texts: How to protect a battery terminal after removing corrosion?

texts:
I have repaired a corroded battery terminal by neutralizing it in vinegar and then cleaning it with a wire brush. The result is a terminal lead which now has bare steel visible where the protective chrome layer has been destroyed.

What kind of treatment can be done to this surface to protect it from oxidation now that the steel is exposed? Even if it doesn't corrode again in the future from a battery, I believe oxidation of the steel can still lead to further damage to the surface and it's electrical conductivity.

I am interested in both inexpensive solutions such as an aerosol spray as well as other more expensive options for an electronics hobbyist that relate to this type of repair.


texts: MAX485 suddenly drawing too much current and output voltage levels are not right

texts:
I have two PCB that I designed and they are made by a PCB manufacturer (so they are identical). They use a MAX485CSA to communicate but suddenly one of them is drawing too much current, on a normal operation the circuit draws around 5mA and now It's drawing 73mA from my bench power supply (I get the reading from the power supply display). I know that the culprit is the 485 transceiver because if I disable the sender pin and enable the receiver (both pins are tied together as you can see in the schematic so this is how it works) the current drops again to normal levels (5mA), I've also noticed:

When transmitting: channel A is 2.84V when high state while in B channel is 4.54V when high state. In the healthy PCB, both are around 4.5-5V when high state.
When not transmitting: channel A is 2.84V (when it should be 4.5-5V) and channel B is 0V as it should be.
If the circuit is connected to the power supply powered ON with its output OFF A and B are connected to the receiver (in this case the receiver is an Arduino using a MAX485CPA, same setup as the sender circuit), the receiver gets an endless train of garbage (random 0s and 255s), this doesn't happen with the healthy sender.
If the circuit is connected to the power supply powered OFF or is not connected to the power supply at all I don't get any garbage.
Things that solved the garbage problem under any circumstance: joining the circuit's common ground with the power supply's ground (Earth), joining both sender and receiver GNDs, adding pull-up and pull-down resistors to channels A, B at the receiver's end.

Note that even with the voltage levels being wrong I can get the data right if I turn on the circuit before the receiver (so the receiver's buffer won't get filled with garbage)
I'm pretty sure that if I replace the MAX485 on the sender the problem will be gone but I'd like to know what's going on and how can I protect the transceiver to prevent this from happening again before I send the circuit to repair.

I attach below the part of the schematic that shows how the transceiver is connected if you wonder about termination and pull-up pull-down resistors:
I'm sending data through a very short distance, like 5-10 meters and low bitrate (9600bps) so I've not added termination resistors, plus a termination resistor would draw additional current.
I have played around a lot with 485 transceivers in very messy setups like breadboards and such and I've never needed pull-up/pull-down resistors so that's why I have not added them to the design.

EDIT1:
I'm going to keep common ground as Jeroen suggested but there's still something bothering me. I've been checking the receiver's side controlled by the Arduino and I noticed a transient in the non-inverting channel when the Arduino's    USB is plugged-in (being USB the only PS), it stays at 4V for like 3 seconds, then it drops to 288mV. The signal also goes up and down some millivolts as I plug-unplug other USB devices and the monitor. This 4V to 288mV transient is causing current spikes in the sender's end of the same magnitude as I'm experiencing now continuously in the defective circuit ¿someone knows what does this mean?

EDIT2:
The 485 transceiver was damaged after all, It has been replaced and the problem with the excessive current is gone and voltage levels in the output are right this time. I'm also not getting garbage from the powered off circuit,with or without common ground.

Reasons for this to happen remain unkwnon even though there are some potential culprits:

Not keeping common-mode within spec due to the lack of common ground as Jeroen pointed out.
Max485 transceiver failure after frequent transients from the receiver's end when connecting/disconnecting the USB cable which caused current spikes on the circuit.

For now I'll be performing tests on the circuit using common ground and see how it performs. I'm also powering the Arduino from the power jack so I won't get those ominous transients each time I plug in the USB cable.


texts:
So, playing around with my first attempt at a circuit using an OpAmp, I am now simply in despair with these 741. Apparently they are "outdated" as any post even related to them is first replied to with a comment along the lines saying as much.
And while I have some LM324 at hand, the project I want only needs a simple comparator so wasting 4 OpAmps on it is not really something I want to do if I can avoid it.
That said, while most posts I read said the 741 is "obsolete", in my project, it seems completely non-functional. The basic circuit works with the LM324 so I don't even know what I'm doing wrong?!
I'm connecting Vcc+ to 5V and Vcc- to GND. Connecting In+ to Vcc+ and In- to Vcc-, I get some 4.8V on the output, which seems fine. With In+ on Vcc- and In- on Vcc+ I get 1.8V which is a bit much compared to the Vcc- I was expecting but I can make it work.
The real problem comes when I try to use it as a comparator as the output voltage never even budges away from the 4.8V. Even when the difference between In+ and In- stands at -0.8V. I also tried using a 10k potentiometer on the Offset Null inputs as the datasheet suggested to no avail.
Again, I understand that they are outdated but how can it be that they just don't work at all? I mean, there has to be something I'm doing wrong, no?


texts:
Can current flow through a relay's NO channel when it's not energized?

I'm an electronics newbie and I built a circuit where a relay is operated by a Raspberry Pi Zero W. See circuit image. The relay used is a SRU-06VDC-SD-C. It's rated for 6v but I hear it click open and closed using the 5vdc from the Pi.

I would use this to turn my heating on and off at home, the circuit that switches heating on and off is a 110V DC line coming from my heating installation (my AC voltage is 220V). When this circuit is closed, the heating is turned on. This line is wired to the NO contact.

It worked fine for weeks when testing but when actually wired up to the heating it worked for about a week but now the heating is always on, even when I explicitely do not energize the relay. The heating is even turned on when the pi is switched off. When I measure with a multimeter, the meter claims the circuit is not closed. Could someone tell me what I'm doing wrong please?

Thanks in advance!

(updated after advice from Transistor)


texts: Design an 8x4 memory chip using 2x1 memory chips?

texts: I have been given this task to design a single 8x4 memory chip using only 2x1 memory chips. I have been searching everywhere on google for some decent information or example of how this is done, but sadly came up empty handed. Can anyone please help me out or at least point me in the right direction?


texts: How is time of supplied real time clock module maintained without battery?

texts:
I am thinking about purchasing this RTC ( real time clock ) module.

Since this particular item comes supplied without a battery, I wonder how the time is being kept running in the chip since it's manufactured and until a battery is plugged in the socket ?

EDIT :

After checking the plenty of nice answers that this question has received, I believe I didn't form my question well.

Real time clock is supposed to give you information about year ( counting leap years ), month, day of the week, time ( hours, minutes, seconds ). So if the module arrives without battery installed, what time will it show ? And how can you set the correct time on the chip ?


texts: Would output signal affect input signal when the opamp is saturating?

texts:
I have learned that opamp would be saturating when the output signal is too large.

My question is would the saturating output affect input signal, for example, change the amplitude of the input signal, cause input distortion or anything else? Thank you!


texts: How does this op amp circuit with adjustable gain work?

texts:
Please see the attached circuit.

I'm trying to show \$-n\lt A_v \lt n\$.

I worked half part successfully:

When \$V_{+}=0\$, the op amp output works to put \$0\text{ V}\$ at \$V_{-}\$. KCL gives:
\$\dfrac{v_{\text{in}}-0}{R} = \dfrac{0-v_{\text{out}}}{nR} \Rightarrow \dfrac{v_{\text{out}}}{v_{\text{in}}} = -n\$

However I'm not able to get the correct answer when \$V_{+} = v_{\text{in}}\$.

Here is my failed attempt:

When \$V_{+} = v_{\text{in}}\$ the op amp output works to put \$v_{\text{in}}\$ at \$V_{-}\$. KCL gives:
\$\dfrac{v_{\text{in}}-v_{\text{in}}}{R} = \dfrac{v_{\text{in}}-v_{\text{out}}}{nR} \Rightarrow \dfrac{v_{\text{out}}}{v_{\text{in}}} = \color{red}{+1}\$.

But the correct answer is \$\color{red}{+n}\$.

Any help?


texts: Using CMOS logic ICs to drive a P-channel FET

texts:
I am attempting to implement a latching circuit without software. The results thus far seem promising, but now I want to drive a control line on a solid-state relay using its output as a high-side PNP switch. I opted to use some CMOS logic ICs to simplify the construction of the circuit, so I want to feed one of the IC's output to the gate of a PFET. These CMOS ICs have limited current output, so I thought to try a simple voltage divider to both A.) keep the current output low, and B.) keep Vg negative with respect tp Vs.

Does this design practice seem feasible? If not, what are some recommendations?

ICs:
CD4043B cmos r/s latch
CD4081B cmos and gate

EDIT: Schematic should read "Vg < Vs" or in this case basically 6V<12V

EDIT 2:

Truth tables for the CD4043/4044
Proposed pfet inverter


texts:
This signal is from an instrumentation amplifier,
read from Arduino MEGA2560 ADC,
loop delay 10ms (rate 100Hz)
I need to count high spikes only, (in below figure, 6 high spikes can be observed)
Edited -
its and ECG signal and signal was sampled at a rate of 100Hz


texts: Measuring power consumption of cache memories?

texts:
Is there any practical method to only measure the power consumption of combined cache memory. I am intereted in measuring the power conumption overhead when replacing blocks, and or filling the cache after start-up. Also of interest is extending this to the power consumption of the whole cache/bus/memory system.

If there is no practicl way, are there any simulator or power calculators which does so. Thanks


texts:
Is this possible to have perfect components in LTspice? No parasitic inductance, no parasitic capacitor, no resistor, etc? Is it not possible is it possible to make a model and model it with no parastic parameters?

