5R to ground.
I also understand that, ideally, the voltage at the input terminal should be the same as the output of the mirror, since no current flows in or out the terminals (in an ideal amp) and there's a virtual ground between the two terminals.
Any pointers on how to decipher this are appreciated.


texts:
I've made a simple SPI test for Teensy 3.2 board.
While trying to get the communication up and running I noticed that while the alternative SCLK pin14 generated the clock, no MOSI data was outputted from the default DOUT pin11 of the Teensy 3.2 board.
I checked the levels with an oscilloscope.
I set the alternative MOSI pin and voila, that pin works fine.
By calling SPI.begin() I assume the default pins are configured:
MOSI pin 11
SCLK pin 13 (but used by LED so I use alternative on pin 14)
nCS pin 10 (I do control it manually, as stated in Arduino documentation)
For some reason pin 11 doesn't work, even when I try to declare it manually.
Whoever can try and test it out as well , please see the Arduino code attached.
Do you have issues as well or am I missing here smth ?
Arduino code (no actual chip required):
Commenting or uncommenting  //#define ALT_DOUT  helps to select the correct pin easily.
#include <SPI.h>  // include the SPI library:

//#define ALT_DOUT //DEBUG Select Teensy DOUT location
#define OSC     //Use PWM input of the MAX chip

// === PIN Definitions ==== //
const int led = 13;

//MAX6967 === SPI

#ifdef ALT_DOUT
  const int MAX6967_DIN = 7;  //Using Alternative pin to send data out
#else
  const int MAX6967_DIN = 11;  //Teensy 3.2 default doesn't seem to work
#endif

const int MAX6967_SCLK = 14; //Configured as Aleternative. on Rising edge, data shifts.
const int MAX6967_nCS = 10;  //Must be low to data to enter. Recent 16bit latch on rising edge of nCS
const int MAX6967_DOUT_OSC = 11;

// === Control ===
/*
uint16_t MAX6967_D15; //Read / Write

//Register Aadresses
uint16_t MAX6967_P0_REG = 0x00;
//uint16_t MAX6967_P1_REG = 0x01;

uint16_t MAX6967_CNFG_REG = 0x10;

uint16_t MAX6967_RUN_NORAMPUP =
*/

//LED intensity control
//Individual 8-bit PWM per CC output
//Individual 1bit analog
//Global 3bit analog control to all outputs

// === Data === //

// === DEBUG ===
char dbuf[100]; //Debug sprintf buffer
int once = 1;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600); //USB

  SPI.begin();
  MAX6967_init(); //Led driver specific inits

  pinMode(led, OUTPUT);
  digitalWrite(led, HIGH);

}

void loop() {
  // put your main code here, to run repeatedly:

  MAX6967_write(0x82, 0x04);

  delay(1000);
}

// ====== Custom functions =====

void MAX6967_init(void){

  #ifdef ALT_DOUT
    SPI.setMOSI(MAX6967_DIN);
    digitalWrite(MAX6967_DIN, 0);
  #else
    //SPI.setMOSI(MAX6967_DIN); not even with this.
    //otherwise SPI.begin should init the default, right ?
    pinMode(MAX6967_DIN, OUTPUT);
  #endif
    Serial.println(MAX6967_DIN);

  SPI.setSCK(MAX6967_SCLK); //Use the alternative on pin 14
  pinMode(MAX6967_nCS, OUTPUT);
  pinMode(MAX6967_DOUT_OSC, OUTPUT); //Set as DOUT

  digitalWrite(MAX6967_SCLK, 0); //Clocked on the rising edge, so default is low.
  digitalWrite(MAX6967_nCS, 1);
  //digitalWrite(MAX6967_DOUT_OSC, 0); //if set as DOUT

}

void MAX6967_write(uint8_t address, uint8_t value) {

  // [R/W][D14 - D8]{D7 - D0]
  address &= ~(1 << 7); //The MSB bit of the address is R/W - 1/0

  //address |= (1 << 7); //The MSB bit of the address is R/W - 1/0

  // take the SS pin low to select the chip:
  digitalWrite(MAX6967_nCS,LOW);
  //  send in the address and value via SPI:
  SPI.transfer(address);
  SPI.transfer(value);
  // take the SS pin high to de-select the chip:
  digitalWrite(MAX6967_nCS,HIGH);

  sprintf(dbuf, "address: %04X Value: %04X \r\n", address, value);
  Serial.print(dbuf);

}


texts: Understanding 75 ohm antenna connection on a hifi receiver

texts: Dear electrical engineers! I am trying to understand what stands behind a 75 ohm (unbalanced) antenna connection on my hifi receiver? I understand the "unbalanced" part,  however not the "75 ohm" one. I know that an antenna will  have resistance and impedance, which will hopefully result in being 75 ohm overall. Would I be right to say that the receiver will appear as a 75 ohm (resistance + impedance) load from the antenna's point of view? I am trying to use 4nec2 software to model a simple Yagi-Uda receiving antenna and I am not sure how to define a "source" which is the receiver. Thank you.


texts: Do time contant vary with the order of filter?

texts: I have this doubt whether time constant varies with order of filter or not.If not, when/what (type of) circuit has more than one time constants?


texts: How to implement 8-bit 2:1 multiplexers on a PCB?

texts:
I need to implement a 2:1 multiplexer for 8-bit data. That is: as inputs it should take two 8-bit numbers and a Select line; and as output an 8-bit number.

I could use two 74HC(T)157s (this is a quad 2-input multiplexer), however, because of its pinout (see below), implementing an 8-bit 2:1 multiplexer would cause a mess on the PCB, and I will probably use several multiplexers in this project.

What is the common way to implement more-than-one-bit (2:1) multiplexers on a PCB? Are there readymade ICs for this (I couldn't find them) or is there a way to keep the PCB uncluttered?

Since I will be home-etching the prints I'm unfortunately rather limited to one layer. The final project should be a home-made CPU of discrete components (really).

This is the pinout of the chip I mentioned. For example, 1I0 and 1I1 are inputs for 1Y. S is the common selector.


texts: What is the difference between these two burden resistor configuration

texts:
On my ADC evaluation board the burden resistor configuration used is like on the left side , but from what I know this configuration is for non differential signals, This ADC ALWAYS takes differential measurement and cannot extrapolate the reading on P or N line separately. The way I have always seen others do it like in current transformer is the configuration on the right side.

simulate this circuit – Schematic created using CircuitLab
Is there any benefits why i would choose to configure it like the left side ?


texts: designing load for the MCU to drive by output current

texts:
I am talking about a plain MCU (ATMega32, max 20 mA per pin) output asserting a logic line high or low. I.e. to drive this IC: http://www.ti.com/lit/ds/symlink/ads114s08b.pdf

There is a table specifying 1 uA current draw for its digital inputs:

That probably does not mean that the output current of the MCU is 1 uA as well if directly connecting the two pins together (i.e. MCU output pin to ads114s08b input pin). Does it ?

In case I am right, what will the current be and how can I bring it to < 20 mA no matter what ?


texts: NPN Transistor For 3 volt base to switch/control 5 volts

texts:
I have a 3 volt microcontroller that I want to control the power to a 5v microcontroller. What transistor can use a 3 volt base and allow 5 volts through the emitter/collectors. What type of NPN transistor will work for this application? (a MPS222A doesnt work :/ )

simulate this circuit – Schematic created using CircuitLab


texts: Implementing circuit with d-flipflop in verilog

texts:
I'm fairly new to Verilog and I'm currently trying to do a structural implementation of a circuit that consists of an d flipflop, it has inputs x and y, x and y are exclusive or'd and that result is exclusive or'd with the current state, and used as the input to the d flip flop. and it'll use the result state from the flipflop in the next run, etc. But I'm not too sure how to construct it.

The circuit looks like so:

And my code is as follows:

module circ(clk,x,y);
 input clk,x,y;
 wire state=1'b0;
 wire xoy,d;
 xor(xoy,x,y);
 xor(d,xoy,state);
 dff a(d,clk,state);
endmodule

module dff(D,clk,q);
input D,clk;
output q;
reg q;
initial q<=0;
always @ (posedge clk)
 begin
  q<=D;
 end
endmodule

I'm pretty sure the d flip flop code is correct but when I try to test this my d and state values are just x for some reason. When I put in different x and y values in my testbench nothing happens, "state" and "d" just always says it has value "1'hx" in the simulation. Why is this happening and how do I actually assign an value to them?

