texts: Methods to measure inductance with high (1%) precision using standard equipment?

texts:
I am modeling the fine behavior of interacting oscillatory circuits. I have looked up a couple of methods for measuring inductance. I believe I am following the procedure faithfully, but the values I obtain aren't as precise as I expect. This is, in principle, an elementary question, but ideally I'd like precision of 1% or less and I don't believe I am attaining it with the methods I can find. I have a Tektronix 1001B oscilloscope and a pretty standard signal generator.

First: Is a precision of 1% with this equipment unrealistic?

If not, I have followed the procedure for measuring inductance with a sinewave here: https://meettechniek.info/passive/inductance.html (I also tried the method where you tune the frequency until the inductor voltage is half the total voltage).

I measure across two inductors in series; as a sanity check I also did both inductors separately. L1 is the kind of inductor that looks like a resistor (see the green thing in the photo below); Lcoil is a coiled inductor (see below). The nominal values are L1=220 uH and Lcoil=100 uH, so I expect a total of roughly Ltot=320 uH. All measurements are with f=95kHz because that is the frequency of operation.

R_s=100 Ohm gives Ltot=290, L1=174, and Lcoil=122 (L1+Lcoil=296)
R_s=56 Ohm gives Ltot=259, L1=174, and Lcoil=98 (L1+Lcoil=272)

Are these the best numbers that I can expect? The coil value changes by over 20%, and the total value varies by ~10%. I do not have an electronics background, so if there are some basic intuitive principles I am overlooking, please let me know!

Edit: I add a screencap of one of the calculations, which provides the values of the inductance and the inductor resistance.


texts: Basic CAN-BUS circuit - what does this section do?

texts: I'm currently learning how to make a circuit for CAN-BUS communication and came across the schematics of the Sparkfun CAN-BUS shield for Arduino (can be found here). I'm a little puzzled by this section that shows a 100 ohm resistor and a 560 pF capacitor going to the ground from CANH and CANL lines of the MCP2551 transceiver. The other circuits I've seen do not have this, what is it's purpose?


texts:
Constant current sources (simply, current sources) are useful and necessary devices. They are widely used to drive LEDs, charge capacitors and batteries, to bias differential amplifiers, etc. The only problem is... there are no such devices in nature; almost all of sources are (constant) voltage sources. So we have to make them.

Many specific circuit solutions of current sources are discussed in other questions. But it is interesting to see the general ideas on which they are based… the “philosophy” behind them. If we know it, we will be able to understand completely unknown circuit solutions… and even to create new specific current source implementations.

So what are the basic ideas behind current sources? How are they implemented in practice? Why are they implemented exactly in such a way? What do active elements in these circuits do? What functions do they perform?

I would like not only to know specific circuit solutions... I want to understand them... to see the idea behind them... "the forest for the trees".

Intuitive and imaginative explanations are welcome.


texts: Does every node on a CAN bus just keep transmitting data no matter what or does it only transmit data when it is "requested" to by other nodes on the same bus?


texts:
I recently encountered a battery that was installed in a vintage lawn mower. The battery was dated 9/19 but would not start the engine, it would not even cause the relay to click. The voltage on the battery terminals is 12.04 vdc. So I grabbed a different 12 volt battery and installed it. It started right away.

I put the battery on the shelf and hooked my charger to it. After a few hours of charging nothing changed so I checked further - the battery is a calcium battery. Does that explain any of what I am seeing? The battery has zero capacity at 12 vdc, is there anything I can do or should do with it? The warranty was 6 months - now expired.


texts:
I understand that an RCD device helps to provide protection against electric shocks when completing a circuit between Live and Earth wires, where the Neutral and Earth wires are separated before being wired into the consumer-unit/distribution-panel.

My understanding is that the RCD device works by detecting a difference between the current in the Live wire and the return current in the Neutral wire.  When a tolerance is exceeded the RCD device opens the circuit, to prevent further current flow.

Does an RCD device provide any protection if the electric shock occurs between the Live and Neutral wires, given the current will still be returning on the Neutral path?


texts:
I developed a MEMS microphone based audio capturing device and transfer that audio via USB to the PC. I used Audacity opensource software to test my working and found the audio plays well when recorded and I play back the recorded sound but has static/crackling noise during the live stream.

I tried this with various apps but I find this issue only while listening to live streaming audio and not with the recorded audio.

Is there a problem with my hardware designed or the Audacity app. Since the recorded sound is similar to what I expect I think there could be a problem with live stream mode. I tried a few settings on Audacity but still, get the same static/crackling noise.

What could be the issue? How can I fix this problem?

Configuration

Sample rate: 8kHz
Channels: Mono
Format: PCM 16


texts: Single phase 2 wire motor... Can this be connected to household electrical wiring?

texts:
Hi I have a soft ice cream machine which shows as240v but is a single phase motor.  It has a scotch block with two black wires and the earth separate.  Can this be attached to normal uk sockets via a wire and plug?
 Thanks


texts:
I want to find an external antenna, to remove the box and just solder directly
to actual reader board with a built-in PCB CROSS DIPOLE ANTENNA- see those 4 points in the attached image.

I want to improve the gain by that. Is that possible? How? And what e.g. antenna to use to solder it to those 4 points?


texts: Voltage-controlled current source with gain limit

texts:
I'm trying to design an amplifier circuit that acts as a voltage-controlled current source. I have found some topologies online that uses a shunt resistor together with active feedback and this is fine for the implementation.
I was wondering however whether it would be possible at all to design such a circuit with a voltage gain limit. This circuit would then limit the current if the voltage reaches a certain value.
Important to note is that it concerns an AC signal with a frequency of around 87.5 kHz.
The circuit should then have the following requirements:

A voltage amplitude of 2V at the input should represent a 160mA with a linear transfer.
If the output voltage reaches above 2V the gain should be limited to 1. So the output amplitude should stay 2V regardless if the current has reached 160mA.

I realize that clipping would be some sort of solution for this problem, but I was wondering whether you could do this in a way that the output would not be distorted?
Thank you for your answers


texts: Why am I 1 digit out, when calculating space from two addresses?

texts:
My STM32F407 microcontroller datasheet states that my flash region is between the following addresses:

0x08000000 to 0x080FFFFF

I want to calculate the amount of flash, which I know is 1024KB, but when I try to prove this, I always get to 1023. Here's my math:

0x080FFFFF - 0x08000000 = 0x000FFFFF
                        = 1048575
                        = (1048575 / 1024)KB
                        = 1023KB

Inversely...

1024 * 1024 = 1048576

Why am I confused with 1 byte? Dumb question, and I know this is high school stuff...


texts: Problem with a Relaxation Oscillator (using Op Amp)

texts:
I'm studying a relaxation oscillator. This wikipedia circuit shows exactly my circuit with the only difference that I'm using different values for each resistor.

I called resistor R the one connecting the inverting input of the op amp and its output, R1 the one connecting the non inverting input of the op amp and the ground and R2 the last one.

I've used an oscilloscope to measure the frequency of the output wave. The strange fact is that I measure frequencies always lower than expected. I calculated the expected frequencies using this formula:
$$
f = \frac{1}{2RCln(\frac{1+k}{1-k})}
$$
where
$$
k = \frac{R1}{R1+R2}
$$
Can anybody explain me why I'm always getting lower frequencies than expected? I also tried to change the resistors and capacitor values but I got again lower frequencies than expected. I'm using a TL081 op amp, resistors that go from 500 ohm to 46k ohm and capacitors that go from 45 nF to 1.7 microFarad.


texts: "Fast" pulse (8µs) low current (10µA - 100µA) amplification for optocouplers

texts:
I got this problem where a inverted pulse of 8µs has to be amplified because the pulse only delivers 10-100µA. The signal will be transmitted over a optocoupler and sent to a mc that interrupts upon receiving the signal. Delay from sensor to mc is acceptable down to 100µs and a longer pulse is acceptable.
The ampere meter fuse was blown the ampere was calculated like:

(Vin-Vled)/R=(1.7V-1.2V)/5600=90µA

The reason why Vin was 1.7V was because the current limiter in the pulse generator was pulling the voltage down. With no resistor at all the voltage was roughly 3.3V.

This current has to be amplified to atleast 10mA, but preferably 20mA at 3.3V from the pulse generator to gnd.

Circuit without amplifiers

simulate this circuit – Schematic created using CircuitLab

I tried using a mosfet but the speed was to slow. I also tried the same setup with a npn transistor:

simulate this circuit

By adding the npn we got the current higher, but only up to 1mA and the voltage was still lower than 3.3V on the pulse generator.

How would you fix this? Should i add another npn, limit the current through the first one to maintain 3.3V? Use a NOT gate? Find another npn with higher current gain? Also i do not want it to be complex since i need to make roughly 20 of these for the pcb.


texts: Are external hard drives designed to be protected against electrostatic charge?

texts:
Looking at the conditions in which external hard drives are used, do the drive makers make them with protection against electrostatic charge? Does the outer casing protect it against electrostatic charge?
When my external was shipped, it was shipped in a simple clear plastic bag and a cardboard box. So i guess it is a yes but not quite sure.


texts: Does connecting batteries in parallel increase the current?

texts:
I was watching this video about potato batteries: http://www.youtube.com/watch?v=FITxr6bJmd8

He ends up connecting them in 3 pairs (parallel) of two (in series). This way, by connecting them in parallel, the voltage is not increased but the current is.

This confuses me. V=IR, so the resistance is what determines the current, given a constant voltage. So wouldn't it be more beneficial to connect them all in series, to get the voltage as high as possible?


texts: Arduino vs Microprocessor vs Microcontroller

texts: What is the difference between an Arduino, a microprocessor, and a microcontroller? I'm trying to determine what is best to operate a cheap resistive touch screen.


texts: Material dispersion in fiber optics transmission

texts:
In plain English, why does material dispersion increase with wavelength in fiber optic transmission? I am aware that refraction index decreases with wavelength increase, i.e. pulse travels faster, but why is dispersion proportional to wavelength?

I am referring to the figure at http://www.fiber-optics.info/fiber_optic_glossary/material_dispersion .


texts:
I plan to use a pair 5.5x2.1mm DC Power Jack as shown below to connect a battery pack to a DC motor that will drive an electric tricycle. Occasionally it may rain while the tricycle may be in use and I want to make sure there is no risk of shock.

When plugged in, there is about 2-3mm of the male pin exposed. I will definitely house the battery pack, which are basically two 4x18650 battery holders fixed together, within a plastic container or special case. However, in case water gets in contact with the connection (mostly rainfall and not submerged), will there be a chance of short circuit or shock?

The positive of the male pin will be on the inside and hence the connection does not complete. Also what about the terminals where I screw in the wires? I guess, at least for that I can use electric tape.

EDIT:

It is a DIY, but not a prototype, rather a toy. It will not be stored outdoors, and if it rains when used, should be quickly moved below a shelter or indoors. That said, 99% of the rain falls on four known months of the year. Voltage is 15-16V.