I would like to have a perfect diode, perfect MOSFET, IGBT etc. Should I use another software for doing something like this?

If I not able to understand some phenomenoms with perfect components I won't be able to understand it with parasatic components.


texts:
I have a pushbutton setup and occasionally it is randomly triggered without someone pressing it. Would this be because I have a larger resistor on the 3.3V GPIO (reads the input and possibly susceptible to being a noisy GPIO pin)?

simulate this circuit – Schematic created using CircuitLab


texts:
I've selected a potential latching relay for use in a project (switching mains power), but - having been away from electronics for a while - I'm still trying to wrap my head around a couple things.  Here's the relay in question:

http://www.digikey.com/product-detail/en/te-connectivity-potter-brumfield-relays/7-1393239-7/PB2014-ND/4925213

1) It says it's rated to 3V.  Will 3.3v (my microcontroller (ESP8266) voltage) hurt it?

2) There's no way my microcontorller can source (or sink) enough power to drive this.  It needs a 30ms pulse (minimum) at 3V with 21Ω of resistance.  If it was NOT a latching relay, I could simply set up a transistor and call it a day - however, I'm not sure how to configure it for this.  I know that I'll have to hook up two IO, and drive one HIGH and one LOW (A to HIGH, B to LOW or B to HIGH, A to LOW) for the duration of the pulse in order to switch the "latch" of the relay.  Seeing as the IO pins themselves can't source or sink enough power, how do I configure transistors to turn HIGH or LOW depending on the IO?  Goodness, I feel like I'm missing something super obvious.

3) Does anybody spot any immediate problems with my idea to use this to switch a mains power line?

Thanks!


texts: What's the difference between 0 and high impedance (or floating)?

texts:
I was introduced to this state of high impedance (that is, not 0 and not 1) in a wire.

I don't understand the difference between 0 and high Z, I see that these are both absence of energy in the wire.

For example, if I'm at one side of the wire and in the other side there is a signal, how can I tell the difference between 0 and Z?


texts: Constructing a D type flip-flop from JK type flip-flops

texts: How can I construct a D type flip-flop from JK type flip-flops?


texts:
A 24.0-mH inductor, with internal resistance of 24.0 Ohms, is connected to a 110-V rms source. If the average power dissipated in the circuit is 50.0 W, what is the frequency?

So I tried using XL=2πfL and XR=R.

First I used P=I2R-->50W=(I2)(24)-->I=1.4434A then I used Ohms laws V=IR-->110V=(1.4434)((2π)f(0.016H+24ohms)) and solved for f. But this doesnt seem like the answer.

Any ideas on how to solve the question?


texts:
Right, first the diagram, I tried using the schematic function,but it never actually added the schematic.

I picked this because it illustrates my confusion in the simplest schematic I could find.

We've got three nodes here, with the bottom (N3) being the ground node, current directions are provided for N1, so writing up KCL for the nodes give the following.

$$N1 :2mA - \frac{V1}{3000}\ -\frac{V1-V2}{6000}\ = 0$$ (current enters from the 2mA supply, leaves trough the rest of the legs)

$$N2 : \frac{V1-V2}{6000} - 4mA - \frac{V2}{12000} = 0$$ (current enters from the 6k resistor, leaves trough the rest of the legs)

This in turn gives out the correct node voltages for V1 and V2. (\$\frac{-12}{7}\$ for V1 and \$\frac{-120}{7}\$ for V2)

However, I am supposed to be able to arbitrarily define the direction of the current over the 12k ohm resistor, so if I decide that current flows into node 2 and instead and use the following N2 equation

$$N2 : \frac{V1-V2}{6000}\ - 4mA + \frac{V2}{12000}\ = 0$$

I get the wrong result for both V1 and V2, so clearly the direction of the current across the 12k ohm resistor matters, what am I doing wrong ?


texts: Is it possible to combine multiple step up inverters in parallel?

texts:
So my goal was to start the car off double layer capacitors, but the issue is, as any of the energy is used, the voltage drops according to the quantity of energy used. When only 20-30 percent of the total energy is used, the voltage already drops so low that the ecm\pcm starts turning on and off, turning off the starter relay.

I saw "DC-DC Step-up Power Inverter Module 10V-32V to 12V-35V". However it's only for 10 amps, and no one makes 100 amp dc-dc adjustable step up inverters. I was wondering if you could put 10 or more of them in parallel.

I was told there are issues balancing the load or something and that's why it can't be done? Can someone explain why this can't be done?


texts: What is this schematic symbol? Transistor ? Variable Inductor

texts:
I was looking through an old schematic and found two symbols that I didn't recognize:

Is this a PNP transistor? looking up the model number doesn't give much information.

Is this some kind of variable resistor or variable inductor?


texts: Current to Voltage Gain using Network Analyzer

texts:
Suppose I have an Voltage to Current Amplifier. And I'm characterizing it over a frequency range, can a Network Analyzer directly measure current to voltage gain (Iout/Vin)? (Or) do I have to use a resistor to create a Voltage drop to get the gain usual Vout/Vin gain?

Thank you!


texts: How to decide CPOL and CPHA values in SPI configuration

texts:
I am working on a slave device for which I have to write a Master configuration.
In the datasheet of the slave, it is mentioned, "The SDO data changes on the falling edge of the SCLK signals. The devices sample the SDI data on the rising edge of SCLK"
Can you please tell me the values of CPOL and CPHA for this slave.
Thank you


texts: ~40 uA current sink... what current mirror topology to use?

texts:
I need to sink a constant 20-60 microamps from the inverting input terminal of an op-amp in order to shift the output voltage upwards a bit. This is a pretty low-speed circuit, with little spectral power above 2 MHz. The feedback resistor I'm using is 2000 ohms so this would translate the output upwards by 40-120 mV. The exact voltage translation I need is dependent on some measurements I have yet to make, but I am sure it will be in this range. I also am somewhat unwilling to change the op-amp circuit impedance.

I believe a current mirror is the right technique to sink this 20-60 uA current, but I'm unsure what topology would be best for my specific application. I am hoping for better than 5% accuracy of the output current.

Here is the circuit I have, with the current mirror currently set up as a Widlar source. The op-amp on top is the one which needs the current sink. In this circuit, In- and In+ are amplified away from each other with a gain of 3. It's like the two input op-amps of a three amp instrumentation amplifier. The two outputs are then sent to a comparator. I'm trying to pull just a bit of current from the inverting input node of the top op amp to shift the In- output upwards. I don't wanna use just a resistor to do it... it would screw up the common-mode rejection of the whole thing. In- is supposed to be in the range of 2.0-2.5V, and I don't need great common-mode rejection but I'm loathe to screw the CMRR up like that by hanging a resistor off there, no matter how small a sink current I'm trying to achieve.

All the resistors in this op-amp circuit are 1% tolerance (since they're cheap), but I'm trying to avoid using matched NPN transistors (since they're expensive and sorta outmoded). Therefore I figure the poor matching of the transistors in the current mirror will be the single largest contributor to error in the output current. I figured I'd use a dual (non-matched) 2N3904-type.

What current mirror topology should I use to achieve this 5% accuracy? 20 microamps sounds small, so I thought the Widlar current source might be appropriate, but Widlar's circuit obviously precludes using the dual emitter degeneration resistors which I would want to include to compensate for any differences in the gain of the non-matched transistors.

So which should I try and why?

If I do the Widlar source, with only a single emitter degeneration resistor, is this likely to yield 5% accuracy with non-matched 2N3904s?
Should I try the ordinary current mirror, with equal emitter degeneration resistors on each NPN, and then a larger collector resistor to synthesize the 20 uA current? This is a 5V circuit, so the collector resistor would be on the order of 250 kohms. I could decrease the overall circuit impedance, but it's already somewhat low.
Or should I try some hybrid approach where there are dual emitter degeneration resistors but of different values? Can anyone refer me to some material about this case?


texts:
I am using SENT protocol in my project.

In my SENT implementation, the data nibbles are 3. So 12 bit data, including a status nibble and CRC nibble.

I need to calculate the CRC for 3 data nibbles.

The seed value for CRC calculation is 5 and the polynomial is

  \$ x^{4} + x^{3} + x^2 + 1 \$

I have done the following for CRC calculation:

char CheckSum, i;
char CrcLookup[16] = {0, 13, 7, 10, 14, 3, 9, 4, 1, 12, 6, 11, 15, 2, 8, 5};
CheckSum= 5; // initialize checksum with seed "0101"
for (i=0; i<3; i++) {
CheckSum = CheckSum ^ Data[i];
CheckSum = CrcLookup[CheckSum];
}

In SENT analyser, I could see CRC error. The log is as follows

Can anyone tell me how to calculate the CRC for SENT protocol.

Note: I have 0XABC as data nibble and 3 is status nibble.


texts: 11-16V DC voltage stabilization for 13.8V powered ham radio

texts:
I am looking for any resources on how to construct a relatively high power (25A, 13.8V) voltage stabilizer (or voltage booster if you like) for my 13.8V powered ham radio.

The problem I try to resolve is powering the radio from both only batteries, and from car battery. So I would like to be protected against both voltage drop especially in first scenario and voltage spikes in the second one.

There is still a plenty of charge in a AGM 12 battery when the voltage is around 12,.4 volts but the radio PSU cuts off when the voltage drops that low.

I know that there are ready to buy solutions, but they are not very accessible in my part of the world, and I would like to at least know the principle they operate on :)

Many thanks in advance!

UPDATE:

What about LM2587 in flyback regulation mode in parallel? Is it possible? I have only found a description of boost converter mode parallel application.

