texts:
UPDATE
After reading comments, I realize that I need to ask better questions. Here is a more explicit question. Ignore the original, which is below for reference.

I am driving an LED. The idea is to change the supply of the LED so that I can make the output of LED modulated at my supply frequency. LED is tied to a transistor which is essentially a switch, when I want output, I use GPIO to turn on a simple transistor and current starts to flow. The issue is that I want to sense when I turn on this LED from far far away where the SNR is real issue. So, my idea is to add modulation to my LED output. So when I turn on the LED it will essentially emit a modulated signal (hopefully 10MHz, previous 1MHz was a mistake). The idea is to modulate the voltage supply of the LED and when I turn on the LED using GPIO, the current across the LED modulates at my desired frequency. I will choose the DC and AC components such that the LED will be on but its intensity will change with frequency.

The idea is to implement a lock in amplifier at the receiver for 10Mhz and sense 1 vs. 0 at much lower signal levels.

My current requirement is 50mA max. The 10MHz AC over DC must be stable as I turn on or off the LED, I don't want to loose the 10MHz or wait for it to stabilize for a long time, so the source should tolerate load changes and respond fairly fast.  (preferably <50nSec)

UPDATE 2
FYI. The application is not data transmission, I just need to recognize the presence of the signal. I control both transmitter and receiver. The signal is on only for 1uSec at a time, with frequency between 100Khz to 1MHz. I unfortunately cannot change this 1usec hard requirement or use a fixed frequency. So, I need to see the signal at that 1uSec. The idea I have is to make that 1uSec a modulated signal so that I can tune into the modulation of that signal during that 1uSec.

BTW, the system currently works without this type of modulation but not in every situation (too much interference, imperfect alignment of the receiver etc) due to low SNR. All I want to is to modify transceiver and receiver circuits to increase the SNR and this is what I can think of. I considered several other options but since my transmitter frequency is not fixed, it is difficult to use narrowband filters etc to reduce the overall noise. Having a HF modulation during the short burst of transmission would allow me to have a lock in amplifier. Essentially, I am trying to cheat by embedding a high fixed frequency signal on to a Lower Frequency signal that is not fixed frequency and look for the HF to see the presence of LF signal. As I indicated, LF in this case is not fixed frequency, could be as low as 100Khz or as high as 1MHz.

ORIGINAL QUESTION
I have a 5V DC. I like to generate 3VDC, 1V AC (2-4V) from this 5V. AC frequency I am targeting is 1MHz. This AC needs to stabilize very very fast, hopefully less than 50nSec. I have a CPU on board, so if I must, I can provide a clock input, it can be anything since I can program the timers of the CPU. (I prefer a pure hardware solution though).

Solution needs to be design time tunable, I may have to change the frequency.


texts: Can I Use a Transformer to feed a Mains current to a RPI GPIO pin

texts:
I have a standard mains (240v) motion detector that activates an outdoors lamp. I want to notify my Raspberry Pi when the lamp is activated.

My plan is to use a 240v to 3.3v transformer that I have already purchased. I intend to wire the transformer in parallel to the feed wire of the lamp so that when the lamp is activated, so too is the transformer and thus the GPIO pin can get its 3.3v activation signal. The transformer output is specified at 3.3V dc 1A 3W (Hi-Link HLK-PM03). I read that you should never source or sink more than 0.5 mA into an input pin.

Is it safe for me to connect this transformer directly to the GPIO pin or do I need to add a resistor or do something to limit the power from the transformer?


texts:
I'd like to use atmega328p to read force with strain gauge. I'm using one 1k strain gauge and 3x 1k ohms dummy resistors.

My circuit looks like that:

I'm using DAC to remove offset from bridge.

As a result I'm getting so much noise on atmega pin.

It looks like that:
1) No averaging (It's like only 0's and 1023's):

2) 30 readings running average:

I've tried changing R4 to 2,4k, 3k and 10k ohms. 2,4k and 3k helped just a little bit, but while using 10k output of ad8237 goes to 0 in a few seconds.
I've removed C11 - nothing better happened.

AVCC is 3.3V with 10uH inducto in series. It's used to power strain geuge bridge, AD8237, DAC, atmega328p analog VCC.

Atmega328p AVCC and AREF are decoupled with 0.1uF capacitors.

Aver unues atmega pin is set as LOW output.

Is there any way I could remove that noise?

@EDIT

Everything solved by removing C23, thank You @EinarA

Now different problem is noise when touching sensor body.
On the photo:
lower amplitude - sensor lying on its own,
higher amplitude - im touching sensor body with one finger.
That's not big difference but it is.
Sensor body is made od 1.4301 steel.
Sensor body is not grounded. Is it a good idea to connect cable shield to body or just ground body?
Cable shield is connected to ground on just pcb side.


texts: A simple RL circuit, getting transfer function, matching with results

texts:
I'm doing  little lab exercise with an RL circuit. I need to check if I did this analysis right, because the numbers I got and the numbers that should theoretically be there are so far off, I figured I had to be doing something wrong.

We have the following circuit:

simulate this circuit – Schematic created using CircuitLab

And we want to measure the voltage across AB and build a bode plot, and ID what kind of filter it is.

So I get a bunch of values for the voltage. No problem, I plot them and the shape looks like a good Bode plot. I even marked the cutoff frequency and it looked like it was in the right place.

But when I tried deriving a theoretical Bode plot the curve always looked off -- way off. It was either too far to the right (the inflection point was off by orders of magnitude) or too high or too low. So I want to make sure I derived the response function correctly. If yes, then fine; I can say that it's off because the resistor and inductor aren't perfect. (One would expect that). But I am really struggling here.

So, here's what I did: the response function on this circuit will be
$$H(\omega)=\frac{V_{out}}{V_{in}}$$

\$V_{in}\$ is easy enough since I set the RMS at 1 V. But mathematically it should be (Ohm's law) V=IR and the total impedance of the circuit at a given frequency (using f not omega) is \$R+ i\frac{f}{2\pi}L)\$. That means \$I = \frac{V_{in}}{R+ i\frac{f}{2\pi}L}=\frac{2\pi V_{in}}{2\pi R+ ifL}\$. That should mean that
 $$V_{out} = V_{AB} = \frac{V_{in}fL}{2\pi R+ ifL}$$
and my response function is $$H(f) = \frac{fL}{2\pi R+ ifL}$$

I need to convert this to a real number and a magnitude, so I did this:

$$|H(f)|^2 = \frac{(fL)^2}{(2\pi R+ ifL)(2\pi R- ifL)}=\frac{(fL)^2}{(2\pi R)^2+ (fL)^2}\rightarrow |H(f)| = \frac{(fL)}{\sqrt{(2\pi R)^2+ (fL)^2}}$$

But this does not produce anything like the values I got. The Bode plot goes up to a certain value and flattens out, as though this were a low pass and not a high pass filter.

Now, if I were using just R in the numerator of my transfer function it looks the right shape, but not in the right place.

Her'es the values in millivolts I got for \$V_{AB}\$ at various multiples of fc (cutoff frequency) in Hz. Fc = 4289 Hz.

428.9: 68.3

2144.5:  64.8

4289:   52.6

8578:   34.7

17156:  1.2

Anyhow I am just trying to suss out what I did wrong here, if anything.


texts: How to analyze this MOSFET H-bridge circuit?

texts:
In my university electronics course project, I am asked to analyze an H-bridge circuit.  It is a simple H-bridge in which the motor is represented with a 37 ohm resistor and thus has no diodes.

The circuit in the image is a particular equivalent for an H-bridge circuit;
I got this circuit once I determined the gate voltage of each of the four MOSFETs, and found which MOSFETs are ON and which are OFF. After that, I determined the current path which gave me this equivalent circuit.
Given that:

the current passing the PMOS equals the current passing the NMOS
we can apply Ohm's law on the resistor
the MOSFETs are essentially being used as switches, so they are in Triode mode
channel length modulation is neglected
for NMOS \$I_D = kn[V_DS(V_OV) - \frac{V_DS^2}{2}]\$
\$|V_tn| = |V_tp| = 3V\$

Through my analysis, I got three equations with three unknowns given:
\$-0.05(V_Dp)^2 + 0.3V_Dp - I_D = 0.112\$
\$-0.05 (V_Dn)^2 + 0.6V_Dn - I_D = 0\$
\$V_Dp - V_Dn = 37I_D\$
I then tried to plug the third equation into the first two, and I got:
\$V_Dn = 1.85(V_Dp)^2 - 10.1V_Dp + 4.144\$
\$V_Dp = -1.85(V_Dn)^2 + 23.2V_Dn\$
How can I solve it from here? Is my methodology right?


texts: What transaction modeling and packet linking frameworks exist?

texts:
We're looking into modeling and checking a simple mesh fabric coherency protocol for checking RTL simulation. In the past, we've completely rolled our own solution for listening to packets in the RTL and then generating an expected response or multiple possible expected responses.

e.g. for a flow like this:

 Core                  Memory Controller
   |                          |
   | Request $Line in E-state |
   +------------------------->|
   |                          |
   |              Data        |
   <--------------------------|
   |                          |

The checker on the Memory Controller needs to predict that the Data packet will be returned to the Core and what the payload of that packet would be.

What are the available frameworks for modeling these flows?  I'm aware of TLM and am looking into it.  Are there any others?  I'm open to any language.  Are there any formal verification protocol tools that can also generate checkers or assertions?


texts: How to match this gate driver to this mosfet?

texts:
I've selected this MOSFET for a motor control application [picture attached]: IRF200P222
Datasheet: https://www.infineon.com/dgdl/Infineon-IRF200P222-DS-v01_02-EN.pdf?fileId=5546d4625b3ca4ec015b3e42ba4a0744

I'm going to use low side configuration. I've chosen the 1EDN751x gate driver which has two possible ways of using it. I attach them. What is the best way to use it? And how can I compute a proper gate resistor? The gate driver power supply is 12V. The dc link voltage is about 150VDC.

Datasheet: https://www.infineon.com/dgdl/Infineon-1EDN751x_1EDN851x_Rev%202.0-DS-v02_01-EN.pdf?fileId=5546d462576f34750157e176df0b3ca7


texts: Difference between Logic Chip and Memory Chip front-end manufacturing process?

texts: I understand that memory chips like DRAM Chips require a little different set of Front-end setup than logics chips. However, I am not finding anywhere how the actual manufacturing steps differ, especially the front-end manufacturing process. I'm trying to understand if a Fab is set to manufacture processors can it be reconfigured to make memory chips without lets say "equipment layout change"?


texts: Implement BGEZAL instruction-MIPS-32 in verilog

texts:
I want to implement MIPS-32 Single cycle microarchitecture using Verilog. I have few doubts regarding the instruction BGEZAL.

It does GPR[31] = PC + 8.