In such an environment, would it suffice if I housed the battery in an inverted plastic container and have the wires run from the bottom? I still need to figure out how to waterproof the motor, but that's another question.


texts: I was wondering about if it’s possible to use different thickness’ of copper on a pcb as a measure to refrain from using resistors.


texts: Serial bi-directional (one-wire half-duplex) digispark device works however answers itselfs

texts:
I followed this guide to create an one wire bi-directional (debug) device for a Digispark (Attiny85):

https://digistump.com/wiki/digispark/tutorials/debugging (see section Bi-directional Serial Debugging with a single I/O) or see schematic in sourcecode below:

/*
  https://digistump.com/wiki/digispark/tutorials/debugging

                        SERIAL SINGLE I/O
                         DEBUGGING CABLE
            ___________________/\__________________
           /                                       \
                                              ____
 .--------.                                  |    \
 |    GND |--------------------------------+---o5  \
 |        |                           47K  | |   9o |
 |        |                        .--###--' | o4   |
 |  DEBUG |                  4.7K  |         |   8o |
 |  TX_RX |-------------------###--+--|<|------o3   |    ---> To regular RS232 SubD 9 pins Male of PC
 |   PIN  |        ^               | 1N4148  |   7o |         or to RS232/USB adapter
 |        |        |               '-----------o2   |         Connector PIN 2: RX (receive)
 '--------'        |                         |   6o |         Connector PIN 3: TX (transmit)
  ATtiny85       Single                      | o1  /
 (Digispark)      I/O                        |____/
                                          SubD 9 pins
                                            Female

 Note:

    Trick to be less intrusive: use a �high� data rate (38400 is fine)
      -> less time wasted in ISR and for transmitting each character.
    You can still upload your sketch modifications through the USB interface
    whilst the additionnal serial port is selected as Serial port in the IDE.

*/

#include <TinyPinChange.h>
#include "SoftSerial.h"

#define DEBUG_TX_RX_PIN         3 //Adjust here your Tx/Rx debug pin

SoftSerial MyDbgSerial(DEBUG_TX_RX_PIN, DEBUG_TX_RX_PIN, true); //true allows to connect to a regular RS232 without RS232 line driver

void setup()
{
  MyDbgSerial.begin(9600); //After MyDbgSerial.begin(), the serial port is in rxMode by default
  MyDbgSerial.txMode(); //Before sending a message, switch to txMode
  MyDbgSerial.println(F("\nDebug enabled"));
  MyDbgSerial.rxMode(); //switch to rxMode to be ready to receive some commands
}

void loop()
{
  if(MyDbgSerial.available())
  {
    MyDbgSerial.txMode();
    MyDbgSerial.print(F("\nReceived: "));MyDbgSerial.write(MyDbgSerial.read());MyDbgSerial.print(F("\n"));
    MyDbgSerial.rxMode();
  }
}

The 'device' I created looks like this:

Doublechecking this pinout to be sure (female -> male):

The 'device' works but answers itselfs, there is something wrong (schematic?). For example: When you enter "hello" in the serial monitor, it replies directly with the same "hello" also without a Digispark attached/connected. When Digispark attached/connected, the Digispark seems to receive nothing.

So what could be wrong, is the schematic correct?


texts: Connection STM Nucleo expansion module to STM 32 NUCLEO

texts:
I want to connect a STM I-NUCLEO-LRWAN1 Expansion module to a STM32 Nucleo  microcontroller.

However, there are no documentation on how this is achieved:
http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-eval-tools/stm32-mcu-eval-tools/stm32-3rd-party-evaluation-tools/i-nucleo-lrwan1.html

Are there some general rule with expansion modules? Do they simply fit ontop of the MCU?


texts: What is the low limit of today's power supply voltage generation and voltage amplitude of sinuosid generation?

texts:
Voltage is not really generated, current is, but let me use this colloquial term. What is limitation for generating electrical voltage very low (DC power supply)? What voltage is the real low limit just above 0?

Also if one wishes to generate a sinusoid function of very low amplitude above 0, what is the limitation of that amplitude?


texts: Serial communication between two devices with seperate logic levels

texts:
The question is more about the DC-DC converter and baud rate between two separate logic level UART devices.

My master device operates at a 3.3v logic level, while my slave operates at a 1.8v logic level.

My proposed solution to allow communication between the two devices is to pull down the tx line of the master device to ground and get 1.8v from 3.3v using a simple voltage divider. To get my slave tx line back up from 1.8v to 3.3v, a simple boost pmic.

The devices communicate at a baud rate of 921600. Is my solution viable? And if so, what considerations must be made about the specs of the resistors in the voltage divider and the pmic boost converter?

Thank you.


texts: Understanding source and return current flow on PCBs

texts:
I'm looking for advice and tips related to PCB board layout and signal+ground trace/track routing.

I'm designing a 2-layer analog-only PCB that has several I/O signals leading to and from other boards and several analog amplifier ICs. I have some questions about how careful and extensive I need to be when routing ground tracks to carry the return current, and how I can best arrange these on the board to reduce noise and hum (EMF) pickup. I'm using star grounding and no ground plane on the board.

From what I have generally come to understand, you want to run signal and return tracks close to each other. To me this seems the same logic used when running interconnect cables off the PCB, e.g. between boards or equipment. On the PCB, I'm unclear about what happens with signal currents, especially when ICs are involved. For instance, I try to run a ground return next to the signal track from the board edge where the I/O connector is located back to the star ground system, but it's not always possible to run this signal+return pair all the way up to where the signal trace connects to a pin on the IC. Should this be of much concern for an analog (audio) circuit? Likewise, is it good practice to try to keep signal+return together for tracks that go between ICs on the same board? If so, how do I figure out where the return current is flowing? For instance, does the current "return" to the ground pin of the first IC, or does it flow back to the star ground system?

Does it make any sense to run a "spur" ground track, meaning one that runs along the signal track but then stops where the paired signal track reaches an IC pin, e.g. that end is left disconnected. The other end would be connected to the ground system. I can't convince myself that this would be effective as a "return" and current would flow, since one end is disconnected. Are dead-end tracks ever used, e.g. for shielding?

I have not been worried about this in the past, and I have designed boards that seem to have acceptably low EMF pickup, etc. but I have always been curious about on-board routing issues like this. I'm completely self-taught so any words of advice would be very much appreciated. I have read several PCB design guideline type documents that I could find on the web, but none seem to address this particular issue - low noise analog signal routing. Maybe its just not all that important?


texts: Is there a transistor comparison chart or database to be found?

texts:
When picking a transistor, I usually start with my supplier's catalogue and search and refine according to the specs I am most interested in. However, I seem to often come out with odd choices. For example I recently needed an NPN for basic switching of a 200mA current using an MCU, and ended up picking a BC337. It seems to work, however it also seems to be categorised as an 'audio amplifier' rather than a 'general purpose' or 'switching' transistor and so I can't help think I could have made a better choice (or maybe it doesn't matter). Likewise, I have a big bag of BC548's that I use a lot, because I happened to have one in my first 'beginners' set, and as it usually worked I just stuck to that regardless of if it was the best choice.

I think I would find useful a simple chart with the most common types, and their characteristics, that I could print off and have to hand to simply look up a suitable type. Google searching has found a few charts from the 60s, a few books (at ridiculous prices, nearly as out of date) but not a simple 'picker' or 'comparison chart' that I can find.

Can anybody recommend one? Or is there a simpler method for picking? Or does it really matter what the 'type' is if I'm just using it for switching (as I always am at the moment, as I'm only doing digital circuits so far)?

Maybe a better simpler question is...how do YOU go about picking a transistor for a switching job?


texts: İ am currently working on a smart shoe( Dont ask why...) and I am using a 3.7 V 300 mAh li po battery with no drop out during transmissin. But the battery life doesnt last as long as I need it to be. So I am planning to use piezoelectric generators to charge it (they produce 4V s and 2 A all together). But I am not really sure if this will work or how it is gonna work. I was thinking that it would work like a garden light, when there is no energy produced from solar panels, it will use from battery. But as I said, is this possible or efficient. If no is there a better solution?


texts:
I'm looking for a way to switch an USB device's power (a mini waterpump) digitally. I've found some solutions, however I'm not sure what are the advantages/disadvantages of the different approaches, so I'd like to ask your opinions and which is the best to use.

Solution 1:
Using transistors similarly to this

Solution 2:
Using a 5V LDO with shutdown pin

Solution 3:
Using a dedicated USB power switch (e.g. TPS203x)


texts: Norton resistance: dependent sources problem

texts:
So imagine that I have a circuit that only contains a resistor in parallel with a dependent source of current. The resistor has a resistance of
$$3 k\Omega$$ and a current I. The dependent source of current has a current of 2I.
Now I want to know the Norton resistance of this circuit.
The correct answer is $$1 k\Omega$$

However I'm not getting there.

My attempt

Because $$R_N = \frac{U_0}{I_{sc}}$$

I attempted to calculate both. However I'm getting to a voltage of 0V. I might be thinking incorrectly. What I'm thinking is that well the resistance and the source have the same voltage which is equal to the voltage I want to obtain. So $$U= RI $$

Considering my node

$$ I + 2I = 0 $$ so I = 0 and the U = 0. I might be assuming something wrong, if someone could please clarify me. Thanks!


texts: I am trying to get the ECAN functionality working on a dsPIC33. I have two identical dsPIC33s, each with identical CAN transceivers connected by a short (3 inch) bus. One is transmitting, one is receiving. However, I see no messages, I just see a repeating waveform with a period of 34.5us. Does this suggest a particular error condition on a CAN bus?


texts:
I have to design a power supply with the LTC1707. It have a enable input to control it.
Now I have to enable an disable this switching supply with a push button.

Only when I push in button during five second, enable = 1.
And if I push a button during five second again, enable = 0.

I have made a schematic with a Flip Flop, but it is instantaneous, i need five seconds.
Is it possible to make this function without microcontroller ? Do you have any idea?

Thanks, sorry for my english...

EDIT:

Thanks a lot for your help! After some research and test on Proteus, i have made a smallest schematic ! :


texts: LIS2DH12 Watermark and Overflow Interrupts at the same time

texts:
I'm working on a project that uses the LIS2DH12 accelerometer by ST (product page). I have a couple of questions about it, and as it is quite a common part, I wonder if anyone here knows the answers:

I would like to know if it's possible to activate two interrupts, watermark and overflow, in the same pin. I tried to set them up, enabling latching interrupts in INT1 in CTRL_REG5 and setting both watermark and overflow in CTRL_REG3. When I get a watermark register, I read INT1_SRC, but that returns 0 (I would expect it to return 0x80, interrupt active) and it doesn't clear the interrupts. I don't know if the overflow interrupt ever kicks in, as I can't clear the watermark without reading the FIFO (I would expect that by enabling latching interrupts, I could clear the interrupt by reading INT1_SRC, and then leave the samples unread to trigger the overflow interrupt).

In case somebody is asking why would I do this, I'm a bit paranoid, and don't want to miss an interrupt and end up losing data. Also, I know that I have a second INT pin, but I can't use it at the moment.