UPDATE2:

Great application note from National about SEPIC design: http://www.national.com/an/AN/AN-1484.pdf


texts: Which mosfets can be used for level shifting

texts:
I would like to build a 5v circuit that uses an sd card and a 3.3v SPI screen and for the level shifting I would like to use the common mosfet circuit, but all versions I have seen use a BSS138 which comes just in surface mount format.

Are there other alternatives to this mosfet that come in through hole format? like TO-92 format?

I was thinking of using a BS-170, is it ok for my use?

Note: The SPI clock will be 8 MHz

The circuit I'll be using (Source sparkfun's level shifting tutorial)


texts: How can I power a load from two separate circuit breakers?

texts:
On one circuit breaker I have a manual switch. On the second circuit breaker I have a motion sensing switch (using a mechanical relay). I have a number of lights wired in parallel as the load. The lights should turn on as a result of motion or manually turning them on. Unfortunately I can't just wire the two switches in parallel on the same breaker because of physical constraints; I'd have to perform a major renovation to rewire.

It seems I need a sort of DPDT relay like this, which is normally open, has two magnetic coils, and keeps both circuits separate:

simulate this circuit – Schematic created using CircuitLab

Does a relay like this exist? Is this the correct way to solve this problem?


texts: How do you measure soil moisture using a capacitive sensor?

texts:
There are a number of capacitive moisture sensor designs on the internet, which use the insulated copper pads on a PCB.For example:

http://zerocharactersleft.blogspot.in/2011/11/pcb-as-capacitive-soil-moisture-sensor.html

In case the above link breaks, here is a photo of a PCB I made using the above design:

Just wondering how these work, and how they can be used with a microcontroller to calculate moisture content? I have seen methods that use a square wave, an RC network, and an ADC to do this, but I haven't seen a clear explanation of how it works.


texts:
I'm studying this circuit:

The author of my book says that the purpose of this circuit, called "Self Biased Current Reference", is to generate a current almost independently of the supply voltage. He also says that, if M3 and M4 are perfectly equal, than I1=Iref. Then it follows that:

from which I can find VGS1 and I1.

Question 1: When the author says that the current mirror is perfectly matched and then I1=Iref, isn't it too much simplified? He neglects channel lenght modulation, but in reality the source-to-drain voltages of M3 and M4 will not be equal (because we have just M1 under M3, instead we have M2 and a resistor under M4)

Question 2: Why is this current almost independent of VDD? The author says:

"The value of the generated current weakly depends on the supply voltage
because there is a high impedance element per branch capable of absorbing
possible supply variations. These two elements are the transistors M2 and M3.
The drain to source voltage of M1 and M4 can not change freely: the former is
two VGS above ground the latter is one VGS below VDD. Any supply fluctuation
is then “absorbed” by the high resistance that we have between drain and
source of M2 and M3"

I don't understand the strong part of the text: why is any fluctuation “absorbed” by the high resistance that we have between drain and source of M2 and M3?

Thank you


texts: If we put 2 diodes in parallel with each other forward biased and the forward voltage of 1 diode is 0.7 V and the forward voltage of the 2nd diode is 1.4V then since they are in parallel the voltage drop must be equal (due to KCL) however they have different forward voltages meaning different voltage drops(?). How is that possible?


texts: Bypassing the circuit board of string lights

texts:
I have a USB powered LED curtain which is attached to a smart plug so I can set it to come on at certain times etc. The trouble is there are multiple "modes" (flashing, alternating etc.) which i'm not interested in but it won't stay set to always on and I have no use for the other modes.
My plan is to bypass the circuit board containing the chip, IR receiver, mode button etc by soldering the lights directly to a new USB connector so the lights are just constantly on when the smart plug is on.
The trouble i'm having is determining some of the values necessary to work out what resistor I would need to use. I have a ton of different resistors and a multimeter and I have done some reading on working out values for LEDs but none seem to refer to these really thin string light curtain type things which is where the confusion comes in.
Here are the values I have from the product specs:

I'm happy to experiment a little but since i'm basically a newbie i'm wary that I don't want to blow the lights or create any potential fire hazards.
Is someone able to quickly run me through what I need to measure/work out in order to determine the resistance needed please? I haven't done anything other than remove the circuit board cover so i'm able to take measurements while they are plugged in if that's any help.
Thanks in advance!


texts: Multiple resistors to reach needed value?

texts:
Im converting an old floodlight to a cree led to run off my solar setup for a yard light

I need a 27ohm resistor for a 3.5v 350ma single led to run off 12.5v, but don't have any that value, what multiple resistors to reach that goal can I use instead?


texts: Help with a simple debounce program on STM32

texts:
I'm trying to write a simple debounce program on an STM32F4. Code as follows:
Initialization:
  RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN | RCC_AHB1ENR_GPIOCEN;
  RCC->APB1ENR |= RCC_APB1ENR_TIM2EN;

  //Configure PB7 as output and PC13 as input pull-down
  GPIOB->MODER |= GPIO_MODER_MODER7_0;
  GPIOC->PUPDR |= GPIO_PUPDR_PUPDR13_1;

  //Configure Timer 2 for 20ms delay
  TIM2->PSC = 95;
  TIM2->ARR = 19999;
  TIM2->CR1 |= TIM_CR1_URS;
  TIM2->DIER |= TIM_DIER_UIE;
  TIM2->EGR |= TIM_EGR_UG;

  NVIC_EnableIRQ(TIM2_IRQn);

Main:
 while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
      if (GPIOC->IDR & GPIO_IDR_ID13)
          TIM2->CR1 |= TIM_CR1_CEN;            //Enable Timer 2
  }

IRQ Handler:
void TIM2_IRQHandler(void)
{
    TIM2->SR &= ~TIM_SR_UIF;                   // Reset Update Interrupt Flag on Timer 2 Status Register
    if (GPIOC->IDR & GPIO_IDR_ID13)
    {
        GPIOB->ODR ^= GPIO_ODR_OD7;            // Toggle PB7
        TIM2->CR1 &= ~TIM_CR1_CEN;             // Disable Timer 2
    }
}

I'm using a delay of 20ms on Timer 2 and toggling the LED on PB7. The LED does toggle, but it doesn't behave like a debounced switch and flickers as the LED turns on. Where am I going wrong?


texts:
I am making a pulley system (for an electric bike) that requires about 300rpm and 40lb-inch torque. The motor that I am looking at is a 24V DC Permanent Magnet Electric Motor Generator 250W 2750RPM from amazon (35$). (There is a geared version available, but it's 80$ more expensive). My question is:
If the motor is near full power and is under load, would the torque increase?
For example, if it's under a load, such that the RPM is 300, does it impact the torque?


texts:
The atmega16 data sheet says that it has 16KB on-chip flash program memory, but the memory map for flash memory ranges from 0x0000 to 0x1FFF(8192, i.e, 8KB) only, which gives a range of only 8KB flash memory. Also the program counter is only 13 bits wide, which can access only 8KB of memory.

In my understanding the address space should have been 0x0000 to 0x3FFF, which would address the whole 16KB of flash, and the program counter should have been 14 bits to access the whole 16KB flash memory. I am confused with this clash between the total flash memory and the memory map of flash memory.

Where am I going wrong? Please help. Thanks in advance.


texts: What's best method to synchronize with main AC voltage?

texts:
I'm making an active rectifier, to make it work I need precise information about actual phase of main voltage.

What I need:

1) exact moment when the positive section of sine wave starts and ends. Basically ac sine -> binary.

2) solution should provide galvanic separation

My ideas so far:

1) small transformer, diode and comparator/logic gate,

If there's a diode on lower trafo side I'm losing precision, as there is drop voltage on it, so I will need to compensate it one way or another. Comparator/logic gate's purpose is to convert half-sine wave into binary.

2) diode/transoptor on upper side of trafo

Higher precision, as diode is on higher side of transformer, but not sure if it will be enough.

3) transformer to step down voltage to let's say 2.5/-2.5V, add 2,5V DC to make it 0-5V and do the math magic in uC

Not sure about it, if anything goes wrong I'd applying negative voltage to uC. Not feeling good about it. But still it sounds as the most precise solution.

What's your method? Do you know any chips that'd do the job?


texts: UART (serial Communication) with IR remote

texts:
I'm trying to send and receive data between 2 Arduino Using UART. I'm have sent and received the data correctly, but in Second Arduino does not active LEDs, maybe the problem in Serial.read(), it's read-only the first byte, but I want to read HEX from Serial Monitor.

This my like for anyone need to help me.
enter link description here
Code for Arduino 1 (Sender):
#include <IRremote.h>
int RECV_PIN = 11;
IRrecv irrecv(RECV_PIN);
decode_results results;

void setup()
{
   Serial.begin(9600);
  //Serial.println("Enabling IRin");
  irrecv.enableIRIn();
  //Serial.println("Enabled IRin");

}

void loop()

{

     if (irrecv.decode(&results))
  {
       long int value = results.value;
    Serial.println(value,HEX); // you can comment this line if serial monitor is not needed
    irrecv.resume(); // receive the next value
    }

    //Write the serial data
    delay(500);

}

Code for Arduino 2 (Recever):
int redLed = 2;

String data;
void setup()
{
  Serial.begin(9600);
  pinMode(redLed, OUTPUT);

}

void loop()
{
 if (Serial.available())
    {
   String data = Serial.readStringUntil('\n');
   Serial.println(data);

      if( data == "0XFD30CF"){
        digitalWrite(redLed, HIGH);
      }
      delay(500);
       digitalWrite(redLed,LOW);
      //Print data on Serial Monitor
 }
}

Note :
This my schematic , but I want to replace PUSH-BUTTON With IR Remote


texts:
I have 5 PCBs which are exactly the same. On those PCBs I'm using a STM32F407ZGT6 ARM Cortex-M4.
But I have a problem with my LSE clock. The Oscillator (ABS07-32.768KHZ-T CRYSTAL 32.768KHZ 12.5PF SMD) does not oscillate on 3 of my PCBs but works fine on 2 of them...