The BGEZAL instruction format is

The bits from 16 to 20 are given to register file. It is 10001 which is decimal 17. But the description of BGEZAL says it writes to register 31. Should the values Intruction[20:16] not be 11111? So PC+8 must be written to GPR[17] or GPR[31] ?
And also, the instruction does PC + 8, but PC is not given as input to ALU in this lecture notes. So I have planned to have a MUX in the first input (upper input) of ALU. If the instruction is BGEZAL, the MUX will feed PC else, it will feed data1 from register_file. Is this fine?


texts: How can I protect a 12VDC power source from high-resistance shorts?

texts:
I have a pickup truck with a 3kw AIMS inverter-charger. It is wired with 4/0 welding cable (for both positive and dedicated neutral back to the alternator), and I installed a block with a 300A fuse in the engine bay as close to the alternator as possible. My concern is that most of the conceivable events causing a short circuit would have a current path with resistance such that the short would be much less than 300A and therefore not blow the fuse.

What is the recommended practice for wiring such systems? I did a search for "DC ground fault protection" but none of the products that came up appeared to be appropriate for my application. If a 300A 12VDC GFCI device was available I would gladly purchase it. Thanks in advance.

Edit: I am talking about a live-to-ground short, not live-to-neutral. Suppose the insulation surrounding the live wire to the inverter (which is routed along the truck's frame) is somehow sliced open and the bare wire makes a weak short against the frame. This is the event I want to be protected from. To be clear, answers pertaining to the physical protection of the live wire are not appropriate here; I have already taken steps to make sure it is as far out of harm's way as possible.

Edit 2: These are the events I foresee possibly occurring as a result of a live-to-ground short (and want to prevent):
1) batteries being drained,
2) batteries exploding due to a short of up to 300A,
3) a fire being started due to the resistive heating from a short of up to 300A through components of the body or frame.

Edit 3: I emphasize that the inverter has a dedicated neutral that connects directly to the alternator housing. Therefore, ALL return current must pass through this wire unless there is a live-to-ground fault somewhere. In such an event there will be a difference in current between the live and neutral wires, which is the condition upon which I want my mystery device to trip and disconnect the live wire.

Edit 4: Here is a concrete example of a situation I want to prevent from which the fuse offers no protection. Imagine that the vehicle is involved in a collision and the body of the truck pierces the 12V wire insulation. The 12V wire will now have a weak (the body of the truck is painted and likely dirty) short against the truck body, resulting in finite current that could quite possibly be way less than 300A but still sufficient to cause a fire due to resistive heating and/or battery explosion (or even just drain the battery and make the truck unusable).


texts: Can Kalman filter be used to increase sampling rate of a real-time information?

texts:
In my application, I am attempting to control the contact force of an end effector. I am getting very poor performance for two primary reasons: the feedback signal has 1) internal delay and it is significantly 2) undersampled.

Unfortunately I am very limited and I cannot improve on the delay of the feedback signal, however I believe there are methods on improve the sampling rate.

I have heard that you can use a Kalman filter in the feedback line to extrapolate in real-time and predict feedback information and improve on sampling. Before adventuring into this, I was wondering if someone can confirm that you can use a Kalman filter to do this. If not, what other methods can be used. Internal modeling is difficult because this system is dominated by external disturbances.


texts: How does a memory map of a 1K EEPROM look like?

texts:
I am using a 1Kbit: The device is organized as one block of 128 x 8-bit memory. I want to understand how to it's organized and how addresses are structured?
Example: I want to store the world "Hello" in the EEPROM. Every character is coded in 1 Byte; So here we have 5 Bytes in total, since the memory is 128 x 8-bit. every character is going to be stored in a address. My question is how these addresses are organized? Is it something like this:

0x00: H
0x01: E
0x02: L
0x03: L
0x04: O
..
..
0x7F

What I am trying to do is to store data in EEPROM in a specif order. So I have to know how memory map looks like in order to know the start and the end address of each field.
Example:
I want to store: name age date of birth and country in an EEPROM. Let's define 2 functions write(address) and read(address). My problem how to determine 'address'?


texts: Why does crosstalk occur in high speed design only?

texts:
I am studying to get a job in EMC and my exams are coming soon.
I am currently studying "high speed design" techniques, and I stumbled upon this thing called "crosstalk."
I know about coupling. There are 3 types of coupling "inductive" "capacitive" "common impedance" coupling.
Why does crosstalk occurs at high frequencies? What is the relation between frequency and crosstalk?


texts:
I am measuring voltages up to 20V with my ATmega2650 MCU (10-bit ADC).

I'm using 5V precision voltage reference (LT1021 - 0.05%).

Voltage dividers are setup with 1% Panasonic resistors.

Vcc->10kOhm->Measure->3.3kkOhm->GND.

Division ratio: 3.3/13.3=0.248

What I've noticed is the following increasing errors while measuring bigger voltages:

Vmeas   ADC Err(%)
3.05    152 -0.013382929
4.09    205 -0.0075968
5.02    253 -0.002075695
6.08    308 0.003057305
7.07    359 0.0054141
8.07    410 0.00595279
9.07    461 0.00637229
10.02   510 0.007764232
11.05   563 0.008777353
12.05   615 0.01046932
13.05   665 0.008925735
14.05   717 0.010366242
15.06   769 0.010955198
16.05   820 0.011495804
17.07   872 0.011368671
18.06   923 0.011826103
19.04   973 0.011739502
19.51   998 0.01271154
19.94   1020    0.012715509

Can someone explain what is causing such non-linearity?

Any hints on math to estimate this (ADC features rather than poly-fit)?
Any references to mathematical models would help.

EDIT - errors through all voltage range:

The calculation methodology:

#define PSU_ANALOG_CHANNELS     3
#define PSU_ANALOG_MEASURES     5
#define PSU_ANALOG_MEASURE_DELAY 1

//apply vRef to each pin to measure post-divided ADC reading
const int psu_adc_corr[PSU_ANALOG_CHANNELS] =  {250,251,251};

int psu_volts_raw[PSU_ANALOG_CHANNELS];//stores ADC readings
float psu_volts[PSU_ANALOG_CHANNELS] = {0}; //stores final values
float mvAdc[PSU_ANALOG_CHANNELS]; //stores mV per each ADC-channel (to avoid division)

void calcMvADC(){
  for (int i=0; i<PSU_ANALOG_CHANNELS; i++) {
      mvAdc[i] = 5.0 / psu_adc_corr[i];
  }
}

//returns averaged reading for each ADC channel
int readAnalog(int ch) {
  int val = 0;
  for (int i=0; i<PSU_ANALOG_MEASURES; i++) {
    val += analogRead(ch);
    delay(PSU_ANALOG_MEASURE_DELAY);
  }
  return val/PSU_ANALOG_MEASURES;
}

void readADC() {
  for (int i=0; i<PSU_ANALOG_CHANNELS; i++) {
    psu_volts_raw[i]=readAnalog(i);
  }
}

/*
>6 <=7 : -1.1%
>7 <=9: -1.14%
>9 <=13: -1.25%
>13 -1.7%:
*/
float corrVoltage(float V) {
    if (V<6) return V;
    if (V>6 && V<=7) return V*0.989;
    if (V>7 && V<=9) return V*0.9886;
    if (V>9 && V<=13) return V*0.9875;
    if (V>13) return V*0.983;
    return V;
}

void calcVoltages() {
  for (int i=0; i<PSU_ANALOG_CHANNELS; i++) {
    psu_volts[i] = psu_volts_raw[i] * mvAdc[i];
    psu_volts[i] = corrVoltage(psu_volts[i]);
  }
}

void setup (){
  analogReference(EXTERNAL);
  calcMvADC();
  Serial.begin(115200);
}

void loop (){
  readADC();
  calcVoltages();
  for (int i=0; i<PSU_ANALOG_CHANNELS; i++) {
    Serial.println(psu_volts[i]);
  }
  delay(500);
}


texts: How to tackle regenerative current in my H-bridge

texts:
I am using 2 of the following H-Bridge to control 2 x 24V 350W electric scooter DC motors. The power is from 2 x 12V 12AH SLA batteries in series.

EDIT: These are the entire schematic and PCB photos:

The PWM signal controlling this H-Bridge is in locked-antiphase mode at 40KHz.

This H-Bridge works great except that only when the motor brakes and changes direction SWIFTLY, this will make the microcontroller hang oweing to electrical ripples/noise.

I am new to H-Bridges and I am unable to see how regenerative current from the motor (generated when the motor slows down and changes direction) is circulated around the circuit. Would it be the cause of my problem? How to tackle it?

A friend of mine who designs electronic circuits suggests using a 0.1uF capacitor in series with a high power resistor (5W) and connecting both between the motor terminals, in order to absorb the power generated by the motor whenever it works as a power generator. Has anyone done this before?

I am grateful to any help from you!

Ah, I forgot to put in the schematic, but C6 and C9 are 1000uF each. The half bridge driver is IRS2184S. If you want to see the schematic clearer, please do a "Save image as". Thanks in advance.

EDIT 17 Nov 2014 Based on Andy aka's & JonRB's answers:

Thank you both so much for your invaluable advice. I believe you are poiting me in the right direction now!

I plan to get this circuit board redesigned, fabricated and tested with updated result, and these are the changes I am going to make:

Since a 4 layer PCB is not possible here, I intend to use a DIP version of the micro (pitch=2.54mm) so that I can make a full earth plane around the micro
The earth plane of the signal part will be connected directly to Battery (-) rather than to that of the power side, so that return current of the power side goes directly to the battery rather than polluting the signal side

I would like to hear your comments on the following if possible:

If I make the power side and signal side into 2 separate PCBs connected by some wires, with GND of each connected directly to Battery (-), will this be even cleaner? Would you recommend it?
@RonRB: is the braking circuit a must (to make the board run without hanging/data corruption)? I guess we can live without it?

As a self-taught electronics enthusiast, I have been pulling my hair on this problem for a month now, hopefully I will have it resolved thanks to your help.


texts: In an NPN transistor, why doesn't current flow without applying a base voltage?

texts:
In an NPN transistor, why isn't a typical C-E voltage sufficient to overcome the internal resistance of NPN junction directly? Since we only need 0.7V to overcome the PN junction from the Base to Emitter, isn’t that the same as applying a similar (or slightly higher) voltage from Collector to Emitter to achieve the same outcome?

Thinking of it an electronic level, the key thing you’re trying to do is ‘push’ electrons into an area of negative charge – i.e. the Collector. I don’t see why the existing potential difference from Emitter to Collector doesn’t do this without a base potential being applied at all.


texts: How to power a homemade lightbulb safely

texts:
I have created a homemade lightbulb as part of a history project and am wondering how to power it in a manner that is safe enough for school.

The lightbulb consists of a piece of .9 mechanical pencil graphite as a carbon filament in a sealed container (http://www.instructables.com/id/Homemade-Lightbulb/?ALLSTEPS)

I currently have a 12 volt drill battery that successfully powers the bulb to an adequate level for a short time before the alligator clips heat up too much.