//Setup code

// set increment bit so we can write to multiple registers with one SPI command
accel_transfer_buf[0] = LIS2DH12_REG_CTRL_REG0 | LIS2DH12_MULTI_BYTE_RW;  //The register address will increment on every write
// CTRL_CFG_REG0
accel_transfer_buf[1] = 0x10; //Magic word of the CTRL_REG0, it needs to be that.
// TEMP_CFG_REG
accel_transfer_buf[2] = LIS2DH_settings.tempEnabled;
// CTRL_CFG_REG1
accel_transfer_buf[3] = 0; //Don't write to ctrl1 yet, as that will turn the accelerometer on, do it as the last step in the config
// CTRL_CFG_REG2
accel_transfer_buf[4] = 0; //Disable High pass filters, see AN5005
// CTRL_CFG_REG3
accel_transfer_buf[5] = LIS2DH12_BITS_I1_WTM; //Interrupts enabled in INT1 pin: watermark
// CTRL_CFG_REG4
//Block data update enabled(AN5005), big endian, accelerometer range, normal mode 10bit, 4 wire SPI
accel_transfer_buf[6] = LIS2DH12_BITS_BDU | LIS2DH_settings.accelRange | LIS2DH_settings.HiResMode;
// CTRL_CFG_REG5
accel_transfer_buf[7] = LIS2DH_settings.fifoEnabled | LIS2DH12_BITS_LIR1; //enable fifo, interrupts latched
// CTRL_CFG_REG6
accel_transfer_buf[8] = 0; //No int on INT2 pin (it's disconnected anyway). Interrupt polarity set to active High
// REFERENCE
accel_transfer_buf[9] = 0; //Reference for interrupts

[...]

//Later on...
accel_transfer_buf[10] = LIS2DH12_REG_FIFO_CTRL_REG;
accel_transfer_buf[1] = LIS2DH_settings.fifoMode | ((FIFO_THRESHOLD - 1) & 0x1F);

[...]

//and finally
accel_transfer_buf[0] = LIS2DH12_REG_CTRL_REG1;
accel_transfer_buf[1] = LIS2DH_settings.accelSampleRate | LIS2DH_settings.HPLPmode | LIS2DH_settings.zAccelEnabled | LIS2DH_settings.yAccelEnabled | LIS2DH_settings.xAccelEnabled;

When I get an interrupt, I do

accel_transfer_buf[0] = LIS2DH12_REG_INT1_SRC | LIS2DH12_READ_REGISTER;
uint32_t errorCode = SPIDRV_MTransferB(spi_handle0, accel_transfer_buf, accel_transfer_buf, 2);
checkErrorCode(errorCode, "DEBUG");
debug_logln(VERBOSE, "Accel Int: 0x%02X", accel_transfer_buf[1]);

And I would expect to get 0x80, but I get 0x00 (and there are no errors in the transfer).

1) Do you know if what I'm doing with the latched interrupts is correct?

2) Do you know if what I'm trying to achieve with the two ints in the same pin is possible?

Thanks!


texts:
https://www.utvinc.com/switches/utv-inc-back-lit-dual-blue-dpdt-on-off-on-vertical-turn-signal-switch/
I want to use a few of the switches in the link above. They are double pole double throw and rated at 20 amps. I want to know if that is 20 amps on one side or 20 amps combined.
I want to run 12V electric fan override by flipping the switch to lets just say the up position.
I am thinking if they are 20 amps on one side I can wire both poles separately, run that wiring into two 25amp fuses and then combine the wiring at a 40 amp relay to send 40 amps continuous to the fan.
Unless they are 20amps combined then my plan will not work and I will be overloading the switch.
If I use two of the DPDT poles can I increase my maximum current rating?
OK I was thinking of it backwards. Above is how I am going to wire the switch using it as a ground interrupt.
Thank you for all the help.


texts: If I ground the base of a NPN transistor (which means no current is passing through the transistor) with a VCE limit of 60 V, can I connect a higher voltage than its rating to collector of the transistor?


texts: Is Gauss's law still valid near the speed of light?

texts:
When the speed of the charge is close to the speed of light, is Gauss's law still valid?
As far as I know, the invention of Gauss's law preceded the theory of special
relativity, so if the answer is yes, then why is Gauss's law still valid when the speed of the charge is close to the speed of light?


texts:
I'm trying to reduce this circuit into 1 resistor and the current source. The dots indicate nodes, which I'm not sure makes a difference...

Can I combine R1, R2, and R3 in series, then, R4 and R5 in parallel?

Then can I combine those two resistors in parallel (assuming that they are parallel)?


texts: Value of resistor to protect against short circuit

texts:
I have a FPGA and a async-sram with OEn, WEn that I want to interface.

To protect against short circuit I want to set resistors on the data lines.

What is the value that would protect the FPGA and SRAM but would still leave the design functional?

Voltage level is 3.3, the FPGA is a Zync 7020 the SRAM is a IS61LV5128AL.
I want to transfer at 25-50Mhz.

Would i.e. 20 Ohm be sufficient to protect the FPGA and SRAM pads to get too hot in case they both try to drive the signal in opposite directions?


texts:
I have the following closed loop transfer function:

$$G(s) = \frac{K(s^2 + 200^2)}{0.05s^3 + (1+K)s^2 + 200{K_v}s + 200K}$$

Where \$K\$ and \$K_v\$ are gains.

My goal is to find the optimal gains in order to have a settling time under 0.5 seconds and as low as possible overshoot.

Using Routh-Hurwitz I obtained the following constraints:

$$K > 0$$
$$Kv > \frac{0.05K}{1+K}$$

Is there any suggestions how to find the gains?

Thank you.


texts: I am looking for a 40 input OR gate which minimize PCB space

texts:
I am using 40x ICs INA301 to measure overcurrent in 40 interfaces
Finally I want to have 1 single "output" to signal if there is an overcurrent in ANY of the 40 interfaces
I don't want to utilize any uC for minimizing cost.
I am right now using multiple 4input OR gates (cd4072, but I want to know if there is any clever circuit or IC that might do this minimizing PCB space/cost.
Thanks in advance.


texts:
I have two brands of broken HDMI cables that I need to join to make them longer.
Can't join them by color, because they are completely different. Plus, one of the cables has all the wires, the other floats some of the pins.
So,
What are the most fundamental pins to transmit audio and video between PC and TV ?
Does the shield/shell have to be connected or is it optional ?
Wikipedia treats the pins as "data", but that doesn't tell me anything, even though I know digital image and video are data.
I would connect all the available wires, but it's quite difficult in my case here. If one is not important, I intend to leave it.
Edit:
Let me make an additional question, if there's still time:
How can the HDMI I have here work normally (at least before it lost one of the endings) having only 14 wires ?
It is missing wires 2, 5, 8, 11 and 13
There are 5 extra/individual shields, but the multimeter is not picking them on those missing pins.


texts:
I would like to make a parallel circuit with two resistors to most-closely resemble how a 'graph' would look, for example:

However, when I try doing something like this in Everycircuit it fails (though it works if the - side of the battery terminal is also connected to ground). For example:

A couple questions here:

Is my drawing a valid circuit? Or is it not valid until the 'negative side of the battery is grounded' ?
If it's valid, why doesn't Everycircuit accept that? Are there any other circuit programs that would accept it? I have an easier time understanding circuits when drawn closer to the top drawing than in the 'box-like' schematics.


texts: Reduce voltage after AC-DC rectification before step-down

texts:
I have a Weller Magnstat soldering station providing 24V AC to the tip. I want to use that output to power a 12V fan to disperse or absorb the fumes.

With a cheap multimeter I measured 25V AC during heating and 27.1V AC when idle (I suppose the voltage will get lowe after some minutes of use).

The maximum rectified voltage would be about 36-37V after a bridge rectifier. This is too high for a linear regulator (0.25A*(37-12)=over 6W heat). I thought about a DC-DC step down ready-made circuit, one based on the LM2596 and cheaply available from China.

However, they are rated often at 35V, some of them 38V (the caps are often 35V anyway...), and the regulator is rated at 40V max itself.

Provided I find one with 50V caps (that however look as big as the 35V ones, I hope they are not fake), would it be reliable to use such circuit to provide the 12V, or should I reduce the voltage further?

If I want to reduce the voltage, are 2 diodes (1.4V) in series before the regulator the best choice, or is there a better alternative? If the fan absorbs 0.25A (max, less during normal use) a resistor to drop 5V would dissipate about 1.25W. I could put a smaller one and dissipate only 4V, 1W. At partial load (fan slower), the voltage drop would also decrease.

Another option is a LM317 set to a voltage drop of about 5V, but I'm not sure using an IC for this purpose makes sense: a resistor or a diode cost much less.


texts: USART in SPI mode vs. SPI hardware speed

texts:
On AVR ATmega devices, the USART has the capability to function in SPI mode (i.e. synchronous with no start or stop bits). The chief operational difference is that the TX line (i.e. MOSI) has a buffer, while the SPI hardware MOSI has no buffer. According to this Atmel application note (http://www.atmel.com/Images/doc2577.pdf), this buffer makes it possible to continuously transmit data. This is in contrast to the SPI hardware where SCK must be halted while a new byte is being loaded into SPDR.

With this in mind, which of the following programs to transmit 200 bytes from a buffer buf[200] would complete in the shortest amount of time? (Assume that all are configured at fosc / 2.)

Polled SPI:

for(int B = 0; B < 200; ++B)
{
  SPDR = buf[B]; // Load next byte into SPDR
  while(!(SPSR & (1 << SPIF))); // Wait for SPIF to be set
  (int)SPDR;  // Read SPDR to clear SPIF
}

Interrupt-driven SPI:

ISR(SPI_STC_vect)
{
  if(B < 200)
  {
     SPDR = buf[B]; // Load next byte into SPDR
     ++B;
  }
  else
  {
     SPCR &= ~(1 << SPIE); // Disable SPI interrupts
  }
  return;
}

Polled USART in SPI mode:

for(int B = 0; B < 200; ++B)
{
  UDR0 = buf[B]; // Load next byte into UDR
  while(!(UCSR0A & (1 << UDRE))); // Wait for UDR empty
}

Interrupt-driven USART in SPI mode:

ISR(USART0_UDRE_vect)
{
  if(B < 200)
  {
     UDR0 = buf[B]; // Load next byte into SPDR
     ++B;
  }
  else
  {
     UCSR0B &= ~(1 << UDRIE); // Disable UDRE interrupt
  }
  return;
}


texts: Transformer coil (reactor) inductance value in AC (El type)

texts:
I want to use one of these inductors (EI type transformer coils with air gap) in series to a speaker (woofer) to filter out high frequencies.
https://www.hammfg.com/electronics/transformers/choke/195-196

simulate this circuit – Schematic created using CircuitLab
Of course this will work inside the loudspeaker in AC and with low average currents and in absence of DC, but the datasheet specifies the inductance "at rated max DC current".
Can I assume in my first-order filter schematic (to determine the frequency response -6dB cut-off curve) the same inductance shown in the datasheet (labelled on the transformer)?
If not, how can I determine the correct inductance value in AC (without DC) of the inductance of a transformer coil whose inductance is specified at "max DC current"?


texts: ADIF is set first or ADSC is cleared first?

texts:
I am using an ATmega8A for ADC conversion. I start ADC conversion by setting ADSC bit and wait till it clears by hardware to detect the end of conversion. I saw some people checking the ADIF bit to detect the end of conversion.
ADCSRA |= (1 << ADSC); // start ADC conversion
while (ADCSRA & (1 << ADSC)) ; // wait for the end of conversion

or
ADCSRA |= (1 << ADSC); // start ADC conversion
while (!(ADCSRA & (1 << ADIF))) ; // wait for the end of conversion
ADCSRA |= (1 << ADIF); // clear the flag

Of course, both of them work fine; I want to know which one occurs first, ADSC=0 or ADIF=1? And which one is better to use? The datasheet says "ADSC will read as one as long as a conversion is in progress. When the conversion is complete, it returns to zero." about ADSC and "This bit is set when an ADC conversion completes and the Data Registers are updated." about ADIF. Does that mean the value of data registers may not be updated right after ADSC is cleared?