On one of them I have a voltage of about 700mv on NetC21_1 and 280mv on NetC22_1 and on the 2 others I have nothing.

Any idea why my oscillators don't work ? I can't seem to figure it out... Thanks !

Here's the schematic I'm using :

And here's the implementation :


texts: I have a 5 volt converter but I also need 3.3 volts, what should I do?

texts:
Goal is to get 5V and 3.3 V output by the use of a buck/boost converter. Important is to use a converter instead of an LDO for heat reasons.
I want to draw minimum above 0.8A, preferably 1-1.2A at the 5V and potentially around 0.4-0.6A at the 3.3. My input will be aything above 7.4V and below 18V.
I want to add a buck converter to a circuit to reduce the voltage to 5V and then to 3.3V. I came accross this buck/boost converter (TPS63060DSCR) which provides enough current and has a suitable Vin range for my application. Here is the schematic according to the datasheet which outputs 5V with the implicitly calculated resistors for any given Vin.

and here's the datasheet: tps63060 datasheet
EDIT: i realised I made a mistake in my circuit design. Here is the updated version:

At the place of the cut, I also realised I could just use an LDO that converts the 5V to 3.3V since this is not a big step down so it will probably not overheat if i pick a powerful enough regulator, in addition to the fact that it will probably also not draw so much current.


texts: Is a SSR designed for AC power fundamentally different from one for DC power

texts:
A solid state relay can switch between high and low resistance with no moving parts. The control signal is a small (~10V) DC voltage. By this logic, I assumed that a SSR can switch either AC or DC power interchangeably. I bought a PID temperature controller with SSR outputs (https://www.omega.com/en-us/control-monitoring/controllers/pid-controllers/cnpt-series/p/CN8DPT-225) and found that this doesn't seem to be the case.
Are SSRs designed to control AC power fundamentally different from those designed for DC power? I know that PID control of AC power requires zero-crossing detection and other complicated things. This doesn't seem like it ought to prevent a SSR from switching DC power.


texts: Debugging a garage door opener circuit with an optocoupler and mosfet

texts:
There seem to be many related questions, but I can't quite find the answer I'm looking for.  I've got a garage door opener switch.  There's 16V across the wires, and when you short them, the garage door opens.  I used my multimeter to short the wires in ammeter mode, and it read about 20mA.

I tried hooking the wires from the garage door directly to the transistor of the 4N25 optocoupler, and when that didn't work, I tried using the circuit from this answer: How to drive a MOSFET with an optocoupler?.  The result is in the schematic below. JP1 goes to the two wires coming from the opener, and the XBEE is a small radio and microcontroller that runs on 3.3v.  You can ignore JP2, that's a different sensor and it's working fine.

I tested the circuit with an LED, hooking up a 9V battery, and LED, and an appropriate resistor to the other side of JP1.  It works (with either just the 4n25 or the circuit below with the MOSFET).  How do I go about debugging the circuit, or is there something obvious I'm doing wrong?


texts: Can I replace a fused UK plug with a regular plug?

texts:
I hope this question is appropriate.
I bought a dremel rotary tool from Amazon and got a UK plug with a fuse.
Now I want to replace the plug to one that will fit the outlet in my country.
We don't have fuses on our plugs, of course.
Should there be a problem, or will it be a problem only in the UK?


texts: Adjustable 9v - 15v 1.5A DC Switching Power Supply from 6 D batteries

texts:
I am starting a project that needs a way to adjust a 9v supply to anywhere from 9v - 15v at 1.5A. The power is coming from 6 D cell batteries so the voltage will drop as the batteries wear down.

Does anyone have any schematics, pointers, or suggestions where I can look? I have browsed around Linear's website and found a couple chips that might work but don't have enough experience to be certain. I have built a couple switching supplies in the past, but I always followed a schematics in the datasheet.

After some browsing, this is the regulator I picked out. Will it work? http://www.linear.com/product/LT1377

Bonus: I also need to power a 3.3v micro-controller off the same set of batteries. If the circuit could also supply 3.3v that would reduce the overall number of components.


texts: How to assign the same value to a bus in Xilinx ISE (Schematic)?

texts: How to set all the bits for example in bus(7:0) to the value in net0?


texts: How to determine equivalent circuit of inductor

texts:
I'm wondering what is the best model for a real inductor.
I used RLC parallel circuit to explain inductor, however the simulation result  is not well fitting to experiment data.
I'm wondering how to plot the best equivalent circuit of an real inductor
For example, Coilcaraft's SPICE model looks better than RLC parallel circuit, however I can't find any paper which introduce this kind of model. Does the scheme has a reasonable physical meaning?


texts: What is Input Impedance Mismatching of differential Operational Amplifier?

texts:
I am new to design differential op-amp.
I am not sure if my circuit will experience input impedance mismatching.
Can anyone explain how input impedance mismatching will happen in differential op-amp? How should I solve it?
Here is my circuit of differential op-amp:


texts: Is excess noise in a resistor only present with DC?

texts:
Resistor excess noise is present when DC current flows in a discontinuous material, for example through carbon granules in a carbon composition resistor. My question is: Why there is no excess noise when an AC current flows through a resistor?
Quoting (Motchenbatcher/Fitchen):

"Excess noise power is proportional to 1/f, and excess noise voltage
is proportional to the level of DC flowing through a resistor." p. 172

it continues:

"The noise index is the rms value of uV of noise in the resistor per V
of DC drop across the resistor in a decade of frequency." p. 173

And on page 19:

"... Thus, even though the noise is caused by current flow, it can be expressed in terms of the direct voltage drop rather than resistance
or current".

Also, from this old document from Texas Instruments by P.D. Smith :Noise in Precision Film Resistors, on page 3 section 3 it says

"The RMS value of current noise is proportional to the d-c voltage
across the resistor".

As you can see, there is a lot of emphasis on being DC rather than AC what is causing excess noise.


texts: Where can i see what is the thermal dissipation of a 5630 or 1W power led?

texts:
I looked a lot of datasheet from different distributors but i can't fint any information about thermal output.
Datasheets: http://greyghost.mooo.com/usb3led/BL-LS5730A.PDF
http://www.yujiintl.com/files/high-cri-led-datasheets/BX5730L-YUJI.pdf


texts: Explanation of Lq, Ld and how it relates to motor inductance

texts:
I'm pretty much a novice to motor controls, but I was wondering if any of you could explain the concept of d-axis and q-axis inductance and how it relates to the inductance L that is usually specified in motor data sheets.
Also, is the phase to phase inductance the same as the inductance at maximum current?
Thank you!


texts: From the basic principle to the actual dc generator, where are the 'coil loops'?

texts:
I've studied the basic principle of the dc generator which is with the single loop example.

Right here it's the example for the motor but the generator works the other way around. I'm aware of how it works anyway.

My problem is I fail to see the loops in the following diagrams and the actual generators.From the pictures I've seen I only see coils going from a slot to the commutators.
The image on the right is the actual image and the one on the left is used for ease.

Let's take coil A for example. It goes from slot 1 to the commutator and from commutator to slot 3. So is coil A actually 2 coils? Where is the loop of coil A? I've been searching for quite some time but I can't find an explanation. Is the coil going behind the picture and coming of slot 3 to make a loop? Maybe I don't understand how the coils are placed.

Again, my problem is the transition from the basic example to the actual generator. You can clearly see here coils wrapped around and not loops. Is each one connected to the wrapped coil across?


texts: Why Data Recovery Block needs to operate at 16 times the baud rate

texts: The data is received on the RXx/DTx pin and drives the data recovery block. The data recovery block is actually a high-speed shifter operating at 16 times the baud rate, whereas the serial Receive Shift Register (RSR) operates at the bit rate.


texts: Control electromagnet with PWM. Any risks?

texts:
I have to control one electromagnet (like this one, see the image above) with PWM from a micro controller (like the teensy board).

In the label there are only those information:

12V
400N

If I've got it right I need an external power supply with 12V and a MOSFET (like IRL or IRF or similar).

I'm not an expert and I've never used electromagnets but 400N seems quite a lot to me. Which are the possible risks? Is there a risk to damage the micro controller board? or the electromagnets? Are there any other kind of risks to take in account with electromagnets?

EDIT: I'm using the electromagnets to play with ferrofluid and obtain stunning images, like the ones in this video. You can find a lot more if you google it.

THIS QUESTION IS NOT ABOUT WHY TO USE ELECTROMAGNETS, IS JUST ABOUT IF THERE ARE ANY RISK TO DAMAGE THE MICROCONTROLLER, THE SOLENOID OR THE HUMAN AROUND.


texts: How to get second derivative of state as a output of state-space model?

texts:
Let's say modeling the free-falling object on state-space.
Obviously, the equation of motion is a second order differential equation of the vertical position of the object.
And one would normally set vertical position "x" and its derivative "x dot" as element of state to configure a state-space model.
However, the output is only a linear combination of states(and input).
In this case what would be the best option to get "acceleration" or second derivative "x double dot" as an output?
This is quite a basic question, but can't find a good example.
Edit)
Consider a falling ball with vertical force F and positional sensor y. How can I represent an additional acceleration sensor "y_2" on the model below?
$$\begin{matrix} \dot{x} \\ \ddot{x} \end{matrix} = \begin{matrix} 0 & 1 \\ 0 & 0 \end{matrix} *\begin{matrix} x \\ \dot{x} \end{matrix} + \begin{matrix} 0 & 0 \\ 1/m & -1 \end{matrix}*\begin{matrix} F \\ g\end{matrix}$$
$$\begin{matrix} y \end{matrix} = \begin{matrix} 1& 0 \end{matrix}*\begin{matrix} x \\\dot{x} \end{matrix} + 0 *\begin{matrix} F \\ g\end{matrix}$$


texts: Can I supply a BLDC motor controller with pulses? Or does it necessarily have to be DC?

texts: I'm using a 48v 1500w BLDC motor. Can I run the motor controller using pulses obtained from an ultracapacitor? I talked to a person who said that you can't as he tried it and he blew up his motor controller.  Something along the lines of the motor controller using pwm to run the motor and if we supply it with pulses it'll induce oscillations and make the system unstable.


texts:
When is it inappropriate to use a totem pole driver while designing a circuit?