I also have a step-down transformer I pulled from somewhere that (according to my measurements) steps down the 120v wall power to two secondary windings that each output 12 volts.

After some research I found out that shorting the secondary coil (which is basically what happens when I connect the light) creates lots of heat and can/should trip a circuit breaker on the primary side. So in other words inadequate for school.

My question is how I can power this lightbulb with minimal heat generated outside the jar in which it is contained. the project is due this Friday and I could turn it in as-is but I'm just trying to optimize it so it's safer. My theory of creating another bulb to increase the resistance wouldn't work due to time constraints

I'm competent with basic electrical engineering tools and terms


texts: Is it true that inductors filter current harmonics and Capacitors filter voltage harmonics in SMPS?

texts:
In switch mode power supply applications, it is true that inductors filter current harmonics and Capacitors filter voltage harmonics?
Is it true that in most applications we use LC filters due to the fact that we need to filter both the voltage and current harmonics?


texts:
I am currently writing a program in AVR Studio, here is the build *Memory Usage : *

Device: atmega32
    Program:    9304 bytes (28.4% Full)
    (.text + .data + .bootloader)
    Data:        334 bytes (16.3% Full)
    (.data + .bss + .noinit)

As I'm using an ATmega32 micro-controller, it seems not to be a problem, but I want to use this same code and use for a ATmega8 micro-controller.

So I want to reduce the program size less than 8192 bytes.

How can I do this?


texts: how to find equations for current of circuit with transistors?

texts:
using Ohm's law, i need to find the current for $$I_C , I_B$$ in terms of: $$V_B, V_C, V_{DC1},V_{DC2}$$
for the following ciruit.

my solution is: $$V_{DC2}+{I_B}{R_B}={I_C}{R_C}+{V_{DC1}}+{V_E}$$
But this seems to be wrong. why?
Thank you


texts: SMD component clearance limitations and guidelines?

texts:
I'm laying out a fairly compact PCB (first SMD design of this degree) and am concerned about how close some of my SMD components are getting.

I've been unable to find any guidelines or advice online for how close I can place SMD components.

My concerns are:

Components sticking/soldering themselves together
Placing low components right next to high components in case the pick and place head can't get in there (i.e. 0402 right next to large connector)

I don't have a fab in mind at this stage, so I'm hoping to get some general/safe rules of thumb.


texts: Using a MOSFET to turn on/off LEDs which could get reverse voltages

texts:
I formerly asked about a LED circuit a long time ago.

The circuit I want to make is 'reverse-voltage notifier'. If the input is reversed, then a LED(below, D2) will lit. Of course, if the input is forward voltage, then another LED(below, D1) will be bright.

Also, I want to use these LEDs only if it is at bright place. In other words, in some occasions, I want to turn off them.

Using a Logic MOSFET is very good choice in my thought. However there's a problem.

simulate this circuit – Schematic created using CircuitLab

I thought this is right, however I don't want to make any smoke and I hadn't confirmed this. V1 could be +12V ~ -12V. Is it right? If it isn't, how could I work on this to work in any conditions(even if the V1 is reverse voltage)?

D1 is for forward-voltage, and D2 is for reverse-voltage. In reverse voltage MCU will not turn on, so I didn't used any MOSFET in D2 circuit.
Of course, the reverse voltage will not excced above 12V. The maximum reverse voltage of the LEDs is 5V.

** Edit : The MCU is STM32F411RE which is I'm using. However I think this will not take an important part in. You could regard the MCU input as just the 0V / 5V logic source. **

You can see the BSS138 datasheet at here:
https://www.onsemi.com/pub/Collateral/BSS138-D.PDF

Thank you.


texts: Increasing current with constant voltage

texts:
simulate this circuit – Schematic created using CircuitLab
I got a sine wave from an STM32 DAC.
Its voltage is 2.64 V. I wanted to amplify it. I used this schematic. Its gain is 4.3. I got 11.20V output of the op amp but the output current is 0.13 mA. I decided to drive a transformer with the output of op amp but the power is too low to do it.
Do you have an idea?
Some people say it is not possible to increase current with constant voltage but I don't know if that's true or not.


texts: What is the name of antenna and connector in the image

texts:
Below is the image of a GPS module. I have highlighted the antenna in the yellow box:

What is the name of the antenna in the yellow box (Question 1) ? Is the type of this antenna APM 2.5 (Question 2) ? What does APM stands for in APM 2.5 (Question 3) ?
Is the connector of the antenna IPX? There are different sizes of IPX, what are they ? Is IPX connector also known as UFL (Question 4)?
I would appreciate answers to any/some/ all of above related questions.


texts:
If I were to design a circuit for a small appliance that works in DC and I would want to allow it to work with the batteries in reverse polarity could I feasibly use a diode bridge?

Would it make sense? Would the energy efficiency drop significantly?


texts: Shall I use a choke or a bead to filter analog power supply?

texts:
Often I have a 3.3V or 5V mixed-signal circuit with a microcontroller running in the 10 MHz range and some analog circuitry, e.g. audio or analog sensor signals, powered from a wall-wart style supply or USB.

So a problem I often come across is how to filter the supply for the analog signals. Shall I use a ferrite bead or a choke? More inductance or less? Or just an RC filter?


texts: Switching Circuit from Arduino to Raspberry Pi (Reading Analog Values)

texts:
I have wired up this circuit from learn.parallax

I have wired this up to an Arduino and it works exactly how I want it too. This is the code that I used to get it working (also from parallax):
void setup()
{
  Serial.begin(9600);
}

void loop()
{
  long dTime = rcTime(8);

  Serial.print("time = ");
  Serial.print(dTime);
  Serial.println(" us");

  delay(1000);                               // 1 second delay
}
                                             // rcTime function at pin
long rcTime(int pin)                         // ..returns decay time
{
  pinMode(pin, OUTPUT);                      // Charge capacitor
  digitalWrite(pin, HIGH);                   // ..by setting pin ouput-high
  delay(1);                                  // ..for 1 ms
  pinMode(pin, INPUT);                       // Set pin to input
  digitalWrite(pin, LOW);                    // ..with no pullup
  long time  = micros();                     // Mark the time
  while(digitalRead(pin) == HIGH);
  time = micros() - time;                    // Calculate decay time
  return time;                               // Return decay time
}

I now need to get this to work on my Raspberry Pi which I did not think would be as difficult as it appears. Here is my current code for what I am trying to do:
# include CircuitPython libraries
from digitalio import DigitalInOut, Direction
from board import *
import time

port = D18

def RCtime(pin):

    #Declaring pin 18 as output
    sensor = DigitalInOut(pin)
    sensor.direction = Direction.OUTPUT

    #Charging capacitor by setting pin to HIGH
    sensor.value = True

    #Wait for 1 millisecond
    time.sleep(0.001)

    #Declaring pin 18 as input
    sensor.direction = Direction.INPUT

    #Set pin to LOW
    sensor.value = False

    #mark the time
    now = time.monotonic()

    while (sensor.value == True):
         now = time.monotonic() - now
    return now

while True:
    dTime = RCtime(port)
    print('time ' + str(dTime) + ' us')

    time.sleep(1)

This does not work. What happens is that I am trying to set the value of a pin as "False" after switching the direction to input which breaks the program. This works in the Arduino software, but not with CircuitPython. If I just comment out the switching direction to input, the program will run but does not work at all as it will display a time and then increment it by 1. I am fairly new to Python, so I am hoping someone with more experience would point me in the right direction!


texts: Why the forward bias voltage of a silicon diode is 0.7V?If we apply a voltage of 0.1V then the depletion region will be minimized.In a diode there is the chemical potential which creates diffusion and there is the electrostatic potential created by the donor and acceptor ions.So if we apply a small voltage which will help the cjemical potential then the majority charge carriers of the n-type semiconductor will diffuse into the p-type semiconductor and the depletion will be destroyed.Where am I wrong?


texts:
I am curious about why there are wings attached to the magjack for the Ethernet.

Other RJ45 jacks without magnetic don't have the wings, but most RJ45 jacks with magnetics inside have them.


texts: Would it be possible to use two UPS in series?

texts:
Would it be possible to use two UPS (uninterruptible power supply) that deliver same voltage (230 VAC) and same power (eg : 2200 VA) in series?

The first one would be connected to the main.
The second one would receive input power from the first UPS. The output of second UPS will be connected to the devices to protect.

Would it increase/double the protection time (battery capacity) or it would just don't work?

Same about putting them in parallel? AFAIK, it would not work because it would require the two phases to have exact same frequency and be in phase (which by default is not the case).


texts:
I have a cicuit here that's giving me trouble when finding out what V1 and V2 equal.The book says that I1 is traveling through the 8 ohm resistor (R1) towards ground. But when I build the circuit on multi-sim it says that I1 is traveling through (R1) upwards "clockwise. I'm confused why the book says I1 is counter clockwise and my simulator says clockwise.

R1 = 8 ohm   R2 = 4 ohm   R3 = 10 ohm  I = 2A   E = 64V

I thought I2 and I add up to I1. I'm so confused. How do I determine the direction of the current so I can build my equation. I always seem to be confused on how to determine the direction of the current. Does it matter? I"m still very confused on node analysis.


texts: Why is the voltage across collector and emitter pushing itself to 0.7 volts?

texts:
I designed a single stage transistor amplifier as shown in this schematic:

I constructed this on a breadboard and applied the DC bias voltage to check the biasing conditions. Prior to this, I made the following assumptions:
1. The collector current ( also almost equal to emitter current) is 2mA.
2. The small signal gain of the transistor is 100.
3. The collector to emitter saturation voltage is 0.2V.

Now with these assumptions, I calculated the resistor values Rc and Re. As per my analysis, I had predicted that the voltage drop across Rc, Rc and Vce would be 3V. But in practice, when I measured the DC voltages, I found the voltage across Rc to be 4.1V, that across emitter was 4.2 volts and the voltage Vce was 0.7 volts.

This meant that the transistor was being driven into saturation and when I connected to a speaker, the output was attenuated rather than amplification. Where did I go wrong in my analysis?


texts:
Where can I find a female RJ45 connector that can be crimped to another cable rather than being soldered to a PCB or installed in a wall or plastic enclosure?
Something like this: http://www.pcpartscollection.com/rjcrmatofeca.html
While we're at it, I'd love to find female RJ11 and RJ12 connectors with the same property.


texts:
I'm preparing for a project that will interface an FPGA with many 3v relays on its gpio. Additionally, some of the relays will be powered with the same power supply that the FPGA uses. The FPGA will actuate certain relays, as well as read signals that are in series with relay coils.

I know that a closing relay can create an inductive voltage spike that might damage the FPGA. Also, I'm not confident that the gpio pins can supply enough current to actuate several relays in parallel.