I ask all of these because if I use checking ADIF to detect the end of conversion I had to clear it and this means one extra word in the flash memory and one extra clock cycle in program execution in comparison with just checking ADSC.


texts: Finding the equivelent capacitance of the circuit

texts:
Finding the equivelent capacitance of:

simulate this circuit – Schematic created using CircuitLab

I think that it should be:

$$\frac{1}{\frac{1}{C_1}+\frac{1}{C_2}}+\frac{1}{\frac{1}{C_3}+\frac{1}{C_4}}$$

Am I right?


texts: Current flow from pull-up resistor in MCU

texts:
According to the circuit diagram here, when the switch is on, the current directly flows to the ground, but shouldn’t it split at the junction and some of it go to the MCU, as well as the ground, if so then I don’t think MCU will give LOW as output?

I may have some mistake in understanding the concept of pull-up resistors.


texts:
What is the difference between PCB fabrication and assembly? Some companies like Golden Phoenix list that based on the size of PCB, it outputs a quote.

Mine was 2.1 x 1.6 inch. It outputted 29 pieces for $100. So it means if I give them my schematic and PCB layout and pay them $100, I will get 29 pieces of production-ready PCBs ready to sell?

Now one company, EPS, lists fabrication and assembly differently. In assembly, it states I ought to provide the parts. In fabrication, anything but about parts is stated.

So what are these companies suggesting?


texts: Transmission Line Voltage Terminology Confusion (Very Basic)

texts:
I have a issue interpreting what transmission line voltage actually means (I have tried researching but nothing clearly explains in detail, just says its a 110kV line etc).For example if i have a 220kV transmission line, and this transmission line is modeled by short line approximation (hence admittance is negligible), is this 220kV what is being received (for VR). I assume not as then the sending end voltage would be higher than 220KV due to line losses hence i am confused to what this 220kV entails.

Instead is this 220KV essentially like the middle voltage of the line? As in the line wants to have voltage that is around 220KV, thus is it just a guide? However the actual sending end voltage could possibly (most likely) be higher than 220KV and the receiving end voltage be lower than 220kV, i.e. constantly varying based upon the load recieved.

Therefore when a question or someone states "thats a 220kV or thats a 110kV line", is that value essentially what the lines voltage will be maintained around, i.e. it could be higher than 220kV or lower than 220kV but it wants to see pretty much 220kV? Like a middle guide basically for the line?

Thanks in Advance


texts: Determine characteristics of unknown choke

texts: I'm stripping some parts off an unused DSL filler since it's easy desoldering and it's got decent film caps. I've also got a couple of 4 lead inductors, probably common mode chokes. How can I figure out the important specs for them? I've got a scope with FFT, multimeters, a couple of dds waveform generators (good to about 20MHz I believe). Probably won't get tolerances and maximum voltage/current but I figure I should be able to get inductance, impedence, and resonance frequency?


texts: LM317 construct 3volt output and 2amp output

texts:
I am doing a project using 6 stepper motors. These motors have different operating voltage and current. For example, one requires 3.6V and 2A, another one requires 2.4V and 1.2A. The 6 stepper motors operating in different voltages and current, so I purchased a 12 Volt 2 Amp transformer, (6 numbers) and a LM317. I also purchased a stepper motor L298 H bridge driver.

Now my doubt is how to reduce the voltage from 12V to 3V using the LM317? I don't need to reduce the current. I need 2A 3V output from my transformers. Please help me.


texts:
I'm trying to wirelessly connect two modules: XBee PRO S2C and XBee S2C.

Although it seems like they're connected in the software:

Serial messages between them don't go through and neither do the range test packets.

Both have the same (latest) firmware on them.

Any ideas of what might be wrong?


texts:
Assume we have this circuit:

simulate this circuit – Schematic created using CircuitLab
At t=0s we decide to close the switch, then current will start flowing through the circuit and around the inductor a magnetic field will be induced.
My questions:
According to Faraday's law, the electric voltage generated on a coil will depend on the change of the magnetic flux through the coil. Since the magnetic field grows at a constant rate shouldn't the back emf of the inductor remain the same? Why does it have the form it does?


texts: How do i find suitable power source given component specs

texts:
If i am aware of the specs of electrical components in a project like for example in mine i am using 4 dc motors with the following specs for each:

Operating Voltage Range: 3~7.5V
Rated Voltage: 6V
Max. No-load Current(3V): 140 mA
Max. No-load Current(6V): 170 mA
No-load Speed(3V): 90 rpm
No-load Speed(6V): 160 rpm
Max. Output Torque: 0.8 kgf.cm
Max. Stall Current: 2.8 A

based on this information how would i calculate or find a suitable battery capacity or amphour delivery to power the four motors?
What i mean is how would calculate the specs of a suitable battery that i can use.


texts: What does it mean when something "drops voltage"?

texts:
You quite often read that a part "drops voltage". What exactly does this mean?

That if there is 9V on the one side of the part, and it drops 3V, that there are only 6V left on the other?


texts: How can I protect my SMPS feedback voltage divider from loading effects?

texts:
Background: I now have a working switched mode boost converter on a breadboard, working as a 12 Volt DC to 24 Volt DC converter. I was troubleshooting what looked like an output voltage problem when I noticed that my meter was actually just changing the feed back path to the controller IC, causing it to stabilize at around 18.5 Volts; I confirmed this with a x10 probe on a handheld scope.

simulate this circuit – Schematic created using CircuitLab

The question then: how does one go about protecting the feedback path from a change in its ratio? Are there any clever tricks, or do I just need to use larger value resistors? What would a pro do?


texts: Why deliberately mismatch impedances in RF?

texts: My professor wants me to design a cascaded RF amplifier, with mismatched stages. The reasoning is to increase bandwidth. Is this correct? If so, can anyone elaborate on the theory why mismatching increases bandwidth?


texts: What options are there for good Low DC Voltage, High Amperage Alligator Clip connections?

texts:
I have a 12V DC, 20A compressor for my offroad vehicle to inflate its tyres after driving on the beach. I also have high current jumper leads with large alligator clips at each end for starting cars with a flat battery. The compressor has flying leads with bare copper ends. What options are there for a solid connection (without the risk of a short circuit) if I want to power my compressor from the car battery using the jumper leads?

Here is a diagram of the setup:

One option is some high-current jumper terminals, but these are quite costly.

I could possibly make my own out of a block of wood, and two bolts.

Does anyone have any other ideas or advice?


texts: 12VDC Fan rated at 0.08A only drawing 0.04A, can I increase current draw in order to bring the rpm up?

texts:
I've built a small desktop fume extractor for soldering.
It uses a 120mm 1000RPM, 12V, 0.08A case fan. Not huge, but it does the job.
The fan is only drawing roughly 0.04A and I have been fault finding and theory checking all afternoon and I can't figure it out and I feel like such a fool now, I should know this.
The fan is powered by a 12V DC 1.5A supply.


texts: Why can't electronic systems use constant current power source and vary the voltage as power consumption varies?

texts: Today, electronic systems use constant voltage power source. Current consumption varies as power consumption varies. Why can't electronic systems be designed the other way round? Using constant current power source and varying the voltage as power consumption varies. What are the pros and cons of each approach? Why has current electronic systems evolve to use constant voltage power source?


texts: Ultra-low Power DC DPDT Switch: Does It Exist?

texts:
I'm working on a circuit for an ultra-low power microcontroller and two configurations are given for RFO HP and LP to operate in low and high power modes respectively. I tracked down an application note for using both and they recommended using DC switches (or solder bridges for a static configuration) and presented the diagram below.

The design already includes this load switch and I was hoping to find something similar but for toggling a connection instead of interrupting it. The image below shows my ideal solution.

I have been searching for a similar ultra-low power IC but haven't even been able to find any SPDT switches, let alone DPDT.
Does this device (or another low power solution) exist?


texts: In a robot, I need to use a (24 volts 5-7 amp) DC motor, which should be controlled by a microcontroller. Now, will I get a motor driver IC for such a motor? If not, what kind of circuit will help? I am new in robotics, so I will be very thankful for any diagram with explanation.


texts: How do we derive the limiting values of a series’ resistance for Zener diodes with varying load and varying input conditions?

texts: Is there a mathematical derivation for finding the limiting values of series resistance in a voltage regulator circuit with varying load and varying input conditions ?


texts: How many mV ripple in DC is okay for powering an ATTINY?

texts: I need to power an attiny85 from an MC3306A, and in order to calculate the values for the circuit I need to know the ripple I desire, what ripple mV is alright for an attiny to happily chug along?


texts: Blocking and nonblocking statements for counter

texts:
Is there any difference between nonblocking and blocking assignment for the following counters?

module  nonblocking_counter (
  input clk,
  input rstn,
  output reg[3:0] out
);

  always @ (posedge clk) begin
    if (! rstn)
      out <= 0;
    else
      out <= out + 1;
  end
endmodule

module  blocking_counter (
    input clk,
    input rstn,
    output reg[3:0] out
);

  always @ (posedge clk) begin
    if (! rstn)
      out = 0;
    else
      out = out + 1;
  end
endmodule


texts: Tradeoffs between QPSK and BPSK re. spectral efficiency, error rate, etc

texts:
Say I'm using binary phase-shift keying (BPSK) to transmit some data at some rate. Now say that I want to double the data rate, without increasing my transmitter power. I could either continue to use BPSK but double the rate, or I could send two bits per symbol at the same rate by switching to QPSK.

Either will double the data rate, but what tradeoffs are being made? If I understand correctly, QPSK will use the same spectrum as BPSK at the same symbol rate, provide twice the bit rate, but the bit error rate increases as the transmitter power is now divided between two bits per symbol. But how does doubling the bit rate, but continuing to use BPSK change things? I expect it will use more spectrum; what of the error rate?


texts: How to solve BJT amplifier clipping a signal?

texts:
I'm trying to make an audio amplifier for an 8 ohm speaker. I'm new in electronics area and having a problem with it.
I already had other issues before arriving where I am, like the need of a high power stage because the low impedance of the load.

To the high power stage my tentative after some reading was to use a transformer at the transistor collector to match the low impedance of the speaker with the high impedance of the amplifier output.

