texts: How to model MIMO channel matrix for numerical results

texts:
I am willing to include the channel matrix in my analytical model (which only includes pathloss and antenna gains). But from what I have seen, channel matrix can't be used to produce numerical results in an analytical model because it relies and should be based on real device tests.
Is my way of thinking wrong in this problem?


texts: Why is there so little interest in powerline communcations?

texts:
It seems that a power line protocol would be a really good way to help increase the range and reliability of wireless IOT networks. Wireless networks are always going to have areas that are hard to reach, even with mesh topologies, and it seems like power-line communication is an obvious choice to bridge gaps in low bandwidth networks. Yet new IOT standards like Thread have no provision for integrating power-line communications.

Is there a technical reason for this to be the case, or is wireless just a "sexier" topic these days? I notice that available standards, X10 and UPB are closed and have royalties. Is the lack of a reasonable, open standard discouraging adoption?


texts: How to handle disconnected resistive sensor?

texts:
I'm trying to connect a PT100 thermo probe to an Arduino project to measure water temperature. After some research I have found and adopted a design using a Wheatstone bridge and an instrumentation amp, attached below. Using this arrangement I get 0V at the output @ -15°C and 3.3V (Vcc for the Arduino) @ 125°C, which is perfect for my application.
However, the temperature probe is designed to be disconnectable, which would create floating inputs. How could I alter the schematics to make sure that when the sensor is disconnected the differential inputs are at the same voltage, so the output also reads 0V?


texts: Handling Transient Currents on USB Powered Devices

texts:
I'm working on a USB-powered speaker design and could use some thoughts or design inputs from the community.

The data part is pretty simple - USB powers an I2S bridge that talks to an I2S amplifer. The power, however, is more challenging because I am trying to handle significant transients on the load while respecting the 500mA USB limit.

That pretty much translates to a current limit circuit that limits to 500 - (sum of all other chips usage) mA on the input. A large capacitance on the output of the current limit is meant to be the buffer to handle transient currents. This capacitance tied to a boost converter powering the amp should do the trick, right? Nope.

A boost converter's input voltage linearly affects the output current, and at the lowest input voltages, the output current is limited to 200mA on average for most parts I've looked at thus far. There is a compensation to be made in how low you set the voltage swing over the reservoir cap(s) vs output current of the boost.

The goal is to deliver the 500 - (sum of other chips) mA to the amplifier in normal operation, and adding up to 1 more Ampere with the aid of the reservoir cap and the boost circuit during transients. What I'm having a tough time figuring out is the right parts and the right capacitance for this design. I'm also willing to start the power part of the design over from scratch given a better solution.

Looking forward to hearing your thoughts on what a good solution would be.


texts: Not able to power motor with the L298N motor driver

texts:
I am trying to make a robot and I have some problems with the L298N motor driver. I supplied it with 9 volts and used its 5 volts output to one of the pins. I put two motors at both motor outputs and the motor doesn't move or it erratically moves.
I measured the voltage across several points:

I tried measuring the voltage across the two input terminals and it was 5.1 volts.
When I took out the motors and measured the voltage between the output two output terminals for one of the motors it was 5 volts.
When I put back the motors and measured the same terminals again it was 0.2 volts.
When I replaced the motors with LEDs, the LEDs lit and the voltage between the terminals was 3.6 volts.

My question is why does the voltage across the output terminals so low when we connect the motor?


texts: Why are resistors necessary in a summing audio circuit?

texts:
I am researching DIY stereo audio mixers (2 input, 1 out) -- there's lots of info out there -- but all the passive solutions (e.g., DIY Multi-Input Audio) include resistors, and I don't understand why they are necessary at all, especially given that adding any resistors to an audio signal reduces the volume.
I just want to know why the resistors are considered necessary, and what happens if you don't include them and just wire together left/right channels.


texts: Simulate WiFi Stations for testing the AP

texts: I was thinking if I can simulate WiFi stations(around 5 numbers) in my laptop, that I can try associating these stations to my AP and load test the AP. Could some one suggest on this or is there any alternative way other than procuring real hardware WiFi stations?


texts: Strange behavior from variable-gain amplifier

texts:
Sorry, this might not go anywhere. My first SE question, though, on any site.

I've built at least three distinct audio amplifiers with the TDA7056B, which is a really great amp. It takes a voltage between 0.4 and 1.2 V on pin 5 to control its gain. In the first two versions of the circuit, I used logic ICs and/or counters and an op amp with a resistor network for a DAC to provide the voltage, and all worked well. This last week, I decided to try my hand at doing the same with an Arduino doing the logic work, and instead of an op amp DAC, I'm filtering a PWM signal and feeding it to a darlington-pair voltage follower. It took a while to get it right, but now it works. The odd part is, the voltage range that produces the correct gain variation is completely different: 1.22 V to 2.25 V. I'm happy that it works, but I'm very curious as to why that is.

The linked data sheet has all the information I have as to the voltage control and everything. Here's what the filter and voltage follower looks like:

simulate this circuit – Schematic created using CircuitLab

Now, as for what I've tried/thought of:

I have taken into account that there's a voltage drop accross the darlington pair. I'm measuring at the pin.

I checked the voltage with an oscilloscope, and while it is noisy, there doesn't seem to be anything of the PWM signal in there.

I tried switching the IC with another on hand, and it works the same.

My current theory is that it has something to do with the way the pin interacts with the circuit. Perhaps it's not exactly the voltage at the pin, rather the current that flows in or out at that pin (which varies between +/- 25 µA), and perhaps this solution does something different about that.

So, why is the voltage not what's described in the data sheet? What did I do differently?


texts:
I'm trying to build a motor driver which can supply ~3A per motor. Only cheap IC I could get my hands on was L298, so I decided to parallel its channels.
But for some reason that I can't understand (I'm merely an amateur hobbyist), L298 and its diodes are getting too hot in just a matter of seconds.

I'm using a 12V (max 40W) power supply for my circuit, and its reduced to 0.95V when I check VCC/GND pins (how is that even possible ?)

This is my PCB design.

47uF capacitors,

1N5819 diodes,

L298N

Edit:
Schematics


texts: Do lithium-ion batteries just lose capacity over time or do they also become more wasteful?

texts:
My question is if lithium-ion batteries just lose capacity over time or if they also become more wasteful. From a practical perspective, can you easily get around loss of capacity in older batteries/devices by just carrying a powerpack or would an older battery also use up more power in a certain amount of time, thus draining the powerpack faster?

This is coming from a consumer perspective but I hope it's still interesting enough to be answered here.


texts: Project Loon 20KM LTE transmission from Regular Handset

texts:
i read this question before asking. how does a cell phone transmitter work?

i am very confused about Google Project Loon. I understand the balloons will be transmitting LTE from 20KM up in the sky.But i am sure there will be enough transmission power in the balloon so the signal can reach the ground. But how does a consumer handheld LTE device going to be able to transmit 20KM up to the sky and still be able to keep battery life?

What i am missing ?


texts:
I'd be much obliged if somebody could point me to a short ISE workflow tutorial that shows how to implement a simple circuit using VHDL.

As indicated, the tutorial should be short as I'm not interested in all bells and whistles of the ISE GUI: it would be neat if somebody could explain how to do things from the command line in UNIX.

The simpler the circuit the better: a logical and should do.

Thanks in advance for your help.


texts: logic circuit for 2 push buttons bitshift

texts:
I'm trying to understand how I could implement, using logic ICs (and not a uC), the following:

there are two momentary push buttons and 3 leds.
The leds indicates the logic "state", that can be 0 (initial), +1 and -1.
Pressing the push buttons, you change the state.

I drawn this little diagram that should help to better understand the topic.

So at the beginning you are on state 0 (and the middle led is lit), if you press +1 you go to state +1 (and only the +1 led is lit). If you press again +1 nothing happens. And so on..

How can I get that using a logic circuit?
so far I only understand how to make the switches to latch using D-FlipFlop


texts: Operational amplifier (UA741CP) not working in buffer configuration

texts:
I am trying to use UA741CP operational amplifier. To test it I wanted to create a buffer circuit in which input voltage would be equal to output voltage. I use 5 V DC as my supply rail. A voltage divider is used to reduce the input voltage of OpAmp (100k 1st, then 10k) which gives 0.45 V (V_in).

But when I measure V_out I get 1.82 V. Moreover, I can completely disconnect the non-inverting input (+) and it remains the same. Also I noticed that when I connect the OpAmp into the circuit the output voltage goes from around 1.8 V to 1.82 V in a couple of seconds.

Do you have an idea what I might be doing wrong?

simulate this circuit – Schematic created using CircuitLab


texts:
There are various types of bus couplers (for double bus system, single section bus system, etc.).

I know that bus coupler between two busbars is called cross bus coupler.

How are other bus couplers called, how do we divide them by type?


texts: Can we make Colpitts Oscillator adjustable?

texts:
Collpits oscillator is one of the most widely used oscillators.

It's frequency equation is like this:

According to the equation, we can change its frequency by changing its LC tank parameters L and C. However, making adjustable capacitors and inductors are not much realistic. Also, their capacitance and inductance value can not vary that much to obtain \$f_{0}\$ - 100x\$f_{0}\$ oscillation frequency range.

So here is my question, how can I make this oscillator adjustable in a way that it can oscillate to 100x\$f_{0}\$?

Note: We can add any digital or analog block to the circuit to realize the goal.


texts: What is the purpose of transistor in this circuit?

texts:
"A zener diode voltage regulator is inefficient when the supply is used with equipment that draws high current. When a supply must deliver a lot of current, a power transistor is used along with the Zener diode as shown  below"

After reading this statement,I still not understand the benefit/purpose of transistor in this circuit. Please can you explain further this statement?


texts: Will this schematic work as a four-bit shift register?

texts:
simulate this circuit – Schematic created using CircuitLab

Will this work as a four-bit shift register? (And by extension a shift register of any size?) Each vertical PMOS / NMOS transistor pair acts as a multiplexer, and the PMOS transistor to its left amplifies the voltage back up to close to V_high. I'd be interested in hearing people's feedback on this. Right now I have only three transistors (and a resistor) per bit. Can I really get it that small a ratio, or are there reasons why I need more transistors per bit?

It's probably worth noting that I don't have master/slave here, so I can only assert (Shift) long enough to move one bit toward the right and no more.

Furthermore, I'm not trying to say that I need a resistor with 100 ohms. That appeared to be the only resistor I could use to make this schematic! What I want is a resistor that has significantly less resistance than the PMOS it's next to when it's at high impedance, but enough resistance to prevent a short circuit from V_high to ground when that transistor is conducting.

