texts: Is it possible to connect a 3-wire line without stripping an RJ11 line cord?

texts:
I have a 302 telephone that was manufactured in 5/39 (May 1939). The line cord does not have a four-prong connector attached; the wires are simply cut.

I am trying to get this connected. I have a four-wire RJ11 cable with both tip and ring (red and green) as well as yellow and black. The 302 has only green, red, and black.

I don't really have the equipment needed for stripping cables, nor do I want to. I am attempting to make a head on connection, like so:

The yellow wire is hidden behind the green cable. The twistie ties are just to keep the individual copper wires together and straight. What I would like to do is be able to simply attach the three sets of wires to the RJ11 connector, and maybe tie it together with a larger twistie tie.

Currently, the interior of the telephone seems operational. There is only one unconnected wire as far as I can see, by the rectangular gray thing.

I have been looking at several wiring schematics. One person said to connect green to green and red and yellow to red. A YouTuber had similar advice for a 500. But this was to connect to a two-wire RJ11 cable, and I have a four-wire RJ11 cable here.

I think ideally one would strip the RJ11 cable and then tape the right sets of wires to the wires in the RJ11 cable, but I'm not going to do that. I have been testing various combinations of colors, including G to G and R/Y to R. At the same time, I've been holding the receiver up to my ear but I am not getting a dial tone. The RJ11 cable is a live wire.

Does the wiring combination really matter? Will it not work if the combination is wrong? The wiring inside looks okay, so it's hard to isolate the problem.

The wiring in my 302 does not seem to be the same as the diagram in the answer:

Could the red wire that is disconnected be causing a problem? Red is RING, so will it stop me from getting dial tone also?

When I did tip and ring to tip and ring it did not work:


texts: Calculate the next state for flip flop sequential circuit


texts: Sine wave generator using a triangle wave input

texts:
I'm covering oscillators in my class right now and in the foot notes of my professor's notes he says that there is a "dirty and cheap" trick to generating sine waves. I replicated the circuit below

simulate this circuit – Schematic created using CircuitLab

I don't have any more detail about this and I'm failing to see how this would generate a sine wave. From the looks of it, it looks like a series of tangential approximations but I would appreciate more clarity.


texts:
I'm using SPI for interfacing between STM32F103 and MRF24J40. I write a value to MRF24J40 register and then read back to confirm it works functionally but I only receive 0x00 from MISO pin. Here are my SPI Initialize and MRF24J40 interface

SPI Config:

SPI_InitTypeDef SPI_InitStruct;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);
SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_32;
SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge;
SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low;
SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b;
SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_InitStruct.SPI_Mode = SPI_Mode_Master;
SPI_InitStruct.SPI_NSS = SPI_NSS_Soft;
SPI_Init(SPI2, &SPI_InitStruct);
SPI_Cmd(SPI2, ENABLE);
GPIOB->BSRR = GPIO_Pin_12;                  //Disable SPI slave

GPIO Config:

GPIO_InitTypeDef GPIO_InitStruct;
//Clock providing for SPI peripheral
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

//GPIO config for SCK and MOSI pin
GPIO_InitStruct.GPIO_Pin = (GPIO_Pin_13 | GPIO_Pin_15);
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOB, &GPIO_InitStruct);

//GPIO config for MISO pin
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_14;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOB, &GPIO_InitStruct);

//GPIO config for NSS pin
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_12;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_Out_PP;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOB, &GPIO_InitStruct);

SPI Transfer:

uint8_t SPI_ByteTransfer(uint8_t data)      {
    while(!((SPI2->SR) & SPI_I2S_FLAG_TXE));            //Wait for data transmitted
    SPI_I2S_SendData(SPI2, data & 0xFF);                //Send data to TX buffer
    while(!((SPI2->SR) & SPI_I2S_FLAG_RXNE));           //Wait for data received
    data = SPI_I2S_ReceiveData(SPI2);
    return data;
}

MRF24J40 Write and Read register functions:

void MRF24J40_WriteShortAddrReg(uint8_t addr, uint8_t data)         {
    addr = (addr << 1) | 0x01;              //MSB = 0 for short, LSB = 1 for writing
    GPIOB->BRR = GPIO_Pin_12;               //Enable SPI slave
    SPI_ByteTransfer(addr);
    SPI_ByteTransfer(data);
    while(SPI2->SR & SPI_I2S_FLAG_BSY);     //Wait for bus free
    GPIOB->BSRR = GPIO_Pin_12;              //Disable SPI slave
}

uint8_t MRF24J40_ReadShortAddrReg(uint8_t addr)         {
    uint8_t data;
    addr <<= 1;                            //MSB = 0 for short, LSB = 0 for reading
    GPIOB->BRR = GPIO_Pin_12;              //Enable SPI slave
    data = SPI_ByteTransfer(addr);
    while(SPI2->SR & SPI_I2S_FLAG_BSY);    //Wait for bus free
    GPIOB->BSRR = GPIO_Pin_12;             //Disable SPI slave
    return data;
}


texts: How do I know if my microcontroller clock frequency is fast enough?

texts:
I've been using ARM microcontrollers from NXP in commercial products with great success for the last 2 years.

In most of my projects I don't use the PLL to increase the oscillator frequency because I never found it was needed (never felt that clock frequency was an issue), and because the PLL slightly increases power consumption.

However I don't know how can I measure what clock frequency is enough to power my code. I'm stuck with this question in my head because as you may know the faster the clock you use, the more power you end up consuming. Since these days portable equipment with limited batteries are common this is an important topic.

The main question here is how can I know if the current clock frequency is enough for my code?

In this question I state "stopping or delays" because I assume that if my clock frequency isn't enough the first symptom that will happen is a slow response time from time consuming routines.

I use in almost my projects a state machine system that has an OnIdle() function that is called when the system doesn't have any events to process, so it can put the MCU in a low power mode. I was thinking about measuring how much time the system stays in this function and record min and max watermarks of this measure to have real numbers about if the current system clock is or isn't enough.

Does anyone have suggestions for this?


texts:
I am studying the Programmable Logic Array (PLA) and Programmable Array Logic (PAL). I understood every detail I found about them including the implementation and difference between them. But I have a very simple question about their naming.
Why did the early designer of such devices choose those close names for both of them? If the PLA appeared first then they designed a new device, why did they just swapped two words in the name from Programmable Logic Array (PLA) to Programmable Array Logic (PAL)? Do not you find it very confusing to differentiate between them?
I did google search to find an answer to this question but I did not find any.
Do you have any explanation?


texts:
I have 7 shelves that are 4 feet across that I want to light with LED strip lighting. After searching and looking for an answer, I can't find anything that is clear.
They are indoor shelves and need to be dimmable.
What kind of power supply should I use to power the LEDs? I am not sure what power supply I need to use when I have seven 48 inch strips running in parallel.
The LED strips I have are 20 inch individual strips and are cuttable every 2 inches, so I will make 48 inch strips out of these. Here is the LED strip specification from the website I bought them from:

Any help on this would be awesome. I don't want to buy the wrong power supply.


texts: TTL, Totem Pole vs. Open Collector Output

texts:
What is the difference of these two ttl nand gates?

What is a totem pole, what does it do and what is it used for?

When connecting multiple ttl logic gates together is it better to use one or the other?


texts: In am receivers, we detect the modulating signal by using envelope detector. So, the diode rectifies the signal, and the detected signal has doubled frequency than the original. Does this mean we will hear distorted sounds, if we connect audio amplifier. Is it possible to decrease the frequency by two?


texts: Can I use Arduino Software and IDE for development on Freeduino Atmega 328?


texts:
I have an old ferrite memory core plane that has either an "M" or a "W" watermarked on the board and was curious which manufacturer made this board. "Memory 2006000" is stamped on the wire side. "2005900" is stamped on the solder side.There is also hand etched numbers along the edges of the board which include "6401", "M", "1067", "1052" AND "1221"
Does anyone know?


texts: Power-Supply "Combination": Solar for voltage + Battery for current

texts:
I'm rather new to circuits & DIY electronics, but am thoroughly enjoying tinkering with my new RaspberryPi and assorted components. I'm trying to power the device using a few simple solar panels I stripped from cheap LED lawn lights from Menards.

I've combined three 2V solar units in series to output 6V total. The RasPi (B+ model) device needs 5V @ 800mA (including some components I've added). While I expect steady, consistent lighting (will be inside under relatively bright fluorescent lights, but I haven't gotten to measure their luminosity or anything yet), I believe the solar panels can only put out a couple hundred mA.

I have a couple old Samsung Galaxy batteries, which put out 3.7V, 1650mAh. My thought is that a charged battery (or perhaps two in parallel) could provide sufficient current, while the solar panel could keep the voltage in the circuit high enough. But my understanding of the intricacies of circuits (especially many elements in combination) is really limited, so I'm not sure this is possible.

My hope is this: Fully charged, two Samsung batteries in parallel could provide 3300mAh at 3.7V, which could supply the RasPi's needed 800mA for just over 4 hours. But the voltage is too low, so I hope I could "combine" the battery's current with the solar panel's 6V voltage supply "upstream" of the RaspberryPi.

I also know that using the solar to charge the battery is a whole other question, given the RasPi's power needs. Even without any load, at 1650mAh, each battery would take 11 hours to charge, or 22 for both! So I'm not too concerned about that just yet. But I'm curious for now to see what's possible with the pieces I've got.

Thanks in advance for any help or advice! Let me know if I can clear up or expound on anything I said.

Linking two posts I found that I think are related:
1) Multiple Power Sources Each For a Certain Purpose
2) Arduino Project Powered by Solar or Battery

I'm not entirely certain whether they address my questions, but I'm working on it.


texts: Measure phase difference with less than a full wave?

texts:
I am interested in aircraft altitude measurement during approach. Off the shelf sonar doesn't provide enough distance, and inexpensive radio sensors don't provide a short enough distance. I have seen other radio wave projects attempt distance measure with "time of flight" and believe this is the wrong approach - a difference of phase angle would allow slower electronics and less critical rf circuits.

A search of this forum shows a number of discussion how impractical "time of flight" calculations are for simple electronics. I suspect the signs in many cities showing car speeds are using phase angle and not "time of flight", but they seem to quit measuring at 30-50ft.

I am trying to figure out what the lowest frequency will be needed for measuring 5ft to 200-300ft. Of course measuring down to 5ft is the critical frequency limitation and generally several cycles are needed for a the transmitted wave to measure accuratly. The table here is partially reproduced below.