Ie. Never use totem pole drivers when...
        or
    Totem pole drivers are never used for...


texts: What value should be used for an LED with current rating of 350mA ~ 1000mA

texts:
I looking to make a basic LED circuit using a CREE LED from eBay. My only problem is calculating what value resistor that I need. If it is really neccesary, I could purchase an LED driver, but before doing so I would just like to know what value resistor I need to operate the LED.

I know how to work out the value for the resistor, my problem is that I do not know what the current I should use to calculate it is. The current of the LED is stated as 350mA ~ 1000mA, so what value do I use, is any value between these okay?

Just incase, here's the specs of the LED:
Colour: Red
Wavelength: 620-625nm
Luminous Intensity: 62
DC Forward Voltage: 2-2.4V
DC Forward Current: 350mA-1000mA
PCB Size: 20mm
View Angle: 130 Degree

I know this is probably a really stupid question with a really simple answer, but my 2 functioning brain cells don't know what to do. Any help would be greatly appreciated, have a nice day!


texts: Why -3 dB in signal to noise ratio (SNR)

texts:
I'm reading about a signal to noise ratio (SNR), I'm quite new to this kind of stuff.
$$SNR=10\log_{10}\left(\frac{P_{SIGNAL}}{P_{NOISE}}\right)=20\log_{10}\left(\frac{A_{SIGNAL}}{A_{NOISE}}\right)$$
I don't know why I read two times that the SNR is set to be:
$$SNR=20\log_{10}\left(\frac{A_{SIGNAL}}{A_{NOISE}}\right)-3dB$$

  Why to put as a baseline -3dB .

I read online that is a recurring number for this I ask the question but I don't know where it comes from


texts:
I currently develop embedded systems using a number of different compilers, the most common coming from IAR systems.

My love of hardware is what drives doing embedded systems and firmware. I however seem to lack quite a bit in software engineering.

I have read many times that a good Lint is invaluable for code. I would like to know if anyone on here uses a Lint, which Lint it is, and how much it helps in detecting errors.


texts:
As mentioned here, I am a novice to electronics, and I am currently building a wooden workbench. The workbench will have an ESD bench mount and ESD matting over the entire bench. Furthermore, the floor is hardwood flooring.
In a comment by DKNguyen to this answer, it is mentioned that my fabric chair is a "no no" when it comes to ESD safety. In particular, I will be working with some sensitive components, like laser diodes, so I am indeed concerned about ESD safety. Even so, since money is limited, and since this is a home workshop, I do not want to overdo it with a setup that you would find in professional ESD-safe environments.
The problem is that ESD chairs seem to be very expensive, costing around $1000. However, I did find this "Dissipative Chair Cover", which is far cheaper than the ESD chairs; would putting such dissipative chair covers over non-ESD chairs be sufficient for ESD protection, or will I actually need a full "ESD chair"? If the chair cover is not sufficient, then what should I be looking for in an ESD chair? I found some "ESD chairs" that have the following description: "does not feature the conductive plastic components and steel components with conductive coating found on our other ESD models"; does this make them insufficient for ESD protection?
And, lastly, is it sufficient to just have an ESD chair without ESD-specific flooring?
I would greatly appreciate it if people would please take the time to help me with this.


texts: What do I call this wire-to-board connector?

texts:
I'm repairing a toaster oven and have encountered this connector. What should I call it when I search? This is a power connector.

It says "R8 JD" on the base of the male part. It is 3/16" wide.

Below is the female part. It says "8 STS".

Here they are before I disassembled it.


texts: Did I build this AC-coupled emitter follower correctly?

texts: Some connections seem to lead nowhere on the diagram...


texts: MC33063A Boost Converter IC Getting Really Hot and Voltage Sagging

texts:
I'm having a lot of trouble trying to design a boost converter using the TI MC3306 IC and I am wondering if I mathed this out correctly.

The chip gets extremly hot to touch and the voltage sags.

The input is 3.5v. However, when I add any sort of load of around 0.8-1 amps reported on my power supply, the IC gets really hot, the voltage sags to about 8V. Smaller loads sag less and dont heat up as much. I have calculated the values for 1.5A maximum draw (the chips max rating)

I have tried a few different inductor sizes, all with similar results, 1uh, 3uh, 10uh and 20uh, none of which have solved the problem. The inductor stays cool though. Orignal calculated result is 23uH.

Our load pulls 0.5A straight from the PSU, when attached to the boost, it pulls between 0.8-1.3A. Something in the circut is causing a large inefficiency. I am not sure why this is happening. I had another engineer take a look and they are also not sure. This is my last hope! Thanks greatly for your help. Please let me know if I'm  missing info. :)

Required Specs:
Vin:3-4V
Vout: 11V
Max I: 1.5A
F: 100KHZ
Inductor I saturation: 2.2A

IC Datasheet: http://www.ti.com/lit/ds/symlink/mc33063a.pdf?HQS=TI-null-null-digikeymode-df-pf-null-wwe&ts=1590606565705

Pics: 1. Schematic, 2. No load, 3. With load (1.2A reported by PSU)


texts: Why are properties of components often given at 1 kHz?

texts: The title pretty much sums it up.  Aside from DC, why are the properties of components often listed at 1 kHz?  I keep hearing that it is a "standard", but why 1 kHz?  This seems to be pretty common in the datasheets I've come across (primarily for ceramic disk capacitors), but have never seen the reason why 1 kHz was chosen.  Also, I have a couple of hand-held capacitance meters that use a 1 kHz pulse to measure capacitance/ESR on components.


texts: bipolar LED across a switch to indicate off/on

texts:
I'm working with this drawing to indicate the switch on a distribution panel on my boat.  Green/OFF & Red/ON.  12vdc One trouble is that the total ma is quite high when you add up 8 switches.
http://www.instructables.com/id/The-RedGreen-LED-Guide/step2/null/
I'm thinking it would be more efficient using transistor gates as in this 2nd drawing down on this page, but that's a single led and I want to use green/red bipolar for switch OFF/ON.
Understanding Transistors
Thanks for all your help.


texts: Open Error on host while using VCP on STM32

texts:
I use STM32F407G-DISC1 board. I have run some examples with VCP based on STD library. Everything is OK. Then I have tried to generate code by CubeMX. And something interesting happens.

If not to add any code, then VCP is defined by host and Terminal can connect that.

If I add CDC_Transmit_FS in endless loop of main(), it works

volatile uint32_t time_var = 3e7;
while (1)
{
    while(time_var) {
    time_var--;
}
CDC_Transmit_FS(b, 4);
time_var = 3e8;
}

If instead of internal while loop I use HAL_Delay function, then terminal can't open the port.

while (1) {
Hal_Delay(5e3);
CDC_Transmit_FS(b, 4);
}

So, COM port is defined in DeviceManager, but terminal can't connect that. It happens even before the first call of CDC_Transmit_FS, though hUsbDeviceFS is already initialized.


texts:
I've got this part specification for the Paste Mask excerpted from the datasheet:

There's a lot of lingo in this short paragraph that I would like to better understand conceptually. Specifically I want to know how to implement the prescribed characteristics using Eagle CAD layout software (I'm using 6.2 currently). I have done a lot of work in Eagle, including making my own symbols and footprints, but I have never messed with the default tStop (which defines the solder mask) and tCream (which defines the stencil) layer data, but rather accepted the automatically generated rectangular data that comes along with the land patterns.

I don't see anyplace where I can specify toe, heel, mask ratio, or extensions. So what are these terms referring to and how do I implement a fully compliant paste mask in Eagle?

Here's an example of what you get from by default by placing a rectangular land pattern:

UPDATE

The datasheet has these two additional pictures related to the footprint:

I'm having trouble reconciling the Paste Mask and the Solder Mask recommendations. In particular, the direction to "not place copper traces or solder mask underneath the module" in the Solder Mask section seems like a prescription that the there should be a no tStop in that hatched area, and that that same area should have a vRestrict and a tRestrict cover. Here's what that looks like when I implement it (showing vRestrict, tStop, tPlace, and Top).

It seems like I wouldn't be able to route signals to the pads in this case without taking DRC errors at every pad (because tRestrict = vRestrict, and that covers the pads entirely). Furthermore, these directions also seem to be in conflict because doesn't there have to be solder mask between the pads at least? If I add another tStop area over top of the vRestrict/tRestrict area, what was the point of me putting a tStop over the pads (1:1)? Am I missing / misinterpretting something?

Finally, here is a screenshot of my tCream layer in the same context as the tStop layer is shown above.

Same sorts of questions - does it make sense of the stencil to be cut in such a way that there are openings where there is no copper?


texts:
I'm trying to avoid the use of a level shifter in a design, but it would unfortunately require that I communicate at different voltage levels than what I power the device at.

If I communicate with a sensor from a microcontroller with 3.3V logic level I2C lines, but I power that sensor at 1.8V, am I in for big trouble (permanent damage to the device, inability to communicate)?


texts:
[EDITED]

I seem to have confused the terminology between signal and power planes! There is a ground plane, plus potentially four power planes -- +/- 15V, +HV (200V), and i'm not sure if a -VREF (~ -7V) reference voltage should be considered a "power" or a "signal".