I've encountered fly-back diodes, voltage followers, and optocouplers before, and I'm pretty sure one or all of these could help here. What should I do to protect my FPGA and make sure it can drive the relays?


texts: Number of windings keeping constant the poles

texts: What happens if I increase the number of windings around the poles keeping constant the number of poles in a motor? for sure the rotational speed should be the same, I think that we will obtain a more stable working point thanks to a higher magnetic flux physically speaking, but I'm not sure. Do you know what is the consequence?


texts: Calculating gains for Op-amps with real AC voltages

texts:
I'm a uni student trying to figure out how to calculate gains of op-amps with recorded real AC voltage inputs and outputs. We are expected to somehow know this for some post-lab work without being told how to do it in any of the lectures.

I'm assuming the gain is still defined as \$ v_{\mathbb{out}}/v_{\mathbb{in}} \$, which would mean the gain would vary of time. I know what the period, peak-to-peak voltages, and crest and trough input and output voltages are. Where do I go from here?

EDIT: By "real AC voltage" I mean actual AC voltages produced and recorded in a laboratory with real circuits; not hypothetical AC voltages with ideal circuits.


texts:
I am trying to design a control for a BLDC motor with a PIC16F887.

I have managed to activate a PWM output and be able to vary it with a potentiometer.
The point is, I need to get 6 PWM signals out.

When I change the CCP1CON I can vary the PWM output but it is always one.

I attach the part of my code where I configure the PWM.

void PWM_Initialize()
{
  PR2 = ("%#x", (_XTAL_FREQ/(PWM_freq*4*TMR2PRESCALE)) - 1);
  CCPR1L = 0x1F;
  RC1 = 0;
  RC2 = 0;
  T2CON = 0x03;
  CCP1CONbits.CCP1M = 0b1100;
  CCP1CONbits.P1M = 0b00;
  TMR2 = 0;
  T2CONbits.TMR2ON = 1; //Timer 2 ON
}

How can I activate multiple PWM outputs?


texts: What is the internal linkage flux of a wire with radius a(shaped like a cylinder)

texts: How can we clarify that the relation between linkage flux an flux in a cylinder shaped wire is \$ d\lambda=\frac{x^2}{a^2}\ d\phi \$?can we illustrate this by electromagnetic formula?I think I would be able to explain this if I knew the exact definition of linkage flux,I think linkage flux is not a real flux that exists(like flux itself),any help would be appreciated.


texts:
I am just learning to build circuits, and I thought I would try my hand at building a 7 segment decoder using just logic gates.

I drew the following schematic in Logisim, and it works, but there are a lot of chips to implement.  I don't have a source for a 13 input OR gate, so it will turn into more chips than the logic diagram shown here.

Q: Can you point me to any tricks that will reduce the gate/transistor count?


texts: Earth Ground's role in 3 prong AC systems

texts:
I've been reading through this explanation where the author goes through the natural progression of why a three-prong AC outlet was made (Why Three Prongs?) , but I have some trouble imagining how earth ground plays a role here.

First off, for just a two prong AC system, which I take it to mean a floating source system, one can't be shocked from touching just one of the two "hot" wires, but only by holding both at the same time and acting as the short circuit between them (does voltage just drop to the value of the wire with the lower potential here, while current spikes?). Just touching one of the hot wires is analogous to only hooking a single wire to one terminal of a battery I imagine--there's no return path for current to start flowing. Even if one were barefoot and standing on a damp floor, with no grounding wire in the system at this point, no danger of shock exists.

So reading further down the link now, how does the fact that the neutral wire (which is grounded) exists allow the hot wire current to go through a person standing on earth ground? The author mentions that by grounding one half of the system, they essentially connected one half of the system under the persons feet. Where specifically is current flowing in the ground to create this loop or return path for current? Is it reaching wiring underground to complete the connection?

To try to drive this idea home, what happens to a power supply when both sides of the circuit are connected to earth ground? How does this make a short circuit between the two sides of the circuit? I thought earth ground was a sort of "reservoir" of sorts that is unaffected by current moving into it.

Any help explaining this concept is greatly appreciated.


texts:
I am having some Somfy motorized curtains installed in my home, but I struggle to understand the following statement in the manual:

Wiring multiple Sonesse 40 WT's in parallel will result in damage to the motor.

Why would this be the case? Even if I didn't wire them directly at the motor end, wouldn't they still end up in a parallel configuration elsewhere in my installation?


texts: What are the terminals in this 6 pin potentiometer?

texts:
I want to use my 6 pin potentiometer in circuits so I want to know what all the terminals are for. I know the basic principle in the 3 pin pot. I'm completely new so please answer it in simple terms. I have attached a circuit which I want to make which pins do I use for it.

I have also checked readings with a multimeter here they are, I have numbered the pins from 1 to 6 starting from left here are the readings:

Pins 1-6 shows a range of 0 ohms to 53k ohms when I turn the knob.
Pins 1-2 show 0 ohms to 53k ohms.
Pins 2-6 shows only 53k ohms no matter what position the knob is in.
Pins 3-4 show 0 ohms to 53k ohms.
Pins 3-5 show 0 ohms to 53k ohms.
Pins 4-5 show 0 ohms to 53k ohms.

I was thinking that 4-5 should only be at 53k ohms and not vary but it varies.

Here's what my pot looks like:

And here is the circuit I want to use it in:


texts: Calculating the peak current of my boost converter

texts:
I am stuck while calculating the peak current in the boost converter through the inductor.

Can you please check if I am right?

Ipeak=(Max Voltage/ R2) = 18/1000=0.018. So, my peak current through the inductor is just 18mA? Am I doing it correct. If this is correct, how will I account for the Vce drop inside the pin1 and pin2 of the IC. The darlington transistor inside the IC is just like a normal transistor. I have added two transistor outside the IC instead of using the darlington switch in the IC for thermal purposes.

Can you please help me with the calculation of Vswce and Ipeak. The calculation of Vswce is not mentioned in the datasheet. So, please help. And the calculation of Peak current is mentioned in the datasheet. But is my approach of calculating the peak current through the inductor right?


texts: Bit Banging a PICAXE 08M2 as an I2C Slave

texts:
Only the X2 parts of the PICAXE family support I2C slave compatibility, but I need to have an 08M2 to act as an I2C slave on a board that I have. Unfortunately I don't have the option of changing micro-controller or making a new board.

I've been reading up on how the I2C protocol works and have found some code which may help, but haven't got any further. Has anyone done a similar thing before? If anyone has some example code which works which I can go from it would be fantastic.


texts:
I have made a wooden case to hold both my Xbox 360 and my PS3. It's as wide as both consoles laid down next to each other and as high as the console. it has 2 doors on the front, one for each console. They're both hinged separately from the bottom. What I want to do is to use a hobby motor to open (push) and close (pull) the door open to 90 degrees. The best way I can see is using plastic cord that has teeth on it and a motor that a teethed head on it to lower and pull the door up.

The problem is:

how can I control the motor to run for a certain time (so it doesn't just keep running) and
how with just one button I can press it and it lowers to 90 degrees and press it again and it will pull the door back up and stop


texts: How do I read I2C memory with an Arduino?

texts:
I have HH100D humidity sensor. It outputs a frequency signal, which I know how to handle. However, it also has a small EEPROM with calibration values that is available via I2C. Those values are necessary to get the actual humidity.

The problem is, that I'm very new to I2C. I cannot figure out how to read out those bytes. I've googled for half a day and still got no solution.

There's something I have:

HH100D datasheet
M24C02 EEPROM datasheet
A topic on this forum (German)


texts:
I have a project involving a small robot and I need to write the firmware to control the wheels. Its not something I have done before, so I did some research.
In my research I saw that some people use optical encoders and PID to allow the motors to have consistent power.

My question is, is this always needed? I can understand how PID works and what the optical encoder is for, but its not clear to me exactly why its needed.

The robot does not need to track distance, direction of its motors or anything like that. It will move according to time e.g. move forward 2s

Thanks

EDIT:
To clarify on the spec:

The robot will be given instructions before it starts
instructions will always be pretty simple such as go straight for 5 seconds, turn left, turn right
The robot is never controlled by a person in real time, it just executes its instructions and stops.
It could execute instructions depending on sensor inputs for example if it detects an object using ultrasonic sensor, it may move backwards for 2 seconds.
The speed that the robot moves is not that important. For moving straight, one speed can be set (using pwm)


texts:
The question is which logic function does this circuit implement if A and B are input and Y is output?

I'm not familiar how 4-terminal MOSFET works but trying to solve Y using A=0 B= 0

The abovest transistor wouldn't be turned on because \$V_{SG} = 0\$

The belowest transistor also cannot be turned on because \$V_{GS}\$  is negative.

For the transistor having \$V_{DD}\$ at base, which side should we choose as a source?

Edit: I still don't know where to expect source when \$V_{DD}\$ and \$GND\$ are ignored as it is said in the comments. I would appreciate an explanation in solving this.


texts: How can I tell if my building plumbing provides an adequate ground?

texts: I work in an old building with two-wire wiring, i.e. no separate ground. Is there some minimum-equipment-purchase way to tell if a wire soldered to a building plumbing pipe is an adequate ground? I have a standard hand-held multi-meter.


texts: What is the maximum lumens an Infrared LED can dissipate?

texts: I am planning to shoot a video under Infrared light and want to choose a ton of the right size so that the entire room is illuminated. I am on to build a separate circuit if need be for better visibility. Please suggest


texts:
From Wikipedia:

  When a transformer, electromagnet, or other inductive load is switched
  off, the inductor increases the voltage across the switch or breaker
  and cause extended arcing. When a transformer is switched off on its
  primary side, inductive kick produces a voltage spike on the secondary
  that can damage insulation and connected loads.

How to avoid transformer switch off spike and protect the circuit?

Is it something that we should be worried about for low power designs (e.g. step down 2A transformer)?


texts:
I'm trying to simulate parallel resonant ciruit. I'm also useing Bode analyzer but the result is different from what it should be.
My circuit:

And the result is:

Do you know what I am doing wrong?
Thanks!


texts: Can you use Oscilloscope probes for a Function Generator?

texts: I just bought a cheap function generator and have no test leads for it. I do have 2 pairs of oscilloscope probes with a 1X-10X switch on them. I am curious to know if I will get the same results with them?


texts: Generating a sine wave over a big frequency range

texts:
I want to build a circuit that can generate sine waves at frequencies controlled by a computer or a microcontroller. I would like to go as low as 0.01 Hz (down to 0.05 Hz would probably be acceptable) and as high as 100 kHz; I need at least 10 frequencies per decade, which is a resolution of roughly 12 mHz at the bottom of the scale (or 60 mHz if the bottom is 0.05 Hz). The output voltage doesn't need to be high - I'm going to run it through some op-amps afterwards anyways.

What is the standard way of doing this? Is DDS the way to go (using either a sine lookup table on a uC or an IC like the AD9850)? Is there a simple analog solution that I'm missing?