The first problem were, if I use an 9V DC source for biasing the transistor, the voltage at transformer primary will float at maximum in 0 to 9V (In an extreme case). So, if the speaker can work at a maximum peak to peak voltage of for example 6V, the ratio n1/n2 should be at the maximum 1.5, because the peak voltage at secondary will be 9/1.5 = 6V. Is that a right reasoning?

Going ahead, if I use a transformer with 1.5:1, the impedance seen in the primary will be 8*(1.5^2) = 18 ohm.
So the configuration of this stage of the amplifier would be like this:

The transistor is biased with 4.5V at emitter resistor, 4.5V at collector-emitter (Vce), and the voltage at the primary is almost 0V for DC.
The capacitor at emitter has low impedance and it's almost a short circuit for AC.
So, in my mind, the voltages will vary from 0V in the primary and 9V at Vce, to 9V in primary and 0V at Vce (in an extreme case).

But when I run it, these waveforms appears. Yellow curve represents the input voltage (250 mV peak), and purple is the voltage at the primary of the transformer (not the output). It have a positive peak of 130mV, but at the bottom seems not to be what I expected. The curve is being cut out at -20mV. It doesn't should saturate only in a relative high voltage, next to the 9V of CC source?

What is wrong and how can I solve this?

EDIT:

I have changed the bias of the transistor for a collector current of 50mA, with a base resistor of 27k instead of 1.35M. Also removed the emitter capacitor (which really reduced the distortion) and changed the emitter resistor to 10 ohm. The clipping has went away for these low input voltage (250 Vpk), and the voltage at primary is apparently a perfect senoid, with amplitude a little higher than the input voltage. But if I increase the input voltage to 3V peak, the clipping reappears at the bottom. I still can't figure out why this happens.

EDIT 2:

I'm adding the image of the waves for the last update:

the clipping voltage has increased, but it is still happening. It starts to appear at about 1V peak at the input.

And I don't know if I have made it clear but this is the end stage of my amplifier, with a low gain, only for drive the speaker. I'm making the stages separately for easy understanding of each part. As this stage has a high input impedance I will use a common emitter before for high gain of voltage.

And sorry for my bad english :(

EDIT 3 (solved):

The problem was the transistor must be biased with a collector DC current of at least the same value that the peak to peak current which load requires.
Other thing I noticed is that the BC548 I was using fails with a relative big current (>200mA) even in the simulation, the base-emitter voltage increases significantly, also making the wave to clip.


texts: Degenerated common source output resistance by inspection

texts:
In Razavi's Design of Analog CMOS Integrated Circuits (2nd edition), on page 65 he describes a way to derive the output resistance of a source-degenerated CS stage by inspection:

I understand how to derive this result from the small signal model but I don't understand the reasoning/intuition behind the inspection analysis.
He starts off by saying that if you apply a \$\Delta V\$ at the drain and measure the resulting \$ \Delta I\$, then all the \$ \Delta I \$ must pass through the degeneration resistor \$R_S\$. Sounds good, since the current has nowhere else to go.
He then derives a voltage divider equivalent circuit as shown in the linked image. However, he uses the result that the resistance looking into the source of a MOSFET is \$ \frac{1}{g_m+g_{mb}} \$ to insert a resistor in parallel with \$ R_S \$, which I don't understand. My confusion is that the resistance looking into the source of a MOSFET is derived when you have an ideal independent source applied at that terminal and calculate the voltage/current ratio (typical Thevenin resistance). How is that scenario applicable here? This analysis started off by saying that all of the \$ \Delta I\$ must pass through the resistor \$ R_S\$ but the model derived in figure 3.30(c) seems to imply that some of it is going through this other impedance.
(A side-doubt that I have is that here \$ \lambda \$ is not assumed to be zero since \$r_o\$ is finite but in then in this case resistance looking into the source shouldn't be exactly \$ \frac{1}{g_m+g_{mb}} \$, not sure if that makes a difference here.)


texts: Fast bidirectional 3.3 to 5V level shifter

texts:
For a hobby project of mine, I'm thinking about connecting some old 5V SRAM chips like this one to a 3.3V - capable FPGA. The target frequency is 50MHz. After some simulator experiments I found out that a simple voltage divider could work:

simulate this circuit – Schematic created using CircuitLab

This gives a nice 0.2..3.0V peak to peak signal on the 3.3V side when driven by 5V side. In the opposite direction however, the output signal is only 0.4..2.6V peak to peak, which is kind of within the spec for a W24512AK (\$V_{0H}=0.8V\$ and \$V_{1L}=2.2V\$) but the margin isn't great. I wonder if this will work at all in practice.

So I'd like to improve the margin by using an active level converter, but as far as I can see, all simple schematics (e.g. the ones listed here) have a terrible frequency response. The only viable solution I see is to buy some TXB0108 which can reach 100Mbps at 3.3V.

Is there a level converter schematic I have overlooked? As such, it doesn't have to be truly bidirectional since the \$\overline{WR}\$ signal is accessible and can be used to enable/disable shifters in each direction.


texts: Do Twisted Nematic LCD need refresh (polarity reversal)?

texts:
The Wikipedia entry for the history of the LCD during the 1970s and 80s, states that twisted nematic (TN) field effect LCDs were available in the 1970s. Later, in 1983, super-twisted nematic (STN) structure for passive matrix addressed LCDs was invented.

From Passive and Active-matrix, it is stated that STN requires constant refreshing:

  STN LCDs have to be continuously refreshed by alternating pulsed voltages of one polarity during one frame and pulses of opposite polarity during the next frame.

whereas, apparently, the TN appears not to require refreshing, see the description of Twisted Nematics. Without wishing to quote the entire description, there is no mention of refreshing, or field reversal:

  A voltage of about 1 V is required to make the crystal align itself with the field, and no current passes through the crystal itself. Thus the electrical power required for that action is very low.

So, assuming that the Wikipedia entry has not omitted something, with TN LCD was the refreshing mechanism required or not?

As an aside, if it was not, why then was it required for STN?


texts: General "rule of thumb" for unused IC pins

texts:
This is somewhat similar to this question about NC pins. In cases where the datasheet doesn't specify what to do with unused IC pins, what is the recommendation to do with these pins? In particular I'm thinking of GPIO pins for the AT32UC3C microcontroller, but also more generally for other IC types (for example multi op-amp IC's).

I can think of a few possible combinations:

Provide a solder pad/hole so the chip is secured but leave pin floating.
Connect the pin to ground (possible through a resistor/capacitor/etc.)
Connect the pin to a supply source
Something I can't possibly think of


texts: Why is pin diagram of 7402 NOR gate reversed as compared to other gates?

texts:
The following is a picture of pin design of 74 series TTL IC Family logic gates taken from this site:

We observe that in every logic gate, the input pins are (1,2), (4,5), (9,10), (12,13) and output pins are (3), (6), (8), (11) but in case of 7402 NOR gate, the input and output pins are reversed i.e. input pins are (2,3), (5,6), (8,9), (11,12) and output pins are (1), (4), (10), (13). Why is this so? Why is the pins reversed in case of 7402 NOR  gate? The following picture clearly depicts what I am trying to say(taken from this datasheet):

Is it due to structural planning, stability or some other reason?The I couldn't find any reasoning on the internet  and need some help. Also, what would happen if we connect NOR gate as we do in other gates?


texts: How to cut the circuit when power is back, join otherwise

texts:
I have a fan which runs on 220V AC power supply.

When the power is there, I use my air conditioner and don't use the fan.
When the power trips, I want to turn on the Fan automatically using the Inverter.
I have an on/off switch which stops this automation entirely if it is off.

Have a look at the circuit diagram, I tried to draw the situation in that.
So I was developing a circuit but all the solutions are using some kind of a battery. Is there any way to solve it without a battery? Or If battery is necessary, can you help me with a simple circuit to accomplish this.


texts: Running baseband analog audio signal over cat 5 cable

texts:
What will happen to a single ended (not differential) 1Vpp analog audio signal(4khz bandwidth, not modulated) if it runs through long cat5 cable (length can be 50 meters)? How much signal voltage can drop? Can there be any change in frequency?
What will happen if the input signal is differential (say 0.5Vpp signal in each differential line)?


texts: Finding equivalent resistance of a resistor network

texts:
In the circuit below, all of the resistors are 15 Ohms. I am trying to find the equivalent resistance between A and B.

Can we argue that since RAD/RDC = RAO/ROC that AODC is a wheatstone bridge and thus say no current will flow through DO and remove DO from the circuit? Using the same argument, can we remove BO too?

Can we then just simplify the circuit like below and then find the equivalent resistance using the series and parallel rules?


texts:
I've seen in a lot of projects a cool presentation of byte such as :

      Fuse high byte:
      0xc9 = 1 1 0 0   1 0 0 1 -- BOOTRST (boot reset vector at 0x0000)
             ^ ^ ^ ^   ^ ^ ^------ BOOTSZ0
             | | | |   | +-------- BOOTSZ1
             | | | |   + --------- EESAVE (don't preserve EEPROM over chip erase)
             | | | +-------------- CKOPT (full output swing)
             | | +---------------- SPIEN (allow serial programming)
             | +------------------ WDTON (WDT not always on)
            +-------------------- RSTDISBL (reset pin is enabled)

or

    Fuse low byte:
     0x9f = 1 0 0 1   1 1 1 1
            ^ ^ \ /   \--+--/
            | |  |       +------- CKSEL 3..0 (external >8M crystal)
            | |  +--------------- SUT 1..0 (crystal osc, BOD enabled)
            | +------------------ BODEN (BrownOut Detector enabled)
            +-------------------- BODLEVEL (2.7V)

I wonder if anyone can tell me how, or where, I can make some of these ?

edit : I mean, I often see those type of presentation in texte format, so I suppose it isen't made by hand. I was hopping to find the software/url to generate the samme.


texts: Motor controller voltage dropping to zero when under load

texts:
I'm having a problem with my KBMD DC motor controller. When no motor is connected, it puts out 0-90V, depending on the speed dial.  However, when I attach my 1/40hp 90V DC motor, the voltage drops to zero and the motor won't move at all. I tested the motor and it's working fine. Any ideas as to why this is happening?

As per Kevin's recommendation, I adjusted the CL trimpot until the LED turned off. The voltage was still zero when the motor was attached, and it did not run. I hooked up an identical motor that was allowed to spin freely, but it too did not work. Interestingly enough, the ammeter pulled a current of 6A when attached in series to the controller and motor, but the motors are rated at .36A. However, I attached each to an 18V drill battery, and they seemed to operate correctly with no bindings or stalling. I used an identical motor controller for a few months before it went out, so I think they should be compatible. Any suggestions?


texts: Mp2307 what is the maximum output current?

texts:
On the datasheet says minimum Upper Switch Current Limit at minimum duty cycle is 4.0A (min) 5.8A (typ).

How can i calculate the maximum output current? It will be higher or lower than 3A?


texts:
I'm a computer scientist with zero exposure to things directly related to hardware (barring what I learned from my undergrad computer org class.)
I've been very attracted to the field of embedded software and computer engineering, and I've been trying to find a class/lab where I can learn and practice the fundamentals of circuits and electronics.
Regarding the theory, I can learn that from books, and I have a few. Or I can take some undergrad courses from a local university (offered both within brick walls and in distance learning format.)