Okay, now I've changed each of the BJT's to MOSFET's, and reduced the resistance of each resistor from 100 ohms to 10 ohms. I'm still going on the assumption that (shift) will only be asserted long enough for the gate delays of M4 and M5, and then of M6, so the value of (dataIn) will only make it to M6's output, and won't move to M8 until the next time (shift) is asserted. Is this enough to get this circuit behaving like a four-bit shift register?


texts:
Computer A has an overall CPI of 1.3 and can be run at a clock rate of 600MHz.
Computer B has a CPI of 2.5 and can be run at a clock rate of 750 Mhz. We have a particular program we wish to run. When compiled for computer A, this program has exactly 100,000 instructions. How many instructions would the program need to have when compiled for Computer B, in order for the two computers to have exactly the same execution time for this program?

  (CPUTime)A = (Instruction count)A * (CPI)A * (Clock cycle Time)A
   = (100,000)*(1.3)/(600*10^6) ns

  (CPUTime)B = (Instruction count)B * (CPI)B * (Clock cycle Time)B
   = (I)B*(2.5)/(750*10^6) ns

The result should be 65000

However, I'm unable to get there.

  The first calculation gives me 0.00022ns = ~2s

  2 = (I) (2.5)/(750*10^6) ns -- I can't solve this to be 65000

What am I missing here and how can I simplify it?

Thanks


texts: Change LED blinking frequency depending on voltage

texts:
I'd like to make an LED blink with a varying frequency that depends on a voltage. I know about the 555's control pin, but I'd like the blinking to vary continuously, instead of switching between just two states.
The circuit will be used as an indicator to give the user a clue about how close to a target voltage he has adjusted a value. As a rough guideline, let's say "0Hz at 0V, 10Hz at 5V". The exact values are to be determined later, depending on the usefulness of this indicator.
I'm not very familiar with the 555, so I'm not quite sure where to start. I only ever built example circuits and changed part values to get the desired frequencies, but I guess so far I haven't learned enough about the chip to tackle this project.
I don't have to use a 555, however that's what I have at hand (and the problem smelled like 555). BUT please note that this has to be an analog (or discrete digital/74 logic) circuit. No microcontroller allowed. I already know how to solve this problem with a micro and I know that this is probably cheaper/easier/smaller with one, but I absolutely cannot have a software component for several reasons that are beside the point of this question.
So can someone please point me at an example circuit or give me some hints so I can learn what's needed to understand an build such an indicator feature?


texts: Can I pull 2 amps through 22 AWG stranded wire?

texts:
I have a spare cable with four stranded 22 AWG-wires in it. My intention is to run 5V at 2A max (~0.9-1.0A normal) through two of them and I'm trying to find out whether this cable will suffice.

Reading on Wikipedia about AWG I find that 22 AWG has an "ampacity" of 7A. But, the table also mentions "60 C" and "Ampacity, at 20 C insulation material temperature rating, or for single unbundled wires in equipment for 16 AWG and smaller", and I'm not entirely sure about what this means.

Does the table mean that 22 AWG can handle 7A, and when that happens the temperature will go up to 60 C? If not, what are these temperatures in the table?

My cable will be 10-15 cm long. Not longer than 20 cm, and the average current through it will be around 0.6-0.9A but for some occations (short circuit or the like) the current will go up to 2A. My over current-protector cuts all supply when the current reaches 2.5A

So; will 22 AWG stranded cable work here, or should I look for another?


texts: Using Single Ended Output with Differential Input by Grounding one Input

texts:
I am making a frequency generator using the AD9833 (programmed from the PIC16F876). I wish to use a Programmable Gain Amplifier to adjust the signal level before being sent to a power amplifier (common collector coupled to class AB Push Pull). I have found several PGA's which fit the bill, for what I want, BUT...

The output from the AD9833 is single ended. All the PGA's I have found which fit my requirements use differential input. So my question is:

To use a differential input with a single ended device can I just ground Vin- and put my signal on Vin+ ???

This does stand to reason, but is there anything I have overlooked?


texts: What can I use to supply 220V DC to this motor?

texts:
I have a small 220VDC motor I would like to drive via a speed controller, so I can continuously adjust the speed. I'm in Australia with 240V mains, and I also have an adjustable 0-220V AC controller. It seems to me the missing piece is a rectifier to take the output from the controller to DC. A couple of questions:

First, is that a good approach?
Second, my understanding of rectification is that the output DC will be higher voltage, is that correct? There's a fair bit of mixed info out there!
If that's the case, am I going to have trouble if the max output voltage from the controller is multiplied before hitting the motor (220V * rectifier multiplier > max motor voltage)?

If there's a better way of doing this, I'm all ears. In my head an easy solution would be to use a voltage controller that outputs DC, but I can't find one with the right specs (apart from the large, workbench style power supplies, which are no good for my application).

Lastly, the components I have are spec'd at 220V, but it seems that 220 and 240 are treated as equivalent. Is that right?


texts: Why doesn't OrCAD show zero voltage here and can I fix it?

texts:
I designed this simple circuit here :

as it can be seen the software shows \$-8.572pV\$ (I assume it means pico volts).
But shouldn't it be \$0V\$? Is this some kind of error due to computers being limited to finite bits or something?
Also can I get this to \$0\$ or is this the best I get?


texts: How can I decrease power losses of H-bridge with 4 N-channel MOSFETs?

texts:
This is my H-bridge circuit. I need to change the polarity and found this circuit from the site. I need 0-200 amperes for the load. I want to use the IRF1404 and parallel them, but I have two problems:

First, there's a lot of power losses on high side (for this example: 1.55 x 5 = 7.75 V.) How can I decrease the power losses?

Second, what diode should I use for back EMF (VCC = 12 V, I = 200 A)?


texts: Why Did My NPN/PNP Voltage Regulator Experiment Explode?

texts:
I have been looking at ways to derive low voltage rails from a higher voltage and current supply, which in practical terms is about 53-0-53V from a linear power supply (toroidal, bridge rectifier and electrolytic caps).

I naively thought that the circuit below should produce a nice 30V across the test load R3, instead I got a dead zener diode and a nice explosion from transistor Q2 which was somewhat unexpected and disappointing. It actually blew its middle leg off, the poor thing.

The idea is to get +15V and -15V rails to power an op amp or two. I expected that R1, D1, and R2 would drop respectively 38V, 30V and 38V and thus, like a pair of standard series regulators, Q1's emitter would stabilise at 15V (relatively to the hypothetical 0V rail which isn't there) and likewise the collector of Q2 would be at -15V.

What have I done wrong? I am wondering if I've misunderstood the current flow through the PNP, they always make my brain fry because of the reverse sort of nature of them. Anyway, what's my mistake?

simulate this circuit – Schematic created using CircuitLab

update:

The zener is now a 1N4751A, 30 V at 8.5 mA, see these specs.
The zener resistors are now 4K7 for a zener current of about 8.5 mA.

After adding voltage sources the simulation runs and results in about +/- 2.54 V over the zener and +/- 2.1 V over the output resistor.

Strange! Either the simulator does not know that the zener zeners at 30 V, or the transistors draw a lot of base current, but with such a big load resistor that is unlikely.


texts: Can a "static" magnetic field carry Information?

texts:
Information is electronically represented as some energy that is changing, therefore we measure an on state (1) and an off state (0), to create a (0,1) binary representation of the information.

Now a static magnetic field by definition has a frequency of 0 Hz, so frequency modulation can't happen. But what if we modulate the amplitude? (Tesla), would that consist as a static field?

Can an amplitude modulation work to send information from an electronic device that creates a magnetic field with constant frequency?
What if the device is already electrically shielded, as this is a follow up to my previous question. If we already have a device that is sufficiently electrically shielded, can information leak out from the magnetic field via amplitude modulation?

I am specifically interested how can / if possible / information leak out from an electrically shielded device by modulating a magnetic field.

EDIT: I made the question more precise. Referring specifically to the relationship between amplitude modulation / frequency modulation, and a static magnetic field. I believe a magnetic field with 0 frequency is only static if the amplitude is constant as well, reading the answers below.


texts: Common mode feedback for current mirrors

texts:
I was reading the chapter about Op - Amp design in Microelectronic Circuits by Sedra Smith, and I have some questions about the so called "common mode feedback" (CMFB) which is used to control some current mirrors.

Let's consider this scheme:

The book says:

  Relying solely on matching will not be sufficient to ensure that the
  currents supplied by Q9 and Q10 are exactly equal to the currents supplied by Q7 and Q8. Any
  small mismatch \$\Delta\$I between the two sets of currents will be multiplied by the large output
  resistance between each of the collector nodes and ground, and thus there will be large changes
  in the voltages vO1 and vO2. These changes in turn can cause one set of the current sources
  (i.e., Q7
  −Q8 or Q9
  −Q10) to saturate. We therefore need a circuit that detects the change in the
  dc or common-mode component VCM of vO1 and vO2,
  VCM
  = 1
  2
  (vO1
  +vO2)
  and adjusts the bias voltage on the bases of Q7 and Q8, VB, to restore current equality. This
  negative-feedback loop should be insensitive to the differential signal components of vO1 and
  vO2; otherwise it would reduce the differential gain. Thus the feedback loop should provide
  common-mode feedback (CMF).

I have the following questions:

1) How is it possible that for instance current of Q9 is different from that of Q7? Their channels are in series (since the load is supposed to be of infinite impedance) and so, by kirchoff current law, all the current through Q9 should go on Q7, I think...

2) Does the book refer to DC or signal currents?

3) Why do we decide that the CMFB has to read the common mode voltage? Suppose there is a mismatch between current of Q9 and current of Q7: there would be a spurious value inside vO1. Which is the link between this spurious voltage, and the common mode voltage between the outputs in 1 and 2?


texts: How can I power my device using a Solar Panel and capacitor bank?

texts:
"I want to power a module that requires 3.3V and 500mA minimum for startup. I have a solar panel that outputs max 3V at 70mA and a 3.3V 3A max output boost converter. I know I need a super capacitor or a capacitor bank to store energy so I can get the current needed for start up. Also, my module only needs around 500mA for less than 1 second. I will probably consume an average of 10-40mAh.
I do not know too much about power electronics, but I want to know how can I design a capacitor power bank circuit that can handle 3.3V, can store a minnimum of 500mA, only takes less than 5 minutes (if possible) to charge the capacitor bank to 500mA, discharge the current for 30ms or more and have the capacitor discharge when full.
This 500mA current is only required once per day or when the solar panel drops below 1V.
I only want my device to be on during the day."
Above was my previous question. Below is my new information!