I would love to stick to through-hole parts if I can.


texts: Problem with stepper motor not landing on same spot

texts:
I had a quick question regarding a stepper motor that I'm working with. I am running the 5 pin, 5V motor via an Arduino board and using the sketches provided. I am trying to get the motor to rotate in full circles broken up into small segments and although it is working (currently I have 7 'stops')I can't seem to get the stops where the motor stops to overlap. There's always a slight change that throws everything off. Any ideas?

/*
Stepper Motor Control - one revolution

This program drives a unipolar or bipolar stepper motor.
The motor is attached to digital pins 8 - 11 of the Arduino.

The motor should revolve one revolution in one direction, then
one revolution in the other direction.

Created 11 Mar. 2007
Modified 30 Nov. 2009
by Tom Igoe

*/

#include <Stepper.h>

const int stepsPerRevolution = 200;  // change this to fit the number of steps per                                 revolution
                                 // for your motor

// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 8,9,10,11);
int stepCount = 0;  // number of steps the motor has taken

void setup() {
// set the speed at 60 rpm:
myStepper.setSpeed(60);
// initialize the serial port:
Serial.begin(9600);
}

void loop() {
// read the sensor value:
int sensorReading = analogRead(A0);
// map it to a range from 0 to 100:
int motorSpeed = map(sensorReading, 0, 1023, 0, 100);
// set the motor speed:
if (motorSpeed > 0) {
myStepper.setSpeed(motorSpeed);
// step 1/100 of a revolution:
myStepper.step(stepsPerRevolution/100);
}
// step one revolution  in one direction:
Serial.println("clockwise");
myStepper.step(stepsPerRevolution);
delay(500);

// step one revolution in the other direction:
Serial.println("counterclockwise");
myStepper.step(-stepsPerRevolution);
delay(500);
}


texts: In verilog code, what happens when repeat statement exists inside always statement with posedge?

texts:
For example,

always @(posedge clk)
begin
    repeat (20)
        @(posedge clk) ;
end

In this statement, when the clk is triggered at first time, repeat statement will be executed. However, if the clk is triggered next time, does it mean that there are two running repeat statements?


texts: Still struggling with the STM32F051C8T6 bootloader

texts:
I've been reading the information available in ST.com about creating a bootloader for a STM32F0xxx microcontroller, and it says the following:

"The bootloader is automatically activated by configuring the BOOT0 and BOOT1 pins in the
specific “System memory” configuration and then by applying a reset."

"In some products, BOOT1 is not an I/O but a bit in the option byte area. This is the case for
the STM32F05x and STM32F3xx devices where BOOT1 is configured through nBoot1 bit in
the option bytes."

"The hardware required to put the STM32F051xx devices into System memory boot mode
consists of any circuitry, switch or jumper, capable of holding the BOOT0 pin high while
nBOOT1 bit in the option bytes (starting at address 0x1FFFF800) is set to value
1. The setting of this bit can be done through STLINK utility or an equivalent tool."

So, if I want to load my programs in this microcontroller, I need to set the nBOOT1 bit to 1 by software. But how can I change its value if I hadn't communicated with it yet, as I need to change it before communicating? :S

Then, do I need to buy the STLINK utility if I want to bootload my custom programs? :S


texts: Reactive vs Real Power in DC-DC Converters

texts:
I don't understand which form of power, reactive or real, should be dominant in a maximally efficient DC-DC boost converter.

As the circuit charges the inductor, the current and voltage will be out of phase. This seems like a textbook example of reactive power: the load, an inductor, is almost purely reactive and there's a phase shift between current and voltage (the equation for reactive power clearly shows a phase angle, φ, closer to π/2 would make the power more reactive: Q = |S|sin(φ) ). Intuitively, this seems like a good thing - you don't want real power being dissipated in the inductor and producing waste heat.

This seems to conflict with the definitions of real vs reactive power!

According to wikipedia's entry for "AC power", real power is that which results in the net transfer of energy in one direction (eg. into the load), and reactive power is power which results in no net transfer of energy between source and load because the energy is passed back and forth between them. With an ideal DC-DC converter, however, no energy will be passed back from the inductor to the charging circuit because the energy will instead be sent to the converter's output. This completely goes against the definition of reactive power as having a net zero energy transfer.

How can the two ways of analyzing the converter's power be reconciled?


texts: Multiple buck converters on the same PCB, should switching frequency be the same?

texts:
I have a question regarding dc-dc buck converters. I need to supply multiple different voltages on my board and I am very limitted with power this is why I need to use high efficiency converters. If they are to be placed near to each other should their switching frequency be the same? As far as I know this would be better due to the EMI and SI issues, it's easier to get rid off one frequency than multiple of them and their harmonics, products etc.

On the other hand if it's not essential, than increasing the switching frequency will decrease the size of the inductors.

Any help would be appreciated


texts: What type of battery is used in Oura ring?

texts: What type of battery is used in Oura ring, and how many mAh is available? I am not sure how does Oura ring manage to claim up to 7 days of battery life. Should not using an LED and BLE connection in continuous mode drain the battery before 7 days that they claim?


texts:
I am trying to understand this circuit.
There is a diode D2 connected parallel to MOSFET M1 on page 9.

I got the idea that it might be used for protecting the MOSFET.
Can someone explain to me the exact use of this diode?


texts: Sizing Transistors for 2.2hp universal motor controller

texts:
my background is mechanical and as you can see I have just enough electrical knowledge to be dangerous.

I have an application where I'm trying to use 2xFDP51N25 in parallel
to drive a (2.2hp) universal motor from a circular saw. Bench testing no load everything works fine. The transistors short (drain to source) as soon as under load. The transistors barely get warm and do not pop at failure. The motor measures 1.3ohms and I suspect it's the start current but am out of my depth so wouldn't be surprised if it something else.  I'm looking at adding a flyback diode for the motor and new transistors with a 350A pulse rating. There's probably a good reason why you don't see this application much....lol.   I'm open to any suggestions or criticisms.     Thanks

Application:
Continuous Duty
2 x FDPF51N25 transistor in parallel
with heat sinks and fan cooling
980hz PWM to gate (0-5vdc) for control
Series wound ac/dc brushed motor 1.3ohms
Tagged as 15Amps/120 volts
Supply voltage 90vdc battery


texts: How to select the right details for activating solenoid valve

texts:
I'm working on a smart watering system as a home project. I have a water output in my balcony (a tap) and I want to control the water flow using an Arduino Uno and a solenoid valve. I still don't have the valve but the specifications of it are listed here - I'm using Model No. SMOKVW-0516O4.7AC which is the last one on the list (at least that is the plan for now, but I hope to achieve general understanding of how to choose the right components such that even if I'm using different valve at the end, I can adjust the transistor and diode accordingly). My plan is to use a transistor to control the solenoid valve and to use a diode to handle the kickback. My problem is that I'm not sure which specifications of the transistor and the diode I need for this purpose, I've tried looking online for information but I didn't find anything that solved my problem. What I'd like to know is how to adjust the transistor and diode to the solenoid valve I'm using, the things that I'd be grateful if anyone can help me with:

which transistor do I prefer to use? I thought NPN will be suitable since I need an amplification (my Arduino supplies 5V where the solenoid valve expects 12V input signal) although I also need it to behave like a switch, in order to turn on and off the valve.
wich parameters should I check when selecting a specific model of a transistor? i.e. if I chose to use NPN, how do I know that the specification of the transistor will allow it to work as expected? how will I know it won't burn?
I have understood that the solenoid valve has a "kickback" - a current flows in the opposite direction (from the valve to the arduino) when the valve is turned off, and to protect the board I need to add a diode. I'm not sure how can I calculate the current that suppose to be returned or how to choose the right diode?

Thank you very much for your time and attetion


texts: I've just started a new "sunday project", the aim of which is to build an ROV. I was wandering if I could use my spare VRLA battery (NEXON XT line 12v/33Ah) as an onboard power supply. Do these batteries emit hydrogen during work? Can I put it safely in sealed box and not worry about it exploding underwater?


texts: What's the difference between sensitivity and resolution of an SMU?

texts:
In Keithley's Low Level Measurements Handbook, 7th ed the two terms are defined as:

  SENSITIVITY - the smallest change in the signal that can be
  detected.

  RESOLUTION - the smallest portion of the signal that can
  be observed.

which sounds exactly the same to me when looking at the system as a whole: resolution is limited by sensitivity and sensitivity is limited by resolution. The only case the two terms seem to have useful separate meaning is when addressing the sensitivity of the measuring component vs. the resolution of the sampling component.

Am I missing something here?


texts: I understand dc load line : for a given collector arrangement it lists all the possible values of (V_ce, I_c). So I expected that the AC load line should be the line on which all possible AC values of (v_ce, i_ce) would stay. But it looks like this line deals with all pairs of superimposed (ac+dc) collector-emtter voltage and current, is this correct? Or is this something else?


texts:
Often in MCU boards I see optocouplers even when the power supply is the same on both sides.
Example:

simulate this circuit – Schematic created using CircuitLab
Here +3V3 and +12V have the same GND so there is no galvanic isolation between the MCU and the external world.
I guess using an optocoupler is more robust that connecting directly the wire to the MCU, but I wonder if there is a good reason to do that instead of using, say, a BJT or a line driver.


texts:
I am using Keil uVision5 for programming TI launchpad TM4C123GXL.

The Keil work perfectly fine for Building and flashing the programs (examples projects of Tiva Ware).
But when I start the Debug session, At first DebuggingMode seems to open perfectly but a second afterword it automatically shuts down.

I have the same software working fine on another PC but it is not working on my laptop.

How can I remove this bug so that I can do Debugging?

It used to work fine a few months ago. But now it's not working. Do I have changed any setting?
I have reinstalled the Keil but the problem persists.


texts:
So I've done this so far, and  know one of the components is a 50ohm resistor. However I dont know where to go from here. How do i decide if its an inductor or a capacitor?
This is a past paper exam so im aware the other component is a 125nH inductor... but how do i get to that?


texts:
Assume there is a piece of metal. I would like to identify, with a microcontroller, if another metallic object is touching this piece.

I want to apply this for a smart hook that "knows" if a keychain is hanging on it.

Is there a standard way of sensing such changes?

I have an idea to connect the piece to a leaf of a capacitor and to measure the momentary change of voltage when the metals touch or deattach. Is this a good idea?

Edit: Long time after asking the question I stumbled into this project which looks like what I was asking for in the first place. https://www.reddit.com/r/MSP430/comments/4clen1/capacitive_touch_sensor_circuit_and_code/


texts: How can I create AND/OR logic gates using comparators?

texts:
I want to create AND/OR logic gates using comparators which do not consume a lot of currents. I tried to design the gates using transistors as shown below. But, this might draw a lot of currents.