The problem: Labs
However, the problem is the practicum, the labs. The closest university has the labs during the day. The other local university has lab classes at night, but they are too far to drive. As a working software developer, then I really have no options to sign up for a lab class to get my hands dirty.
What would be the value of learning from books (or from classes) if I don't get to a lab? The stuff they do at EE labs (the typical electronics lab I class), is that something I can learn on my own? If so, how?
I'm trying to close this skills gap I have in front of me and get more into Computer Engineering. The last thing I want to be is a paper tiger with all theory and no practice. But the labs are always during times of the day that conflict with my work schedule.
Any advice?


texts: Proximity IR Sensor Circuit using TSOP VS1838 output problem

texts:
I am assembling a proximity IR Sensor using TSOP instead of Photodiode. I followed the diagram below. When I tested the circuit, and put my hand close to the IR LED. The receiver receives the signal in just one second. From 0.7v to 5v instantly. How can I make a low output constantly if my hand is close to the IR LED? Please tell me what is wrong. I am using a TSOP VS1838b as the receiver and an IR LED using 555 ic transmitter operating at 38khz frequency.

Reference https://forelectronics.wordpress.com/2014/05/09/tsop-based-ir-sensor/


texts: What is the use of V ref pin in a differential amplifier?

texts:
What is the use of Vref in a differential amplifier?

Will it keep the output below V+=5V (from 0 to 5V) or will it keep the output below reference voltage (Vref) =3V (from 0 to 3V?)

What does unidirectional ground reference output, and what is unidirectional V= referenced output?

i refered Google i got some results but iam still confused. kindly help me clearing my confusion?


texts:
I'm aware the same question has been posted before, but unfortunately, it has not led me to an answer.

I have a small PCB in which I've added an LDO to convert input voltage to 3.3 V output voltage.

The LDO in using is the AP2210-3.3TRG1 (datasheet).
My understanding from the datasheet is that with an input voltage of 4.3 V - 13.2 V. (4.3 V because the manufacturer recommends Vout + 1 V).
I'm supplying 9 V input voltage from a battery.

My schematic is as follows:

simulate this circuit – Schematic created using CircuitLab

I'm expecting to get 3.3 V as output voltage.
When I measure the output voltage, however, my multimeter reads only 0.5 V.

I've gone through the datasheet to see if I've misunderstood or missed something, but I can not manage to figure it out. There's also some stuff I do not really understand, which doesn't help.

So some concrete questions.
Do I have some mistake in my schematic?
Am I misunderstanding how to use this component?

I hand soldered the part on a PCB (with hot air), is it possible I overexposed it to heat?

UPDATE

Thank you all for your answers!

Some additional information:

The load is an ESP8266 (datasheet). I've measured the current at the LDO output, which is ~135 mA.

When I measure the voltage at the same spot I get 1 V now.
In the original post, I reported reading 0.5 V, but I must've been mistaken since nothing has changed and now I get a solid 1 V (which is still lower than expected).

In regards to "Power Dissipation"; I get the following results (as per page 23 of the LDO datasheet):
(150°C - 25°C) / (0.135 A × 200°C/W) + 3.3 V = 7.93 V

This is a lower voltage than I'm supplying. Can this be the issue?
The datasheet says:

  Therefore, for good performance, please make sure that input voltage is less than ...

I'm going to find a 5V power source and see what happens!

Results
I supplied ~4.8V and measure the following values at Vout:

85-90 mA

0.7-0.75 V

I also feel the LDO is getting significantly hotter now, but I've not verified that.

UPDATE

Adding a screenshot of the board design.

resistors on top layer are 10k ohm resistors.

C1 is a 1 uF cap and C2 is a 2.2 uF cap.

U1 is an ESP-12F


texts: Converting from time domain to phasor domain?

texts:
If I have a voltage source of a circuit
\$V_s(t) = 8\cos(24\pi*10^9t-60^{\circ})\$ (V)
and I want to convert it to the phasor domain would it be this?
\$8e^{-j60^{\circ}}\$?


texts: How to convert block diagram in to circuit schematics

texts:
I want to design an electrical circuit for my project.

l am not good at making circuit schematic, but I am good at assembling block diagrams.

How can I convert a block diagram into a circuit design by using software? If it is not possible what are the basic knowledge I must have to draw schematic?  for example this is the block diagram that I want to convert so what I have to do?


texts: How to power up arduino and two 6v motors with 12v LiPo efficiently?

texts:
I have a 12v LiPo battery, arduino mega and two 6v dc motors (which will be powered by a motor shield). Although arduino can be powered using 12v, i don't want to do it because a lot of power will be wasted as heat by the regulator. Is there any way I can provide 6v (or 7v) to the board without using linear regulators? And switched regulator circuits look too complex for me.

Also I'm planning to give 12v to the motors, but use a low maximum value (150 instead of 255) in PWM to keep them from heating. Is this a good idea?


texts:
I need to build a constant current driver for a LED with a forward voltage of 3.4V and 350mA maximum current. The driver will be controlled by a PWM signal from a 3.3V MCU.

Reading this post and doing the calculations using my system specs, I came up with the following circuit:

simulate this circuit – Schematic created using CircuitLab

I had to choose a 12V power supply due to the high forward voltage of the LED, which resulted in a minimum power supply voltage of 6.5V. Therefore I couldn't use a 5V power supply.

However, I'm concerned about the power dissipation on the transistor. If my calculations are right, the power dissipated across it would be (neglecting base current and considering Vbe=0.7V):

And the BCP56 can only dissipate a maximum of 1.35W with properly sized mounting pad in the PCB.

First of all I would like to know if the my calculations are right and, in case they are, what would be a good solution.

The only two options I can think of are either picking a beefier transistor that can dissipate more power or reducing the power supply voltage, although I like the idea of using as 12V power supply since it's easier to find locally.

Furthermore, is BJT a good solution for this type of driver or changing for a MOSFET based driver a more suitable option?


texts: In this circuit why am I getting a voltage of 3,99V when the voltage source is only 2V?

texts: In the circuit below I have to calculate the values for the voltmeter and the ammeter, in the ammeter the result I got was -0.057 A which is the correct value, but in the voltmeter I can not seem to figure out how to calculate it.


texts: I'm trying to use the nrf24l01 transceiver on altera board de2-115. I would like to send a signal from the altera board using this spi module to another spi module and use the spi module on the receiving side to turn on an LED and a vibrating motor. Does anyone know if this board works with this spi module and how ?


texts:
This is the DC motor of yamaha mt1x 4 track tape recorder.
The motor is not working and i would like to know maybe if i can fix it.
This motor turned for a while and then it totally stopped.

I opened the motor coils look fine to me.

These are the brushes and the circuit.
In the picture there are also voltages i measured when the motor was connected to the tape recorder.

This is the motor when it is in the device.

And tgis is its cap and part number.

The motor disconnected from the device when i power it with 9v it draws 20 mA which is too low i guess.
I am very unexperienced with motors.
Would you point me to the right direction for debugging this motor?
Unfortunately i couldn’t find the datasheet.
also why do i measure the supply voltage on the middle two pins?

Thank you.


texts:
So I want to provide some heating to what will be like a fibreglass bucket and am contemplating adding some nichrome wire between a couple of the layers of fibreglass mat. I would ideally like to achieve this by just by using wire resistance to achieve the correct temperature. Existing requirements are 12.6v power supply, an approximate 65°C temp requirement and an knowledge of someone who did something similar to what I am contemplating and their heater used 25w

So what I have done is from this table, divided the 205°C column by a third to give an approximate current requirement for a given wire size, and then converted this table, to give an Ω/m figure.

I then multiplied the (65°C) required current figures by 12.6v to see what the watt requirement would be, the 16gauge wire came to 26w. Then I divided the 12.6v by the 2.11A (65°C 16gauge wire) to give a total required resistance figure of 5.97Ω then divided that by the by 0.84 Ω/m figure to give a required wire length of 7.11m.

Does this seem right?


texts: LTspice three phase rectifier simulation

texts: I am interested in creating from scratch a regulator rectifier for motorcycle. I struggle to comprehend the ground placement in the simulator. I cannot find instructions about tree phase simulation. The difference between the two is the additional ground that there is on the schematic on the right. I probed different angle phase on each so you can see clearly. In the second case each phase does not go under 0V when in the first case on the left the sine is as expected. Could you tell me how to simulate this properly as eventually when a battery, load and regulator come into play it will be a common ground with the diodes. I guess my error is in the phase representation. I hope my question is clear.


texts: Why does this code for an ADC only return 4095 or 0

texts:
I have set up a voltage divider with a TLC2543 ADC.

Here is the code uploaded to my Arduino.

#include <SPI.h>

const int chipSelectPin = 53;
const int eocPin = 49;

void setup() {
  SPI.begin();
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode(SPI_MODE0);
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(chipSelectPin, OUTPUT);
  pinMode(eocPin, INPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  Serial.println(myVersion());
  delay(1000);
}

uint16_t myVersion() {
  uint16_t ad;
  uint8_t adq;

  digitalWrite(chipSelectPin, LOW);
  while(!digitalRead(eocPin)){}

  ad = SPI.transfer(00001000);
  adq = SPI.transfer(00001000);
  delay(10);

  ad <<=8;
  ad |= adq;
  ad>>=4;

  return ad;
}

Here is the setup on my Arduino:

The known resistor is 10k and the unknown resistor is Rf.

Following the voltage divider formula, v = 5 × (10k / 10k + Rf)

And since this is a 12-bit ADC the value on the serial terminal should show
V × 4095 / 5. Therefore 409610000 / 10000 + Rf.

However, while changing values for Rf, the serial monitor would print 0 if Rf was 0(just a wire), but for any other value of Rf it would print 4095. Can someone tell me why?

EDIT: Rotated Image, I tried adding comments, but i honestly am not sure what I am doing. Also Thanks everyone for taking interest in my question, and Im sorry for the late edit.


texts:
I'm fairly new to electronics, and I'm working on an amp for my guitar. I need to wire a 1/4" audio jack as the input of the amp. The jack has 6 pins and I'm really confused. I found the datasheet (https://www.mouser.com/datasheet/2/18/55010643000111_acjx-ihs-771337.pdf), but I still can't understand it.

I think "R",  "T", and "S" stand for "ring", "tip", and "sleeve", but what do "RN", "TN", and "SN" stand for? And how should I wire it? Thanks for the help!


texts: What elements of a capacitor make it higher voltage and higher capacitance

texts: I know capacitors have 2 plates, and an insulator in between the plates. I am wondering what elements inside of a capacitor make the capacitance larger, and what makes the maximum voltage higher?


texts: Is it okay to take \$\beta=I_c/I_b=98/2\$ in this problem?

texts:
In an npn power transistor the collector current is 20mA. If 98 percent of
  the electrons injected into base region reach collector then the base
  current in mA is nearly ?