My size requirement is a 2x2 solar panel
Cannot have a battery, customer wants power only during day or peak
hours
The figure is what I have been calculating on the wattage required

Will this work?

I have purchased the evaluation board for the boost converter and set
a breadboard circuit up with smaller capacitors and supplied voltage
to a red led, but it doesn't have consistent power, it blinks fast
like a relay.

Also, when i supply this power to my wifi module, will this provide consistent power throughout the day after the startup requirement?


texts:
Ive made my own 18650 cell tester that:
Fully charges -> fully drains -> partially charges

It takes 4 cells, measured independently of each other.
While testing the drain circuits (charging circuits were not made at this point), all was perfect

After doing the charging circuits, cells 2, 3, 4 work perfect but cell 1 has the drain circuit on all the time (700mA drain) regardless of whether the mosfet gate is high or low.

Ive replaced the mosfet and 10k pull down resistor but still the same behaviour.

The voltage dividers for cell 1 read lower total resistance than the other cells too..

Can somebody look at these diagrams i made for myself while planning the build and point me to a probable cause?

Ive been over it with a fine tooth comb and all the cells wiring is identical!

Thanks in advance

EDIT:

Voltage divider resistances (measured from one end of the 10k to the other end of the 3k)

V divider before shunt

Cell 1: 5.1 ohms

Cell 2: 6500 ohms

Cell 3: 6500 ohms

Cell 4: 6500 ohms

V divider after shunt

Cell 1: 4.2 ohms

Cell 2: 6500 ohms

Cell 3: 6500 ohms

Cell 4: 6500 ohms


texts: How can I calculate Ampere Per Hour if Intensity has been given

texts:
Today I had an exam on Technology, and there was a question:

  If a nano robot has a battery of 2.15Ah(Amper per hour) , how much it will last without recharching , if the robot spends 1.8I(Ampere) in continuity. Solve that on minutes!!

I did it this way, 2.15A*60Min/1.8A = 71 min , Am I right?

Thank you so much!


texts:
I'm trying to implement a poor man's amplitude modulation by multiplying analog signal with PWM output.

The simulation result:

Why I get negative voltage? How it can be?


texts:
Before I ask my question, I should say that I am very new to working with electronics and I may not quite know how to describe my problem.

I am trying to use a pin on my msp430 microcontroller I have as a replacement for a pushbutton on a device. The msp430 is 3.3v and the device I am switching is 5 volts. I was under the impression I could use a 2n3904 transistor in place of the button by applying current by turning on the pin on the msp430 which would let current go from the collector to the emmiter, and hopefully "push" the button.

This is my current setup

However, turning the pin on does not activate the circuit. When I connect the jumper for the onboard LED, I can verify the pin is working. also, when I connect the 5v from the collector to the base using a wire, I can activate the transistor.

What other information am I missing to solve this?
Thanks in advance

EDIT: After reading the comments, adding a 4.6k resistor between the base and IO pin and connecting my 3v ground and 5v ground allowed me to control the transistor without any noticeable problems. Thank you!


texts: How can I find failure rates and probabilities when there is no information available?

texts:
I am conducting a risk assessment study of a system. To do so, I need to know the failure probabilities of its components. Some manufacturers do include this piece of information in their datasheets, other manufacturers don't and in the worst case some manufacturers don't even have a datasheet.

For example, I have been able to find the failure rate for the ATmega128 on page 8 of the datasheet:

  Data Retention

  Reliability Qualification results show that the projected data
  retention failure rate is much less than 1 PPM over 20 years at 85°C
  or 100 years at 25°C

On the other hand I have been unable to find any useful information for the CYRF6936 in the datasheet.

Finally, I can't find any datasheet for a linear B5K potentiometer.

Where/How can I find/estimate failure rates and probabilities when there is no
information available?
Are there any known generic failure rates/probabilities for
electronic components such as sensors or potentiometers?


texts:
I have a stepper motor(with STR2 Step Motor Drive) which needs npn sinking signal to operate. dsPIC33EP512mu810 is capable of generating high resolution pwm. However, the PWM signal can only turn on a LED but not the motor.

It works if I manully switch a pin on and off with some delay to operate the motor.
I've searched through data sheet and app notes but PWM output type is not mentioned. Any suggestion on PWM signal type and how to convert PWM into npn sinking signal?


texts: Feasibility Question - graphic acceleration on CPLD / FPGA ...DSP?

texts:
I am a programmer new to electronics. I wanted to get a perspective on wether Programmable logic is feasible in allowing a basic math algorithm to be accelerated.

Wanting to solve a ray-intersection algorithm (few multiplications and subtractions ) over a grid of 800x600 (480000) numbers. [I understand that integers would be ideal, and control logic is frowned upon - these constraints I can work around]

Everything I have researched so far says that I can offload this processing from a processor onto a FPGA could be programmed that would calculate the problem space in a very efficient manner.

few questions:

I am thinking of using a CPLD - perhaps literally an Altera MAX® 10 - does this provide the right scale device to get this type of problem set complete ?

If I wanted to calculate the problem set 100/sec would that be possible?

(assuming performance is a problem) Can the problem be easily divided amongst different chips - where each chip wrote it's solution to a different region of ram?

Is this sort of project feasible to attach to a lightning bold/ usb3 / sata or pci express slot in a PC ?
- what type of investment does it take to create a board that sophisticated (timing-wise)?

Could this be done with DSP chips? (I'm having a hard time understanding where DSPs are no longer useable - I understand there typical use in filters etc ... but how much more applicable can they be ? Can they perform simple integer math operations?)

Could this be done with discreet logic chips? - I was looking at a this EE project http://www.ele.uri.edu/~vijay/ProjectELE447.pdf ... which described all manner of ALU and multiplier chips - could these simply be piped together to express this algorithm efficiently?

How would my needs change if I needed to solve a grid of 4000 x 2000?

Thanks for your time


texts:
My friend and I are trying to design a remote controlled car and one of the aims is for the controller to be a smartphone. The original idea was, have a transmitter plugged into the audio headphone jack which would interpret audio signals sent from a controller app and then send an appropriate signal.

My problem is I don't know what sort of signal is appropriate. All that needs to be controlled is forwards/backwards motion and turning left or right. Ideally it would be able to have speed control - not just forwards and backwards.

My initial idea was using something like this for radio transmission: https://www.sparkfun.com/products/10534, but then it would mean doing analog -> digital and sending digital data with some kind of protocol, so then I thought of sending just the analog data but I'm not sure how that would separate the forward/backward and right/left controls.

I am a beginner in this field and would like some direction - what approach do I take that will allow me to keep the cost low (e.g. no bluetooth modules)?


texts: ATmega162 fuses to select external clock 12Mhz?

texts:
Could anyone tell me how I could change the fuse bit, so that my ATmega162 uses 12 MHz external crystal.

Once, I made the changes in the AVR fuses wrong the AVR went dead.

That is why I need supervision of an expert.

Below is images from Datasheet


texts:
How to test an ignition key switch voltage drop with an Arduino Uno microcontroller?
I want to test thr voltage drop across OFF and ON key positions with an Arduino.
The operating voltage of the ignition key switch is 14VDC and the Arduino operating voltage is 3.3-5VDC. If I connect the ignition key output direct to the Arduino, it will burn.
How can I test this?


texts: Direct connection between two SFP+ cables

texts:
I have been reading a lot about modern fiber networking recently and I have a clarifying semi-hypothetical question:

Imagine I have two 3-foot sections of Multi Mode Fiber, and four SFP+ 10G transceiver modules. I have two servers, each with an SFP+ slot, mounted 5 feet apart. I can't connect them with one of my cables, but if I could use both cables I could pull it off. I could use an optical connector of some kind and that would probably work, but I don't have one of those.

Does such a device exist that would accept my two extra SFP+ modules, and provide a direct connection? Like a switch, but without the switching. It doesn't really need to know anything about Ethernet Frames, so I don't need a MAC layer. If the configuration was possible, I could use two PHY ICs back to back blindly passing data. But do I need PHYs? I read the SFF-8418, and the SFI interface is quite bare bones. I also saw an SFP+ module app note, and it looks like the module isn't much more than a laser and conditioning circuits. the SFP+ does no buffering, etc.

So can I just make a board with two SFP+ slots wired directly together? Both modules would need power. There are those I2C pins, which probably need to be used to turn on the laser. What SFF document has information on that protocol? Do SFP+ modules need a clock signal?

Assuming I can build a board with properly impedance matched traces, how close to impossible is this?

If it is possible, what are boxes like this doing? some kind of signal reconditioning for long hauls?

https://www.perle.com/products/10-gigabit-standalone-media-converters.shtml


texts: Big address space and small physical size?

texts:
The Intel D1000 MCU datasheet says:

The MCU has 4 kB of data flash and 32 kB of code flash. Code flash
occupies the address range 0x2000 0000 to 0x3FFF FFFF and is aliased
throughout. It is accessible from both 128-bit code and 32-bit data
busses. Data flash occupies the address range 0x4000 0000 to 0x5FFF
FFFF and is aliased throughout.

The size of the address space is:

0x2000 0000 ~ 0x3FFF FFFF = 512M Bytes
0x4000 0000 ~ 0x5FFF FFFF = 512M Bytes

But the datasheet says the MCU has only 4kB data flash and 32kB code flash. Why the address space is so big and the physical size is so small? Does it mean that only the first 4kB or 32kB of the big address space can be used?

And what does aliased mean?


texts: Choosing a PCB Manufacturer/Assembler for the first time

texts:
I've just finished designing my first PCB, and I'm about to send out a batch of emails for quotes from manufacturing/assembly shops. My design is super simple: the only components are 7 identical SMD resistors, a 5v voltage regulator, a decoupling capacitor, an ATMEGA328P-PU and 16 pads for off-board wires. I'm looking to do an initial run of 50 boards, with the possibility of ordering more later. I'd also like to receive a prototype to verify that everything works properly before putting in a purchase order for 50 more boards.

I'm very new at this, and Google provides an overwhelming number of shops to choose from. This post seems to have some good advice for ensuring quality, however it seems that such a small, simple board wouldn't fall prey to many quality issues.

Beyond the advice in the above thread, does anybody have any recommendations for what I should ask in the email? And further, if anybody has any suggestions for particular shops to reach out to, I'm all ears. Less expensive is better, but not at the risk of receiving defective boards.