At the end,

I want minimal current flowing through the circuit and 3.0-3.3 volts at Vout.

simulate this circuit – Schematic created using CircuitLab


texts: Regulator that can handle voltage on its output

texts: I need a voltage regulator for a project which will handle a voltage on its output pin with no input. (The GND pin may still be connected.) Most devices don't seem to be able to handle this. Are there any which can?


texts: What are the pros and cons of resistive and capacitive touchscreen mobile devices?

texts:
I have zeroed it down to these two phones Nokia X6 and Nokia C6.

Apart from others, one difference is the presence of capacitive touchscreen in one and resistive in the other.

If I were to decide only on the basis of these touchscreen technologies, which one should I go for?


texts: I'm using Altium Designer version 14.2. I am making a thermal analysis. The  Analyze program expects a ODB++ format input from me. When I convert my PCB to ODB++, I can't see any height information about my PCB component on analysis program. When I am searching to fix this problem, I found some information. When I look at my pcb library, I saw there is no height information on my component, but there is a 3D CAD file associated. But there is overall height information. How can I convert overall height to height? Or is there any solution for this problem?


texts: My inverter keeps flipping between battery/mains slowly at first, then faster. Why?

texts:
Here's the situation.

I'm possessed of an inverter purchased nearly a decade ago.
A few months ago it started to make a clicking noise of it's own volition
The repairman said he replaced the relay and then it worked fine ... until now
By trial-and-error I discovered that enabling the bypass switch (so the inverter is powered from the battery) would kill the tripping. Killing the bypass brought up the tripping again.
More importantly, the longer the duration the bypass was enabled, the longer the wait before it would start to trip again; slowly at first and picking up speed with each cycle.
The repairman who fixed it originally and the other ones I've contacted are not bothered and recommend replacing the inverter altogether!
I have some basic exposure to electronics; my impression is that the relay is good but there is some condensor out of the kilter.

The idea of replacing the inverter  merely because it flips isn't fun, and stinks of an attempt to earn some commission on the sale. I'll replace if I must, but not without giving it a try myself!

What I would like to know from you

Does my impression about the condensor sound right?
How should I go about finding out the fault?


texts: What is the accuracy of a thermocouple after calibration?

texts:
I'd like to use a thermocouple to create a general-purpose temperature probe.  However, the accuracy is quite a bit lower than I want.  Almost every source I look at (example) lists the accuracy of a type-K thermocouple as being 2.2 °C or 0.75% "standard," or 1.1 °C or 0.4% "special."  (I've chosen type K for both wide range and low cost.)

On the electronics side I'm quite confidant that I can get better than ±0.1 °C, meaning that the accuracy is pretty much entirely limited by the physical probe.

Confusingly, I see some (far more expensive) thermocouple probes listed at much higher accuracy than for the thermocouple itself.  For example, ThermoWorks lists some type-T thermocouple probes as being accurate to 0.1 °C, even though the accuracy of plain type-T thermocouples is always listed as only 1.0 °C "standard," and 0.5 °C "special."

My thought is that I should be able to achieve higher accuracy by calibrating the thermocouple.  A proper ice bath (using shaved ice made from distilled water) should let me get comfortably within 0.1 °C (NIST makes ice baths repeatable to better than 0.001 °C).  This would let me perform a single-point calibration of the entire system (including the cold junction reference, for which I'm probably going to use a platinum RTD).  My question is, what kind of accuracy I can expect after calibration?

Another way of phrasing the question is, how much of the specified measurement error is due to random variance versus (removable) systemic error?


texts: Is printing a PLA box for electronic components safe?

texts:
not sure I'm in the good place.
I'm working on a small project, building a connected light dimmer for my home. I'm using a raspberry pi zero and an AC dimmer (this one : Universal AC MAINS Dimmer - MPDMv4.1). All is working fine. Now I want to install it into a room and I need an electric box to put the dimmer in. I have no knowledge in electrical stuff but I was thinking about printing my own PLA box to put the dimer and the raspberry inside. Do you think this material could be safe enough ? I would not want to start a fire... Otherwise would you have any suggestions / better ideas ?


texts: Exiting Virtual Ground back to Zero Volts Reference

texts:
I have a circuit using LM358N and LTC6240 op amps. The supply is 0-5V and I have used a virtual ground circuit, where 2.5V is my reference.
I am happy with my filtered and amplified signal and now want to connect it to the external interrupt of a PIC18F4550. I therefore need to transpose my ac signal from -2.5 - +2.5V to 0-5V

I have tried summing  2.5V from a voltage divider with my signal but get a 0V DC output.

I'm quite perplexed as it seems a simple procedure.


texts: State Diagram Issue - Equivalent Situations

texts:
How do I know according to the following diagram if I have a equivalent situations, how do I recognize it?

for example we will examine S2 and S3.

I would like to get an advice how to do it.
Thanks!


texts: Piezo as a switch to flash an led when disturbed

texts:
An LED embedded in a small translucent item (say half the size of a pack of cards) that would flash on briefly if the object was disturbed or tipped over.
I immediately responded that a piezoelectric sensor/generator inside the object wired to an LED would do it.
However, when I tried to demonstrate this concept using a piezo buzzer I liberated from an old phone, I could only get the LED to register a dim blip when I smashed the piezo buzzer with a blunt object.
How would I ensure that a piezo sensor/generator would actually light up the LED adequately without the application of blunt force trauma.
As I mentioned, space would be an issue so no large parts, breadboards, or really complex circuitry.
I'm just trying to figure out the easiest and smallest way to accomplish this simple task.
Thanks a lot for any help you can give me!


texts: Floating multiple sealed lead acid batteries in parallel

texts:
I know with multiple lead-acid batteries you should really charge them separately so that one battery doesn't try and charge another and waste power.

But that holds true for the main charging process.

What about the "float" portion of the charge?

I have a number of SLA batteries that I'd like to keep charged up.  The initial charge of each battery will be done separately as and when they get removed from the bank and used, but between uses, when they have been fully charged, I'd like to have a single float charger to keep them topped up.

Is it safe to just whack them all in parallel with the one float charger, or would I need to have some form of separation (e.g., a diode per battery), or even an individual float charge circuit per battery?  I'd like to keep it as simple and cheap as possible.


texts: How to read Operational Amplifier documentation

texts:
I am reading the documentation of an operational amplifier, and I do not understand certain values. For example, for this AO http://www.ti.com/lit/ds/symlink/lmh6601.pdf :

The documentation indiactes the bandwidth is 250, does this refers as the difference between the high and low cutoff frequencies, or the average value of the cutoff frequencies? (cf fc here :
https://en.wikipedia.org/wiki/Cutoff_frequency)
About the figures page 12, the curve start to decrease at approximately 100 MHz, the name of this values is the high cutoff frequency, what is the name of this value in the document?
Why are there different curves? I see that the gain (Av in the document) is the parameters that changes between all the curves, but I thought that the gain was measured, not a parameter. Plus, it is negative for some curves.

I know this is very basic questions, but I do not know where to find answers because I do not know the abbreviations. Thnk you for your time.


texts: create delay before the next click on doorbell

texts: I'm in a place where noisy people have the habit to click the doorbell many times ding ding ding, is there a way to make the doorbell, that when he clicks it, then he should wait 20 seconds for example until the next click? (cut the current for 20 seconds )  Sorry for that abstract question, but I have little experience with electricity, the current is 230 - 240 Volt.


texts:
A good background on the problem can be found in the document: (Under Voltage Lock-Out Design Rules for Proper Start-Up of Energy Autonomous Systems Powered by Supercapacitors).

The above document seems to suggest that a hysteresis comparator driving a high side switch is the best approach. But the actual design is left a bit fuzzy.

Here is the example circuit:

simulate this circuit – Schematic created using CircuitLab

An LTC1540 drives an N-MOS into a P-MOS to switch the high side of the load. Supposedly V-high is 3.6V and V-low is 3.2V in that configuration.

So the questions:

1a) Is this the best way to go about it?

1b) Is there a simpler method that would be almost as good?

2) How do you go about figuring out what component values you need to give the hysteresis window desired? The math seems kind of complicated and I haven't found any good guides on it.

3) How does the example comparator actually work? It has the HYST pin connected to a CAP into GND, normally I would have thought some sort of voltage divider would be connected to HYST?


texts: Nodal analysis - what to do when a supernode spans entire circuit

texts:
I'm back again with a nodal analysis question. I'm getting better, but I've come to a problem again.
Consider the following circuit with the bottom node as ground:

I specifically don't know how to deal with the two lower left branches. When I apply KVL I get equations of the form v1 = v1 and v2 = v2, which is not helpful. One of them is also a dependent source, so I can't just use source transformations as far as I know.
I know that this problem ought to be a lot easier with mesh current analysis. Unfortunately, I'm doing this problem for educational purposes and we're expected to be able to solve this problem with nodal analysis too.
Thanks in advance again,
Joshua


texts:
If I have a MOSFET (or a number of paralleled MOSFETs) driving a motor, what determines the maximum bandwidth (PWM frequency) at which I can excite a motor phase?

Is this only a function of the total gate capacitance of the MOSFETs and the current rating of the MOSFET driver, or are there other factors that will be at play here?


texts: Opamp topology without a stable voltage reference

texts:
I have an opamp configured as a constant current sink like this:

As you can see, the reference voltage for the SENSE pin is set by the voltage divider on the left. This requires a stable voltage on VCC - if it varies, so will the set voltage and thus the current passing through Q1.

I'd like to be able to run the opamp off a supercap or unregulated battery as a power supply, which means VCC won't be entirely stable. Is there an alternative topology for the opamp that achieves the same result without requiring a stable voltage source, or the introduction of an LDO or voltage reference?


texts:
What are the advantages in power electronics of Matlab in comparison with LtSpice and vice versa ?

Thank you very much and have a nice day ! :D


texts:
I'm trying to finally apply what I learned at university in the course of power electronics.
However I find that both that course and most of the books / online references are lacking on some points.

In fact (this may be similar to controlling H-bridges for motor drivers, not sure) there are some possibilities concerning how to realize a step-down (buck) converter:

Using PMOS as input switch (source at supply voltage) -> gate of the PMOS needs to be HIGH when PMOS is off, while gate of the PMOS needs to be LOW when PMOS is on
Using NMOS as input switch (drain at supply voltage) -> gate of the NMOS must be commanded via boostrapping (needs an additionnal Diode and Capacitor)

Additionnally it may be a good idea to use a synchronous buck converter (less losses) using an NMOS in parallel to the output diode. I think I got this part and - anyway - it's simpler to command since it's an NMOS with its source tied to the ground.

Back to the original question: while I agree that it may be (theoritically) possible to easily control the PMOS transistor, I think it's pretty difficult, expecially with high input voltages.

Consider that I take power from the wall outlet: 230V_RMS at 10A max (but for my applications I will go for much less, 1A max). I'm gonna get a pseudo-DC voltage by using a bridge rectifier (Gretz's bridge) with a capacitor at its output (standard practice). This last voltage will be the input of my DC/DC buck converter.