  Freq      length     1/4 wave
  ................................
  50  MHZ     6m         1.5m
  100 MHz     3m         28cm
  300 mhz     1m         25cm
  500 mhz    .6m         15cm

Due to a less than perfect world, it looks like measuring down to 5ft (10ft round trip) will need at least 300mhz (1m full wave), but the 1/4 wave column got me wondering if some how less than a full wave can be measured accurately? I understand the 1/4 wave data is supplied for antenna purposes.

My project would be much simpler if I could use a 100mhz transmitter instead of 300mhz. I have found an off the shelf sensor (AD8302 board) for less than $10 with 1 degree phase resolution.

Does anyone know if there is a simple theory or whether it is possible to measure phase difference with less than a full wave?

Thanks


texts: Does Sony NP-F type (generic) batteries have any over discharge protection circuitry inside?

texts:
I use these Sony NP-F550 or NP-F570 Li-PO generic batteries (8.4V) for video light and for powering my DIY projects.
I've read you shouldn't discharge a 8.4V Li-ion (it's a double 3.7V cell inside the casing) below 6.0V.
I thought that these batteries had some sort of discharge limit circuitry inside. That they would "turn off" when below a certain voltage. But when using them in some Arduino projects, they do discharge until the Arduino turns off (below 5V), as there seems to be no protection at all.
Does anybody knows if it's normal for this kind of battery to discharge beyond the safe point? There's a PCB circuit inside, and I can't put it to charge in a regular Li-PO charger. It charges normally in a NP-F specific charger. Sometimes a battery can go down to 20% amount of charge (as the LCD in the charger shows).


texts: How to determine diode will conduct or not

texts:
Here we had to find the voltage for which the diode will act as a forward bias.

I am a little confused about how do we find whether or not a diode will conduct or not in a network having more than one independent voltage and current source.

What I did was removed the diode, determined the thevnin equivalent voltage across the open terminals after removing the diode. That turned out to be Vi-1 volts.

Am I right ?

Does that mean then that for the diode to be forward biased, Vi-1 volts must be less than zero ?


texts: If A=0, B=1, and x=0 what are A' and B' in the logic circuit below?

texts:
The following circuit diagram what are A' and B'?

The question in the slide asks what happens if A=0, B=1, and x=0.
I understand what it means when x=0, but what exactly does this mean when A=0 and B=1?
The way A and B are labeled in the diagram it appears like they represent the hardware device, not an input.  Can someone explain to me what A and B are exactly?

In the following diagram we are given the answer if A=0,B=1,and x=0 in red.
Can somebody explain how they arrived at this answer?

Trying to make sense if it myself, here is my train of thought:

Input x is fed into a NOT gate, making it x'.  x' is fed into an AND gate with Q', thus making the output (x'^Q').  Which is then fed into an OR gate with Q, giving you Q OR (x' ^ Q') = (Q OR x') AND (Q OR Q') = Q OR x'.  This is fed into both inputs of B, which doesn't make any sense to me. At this point I am lost, so I would appreciate some guidance what happens to Q OR x'?


texts:
I made a simple LED circuit with an Arduino Uno with a 220 ohm resistor.
I measured the voltage across the outputs on the wires.
It shows 5.08V.
When I measure the voltage across the LED and the resistor separately I get 1.740V and 3.020V respectively.  That makes 4.760V in total.
Why is it not 5.08V? Does that indicate internal resistance of the breadboard?

Thanks a lot for your thorough explanations. @hacktastical I actually had a constant high drive and your explanation makes sense, thank you.
I have one more question though; why do I then get 5.08V across outputs of the Arduino without any circuit in between? I mean if the internal resistance of the components cause this, shouldn't I still measure less than 5V in this circumstance?


texts:
Background
I'm working on a seismic alert network and seismograph station at my school in Puerto Rico. We're building a solar system for the system to continue running during a potential seismic event. The system only consumes about 10 Watts, but with the satellite internet equipment it might go up to about 40 Watts. Based on my calculations, the needed battery bank will be about 200AH (12V System with AGM batteries for safety). This goes a bit over our budget, so I thought of redesigning the system so it would be more of a "backup" instead of 24/7 solar power.
Question
Could I use a relay to change the load to battery power if the mains electricity power goes out? This way, the satellite internet equipment will always be powered by the school's mains electricity, but once it goes out, it automatically changes to battery power from the solar system.
What I had in mind
I thought of using a relay to control the change as follows:
Common: Load Positive (AC)
Normally Disconnected: Mains Electricity Positive (AC)
Normally Connected: Solar System Battery Power Positive (AC)
The relay will be activated with a 5V Power Supply connected to the school's mains electricity, so if the power goes out, it will transfer the load (satellite internet equipment) to the battery backup power.
What I want to accomplish with this
So what I'm thinking is that by maintaining the satellite internet equipment connected the majority of the time to mains electricity, I can downsize a bit the battery capacity needed for the solar system, since it will only consume the 10 Watts from the seismograph. Then in the event of a power outage, it will provide some hours of power to the internet system, even if it goes out before the sun goes up again.
EDIT
Is this an automatic transfer switch I'm referring to?

Feel free to give suggestions about the system, if it could work, if it would be dangerous, or if there's a better solution to it! I appreciate your feedback!


texts: Two-Channel PWM LED Driving at 12A Load Issue (Signals affect each other)

texts:
I am designing a two-channel PWM LED driver. It will switch 24V LED strips at 12 amps. Each strip has two white LED chips. Each channel complements the duty-cycle of the other one (i.e. while one channel's duty-cycle is 20%, the other is 80%). Thus I am able to adjust the CCT (correlated color temperature).

I designed and coded the circuit. I don't have enough LED strips that provide 12 A, so I am using two rheostats for load.

The driver circuit schematic is shown below:

simulate this circuit – Schematic created using CircuitLab

I am monitoring the both Drain to Source PWM signals on an oscilloscope. When I change the duty-cycles of the channels, the one with the wider duty-cycle creates voltage spikes over the narrower one's signal and it changes voltage level of the other's signal on own switching time. (Oscilloscope screen photos are below.)

0% Yellow (CH1) - 100% Blue (CH2)

10% Yellow - %90 Blue

30% Yellow - 70% Blue

50% Yellow - 50% Blue

70% Yellow - 30% Blue

90% Yellow - 10% Blue

100% Yellow - 0% Blue

How can I eliminate these disruptive effects of both switching on each other? I tried to design a snubber according to NXP AN11160. But it didn't eliminate this effect.

My power stage schematic is:

Two regulator used in power stage. LM317 is down 20-30VDC input to ~10VDC to drive MOSFET's gates. L78L33 for feeding the MCU and other ICs..

My pcb layout is:

My probe setup is:     NEW setup:

Power Supply wave form while switching :

I am able to suppress voltage spikes by adding a resistor between the gate of power mosfets and drain of driver mosfets. My drain to source signals of M1/M2 is :

My another problem is audible noise at heavy load. C1 and C2 in the circuit are 4u7 ceramic caps and while the PWM duty-cycles are different from 100%, the caps make audible noise. The switching frequency is 400Hz, that is below the audible borders.. I tried to use aluminum electrolytic caps instead of ceramic ones. However, electrolytic capacitors heated and exploded after a while.

How can I solve audible noise?


texts:
In my product i am using a wifi module requires 3.3v and a bunch of other components requires 5v. For this i am using 3.7v 3000mAh battery. So here i have a doubt whether to use which case or any other suggestions

case 1: To use two 3.7v battery in series becomes 7.4 so that i can use a 3.3v regulator to convert from 3.7 and a 5v regulator to convert from 7.4V as in below fig.

simulate this circuit – Schematic created using CircuitLab

case 2: Use one 3.7v battery and use a 3.3v regulator and 5v booster(if this please suggest a good circuit or module). If i use this does the power consumption increases and batter level reduces in short time? or it doesn't?


texts: I am a mechanical engineering student and for my final project I am designing a solar car ventilation system so I need to know how much power the air conditioner of a car (Mazda Lantis 323 2001) fan needs to get from solar panel(12V) in order to operate properly?


texts: I needed to find the minimal order of Chebyshev low pass filter for given dB and rad/s

texts: Is the work ok and which one do I take the smaller value or the bigger one?


texts: LTspice: How to make a time-variant mutual inductance coefficient in transformer model

texts: I would like to make a transformer model with a time-variant mutual inductance coefficient. Does it work at (K1 L1 L2 var)?


texts:
it is well known that the characteristics of a DC amplifier is realised by a bode plot which has gain and frequency on the y- and x- axis respectively. But frequency of DC is zero. How is it possible to plot a frequency based graph for DC op-amp ??
Thanks in advance !!


texts: 555 Timer Min Max Expected Output Voltage Value

texts:
Could someone please tell me what are the min and max output values that should be expected from a 555 timer Output (pin 3) given X volts as the voltage source?

For example, assuming that the 555 timer is powered by 9 volts, what should the pin 3 voltage be when the pin is low and when the pin is high? I was under the impression that the voltage should be 0 when the pin is low and 9 when the pin is high but instead I get 0 volts when the pin is low but only 7.7 volts when it is high (Note that I measured the voltage with no load on pin 3).

I tried this with a couple of timers that I have laying around here and they all did the same thing. At this point I am not sure if I have a bad batch of timers, if I am connecting things the wrong way of if this is the way is should be.

If possible, could someone also point me to the place in the timer 555 specs document where it specifies what the output should be? I tried looking at the specs but I got lost, I am still pretty new to electronics and spec sheets overwhelm me a little.

The specific timer I am using is NE555P.

Thanks.


texts:
I'm using this IC (https://www2.mouser.com/datasheet/2/609/ADM1270-878589.pdf) to control the current and the voltage on some of the outputs of a PCB that controls the power to other PCBs, which have several sensitive components like microcontrollers and other semiconductors.

This IC controls the gate of a pmos. I'm thinking about using this MOSFET (https://www2.mouser.com/datasheet/2/389/sts10p4llf6-956791.pdf).

The IC gate current is very low (GATE Pull-Down (On) Current = 25 uA), and the MOSFET gate has a fair amount of charge (Total gate charge = 34nC), so I did the math: Q=it => t= 1.36 ms, which is the amount of time to switch the MOSFET without any resistor (I think...). If I use a resistance to limit the current the time to switch will increase even more.

My doubts are:

Are my assumptions/calculations correct?
How long do I have before my sensitive components get fried? Is 2 ms of delay on my protection IC good enough?

My objective is not only to protect singular components, but also to know which subsystems are functional and to be able to isolate the damage, if it can't be prevented completely.

(Context) I'm a Mechanical Engineering student doing an electronics project in an automotive context.

Thank you in advance for the help!


texts: Hysterisis - How do you choose a good value for R3?

texts:
simulate this circuit – Schematic created using CircuitLab

Above is the basic schematic for a comparator with hysteresis. Determining the values of R1 and R2 is fairly straight forward. They essentially boil down to ratios of R3 and you can just plug the values into the relevant formula.