Edit: Also, would you anticipate that it would be dramatically less expensive to just solder the boards myself? And if it's worth it to have the PCBs assembled, is it more or less expensive to let the shop source the parts themselves? I'm not sure if they would get a better deal on the parts, or if they would be overcharging me for them.


texts: Interpreting the power rating of the refrigerator

texts: My refrigerator is rated as 130W of power. I need to know how to interpret this. Does that mean if the compressor works for a whole hour then only it consumes 130W? Or is 130W the average power considering that the compressor will be sleeping for most of the time? The refrigerator is from LG electronics.


texts: Difference between blocking and nonblocking assignment Verilog

texts:
I was reading this page http://www.asic-world.com/verilog/verilog_one_day3.html when I came across the following:

  We normally have to reset flip-flops, thus every time the clock makes the transition from 0 to 1 (posedge), we check if reset is asserted (synchronous reset), then we go on with normal logic. If we look closely we see that in the case of combinational logic we had "=" for assignment, and for the sequential block we had the "<=" operator. Well, "=" is blocking assignment and "<=" is nonblocking assignment. "=" executes code sequentially inside a begin / end, whereas nonblocking "<=" executes in parallel.

I was fairly sure that nonblocking assignments were sequential while blocking assignments were parallel. After all, you can make blocking assignments with assign statements outside of always blocks, and those all run in parallel. Is this a mistake, or is the behavior different inside an always block? And, if the behavior IS different inside an always block, can nonblocking assignments be made outside an always block?


texts: What are the limitations, if any, of free EDA tools with respect to high speed design?

texts:
I've read this excellent post by Some Hardware Guy, and I'm aiming toward something similar to what OP was doing which is a Beagleboard derivative.

I've done some more research and it seems that experienced board designers advise the use of professional tools for Beagleboard-type high speed designs, like Altium or Allegro. Are there any very specific reasons why one could not use a tool like KiCad for high speed designs? Are the free tools missing the required signal integrity simulators, or are they simply too much trouble given the complexity of the job?

I am also a software person. Though it sounds like I'm more experienced with hardware design, I haven't yet done a board this complex. So I'm trying to evaluate if these free tools are useful as long as you really know what you're doing, or if I should not even bother until I can afford a professional tool (and learn it).


texts: Would a current feedback op-amp work well as a precision ground reference?

texts:
I've been looking into precision ground reference circuits to form ±5V rails from a 10V supply for a project I'm working on, and noticed that current feedback (CFB) op-amps have some desirable characteristics (primarily high output current and slew rate). Since I will be using it as a return path for multiple filters and decoupling capacitors, it needs to have a high output current and fast settling time. However, I also need keep the DC level stable across a range of temperatures and under varying loading conditions.

I like the dual-feedback design below that a voltage feedback op-amp, but I also have a few concerns:

The suggested precision op-amp has a low slew rate. This could be problematic since I am expecting (unavoidable) step changes at the output.
With the series resistor, I'm afraid that the op-amp will saturate before it can source or sink sufficient current.

simulate this circuit – Schematic created using CircuitLab

Questions:

Can I safely route the inverting input of a CFB to a distant part of the board (as a Kelvin connection)?
Assuming that I can guarantee stability under capacitive loading conditions, am I likely to run into DC drift issues (possibly due to self-heating)? I don't care about the initial DC offset as long as it is very stable.
After setting the feedback resistor, can I still expect to get a high slew rate?

I'm thinking of doing something like this to generate a ground reference using a CFB op-amp (possibly the LT1206 or LT1217):

simulate this circuit


texts: I want to connect two PCBs with four wires: VCC, GND, 2x I2C. Which connector is best suited for this application? I was thinking about an USB connector (and wire), but I am not sure if that is the best possibility. Therefore I wanted to ask if there are better connector types than USB for this application? VCC is 5V.


texts: What is output amplitude of Direct Digital Sythesizers as AD9850?

texts:
By looking at AD9850 DDS or other similar parts made by Analog Devices Company it is obvious that the output signal amplitude changes by frequency. This can be shown as x= pi* fout / fClock and amplitude changes by Sin[x]/x.
By using this formula we should see an amplitude drop less that 20% between 1Hz to 50 MHz but this is not the case that happens. As I am driving this part, I see the amplitude is around 1 volt pk-pk at 10Hz and 10mV at 50 MHz. Is anything I am missing in these calculations?


texts:
I have this simulation issue and I don't know how to solve it:
The Zener current is smaller than the breakdown current yet the Zener diode still acts like a voltage regulator. Any help?
Shouldn't the voltage be 6.4V?
Is the breakdown current the minimum current after the Zener diode is not in the Zener breakdown region or is it the maximum current before damage?


texts: Is this a parallel circuit or series circuit? The picture shown is a lighting system with 5 leds and 5 resistors.


texts: Why would I need AC coupling if audio inputs already do the job?

texts:
I'm transmitting data from a microcontroller to a smarphone mic input and I was suggested to use this circuit to adapt the 5v digital signal:

Taken from this tutorial
The way I see it R2 and R3 have effect on the filter but their main function is to scale down the signal to aproppiate levels. The circuit is clearly a high-pass filter and I think its only function is to eliminate the DC offset. But why would they do it if the audio input does the AC coupling itself?


texts:
I'm currently doing the practice problems for CMOS VLSI Design 4th Edition. Question 1.6 says to use a combination of CMOS gates to generate the following functions (solution attached below function given from book answers):

$$Y=A (Buffer)$$

$$Y= {\overline{A}B+\overline{B}A}$$

My question is regarding the outputs.

For the first function (buffer) what is the point of using two inverters? Why can't I just draw a buffer? And why does the second inverter need to be active low?

For the second function, same thing, why does the output need to have an active low inverter? why can it just contain an OR gate at the output instead of a NOR and an inverter?

My best guess is that it's used to produce 'strong' outputs. But that explanation doesn't fully help with my understanding.


texts:
I am using LTspice to simulate the AC analysis of a circuit. When I open the netlist of the circuit in LTspice and run the simulation, I get the following error:

An example of the netlist that I'm using is:

I have placed an independent current source between nodes 5 and 1 in the first line of the netlist: I1 5 1 AC 1. I want to know why am I getting this error and how to correct it?


texts: PID: how to deal with delay between controller and a process?

texts:
In designing a digital pll, I'm facing a problema with a communication delay between the loop filter output and the frequency synthesizer (via SPI).
If I dont consider the communication delay the system suffer with a high overshoot, long stabilizing time or no synchonization at all.

Its a classical design: ref_in  --> phase_detector --> PID --> SPI_controler --> frequency_synth --> phase_detector

Any tips would be very appreciated.


texts:
Why does capacitor polarity matter or maybe it   does not? and when it comes to capacitors in a filter circuit, what is the difference for picking one type to another, namely, electrolytic or ceramic.

For instance, the classical multiviberator circuit as shown in the diagram above, there are 2 capacitors: C1 and C2. Why are they polarized? I am sure that ceramic caps works here fine because I have tested it.

Another commonly seen mic amplifier as shown above, C1 sometimes is electrolytic and sometimes ceramic, generally having the value from the range of 0.1 uf to 10 uf. Let's say both are 0.1 uf, is there a difference for using electrolytic than ceramic capacitor for C1? and I am very confused, why does C1 have a range from 0.1 uf to 10 uf? which value should I use for C1?


texts: 7 port powered USB hub backfeeding to my PC

texts:
I just bought two 7 port usb hubs: LogiLink UA0124. Just to run into a strange situation.

I did some servicing to my PC today and disconnected the main power cord from the PSU. Only to find out that all my usb devices(connected to other usb ports on the PC) are still powered up!
At first I thought that I somehow accidentally  managed to make a perpetuum mobile!!!

When my euphoria run out I figured out that the hubs are giving a constant 5 volts to the PC port (backfeeding), even when I turn off the switch on the usb hub!
I also noticed that the processor fan has a small movement like twitching every 5 seconds...

So there must be some weird current running through my motherboard.
What should I do? This does not seem like some no name cheap product. So I wonder why is it designed in this way. Is it OK when the PC is powered up? I mean does the default voltage of the PC usb port counteract with this one and everything is fine? In that case I should only watch out when turning off the PC? Or is this something serious that could damage my other components?

UPDATE

As per request in the comments, I'm adding few pictures here. And many more on this LINK (LogiLink 7 port USB HUB dismantled)


texts: How do the windings in a residential transformer create a neutral and why are the hots opposite phase?

texts: Pretty self-explanatory I think; just wondering why neutral "manifests" from the windings and why it "outputs" (for lack of a better word) a negative-phase hot?  I guess my perplexity comes from thinking that the [+hot/neutralwindings/-hot] are all the same wire so assuming that is correct what causes the changes?


texts:
Excuse me for this simple question.

Can someone tell me how this circuit works?

In the video, it is said that, the voltage drop across the resistor connected to NPN/PNP will be only a diode drop. But I'm not grasping that. Can someone simplify it better?


texts: small wind turbine pancake generator, force of magnets effect on rotation when charging a battery?

texts:
Contexte: a DIY small wind turbine pancake generator, made with 2 rotor plates of 12 rectangular magnets, and one stator of 9 coil wired. After the generator, the 3 alternative electricity phases are transformed into direct current thanks to 3 bridges rectifier (one for each phase). After the rectifier, a LM317 circuit limits the voltage, in order to load battery, or an arduino board, or any else device.

Problem: at low speed of wind, when the generator charges a battery (or load arduino board, etc ...), the load generates a break onto the rotation of the wind turbine. The power of wind is not enough to maintain the rotation speed face to the reverse force generated by the load of the devices.

Question : Every things being equal, does the break phenomenon will be less important if we put magnets with low force (but with same shape) ?

Additional informations:
Currently, I have build a DIY generator for a DIY vertical axis mini-wind-turbine. This generator is made with magnets and coils. The magnets currently used are very strong. The resistivity when it charges a battery is too important when wind is very low. Then, I wander if reducing the strength of magnets, choosing magnets with same surface, same shape of surface, but less strong than those currently used, without changing anything else, will reduce the resistivity ?

Said differently:
For a pancake type generator, what will the effect of a reduce of the magnetism force of magnets (keeping the same magnet surface shape x*y, but decreasing the height h, the thickness) on the reverse electro magnetic force created when this pancake type generator is run by a mini wind turbine and feeds a charge (like a battery).

To better understand the system, I give you this following little sketch. You can see the general system. The type of pancake generator I'm talking about. The effect on rotation per minute when the generator loads a battery and when it does not, for a same low wind speed. And the question about the magnets.