Hence the problem: using a microcontroller to generate a PWN signal to control the output voltage (GPIO: 3.3V output, or 5V at best) it's not gonna be possible to activate the NMOS or deactivate the PMOS.

I think I need the NMOS's gate voltage needs to be around 5-10V above the supply voltage. I'll have to do the bootstrapping for that, yet I didn't really understand it. That's what basically GATE drivers are made for AFAIK.

As for the PMOS a simpler solution may be to use an inverted PWM signal (D = PWM at level LOW, normally it's the reverse) and control an optocoupler which has its collector connected to the supply voltage (same as the PMOS source's voltage). Collectors able to sustain that voltage exist, yet there may be a better solution.

There aren't many high voltage MOSFET drivers available on the market (let alone at low cost) and I would really like to know how to do this. I think step-down/buck converters are quite common nowadays, so I find it hard that no such products exist. This leads me to believe that I'm not looking at the right components (yet). Or the only solution would be to realize the driver in discrete components? Any product reccomandation / reference to satisfy these requirements?

EDIT: as I said to Oliven Lathrop here is what I have in mind to control the PMOS. Basically I use a BJT as a current source and then shunt just enough of the voltage (12-15V) to get the PMOS in conduction mode. Otherwise ideally no current flows in the BJT and the PMOS is blocked.
PMOS CONTROL http://img513.imageshack.us/img513/1879/pmoscommand.png.

I have not verified the polarity of the PWM signal (should it be reversed or not) but in principle this may "just" work. NPN transistors supporting > 400V_DC are much more common than PNP/PMOS and their price is small. A small current in the BJT is enough. Therefore R2 has to be quite large (in order to get I_BJT_Collector ~ 1mA) and R1 just large enough (but not too much, otherwise the charge takes too long and I dissipate too much energy). May pose a problem for the discharge though, since the accumulated charges can't be evacuated?

EDIT2: I know on the schematic I represented an NMOS transistor, but there was no PMOS symbol in the schematic program I'm currently using. It's actually a PMOS!

EDIT3: On second though I'm not sure this would work since the current is imposed in the NPN, not through R1. It may just work if the current going into the MOS (I_G > 0) adds up with the collector's current of the NPN (I_C > 0). This way the voltage drop actually increases and conduction is assured. Still doubts on the opposide process though.


texts: L6234D three phase motor driver, atmega328p, and brushless motor speed

texts:
Folks,

this question involves an arduino, a brushless motor, and L6234D three phase motor driver.

A very nice description of the principles to use the L6234D be found at this site. The gist it's operation is it does not use PWM, but rather a it employs "sine-wave modulated PWM" which essentially supplies psuedo-sine waves to the controller to run the brushless motor at low speeds.

To simplify things there are lovely boards that have the L6234D with a built in Atmega328p put together by our colleagues in china. (search "rctimer brushless gimbal controller")

The circuit for these boards can be found here

I have a long explanation of using a brushless motor driver at my github site that no one should care about. (My write and code to run the thing is in a comment below).

So my problem is this. I want the motor to run faster. The key issue is my code has a delay in it as it steps through passing PWMs to the three inputs to the L6234D, and if I shorten that delay to a small number of milliseconds, the motor stops turning and just jitters.

Does anyone have any suggestions for how I can increase the speed of the motor? The documentation up in my first link shows a graph where the motor runs faster when SPWM is not used - but I cant apply digital levels to the enable pins on the L6234D because I'm working with hardwired circuit board.

thanks in advance


texts: Can rated stator voltage frequency be exceeded safely in an induction motor?

texts:
The following induction motor at the link has rated 50Hz stator freq. on namespace label:

http://www.vanbodegraven.nl/en/products/ac-motors/asea-mbg-200-m-60-6/

It seems it is 6 pole since it has 970 rated rpm and therefore sync. freq. is 1000 rpm.
Which means this motor cannot exceed 1000 rpm unless its stator freq. more than 50Hz.

A VFD speed control reads 1070 rpm mechanical speed when at full speed.
It means it is definitely applying more than 60Hz to stator windings.

My question is is that safe to apply a volateg with more than 50Hz if the rated freq. is 50Hz?


texts: Increase the analog sample rate of the IOIO?

texts: On the analogue input wiki page for the Sparkfun IOIO (android development board), it says that the analogue pins are sampled at 1kHz. This is too low for a number of potentially exciting uses, like multiple-channel audio input, or use as an oscilloscope, or logic probe. But the wiki page says that the physical limitation is 500kHz, which would be more than enough for some of those uses. Is it possible to modify the current generation of IOIOs to increase the analogue sample rate?


texts: 18V from printer USB port. Is that normal?

texts:
I have HP 1514 printer. I noticed that the usb type A plug coming from printer has as buzzing feeling when touching skin. I connected one multimeter probe to the USB plug and the other one to ground pin in my power outlet as shown in the sketch below. The multimeter shows 18V. Shows 0 when measuring current with same setup.

I believe that this is not okay? What could be the cause? Could I damage my Macbook by using this printer (I have used it for a year with no problems, though)


texts: Can't find a high power linear power brick?

texts:
I've searched for quite a while, so I'm fairly sure I'm not doing things right. I need someone to point me in the right direction as I'm sure there's a better option.

I'm looking for a highish power (30V, 3A - preferably a little higher than this because I want it to go up to 30V) linear power brick for my power supply project. I've struggled to find one, so I assume I'm doing something wrong. Is this because such a high power will have high voltage losses over a wire?

I don't want a switching power supply as this will be a lab supply.

I generally wouldn't mind using an IEC connector and wiring a transformer myself, but I'm not completely sure enough of standards for isolated mains electrical supplies (of course this power supply has to be isolated).

I should probably add that I live in Australia, but that shouldn't change much, I can still buy stuff from ali express.


texts:
In my book, it is written that at any instant,

PD across the Capacitor Plates = Applied EMF ---------(1)

Assuming that it's a pure Capacitor of Capacitance C, I think if Voltage across Capacitor becomes equal to the Applied EMF then, it means that the capacitor is fully charged and thus, no current will flow.

Also, how can it be true that the given statement (1) is true at any instant?

As per the Phasor Relationship between Applied EMF and Current in Circuit, the Current is 0 at π/2 and at odd multiples of π/2 where the Applied EMF corresponds to its Peak Value.So Capacitor becomes fully charged at these instances.

Thus, what i think:

PD across Capacitor Plates = Peak Value of Applied EMF

Where am I wrong?


texts: Designing 125 KHz RFID Rectangular Spiral Antenna for FPC

texts:
Am trying to design a rectangular loop antenna similar to this paper from Melexis for an HF antenna design, however i want to implement something similar but for 125 KHz rectangular antenna.
Now using the Frequency resonance formula i get a needed inductance of about 4.9 mH as the chip am using has an internal capacitance of about 330pF. I have a very limited space for my application which the antenna shouldn't exceed 20x6 mm.
Based on the formula from Appendix A from the paper it calculates the physical dimensions of the antenna but the inductance i get is extremely low something like 1.6 pH within the dimensions mentioned above, i tried adding a capacitor in parallel and i would get using the resonance frequency formula a lower inductance but i can not seem to be able to get a matching for to make an antenna of this size and design at this frequency. any pointers or papers would be great help!
Thank you so much have a wonderful day ahead.


texts: Some questions about drift at the output due to transducer or amplifier

texts:
I have instrumentation amplifier box/circuit using a INA128 amplifier. Inside the same box the output of this goes to another amplifier for a larger modifiable gain. All this is used to amplify a force transducer's mV level outputs. The force transducer is using Wheatstone bridges.

I observe large drifts during time and I suspect about the temperature. I cannot verify if the drift is due to the transducer or the amplifier.

So I'm planning to measure the outputs of both amplifier and the force transducer at a constant force/load.

1-) And if I see a change in the force transducer's output it means the transducer is causing this drift and is defect?

2-) If there is no change in the force transducer's output but there is change in the instrumentation amplifier's output it means the amplifier is drifting. How can I calculate the drift of the INA128 after a 10°C increase if its gain is set to 300 for an initial 1mV differential input? I wonder if the drift Im experiencing is normal or not..


texts: How can I test wether my OCXO VCO is working fine?

texts:
I recently bought a PTOC32227 OCXO (datasheet) from eBay (secondhand). It is supposed to output a square wave at 10MHz. However, it is a part of a bigger circuit that is not working properly and it seems to me that the failing component may be the OCXO.

I took it apart from the rest of the board, and connected its VS pin to +5V, GND to ground and measured the HF pin with an oscilloscope (left the VC pin not connected). This is the output:

Shouldn't it be an square wave? How can I determine then if the OCXO is working properly?

Thank you!

Edit: my oscilloscope BW is 100MHz, so it should not be a problem in the measurement

Edit 2: new measurements with my probe in x10 mode seem fine! Thanks!


texts:
I have some questions about http://fpgacpu.ca/fpga/Pipeline_Skid_Buffer.html

1) Why is skid buffer designed to be 2-entries FIFO instead of just 1-entry FIFO ?

  However, pipelining handshaking is more complicated: simply adding a
  pipeline register to the valid, ready, and data lines will work, but
  now each transfer take two cycles to start, and two cycles to stop.

2) Quoted from the article , why two cycles to start, and two cycles to stop ?


texts: Microcontroller input pin impedance/leakage current

texts:
I'm using the internal ADC of an ATMEGA324PA to measure the voltage of a low power 3.6V battery. The ADC is referenced to it's internal 2.56V and I need to use a voltage divider on the battery.
To not draw too much current form battery I'm using large value resistors, but this is a problem, because the ADC input pin on uC is leaking at the most 1uA (according to the datasheet - page 328).

This can easily be compensated in the code, but is this leakage current constant? Does it vary with temperature, Vcc, etc. How much does it vary? Is this leakage caused by the input pin protection diodes (page 74)?


texts:
I require recommendations for the layout of crystal.
I am designing a board which uses an external RTC. The Mfr. part number for RTC is PCF8523TK/1,118 and Mouser part number is 771-PCF8523TK/1118. It uses a crystal (32.768kHz, Load cap 7pF, temp range -40C +85C) with Mfr. part number ECS-.327-7-12R-TR and  Mouser part number 520-.327-7-12R-T. Schematic and PCB layout are attached below.
Please share your feedback.
Schematic

PCB layout


texts:
After synthesizing my RTL level design into verilog netlist, I find the syntax confusing. Here is what I mean.

RTL compiler gives me:

  MUX2X1 g11005(.A (n_741), .B (\in_a[9] ), .S (n_2197), .Y (n_1063));

What is "\in_a[9]"?

XST gives me:

  wire [1 : 0] \inv/qmul/p ;

What is "\inv/qmul/p"?