So, the choice of R3 seems to be the most important design decision. But I haven't really been able to find much information on how to work out what a good value for R3 is.

I've been having some problems with designs that look good on paper but don't seem to function correctly in reality...

Picking a high value seems good, since it would reduce overall current usage. But how high can you go?

What characteristics of the comparator are important? Does the value of VRef have any impact (many comparators have a built in VRef, so you may not have a choice here)?

Essentially my question is: What factors do you need to consider when choosing the value of R3 to design an efficient and stable hysteresis circuit?


texts: Why can current flow through the reverse biased base-collector junction (N-P junction) in a BJT with a forward biased base-emitter junction?

texts:
If the base-emitter junction of a BJT is forward biased, then current can flow through the reverse biased base-collector junction (N-P junction). This disagrees with my understanding of the PN junction, as I thought electrons cannot flow from the P-side to the N-side of the reverse biased junction, since there is a depletion region between them.

I understand why the current can flow through the forward biased base-emitter junction: the external voltage (positive connected to P-side, negative connected to N-side) creates an electric field from the N-side to the P-side, which cancels out the built in electric field caused by diffusion of carriers across the dissimilar materials. This collapses the depletion region.

However, in the reverse biased base-collector junction the external voltage will support the built in potential and cause a larger electric field (from the N-side to the P-side), which will stop positive charges flowing from N to P, and stop negative charges flowing from P to N.

But if you forward bias the base-emitter junction, and reverse bias the base-collector junction, electrons can still flow from the collector to the base, which is from P to N, which as I just explained in the previous paragraph should not be able to happen?

So what allows the electrons to flow through the reverse biased PN junction, as in the case of the collector-base junction of a BJT?


texts: reading the position of a switch using a microcontroller

texts:
I would like to use a micro controller to read the position of a switch.

The example and image below is for illustration purposes only.

For example if a switch is at Position A, a 5V signal might feed DIGITAL INPUT 1. Similarly if the switch is at Position B, a 5V signal might feed DIGITAL INPUT 2. To make the signals useful, they would be on exclusivity to the other.

i.e.

Position A   Position B   |   DIGITAL 1      DIGITAL 2
--------------------------|----------------------------
    ON          OFF       |     HIGH          LOW
                          |
    OFF         ON        |     LOW           HIGH

The circuit is powered by the micro controller's 5V supply, and shares a common ground with the micro controller.

Thank you.

EDIT: changed R1 (1 kOhm) to a DC motor, to better represent the actual circuit.

Also, the input voltage has an error or +-0.5V. The resistors have a 5% error tolerance.

https://www.circuitlab.com/circuit/wec9n2/switch-sensing/


texts: Is a DMOS potential free? (in case of TPIC6C596)

texts:
I've been looking at the Datasheet of the TPIC6C596 and I'm not sure if the DMOS that is mentioned in the package can be used as a potential free.

I also don't know in general if a DMOS can be used as a potential free contact.

According to this functional Block Diagram the DMOS will just switch the Drain to GND if powered. So I wondered if this counts as a potential difference in the switched circuit.

Here's an example of what the circuit with the TPIC6C596 would look like:

simulate this circuit – Schematic created using CircuitLab


texts:
I have a part that looks like this under my microscope:

and it is a TPS22810 load switch (datasheet). But, how do I know which side is which?


texts:
I'm thinking about buying a TDA8920 audio amplifier and power supply and I need some help buying the right PSU. See edit below.

So here's what I know.
L (AC) = Live (Brown*)
N (AC) = Neutral (Blue*)

__|__  = This normally indicate natural ground in AC (green/yellow**).
 ___
  _

** in Sweden

So here's where the problem starts. On AC-DC 5V you will get +VCC and GND connectors.
But TDA8920 is a op-amp chip and requires +V GND -V (±12.5 to ±30 V). I have been looking on some SMPS (switching-mode power supply) and there output is as following (see below).
On some units COM are replaced by -V.

How do I wire it all up?
TDA8920 --> SMPS
+V --> +V
-V --> -V (or -V --> COM?)
GND --> Where does this fellow go? Also -V/COM? COM is normally ground on voltage meters and there is no specified output as AC-DC 5V adapters have.

Also I'm hooking up a 24V to 5V step-down.
Ebay item: 191014663436
step-down --> SMPS
IN+ (V) --> +V
GND --> -V/COM?

Audio Amplifier - TDA8920
Ebay: D Class TDA8920 Digital Stereo Audio Amplifier OCL 2*80W Power Amp Board BTL
Item number: 190898639459

+V
GND
-V

Model PS100-W1V24
Ebay item: 291031105572

L (AC)
N (AC)

__|__
 ___
  _

-V
-V
+V
+V

S-50-24
Ebay item: 231045540508

L (AC)
N (AC)

__|__
 ___
  _

COM (-V on some units)
+V

As a side note, do you know how many A my PSU will need to power the following:
PSU -> TDA8920
PSU -> Stepdown -> Raspberry Pi
Raspberry Pi -> Arduino (5v from RPI or stepdown)
Raspberry Pi WiFi and USB Soundcard

Raspberry Pi requires 700mA/1A
Arduino 500mA/1A
TDA8920 n/a - can't find any information

Stepdown are rated 5A on the output side

I have been looking on SMPS PSU ranging from 2.2A-4.5A, will this be enough?

EDIT: 20:00 / 2014-03-30
Now I have googled and googled some more. This is what I have come up with:
TDA8920 --> SMPS
+V --> +V
-V --> -V
GND --> GND/Ground/Common
You can't choose one with COM / +V (Not for this board at least) due to the fact it requires a negative voltage. Or you need two power supplies. (So scratch S-50-24 off the list)
http://kb.bkprecision.com/questions.php?questionid=224

  Wikipedia Ground (electricity) # 5.1 Circuit ground versus earth

  Voltage is a differential quantity. To measure the voltage of a single point, a reference point must be selected to measure against. This common reference point is called "ground" and considered to have zero voltage. This signal ground may not be connected to a power ground. A system where the system ground is not connected to another circuit or to earth (though there may still be AC coupling) is often referred to as a floating ground.

But if you want to build a Audio amplifier for a radio, you must choose another power supply, due to the fact that switching-mode power supply are interfering with RF frequencies.
http://lenardaudio.com/education/12_amps_7.html

So back to the drawing board and get me a AC-AC transformer to ~25V and a AC-DC rectified & filtered +-25DC power supply with capacitors.
Now I will search for a way to calculate VA requirements and by the look of things these are huge so maybe I will choose a crappier audio amplifier to fit inside a old 50/60 radio.

EDIT2: 23:24 / 2014-03-30
None of the power supplies I have mention does work with this audio amplifier, I have checked some schematics on similar switching-mode power supply and they don't give you -V on -V pin. It's just COM (common).
You need a "bipolar/split-rail/dual rail supply" power supply

Regarding previous link about radio interference there shouldn't be a problem if your switching-mode power supply are correctly made. If you google "Interference from Switched Mode Power Supplies" you will find a article by UKQRM about this. (Don't have enough rep to link more).


texts: Effects of not enough current for a microcontroller?

texts: I have a picaxe 28-x1 and a Sharp Distance Sensor. When I try to program the PIC with the sensor plugged in it can't find the PIC but when I unplug the sensor it finds it. Is it possible that the sensor is using all the current and there isn't enough for the PIC? When I test the separate parts they work. Is it another problem, if so what?


texts: Ensuring good contact between ring terminals and the screw terminals they're bolted to

texts:
I'm working on a high-current switching converter for research purposes. Because of the voltages and currents involved, many components use screw terminals to connect to wires. I haven't used screw terminals that needed to be able to carry 100A before, and want to ask:

What is the recommended way to make good electrical contact between screw terminals and ring terminals or PCB pads? Is there an IPC standard for this?

Are there any types of nut or washer that can provide a gas-tight seal? Or am I worrying about things that don't matter, and the seal of a normal tightened nut is more than sufficient?


texts: Making transistors or semiconductors at home

texts:
The transistor was invented some 50 65 years ago, so is it not about time to be able to make transistors or other semiconductors at home?

Would that be possible?


texts: Effects of encasing bluetooth chip and rechargeable battery in an adhesive encapsulate?

texts:
I am thinking to encase my entire bluetooth PCB along and connected battery in an adhesive such as a soft urethane or silicone encapsulate. My board and battery are each about the size of two stacked quarters. Of course I will be avoiding getting the adhesive on any input ports and the on/off pairing button. I feel like this would give it good water resistance. Also it would hold my components together and to their enclosure and would especially protect a few soldered connections I made with the battery etc.

Has anyone tried this or can hazard a guess? I am concerned that the bluetooth reception will be significantly diminished. Should I also be concerned about the thing heating up and catching fire? I would use a non-flammable adhesive, and the battery for the bluetooth is only about 3V (and charges via usb).

What else might I be concerned about?


texts:
I just received my ArduinoBT in the mail, and was a little confused about how to get code onto it. Typically, you can upload it via USB through the Arduino IDE.

I have a vague understanding of what a bootloader is - which comes pre-installed on the ArduinoBT, but I don't understand how I can get the code to the bootloader.

The docs suggest that you can still connect via the IDE and they provide the default name of the device, along with a default password. However, wouldn't I need some sort of BlueTooth receiver on my PC to achieve communication with the ArduinoBT?

Do I have to have an AVR ISP Programmer? Is there another way to get code on the device?


texts:
I originally was looking into a Nixie clock. I'm scaling back a little and going to try a Numitron clock first. It lacks the high voltage :)

Hows this look for a Numitron clock?

The solenoids are these. I'm planning on putting the Arduino bootloader on the Atmega and using the USB to program it. (I'm planning on using this to mess around with a bit to learn from).


texts: Does a correctly sized resistor protect low voltage components from a high voltage source?

texts:
Let's say that I have a 37v DC source that I would like to reduce to 12v so it can run a 12v light bar (a string of 6 leds and I assume a resistor to limit the current).

I measure the resistance of the light bar at 35 Ohms, so using Ohm's law I calculate that putting a 70 ohm resistor before the light bar will safely reduce the voltage from 37v to 12v and run through the light bar at the expected 351 mA.

Will this really protect the components of the light bar considering the fact that the inital voltage is 37v until the current starts flowing. If you measure the voltage of the 70 ohm resistor before the current starts flowing: it reads 37v. It's only after the current starts flowing: that the voltage is reduced to 12v. Is it possible for the 37v to damage a component that's not rated or such a high voltage? Initially I tried applying 29v directly to it (no initial resistor) and it instantly smoked and died without heating up first despite being supposedly rated for 12-30v so I'm wondering if some arcing will occur internally with 37v and a resistor.