I'm just not really understanding what you're supposed to do with the state, I'm assuming you need to give it a state at the very first run but if I give it a state isn't it just going to set state to that value every single time that module is accessed?

This is what state looks like on the simulation chart, it just stays red forever:


texts:
I would like to subtract one frequency, varying from maybe 40kHz to 41kHz, from a 40kHz signal, to end up with a signal from 0 to 1kHz.  Right now the 40kHz fixed signal is square and the variable signal is sinusoidal, but I can filter and make either signal square or sinusoidal.  I would like to use a mixer like the SA612.  The circuits that I've seen online are way more complicated than I need... Isn't there just a way to hook one signal to the input and the other signal to the oscillator?

I tried wiring the variable signal to "input A" of the the mixer, grounding "input B" (to get a nice 5v pk-pk signal on the inputs), and similarly hooked up the 40kHz signal to "oscillator A", and the other side to ground.  It looks like both the input and oscillator pins are getting good signals, but the output is garbage in the 40kHz range (with noise), with no strong component anywhere in the 0 to 1kHz range like I was expecting.  Any advice?  THANKS!!!

EDIT:  The two signals are on separate lines.  I'm trying to build a Doppler Effect speed measurement device.  The 40kHz signal is being fed to an ultrasonic transmitter.  The received signal slightly faster than 40kHz depending on how fast the object is moving towards the receiver.  I want it to be a standalone device operated by a microcontroller so I don't want it to involve a PC and audio codecs.  I suppose it doesn't have to be analog... I could make both signals square.  I just don't know what type of IC makes this task somewhat less exhausting.

EDIT #2: For testing purposes, I am now putting a 37kHz square wave through the SA612 input, and a 40kHz square wave on the oscillator, expecting to get a noisy waveform with a strong 3kHz component on the output.  I'm now using resistor dividers to get the input signal to about 60mV pk-pk, centered around 2.5VDC (DC bias).  The oscillator is now 250mV pk-pk, centered around 2.5VDC (DC bias).  So Pin 1 is connected to 37kHz signal, Pin 2 is connected to 2.5VDC (so that peak-to-peak is measured at 60mV), Pin 6 is connected to 40kHz signal, and Pin 7 is connected to 2.5VDC (so that peak-to-peak is measured at 250mV).  I didn't know if I needed to center those signals at half the rail voltage but at least now I'm getting something on the output.  Unfortunately, the output signal looks just like an amplified version of the input signal (and both outputs are the same).  The help so far has been great.  Any other advice would be much appreciated.

I may end up going with an XOR gate or something but that would require additional thought to integrate the resulting signal (phase difference) to a meaningful value.

By the way, driving the ultrasonic transmitter with a square wave doesn't seem to be a problem.  The received signal is still sinusoidal.


texts: How does SD card write protect switch work?

texts:
I am designing a device which requires an SD card for logging data, and I am using Microchip USB2240 as USB to SD bridge. I have all the parts on board (Referenced by Microchip).

I am able to log data to SD card as well as read data on my computer, but I have just realized that I cannot format the SD card nor delete any files from it.

I have a thought that this might be the problem with SD card WP switch, as I am using Micro SD card which doesn't have WP switch and USB2240 Evaluation board comes with the MMC socket. MMC has a WP switch (but the connections are true).

What will happen inside MMC when I move the switch to the lock position?

On the other hand, USB2240 has a SD_WP switch, which in my case is floating. They have not provided any information on this pin in the datasheet; whether I have to pull it HIGH or LOW to remove Write Protect.

Could the problem be either the write protect switch or SD_WP pin?

All the documentation on USB2240 bridge can be found here : LINK


texts: How can I reduce loading effect in dc common drain source follower?

texts: I want to make a dc voltage buffer using an nmos source follower. I found that by making Rs as large as possible or even open, Vs= Vgs-Vth. I verified it using multisim. The problem is it suffers from loading effects. I wanted to make a dc voltage buffer using the least amount of transistors.


texts:
I made a pcb with a QFN32 with exposed pad but I feel like I've made a mistake on the stencil, in the exposed pad area.
I managed to solder it and the chip (CC1310) is programmed successfully but I'm still concerned about the stencil. The solder paste looks like a chess on the exposed pad and I don't think that this is the right pattern.


texts: AD9850 can generate others waveform beside sine wave?

texts: As know that AD9850 chip module can generate sine waveform, but does it can generate others waveform? as data sheet of AD9850 didnt mention it


texts: LTSpice - Voltage Controlled Switch in hardware circuit?

texts:
I have a question considering LTSpice's voltage Controlled switch !
(http://www.linear.com/solutions/5735)

In my circuit I want to pass on the voltage from one circuit to another with the voltage controlled switch. The switch gets a control signal, which, if >= 1V (or 0.5V), turns the switch on and connects the 2 circuits.

This is currently modelled with a .spice directive. But as I cant do that in hardware, I need to figure something out!

I tried a NPN Transistor, but it didnt really work out as I had to apply the load of the latter circuit to the emitter, what in turn altered the output I was hoping to get !

In short terms: I need something switch that goes "on" when the control voltage is > 0.5 Volt and that doesnt alter the input voltage it is supposed to carry across !

Any ideas are greatly appreciated !


texts: If speed of rotating flux and actual speed of rotor is same then what will be the torque produced in three phase induction motor and why?


texts: How to tell if a Demultiplexer's output values are maintained from datasheet

texts:
I want to know how can i tell from a Demultiplexer's datasheet that it maintains the output logic level after the address inputs have been changed.
EDIT: I do not have any datasheet to post since I have not found any demultiplexer with the 'latching' feature that I want. What I am asking here is how to understand that a Demux has this latching feature from looking at a datasheet
Example: Say i want to turn on 3 leds:

simulate this circuit – Schematic created using CircuitLab
But after the LED1 is turned ON, and I focus (point on) the second led, I want the first led to stay ON.
I tried searching on the datasheets for the keyword "Latching" or "latch" but it found nothing. Maybe i just searched on the wrong datasheets (like this one) , or is there another keyword?
In this website also says: Also some have latches built into their outputs to maintain the output logic level after the address inputs have been changed So I know some of them have this feature.


texts: How to combine a stereo audio signal, but maintain the original stereo separation?

texts:
A long time ago I had a CD player boombox and wanted to add a "subwoofer" to it (it was really just a small guitar amp with the EQ set to cut the highs and mids).  The CD player had a 3.5mm line input jack that conveniently worked as a line out as well.  My naive approach was to just bridge the right and left channels together from the line in and run that to the mono input of the guitar amp.  This had the unfortunate, but obvious in hindsight, side effect of combining the signals going to the main speakers.
Is there some sort of circuit (ideally passive) that my younger self could have built to combine the signals for the "subwoofer" while maintaining the stereo separation for the main speakers?


texts:
I've recently been moving from Arduino environments to AVR, and I'm programming a Tiny84 with the Sparkfun USBTiny programmer and Atmel Studio 7. For the life of me, I cannot figure out why I can't output a PWM signal.

I've tried so many different example codes, scoured the datasheet and set my own TCCR0A and TCCR0B bits to set the modes, but every program so far has either a) not lit the LED at all or b) lit the LED at full brightness, ie does not correlate to OCR0A at all. The LED MOSFET is on PB2 (OCR0A, right?) and works fine with a simple blink function. The code I'm trying currently: (this one outputs full brightness all the time. I've even tested with a normal 5V led on the output to make sure it wasn't the MOSFET having an extremely slow recovery time)

#ifndef F_CPU
#define F_CPU 8000000UL // 8 MHz clock speed
#endif

#include <avr/io.h>
//#include <avr/interrupt.h>
#include <util/delay.h>

int main(void)
{
    DDRB |= 1 << PB2;
    TCCR0A |= (1<<WGM00)|(1<<COM0A1);
    TCCR0B |= (1<<WGM02)|(1<<CS00);

    while(1){
        for (uint8_t i = 0; i < 255; i++) {
            OCR0A = i;
            _delay_ms(4);
        }

        for (uint8_t i = 255; i >= 0; i--) {
            OCR0A = i;
            _delay_ms(4);
        }
    }
}

As I understand, this should be phase correct PWM, clear on OCR0A match, and no pre-scaler

And the (full) schematic:

I'm attempting to put PWM on the White control MOSFET, which is driving a small section of 12V LED strip. MOSFETs are NVR4501NT1G n-channel

This is on a custom-made board which had the problem of a broken ground plane where I haphazardly placed mousebites, so I have two bodge wires to fix that issue.