My question is really focused on effect of the change of magnet force, regarding the RPM when appears the reverse electromagnetic force due the load of a device, everything else equal. Will the RPM be less slowed with lower force magnets ?

Whatever the effect on voltage or intensity, the question is really only focused on effect of the change of magnet force.


texts: Measuring maximum output current of Operational Amplifier

texts: I just designed a two stage Miller compensated operational amplifier. I am not sure how to measure its maximum output current. What is the precise definition of this current?


texts: Is EMC shielding of a grounding wire required?

texts:
Consider the following 2 use cases:

Fully electric vehicle with 2 different insulated voltage systems: 1 high voltage @1000V DC insulated from chassis and 24VDC system with minus pole (-) at chassis. Would PE cable (connected to chassis) need to be shielded? If yes, then why?
Single phase house supply system. Would the PE cable need to be shielded? If yes, then why?

In my opinion there is no need for shielding as these cables' sole purpose is to protect the people from indirect contact should any live part came into contact with metal exposed parts (that can be touched by people).

In short, these conductors are not meant to carry any signal/current (if not for brief periods < 1s), I don't see any reason for EM shielding.

Short clarification:

In question 1, the the chassis is ground (as in "return path") only for 24V system while metal parts of chassis of high power loads are connected to the chassis with a PE cable (as in "Protective Earth").

In question 2, consider a TT system, the PE cable is grounded.


texts: ATX power supply max current 12V P8 connector

texts: I'm using a ATX power supply as a unit for my project. The power supply is of the type "be-quiet" straight-power E8 480W with cable management. I cannot figure out how much current can I get from the 12V P8 connector, which has 4 12V poles and 4 ground poles. My need is 20A in total for the 4 couple. I read that this kind of ATX power supply has 4 12V rails, each one can give up to 18A. How are these rails physically placed and distributed among the different connectors?


texts: 9v oscillator circuit that produces a frequency of 500 Hz

texts: I am a gr 10 student that really has no idea what I am doing, however, I have made a circuit schematic and just need to know if it is right I guess.


texts: Throughput and Bit rate seems to have the same meaning and also have same unit of bits per second. Then what is the exact difference between throughput and bit rate?


texts: How can I make my PNP amplifier circuit to turn off faster?

texts:
I'm using the following circuit to switch a 24V signal to a PLC. The rising edge is fast and perfect(38 ns) but the falling edge of the signal is not as good(3.5us)!
How can I modify this circuit to have faster-falling edges?

simulate this circuit – Schematic created using CircuitLab


texts: PCB Layout: Reconciling metric and imperial measurement units

texts:
I am using Eagle CAD to lay out a BGA based PCB, for manufacture at Laen's prototyping service. One of the problems which I am having is that BGA parts are typically specified using metric units (for example the ball pitch is .8 mm), but that several other parts on the board (and actually the specifications for the PCB DRC) are given in Imperial units (for example, the minimum trace width is 6 mils, and the minimum hole size is 13 mils).

How do people reconcile the differing systems? For example, if I route things on a metric grid, connectors which have .1 inch spacing no longer align nicely to the grid. Alternatively, if I use a mil grid, I cannot place a via precisely in between 4 BGA balls.


texts:
This is about the 'TEE' Model in BJT small signal analysis on CB configuration. During the lectures, the one I learn is this model;

But in some books I found a different model with a base resistance.

If I do the calculations for common base configuration without the base resistance, I end up having a short circuit path from Base to ground. Even in examples this base resistance is not small so that we can neglect (Where the model uses a base resistance). Can anyone just say what is the importance in having a base resistance in this Tee model? :)


texts:
I am trying to solve the 2013 paper set by ISRO for electrical engineers. I wanted to verify if my answer to Question no 14 is correct.

The maximum RMS current is 20A, so maximum tolerable RMS voltage will be \$E_{max} = 20 \times Z_o = 20 \times 50 = 10^3\ \text{volts} \$, from this the power we get is also \$ 20 \times 10^3 \ \text{watts}\$.

Also total power transmitted into the load is given to us \$ P_T = (1 - |\Gamma|^2)P_i = 10 \times 10^3 \ \text{watts}\$

So we can find the reflection coefficient \$ \Gamma = \frac{1}{\sqrt{2}}\$ thus

$$ VSWR  = \frac{1+|\Gamma|}{1-|\Gamma|} = 5.828$$

Actually I'm  not getting any answer in the options.

I am not clear if I was right in thinking  that the incident power

$$P_{incident} = \frac{E_{max}^2}{Z_o}$$

An alternative approach,

if I know max current flowing into the load is 20 A,

$$ 20^2Z_L = 10^4 $$

So we can find \$Z_L\$ = 25

$$\Gamma= \frac{Z_L - Z_o}{Z_L + Z_o}= \frac{25-50}{25+50} = -0.33$$

$$ VSWR  = \frac{1+|\Gamma|}{1-|\Gamma|} = (0.5)^{-1} = 2$$

I really was not truly happy with any of my approaches to this problem.


texts: zigbee seies 2 (xbee model ) , zigbee + microcontroller

texts: Does a zigbee series 2 ( xbee ) module have a inbuilt microcontroller? If yes, is it possible to reprogram that microcontroller? If not, then is it possible to use an external  microcontroller.


texts:
I'm studying the subject Electrical Safety in Engineering and a special term really drew my attention. When I tried to google it, no any option was suggested but hull protection.

In the presentation slide, the definition of the term is explained in a such way.

  Hull voltage: voltage that occurs when the insulation between
  accessible contacting parts usually not under voltage and a sufficiently
  distant point on the Earth's surface, is damaged or between such parts
  and other conductive parts with zero potential;

Could anyone explain the exact meaning of the term hull voltage?


texts: Separate FB rectifiers for each phase, outputs in series...bad idea?

texts:
Newbie here. So I have made myself a mini hobby 3 phase wind turbine that rarely outputs enough usable voltage from a 3- phase rectifier.
Didn't find any adequate info on it online but made sense in my head. What if instead of the 3 phase rectifier, I used full bridge rectifiers on each phase separately and connected the outputs in series?(+maybe smooth each one with a capacitor) Would it yeald in higher(granted noisier)voltage,and a less amperage,as the outputs on a three phase rectifier are in parallel?


texts:
I recently bought a DIY 1000W AC motor dimmer meant to be powered off 220-240VAC. I was hoping to use this to control a transformer which in turn powers a heating element.

The heating element needs 60W and i think the resistance is about 5mOhm. My derivation of this is at the bottom.
Rather than try get the windings on the transformer perfect i thought using this dimmer control would give me enough flexibility.

This is the circuit that has been supplied:

simulate this circuit – Schematic created using CircuitLab

I am new to triac and diacs but my first question is more about the 1000W rating on this circuit. With my heating element only needing 60W is it a good idea to change the values for some of the resistors and/or caps? or is this 1000W just an absolute max with no relevance to the magnitude of control i would get with a lower powered load?

Secondly, the terminals were not labelled on the diagram and are not labelled on the PCB either. If somebody could figure out the orientation of the IN and OUT terminals i would greatly appreciate it.

Deriving Resistance of the heating element:

Connected the element in series with a 100 (99.3)Ohm resistor powered by a 4 (3.965)V supply.
Measured the voltage drop over each of them
Over element \$V_e = 0.2mV\$
Over resistor \$V_1 = 3.94V\$
\$ R_e=V_e * R_1/V_1 =5.05 mOhm \$
the 0.2mV drop over the element is very close to the minimal 0.1mV that my DMM is able to measure so i do not know how accurate it is. If anyone knows a better way to test the resistance please let me know.


texts: So here's a picture of a potentiometer from my book. And my book says that the potentiometer is used for measuring internal resistance (of a cell), emf (of a cell) etc. But I cannot understand the concept behind this as how to find the emf of a cell? Also how to find the internal resistance of the cell? Could someone please explain this concept?


texts: How to find the total output resistance for a mosfet cascadinging with a bjt?

texts:
I'm working on an problem in school. The original circuit was much bigger but I replaced the two current mirrors with DC current sources for simplicity. I know \$R_{in}\$ for the mosfet is infinite so the total \$R_{in}\$ for the amplifier is infinite. The mosfet acts as a voltage buffer. But I can't figure out how to get the total \$R_{out}\$ for the circuit.
Info. I already solved for: \$r_{o1}=8\mathrm{kohm}\$, \$g_{m1}=4.4721\mathrm{mA/V}\$, \$g_{m2}=40\mathrm{mA/V}\$, \$r_{p_i}=2.5\mathrm{kohm}\$, \$r_e=23.97\mathrm{kohm}\$.
I've looked all over the internet and can't find any examples of a MOSFET cascaded with a BJT. Every example out there is either two MOSFETs or two BJTs. Please help.


texts:
In a CE circuit what happens when gain, determined by Rc/Re is greater than transistor beta?

i.e. I'm designing an amplifier for 75mhz, I have a 2nF capacitor across Re. I expect the impedance at that frequency to be 15ohm. My Rc is 2.5K , so Rc/Re = 166.

This is greater than beta for this particular transistor,
what actually happens under these conditions?


texts: Do I need SS for SPI single-slave communication?

texts: I'm using Atmega328 as a master in SPI communication with a single slave. Is there a way to avoid using the SS (slave select) pin for SPI? That pin can also be used for PWM output, which I would like to use.


texts: How do you programmatically detect pin count on an MSP430G2553?

texts:
I am using a Launchpad to program an MSP430G2553 controller.  I use it for debugging.  This controller has 20 pins.  However, the end goal here is to run my program on an MSP430G2553IPW28R controller.  This controller has 28 pins instead of 20.

I'm using pins P3.0 and P3.1 on the 28 Pin Controller for some LEDs.  And my launchpad controller doesn't have those pins.  I need to determine which controller the code is running on.

I will be using my launchpad's JTAG pins to program the 28 pin controller.  So, the question is, how can I programmatically determine which of the 2 controllers my code is running on, and put some kind of #define in place to use pins P3.0, P3.1 when running on the 28 pin controller and pins P2.1 and P2.2 when running on the launchpad controller.  I don't want to have comment and uncomment lines of code each time I switch from one processor to the other...

Please note, I'm using Energia as my development environment.


texts: Design an emitter-follower amplifier with bjt

texts:
I'm studying the emitter-follower configuration for bjt on the book "Practical Electronics for Inventors". On pag 439 there is an example related to the design of this system. In this problem it knows the parameters Rload, Vcc, hfe and f3db, and the target is to find the other parameters:

choose the value of Ic = 1mA;
Find the resistance Re = (0.5*Vcc)/Ic;
Find the ratio of R1/R2 such that Ve = Vb-0.6V;

Than it says that R1//R2 <= 0.1 Rin(base),dc because this prevents the voltage divider's output from lowering under loading conditions. I don't understand this statement.