Diagram / Simulation


texts:
I'm currently developing a BLDC controller with hall sensors, curious about where the hall sensors triggered.  Are they triggered when just a commutation axis becomes or around the axis (at the sector changings in the image)?
The controller will control the motor according to space vector modulation. I'm planning that according to the hall triggering positions, microcontroller will calculate the angle according to the commutation step axes (red axes in the right picture). So, when the hall states changed, is that means the motor is -for example- between the (1, 0, 0) and (1, 1, 0) axes? Or will be 30 degrees later after the halls triggered?
Thanks in advance.
Edit: The hall sensors are positioned 120 degrees according to each other.


texts: Why does PCIe hotplug capability require hardware support?

texts:
As far as I understand, hot-plugging a PCIe connection requires both hardware and software support.

Software-wise, it makes sense, since the OS has to re-scan the bus, and by default it doesn't do this after the initial scan.

Hardware-wise, I do imagine it would require special circuitry in order to send an interrupt to the CPU, so that the OS is informed about a new device being connected to the bus.

However, what I do not understand, is why there is a risk of burning/damaging components if I just plug-in a PCIe device while the computer is running.

How does electrical current flow differently from when the PC is turned on after the insertion?


texts:
Can anyone provide a reference design for a 434 MHz PCB Trace Antenna? Is it just a matter of creating a snake trace pattern about 17cm long and slapping a ground plane under it (with a trace thickness for say 50 ohms characteristic impedance to the ground plane given the PCB thickness)?

The context is that I think I'm heading toward using a trace antenna with the RFM12B transceiver module en route to passing regulatory standards. I've been told that embedding the antenna in the PCB is an easier / lower cost path to certification than allowing for a whip (or other externally connected) antenna. Any advice or pointers would be most appreciated!


texts: Does PCB artwork affect operation and how is the effect validated?

texts:
Sometimes PCB designers will draw some art on unused PCB areas. Like here and here.

Looks great, but does this affect schema functioning? According to answers to this question an entirely isolated stripe of aluminum foil may act as a stripe antenna.

So I'd imagine the following scenario is quite possible:

a PCB layout is designed and some area is left unused
an artwork is added there
the artwork adds capacitance or otherwise affects operations

Does PCB artwork affect schema operation? How do designers validate the effects are tolerable?


texts: Old monitor’s internal power supply works only when heated from the outside...fixable?

texts:
I have this old LG Flatron w1934s that worked fine until it‘s power indicator led started flashing, and after a long while the monitor turned then on, if I heated the monitor’s back with something like a heat gun it started after a few seconds! While the starting process is going it is possible to head a switching mood from the monitor’s PCB, a sound that during operation is not present! I took the monitor apart and tested the voltages on the backlight lamps, I found one, top right in the picture, to have a lower DC voltage than the others at startup, and an equal one during operation...I also tested how log the monitor took to start depending on the zones I heated in the PCB, the two mosfet’s heatsink, if heated, is the fastest one to make it start!

My question is if it’s most likely a bad joint problem, that a resoldering could fix, or what else can I look into?


texts: How do you calculate caps for voltage regulator circuit

texts:
In a voltage regulator circuit, how do you calculate which capacitors are placed before and after the regulator?

For example, if I'm pulling 50mA from a 5VDC regulator(L78M05) with a 9V input, how do I determine which caps are going to give me the least amount of ripple?


texts:
I'm sending over the air data block which is 144 bytes.
I can put additional 18 bytes of data for error correction.
The field for FEC looks very small and I can't find what I can use.
I have not requirements about BER, the number of bits to restore etc.
I need to fix as much as possible.
What FEC I can use for 162 bytes block where is 144 bytes data and 18 bytes FEC?


texts: Using a higher C than necessary in a voltage regulator circuit

texts:
I've two questions:

If I've a voltage regulator that says in the datasheet to use electrolytic capacitors is it possible to use 'normal' capacitors with the same capacitance?
I've the circuit drawn in the figure below. Can I use 2,2 microfarad capacitor as input capacitor (instead of the 0,33 microfarad one) and a 1 microfarad output capacitor (instead of the 0,1 microfarad one)?


texts: NiMH battery at 660mV, is it trash or good?

texts:
An AAA battery of type NiMH is only at 660mV (unloaded).
Can it still be charged and used or should I throw it away*?

Some more details:

The battery comes in a 2 pack. The other battery has about 1.2V. The pack was opened and stored in my drawer for a year or so. I probably used one of them, that's why it is "empty", but honestly I don't remember.

I will try to charge them (both, as my charger only works with pairs).

* of course to a proper bin for old batteries


texts: How to wire together DPDT and rocker switch without fear of short circuit?

texts:
I am working on desktop monitor raise -system with a 12V 3amp linear actuator (that has dual self locking mechanisms) and would like to use both dpdt switch to let it run up or down freely, and 2-pole switch to make fine adjustments for the height if wanted.
I know how to wire the DPDT. I could also put wires just between the switches but the problem is that if I have the DPDT locked down and press the rocker (2-pole) switch up I end up short circuiting the system.
Someone told me to put diodes in between the switches. I just don´t know how to design this.
In summary:

I have a DPDT switch (Boot rocker switch, 6 terminals, 3 position)
Rocker switch that has 6 terminals, 2-pole.

I need to wire them together succesfully with no risk of short circuit.


texts: I'm using the absolute value block from AHDL library in cadence virtuoso. I need to take absolute value of a signal which varies from -5 to +5 volts. Since the voltage passes through 0 volts when there is a transition from -5 to 5 and 5 to -5, there are some spikes in the output of my absolute value block. Is there a way by which I could remove these spikes? This is important because I'm connecting the output of this block to a reciprocal block.


texts:
I'm working on a project and I need to use a Futaba S3003 servo, I'm about to buy a transformer that gives 6v, the thing I'm not sure about is the amperage.

Is this transformer ok? I can choose 3V, 4.5V, 6V, 7.5V, 9V and 12V, but its 800mA and I don't know if it is OK with the servo.

EDIT:
Link to servo datasheet: http://www.es.co.th/schemetic/pdf/et-servo-s3003.pdf

The transformer is only for powering the servo


texts: What is the “dt” in the complementary filter equation and how do I find out the “dt”?

texts:
I am trying to implement a complementary filter in my system but I do not quite understand what "dt" means and how should I find out the "dt" in the complementary filter equation.

I found the complementary filter equation here.

This is the equation:

$$angle = 0.98 * (angle + gyrData * dt) + 0.02 * (accData)$$

This is the code I am using now:

while n!= 10:

data = bus.read_i2c_block_data(0x68, 0x3B, 6)

xAccl = data[0] * 256 + data[1]
if xAccl > 32767 :
        xAccl -= 65536

yAccl = data[2] * 256 + data[3]
if yAccl > 32767 :
        yAccl -= 65536

zAccl = data[4] * 256 + data[5]
if zAccl > 32767 :
        zAccl -= 65536

data = bus.read_i2c_block_data(0x68, 0x43, 6)

xGyro = data[0] * 256 + data[1]
if xGyro > 32767 :
        xGyro -= 65536

yGyro = data[2] * 256 + data[3]
if yGyro > 32767 :
        yGyro -= 65536

zGyro = data[4] * 256 + data[5]
if zGyro > 32767 :
        zGyro -= 65536

totZdata += zAccl
totXdata += xAccl
totYdata += yAccl
totGyroXdata += xGyro
totGyroYdata += yGyro
totGyroZdata += zGyro
zAcclG = (zAccl - AcclzOff) / Accl_scale
xAcclG = (xAccl - AcclxOff) / Accl_scale
yAcclG = (yAccl - AcclyOff) / Accl_scale
xGyroDPS = (xGyro - GyroxOff) / Gyro_scale
yGyroDPS = (yGyro - GyroyOff) / Gyro_scale
zGyroDPS = (zGyro - GyrozOff) / Gyro_scale

print ("Acceleration in X-Axis : %.2f G" %xAcclG)
print ("Acceleration in Y-Axis : %.2f G" %yAcclG)
print ("Acceleration in Z-Axis : %.2f G" %zAcclG)
print (" X rotation : %f" % (get_x_rotation(xAcclG, yAcclG, zAcclG)))
print (" Y rotation : %f" % (get_y_rotation(xAcclG, yAcclG, zAcclG)))
print ("X-Axis of Rotation : %.2f" %xGyroDPS)
print ("Y-Axis of Rotation : %.2f" %yGyroDPS)
print ("Z-Axis of Rotation : %.2f" %zGyroDPS)
n += 1

How can I determine the "dt" from the cmplementary filter equation?


texts: Is there any reasoning behind component names?

texts:
All the components I own have strange names, like a transistor called 2N2222 and a motor driver called L293D.  When you see these kind of things writen down do you instantly know what it means or do you have to google it every time?

How much information is hidden in these codes or are they totally random?


texts: How to calculate measurement error in a voltage divider?

texts:
I'm trying to calculate the measurement uncertainty of the voltage represented by the ADC in +/- V or % of a voltage measured across R2 of a voltage divider.
What would be the general way to tackle this problem? I found a video of someone calculating measurement uncertainty of a voltage divider using partial derivatives.
The formula used is shown below.
Would the quantization error of the ADC be added to the voltage uncertainty I calculate using the partial derivative method?
Q.E of ADC = LSB / 2 => (3.3V / 256) / 2 = 6,45 mV so is this the uncertainty I add to the uncertainty in voltage V2 to get a total uncertainty?


texts: Slayer Exciter circuit not producing electricity

texts: I used the circuit below to try to make a slayer exciter, but it doesn't seem to be able to power anything around it. Is there anything that I'm missing? Also, yes, I know that in the picture there is no battery :)


texts: How can I control TRIAC firing angle automatically with a DC voltage?

texts:
I have to build an analog proportional controller for a 127 V, 1 kW AC heating resistance. The power delivered to the heating element must be proportional to the difference between a set point temperature (40°C) and temperature measured with an LM35 sensor, conditioned to work between 0 and 5 VDC.

I tried to control the power delivered to the load by varying the firing angle of a TRIAC. However, I have searched online and on power electronics textbooks for ways to control the firing angle, but all the circuits I have found involve either potentiometers (such as dimmer circuits) that make then useless for automatic control, or special triggering circuits of which they provide no information whatsoever.

Is there a way to control the firing angle of a TRIAC using a DC voltage without resorting to manual control using potentiometers?
Or is there some other way of controlling the power delivered to an AC load using a DC voltage? Reference books or circuit diagrams would be greatly appreciated.