Any help would be greatly appreciated; even just an example of what should work would let me know whether this is a software issue or another problem with my board.


texts: So, what's the best way to go about evaluating a device for class 1 div 2 ( or Zone 2)

texts:
We purchase a small low power embedded computer from an OEM based out of United States. The device is not currently certified for Class 1 Div 2 (or Zone 2 which is the Canada/Euro equiv). We need this certification for use in Oil and Gas applications in Canada.

I suspect that the device itself would comply (it has no big caps and only consumes about 2.4 watts), and maybe only require a change in enclosure type. I don't want to throw money away before I have a decent understanding of what they will be looking for when doing a field certification (They being Intertek or CSA Labs).

So, what's the best way to go about evaluating the device for possible certification?


texts: Analog Blackfin Processor Silicon Revision issue

texts:
Recently we got a large batch of ADSP-BF5346s that say they are Silicon Rev 3 but internally read as Rev 2. Is there a way for me to determine the Silicon Revision number on the rest of the shipment without soldering all of them? I'm thinking a bootloader/JTAG but don't even know where I would find a bootloader for that.

Here's the code I might can use if I can find a way to load it

 /* silicon revisions 0.0    1.0    1.1   */

int silrev_list[] = {0x0, 0x100, 0x101};

int running_on = (*pREG_TAPC0_IDCODE & BITM_TAPC_IDCODE_REVID) >>
BITP_TAPC_IDCODE_REVID; /* check the part */

int built_for = __SILICON_REVISION__; /* check what we built against */

int running_on_hex = silrev_list[running_on];

DEBUG_PRINT("Built for version %d.%d, running on version %d.%d\n", built_for>>8, built_for&0xff, running_on_hex>>8, running_on_hex&0xff);


texts:
I am trying to make realtime, low power 1hr audio indicator using binary counters. I don't need display so not using decade counters or 7 segment display ICs. So I bought bunch of CD4060 binary counters, because they have inbuilt oscillator.
Later I figured out I can get reliable & accurate 1Hz/1second pulse from external, crystal based, source. My question is how can I configure CD4060 to use external clock instead of using timing capacitor and resistors?
Following is the functional diagram of the IC.

Can I give external clock directly to pin 11(RS) and leave pin 10(time resistor) and 9(time capacitor) hanging without connection?
Or can I give external pulse directly to pin 9 and leave pin 10 and 11 hanging?
will leaving other pins(11/10/9) hanging introduce errors due to external noise as it is CMOS IC? I can't ground them though.

I know, I can use CD4020 here, but I've already bought CD4060 and don't want to waste them.
I know, real time clock ICs, Arduino and like solutions can be used. I don't have microcontroller programming equipments.


texts:
I am designing a PCB in Eagle, however my PCB has a bit of a complicated shape which I can not design directly in Eagle.

I want to design it in a simple CAD software and would then like to import it into Eagle.

Is there any way to import a drawing from a CAD software into Eagle to use as the dimension for the PCB?


texts: Cheap bracelet with indoor location tracking

texts:
I want to provide people at an indoor exhibition of ours with a bracelet which allows me to send a signal to it to flash a led light. At the same time I want to be able to determine the location (within 2-3 meters) of that bracelet (everyone wearing the bracelet is assumed to have given permission for this).
The exhibition consist of 1 room (mutliple rooms MAY be needed in the future, not sure if that changes anything in technology requirements).
I was thinking of some sort of radio receiver, but what kind of equipment & technology would be required to do such a thing? Also for determining the location of the bracelet, e.g. could triangulation work? (I need the cheapest solution, so probably bracelets without GPS). The battery (if any) in the bracelet would only have to last a couple of hours.


texts: Why does the voltage output of a signal generator changes with its frequency setting?

texts:
I connected a signal generator to a 5.1 ohm resistor, which may be too low comparing to the internal resistance of the generator, so I got only several hundreds millivolts amplitude for frequencies below a hundred. However, when the frequency was increased beyond a hundred and something, the voltage could rise to about 4.5Vamp (maximum). Why dose this happen?

(The specified maximum voltage amplitude of the signal generator is 20Vp-p)

Thank you!


texts: if(){} else{} if(){} VS if(){} else if(){} in PWM control

texts:
I'm using timer0 and a gpio pin to generate a 300Hz PWM signal on an ATmega2560.

The details if you care: F_CPU=16M, timer clock prescaler /256, count_max=208

The frequency changes depending on if I use an "if(){} else{} if(){}" or an "if(){} else if(){}".
The first generates 300Hz and the second generates 244Hz. Below is the code that generates the correct frequency. If I delete the curly brackets after the first two else's, I get 244Hz.

void pwm_on(uint8_t duty){
    if(TCNT0 <= duty){ //portion of counter active
        PORTB |= (1<<7); //turn on PB7
    } else {}
    if(TCNT0 >= duty){ //portion of counter inactive
        PORTB &= ~(1<<7);//turn off PB7
    } else {}
    if(TCNT0 >= COUNT_MAX){ //if counter full
        TCNT0=0;//reset counter
    } else {}
}//pwm_on

Why am I getting such a significant frequency change with code that doesn't change the functionality?

Also calling this function is the only thing I do in Main after initializing.


texts: Running barebones ATMEGA328P on 3.7 V battery

texts:
I have some questions regarding running an ATMEGA328P from a 3.7 V battery. These batteries can vary their voltage during discharge from 4.2 V to 3.0 V. So my questions are:

If I power the ATMEGA328P directly from the battery, what would the voltage of the digital I/O pins be? Would it be the voltage at Vcc (i.e. the battery voltage)?
If so, does that mean that the voltage used on a UART (TX, RX) line would be the battery voltage?
How would I go about programming the device? I imagine selecting, for example, the Arduino Pro Mini at 3V3, 8 MHz within the Arduino IDE would not work (?), because Vcc is not 3.3 V but rather the battery voltage. Would I need to switch to a 3.3 V supply for programming?

Thanks in advance!


texts: How to implement 8b10b en/decoding protocol between two FPGAs?

texts:
I'm using two Xilinx FPGAs (one Kintex 7 and one Artix 7).  The Kintex 7 is tied to its own system (OPAL-RT software, it is a simulation software that is an addon to Simulink which lets data be output to an FPGA via a user CPU input) and will be outputting the its data as 10 serial bits.

The problem I am trying to solve is to send 20 serial bits (actually, 16 bits, but when it's encoded it should be 20, if I'm not mistaken) from the Kintex 7 to the Artix 7.

They will be clocked differently, but I thought the point of 8b10b was so that the clock of the primary FPGA can be recovered by the secondary  via the data stream.

Clearly I'm not very learned on the subject of setting up a communication link between two Xilinx FPGAs, but if someone has any insight that can help me, it would be super appreciated.

Worth noting is that I have access to Vivado/Xilinx System Generator.


texts: I am making a drone for geological applications and for that we require a flight time of 1.5 hr without payload. Could anyone recommend any battery types of alternate power sources that I could use?


texts: What is the range of a direction protection relay?

texts:
I am modeling a hypothetical backup protection system for a power transmission grid and need to know if a directional relay can detect a fault if there are multiple lines and buses between the relay and the fault.

For example, in the below diagram of the IEEE 14-Bus System can a direction relay located on the Bus 2 side of line 2-4 detect a fault on line 13-14?


texts: How do I plot noise gain of an op amp circuit in SPICE?

texts:
How is an AC analysis of the noise gain of an op amp circuit plotted in LTspice?