I guess what I'm really wondering is whether it's considered kosher to turn the +/-15V, +HV, and -VREF into solid copper layers analogous to the ground plane, as opposed to trying to draw out all those traces.

[Original]

I'm laying out a schematic for a piezo driver on a multi-layer PCB. The schematic has potentially five signal layers -- a ground, +15V, -15V, -VREF (-6.95V), and a +HV (+200V). Is there any advantage/disadvantage to having 5 signal planes? Is there a "best practice" on how to order them? The output is a ~0-150V signal, which might be a low-frequency sweep of ~ 10 to 100Hz, or a high(er) frequency dither of ~ 1-100kHz.


texts: Why current gain of common emitter transistor changes with the change of transistor

texts:
I was reading a book on basic electronic engineering and there it said that if we replace a transistor with a new one and even if we keep all other parameters same for both transistors then also the current gain is likely to change.

But I couldn't justify why should gain change if we keep all parameters same. Thanx


texts: How to tune a PID controller to a nonlinear process

texts:
I have a nonlinear thermal process (nonlinear radiation becomes more and more present as temperature goes up) that I would like to tune a PID controller to. I'd like to control the temperature as accurately as I can.

I have planned to divide the temperature range in N pseudo-linear ranges (to be defined), and for each of these temperature ranges: fit a first order model using a small temperature step, and calculate the PID parameters to suit this model. The PID parameters would be automatically switched depending on the temperature of the process*.

My issue is the following: consider the 70°C checkpoint for example. P watt are already flowing to reach this temperature. I'll inject dP watt to increase the temperature by 1°C. I'll then make a note of the time constant, and the steady state gain will be 1/dP °C/W. [Please can you take a moment to think about whether this is right?] Finally, I'll tune the PID to that plant to get the parameters for that temperature range, and move on to the other ranges.

Now, assume the process reaches 70°C. The new parameters are loaded and the integral counter reset. The error may be 1°C, but the power required is much more than that to reach 21°C, it is certain the controller will demand less than P watt. This means the temperature will droop a lot before the integral term demands P watt, and only then will the dP additional watt eventually bring the process to 71°C (and it will certainly overshoot). The bigger P is compared to dP, the worse it gets.

It almost seems like the heaters should be driven with the sum of the controller output, and the power required to stay at the current "reference temperature" (e.g. 70°C). But off the shelf controllers do not offer that, so there must be another way.

What am I missing? What's the proper way?

*: It's effectively Gain Scheduling.


texts:
I'm working on firmware for LED display composed of Chinese RGB LED matrix modules (1/4 scan, 16x16, RGB). I want to find out how some pictures are displayed in three colors, is there any idea behind this, I know we're using different duty cycles (PWM) for different brightness of pixels but how all that is combined and well displayed on that big display panels? Is this control very complex or it just seems complex to me?

I'll be very thankful if anyone explain this or have an idea from where to start when writing firmware for displaying full color images on RGB matrices?


texts: How to Increase Solar Charge Controller Output Amps

texts:
I am new to solar panel system set ups, and I'm trying to make an off-grid DC-DC solar panel system where in I will be running a bunch of 12v loads which are mainly DC Pumps cause its gonna be something like a waste water management and recycling system.
Then, I saw this guy online selling his solar panel set up for a cheap price and he is near to my area, and so I decided to grab it.
Here are the specs of the solar panel system that I just bought:

310W Solar Panel

40A MPPT (ML2440) SRNE Solar Charge Controller

150AH Sealed Lead Acid Battery

1000W Pure Sine Wave Toroidal Inverter

And just before I bought it, I thought that the "40A" in the 40A MPPT SRNE Solar Charge Controller stands for the output the SCC(solar charge controller) can give from its load terminals.
And now that I have it and have read the manual, I realized that its Max Discharging current is 20A only.. (or maybe I'm wrong.. please correct me, I'm just googling everything and watching YouTube videos)
Going straight to my problem number 1:
I have calculated my estimated load, and it is around 23Amps..
I am thinking, is it safe to connect a buck converter to the battery bank directly in order to get more amps for my project?? because the SCC can only give 20A, and I don't wanna compromise the performance of my loads..
cause I have 5 loads to power, and I thought, if 4 of my loads sum up to 19A, I'll power those 19Amps with the power from the load terminals of the SCC, and then for the 5th load, I will just connect it directly to the battery bank and just use a XL4015 buck converter to regulate the voltage if its too high.. Is it safe to do so?? If not, how can I increase the 20A to 23Amps with the safest way possible.
my question number 2:
If a load's specification let's say needs 6A, does it really use up 6A all the time?
I know that you can run a 6A load with a 10A power supply but not the other way around, but I am genuinely confused, here's the story why.
When I met up with the guy to whom I bought my solar panel set up, I talked to him (I just assumed that he's an electronics and electrical stuff expert) about running some 12V DC motors and Arduino on a sealed lead acid battery that goes to 14.4V to a little less than 15V when fully charged.
I asked him if it is safe for devices to run them on voltages a little bit higher than its requirement of the load
Example: Running a 12V Pump with a battery voltage of 14V (lets just assume the sun is like really really bright for most of the day time)
and how do I increase the Load Current Capacity just incase I need to add more load to my project..
The guy then weirdly took the 12V DC Pump I was holding that time and then tested it directly to the load terminals of the Solar Charge Controller, please note that the battery voltage at that time was 14.4 volts, and he said,
"Just because it says 6Amps on the item's specification doesn't mean it takes 6A constantly"
I've read about overvoltage and that how dangerous it is, but I am now weirdly confused AF because of that guy's answer to my question to him.
I've been googling all day and watching YouTube videos about my question but I can't seem to find a good answer to it.
Somebody please enlighten me and correct me. (T__T)
I might be wrong, I'm really sorry, I'm just trying to build this project idea on my own and I thought I could get some answers to my questions from the experts here.
Any form of comment or suggestion and corrections to me will be highly appreciated.
Thanks! :)


texts:
Maybe this question does not belong here but here, but since this webpage is for electric circuits in general and not for LTI systems that is why I post it here.

I have to compute the group delay and the frequency-response phase (which I don't know if it is the same as the phase delay) and I would like to know if for the frequency-response is enough to use P(H(w)) in PSpice, if someone is familiarized with it.

Also, consider the following phase response of a low-pass filter:

Where the simulation is up to 10Hz, but now if I perform it for 900MHz:

where I have cropped it up to 10Hz again. Is exactly the same circuit but the simulation is computed for a bigger frequency (as I have said) but the graph is totally different. Shouldn't be the same shape for both graphs? And which one of them should be the best option if the following specification mask is chosen?

where \$\omega_p = 1\;rad/s\$, \$\omega_{a1} =\;4.08 rad/s\$ and \$\omega_{a2} =\;4.36 rad/s\$. My guess is that the first one is the best option since the managed frequencies are pretty low.

The schematic in PSpice is the following one:

which corresponds to a Butterworth filter of order \$n=3\$

and the parameters of the simulation (frequency domain):

for the first one (for the other one End Frequency = 900meg). The stimulus has the AC option equal to 1


texts: Quartus produces different synthesis for same design

texts:
I synthesized my design in Quartus for Arria 10 in a remote server. In my memory instantiation, it is saying that it is unable to infer a Block RAM due to asynchronous reads. I tried to synthesize again in my local machine, this time setting a DE1-SoC FPGA as the target device. It properly inferred my memory instantiations as BRAMs. To test my sanity, I decided to bring it to board level in my DE1; the design functioned as expected. I'm just wondering why Quartus produces different synthesis for the same design? Are there some compiler commands that I can use to force Quartus to infer my memory instantiations as BRAM? Thank you.

From the terminal in remote Server:

Quartus Prime Design Software

Version 17.1.1 Build 273 12/19/2017 Patches 1.38 SJ Pro Edition


texts: Circuit for selecting between PCB antenna and external

texts:
I'm just developing the second iteration of an 2.4Ghz sensor and receiver set. Because I can't afford the expensive development path of a big commercial project and because the environment these products get placed in is not constant or easy to stimulate, I'm trying to incorporate both an external antenna connector and a PCB antenna, with the option to select between the two.
To sum it up:

Allow for switching between the PCB antenna and the external one. It's ok for this to be done by soldering/removing components.
Have connectors (UFL) for both external antenna and VNA needed for antenna tuning.

Given the above, I was thinking of the following solution:

Transmitter ->
UFL with short stub for VNA ->
PI matching network ->
UFL connector for external antenna ->
0 ohm resistor with two positions to select between PCB and external antenna

Does that sound like a good solution?


texts: How to define the circuit that replaces the variable capacitor in its use with the TDA7000?

texts:
In the circuit below, there is a subcircuit that connects between C4, D1 and the VCC (5V), with Q1 and D2 as the central component, this circuit seems to me to be a Gyrator, I know that Gyrators are a choice to replace coils, however here it replaces a variable capacitor.