Also, any information regarding already existing trigger circuits for triacs (such as integrated circuits for triac firing) would be a lot of help.

NOTE: I am not allowed to use an Arduino for this circuit.


texts:
Does anyone know what this circuit symbol is? My guess is that it's a surge protector but I'm not sure

Context


texts: LM317 maximum current output as a voltage regulator

texts:
I built the following circuit in LTSpice using LM317.
With a current load at the output, stepping from 0.1A to 1A, I noticed the output voltage collapsed at around 800mA.

This is a surprise, since I read the datasheet somewhere that LM317 has a maximum output current of 1.5A.

So what did I do wrong in the simulation?

sim.zip - ltspice sim with 1N4001 and LM317 models


texts:
I have a choice between a CD4017 and a CD4017B.

I've also seen CD4026 and CD4026B.

What is the difference between these - is it a silicon revision or do they have different functionality?


texts: Can one tri-state pin drive two SS pins?

texts:
This is how i see it;

State H: SS out is High, Deselecting SS 2, turning off Q2 and on Q1, which grounds SS 1, turning it on.

State L: SS out is Low, turning off Q1 and grounds SS 2 through Q2. SS 1
 is deselected by R1

State Z: SS out is high impedance. R1&3 keep the SSs high. ARGH EDIT: R4 keeps Q1 off. R6 may keep Q2 off. IDK

simulate this circuit – Schematic created using CircuitLab

Am I wrong? It's purpose is for when gpio pins are a premium.

It's a 3V3 system.


texts: How to measure Voltage & Current with a single multimeter, Simultaneously?

texts:
I have bought a cheap but neat Uni-T UT61E multimeter, which only has one display as most multimeters. For 40 Euro's I cant complain. It's on the way to me.

Q.1 If I would like to measure both Voltage and Current, do I have to buy another multimeter? Are there mutlimeters that measure both Voltage and Current in two displays with multiple wires attached to the meter? Have searched but haven't found any hand-multimeter.

Q.2 I would like to put a very tiny voltage/current multimeter lcd on my batery pack so that I can check the volage there (without using my big multimeters) on travels. Any advice on how/where I can find such things?
So far I only found this which is a self-build kit:
Do you have better advice and/or know any existing final products that are calibrated and working okay?

http://www.electronics-diy.com/store.php?sel=kits&sub=pic_voltmeters

My new big mutlimeter on its way, with which I guesse I cant view voltage and current simultaneously:


texts:
I've researched and it says that resistors limit the current flowing through the LED.

But this statement confuses me because we know that in a series circuit, the current is constant at every point, so how come a resistor can limit the current flowing?


texts:
I thought of an idea recently, and I wanted to know if electrical engineers agreed with my theory.

I have a smartphone.
Recently I bought a power bank because I found my phone's battery not holding up long enough.

Now here is what I thought about while charging my power bank and my phone.

If both batteries (of my phone and powerbank) could in theory fill up 1 mAh/minute and both my phone and and the power bank are connected to the outlet, and are actively charging, I'm basically charging the two batteries at an effective 2 mAh/minute.

If both my phone and my battery pack could hold 1000 mAh, I could charge both half way to 500 mAh and still have an effective 1000 mAh at half the time it would take me to charge the phone alone.

So if I bought three banks then together with my phone I could get the same effective 1000 mAh in just a quarter of the time!

So if this works in theory: Why not divide the phone's battery into hundreds of separate banks to get hundreds of times the times the charge rate? What prevents this in practice?


texts:
I am building a device on breadboard where there are 2 ICs: a microcontroller and some auxillary IC, they should communicate via SPI with a 4 MHz clock. Because I don't have enough place on my breadboard, I plan using two breadboards, microcontroller on one and other IC on other. The question is, can I transmit 4MHz 3V3 signal over a jumpre wire, just like on the photo:

Will the signal be deteriorated? Where I can find some rule-of-thumb info about cables and their band-pass frequencies?


texts: What is the display life of ulcd-43PT TFT LCD Touch panels in terms of pixels and backlight? I want to keep it on in my application for the maximum time (say ten years) in an almost same state (data display).


texts: Are there any single chip solutions for single cell LiPo battery protection? If not, any references?

texts:
I can't seem to find one, but does anyone know of a single chip solution for LiPo battery protection on a single cell/3.7V battery? Looking for things like over-current/overvoltage/undervoltage protection. I wan't to be able to either have redundant protection or be able to use wholesale LiPos without protection to add some safety.

If not, does anyone know of a reference on how to design one? I'm more interested in learning how to design a circuit as opposed to a single chip solution since they are usually cheaper, but can't find any blog posts/papers/lessons/etc.


texts:
Can an Arduino turn on multiple leds at the same time?. I want make a home made lamp with several less controlled with an Arduino UNO light sensor and i already have the light sensor, also i know how to turn on one led.

But do not know if i can power several less.

Any advise?, thanks in advance.


texts:
I know we should not ask for product advice here, but I searched a lot for a specific board connection solution lately and it almost drives me crazy that I have only found so little options.

I need to connect two PCB spaced/stacked 26-28mm apart with at least 50 pins carrying each max. 1A current at lowest possible cost. Both boards can only be assembled on TOP side (Because both boards are on the same panel.) SMT and THT is ok, but no press fit. I need to be able to disconnect the boards. Special requirement: I can not turn one board head over heels because of other connectors that must remain the same orientation. So I need something like a header for the lower board and a reverse mount socket for the upper board.

Single row connectors would be ok.

First I thought about standard ribbon cable, but this seems to be way more expensive than other solutions. Then I thought about standard FFC/PFC cable. The standard 0.5mm pitch types are cheap, but I would need way more than 50 pins to distribute the >1A current of some of the power lines, which makes it expensive.

Then the Samtec BSW-125-04-T-D and TSW-125-18-F-D came to my attention. This is a standard 2-row 2.54mm SMT header (TSW) combined with a reverse entry SMT socket (BSW.) Together, this solution costs about 5.50 USD at 1kpcs median at octopart.

So my question is: Can anyone name a "type" of connection or even a product that could beat the 5.50 USD mark from above? Maybe you have met other connection systems that I haven't thought of.


texts:
There is a solid state relay (AQH1213) that switches the load to 220 V using 5 V (Arduino).

The insulation voltage between the low and high voltage circuits in this relay is 5 kV.

The challenge is to provide additional isolation for this relay and controller contact.

For these purposes, I plan to use an optocoupler.

Solid State Relay LED Characteristics:

Forward Current: 50 mA
Peak Forward Current: 1A
Reverse voltage: 6 V
Recommended input current per LED: 15-25 mA
A current limiting resistor of 300 Ohms is installed between the relay and the controller.

What optocoupler output current should I choose?

Initially, there were doubts about the high peak current of the solid state relay (1A). At this maximum current, the optocouplers require a supply voltage> 5 V, which in my case is not suitable, since all control circuits have a voltage of 5 V.

A current-limiting resistor should clearly reduce these indicators, but I do not know how accurate.

Applying Ohm's law (U = 5 V, R = 300), I got a very low current value of 0.016 A, is that true? If this is true, then most likely it does not take into account the maximum forward current.


texts: How can RS-232 DTR / RTS pins be used for power?

texts:
I want to interface to this device where (sec 4.2) states

  can be powered from the DTR and RTS handshaking lines by having one
  high and one low

Also, Wikipedia states:

  No method is specified for sending power to a device. While a small
  amount of current can be extracted from the DTR and RTS lines, this is
  only suitable for low-power devices

I would like to understand how RS-232 allows DTR / RTS to be used as power.
What polarity / voltage levels should be observed?
Can they be permanently wired or do they need to observe a protocol?

I'm particularly concerned that if I just wire DTR / RTS permanently to power then the handshaking protocol will screw up (assuming the device I'm interfacing to observes the handshake protocol).


texts: PCB markings and reverse engineering a board

texts:
I've got a fried board for an elliptical exercise machine and I'm looking to build my own replacement as there is no repairing or replacing the original. I have interfaced successfully with everything on the machine except the heart rate sensors on the handles. They go back to a small board that is elevated off the main board by some headers. I'm hoping to remove this small board and add it to the new computer but I can't seem to get it working. There is a row of 4 pins labeled - E O +.
My scope doesn't detect anything communication wise and tracing them out shows me that O goes through a resistor to a capacitor then ground. E goes directly to the main board CPU and looks to be pulled low by a 300k. The sensor pads go to 3 different pins that I'm not concerned about. The brain of this small board is one of those bare chips hiding under a black glob so I have no idea what it is..
Positive and negative are obvious, but E and O have me puzzled. Does anyone have any ideas what these might be? When powered they have a voltage increase but nothing happens when my hands are on the sensors.


texts: Stepping down/up center tapped transformer

texts:
I've got a Hifi setup to repair where the power amplifier died. I want to replace it with a different one. There is a center tapped transformer that provided +-35 volts DC for the original amplifier. My question is: can I use two buck converters to step the voltage down/up to +-20 volts?
One for the positive rail - V+ on converter to V+ on transformer and GND on converter to GND on transformer. The second one for negative rail - V+ on converter to GND on tranformer and GND on converter to V- on transformer.
Or will I blow something up?
The old amplifier was 50W and the new one is 20W (which is plenty) so I would not wory much about overloading the converters.
Thank you for your time and answers.


texts: I need to reduce the gain of an emitter follower circuit to 50%. Can I do this by splitting the emitter resistor into two sections and taking the output from the junction? I am concerned that I will loose the low output impedance characteristic of the circuit if I do this.


texts:
I'm trying to design a notch filter to suppress an oscillator signal coming through a mixer (namely, 53.125 MHz), at the same time I must get the best possible signal at 60 MHz.

I've been running some simulations - it seems lowering the capacitor value and increasing the inductor value makes the "notch" steeper. It would seem in this example design, I would be losing a lot of signal on 60 MHz?

What confuses me, also, is the role of the value of the resistor here, I don't really understand what the lower blue line and the dotted green line represent.

As I lower the resistor value, the lower blue line moves up and the dotted green line curves.

Can someone give a basic idea of what's going on here?


texts:
I have a custom board based on an Atmega168A which I would like to reset when the power switch to the on-board LEDs is switched off.

Resetting the uC by shorting RST and GND works on the ICSP connector (sanity check), but switching off the power switch SW1 when 5V is present does not. At least rarely. I did manage to make it work a few times, but it was shortly after I had shorted RESET and GND so it happened to work.