This is a follow-on question to a prior question here: What is noise gain, really? And how is it determined in the general case?


texts: Understand how to integrate STM32F407VG MCU on custom PCB and program it

texts:
I have been messing around with the STMF407VG for a few weeks now using a discovery board. Been the steep learning curve but I think I have made significant progress on learning firmware development with it. I have gotten my code to be to a point where I wanted to have a custom PCB solution. I went ahead and looked at a few implementations of other STM32 dev boards and used that to help understand how to connect everything up.
I finally got my boards in the mail. Power seems to be okay to the target, I measured the power rails for all of the pins and looks okay. Both boot pins are grounded, and the reset line is held high. Though when I try to upload a blank project to my custom PCB, I get the error that there is "No device found on target". Only thing I can think of is that I must have miswired the port that connects to the ST LINK V2 I purchased. I never made a custom PCB with an ARM MCU before so this is my first go at it. I have attached a picture of the MCU section of the schematic. Is there perhaps some green horn mistake I made?
Any hints are welcome!


texts: Measurement of transformer with a vector network analyser (VNA)

texts:
I have a planar air core (no ferrite) transformer in a PCB. I need  to characterize the transfer function of this transformer from DC to 500 MHz using a vector network analyser (VNA).

My first question is regarding measurement method selection: I’ve used a VNA before to characterize coils and capacitors so: first I would check the expected inductance or capacitance of this device under test (DUT) in a diagram like the one below, then I would use the measurement method with the best accuracy for the given frequency range.

Now my first question is, how to select the measurement method in the case of a transformer?

My second question is regarding the smallest signals that can possibly be measured with the VNA:  I am afraid that if the voltage or current in the secondary are too small then the VNA won’t be able to measure them. My problem here is that no matter how I connect the transformer, one quantity (voltage or current) will be smaller than the primary, but as far as I know VNAs work with power (S parameters) measurements, so I don’t know how to decide (I’m dealing with a transformer with a very large ratio). How to determine what is the smallest signal the VNA will be able to measure?

Many thanks in advance!


texts:
I have a problem with the MOSFET commutation. The fall time is very slow when the load resistor has a low value. It seems like there's a capacitor. However, this doesn't happen when I use a BJT transistor instead of a MOSFET.

I've tried with lots of MOSFETs but the result is the same. I read this may occur because of the scope probe although I'm not sure how. Can anyone help me?


texts: Differential equation of the NPN transistor configured as a voltage divider

texts: The mathematical model in AC of the NPN transistor is represented by the pi model which is only one resistance in parallel to the resistors of the divider and the DC source in parallel to the collector resistance and the resistance of the load. How could you get the differential equation? Thank you very much in advance for your answer


texts:
I have a microcentrifuge which has a DC motor rated 24V, 10 Watt and 7000 rpm.

I have attached one 5W, 500 Ohm potentiometer with it to control the speed and it works fine without heating up.

This microcentrifuge is supposed to be used with a light weight part. But as I need to use it with some large tubes I have 3D printed some parts and attached on the rotor part.

This time with this extra weight my potentiometer becomes very warm within 1 minute.

Is it because of the extra mechanical load or it is something wrong with my potentiometer rating?


texts: Choosing right equipment for the Test Fixture

texts: I'm planning to build a "Test Fixture" which tests PCB via PC that reads data from the I/O module. And since i want this project to be flexible to the PCB change, my preference gone towards to the PLC ( I can easly extend the I/O number etc.). Using similar modules like "Analog Discovery 2" is seems not preferable cause of limited I/O. So I want to ask your advice on this subject. What can I use to read data from the tested PCB and communicates with PC (I don't want to build a PCB for it, since it seems not flexible)?


texts: Difference between voltage and current ratings on a component

texts:
This is a pretty basic question, but I'm new to electronics, and I'm a little confused: if you have a component that say it runs at 12V, it still needs a certain amount of current to run, right? If you add too much resistance, even if you supply a 12V difference across it, the component will not function correctly, right?

That being said, if you don't have the proper voltage (say you only have an 8V difference), but you have a low enough resistance such that the current through the component would be sufficient to power it if the voltage difference were 12V, will the compoennt still run?

I'm asking because I have a windshield wiper pump that's rated at 12V, but isn't running when I power it with an 8V, 1A power supply, even if I don't have any resistance on it (i tried this for less than a second, when 10Ω resistance didn't work). Is this because the current isn't high enough? Or the voltage? Or both?

Any assistance would be greatly appreciated. Thanks!


texts: What should be the debounce time for the diagnosis of short circuit to ground?

texts:
There is an analog input voltage pin of a microcontroller whose threshold voltage is set 0.2V. If the input voltage at the pin is below 0.2V, then it is recognised as the short circuit to ground(SCG). A value for the debounced time should be chosen in ms. When the input voltage is below 0.2V for a time as long as the debounced time, then the error bit SCG is set.
Do you have an idea how i can calculate the optimum debounced time?


texts: Interpretation of the characteristics for amplifier circuits with and without a filter

texts:
I've run simulations in AWR software for hmc414 amplifier without and with filter on output.
The conclusion after the first simulation is that this amplifier is unilateral.

Unfortunately I don't know how to refer to the characteristics of the amplifier with a filter on the output. How to interpret it and what does it imply? Does anyone have any idea?


texts: Better options for induction coils than water-cooled copper

texts:
In an induction heater one of the main problems is that the coil carries a large current. This causes the coil to become hot. There is a limit to how large diameter the wire can be, because it needs to have multiple turns (I think). The standard solution to the problem is to use hollow tubing, then run water through the tubing, thereby cooling it.

Is there a better option for making the coil? The overall goal is to make a coil that can transmit large amounts of current without getting hot.

One obvious improvement I can think of is to make the coil out of silver. Silver is both more electrically conductive than copper and also more thermodynamically conductive, so it will be able to transmit electricity better and be less susceptible to heating up.

Is there an even better way, maybe superconductors?


texts: How to debug a non working atmega88pa ciccuit. programmer can't connect

texts:
I am trying building a Mutable Instruments Branches module which includes a atmega88pa.
I am trying to connect the programmer but can't get a connection going (I've tried the programmer with another board and it works there so I don't think the issue is with the programmer itself).
When I try to connect I get:
λ avrdude.exe -c usbasp -p m88p

avrdude.exe: error: program enable: target doesn't answer. 1
avrdude.exe: initialization failed, rc=-1
             Double check connections and try again, or use -F to override
             this check.

avrdude.exe done.  Thank you.

The circuit for the MCU is

the board is 0603 SMD component based. I used solderpaste and a skillet to reflow. Upon visual inspection everything looks okay. When I connect the power nothing heats up particularly.
How would I approach debugging this? I have a multimeter.
Would I measure the voltage at ping 29, 18, 4 and 6 to make sure they are at 5V?
How would I verify the MOSI/MISO and SCK connections being properly connected to the pins on the JTAG header?


texts:
I have designed a mezzanine PCB that will sit on top of a main PCB connected via two connectors on either end of the mezzanine PCB.

If I connect the grounds on at both connectors (And thus at both ends of the mezzanine PCB), and the mezzanine PCB has a ground plane on it, will I get a ground loop issue?


texts: how to control power within a triangle automatically

texts:
I have two mains powered extract fans with sensor operated controllers.
I need to add a third extract fan that will run if either or both of the other two are on.
How do I wire this so to prevent backfeeds from one of the existing fans to the other?

as requested:

( plug should be exchanged for word socket,  plug socket )

EDIT:   so   extractor 1 and two are to control extract heat,  a sensor plug that has a hot and cold socket is how I turn each one on.   When heat is above 23 degrees, it auto turns power onto the socket, and extractor starts working, until heat in down to the desirable temp < 23 degrees.

I was going to wire from power input on each extractor, to forward on voltage to a plug socket,   when this socket has power,  this in turn will power the third extractor.

both extractor 1 and two should be able to send power to socket at same time without any issue, and the extractor 3, will only draw what it needs.

But when  extractor 1 is on, and extractor 3 is off.   How do I stop the power from the socket, going down and powering extractor 2.

This would be undesirable as i would be extracting when i dont want to from room number 2.

Hope that makes things a bit clearer


texts: Testing a I/V stage using function generator

texts:
I created a I/V stage with amplifier for my DAC project. An excerpt of the circuit can be seen in the attached picture in the "Device under test" part.
The DAC has a 3.9mA pp current output, which I convert to voltage using a high precision resistor (R302).

I want to draw an approximate bode plot of the circuit using my function generator, whose output is a voltage.
I have studied some literature, and I know that using opamps and transistors is possible to create very precise voltage controlled current sources, but before proceeding with building another device, I tried to find a easier solution by myself.