Here, in this problem is it okay to take \$\beta=I_c/I_b=98/2=49\$ ?


texts: Raspberry Pi wake-up and battery power circuit

texts:
I am working on a Raspberry Pi (3B plus) project that - at times -needs to operate on battery power, and on external power whenever available. The RPI needs to operate only when a dedicated sensor detects a preset signal level.

To save power, I want to keep the RPi powered off, only to be powered up when a (power savvy) Adafruit Trinket M0 senses the signal-level of interest. The Trinket then activates a relay that connects the RPi to the supply power (be it battery, or external power supply).

When the signal level drops below the level of interest, the Trinket will not power down the RPi, until it receives a 'Safe-to-power-down' from the RPi.

I came up with a wiring diagram, (see picture), but, not being an electrical engineer, I would really appreciate some input. Would it work like this? How can I improve, or change it?
By the way, both switches should be physically coupled, and labeled (BATT - EXT+COMM)


texts: Sharp transistor cut off outside active region

texts:
I'm building a simple temperature controlled NMOS switch for regulating the speed of a fan.
It's a 12V fan and the controller works great (as long as the transistor is in it's active region.)
This is the circuit I'm using, where R2 is the temperature sensor:

However, the fan only turns on at a voltage of ~3V or higher, and makes squeaking noises on anything lower than that. The voltage output vs. temperature (C) looks something like this:

Ideally I'd like it to "cut off" completely when reaching an output below 3V with a result like this (in red):

I want to remove the exponential behaviour when exiting the active region.
Is there a way to "reverse clamp" the gate voltage, immediately bringing it to 0 if it's too low, or is there some other solution to this problem?


texts: My slayer exciter circuit doesn't work properly

texts:
today I tried to make my own Tesla coil circuit according to the schematic below, except that I have changed the number of turns on the secondary and primary so could get a higher output voltage (1 to 500+ turns). That's what I was trying to do. But I have come across a problem. I used Power transistor (BD243C) instead of the 2222A. I wired up my circuit according to the schematic below with red LED, 9V battery but without switch to see if it's at least working.

The circuit doesn't work as expected. My LED didn't light up, transistor is heats up. There are voltage drops in the circuit which I probed but no sign of high voltage output. Can anyone notice something weird and tell me?

Thanks to everyone who post a sensible and helpful answer.


texts:
Anyone very experienced with Modbus & RS-485???

My task is to control a DC motor using micro PIC24.
The motor setting like the angle, delay, start/stop, duty cycle, etc will be sent from PC using Modbus to PIC24.

The system is like this:

PIC24 -> UART -> IC MAX3471 -> RS-485 to RJ-45 converter -> RJ-45 to USB -> PC (running modbuspoll tool)

The Modbus format used is Modbus RTU.

At first, the Modbus read holding register function and write single register function is working. But after I send some of the motor settings using Modbus write single register function then the motor start running, it was then the Modbus communication always timeout error.

And once the timeout error happens, the next time I turn on the system again it will keep giving timeout error.

I've tried changed UART baud rate from 9600 to 115200.
Try changing the RS-485 to RJ-45 converter board (just in case it broke), the phenomena just repeat.

Can someone give me some advice on what could be the possible cause?

Also, I'm not sure about this, in Modbus RTU format, at the start and end there should be 28 bit (at least 3 1/2 character length), but should the micro firmware code care about this since at the PC use modbuspoll tool?

I've tapping the A & B signal using logic analyzer, if I send some character from uC to RS-485 (but not connected to PC), the character showing correctly on A & B line. But if I tapping the A & B line signal when I send read holding register function from PC using modbus poll (give timeout error) I got some weird signal:

So it seems the problem is not in the uC firmware code, but rather either one of them: USB to RS-485 converter, straight ethernet cable, or RS-485 interface board.
Here's the USB to RS-485 converter that I used:

and the RS-485 interface board:


texts: I need to measure current in a small electromagnet powered off 3 x AAA batteries in series. This is the manual for my multimeter. When I run this multimeter in series and try to find the current, the electromagnet doesn't work anymore. I suspect the internal resistance of the multimeter to be too high compared to my electromagnet (just a few coils of 20AWG magnet wire) so the electromagnet isn't getting enough voltage anymore. Is there a cheap/free solution for me to find the current in the electromagnet?


texts: What is the mathematical equation to calculate the RSS or RSSI at a receiver, receiving a signal via single reflection ?

texts:
I have received certain answers on how to use your laptop or WARP or WLAN NIC to get the RSS or the RSSI, but what I'm interested in is the mathematics that is involved in calculating the RSS. Consider a situation as below

L_1, L_2, angle, and the reflection and transmission coefficients are all known, what else should i know so that a mathematical equation can be written for calculating the RSS.


texts: How do I deal with ideal current and voltage sources in my circuits?

texts:
Data given: electromotive force of the ideal voltage source \$E=20V\$, power output of the ideal voltage source \$P_e=3.333W\$, current of the ideal current source \$I_s=4A\$, power output of the ideal current source \$P_i=56/3W\$. The task is to find the resistances \$R_1\$ and \$R_2\$.

So here are the steps that I've taken: \$P_e=E \cdot I\$, therefore, \$I_1=1/6(A)\$, and the resistance at the i.v.s. is therefore 120 ohms. With this we can calculate \$I_2\$, namely it is \$23/6 (A)\$. Then using Kirchhoff's laws, I found that \$R_2 = 1.6 \Omega\$ and \$R_1 = 277 \Omega\$.

I am having a trouble figuring out how deal with these sources, and I am not sure of my answers. When having an i.v.s. do I place the appropriate resistance in parallel with it? What about i.c.s.? In series? I've searched many sites online, but didn't find the explanations I was looking for. We are only allowed to use Kirchhoff laws here. Can you recommend some good, valid sources to learn from?


texts: Why does my 24VDC fan draw much less current than labeled?

texts:
I have three Delta PFB0824UHE, which were provided to me by a customer for a project. They are labeled 0.93A.

When actually hooked up to 24V, the fan draws .45A, regardless of head pressure. This current varies linearly with input voltage, going as low as .2A and as high as .5A across the fan's spec'd input voltage range. I have three units, which all behave the same.

The datasheets I find for this part indicate a current draw of 0.77A.

I’m confused as to how much current I should actually expect this fan to draw. Do fan manufacturers typically allow that much overhead in their specs? Are they subject to manufacturing variations to that degree? Do I perhaps have some special variant of the fan, and not know it? Are they perhaps mislabeled? Should I expect the fan's current draw to increase over time, or with temperature or some other variable?


texts: Impedance Control in Twisted Pairs and PCB

texts:
Why do differential signal traces on a PCB require a reference plane to have a controlled impedance?
Whereas, in an unshielded twisted pair there is no reference, there are only the two conductors?
Thank you for any answers that you can provide.


texts: How to calculate output resistance impadence with using small signal analyse?

texts:
Hello I am trying to understand calculating impadence of a transistor using small signal analysis. In the book I came across with following exmaple.

It tries to calculate Rout.

So I didn't understand how circuit at the left side have equivalent small signal analysis as circuit at the right side.

I mean how Vin transported to emitter as Vx?

I understand that Vin must be grounded for calculating Rout with one port input. But I can't see any relation about Vin and Vx.


texts: Flyback transformer vs neon sign transformer

texts:
I've been working on my spark gap Tesla coil, and I'm planing to use a 5kV 30mA neon sign transformer connected to a voltage multiplier circuit with 10 stages to get a higher voltage.

Could I use the same setup but replace the NST with a 20kV flyback transformer with a strong Mazzilli driver?
Is the flyback more powerful than the NST?


texts: 240V AC to ~380V DC converter at 3500 continuous watts

texts:
I have a single phase 5KW generator connected to a diesel engine capable of producing approx 3500 Watts of power

I need to convert the 240V AC to DC in order to send it to my solar charge controller that can accept anything up to 600V DC.  It then converts it to 48V DC to charge my battery bank.  The generator is 300 feet away from the battery bank and charge controller

I understand that I need to rectify it to get DC, but I also need to smooth the ripples out as much as possible for the charge controller to be happy first.

The charge controller and battery bank are connected to a grid tied inverter.  I will be exporting the power to the grid.  My generator has no ability to sync to grid.

My question is what components do I need (capacitor values) in order to reduce the ripples?  I'd also like to filter out as much AC noise as possible

I appreciate any insight you may have

Thanks for your time

John


texts:
I've been wondering. How hard is it to craft a (digital) watch from scratch?

I'm currently thinking that (with a lot of assumptions) you can buy/import quartz chips or something like that from overseas, and then after putting them on a case, stick them to some circuits, batteries, some LCD display etc.

So yeah, what other considerations could there be, besides manufacturing (cases, straps etc)?

disclaimer: I'm a complete newbie when it comes to electronics, so you probably cringed just by reading that. I'm just curious about this because after trying to shop for a good watch, it seems that there's almost too many choices, and I can't help but wonder how hard is it to get to the watchmaking business.


texts:
I found a circuit online for a 2 transistor noise generator, shown here. However, that original circuit has a capacitor completely bypassing the emitter resistor (many of you who are familiar with single-transistor amplifiers will have seen this). I was afraid that it might lead to a lot of variability in the output voltage due to the high parameter spreads (especially with hFE) that transistors typically have, so to try to combat this, I added R4 into the circuit (producing what you see below) which was not present in the original circuit. This is what I have:

The problem is, how do I determine the range of output voltages at Vout based on R2, R4, R5, R3, and the transistors' characteristics?
Expanded a lot because stupid me forgot to even link the original circuit in my original post :-/


texts: Op-amp and manipulating its linear output range

texts:
First of all let me give some background on the problem. I'm not a native English speaker and I have a basic understanding of amplifiers and op-amps.

I am having trouble with one problem in English where I believe I don't have enough expertise to understand. I would greatly appreciate if anyone could put in different terms and explain to me what is asked and point the way to the solution.

The problem as it follows:

  Design a dc-coupled one-op-amp circuit that will amplify the -100mV to +50mV input range to have maximal gain possible without exceeding the typical guaranteed linear output range.

As far as my understanding goes:

When talking about an op-amp, we have a typical voltage transfer characteristic curve (Vo x Vi), where part of it is (almost) linear. The solution I went after, involved changing the linear region to be entirely in the -100 to 50 mV range. But how to do it?

I searched for quite awhile and the closest I got was a balancing method for a differential amplifier using transistors at the Millman/Halkias Electronics book. So after some time, I started thinking I may be looking at the problem in the wrong way and I decided to ask here.

Sorry about my English, I try to keep it simple. I am a computer science graduate with some engineering background.

So what is exactly the problem asking and how could I solve it?


texts: When do you want an ESBT (emitter switched bipolar transistor)?

texts:
I just found out about ESBTs, which seem to be a hybrid of BJT and MOSFET:

When I googled it most links led to STMicroelectronics, so I think currently they're the only manufacturer.
I noticed that many devices are high voltage (1000V to more than 2000V), and some devices come in rather large packages,

despite being relatively low current (this one is 7A). Must have to do with their application in high voltage (2200V) circuits.