Here is the reset subcircuit, where both the USB data connector and 5V power supply are present, as well as the ICSP. It is supposed to be an adaptation of a typical DTR reset... (note +5V is separated from +5V_USB)

Here is what happened when the LED power was switched off, i.e. when the switch connects the net named +5V to 0V instead of the external 5V supply:

I modelled the subcircuit in LTspice just in case and proceeded to modify it to try something different - I needed a pull-down resistor between +5V and 0V USB anyway to monitor the presence of +5V from the Atmega (which I had forgotten): increased C6 to 330nF, removed short between +5V and 0V_USB when the switch is OFF, added R6=1k.

And the result: now the pulses are systematic regardless of whether I manually reset using the ICSP right before, but they're way too high for a reset at 2.4V !

LTSpice (and in fact, a simple calculation of resistor divider) says the pulse should go down to 0.6V... What's happening? RESET pins are supposed to have internal pull-ups in the order of 30k min, not 1k...

What would be an easy fix for this circuit (robust still) with as few additional components (if possible passives) as possible (the PCB is quite dense)?


texts: Does anybody have a detailed drawing of a 3U backplane for mounting eurocards in a 19" rack. My eurocards use the Harting din 41612 connectors. I'll looking for information on the position of the backplane connectors to make sure the eurocards line up with the guide rails etc.


texts: I've made a few things now using a RJ45 jack and a separate pulse transformer. To make the design smaller i'm looking to use a magjak or a RJ45 connector with the pulse transformer built in. The jack has the center tap pins tied together to a single pin. Does this mean that i need to tie the center pins together on the device and hook them to the single pin on the jack or is there some other connection scheme i'm not aware of?


texts: The Marx generator circuit isn't working. We are having trouble getting the output

texts:
As you can see, we are trying to build a Marx generator using BJT (astable configuration.)
We have a circuit for the Marx generator using a 555 timer which we tried and tested and it works fine.
We are not able to implement the same using BJTs:(
I'm attaching the 555 timer equivalent circuit and the circuit we are trying to build.
Edit:
Please see the image I added.  It is a clearer image of the 555 circuit.
BJT circuit:

555 circuit:

555 timer circuit:


texts: Is it possible for an opamp to oscillate at a frequency greater than its GBP?

texts:
I was installing a tl3141 into a headphone amplifier circuit and it appears to break into ~250mVp-p oscillation at 8-10MHz on the lower half of the waveform when fed a 1kHz sine wave.

Is that even possible given the specs of the opamp (GBP 1.1MHz, Slew rate 1.3V/μSec)? Given the measured oscillation the output would have to swing at somewhere around 2.75V/μSec which is well beyond that spec.


texts: Can I control a 12V motor from arduino using an H-bridge?

texts:
I want to control my 12 volt geared DC motor from my Arduino Uno. I want it to be able to rotate both directions as I'm intending to use it for a robot.
    Can I use the L293NE H-bridge in this case? The following diagram shows the pin connections. For this I'll have to externally supply the IC with 12 volts, but will I be exceeding the maximum voltage rating for the IC? I dont really want to blow up the IC in the midst of all that circuitry. Please tell me if there's a more suitable h-bridge for handling 12-volts, or another approach to my problem.


texts: What are the limitations of the USB Composite device

texts:
I am looking at coding a USB device that is capable of encapsulating two USB devices. I would like to create a HID keyboard with a single extra USB port. A mass storage device would be connected to the port.

I was wondering, would I be able to program the keyboard to register it as a composite device encapsulating the mass storage and the keyboard?

My current thought process is to declare the keyboard as having 2 interfaces. I was thinking of simply copying the USB commands from the mass drive into one of the interfaces of the keyboard. Is this possible?

If this is incorrect thinking, please let me know what the data formatting of the interfaces is suppose to be.

Thank you.

Also, this is for educational purposes to expand my knowledge of USB.


texts:
This question is very basic, but I'd like to ask it anyway.

I need to drive a small motor. I'm thinking about connecting it directly to 4 AA batteries and using a simple switch. Is there anything else needed?

Also, it its datasheet unit gcm is mentioned. What is it? I thought that torque is measured in N*m or similar units.


texts: How to calculate MOSFET internal gate resistance?

texts:
I was trying to figure out how to calculate the internal gate resistance of the MOSFET. For the purpose of analysis, Let's take the MOSFET as - BUK7Y3R5-40E

From most of the documents I read, best way to get the internal gate resistance is to measure it out.

With my current circumstances, I would like to go with a mathematical calculation but I could not find anything as reference.

Can someone suggest how to do calculate the MOSFET internal gate resistance.
If it is difficult to calculate the value accurately, any approximation will be sufficient.


texts: Can I use two Arduino digital pins in parallel to keep a higher voltage?

texts:
I'm using a digital pin as a supply to a sensor (should draw ~7mA).

Unfortunately, the sensor pulls the voltage of the digital pin down from 3.3v to 3.0v, which isn't enough for the sensor.

Can I tie two digital pins together and enable both of them to keep a higher voltage? Or will it release the magic smoke from my mini / do nothing?


texts: Why does the positive wave of my class AB amplifier output get clipped far below rail voltage?

texts:
For the past 6 months I've been designing and building a 30W 3MHz audio modulated Tesla Coil driver.

For this, I've created a +-15V linear regulated power supply, an AM modulator using an MPY634, and a class AB output amplifier which uses a 2SC5200 / 2SA1943 BJT pair.

The only thing that is still giving me trouble is the class AB output amplifier, which clips the positive half wave when the input from my signal generator goes above a certain voltage.

Here are the schematic and a scope shot:

I know clipping can occur when the output voltage reaches the rail voltage, but the rail voltage is +15V, while the positive output wave is only at +2V when it starts clipping.

Meanwhile, the negative wave remains a perfect sine.

I tried to simulate the circuit in EveryCircuit, but in the simulation everything looks fine.

Any idea what I am doing wrong here?

Thanks in advance for any help!

EDIT: Decoupling caps C1 and C2 were NOT present during my test, and my signal generator is an MHS-5200A

EDIT 2: Like @Transistor suggested, I measured the voltage between the two emitters, removed the signal generator from the circuit, and shorted the input terminal to ground.

The result is this 8.5Vpp high frequency (even though the crappy scope says 0 Hz) noise!

Is my power supply causing this? (A higher quality PSU is already on its way) Or is it indeed a problem with the biasing circuit?

If the latter, can someone please explain to me how to determine a proper biasing circuit? I've followed all kinds of tutorials, and apparently they are all missing something crucial.

ALSO, it seems like R2 is getting much warmer than R1.

It also seems like the waveform clipping is reduced as frequency is increased.

EDIT 3: I triple checked the connections, and they are correct. Then I measured the resistors, and they both show around 470 Ohms. Finally, I replaced the 1N4148 diodes with the much more bulky HER305 diodes, and now there is no clipping anymore...

However, these HER305 diodes have a forward voltage drop of 0.5V, which might not be ideal for biasing the transistors, which usually need 0.7V.

I ordered some 1N4937's to see if those would be a better fit (I am planning to push this amp up to 3 MHz, so I need fast diodes).

Thanks everyone for your help!


texts:
So while trying to interface a 5v SPI to a 3.3v SPI device, using the inline resistor method outlined below,
http://www.sparkfun.com/tutorials/65

I discovered that at high clock speeds (above 200khz), my clock signal was being corrupted by the inductance in the resistor (with an oscilloscope, the clock looks signal looks triangular shaped) I am using carbon film (through hole) resistors for prototyping and I heard that these can have high parasitic inductance and not suitable for high frequency use. Is this information correct?

What types of resistor instead should I be getting (digikey link would be appreciated)? Right now, I'm just working on a protoboard but eventually I would like to manufacture this prototype on a PCB using surface mount components. It seems like from what I read about surface mount resistors, the inductance is not typically a problem for applications under 20Mhz.


texts:
What's an appropriate sensor for cheaply and accurately measuring an angle of rotation?

I'm trying to measure the angle of a joint in a robotic limb using a small potentiometer mounted at the axis of rotation, and although it's small and inexpensive, it's accuracy and susceptibility to noise is horrible.

I need something equally small and cheap, but much more accurate.

The only other technology that comes close are hall effect sensors. I've seen some SoC that can detect a rotating magnet above them and output the angle as a signal. However, I can't find any of them packaged in a form that's as small as a potentiometer.

Do any of these come in small package sizes? What's their accuracy compared to a potentiometer measured with an ADC? How much more immune would a hall effect sensor be?


texts: Possible to power STM32 Nucleo boards with USB battery pack?

texts:
I have a wireless-transmitter module connected to a Nucleo board. The sensor draws power (~200 mA) from the Nucleo board's 3.3V out pin.

Case A (successful): When I connect/power the Nucleo board with a standard USB (5V) cable connection to my PC, then:

the transmitter module successfully transmits (I successfully receive packets on remote unit)

Case B (unsusccessful): But when I connect/power the Nucleo board with a USB cable to a Battery pack (one of those phone backup-battery packs with 5V output @ 1A), then:

I get 1.1 V for the multimeter reading on the 3.3V out pin of the Nucleo board
the transmitter module isn't transmitting (I'm not receiving packets on remote unit)
the Nucleo board's LD1 (LED) just continuously blinks at 1 Hz

Question: Is there some physical re-configuration I have to do to allow the Nucleo to be USB-powered by a 5V-Usb-out battery pack, and to successfully draw power (about 250 mA in my case) from the board's 3.3V out pin?

Here is the schematic of the Nucleo board including its power circuitry:
http://ds.arm.com/media/resources/db/platform/st/nucleo_f401re/MB1136.pdf


texts: Connecting solar panel and batteries of different voltages in series

texts: Will this work? What I want to do is connect a 12v alternator to a battery to charge it which would then be wired in series with a 24v solar panel, but hopefully isolating the voltage. Will this work? Will this give me ~= 36v that I can use to power my inverter?


texts: Small signal modelling of buck converter, varying frequency

texts:
It seems that the most popular method of voltage mode control of buck converters is by varying the duty cycle. Is this because it is easier to do so because we can set the duty cycle using PWM ICs?
How do I start small-signal modelling of a buck converter (DCM mode) keeping input voltage Vin and duty cycle D constant, varying switching frequency? I want to get the transfer function $$\dfrac{\hat{v}(s)}{\hat{f}(s)}$$
EDIT 1:-
For example, here's a question that asks to find this, [SMPC book, V Ramnarayan],

I'm not able to get the small signal model mentioned in part B, neither the answer to part C. I imagine a similar approach can then be taken for a buck converter.


texts: I am trying to build a low pass filter circuit from the LM358 datasheet from TI. Looking at the pinout and building the circuit I cannot get something basic like this filter to work. I have everything connected properly, with the GND pin (pin4) connected to the negative power rail and the  VCC pin (pin8) connected to the positive rail. I've been scratching my head over this the past couple hours, any help would be much appreciated.


texts: If a positive gate pulse is given to a forward biased thyristor, it gets turned on. What will happen when a negative gate pulse is given to a reverse biased thyristor ?


texts:
Info

So I've decided to hop on the ESP8266 WiFi module bandwagon and build a light switch with a couple of differences.