My first question is: why R1 and R2 are in parallel? If you apply the simplified model (I show after) to find the quiescent operating point R2//Rin not R1//R2.
Am I wrong? Con you explain the meaning of this statement?

Thanks

Equivalent model

simulate this circuit – Schematic created using CircuitLab


texts:
I recently broke my USB port on ESP 32 ...

... so I need somehow program it. I have this FTDI programmer. ...

I tried to flash it (I pushed boot and EN button together and when Arduino IDE finished compilation and started flashing, I released EN and then boot button.)

Connection:

ESP 32 VIN ... VCC programmer (3.3 V)

ESP 32 GND ... GND programmer

ESP 32 TX  ... RX  programmer

ESP 32 RX  ... TX  programmer

After this attempt I get this error:

I tried to use this programmer to program Arduino nano and it works.
Do you have any sugesstions about programming this ESP 32 without USB port?


texts: What is the current limit of driving a linear actuator for 4 VDC at 12 VDC?

texts:
Please bear with me, if this is a stupid question.

I obtained a linear actuator of a family of linear actuators, here are the specs

| Bipolar linear actuator | 04     | 12       |
|-------------------------|--------|----------|
| Operating voltage       | 4 VDC  | 12 VDC   |
| Current / phase         | 0.2 A  | 0.07 A   |
| Resistance/ phase       | 20 Ohm | 180 Ohm  |
| Power consumption       | 1.6 W  | 1.6 W    |

I own the 04 model that is rated for 4 VDC and which is a bipolar linear actuator.

The first question for me is: When I am configuring a stepper motor voltage, the total current, that the 04 version of the actuator uses, would be
$$0.2 A \cdot 2\space phases = 0.4 A $$
is this correct?

The fact that $$ 4V \cdot 0.2A \cdot 2 = 1.6W$$ also somehow supports my understanding :D

Now to the real question: When I use a stepper driver whose voltage would be 12VDC, what does it actually mean to the 4 VDC version of the actuator itself?

Higher voltage might saturate the coils quicker, as far as I understand, but the effect is probably not that big as the actuator for 4 VDC was designed to saturate the coils already in the most efficient way, increasing voltage also might just increase power consumption and little other effects?

When I apply 12 VDC to the actuator, I would have to limit the total current to the specs of the 12 VDC version, then or still go with the 4 VDC?

Would it be $$ 0.07 A \cdot 2 = 0.14A$$

or am I wrong and would have actually to drive it with the current / phase for the 4 VDC which would be 0.4 A? Which however would mean that the power consumption increases from 1.6 W to
$$ 12 V \cdot 0.4 A = 4.8 W $$

affecting the resistance per phase also, increasing it from 20 Ohm to
$$ \dfrac{12 V}{0.2 A} = 60 \Omega $$

So for what current should I adjust the stepper to use the 4 VDC actuator with 12 VDC (if at all).

Insights appreciated :)


texts:
I want to use a MOT (microwave oven transformer) for something it's not intended for. As a consequence, I need to limit the current so it doesn't melt itself. I am planning on connecting the ballast to the primary. The load on the secondary should be capacitive. I understand that a resistive ballast will limit current because V=I•R, so if V is constant, I will be relatively constant.

How does a reactive ballast limit current? Can I use a capacitor instead of the usual inductor? If I use both (in series) to correct the power factor, will that counteract the ballasting? Will connecting two MOTs, primaries in parallel, secondaries in series, change much?


texts: Which everyday components involve flows of charge that are not electrons?

texts:
I like this explanation of why there's nothing wrong with conventional current being the opposite direction from electron current.  It mentions batteries and fluorescent bulbs as two cases where the current is not a flow of electrons.  (As well as ion flow in human beings and proton flow in water ice, though those are not electrical components.)  What other electrical components involve flows of charge that are not electrons?  Does this happen in the electrolyte of electrolytic capacitors?

  From the topic electron theory we know that metals emit electrons easily and semi-conductors and electrolytes emit them with great difficulty. The electrons in the electrolyte are in fact not free but are bound in ions. http://www.electronics-tutorials.com/basics/polarization-capacitor.htm

Do holes in semiconductors really count, since they're not physical particles?


texts: I have some breadboard wires as below photo, how can I take away the jumper out of the wire, I've tried to push the the slit on the jumper with no luck!


texts:
I am looking to control a proportional valve with a PWM signal that will correlate into exact current amounts (for example a 25% duty cycle will output 200mA, and a 90% duty cycle will produce let's say 1A).

What kind of hardware will this require?

Can I use an LED Driver (they seem to be current control outputs)?

I have seen and read about dc-dc converters being used, but I am not sure I understand how they achieve constant current source.


texts:
I was recently taking a look at a failed power supply for 12V halogen lighting and noticed an unusual texture in the potting compound. I tried chipping some of it away with a screwdriver and got a nice surprise:

Yes, pebbles. But why? Are they special pebbles or just normal ones?


texts:
I found a movie
 about controlling motor speed.

It is a motor from a Vitamix Blender, controlled with a potentiometer.

What kind of motor they are using for these blenders?


texts: Will I be able to modulate a 1mW laser using a 555 timer LED circuit by replacing the LED with the laser diode?


texts: smallest device to switch off power for a battery powered project

texts: I have a servo motor (tower pro sg90 analog) that I am powering with a 9v battery. I want to attach the smallest switch possible somewhere between the battery and the servo to be able to manually turn the power on and off (or potentially interrupt power with an attached gyro or accelerometer). I know I could buy a battery holder with a switch, but is there another electronics component I could buy to wire in somehow, without the holder? I have no background in EE, so I don't know the appropriate search terms to find this.


texts:
This project is from Arduino's Examples page. The first fritz is from there. I managed to run that example without any issues. However, I had tried keeping the wires together so I tried to run the project with a breadboard but have had no success. What is wrong with the second fritz?

1.

2.


texts: What are the selection parameters for an NPN BJT?

texts:
I'm building an NPN-based driver circuit for disconnecting my battery level measuring voltage divider when not in use. Here's the circuit:

  http://www.microbuilder.eu/Tutorials/Fundamentals/MeasuringBatteryVoltage.aspx

I've gotten fairly familiar with selection parameters for mosfets (gate-source voltages and whatnot), but what parameters should I be looking for when picking Q2? Digikey, as always, has about 100 results for BC817

As a small part 2, what is the purpose of R4 in this circuit? I know for MOSFETs, this is done to manage gate capacitance, is it the same idea here?


texts: What to do to make the clock in the microwave always correct?

texts:
My new microwave has the same problem, after setting the correct time, after a week there is already 40 minutes forward.
I even thought to install my RTC in it, but the manufacturer should somehow manage it by himself to make the hour work properly.
I don't understand why every one of my microwaves, including my friends, always has the same problem.


texts: Powering nichrome wire with 18650 battery pack?

texts:
I am doing a school project to build a portable electric cooktop (like if someone's camping) I plan to have a 5s6p 18650 battery pack of 2000mah cells heating about 2m of 20ga nichrome wire. I calculated that my battery can provide 150 amps for an hour (15000mah charged) and at 25.2 volts, and I will be using a BMS of the correct specification. According to https://www.easycalculation.com/engineering/electrical/nichrome-wire-calculator.php, 2m of nichrome wire would require 17.5a of current and 34 volts.
My questions are:

What challenges would you see with building this prototype?
Would I be overdischarging the battery pack?
The calculator also says it requires 662 watts of power. Is this cause for concern?
I know that a circuit will only draw how much power it needs. If the nichrome wire can heat up to 2100 deg. Fahrenheit, will it pull that power and overdischarge the battery pack?
Is there a way to control current flow to control the temperature of the wire?

Thanks!


texts: can i use a single voltage regulator to power two usb ports

texts: So I was wondering if its possible to use a single voltage regulator (with one input and one output) to power two usb ports? Or would I need two voltage regulators to this. The voltage regulator takes in 12V and outputs 1.5A at 5v.Both my usb ports require .5A @ 5V. I will be using TI ptn78060w. This is my first electronics projects and im still trying to get the hang of all this. Any help is greatly appreciates or any book recommendation to help me understand power would be great.


texts:
I have a Prime Instruments model 60-579 watt meter for a gas generator. It has a scale of 0 to 3750 watts and is marked 125 volts. So its for a 30 amp circuit. I have searched extensively for the current transformer to use with this meter but no one seems to know. Does anyone know which CT is needed or how to calculate which one would be needed. FWIW, I measured .2 to .4 ohms across the meter terminals. Thanks
Here is a picture inside the meter. The wire is less than 14 gauge.
https://www.dropbox.com/s/z72437v21uvgnxh/PrimerMeter%20Turns.jpg?dl=0
The wire in the turns around the disk is less than 14 gauge. I am concerned about running 30 amps thru the meter.


texts: Do ordinary transformers need flyback protection?

texts:
Low voltage 12V relays driven by a microcontroller plus transistor need a flyback diode to suppress an inductive voltage spike when they are switched off.
Do ordinary power transformers (say, at a distribution substation) need some sort of similar flyback protection in case a large fraction of their load is suddenly shed (e.g. a tree fells powerlines and a breaker opens, etc.)? I would imagine that a resulting voltage surge for those who remain connected to the grid would be very undesirable. What about lower current transformers in "power" household applications?
In practice is there a good way to estimate the magnitude of the spike (besides empirical testing)?


texts: Decoupling capacitors on I2C interface + ESD protection

texts:
I had one of my PCB designs reviewed by someone and the reviewer suggested that I add decoupling capacitors on the clock and data lines of I2C interface.

I am a bit surprised as I have always seen decoupling capacitors placed next to power supply pins. Is this a common practice? I looked around in different reference schematics and I haven't come across a design where they used decoupling capacitors on the clock and data pins. Is this necessary?

I am using a PCA9548 I2C multiplexer. The chip comes with ESD protection. Is it necessary that I add external TVS diodes for ESD protection?


texts:
I understand the algebra, and I can also use Kirchoff's Law in calculation.

But I struggle to understand how it makes sense logically.

The law states, that the sum of the currents entering a junction must also be the same sum for the currents leaving that junction.

Now, this would make sense in a circuit without resistors, but if I am to apply resistors, the current would be slowed, and therefore, the amount of coulombs passing through per second (amps) would be lowered, and the current on the other side would surely be lower, than before the resistor?