Has anyone used one of these yet? What are the advantages over a MOSFET (besides maybe the higher voltage)?


texts: Negative feedback from block diagram to circuit components

texts:
I can read and understand the block diagrams which show the internal amplifier and the feedback network and I can read and understand the schematics of several single-BJT amplifier circuits, but I have a very difficult time going back-and-forth between the two.  I have been unable to find resources that show how to define loop gain and feedback factor when viewing the schematic, or how to predict component values by looking at the block diagram.  I tried it on my own here hoping that users can help me understand what I'm missing.  My objective was to begin with a common emitter circuit schematic (below right) and use it to derive the familiar equations for the block diagram (below left).  In specific, I'd like my analysis to give me the closed-loop gain, feedback factor (\$K\$), and values for \$v_{in}\$, \$v_f\$, and \$i_{out}\$.  (I use \$K\$ instead of the more common \$\beta\$ because the latter is already used to describe the transistor.)
Is my analysis correct?
NB: I edited this question to correct an earlier error where I neglected \$r_e\$ when calculating voltage gain.

For the circuit above, I applied a test voltage of \$v_s=100mV\$ and the simulation showed an output current of \$342\mu A\$.  If all goes well, I should be able to predict this result using the expressions I find for closed-loop gain.
1. Transconductance
I understand that to properly analyze this circuit I will need to visualize it as a transconductance amplifier, so next I examined the closed-loop gain \$A_f=\frac{i_{out}}{v_s}\$. To get the closed-loop gain, first I'll need some expressions for \$i_{out}\$.  I began with the output voltage, which is easily found with the resistors \$R_C\$ and \$R_E\$.
\$i_{out}=\frac{v_{s}A_V}{R_C}\$ where  \$A_V=\frac{R_C}{(R_E+r_e)}\$.
\$i_{out}=\frac{v_s({\frac{R_C}{(R_E+r_e)}})}{R_C}=\frac{v_s}{(R_E+r_e)}\$
\$i_{out}=\frac{v_s}{(R_E+r_e)}\$
2. Feedback Voltage
Next, I wanted to understand how the feedback network \$K\$ works.  I found a value for \$K\$ by working backwards from \$i_{out}\$.  I know the effect of the internal amplifier \$A\$, so I know that \$i_{out}\$ will be \$g_m\$ times \$v_{in}\$.
\$v_{in}g_m=i_{out}=\frac{v_s}{(R_E+r_e)}\$
\$v_{in}=\frac{v_s}{(R_E+r_e)g_m}=\frac{v_s}{R_Eg_m+r_eg_m}\$
Because \$r_e\$ and \$g_m\$ are related through inversion,\$r_eg_m=1\$.  So...
\$v_{in}=\frac{v_s}{R_eg_m+1}\$
Because \$v_{in}=v_s+v_f\$, I know that...
\$v_s-\frac{v_s}{R_Eg_m+1}=v_f\$
Finally, I can say that
\$v_f=v_s[1-\frac{1}{(R_Eg_m+1)}]\$
3. Defining K, the feedback factor
I know that \$K\$ will have a value in ohms, or \$(\frac{V}{I})\$.  Its effect on the input, the voltage \$v_f\$, will be \$v_f=Ki_{out}\$.  If I use my expressions for \$v_f\$ and \$i_{out}\$ I can find an expression for \$K\$.
\$v_f=Ki_{out}=\frac{v_s(1-\frac{1}{R_Eg_m+1})}{\frac{v_s}{R_E+r_e}}\$
\$K=v_s[1-\frac{1}{R_Eg_m+1}]*(\frac{R_E+r_e}{v_s})\$
I can cancel out \$v_s\$, giving...
\$K=[1-\frac{1}{R_Eg_m+1}]*(R_E+r_e)\$
Reworking, I get
\$K=(R_E+r_e) - \frac{R_E+r_e}{(R_Eg_m+1)}\$
This yields a mess of \$R_E\$ variables:
\$K = R_E+r_e-\frac{(R_E+r_e)}{(\frac{R_E}{r_e}+1)}\$
Which eventually boils down to
\$K=R_E\$.
4. Finding the closed-loop gain
Finally, I plugged in my \$K=R_E\$ expression into the standard closed-loop gain \$A_f=\frac{g_m}{1+Kg_m}\$ equation:
\$A_f=\frac{g_m}{1+Kg_m}\$
\$A_f=\frac{g_m}{1+R_Eg_m}\$
5. To Double-Check
I went back to my original schematic and checked my work.
if \$A_f=\frac{g_m}{1+R_Eg_m}\$, then my \$A_f=\frac{0.12}{1+(284*0.12)}=0.00342\$
If \$A_f=0.00342\$, my output current should be \$i_out=A_fv_s=0.00342*0.1v=0.000342A=342\mu A\$
If \$K=R_E=284\Omega\$, then \$v_f=Ki_{out}=284*0.000342=97mV\$
If \$v_f=97mV\$, then \$v_{in}=v_s-v_f=100mV-97mV=3mV\$
So, the negative feedback \$K\$ prevents the majority (97%) of the signal voltage from reaching the transistor.  The closed loop gain is defined as
\$A_f=\frac{g_m}{1+Kg_m}\$ and the feedback factor \$K=R_E\$
Everything checks out in simulation and it all makes conceptual sense... so, is my analysis correct?


texts: TLV431 based voltage regulator, possibility of exceeding Vka max. at startup

texts:
I need a small (15mA max.) voltage regulator and considering a TLV431 + emitter follower:
This works fine but the datasheet states Vka as 7V absolute max. My input voltage Vi however can be as high as 8.4V (2S lithium ion). During normal operation this isn't a problem because the TLV431 will regulate and keep its cathode at Vo + Vbe, which is well within spec.
I'm wondering about startup tough. Is it possible for Vka to briefly exceed 7V before the TLV431 has a chance to start regulating? Would it be wise to add a 6.2V zener diode in parallel to the TLV431? (During normal operation the zener won't conduct as Vo + Vbe is lower then 6.2V).


texts: Amplify low voltage signal coming from lm35

texts:
I am using a lm35 to measure temperature from a box. The range of output voltage is 0.2V to 0.5V. I need to amplify this signal by 5. I tried using a non inverter op amp configuration with a LM358 and a lm381, but it seems this IC do not recognize this range of voltage, because at the output i get 0V.

Also, I cannot use negative supply and the maximum supply is 12V, so my range is 0-12V. I need to know which op amp to use.


texts:
I'm working on the integration of a sensor into an automotive platform, using a standard 12v negative chassis setup. I am trying to understand a somewhat mythical phenomenon that is experienced known as "ground shift". I haven't been able to explain this, but my intuition suggests this is reasonable.

The way it has been "explained" is as such: two ground referenced points on the vehicle may be held at some different potential for some unspecified amount of time due to some form of interference from neighbouring components, or components sharing a common grounding "stud".

For example, when the ABS is actuated and a significant amount of current (hundreds of amps in some cases) is sunk into a particular ground stud, the grounding point becomes an unstable reference. Other components attached to this stud may experience voltage swings on their input pins.

My question is this: is this phenomenon something that truly exists, or is it simply an internal "old wives tale" with little to no basis?

If it does exist, how can it be characterised, and where can I learn more? What is the fundamental electrical principles at play here?  Can it be reduced to a representative model circuit? Any experiences would be appreciated.


texts:
I have a question about how the PN junction works in a diode.  According to http://hyperphysics.phy-astr.gsu.edu/hbase/solids/pnjun.html:

"Filling a hole makes a negative ion and leaves behind a positive ion on the n-side. A space charge builds up, creating a depletion region which inhibits any further electron transfer unless it is helped by putting a forward bias on the junction."

My question is: why does the filling a hole make a negative ion?  Shouldn't the hole cancel out with the electron giving a neutrally charge ion?  And the  consequently, there would be no e-field created?  I'm not sure what I'm missing here...  Why are there positive and negative ions in the depletion region?  I thought there'd be neutrally charge ions...


texts: Why if I change the sample time in Matlab/Simulink modifies results in a huge way?

texts:
I'm having trouble with the circuit I'm studying but in order to modify some values, I want to get out this question of my mind.

* Example 50e-6

* Example 50e-7

* Example 50e-8

I use a S-Function block in order to get this "triangular" wave, so I'll leave it here in case of:

static void mdlInitializeSampleTimes(SimStruct *S)
{
    ssSetSampleTime(S, 0, INHERITED_SAMPLE_TIME);
    ssSetOffsetTime(S, 0, 0.0);
    ssSetModelReferenceSampleTimeDefaultInheritance(S);

}

static void mdlOutputs(SimStruct *S, int_T tid)

   int_T             i;
   // Corriente Snubber
   InputRealPtrsType u0_Is = ssGetInputPortRealSignalPtrs(S, 0);
   // Triangle Reference
   InputRealPtrsType u1_Iref = ssGetInputPortRealSignalPtrs(S, 1);
   //  Voltaje THY - Lectura voltaje colector/emisor
   InputRealPtrsType u2_Vce = ssGetInputPortRealSignalPtrs(S, 2);

   real_T            *IGBT = ssGetOutputPortRealSignal(S, 0);
   real_T            *THY =  ssGetOutputPortRealSignal(S, 1);
   int_T             width = ssGetOutputPortWidth(S, 0);
   int_T             width1 = ssGetOutputPortWidth(S, 1);

for (i=0; i<width; i++){

       if (*u0_Is[i] < *u1_Iref[i]){
           *IGBT++ = 1;
           if (*u2_Vce[i] >= 0.8 && (*u0_Is[i] < *u1_Iref[i]) ){
               *THY++ = 1;
           }
           else {
               *THY++ = 0;
           }
       }
       else {
           *IGBT++ = 0;
           *THY++ = 0;

       }
   }


texts: How to calculate the Impedance of a circuit

texts:
I am having a problem regarding calculating the impedance of the two circuits below:

simulate this circuit – Schematic created using CircuitLab

Everywhere I search I always get a description of what to do if they are connected in series or in parallell, however no one I have found so far explains how to use both parallell and series to make an Impedance function using the jw method. Would be extremly happy if someone explains the best method of getting the jw impedance function and also what does R1 // L1 stand for in these cases. Why is R1 // L1 often refered to as (R1 * L1) / (R1 + L1) and not (1/R1 + 1/L1) Like regular parallell functions.

The values on the different parts in the schematics are just examples, I would like to know how to make the formula using the signs like R1, C1 and so on.

Thanks in advance


texts: What value does ammeter or voltmeter measures (RMS, Average or Peak )?

texts:
What value does these meters measure?

Is it RMS, Average or Peak value ?


texts: Design a 4-bit binary counter using D flip-flop

texts:
I am learning logic circuit now.I am going to design a 4-bit binary counter with D-flip-flop.It counts from 0 to 15.And when the number reaches 15,the number wont change and remains 15.I am now working with the add function of the circuit,but I cant find where i get wrong.

This is the Truth Table I made.

The Karnaugh Map and expressions of all D and CP

Like you can see,when CP 1 activates Qa,CP2 gets activated due to (Qa !Qb),and CP3 gets activated then and CP4 got activated then.The result gets totally wrong!So can anyone points out my mistake?

Thanks in advance!