1) the light switch needs to go in the wall and be the same size as the existing panel light switches (deeper will be OK)

2) the circuit needs to pull power from the existing 250v power that runs through the switch

3) the light switch needs to contain a microphone so I can walk around the house issuing voice commands and each light switch will be able to hear the command and relay it to a central hub for processing.

4) the light switches will use the esp 8226's ability to be a wifi client and AP to create a mesh network so commands can be relayed around the house.

5) I need a design that an support up to 4 switches in one light switch panel.

Questions

1) What should I use to pull 5v from the 250v power supplier. I've seen switching power supplys but these are all fairly bulky and contain transformers. I was hoping that there was a smaller solution. I only need 250mA to power the device.

2) Can the esp 8226 be used to forward raw audio from a digital microphone. I would estimate the device will need to handle about 100Kbps given I probably won't have sufficient room on the device to compress before I send the data. So there are two parts to this question

a) is it possible to wire a microphone to the esp 8226 and capture the audio

b) can it handle 100Kbps

3) If I 3d print the panel and a mount box in PLA is that considered electrically safe ?

4) How much of a challenge is reception going to be if the antenna is in the wall? Should I expose the antenna on the switch face plate? As i'm designing the light switches as a mesh network there should be another light switch just a few meters away in most cases.

Sorry if the questions are dumb but I'm a programmer not an electrical engineer.


texts: Why doesn't my multimeter show the correct Zener reverse voltage?

texts:
I have a 3.3V Zener diode, brand new from a reputable source.

When I set my Fluke 101 multimeter to diode test mode, and put the black lead next to the dark bar on the diode and red on opposite side, the meter reads a voltage drop of about 0.689V. This would be the forward voltage of a "normal" diode.

When I reverse the leads, however, the reading does not match the expected reverse voltage. Instead my meter reads 1.746V. I tried also with a Fluke 87V which gave a slightly higher reading of about 2.2V, but still not the 3.3V that it should be.

Now obviously for most diodes, a multimeter will just read "OL" rather than finding the actual breakdown voltage (which could be quite high). Why in the case of a low-voltage zener do multimeters give wrong (and different to each other) readings of the reverse voltage?


texts: Why does a bipolar transistor not work, but a MOSFET does

texts:
In reference to my question Arduino Controlled Power Supply for more details and a test program.

Why is it that my circuit involving a transistor does not work (see below) whereas a similar circuit using a MOSFET does work?

Also, why is it that when the power is cut in the transistor based circuit, the Arduino dies instantaneously, whereas in the MOSFET based circuit, the Arduino gradually fades away over a period of 3-4 seconds? When I say it "fades away", the LED's will dim over that 3-4 seconds. It is like there is some capacitance that keeps it going until the charge is exhausted - but this does not occur in the transistor based circuit.

The idea behind this circuit is to maximise the life of a 9V battery powering the Arduino. The idea is to allow an external physical event (pressing S1) to power up the Arduino. Then, the Arduino, via Pin D2, will keep the power on after S1 is released until such time as it has done what it needs to do. Finally the Arduino will drop Pin D2 to a low state to shut off the power.

Following are the two circuit diagrams.

Firstly the transistor based circuit - which does not work (the Arduino dies as soon as S1 is released - and it dies instantaneously).

Secondly, the MOSFET based circuit - which achieves the desired result, but the Arduino gradually "fades away" when D2 goes LOW. This is OK, but it would be nicer if the Arduino powered down much more quickly.


texts:
What is the benefit of the double feedback of the LMV324 op. Amp.? Why was that implemented in that way?

From this scheme I have to understand why was implemented in that way


texts:
I’m measuring the voltage level from an Arduino Uno PWM pin using an oscilloscope. I’m using analogWrite(pin, voltage) in the loop with pinMode(pin,OUTPUT) in the setup.

I set the trigger to edge (rising), auto mode, but all I see is noise. Tried zooming in/out and moving up and down on the screen to find the signal at 3.3 V but couldn’t find it.

What am I doing wrong?


texts:
I'm looking to use a TPS61xxx series DC-DC boost converter for a charger, but I only want the converter to be active once the USB cable is plugged into the receptacle.

Now from my understanding, some devices look at the resistance on the end of the D+/D- lines and decide how much current the device is allowed to pull from the charger. So is using the data lines to activate the EN pin a bad idea? I'm assuming the IC has its own internal resistance, and that might confuse the device being charged. If that's the case, then what's the best way to send a signal to the EN pin to activate the converter when the USB is plugged in without using a switch?


texts: Triac snubber: Where to put current limiting phototriac resistor?

texts:
I have seen two variants for putting the current limiting resistor of the phototriac. One is to put it between R and C of the snubber circuit, the other one is to connect it to the triac terminal directly.
What is the difference between the two? Does the second circuit also protect the phototriac from voltage spikes (too high dV/dt)? Is one of those circuits better?


texts: Speed Current Relationship in İnduction Motors

texts:
It is said that speed of an induction motor depends on its frequency and torque depends on current. But I will explain what i cant understand here.

Let’s think an induction motor runs with constant load and speed. When I increase its current (by varying voltage) but keeping the source frequency constant (by vfd) what happens ?

For me, when i increase current it will cause torque to increase , when torque increase and motor will start to accelerate aftet it gets high speed it will find another point source and load torque trades off each other. In this way I don’t change frequency but motor gets higher speed by increasing current.

Is this assumption correct ? Or do i miss something ?


texts:
I am ordering parts to build an OSMC Motor Controller for a 24V system.
The schematics calls for LLSD101A , surface mount Schottky barrier diode.
I would like to use through hole components, but I cannot find an equivalent diode, mainly because I am not sure what parameters are relevant. If somebody could come up with a suggestion it would be greatly appreciated.
Also I am planning to use only one mosfet per side, as the Motor requirements are not huge ( 24V motor, 20 Amps max). Should I reconsider the value of the gate resistor in light of this, and what wattage rating should these be?
thank you


texts:
So i recently inherited a design as a new graduate, and am currently in the process of working on the next board revision.  The design currently calls for a 24VAC line to come out of a G6k relay, leaves the board via a connector, and eventually turns a larger contactor on in the boards housing.  The current design typically has 10mil signal lines, but for the 24VDC and 24VAC, the previous designer tried to use 20mil lines.
The problem is, in this case, he used 10mil lines for the 24VAC trace which eventually outputs to the contactor.  The good news is we are just powering relays with the trace.  I tested the amperage coming out of the relay on the board, and it is only about 230mA or so, which seems well within the thresholds for a 1oz 10mil trace.
I know this is a frequently asked question and I have been doing the reading, but would love an opinion from someone with a little more experience.  24VAC on a 10mil trace ok if we arent trying to pull too much current?  Seems like I could pull 4x that before I had to start worrying if i can trust these calculators to any extent.
Thanks for any help or guidance!


texts: can voltage divider from the R2 and R3 be used to drive two transistors simultaneously? I need the LED (with Q1) in this circuit to show the state of transistor Q2, i.e. be able to tell if Q2 is conducting.


texts: Large via vs several small vias for large current

texts: I'm currently routing a board and need to supply 12A between a current sensing IC and an ESC.  Due to size constraints I cannot have both the decoupling capacitor and IC on the same side of the board.  Is it better to use a single large via to pass this trace between the top and bottom sides of the board, or would several smaller vias be better?


texts: How many logic gates does it take to implement base-100 addition?

texts:
I'm curious about the trade-offs that have been made in implementing different kinds of arithmetic in different models of computers, to which I'm trying to understand what the costs of various options would be.
Say you want to implement base-100, using 7 bits to store a decimal number from 0-99. So you want an adder circuit that takes a pair of 7-bit inputs and produces a 7-bit output (still 0-99) plus a carry flag.
How many logic gates would this take, roughly, compared to the obvious alternatives of either 7-bit binary or 8-bit BCD?


texts: Point-to-point range measurement using an IR receiver

texts:
I am interested in using an IR receiver (as opposed to a standalone PIN photodiode or phototransistor) to measure distance/range. I thought I had found an appropriate match in Vishay's TSSP4P38 mid-range proximity sensor, which varies its pulse width with reflected signal strength. These, however, seem to only detect changes in distance as stated in p.3 of this document from Vishay; also, it's reflective and I want to be able to detect the distance (and possibly bearing using an array of IR detectors) from an IR emitter as depicted in the image below.

After my search, I have found only Vishay offers an IR receiver capable of outputting "analogue" information; is there an alternative IR receiver capable of measuring absolute distance I have overlooked? I would like to exhaust my IR receiver options first, before I look into using a photodiode/phototransistor which will require extra circuitry, such as amplification, filtering and demodulation.

Additional information: Range of ~2m to 3m and not too sure of accuracy and resolution at this stage, but possibly within ~10cm @ 3m.


texts: Determining a suitable Power Supply for a Light

texts:
I have an old multi-coloured LED lighting system, but sadly I have lost the power adapter to it and there are absolutely no markings (exterior or interior) whatsoever, so I am trying to figure out the power requirements so I can breath some life back into it.

The internals of the control box is a 78L05 regulator, connected to an ATMEGA88 microcontroller which, through a series of small SMT components I cannot make out the markings of but have assumed to be a transistor and resistor, link 3 outputs to the connectors that go to the lights via 3 J189 FETs.

The output from the FETs link to the 6 connectors to the lights, all wired up in parallel. Each light is a stick of 54 LEDs, 18 on each channel (linked to each FET). I cannot make out the internal wiring of the sticks, but I can see that they are subdivided into 6 sets, denoted by resistors every 9 LEDs.

I have tried to determine the resistor values, but they appear to be consistent on their channel, one channel is 470 Ohms, another is 200 Ohms, and the third is 240 Ohms.

So, in a nutshell, 108 LEDs with 36 470 Ohm Resistors, 108 LEDs with 36 240 Ohm Resistors, and 108 LEDs with 36 200 Ohm Resistors. I think that each smaller set (3 LEDs) are connected in series, then those are grouped together in parallel, totaling 36 groups, but each stick might be entirely in series.


texts: Amplifier for 100kHz magnetostrictive ultrasound emitter

texts:
I need an amplifier to drive an ultrasound emitter (inductive load, 120uH, 0.3 ohm). Single supply circuit would be preferable. Bandwidth - from 40 to 200kHz, output power 6-10W at 4 ohm load. The input signal is sine wave.