What I need is a current which is more or less the same my DAC will give as output (circa 4mA). My idea was to just use the Ohm law V = RI with the intuition (which may be wrong, since I am quite a beginner) that if I put the low input resistor in series with a much bigger one (R301 in the schematic), the input current will be dictated almost only by the latter. In other words, the small resistor almost disappears when put in series with a much bigger one. This way, I could generate the needed current by just putting this big resistor in series with the input of my circuit, and trimming the output voltage of my functon generator.

Could it be a good way to go?


texts: Up=Voltage Protection Level of a surge arrester

texts: As I have found out from web searches,in a surge arrester "Up" is the value of voltage on the terminals of an SPD while discharging the surge current. So the load which is connected in parallel with the surge arrester will suffer a voltage as much as Up(which is around 1.5 KV). This voltage won't destroy the load?


texts:
Here is a simple FM transmitter that I've been studying recently. What I'm wondering about currently is how the BJT amplifier in this circuit is biased. I believe that from the audio signal standpoint the BJT is working in a common emitter mode: the signal from the mic is input into the base, and the output appears at the collector and the voltage between the two changes the base-collector capacitance, modulating the signal. From RF signal standpoint it works in common base mode: unwanted frequencies are filtered from the collector to ground through the LC circuit, while the frequency of interest is blocked by it and fed as feedback through C2 into the emitter. The base is grounded for the RF signal through C1. Am I correct so far?

Back to biasing: looking at the circuit, it seems to be biased using "base bias". Let's calculate the quiescent current through the base:

\$I_{b} = \frac{9V - 0.7}{4700\Omega + 470\Omega}\approx1.6mA\$

It's impossible to know exactly what the beta is for the specific transistor, but let's say \$\beta=100\$. Then:

\$I_{c}=\beta I_{b} \approx 160mA\$

Therefore the quiescent voltage across R1 is approximately \$0.160 A * 470\Omega = 75.2V!\$ Clearly this is not possible, since the battery has only a voltage of 9V. So what is my error in understanding the biasing here?


texts: Explaining a car voltage regulator circuit

texts:
I need to come up with a solution for a voltage regulator to be used in a vehicle, regulating ~12V from the car battery to 5V used by Atmel AVR microcontroller.

I've found this schematic on the Internet:

While I understand the most part of how this circuit works, I have a few questions about it:

What's the purpose of R30 resistor on the input side?
Why are there two capacitors on each side of linear regulator LM7805? This answer to another question might be the answer I'm looking for, but I'm not sure about it. If this answer is related to my question and the use of two capacitors is to reduce resistance and inductance, why are such different capacitor ratings used (0.1 µF and 470 µF)?
Taking a single pair of capacitors, why is one of them polarized and the other one is not?
Are there any drawbacks if using capacitors with larger capacitance instead of those displayed on the schematic?
Are there any drawbacks if using capacitors with larger break-down voltage instead of those displayed on the schematic?

Thanks in advance.


texts: P-Channel Mosfet overvoltage protection using a TVS

texts:
I have a PCB layout that I need to modify in order to protect the mosfet from a transient voltage when the user connects the power supply. Occasionally the mosfet gets damaged due to transient voltages.  Will I be able to get away by just using a TVS diode connected from Source to Gate and without using a resistor on the Gate? The gate is directly connected to a via on the board and I cant mod it that easily.

simulate this circuit – Schematic created using CircuitLab


texts: Programmatically verifying EEPROM pins connected

texts: I can't find really much about it online, but am curious if there is any bit-fiddling like tricks to verify all pins on a EEPROM are properly soldered/connected (particularly address pins on a parallel chip).  I don't believe writing to a specific address and reading from the specific address would reveal any sort of error as within both functions a specific address pin would always be left low if disconnected (i.e. due to lack of solder, bridging, etc).  I looked through the EEPROM documentation and there is no special routine in the chip to pull all address bits high to then check them all... is there any other way to check programmatically?  Thanks.


texts: I have a PIC16F877A micro-controller. I need to interface a Bluetooth module with PIC. It will be connectted using UART Serial Communication. I have read the datasheet but couldn't find which exact module can be used with PIC.


texts:
This might not be a typical Stackoverflow question, but I wasn't sure where I could get this answered.

I have Verilog code to multiply two matrices and read them out, but my throughput is limited significantly by the number of I/O pins on the Xilinx Virtex 5 board (http://www.xilinx.com/support/documentation/boards_and_kits/ug347.pdf) we would be using. (I am designing on the Xilinx ISE)

How do I know which of the pins mentioned in the datasheet may be used as digital output pins? I've been through the datasheet several times, but I can't figure out which of the pins may be used for reading my matrices out (I estimated the number to be ~20-30, but not sure).

Thank you!

PS: I'd like to use every output pin I have, since we shan't be implementing on the board, but just calculating theoretical maximum throughput)


texts: Producing different types of tones using the 555 timer

texts:
I'm learning how to work with the 555 timer (astable mode) and decided to make a simple synth. The sound from a square wave is rather harsh so I'm trying understand how to modify it to make different types of tones. I'm a bit confused on how exactly to do this.

If I have the 555 timer running in the astable mode at a frequency of 136Hz and I want to produce a sine wave from its output, as far as I understood I need to 'bend' each HIGH from the 555's output with a capacitor and inductor, correct? I can easily find a matching capacitor using an oscilloscope to bend the HIGH signal like this:

but I don't understand how to calculate the inductor value so I can 'bend' the beginning of the HIGH signal as well to make it appear like a sine wave. How can I calculate the inductor value?

Is there a way I could modify each HIGH from the 555 timer in a 'linear' fashion to produce output/tone similar to this?

or is this achieved by merging different layers of tones into a single one?

What terms can I use to learn more on modifying the square wave in order to produce different types of tones? Thanks!


texts:
I have a question about interfacing IDT6116SA15TPG SRAM to a tri-state data bus controlled by 74LS244 tri-state buffer. I could not find an old memory like 74LS289 with separated inputs and outputs.

According to the memory datasheet, when the I/O pins are in the output state the input signals must not be applied. It seems like there is a possible situation, when memory and buffer are both in the output state for a short moment during the transition period (Read -> Write or Write -> Read).

One of the ways to solve this problem is adding a delay element (like 74LS31) and a logic gate to the circuit.

Is there a better solution (something like a special memory controller / bus buffer)?


texts: what would be the function of a resistor 36,000 ohms across leads on non polarized electrolytic capacitors in a roto phase phase converter

texts:
I have a surface grinder (3 phase) and believe that some of the capacitors are shot
in my phase converter due to a lack of available surge power. The grinder starts and works ok but the circuit board for reversing the carriage shows an error(Red LED lit) intermittently and carriage does not reverse direction. Could be lots of things.(Already replaced circuit board and worked fine at first then similar problem of carriage reversing direction happened again. I can get it going if I push
it so I am thinking  because the converter is old and the capacitors don't cost too much I would replace them. However some the wire leads are soldered directly to the capacitor leads, and 2 of them have resistors soldered across the leads. Why are they there.


texts: Dimmer effect (fade) on 12v LED using transistor and Arduino

texts:
I am working on a project on which I want to control the brightness of a 12v LED using a transistor and an Arduino board. So far I have used the 2N3906 resistor connecting the collector to the 12v Power supply, the base to the PWM of the Arduino (in which I am using the "Fade" example where it increases and decreases the value indefinitely) and the emitter to a resistor followed by the LED. As a result, the LED was lit on a very low voltage which was received ONLY from the PWM of the Arduino. I have also used a BC327 transistor connecting the collector to the 12v Power supply, the base to the PWM of the Arduino and the emitter to the LED. On this result, the LED was lit brighter than the previous but not on as much as it should.

My question is, am I doing something wrong? Are the transistors that I used not capable of performing this job? What should I do for the LED to be lit on maximum and control its brightness via the value of the PWM of the Arduino?

The PWM voltage of the Arduino is 5v.