How is this circuit characterized? is there a standard that defines it, is there any paper that defines it clearly?

source: https://www.py2bbs.qsl.br/tda7000_fm_receiver.php


texts:
I am trying to calculate the frequency of the internal oscillator, in order to go through the design procedure listed in the datasheet. The problem is that it gives me answers that contradict the 100kHz max f specification. Here is my calculation with the example values in the step-down converter example:

Here is the datasheet I am using:

http://www.ti.com/lit/ds/symlink/mc33063a-q1.pdf

To find the discharge time (tdis), I am using the following values:

C = 470pF (CT on figure 13)

dV = 0.5V (Section 7.4)

Idis = 200mA (Section 7.4)

I then calculate:

Idis = C * dv/dt  ---->  dt = C * dv/Idis

dt = 470pF * 0.5/200mA = 1ns

since the charge time is 6 times the discharge time, the period T is 7ns, which gives a frequency of approximately 143 MHz. What is happening here?


texts:
For the system $$ \dot{x}(t) = A(t)x(t),\quad x(t_0) = x_0\quad (1)$$
we say it's uniformly stable if $$\exists \gamma : ||x(t)|| \leq \gamma ||x_0||\quad t \geq t_0\quad \forall t_0,x_0$$

However, from the state transition matrix context, (1) is said to be uniformly stable iff $$ \exists \gamma : ||\phi(t,\tau)|| \leq \gamma \quad t\geq\tau\quad \forall t,\tau$$

Since $$x(t) = \phi(t,t_0)x_0$$, I'm wondering what explains the 'if' and 'iff' discrepancy. Reference: Wilson Rugh's Linear Systems


texts: Armature reaction of a synchronous generator

texts:
I quote from my book-

  When a synchronous generator's rotor is spun, a voltage EA is induced in the
  generator's stator windings. If a load is attached to the terminals ofthe generator,
  a current flows. But a three-phase stator current flow will produce a magnetic
  field of its own in the machine. This stator magnetic field distorts the original rotor magnetic field, changing the resulting phase vo ltage. This effect is called
  armature reaction because the armature (stator) current affects the magnetic field
  which produced it in the first place."

When the rotor magnetic filed BR crosses the coil EA is at its maximum value. So, BR and EA coincides. A lagging load is attached with the generator. So the current will lag. Assuming IA where it is in the picture.
My question is, why is BS is perpendicular to IA. It should be perpendicular to the plane the coil is on, in other words, it should be perpendicular to EA applying the right hand rule. Align all your fingers to the direction of current flow, the thumb will show the magnetic field direction.


texts:
On the SAM Xplained Mini boards, does anyone know why the ATmega32U4 debug MCU has EXT_CLK wired to its PB5 pin please?
Or, has anyone clocked the target MCU (e.g. SAM D10) on that board with an external oscillator, not the 8MHz one provided by the ATmega32U4?
TIA.


texts: voltage in an electrical circuit consisting of a current source

texts:
In the following circuit is it correct to ignore the current and simply add all the voltages to measure voltage at open end?

simulate this circuit – Schematic created using CircuitLab

If it is required to calculate the voltage at open circuit then what I am doing is:

$$V=V1+V2+V3$$

Is it correct to ignore the current source?


texts: Communication between Microchip PIC24F & Android device

texts:
I am working on Microchip with Android Application via Android USB framework.

Currently, I have written a while loop to generate the random number continually.

It is possible to retrieve the random value that the Microchip generate through writing an Android application but do anyone knows how to do it?

I had research on-line but the information are very limited due to new technology!

The software I am using:

MPLAB IDE on Windows Version 8.73 MPLAB C Compiler for PIC24 and dsPIC v3.30

Eclipse on Ubuntu

The device/tools I am using:

DM240415 - PIC24F Accessory Development Starter Kit for Android


texts: Finding the sinusoidal input voltage of an amplifier

texts:
An amplifier has a linear transfer characteristic passing through the origin (0, 0) and with output
  voltage saturation at L+ = 10 V and L– = –8 V. The amplifier gain is 100 V/V. What is the amplitude
  (in mV) of the largest sine-wave input having no dc component that can be applied without causing
  output voltage distortion?

I tried to take the middle point (L+ - L-)/2 = 9, dividing it by the gain, but this only gets me the sinusoidal voltage assuming there is a DC component.

(The answer to this problem is 80 mV, but I'm getting 90mV).


texts:
I need to design a breakout board for this Cree XHP50 LED. It is a 12V LED that I would like to run at 1.5A.

It will be turned on by this ON Semi NSS12201LT1G NPN transistor, which is connected to a 12V power source and an ESP32. I will use PWM on the ESP32 in order to slowly dim the light in and out over the course of 30 minutes.

I am concerned about a couple things and would really appreciate any help.

SMD Pad

Here is the pad required for the LED. However, I don't understand how to wire this up to the 12V power source. Do I run a VCC trace to bottom left and GND to the upper right? Won't the thermal pad cause a short?

Heat Dissipation

Is it a bad idea to place this on a small 2 layer breakout board? I plan on making a ground plane on both layers, but is this still a bad idea without a heatsink or aluminum PCB?

I don't understand what Rj-a means at why there are different temperatures for different lines.

Thank you so much for your time.


texts:
I have a previously used a resistor component in my project that originated from an *.intlib library.

Now I want to use an alternate footprint. However, I cannot access the .schlib file of the alternate resistor component in order to add the new footprint to the model.

What should I do?


texts:
I have installed keil v5 and installed STM32 package.
When I start the STM32 project and add  the Software components

Here is the directory


texts: SMD Fuse - DC voltage rating higher than AC?

texts:
I would like to use the Bel Fuse C2Q (https://belfuse.com/resources/datasheets/circuitprotection/ds-cp-c2q-series.pdf) for a new PCB design. It is conveniently packed in a 0603 instead of the larger C1Q which comes in a 1206 package.
However, while I always thought that DC voltage rating for fuses was lower than AC, this particular fuse features a voltage rating of 32V AC and 63V DC. How is that possible? It does not make much sense to me and it makes me concerned that I should understand it better before I use it in my design...
The circuit runs some motors out of a 24V lithium-ion battery, so I am not expecting any proper AC, but maybe some spikes here and there. While the 63V DC is totally fine, I don't like that 32V AC very much. Any advice?


texts: Finding the kVA loading after improving the power factor

texts:
This is a homework question I've been attempting. But the answer I get doesn't match with whats given and I don't understand why my method is wrong.
This is the question with answers.

Here's what I've done.

I'm still new to these calculations. Thanks in advance.


texts:
I thought earlier that zeros  have no direct effect on stability but when I read the below article of Wikipedia where it said under the heading "Effect of poles and zeros "

It says that adding zeros to transfer function pulls the root locus to left, making system more stable

Why this difference in concept about effect of zero on stability?

https://en.m.wikibooks.org/wiki/Control_Systems/Poles_and_Zeros


texts: What's the point of a "flipped" opamp power supply (going from -9V to GND)?

texts:
I was looking at the attached schematic and realized that all opamps and transistors are "flipped" in respect to their power pins. I realize that this is only another way of writing the same thing with +9V on the positive rail and GND on the negative one, so what's the point of this?

Bonus question: Why are the headphones and the Line Out in rerence to GND (positive rail) and the built-in speaker in reference to -9V (negative rail)?


texts: General Purpose Solder for Beginner's Toolbox?

texts:
I've been asked by a friend to make such a recommendation, to go along with his new Weller WES51.  I've told him:

60/40 tin/lead
rosin-core
good name brand, such as Kester

What's a good size to recommend for general purpose use?


texts:
In this project i want to control dc motor with numeric keypad.
when I push a button first time, it works properly but when i push a button second or third times it does not react and it stays button that I pushed first.

Here is the code:

#include "io430.h"
#include "in430.h"

#define ileri BIT0
#define geri BIT1

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;

  DCOCTL=CALDCO_1MHZ;
  BCSCTL1=CALBC1_1MHZ;

  P1OUT = 0x00;
  P1DIR = 0x0F;
  P2OUT  = 0x00;
  P2DIR &= ~BIT0;
  P2IE   = BIT0;
  P2IFG  = 0x00;

  _BIS_SR(GIE);

  for(;;);
}

#pragma vector=PORT2_VECTOR
__interrupt void P2_ISR(void)
{

 if((P1IN && 0xF0) == BIT5+BIT6+BIT7)
 {P1OUT =BIT0;P2IFG  = 0x00;}

 if(((P1IN && 0xF0)== BIT6+BIT7) && (P1IN && BIT5) == 0)
 {P1OUT =ileri+BIT2;}

P2IFG  = 0x00;

}
when I push a random button and interrupt enable for ex.  if(P1IN == BIT5+BIT6+BIT7) =1 and  so P1OUT =0X01;. It is okay there is no problem but, if I push another button, second interrupt does not work. Although if((P1IN == BIT6+BIT7) && P1IN!= BIT5) =1 , I cannot make P1OUT= ileri+BIT2.

Could you help me please?


texts: Will a 5v radio be safe to power with a PC PSU?

texts:
I pulled a working PSU from a dead PC, and will I risk burning something with this circuit? WIll it cause a fire?

simulate this circuit – Schematic created using CircuitLab


texts: Does Kirchhoff's law apply to displacement currents?

texts:
When dealing with AC or RF circuits, does one need to take into account the displacement currents (as derived from Maxwell's Laws or Heaviside's formulation) when applying Kirchhoff's law to a circuit analysis?
Why (or when) is this not normally done in circuit analysis tutorials?


texts: How usable can results of measuring MOSFET resistance with a multimeter be?

texts:
When the resistance of a MOSFET at a certain gate voltage and current is needed, the correct value is ordinarily obtained by reading the datasheet for specified values.

Since a MOSFET is supposed to act as a resistive component, how good would results of measuring the resistance between drain and source be? I know that the current affects the resistance, but I plan to run the MOSFET at low enough current so that the effect shouldn't be too important.


texts:
I know that \$e^{jk2\pi}\$ or \$e^{\mathrm{integer}}\$ will give you 1, but I can't find the proof for why \$e^{jk\pi} = (-1)^k\$.

Can someone please explain how \$e^{jk\pi} = (-1)^k\$?

Does it have to do with the fact that it is a multiple of \$\pi\$ and not multiple of \$2\pi\$?


texts:
I've been reading articles about digital PID implementation.
So, in the discrete domain, we can write the parallel form PID law, as:

$$U(z) = E(z)*\left[K_p + \frac{K_iT_s}{1 - z^{-1}} + K_d\frac{1 - z^{-1}}{T_s}\right]$$

Where \$T_s\$ is the sampling time. It's also said that \$K_p\$, \$K_i\$ and \$K_d\$ are related as:

$$K_i=\frac{K_p}{T_i}\\ K_d = K_p\cdot T_d$$

where \$T_i\$ is the integral time and \$T_d\$ is the derivative time.