Are "\" and "/" even eligible in verilog naming conventions?


texts: Tips for Analyzing Circuit with Transistors

texts: Below is a circuit from a homework problem where I am asked to find the operating points of the three transistors. What I need help with is calculating the base currents for the transistors labeled T2 and T3. Could you please give me some hints as how I can find these currents?


texts: How do I power a LCD Backlight inverter (got from a disasembled LCD screen)

texts:
I have two LCD Backlight Inverters lying around here and I want them to powerup without using any laptop part / motherboards.

I want to power it by using a simple power source, I have both AC and DC transformers available in the 5V to 24V range.

Here are more pictures of the CCFL's I got: http://gz.pxf24.pl/inverter.html

Thanks in advance for your time, effort and help!

If anyone knows how to do the wiring/connecting I will be really happy.

Edit:

Here are 2 HQ photos:

Click to enlarge

Click to enlarge

Finally got it working thanks to the answer below, here is a picture:

If you want to connect it acording to the picture in the answer, you need to look at the BACK of the inverter and connect the following together:

1,2,6 to + , all others to -, take an adapter which is exactly 4.5 volts DC.

UPDATE 2:

I experimented a bit and only 2 needs to be connected to the + and 4,5 need to be connected to - and that's enough to get this running!

However no joy for the other inverter, maybe it's broken.


texts: Sensing doorbell directly off the secondary of the bell transformer, with an ESP

texts:
New here, and not so skilled, so be kind to me...
I've got a very simple electric, old fashioned "ding-dong" doorbell, that I'd like to migrate to the 21st century.
It's basically a transformer (230 Vin, approx. 18 Vout), and the coil of the bell is connected to the secondary via the doorbell switch. You press the switch, the coil moves to the 'ding'; you release the switch, and it hits the 'dong'.
My goal is to have a 3V3 pulse coming from here, so I thought: Let's put a rectifier bridge across the switch, feed an optocoupler with that (no idea what type/model, I'm new to this!) that works on 3V3, and take the output of the optocoupler to the ESP and it's software from there.
I really don't know if this would work, and I also don't know how to hook up the optocoupler to the ESP to detect the pulse.
Would any of you be so kind to help me forward a bit, so I can try to buy the correct optocoupler and not blow up either my ESP or my doorbell?


texts: How to rename several Net Labels in Altium Designer?

texts:
I am using Altium Designer 16.1 for a project which has about 6 thousands of components, so I have many Net Lables(at first I designed a small circuit in a schematic page then by copy and paste I create the whole project).
I used Annotate Schematics option in the "Tools" menu to rename the components, Is there any option to rename the Net Lables automatically like annotate option?


texts: I have A = [-1 0;0 -1] B = [1;1] and C = [t^2 1] To study observability, I can't use rank (C;CA) here due to time-variance. However, it seems, for controllability, we can still use rank (B AB). If this is because C has no impact on controllability, isn't there a conflict because the system is not strictly time-invariant?


texts: Power consumption problem in high-voltage power audio amplifier

texts:
I have a problem with my power audio amplifier.

I am unfortunately forced (because of the specifications I have been given) to make it work at a dual voltage of +-90V.

Finding the components to do it was not difficult, I built it, I balanced the currents of the whole amplifier and now it is perfectly stable at that voltage.

The problem, however, I have in the final stage:

My drivers are, as you can see, KSC3503 and KSA1381, and the power transistors are 2SC5200 and 2SA1943.

The problem: the amplifier is current and thermally stable. But the power transistor power dissipation is too high. For only 10W of output in 8 Ohm I have to dissipate 24W of heat. I tried to increase the resistance of degeneration (0.1 ohm even up to 47 ohms), but the problem is not solved: what the transistors should dissipate, the resistors dissipate. Did I forget something somewhere? I should be able to deliver about 200W with this amplifier, but I can't dissipate 480W of heat. (P.S. variate R89 does not solve)


texts: Effect of feeder length in microstrip patch antenna

texts:
Summary of the question : Why reflection coefficent changes with microstrip feeder line length ?
Explanation of the question:
I'm working on re-simulating this paper : Microstrip Patch Antenna Array Design
The model and simulation done but claimed S11 parameters did not matched with the simulation. Here first picture is design from conference paper and second picture is the version with longer feeder line. Internet search like this claims that feeder length does change anything, just width and thickness is important. But as seen in third image, (blue curve is for short feeder length and red curve is for long feeder), it has very big effect on reflection. It may be mistakes on the conference paper or something else but I want to learn why the feeder length has effect on S11 parameters. Any explanation or reference would be great.
Thanks in advance !
Design Parameters :
Substrate : 1.6mm thick, FR-4 with epsilon_r = 4.3
Conductor : 0.035mm thick, Copper(Annealed)
Ground Plane : 0.035mm thick copper
Frequency : 4GHz
Simulated with CST Studio Suite, Frequency Domain Solver

*Note that there are some changes on patch size but they are out of the question, they only effect center frequency and my question is valid for this situation too. (I simulated without changing patch sizes and S11 parameter still changed with length of microstrip feeder line)


texts: Best way to connect to a really small berg connector

texts:
I am using the cc2520emk to interface with an external mcu. I know the pinout of each but I do not know how to make a good connection with my MCU. THe mcu is not the issue. I can stick in Bergs and use a breadboard to prototype. The problem is the cc2520 which has really small berg connectors. I really dont know how to connect them or what these bergs are called. I am attaching a snapshot of how they look so you guys can tell me what berg to buy. In the parts list it says
P1          SMD pinrow socket, .050 spacinSMD_SOCKET_2X10 . So does that mean a berg connector with 0.05 inch spacing will fit correctly?


texts: Bidirectional data bus divided into nibbles not returning correct data - 8051

texts:
Since I have 10 I/O lines connected between two microcontrollers (AT89C4051 + AT89S52), I am trying to get away with elegant data transfer. Instead of spending months redoing an entire circuit board, I'm trying to divide the 8-bit port into two nibbles so I can achieve bi-directional data transfer as well as being able to skip the step of tristating and waiting.

Except somewhere in my code, something is wrong. I managed to transmit the data from the master to the slave and the data is recognized, but when the slave returns its data back to the master, the value returned is incorrect. In this example, the master is supposed to send the value 5 to the slave, and then the slave is supposed to respond back with the value 9, but instead the slave returns the value of 15 (0Fh). I know this because I used the hexadecimal routine (included in the code snippet) that converts the returned value to hex.

I feel there is something obviously wrong in my code but my brain is fried. What can I do to make this code work?

;Port is organized as: rrrrssss where:
;r= 4-bit data received from master
;s= 4-bit data sent to master

;Master begins with this function
test59:
  mov A,#05h ;set output to 5
  lcall uCdat ;process
  lcall printhex ;print result to screen in hex
  ;Expecting A=09h, but always getting A=0Fh. why?
ret

;mini micro issues a 4-bit command to big micro
;then waits for a reply
;Low nibble of accumulator = data to send
uCdat:
  orl A,#0F0h ;Make high nibble tristate
  mov D,A     ;Send XXXXdata to port
  clr ACT     ;Tell remote were ready
  jb ACK,$    ;Wait till remote is done
  mov A,D     ;Get data
  anl A,#0F0h ;High nibble is output
  swap A      ;Make it low nibble
  setb ACT    ;Tell remote were ready
  jnb ACK,$   ;Wait till remote is done
ret

;Function takes input as accumulator and prints out "xnn " where n=hex character
;Example. if A=#0ABh, then xAB is printed.
printhex:
  setb NIBNO
  mov R7,A
  mov A,#'x'
  lcall cout ;each call to cout prints a digit on serial line
  mov A,R7/swap A
  nextnib:
    anl a,#15
    add a,#246
    jnc phexb
    add a,#7
    phexb:
    add a,#58
    lcall cout
    mov A,R7
  jbc NIBNO,nextnib
  mov A,#' '
  lcall cout
ret

;Slave starts with this function
get5send9:
  ;Stall until we receive a 5.
  test1:
    lcall miniuCdatin
    jc test1 ;if C=0, then remote lowered ACT line and we have data.
  cjne A,#05h,test1 ;Input must be 5 to proceed
  ;Send out 9
  mov A,#09h
  test2:
    lcall miniuCdatout
  jnc test2 ;Stall until data is sent out
  ;All this is processed, but apparently 0Fh is returned to master instead of 09h
ret

;Slave calls to get data from master
miniuCdatin:
  mov C,ACT ;Check action
  jc noUdat
    mov A,D    ;receive XXXXdata from port
    anl A,#0Fh ;get request into low nibble
  noUdat:
  mov ACK,C ;Acknowledgement = Request state
ret

;Big slave then processes data then calls this to give result.
miniuCdatout:
  mov C,ACT
  jnc noUdat2
    swap A     ;make output high nibble
    orl A,#0Fh ;Tristate lower nibble
    mov D,A    ;send dataXXXX to port
  noUdat2:
  mov ACK,C
ret


texts:
Are terminations required for DDR3 in point to point designs? I saw a reference design that doesn't include any termination to VTT for a controller/single DRAM design (pt to pt). DQS, DM and DQ use ODT feature, however Address, Command, Control and Clock do not have the same ODT selection. None of these lines have termination resistors either. It is a working reference design, however I am unsure as to how and why the lack of termination is permissible in this case. Differential clock doesn't even have parallel termination.
I was not able to find any online source to indicate whether it is ok to leave point to point design unterminated (not counting ODT which is available for data/strobe/mask). If anyone could please refer me to a link/document I would greatly appreciate your help.


texts: Why do rubber duck antennas have this metal part, while other antennas do not?

texts:
If you open up a rubber duck antenna, it usually has a wire inside, plus a crimped on piece of metal, like this:

Other antennas, like those on an RC receiver do not have this second metal part:

Both of these antennas are 2.4ghz, why does one require this metal part where the other does not?

Also, if the metal tube forms part of a dipole, then how is it electrically different than the shield it's covering? I think they're connected. Wouldn't it do nothing that the shield isn't already doing?


texts: Manufacturer doesn't list self resonant frequency

texts:
To put it simply, some manufacturers don't list their inductors' self resonance frequency.

I'm a bit baffled as to why they don't do this, and I have some concerns using inductors like this one on high frequency switching applications such as DC to DC converters, as they typically use frequencies in the order of hundreds of kHz, some even a few Mhz.

The only spec they list for that particular inductor is "Frequency - Test" of 1kHz. What does this mean? Will there be any problems if I use this inductor on a DC to DC converter switching at a frequency of, let's say, 100kHz?

I suspect the reason for this omission is the type of inductor, toroidal in this case. Do toroidal inductors have such a low parasitic capacitance that its effect is not noticeable even at very high frequencies, and manufacturers don't even bother to list it? Or is it the opposite, and manufacturers are expecting designers to only use them at very low frequencies?

And whatever the case may be, how does the parasitic capacitance of toroidal inductors compare to other types of inductors?

Also, maybe I shouldn't be using these type of inductors for stuff like SMPSs? If so, what kind of inductors should I be using? What if I need high power, and thus high current handling capabilities?

Any help would be immensely appreciated.