I tried TDA2050, but at ~15kHz it's output current starts to drop and at 100kHz it's only 80 mA. Also I found this circuit, but when I try to simulate it in Multisim, I get nothing at the output with ±12V supply.


texts: I have a sensor, the manual of the which says it has a maximum response time of 1 msec. Does it mean the sensor takes at least 1 msec to respond or at max 1 msec to respond? I am confused because providing least response time makes sense, and here it is given as max. So what does maximum response time denote? How should I interpret it?


texts: Unresolved symbols building a code composer 3 project in code composer 4

texts:
I downloaded a program from texas instruments, PMSM3-2, which is made for code composer studio 3. I only have code composer 4, when attempting to build it I get the errors:

'Building target: C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/build/pmsm3_2.out'
'Invoking: Linker'
"C:/Program Files/Texas Instruments/ccsv4/tools/compiler/c2000/bin/cl2000" -@ccsLinker.opt -o "C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/build/pmsm3_2.out"

 undefined                   first referenced
  symbol                         in file
 ---------                   ----------------
 _DLOG_4CH_init              C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _DLOG_4CH_update            C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_EV1_DRIVE_Init       C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_EV1_DRIVE_Update     C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_EV1_PWM_Init         C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_EV1_PWM_Update       C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_EV1_QEP_Calc         C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_EV1_QEP_Init         C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_EV1_QEP_Isr          C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_EV2_PWMDAC_Init      C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_EV2_PWMDAC_Update    C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_ileg2_dcbus_drv_init C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _F281X_ileg2_dcbus_drv_read C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _clarke_calc                C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _ipark_calc                 C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _park_calc                  C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _phase_voltage_calc         C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _pid_reg3_calc              C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _rampgen_calc               C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _rmp_cntl_calc              C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _speed_est_calc             C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _speed_frq_calc             C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _speed_prd_calc             C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj
 _svgendq_calc               C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/obj/pmsm3_2.obj

error: unresolved symbols remain
error: errors encountered during linking;
   "C:/tidcs/DMC/c28/v32x/sys/PMSM3_2_281x/cIQmath/build/pmsm3_2.out" not
   built

>> Compilation failure

Is there something I need to change to make it work with ccs4?


texts: Interpreting scattering parameters on a Smith chart.

texts:
I'm trying to become reacquainted with microwave circuits and how to analyze them, especially with a VNA.  Just to get some practice I'm using Keysite ADS simulator.
To get the feel of it I used the circuit below as a test, and analyzed it.  It's a simple band-pass, the resonates at 5GHz.

My issue that I'm having is interpreting the Smith chart results.  By my understanding at 5GHz, the input to the filer, S11 should be 0, with maybe a phase change, and also the reflection coefficient should be 0.  In the Smith chart below, at resonance, 5GHz, it shows S11 as being ( 1 + i0 ).  This doesn't seem to make sense to me.
Looking at the other graphs of S11 and S21, they seem to makes sense,  where at 5GHz S21 goes to 0 dB and S11 goes to very low, meaning %100 of the signal from port 1 goes to port 2 as you would expect. The Smith chart doesn't seem to show the same thing.  I would expect it to show 0 at resonance.
So what is the meaning of the S11 plot on the smith chart?
Or, is the Smith chart not appropriate for plotting S parameters?
I figured that with S parameters being complex they would normally be plotted on the smith chart, but what I'm seeing doesn't seem to make sense to me.
Or is the issue just with the way that ADS plots S parameters?  Would I expect the same plot on an actual VNA on the Smith chart display.

BTW, I'm also including magnitude and phase charts of S11 to show that those reading are behaving as expected.

S11 and S22 below, with marker at 5Ghz resonance.

S11 Magitude.

S11 Phase/Magnitude


texts:
I need to put dipoles antennas in a restricted area with lot of movement. I'm wondering if I fasten the end of the antenna will affect performance, because the fasten needs to be grounded.

Is like when human touch TV antennas can improve signal reception because body acts as an extension of antenna. Or in a oppositive way when touching Iphone 4 can degrade signal quality because your fingers are in contact with antennas (http://ipod.about.com/od/iphonetroubleshooting/qt/Iphone-4-Antenna-Problems.htm).

The difference is that no human is touching the antenna but a plastic fasten.

Hope that the following diagram could help.


texts: How to find the Thevenin equivalent circuit

texts:
What will be the current at A-B if a 12 Ω resistor is connected across this terminal?

Please I need equations/solutions.


texts: Need help calculating resistance for transistor base

texts:
I have 3 12VDC/40A automotive relays (datasheet) that I want to use with my Arduino.
Based on the tutorial I am following (link) I need transistor, resistor, and diode. I am not an electrical engineer therefore I am unsure about the parts and calculations I made.
For the start, relay coil resistance is 90+-10% Ohm per datasheet. So I proceed by calculating the current flow.

Voltage=Resistance*Current
Current=Voltage/Resistance
Current=12V/90
Ohm Current = 133mA

For the transistor I can get 2N3904 or 2N4401. At this point I have to calculate resistance for the base of transistor. In tutorial its as following

hfe = Ic / Ib
Ib = Ic / hfe
Ib = 0.03 A / 75 Ib = 0.0004 A => 0.4 mA
R1 = U / Ib
R1 = 5V / 0.0004 A
R1 = 12500 Ohm

2N3904 datasheet states the H(fe) is 30-300 when lc = 100mA (mine is 130mA) and Vce = 1V. At this point I have no clue what is going on, thus I need help.
Edit:
Here is what I ended up with. RLY1 in the picture is 12VDC/40A (link)


texts: whats the difference between a cascaded band pass filter and a normal band pass filter (Audio visualizer)

texts:
simulate this circuit – Schematic created using CircuitLab

currently im building an audio visualizer i would like to know what is the difference between a cascaded 2nd order band pass filter and an inverting band pass filter.
which type of band pass filter is the best to be used in building an audio visualizer.
i would like to get some feedback on what are the stages for building an audio visualizer.
based on my knowledge there should be several band pass filters to separate the frequencies based on my preference. then the signal should be rectified using a diode and a capacitor , and the output will be connected to the LEDS , in my case im using the LM3915 led driver.
i would like to get some feedback to improve my design and what would be best to build an audio visualizer.

thank you


texts: Reduce the output current from a stepper driver

texts:
I have to control 2 stepper motors with a single driver (multiplexing one at a time) and both motors are different, one 1.7A and the other 0.4A, if I set the current to 1.7A the 0.4A motor can burn out. Is it possible to put resistors at the output of the driver to reduce the current? How could I calculate it?

edited: the motors are
1.7A=17HS4401S, resistance per phase: 1.5 ohm
0.4A=JK42HS34-0404, resistance per phase: 30 ohm


texts: over and critically damped systems settling time

texts:
I know that for second order systems the settling time(St) equation is:

So my question is, should this same formula be used when the system is over or critically damped? Is it right to use it in that cases?


texts:
I have an ESP-WROOM-32 (I2C master) and an ATmega328p (I2C slave, address 0x03) assembled on a prototype PCB using external 6k8 pull-ups.

I'm using the ESP's default I2C pins 21 (SDA) and 22 (SCL) as I always did, but when running the I2C scanner below, I do not observe any communication on the bus. SDA remains on high, SCL on low.

The same sketch works as expected when I flashed it to another individual ESP32 (there I see communication on the bus and the slave is recognized at address 0x03).

I'm very confused by that!

I'm pretty sure there is no hardware issue on the PCB, because I verified it on a breadboard before giving it to the manufacturer and I have also tested the circuitry with a multimeter after the assembly. Also toggling pins 21 and 22 in software with high frequency works as intended.

When I connect the other ESP32 to the same hardware, the signal has sufficient quality and is (at least) there.

As there is nothing magic about my PCB (SCL/SDA lines are about 1" long with no slave assembled, nothing else), I don't think posting my layout will be necessary (and I'm also concerned about posting it publicly as it's the property of my company).

I have no idea how the problem could be in my PCB, but as my previous thread was closed in the SE software section as "off-topic", I hope to find some answers here.

Has anyone made experience that too high pull-ups suppress signal transmission completely?

Is it reasonable that I partly destroyed the ESP through soldering (using a self-made reflow station which up til now did a great job). As I had no problems with other features at all, that does not seem to be likely.

At least some information I provided in the software section.

Before debugging with my oscilloscope and believing in a software fault, I flashed sketches that use the Wire.h, drivers/i2c.h and /peripherals/i2c.h, where I2C was set up on different pins (right now I don’t have access to those pins due to shielding, so I can't check if there is a signal output).

It seems like the interface was not even initialized? I can’t imagine I have a faulty chip...

Any ideas?

This is the I2C scanner I used (but I reproduced the problem with anything I did with Wire.h, drivers/i2c or peripherals/i2c.h):

#include <Wire.h>

#define SDA_PIN 21
#define SCL_PIN 22

void setup () {
  Wire.begin(SDA_PIN, SCL_PIN);
  Serial.begin(115200);
  Serial.println("\nI2C Scanner");
}

void loop () {
  byte error, address;
  int nDevices;
  Serial.println("Scanning...");
  nDevices = 0;

  for (address = 1; address < 127; address++ ) {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();
    if (error == 0) {
      Serial.print("I2C device found at address 0x");
      if (address<16) {
        Serial.print("0");
      }
      Serial.print(address,HEX);
      Serial.println("  !");
      nDevices++;
    }

    else if (error==4) {
      Serial.print("Unknown error at address 0x");
      if (address<16) {
        Serial.print("0");
      }
      Serial.println(address,HEX);
    }
  }

  if (nDevices == 0) {
    Serial.println("No I2C devices found\n");
  }
  else {
    Serial.println("done\n");
  }
  delay(1000);
}


texts: I am analyzing a JFET. The datasheet has both information about the currents Igss and the maximum of Ig. I know that the Igss is a the reverse current in the PN junction but I can't explain myself what kind of current is Ig and when does it flow?


texts:
I was reading a chapter in a textbook on Infinite Impulse Response filters. The author in the beginning of the chapter states that" impulse response h(n) for a realizable filter is "

h(n)=0 for n<=0

Can anyone please tell me why?
If the answer to this question is lengthy please feel free to suggest any websites/links where I may find the answer to this question.


texts:
I have 2 boards that are normally stacked on top of each other using 2 x 7 pins 1mm pitch connectors. I'd like to separate them by a foot or so. But I can't find an extension for that pitch. What would be the alternative possibilities?

PS: this is not meant to be a product recommendation question but a quest for a solution to an actual problem.