How does this make sense with Kirchhoff's current law?


texts:
I want detect a 220 VAC AC signal using an AVR.
I could convert 220 VAC to 5 VDC with an opto-coupler.
How can I detect the exact time of the signal?
What about blinking signal per half second?


texts: Troubleshooting SC2262/2272 RF module interaction Arduino

texts:
I'm having difficulties reading any input from my RF module to my Arduino. I hope I have done all the necessary simple tests prior to asking for help here on whether or not the receiver is faulty.

There was a forum post over at Arduino with a similar problem, but unfortunately, no solution found.

Kit:

SC2262 transmitter and SC2272 receiver 433.92 MHz with keyfob TX, cheap off eBay.
Arduino UNO R3
Prototyped with standard breadboard and jumper wires. D0-VT to Arduino pins 2-6 respectively.

As suggested in the other forum post, I have used a meter to measure the voltage across GND to each digital PIN and see no flicker of life with each button press. This is the M4 sub-type which I understand as momentary, however, the meter is flat 0V which I don't believe would be expected.

There is demonstrable 5V on receiver module power pins.

Using an RTL-SDR dongle also demonstrates transmission peak on button press so I don't believe the fault lies at the transmitter end. New A23 battery in keyfob.

I haven't included any code here, as I don't think this is where the fault lies. I can demonstrate correct digital reads in Serial Monitor when artificially replicating signal with 5V.

In addition, I believe that there are encoder/decoder chips onboard this module. I did try adding a library from GitHub (QuentinCG's) but it made no difference.

This leads me to believe the receiver may have a fault. However given my lack of experience, it could equally be oversight of something simple.

If you want me to put up my code, or photos of the breadboard please let me know.

Address pin photos


texts: Why do baseband processors remain on, and communicating with the tower, when the phone is shut down?

texts:
I've believed this since 1994 - that if you really want to turn off a cell phone, you need to take the battery out.
But why? What is a good technical reason to keep spending battery charge and occupying tower bandwidth despite the user having shut down?
Please, if you could refer to sources, alongside your provided reasons, I would love it very much!
Clarifications: I am aware of locking your screen, which (depending on your settings) can make the screen turn off. My question is clearly about shut down.
Not locking screen, not screen locking itself after a minute due to inactivity... I am talking about pressing the power button and choosing "shut down" (Nokia) or "Power Off" (Android)
It's very hard to find discussion about this topic because of millions of people raising all sorts of power issues on their phones but I really don't know of anyone who doesn't believe the baseband processor remains on even when you shutdown the device, including experts in the field.
For example, here's a guy who appears to know a thing or two about Android phones (look at the most popular answer to the question):
https://android.stackexchange.com/questions/215736/what-is-the-fastest-way-to-shutdown-unrooted-android-phone
Another example: https://www.zdnet.com/article/fbi-taps-cell-phone-mic-as-eavesdropping-tool/
"Some handsets can't be fully powered down without removing the battery"
...Again, I know these aren't design documents by Qualcomm but people seem to be adamant that it's a thing!
Would be lovely if they cited their sources :D


texts: connecting oscillators in parallel to increase current

texts: I am trying to power an alternating current coil, and was wondering if I can connect the output from transistor oscillators in parallel to increase the current, like you can with batteries. I don't need to increase voltage, just current.


texts: Charging internal laptop battery bypassing board

texts:
I own a refurbished tecrq z50a and during a routine clean up i did a mistake of taking off the bottom cover without realizing that it was still shutting down. A screw rolled on the board and sparks happened.
Notebook works using battery but battery wont charge, port is working and the local laptop shop has given up stating they cant get the current up to the correct voltage.
Is it possible for me to hijack the red\black wire from the battery pack and directly supply the correct voltage (maybe i would need to create some sort of step down from the laptop adaptor) so it will charge the battery while running the laptop or can i just replace the wires that is supposed to go to th battery with fixed wires. Its a shame if i have to throw this fairly good notebook away..
Any hints of a logical solution is appreciated,  as I am a programmer not a technician but I can learn the basics, thanks!


texts:
I have a question regarding the calculation of the junction temperature of MOSFETs and IGBTs.
An estimation is possible with:
$$T_j = P \times R_{th} + T_a$$
Let us assume that the thermal resistance (from junction to ambient) is 0.2 and the ambient temperature is 50°C.
Now, when I want to calculate the power losses I need to know the junction temperature due to $$E_{sw}\left(I,R_g,T_j,V \right)$$
I always thought that need to use the ambient temperature for loss calculations and then to calculate the junction temperature but it seems I do not understand this correctly.
Can someone explain to me how I can calculate the power loss of power semiconductors without knowing the junction temperature?


texts: Finding the waveform of current in a circuit

texts:
How do you find the waveform of current i1(t) in the following?

Do I need to find the capacitive and inductive reactance then find the current i1(t)?


texts: Are there any length limits to series termination ? If I have a trace that's 12 in or a trace that is 100 in, can the same series termination resistor be used (assuming that Zo = 50 ohm) ?


texts: RGB LED Arcade Button rewiring for the AIY Google Voice Bonnet

texts:
I'd like to rewire an arcade-type RGB button so the button action is
replaced by a simple external push button and the LED function is either
maintained as is or replaced by a single LED.  My button comes with the AIY
Google Voice Bonnet and is attached with 6 pins to an 8 pin harness
as illustrated in the schematic at
https://aiyprojects.withgoogle.com/voice/#makers-guide--button-connector-pinout.  Eventually, my aim is to
replace the new button by a  dialer microswitch as in Alasdair Allen's
retro telephone project,
https://medium.com/@aallan/a-retro-rotary-phone-powered-by-aiy-projects-and-the-raspberry-pi-e516b3ff1528.  (Note: I have V2 of the
Voice Kit while Alasdair had V1, which has a simpler (4 pin) button.)
At first I thought I could simply remove the leads from the button connected
by the harness to the BTN and 5V pins and insert a push button as a prototype.
This did not work.  My second attempt simply connected the push button,
220 Ohm resistor and an LED to the GND and 5V pins.  This produced the
expected effect of lighting up the led when the button was pushed, but
didn't communicate with Voice Bonnet as intended by the python code below.
If I want the LED to mimic the RGB LED in the button I need connections
to the BTN and one of the RGB pins, but how?

#!/usr/bin/env python3
from aiy.board import Board, Led

def main():
    print('LED is ON while button is pressed (Ctrl-C for exit).')
    with Board() as board:
        while True:
            board.button.wait_for_press()
            print('ON')
            board.led.state = Led.ON
            board.button.wait_for_release()
            print('OFF')
            board.led.state = Led.OFF

if __name__ == '__main__':
    main()

I'm obviously a total novice at this sort of thing.
An inquiry to the Google AIY team yielded the
advice that I should use the extension pins of the Voice Bonnet
rather than the existing button pins, but I'd prefer to reserve
these for the on/off-the-hook switch of the phone.  Any advice
would be much appreciated.


texts: Microstrip High- and Low-Impedance Short-Line Sections

texts:
Expression 4.50 can be obtained by equating the ABCD parameters of the
  two circuits ?

How to derive expression 4.50 using the ABCD matrix for transmission line and π-circuit network ?

Note: Screenshots below are taken from Microstrip Filters for RF Microwave Applications, 2nd Edition


texts: Distributing Ground and Clock Between ADC and FPGA on Separate PCBs

texts:
This question is in reference to my previous question where some suggestions were made that went somewhat off-topic.

Basically I have a built a system with an FPGA and very sensitive ADC (sensitive to picoamp currents) which is working well, but now it has to be separated into two PCBs.

Major questions are

How to properly share GND between the two boards in order to minimize ADC noise/error at all costs?
How to properly buffer the CLK and serial signals in and out of the ADC?

My proposed solution:

Concerns I'm having:

I know the ribbon should have GND in between each signal (since some are 40MHz) but should GND be connected to both planes on either side?
It was suggested to buffer the ADC I/O so that the ADC doesn't have to drive a lot of current, but where do the buffers get their power and ground from?
Here I have signals traveling over the edges of ground planes, which I've heard defeats the purpose of having a ground plane.
Since the PCBs are already getting a GND connection at the power supply, doesn't also having GND in the ribbon create a loop?


texts: What is the name of this connector and how can I find an adapter?

texts:
I have the following connector (see image below) with contains 5 metallic pins (4 pins are used for a 4-probe IV measurement + 1 ground). Its diameter is 6.65 mm.
What is the name of this connector?

I would like to connect it to a Keithley 2400 series, possibly using the 4 different triax connectors.
Do you know of any adapter I should use?
Thank you
EDIT:
This cable is for a 4 pin probing system with ground. We use it to test microelectronic devices. It is basically the connection to 4 metallic pins.
On the one side, the cable looks different, as it has a different head connector:


texts: Is it really that the electrical energy consumed by a resistor totally transform to heat energy?

texts:
My notes say that electrical energy and power consumed by a resistor is totally transformed to heat energy.

Is this true?

Or could it be transformed into also some other kind of energy?


texts: I am currently having an voltage output that differs with time and is about 35 V at maximum. I am looking for a solution to decrease the voltage to 3.3 V without  changing the signal. I am looking into using a voltage buffer and a voltage divider, but the op amps I found has a maximum voltage of 32 V. Is there another way to decreasing the voltage without affecting the signal?


texts: I need some help manipulating a transfer function to a specific form

texts:
I am taking an electrical engineering course at college and am tasked with designing a specific filter for our final design lab. The general form of the transfer function that this filter must satisfy is known.

In order to satisfy the conditions outlined by this lab, the transfer function of the filter must take the following form:
$$\frac{T_2T_4}{T_1T_3}\cdot\frac{(1+j\omega(T_1))(1+j\omega(T_3))}{(1+j\omega(T_2))(1+j\omega(T_4))}$$
with (T_i) are terms which are equivalent to any combination of other variables.

Now onto my task. The transfer function for this type of filter starts out in the form
$$\frac{R_1}{R_1+Z}$$
In this circuit, $Z$ can be defined as
$$\frac1Z=j\omega(C_1)+\frac1{1/R_2+j\omega(C_2)}+\frac1{R_3}$$
and if I've done my algebra correct this should simplify to
$$Z=\frac{R_3+j\omega(R_2R_3C_2)}{1+jw(R_2C_2+R_3C1+R_3C_2)-\omega^2(R_2R_3C_1C_2)}$$
But feel free to check my math there.
So finally, for the question I pose to all of you, I need help getting
$$\frac{R_1}{R_1+\frac{R_3+j\omega(R_2R_3C_2)}{1+j\omega(R_2C_2+R_3C_1+R_3C_2)-\omega^2(R_2R_3C_1C_2)}}$$
to look like the first expression above. At the end of the day, the ultimate objective is to obtain a set of equations where if I had values for all (T_i) and R1 I could solve for the R2,R3,C1,C2 required to obtain the behavior described by the selected values for the (T_i) terms. This means that something like
$$T_2+T_4=R_2C_1C_2$$
is valid as long as the other equations help solve for at least one term, which I can substitute into others to solve for the rest of the terms.