Feedback to your answers:
I have ordered each sensor that each one suggested and I will try out your solutions. Once I am done, I will let you know about the results.


texts: Understanding The Art of Electronics mathematical explanation for capacitors

texts:
The author mentions that the reader should not worry if they cannot keep up with the mathematics, I however feel uncomfortable doing so. The issue is the fact that the author does not explain what the mathematical variables are for so I would like someone who understood it to clarify. The give the following circuit

simulate this circuit – Schematic created using CircuitLab

It mentions that at time = 0 the equation for the current is
$$ I = C{dv\over{dt}} = {V_i - V \over {R}}$$
The author does not specify what Vi or V are. However, I can conclude that you would need to subtract the voltage supplied by the battery by the voltage of the capacitor. Vi is the source voltage, V is the voltage on capacitor. Afterwards they define the V (capacitor voltage) as  $$V=V_i+Ae^{-t\over{RC}}$$ What confused me here is what the term Vi was doing in the expression for the initial voltage across the capacitor or does Vi stand for something else? also what does A signify? As the author then states that A is determined by initial conditions V=0 ,t=0. A will be equal to -Vi so then $$I={V_i -(V_i + (-V_i * e^{-t/RC})\over{R}} = {V_i * -e^{-t/RC}\over{R}}$$ at this point I have lost track of the intuition behind it and if someone could walk me through what the author means, or really just the intuition behind the mathematics I would appreciate it.


texts: Sound generator: 14500Hz frequenzy (required), 90db (required), should run ~24days on battery (if reasonable)

texts:
I am looking to build the following thing:

Sound generator: 14500 Hz frequency (required), 95 dB measured at source (required), should run ~24 days on battery (if reasonable).

There are two major phases:

Prototype: Needs to be easy enough for an non electronic guy like me to build. I have seen videos on the 555 chip, some calculations.
Series: If the prototype is conclusive I might first build a series of 50 and then several 10000.

I have read that differences of sin and square waves are marginal in tone output if the frequency is >10 kHz. How much is marginal on a frequency at 14500 Hz.

Currently I hope to have max change of frequency ±200 Hz as an output.

I am looking for ideas:

What would be the most reasonable circuit to build to generate this frequency. (est. material cost?)
How can I select the best speaker for this application (very economic, low energy consumption, ..?)


texts: Pat testing alliances with DC DC converters in them

texts:
For example a digital radio or a laptop, these sorts of applicances all work on dc. They a switch mode power supply which turns low voltage into extra low voltage.

So essentially it's selv right,

So my question is do testers actually test the appliance itself at 250? I assume they flash test the power cord at 500v. Similar to the insulation resistance test a electrician would do on a fixed installation I.e. a house.
Yes?


texts:
About a week ago, I have been soldering exactly 29 LEDs to a PCB in an effort to replace my old, custom taillight bulb that came with my motorbike since I bought it. I have successfully managed to solder the LEDs onto the board and I already did the wiring. Since I bought my LEDs on an electronic market, and they did not come in a package, I have no idea exactly how much voltage they need nor how much AMPS they require. Since then I have been trying to hook them up to multiple voltages including 3v, 6v 12v(which will be the voltage used by my bike.) I have also been researching about my issue and believe that my problem has to do with some form of resistor I will be needing.

I look forward for a good solution!


texts: I have lots of these connectors in my MT765.  The dealer only sells full harnesses with this as part of it.  I want to buy a bunch that I can crimp myself (of both male and female parts).  How can I identify the connector so that I can find some?


texts:
Another question yet again.

I am having troubles trying to use the DAC on the STLM32L432KC chip. Using PA_4 pin which only has DAC1 (Channel 1.) When I probe the pin nothing appears on it.

Pinout
STMLM32L432KC Datasheet

Is there something that I over looked?

The code:

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  *
&copy; Copyright (c) 2020 STMicroelectronics.
  * All rights reserved.

  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include <string.h>
#include <stdio.h>
#include "custom.h"
char buffer[80];
int adcValue = 0;
int counter = 0;

void ADC1_IRQHandler(void){

    if (((ADC1->ISR) & (1<<2)) != 0){
        adcValue = ADC1->DR;
        DAC1->DHR12R1 = adcValue;
        printADC(DAC1->DHR12R1);
        ADC1->ISR |= (1<<2);
    }
}

int main(void)
{

    initDebug();
    initADC();
    initDAC();

  while (1)
  {

  }

}

void printADC(int adcValue){

    sprintf(buffer, "ADC Value: [%d]\n\r",adcValue);
    for (int i = 0; i < strlen(buffer); i++){
         USART2->TDR = buffer[i]; //Put data in the Transmitter reg
         while(((USART2->ISR) & (1<<7)) == 0); //Wait till transmitter reg is empty
    }

}

void initDebug(){

    RCC->APB1ENR1 |= (1<<17); // Enable USART2 Clock
    RCC->AHB2ENR |= (1<<0); //Enable GPIOA Clock
    RCC->CCIPR = (1<<2); //Use the System Clock for USART2

    GPIOA->MODER &= ~(1<<4); //Enable Alt Function for PA_2
    GPIOA->MODER |= (1<<5);
    GPIOA->AFR[0] |= ((1<<10) | (1<<9) | (1<<8)); //Enable USART2_Tx for PA_2

    USART2->CR1 |= (1<<3); //Enable Transmitter
    USART2->BRR = 0x1A0; //9600 baudrate
    USART2->CR1 |= (1<<0); //Enable USART2

}

void initADC(){

    RCC->AHB2ENR |= ((1<<0) | (1<<13)); //Enable GPIOA Clock & ADC Clock
    RCC->CCIPR |= ((1<<29) | (1<<28)); //Uses System Clock for ADC

    GPIOA->MODER |= ((1<<15) | (1<<14)); //Enable Analog Mode for PA_7

    ADC1->CR &= ~(1<<29); //Disable Deep power ode
    ADC1->CR |= (1<<28); //Enable Voltage Regulator
    for (int i = 0; i < 100; i++){
        counter += 1;
    }
    counter = 0;
    ADC1->CFGR |= (1<<13);
    ADC1->CR |= (1<<31); //Start Calbi
    while(((ADC1->CR) & (1<<31)) != 0);

    ADC1->IER |= (1<<2);
    NVIC_EnableIRQ(ADC1_IRQn);
    NVIC_SetPriority(ADC1_IRQn,0);
    ADC1->SQR1 |= ((1<<9) | (1<<8));
    ADC1->ISR |= (1<<0);
    ADC1->CR |= (1<<0);
    while(((ADC1->ISR) & (1<<0)) == 0);
    ADC1->ISR |= (1<<0);
    ADC1->CR |= (1<<2);
}

void initDAC(){

    RCC->APB1ENR1 |= (1<<29); // Enable Dac
    RCC->AHB2ENR |= (1<<0);
    GPIOA->MODER |= ((1<<9) | (1<<8));
    DAC1->MCR |= ((1<<1) | (1<<0));
    DAC1->CR |= (1<<0);
    for (int i = 0; i < 100; i++){
        counter += 1;
    }
    counter = 0;
}


texts:
Many times I want my computer to interface old hardware. Such as radio, light switch, etc. This mostly involves pushing pressing and moving various buttons and switches.

I don't want to buy new hardware I want my computer to interface the old hardware I already have.

I thought about it and reached to the conclusion that what I need is a general purpose button-pusher hardware.

I need a simple device I can interface by a computer and would be able to push most of the buttons we have in daily accessories, without damaging the button.

Is there any such accessory availible?

(migrated from superuser, where I got no satisfactory answers).


texts: Where to find ARM CortexM complete register list and description? ie. for stm32f746

texts: I'm new to ARM microcontrollers and currently learning from the book "The designer's guide to cortex-M Family" by Trevor Martin. One of the odd things I've found is that I can't find many of the register's description such as SCB, PRIGROUP and many others on my device's datamanual or datasheet, but are present on my project libraries such as stm32f10x.h or core_cm3.h . Where I can find a complete source for registers? I tried http://infocenter.arm.com but it lacks the integrity of a manual and is more of a look up table and also I don't know what am I missing.


texts:
How would one design an actuator with the following requirements:

The actuator is completely isolated with no electrical contacts.  Imagine a rotor encapsulated in sealed plastic cylinder. The rotor is rotated by say 45 degrees to lock / unlock a system.

The rotor is designed so that it cannot be rotated unless inductively energized thus becoming magnetic.  The rotor has to be non-ferrous and non-magnetic.

As an example only I picture an impeller from a water pump but with the magnetic charge of the rotor being from induced current instead of a permanent magnet.

For the use case, the stator is removable.  Once removed the encapsulated rotor must not be able to be rotated by a permanent magnet
{without adding some sort of braking or locking mechanism.}

Clarification: I can't explain the application explicitly.  The rotor will acting as a lock mechanism.  Unpowered it would be locked from sliding up.  Once powered to rotate out of the locked position let's say 45 degrees, it would be free to slide up.

Induction Solenoid:

Alternatively, a similar concept but instead an induction solenoid.  One that could not be actuated by a permanent magnet.  Unpowered it's held in home position with a spring and only moves when powered.

Non-ferrous? Material is unimportant as long as it can't be actuated externally with a magnet.


texts:
I would like to make a simple 2 axis CNC machine to create gears.  One stepper motor could spin the gear, and the other could move a drill bit in a single axis.  On ebay, I can find double h bridge controllers for less than $10.  For example: http://imgur.com/XBEww

Now, if I were to buy two of these, and two stepper motors, and a power supply, is this all that's necessary (electric wise) to build a gear maker?  I already have an arduino and a computer.   For the power supply, can I just use a simple power supply that turns a home power supply into something that looks like my car's cigarette lighter?


texts: Should a six wire stepper motor not have two coils that are separate from each other?

texts:
My understanding is that a six wire stepper motor contains two coils. Both of these coils are separate from each other, meaning that the impedance between any two wires, one from each coil will be infinite.

When I took impedance measurements on a stepper motor that I salvaged -- I got the following readings, all in Ohms.

Would any help at understanding what I'm looking at.


texts: Optical perpendicular speed sensor required

texts:
I've been looking to this for a while now, and so far I can't find what I need. But I'm think I'm missing the right search terms for it..

I've got a little project in mind where I can measure the speed of a conveyor belt. I'd like to do this by having an arduino sized box with the sensor inside. You could hold it on the belt and measure the speed, showing this on a few 7 segment displays or LCD display. How I'd like to do this is by using a system like an optical mouse, and from my understanding they have a module inside that compares low res pictures that compares how much the mouse has moved. This way I can keep my system a bit airtight instead of a wheel of some sort, and it looks fancy.

Does someone know what I should be looking for?

EDIT1: It has to calculate m/s, with 1, maybe 2 decimal numbers. I can't place extra detection stuff on the belt(s). It has to be one handheld device that can measure it all in a few seconds.


texts: Are multiple reflections accounted for in S-parameters?

texts:
When the S-parameters of a 2-port device whose input and output impedance are different from 50 Ohm are calculated/measured in a 50-Ohm system, multiple reflections occur at port 1 and port 2.
Let's take the example of calculating/measuring S11:
When injecting a signal into port 1, part of it is reflected at the generator-port1 interface and the rest travels to port 2 where part of it is reflected at the port 2 load interface.
This partial reflection travels back, part of it goes into the generator impedance, the rest is re-reflected towards port 2, etc.
Is it correct to say that all these waves reflected back into the generator are summed up and therefore accounted for in the calculation/measurement of S11?


texts: How do phones charge their battery at seemingly any rate with no issues? 500mA or 1A or 1.2A depending on the charger?

texts:
If most use some sort of li-ion battery, and those batteries like to be charged in CCCV format how can my phone charge just fine at 5V, 500mA or 5V, 1A or 5V, 1.2A just fine (actual current delivered, not power supply capabilities)? It seems the current is not constant. If I made a 5V, 1A battery charger it is recommended to not use a 5V, 0.5A supply since the charger was designed for 1A.

Do phones just have really complicated charging circuitry that differs from the standard li-ion charging ICs? Everyone can either charge their phone with USB at 500mA or use a wall adaptor for a faster rate.


texts: Battery gauge – Microcontroller 3.3V using a 4.8V NiMh battery source

texts:
Well I am currently working on building a battery gauge via LED. My target is a red LED to blink
if batteries  are going to die and a green LED to blink if the batteries are fine.

Researching on  that topic  different questions already have been considered and mostly referred to  a link such as
http://batteryuniversity.com/learn/article/how_to_measure_state_of_charge.
Knowing the limitations I was planning to make use of the Voltage Method.
The batteries I was planning to use were NiMh enveloop pro batteries (AA).
Considering the tests on the battery (I couldn’t find the datasheet)
 the http://www.stefanv.com/electronics/sanyo_eneloop.html
I found out that the battery mostly crosses below 1,1V before dying. Therefore I was planning to use 1.1V per Battery as a threshold or indication that the battery will die.
To apply the voltage method beneficially, using the internal  1.1V reference voltage of the Adafruit Trinket Pro (according to the datasheet of atmega 328p, which can be found in the Trinket) has to be measured against the input voltage(as described :http://wp.josh.com/2014/11/06/battery-fuel-guage-with-zero-parts-and-zero-pins-on-avr/).

However my issue is that I make use of an Adafruit Trinket Pro 3V and a Servo having one source of battery (4XAA NiMh).
4.8V are provided to the Servo. A buck converter is attached  between the battery and the Trinket in order to provide it with its required 3.3V.

Generally using the Voltage method for a battery gauge the ADC Pin is compared to Vcc Pin as described above.
 However in my case the microcontroller will always receive 3.3V. Any voltage drop of the battery will only affect the servo since the buck converter will make sure to provide the microcontroller with sufficient voltage.
Therefore using the voltage method I do not know how I may identify any voltage drop on the 4.8V battery source because the voltage drop will have no effect on the Adafruit Trinket.

Given these circumstances is there a way to make a battery gauge making use of the voltage method or any other beneficial way? I am aware that the difference in VBAT and VCC might complicate the issue..

Information Adafruit trinket: https://learn.adafruit.com/introducing-pro-trinket/overview
Datasheet atmega 328p: http://www.adafruit.com/datasheets/ATMEGA328P.pdf


texts:
I want to buy connectors which are generally at the input of speakers or amps. I have attached a picture below.

What are these plugs called? I cannot find these on Digikey.
Thank you for your help?


texts: Overhead transmission line crossing over interstate highway

texts:
I live in Minnesota, and a few years back, Excel Energy constructed a massive power line stretching from Monticello, MN to Fargo, ND.

This is not the exact photo of the power lines, but it's very similar in design:

The power line is wired on only one side of the tower for the entire trip of the line. The only exception is when the power line crosses Highway 94, both sides are wired. Once the line has crossed over the highway, it continues on only one side. The line crosses several times for the length of the trip (approximately 200 mi,) each time, both sides coupled.

My question is, what is the purpose of having both sides of the tower completely wired when crossing the interstate when only one side is clearly being used? Are these "extra lines" underground cables that need to be crossed overhead?


texts:
Im planning on building a E-Bike and have made some calculations and only need my 190rpm/V brushless motor to spin around 600 rpm to give me a good speed.

So by this calculation I only need to supply 3.x V.

As I understand it without load the motor will rev up to 600 rpm, but on a bike there will be a pretty big load and high current will be required.

Now because many components doesnt like too much current is it better to have higher voltage so I get more W from V and not as much from A?


texts: Should I use all the pins from 1 Port or few from each available (STM32)?

texts:
I am using a MCU from the ST, specifically from the STM32L1xx series. I want to connect 2 sensors, both of which will use the I2C protocol, 1 MicroSD card with SPI and 4 Interrupts. Is it a good practice to use as many pins from one port (for example from PORTA) as possible or to use every available port? Some pins connected to PORTA, some to PORTB etc.

Thank you for your time


texts: Node Voltage Problem, possible to simplify?

texts:
I have a circuit here which has to be solved using only direct input into a matrix using the node voltage method.

Here is my attempt to solve it, the blue lines separate each matrix entry. I am wondering if there is a better way to solve it, or if I made a mistake or anything. I don't believe I did it correctly largely because of the \$3V_1\$ in term \$b_{33}\$ of the matrix.


texts:
I witnessed an experiment in which a transistor was connected to an led and a power supply.

A lighter was used to heat up the transistor and this reduced the resistance of the circuit and made the led light up brightly.

Why does heating the transistor do this ?

And if this works with a transistor then why is  a thermistor needed ?


texts: What is this symbol? (assumed compliance mark like CE / FCC)

texts:
So Raspberry Pi have a new model out (the Raspberry Pi Zero W). Having taken a look at the photos, I see that on the reverse, where the CE and FCC compliance marks are shown, there is another symbol. It's hard to describe - something like a "T" with a parallel bar over the top enclosed by a three-quarter circle and a horizontal lightning bolt above the "T" but inside the partial circle.