I've given my best at trying to manipulate this thing to suit my needs, but I've hit a wall. I'm not sure if I did something wrong, or if I simply am not seeing how to proceed, and thus I am looking for second opinions. I managed to get to
$$\frac{1+j\omega(R_2C_2+R_3C_1+R_3C_2)-\omega^2(R_2R_3C_1C_2)}{R_3/R_1+1+j\omega(R_2C_2+R_3C_1+R_3C_2+\frac{R_2R_3C_2}{R_1})-\omega^2(R_2R_3C_1C_2)}$$
Maybe you guys can work past this.  Thank you so much for sticking with me and for any help you can provide.  I'm not sure if this will help any, but the form of the transfer function I am trying to match can also take the form
$$\frac{T_2T_4}{T_1T_3}\cdot\frac{1+j\omega(T_1 + T_3)-\omega^2((T_1)(T_3))}{1+j\omega(T_2 + T_4)-\omega^2((T_2)(T_4))}$$
by simply multiplying the terms out in the numerator and denominator.  This may be more useful as I don't need equations for each (T_i) individually per se, though that would make everything all the easier, since I already have values for what (T_i) will all be. As I said, I just need enough equations to where I can isolate at least one of the 4 variables I'm solving for, then use simple substitution to solve the system.


texts:
Background: automotive application, '79 oldtimer with a Cylinder Head Temperature (CHT) sensor (a 2-wire NTC thermistor) that is fed into an analogue electronic control unit (ECU). The sensor output is only visible to the ECU and used for fuel injection management. Also, I don't have visibility of the ECU circuit that conditions the thermistor signal (the ECU has 3 proprietary hybrid ICs with no datasheet available).

Some more notes:

One end of the thermistor is grounded, the other feeds into the ECU.
I've got +12 V and enough current available for additional circuitry, though.

I would like to monitor and display the engine temperature with a vintage analogue gauge. The obvious option is to install a second CHT sensor. Yet mounting an additional sensor on the engine case is non-trivial, and given that there is already a sensor, why not reuse its output?

I'm looking for a circuit that would allow me to tap into or split the thermistor output so that I can read the resulting additional output with the gauge. I would worry about matching the sensor output to the gauge later, but is this something that could be achieved without upsetting the ECU temperature reading?

Update: just for the background's sake, while the ECU schematics are not available, there is  circuit diagram of the next generation of that particular ECU online:

In that picture, I've marked the engine temperature sensing thermistor in red. The schematics, without being exact are probably close enough to get an idea of the circuitry behind the sensor that I'd like to tap into.

The BS10, BS20 and BS30 are the more modern DIP versions of the proprietary hybrid ICs in my ECU, while the rest of ICs are LM2902 quad op-amps.


texts:
I'm using a PCM5102A DAC in a project and I've noticed that when the IC goes to sleep (>1 second without data on the I2S bus) there is some errant switching noise audible via the amp.

If I connect the R/L channels to analog ground, everything sounds great. My question is:

How can I automatically ground the R/L channels when there is nothing coming from the analog output of the DAC?

A monostable has been suggested to me, but I feel like that might be too complex of a solution for this.


texts: So I wish to wire a project that uses three 12 V fans but I don't know if I should get a power supply with 12 V or 36 V.


texts: Powering a buck/boost converter, how much amps can I get?

texts:
I have a 12V/3.2A switching PSU powering an LTC3780 buck/boost converter rated at max 2-30V/0-10A.

Let's assume 100% efficiency, can the LTC3780 achieve more than 3.2A if set for example at 5V? I guess it is a general electronic question. Do we have to 1) think in watts here or 2) assume the amps out can't be higher than the amps in?

If we have to think in watts, would it mean that...

PSU: 12 * 3.2 = 38.4 Watts

LTC3780 @ 5V: 38.4 / 5 = 7.68 A

The LTC3780 would be able to push 7.68 amps @ 5 volts? (again, let's assume 100% efficiency)

Thank you!


texts: BLDC motor and drive power loss calculation for dynamic application

texts:
what I have done so far:
calculated torque and speed of the motor (robot arm swinging mass)
used equivalent circuit for DC motor as model for BLDC:
U_terminal=L* di/dt +(I_o+ I_load)* R_ph-ph +k_emf *n
can be rearranged as:
U_terminal=(L/k_t)* dT/dt +(R_ph-ph/k_t) *T_load +I_o *R_ph-ph +k_emf *n
efficiency=P_out/P_el=T *2 *pi *n/(U_terminal *I) with U_terminal from above, I=Io +T_load/k_t
Looks like motor loosing efficiency because of intertial torque as a component of T_load and also cause of the inductivity L.
Now I want to proceed as stated here: Motor Calculations for Coreless Brush DC Motors
Calculate P_loss from efficiency, use thermal equivalent circuit, calculate new heated R_ph-ph, recalculate power losses and new coil temperature iteratively...
Question1: Why does the torque constant have to be recalculated (scroll almost far bottom of the link)? Where does the given formula K_t_warm=k_t *(1+ magnet_temp_coeff *temp_difference) come from and why is it so similar to the heated resistor formula? Do you need to do this for brushless dc motor aswell?
Question2: Is there any BLDC with a given efficiency map out there? I would love to calculate the efficiency and compare it to some real experimental data (and share it with you ofc), but could not find anything on google myself
Now the harder part: drive losses
Im fairly new to electronics and dont know where to start. It seems like there are Mosfets and IGBT, also trapezoidal control for BLDC and sinusoidal for PMSM. I have seen some power loss calculation in the manual for a drive made by texas instruments, but it was hard to follow because the terms are new to me. Now I could start researching, but I fear that im gonna spend 5 hours on it and later find out, that the calculation does not fit for BLDCs.
So the question3 is: Do you know of a good tutorial/ manual to follow for the power loss calculation of a BLDC drive?


texts: Why does my clock signal have a step half way between high and low?

texts:
I'm trying to debug a clock signal between two ICs (DS90CR287 and DS90CR288). There is a step half way up the single ended clock generated by the DS90CR288 which I don't know how to explain. I can't post the schematic but there is a 30Ohm series resistor between the output clock (DS90CR288) and input clock (DS90CR287).

EDIT

I meant to say between two DS90CR287 ICs and a DS90CR288. It seems like the cause of the step is using series termination rather than parallel termination.


texts: ARM Linux and UBoot - Can I make a read-only MTD writable?

texts:
I have several embedded Linux devices installed at customer sites.  We have an updated Linux kernel we are prepared to deploy to these devices.  The problem is that on these devices, the U-Boot arguments are specified such that:

bootargs = {....} mtdparts=atmel_nand:16M(kernel)ro,240M(rootfs)

So, I can't flash_erase to nandwrite the kernel or U-Boot over SSH because MTD0 is read-only.  I can't tweak the U-Boot args without serial access.  For many of the customers, taking all the devices down and serially hooking them up and interrupting U-Boot to get to the bootargs would be extremely cumbersome.  Is there any way to change MTD0 from ro to rw from the kernel once it's loaded?


texts:
Is there a list of standard ID codes used for components on a schematic drawing that anyone can point to?

e.g.

K = Contactor
S = Switch
Y = Solenoid
X = Terminal strip

etc.

Any list would be good, although if there is anything relating to Australian Standards that would be great.


texts: How can there even be an input voltage on a long-tailed pair?

texts:
Assuming the following:

The voltage across the base-emitter junction of a BJT is constant in forward-active and saturation mode
The BJTs in a long-tailed pair are normally forward-active or saturated

(If any of these assumptions are incorrect, read not further and correct me)

then how is the difference between Vin+ and Vin- not fixed to the difference between the base-emitter voltage drops of the two transistors? (Zero, if the transistors are identical)


texts: Three Phase AC Induction Motor - Locked Rotor and Phase Drop Questions

texts:
A few questions about three phase AC induction motors. All questions relate to a Wye connected motor, running off 120V rms (phase-neutral), each phase 120° apart. This is a pure and simple three phase motor; there is no starting circuit, overload protection, extra circuitry, etc.

If I know the phase resistances, input voltage, and how the motor is wired (wye), is this enough to calculate locked rotor current? Everything I've found relates NEMA ratings to locked current ranges but I have a custom designed motor and need to calculate locked rotor current from the info I have.
If I start a 3 phase motor with 1 phase (i.e. with power off, open the contacts to Phase B and C, leave Phase A closed, then apply power), what would the current on that phase be when voltage is applied? Would it just be the 120V divided by the phase-neutral resistance since the rotor would not rotate?
If I started the motor with all 3 phases (normal operation), then dropped to just Phase A (as in question 2), would the rotor continue to rotate (assuming my power supply has no current limit)? What current draw is to be expected here (relative to steps 1 and/or 2, assuming there is a way to calculate/approximate it)?


texts:
I've recently talked with a friend about LaTeX compilation. LaTeX can use only one core to compile. So for the speed of LaTeX compiliation, the clock speed of the CPU is most important (see Tips for choosing hardware for best LaTeX compile performance)

Out of curiosity, I've looked for CPUs with the highest clock speeds. I think it was Intel Xeon X5698 with 4.4 GHz (source) which had the highest clock speed.

But this question is not about CPUs that get sold. I would like to know how fast it can get if you don't care about the price.

So one question is: Is there a physical limit to CPU speed? How high is it?

And the other question is: What is the highest CPU speed reached so far?

I've always thought that CPU speed was limited because cooling (so heat) gets so difficult. But my friend doubts that this is the reason (when you don't have to use traditional / cheap cooling systems, e.g. in a scientific experiment).

In [2] I've read that transmission delays cause another limitation in CPU speed. However, they don't mention how fast it can get.

What I've found

[1] Scientists Find Fundamental Maximum Limit for Processor Speeds: Seems to be only about quantuum computers, but this question is about "traditional" CPUs.
[2] Why are there limits on CPU speed?

About me

I am a computer science student. I know something about the CPU, but not too much. And even less about the physics that might be important for this question. So please keep that in mind for your answers, if it's possible.