Here's a picture:

and a close-up:

Does anyone know what this symbol represents? My guess would be another compliance mark.


texts: rf range at 433Mhz with prototype stripboard

texts:
I have a pair of RF IC's, wired with capacitors and coils as suggested by the manufacturer, on a prototype vero-board. (see pictures).
These are an OOK 433MHz transmiter CMT2150 and a receiver CMT2250 by the chineese rf manufacturer COMSTEK.
I made them working but at less than 3 meters distance.
Should I proceed with pcb prototyping/manufacturing hoping that the properly made pcb will improve the range to 20 meters (line of sight) which is the requirement ?
Should I try external LNA ?


texts: Two simulations are different. Mine V.S. Paper's

texts:
Paper Link : http://rincon-mora.gatech.edu/publicat/cnfs/new16_pzdamp.pdf

After reading the Fig3 (Asymmetrically pre-damped piezoelectric charger),explanation of its process,i make a schematic(a.) and simulate(c.).However,my simulation and its simulation(d.) are different,i think the time of my switch close or open are right.so i can't find the place i do wrong.

From the first picture,you can find that i use a "vsin" instead of "isin" or "cccs/vccs",this is because i saw a unload wave from another paper,and the PZT output voltage is a sine wave.

Can anyone guess or know where am i wrong?

\$V_{CAP}\$=\$V_{PZ}\$,1 means connect and 0 means disconnect for two switch signal

(a)

(b)

(c)

(d)


texts: I am miscalculating the Asymptotic Bode Plot

texts:
hope you are all doing well. Right now I am dealing with a homework and I have transfer function and I need to plot the asymptotic Bode Plots of it. I am trying to plot the Magnitude Diagram right now, and I am misevaluating the Magnitude at Low Frequencies. I calculate it as approximately 15dB, whereas MATLAB shows it 35 dB. Here is what I did:

The original question:

What am I missing? I am pretty ill right now, so I am probably missing out a detail, even though I checked it multiple times.


texts: Simple AC line state detection for digital controller input

texts:
Last year I moved into a house that has an old ('50s-'70s vintage) GE low voltage lighting control system.  It uses 24VAC momentary wall switches to toggle solenoid/latch relays that feed 12 main lighting power runs.  I want to do some computerized home automation using this system and most likely something like a Phidgets digital I/O controller.

Controlling the lights should be easy.  I just need to piggyback momentary circuit closures in parallel with the existing switches.  This should be easily achieved with a digital output controller.  Although, the Phidget board I'm looking at says it can control "up to 30VDC" so this might be a problem since I need to switch an existing 24VAC signal.

I also want to be able to detect the state of the main lines to know (in software) what circuits are live.  The simple answer is to put a relay in parallel with the main load.  I can wire in the digital I/O controller to the switched poles which then tells the software the state of things.  The problem I'm having is finding appropriate (e.g. low load/cost) relays that work with a 120VAC coil voltage.  There are plenty of heavy duty industrial relays, but those are far beyond the needs (and, more importantly, cost) of my application.  The switched side needs to handle only a very low DC voltage supplied by the I/O controller.

I'd settle for a mechanical relay if that's what it comes down to.  (Also still looking for a suitable candidate in that area.)  But I'd like to avoid having a bank of 36 mechanical relays just to translate the 120VAC input signal and 24VAC output signals to/from the controller's DC input/output.  However, my research so far is suggesting that might be the only way.

I've been searching various suppliers catalogs for solid state relays that will do this, but no luck so far.

I've also thought about using analog I/O controllers with voltage sensors, but that seems excessive/unnecessary and I haven't found a cost effective solution there either.

Can anyone recommend a relay product for this solution?

Or does anyone have another suggestion to this problem?

Update: Change link to a GE document that somewhat represents the system I have.  Document includes schematics of the relays and other parts.


texts:
Duplicate of https://raspberrypi.stackexchange.com/questions/91781/dht22-bad-readings-on-long-cable, I figured there is chances people here have a solution for me.

Hi,

I'm preparing a setup with a long wire separating the sensors and the rpi. Wire is a cat6 RJ45 (ethernet) cable of 100ft (30m), that i'm using 6/8 wires. I randomly choose the wires, I figured as long as I take the same one at the other end, it should work. And it does, for the most part.

I've drawn my wiring to fitzing to explain it. See below. Some notes to take into consideration:

For the RJ45 in the drawing, assume the white wire is partially colored of the closest wire on it's left. For exemple, the first wire is orange, and the second one is white-orange.
For the resistor, horizontal ones are 10k and vertical ones are 1k.
white-green and white-blue are not used, so i merged them on one end and put them to GND on the other end. Before doing that, I had interference between IRLed and button switches

DHT22 readings are done in python, every minutes, using Adafruit_Python_DHT 1.4.0.
Exact code for DHT22 in this public repo: https://github.com/Ericmas001/hq-dht22-reader-docker/blob/master/exec/hq_dht22_reader.py

My problem is:
DHT22 readings are 99% wrong. I'm reading 10.3°C (50°F) and 3288.7% humidity most of the time. Correct readings would be around 24°C (75°F) and 21% humidity. Funny enough, I get correct reading somethign like twice an hour.

Currently, it's a 100ft (30m) cable but it's only as a proof of concept, PI and sensors are really no more then 10ft (3m) appart.

I've tried switching wires (to rule out that the problem was bad wiring within the RJ45) but result is always the same.

I've also tried using a 10ft (3m) jumper wire for the yellow wire (bypassing RJ45) and then, everything works fine.

So the problem seems to be because of the length of the wire.

I've done some research, and found out that there was similar problems for other people with the library

https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/issues/49
https://github.com/adafruit/Adafruit_Python_DHT/pull/6

Unfortunately, those problem have all been resolved with recent 1.4.0 release, that I happen to be using in my setup.

Does somebody knows how to resolve my issue. ?

Also, you can assume this:

Electric & electronic knowledge are very limited on my part. I'm learning using the internet and doing this as a hobby.
I would prefer if solution is on the pi-side of the RJ45, since the sensor-side would be in the wall
For the proof of concept, RJ45 and jumperwire are twisted together with wire caps.

Thanks, have a nice day !


texts:
I am currently working on a low power battery backed data logger.
An Intersil ICL7673 backup switch is used to switch between the battery and external power.
Because the circuit draws more than 30mA I have to use two mosfets (instead of transistors) as suggested in the datasheet:

simulate this circuit – Schematic created using CircuitLab

One of the problems I ran into is that the mosfets let current flow into both directions. This makes it difficult to check if the supply is turned on. Two addional diodes could be a solution for this, but do I even need the intersil backup switch then? Wouldn't a simple diode-or be a more efficient solution?

Because the battery input already has a diode I am thinking about just putting another diode in series with the power supply. That would make the whole circuit cheaper and consume less power.

EDIT:
Just for clarification: The circuit draws a bit more than 30mA once every few minutes for a few milliseconds. The rest of the time it will be at under 100uA. I tried the setup with resistors as described in the datasheet but it seemed to draw around 500uA (not mA, sorry for confusing that in my first comment). If I am using a 10k and 1k resistor souldn't that alone use around 0.3mA?

simulate this circuit

EDIT 2: After trying the solution with two mosfets, I took out the ICL7673 and put a schottky diode between power supply and vcc. It works perfectly. As long as the supply voltage is greater than the battery voltage, the circuit will only draw current from the power supply. On the battery side I needed a diode for polarity protection anyway, so the voltage drop is unavoidable.

simulate this circuit


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The STM32F427 is powered by 3.3V but many of it's pins are 5V tolerant. This allows external chips to drive it's logic I/O pins at 5V without damaging the device.

I have a board design with at STM32F427 that operates off of two voltage supplies: 3.3V and 5V. The 3.3V regulator is daisy chained off of the 5V regulator which means that the 5V logic comes up before the processor. I currently have a dual-supply buffer (TXS0108E) between the 5V logic ICs and the processor to prevent the processor pins being driven before power is applied.

Is this protection necessary? Can I safely remove the buffer to reduce the complexity? I don't see a lot in the reference manual about power supply sequencing.


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I intend to use an Arduino.

If the resolution is not good enough for the Arduino analog input pin (A0) Arduino Tutorial then I want to use a ADS1115 Datasheet.
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What is the thermal steady state analysis and Transient analysis?
Which state gives the temperature rise in the busbar exactly after 1 hour charge/discharge?
In general what is the state used in thermal simulation of busbars?
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