So, in the above equation I would get
$$K_i=K_p\frac{T_s}{T_i} \\ K_d=K_p\frac{T_d}{T_s}$$

Let's say I implement my control law, in discrete time (k), as:

$$u[k] = K_p\cdot e[k] + K_i\big(e[k] + e[k-1]\big) + K_d\big(e[k] - e[k-1]\big)$$

My questions:

is the integral time and derivative time (\$T_s\$ and \$T_d\$) defined by the clock period of the circuit that perform these computations?
if my error signal is sampled by the same clock that computes the integral and derivative parts of my law, \$T_i=T_d=T_s\$?
If \$T_i=T_d=T_s\$, \$K_p = K_i = K_d\$? It sounds really odd.


texts: Why aren't Stepper motors used in closed-loop systems and PID control?

texts: I know stepper motors are usually operated in open-loop systems. I'm curious to why they aren't usually part of closed-loop systems? Also why aren't PID control methods commonly used with stepper motors?


texts: Circuit to put digital amplifier into standby when no audio is at inputs?

texts:
I am putting together a battery powered audio amplifier using the PAM8403 class D chip.

http://www.diodes.com/datasheets/PAM8403.pdf

It has an active low STANDBY pin which turns off the circuits bias and brings idle current to <1uA. The PAM8403 will be powered by a 3.7V lipo battery and a DC/DC boost circuit to bring it up to 5V so I'd like to conserve all the microamps I can. I'm thinking of a circuit that checks for voltage or current at the amp inputs and sends the low signal to the STANDBY pin if nothing is detected after x amount of time. Ideally the circuit would have to be low current itself as it would be on so long as the battery is connected.

What are my options here? I tried google and couldn't find anything but I am thinking a small microcontroller might be the best bet?


texts:
i have two binary number

u8 buf[2];
buf[0] = 0001 1110; In dec it's 30 ; it is  High Byte and means 30 C;
buf[1] = 1100 0000; In dec it's 192 ; but its Low byte and means 0.75 C;

How i can return 30.75 C value?


texts:
I have to derive the Fourier transform of a half triangle which is shown here:

So far I got the equation of the line as 1-t/T, and now I think that I have to substitute into the Fourier transform definition with the limits set as 0 to T, but I'm not entirely sure...

(Sorry if I posted in the wrong stackexchange, this question is from my electronics course and thought here would be most appropriate)


texts: Why does PoE use duplicate wires for power

texts: When a PoE cable is used to transmit power, it uses two wires for DC+ and two wires for DC-. In contrast, a simple light bulb powered by a battery circuit uses just one DC+ wire and one DC- wire. Why two wires for each polarity in PoE? Is it because the gauge of the wires are very thin and may not reliably transfer power over larger distances?


texts: Spoofing or hiding monitor serial number

texts:
A MAC address of a computer can be spoofed by an FPGA which can be programmed as a network controller. I can set a custom MAC address to it. I turn off the motherboard's network interface controller in BIOS. I use the FPGA that is programmed as a network controller. A software can in no way fingerprint my computer.
SSD or HDD serial can be spoofed by Raid controllers which do not reveal the serial numbers of the connected SSDs or HDDs. A software can in no way fingerprint my storage devices.
How can I hide monitor serial numbers in a similar fashion?


texts: Can an offset:ed 9VAC be used as a normal 9VAC source?

texts:
Consider a normal sine curve for 9VAC; top hits +9, bottom hits -9V.

Then consider the same curve that's offset:ed, or "lifted", by a DC-voltage; top hits +18V, bottom hits 0V.

The second curve is produced by PWM from a DC-source, therefore there are no negative voltages.

Question: if one wants to use the lifted curve in a 9VAC-application (i.e. feed it), how can one "lower" it again? That is, putting the center back at 0V.

Is this at all possible?


texts: Circuit Charging Sealed Lead-Acid Battery (NP1270M)

texts:
I have a project (remote gate opener...) I have made good progress but its the first time I have built a charging circuit so I have some questions I need help with.

The battery I am using is a sealed lead acid battery NP1270M datasheet here

The gate will be near a power source and i will supply 18VDC @1.5A as an input to the circuit. The project has a Micro controller so I plan to implement automatic overcharge/undercharge safety. As well as switching I will limit the voltage and current (fixed amount). The battery will never be less than 80% so I was just going to trickle charge at a fixed rate until it reaches a voltage or the voltage no longer increases.

Questions:

What voltage should I use for "Fully charged" can't seem to find
that anywhere i.e. if reached turn off charging.
What voltage should I use for under-voltage protection (<12v?)
What voltage and current should I trickle charge at note: 30% in 8 hours will be quick enough.

I don't understand this from the datasheet:

Thank you in advance for your help.


texts: Recommendations on pyranometer In-amp design

texts:
I'm planning to build a pyranometer amp based on the AD620 In-Amp, at this point I would ask your knowledge on the following details:

a) Apart from using a 1.5v dry battery with a (huge?) voltage divider, is there another way to simulate the microvolt/milivolt signal level for the INA input? (I want to test the device by comparing the input Vs the voltage output using a oscilloscope and/or millivoltmeter).

b) Should I use a low-pass filter (cut-off freq around 40 Hz or less, to leave out the 50/60 Hz AC Hum) after the INA-amp or between the pyranometer and the INA-amp?


texts: Is it possible to measure the voltage produced in heart

texts: I learnt from my high school biology that human heart will produce about 1mV from the sinoatrial node.(voltage will vary like the graph in ECG test).Is it possible to measure the voltage with any instrument which can be available in a electronics laboratory(like multi meters,voltmeters,oscilloscope etc.) which is pre-amplified using a amplifier.


texts:
I would like to use (link) a function written in assembler in an Arduino project.
What I want to do is:

write the function in assembler using avr-gcc calling conventions
declare the function as extern in the .ino file
provide the instructions and other information to link the assembler function into the project

I do not want(or I already know how to):

use inline assembly (prologue and epilogue prevents effective parameter handling)
use alternative ways/toolchains/programmers


texts:
I am calculating RMS value of trapezoidal wave.

I found its formula like below:

and at last the RMS value formula:

u = 30degree or pi/6 --> especially pi/6
A = 12
When I calculate RMS value by this formula, I got 2 but by matlab, I got 11.314, when I calculate the RMS value by fourier series, I got 8.48 where did I make mistake ?
Here the codes
inputs = -pi:0.0001:pi;

outputs = zeros(1,length(inputs));
u = pi/6;
A = 12;

for i =1:length(inputs)

    if inputs(i) <= u/2-pi && inputs(i)>=-pi
        outputs(i) = -2*A*pi/u - 2*A*inputs(i)/u;

    elseif inputs(i)>=u/2-pi && inputs(i)<(-u/2)
        outputs(i) = -A;

    elseif inputs(i)>=(-u/2) && inputs(i)<=(u/2)
        outputs(i) = 2*A*(inputs(i))/u;

    elseif inputs(i)>(u/2) && inputs(i)<=(pi-u/2)
        outputs(i) = A;

    elseif inputs(i)>(pi-u/2) && inputs(i)<(pi)
        outputs(i) = 2*A*(pi - inputs(i))/u;

    end

end

mean(outputs)
rms(outputs)
%axis([-10,10,-4*pi,4*pi]);
plot(inputs,outputs);


texts: In my continued quest to design a poly synth I have decided to use XR1071(http://www.cq-dx.ru/upload/pdf/X/XR-1071.PDF) but only the right audio channel. would this configuration work for my purpose (a LPF/HPF/VCA)?


texts: How do i find Thevenin and Norton equivalent? [updated]

texts:
I tried calculating Vth, Rth and In but i am getting stuck at the V2 source.

simulate this circuit – Schematic created using CircuitLab

Can anyone explain why Vth=45?


texts: How hard/possible it is for an engineer to make this happen?

texts:
I need to get one of these power supplies to use it in something I'm developing. The problem is that where I live there are no shops that sell this.

What I need is this:

If I'm not mistaken, this is a power supply with a special form factor. This is exactly the form factor I need for my project.

However, like I said, no one sells it here, so I need to fabricate it from scratch.

Do you think this is a viable project for an Electronics Engineer?

I wonder maybe these power supplies are manufactured by machines and it is impossible/tricky for a someone to do it.

Edited: a PS of 12v and 2A will do.


texts: Determine the functions of the given multiplexers

texts:
In the following problem I want to understand a section of the overall problem. The image only show 2 MUX(es), however the original question has a lot more that are connected with one another.

Write the outputs for the following diagram only in terms of the relevant multiplexer inputs.

The first one is relatively simple because I use the same idea as for a normal 2:1 MUX. So for r I get r = (not a*0) + (a*1) = a. The value of r is then forwarded to two other MUX(es). For one of the given MUX(es) I have t=(not c*r) + (c*0) = (not c*r). Is this correct? I'm not a 100% sure.


texts: Is DRAM burst mode compatible with bank interleaving?

texts:
I am trying to understand how DRAM burst mode is compatible with bank interleaving.

Once a row within a DRAM memory array has been activated, sensed and buffered, according to the strobed row address, adjacent bits within the same row can be accessed very quickly by varying the column address for the same row, without the overhead of pre-charging, sensing, etc.  Indeed, the column address can be changed as fast as the clock supplying the data.

The first part of my first question is, do we refer to this as ‘burst mode’ and how does it differ from ‘fast page mode’ which I understand is now obsolete ?

If multiple arrays within the same BANK, let’s say 8 of them, are supplied the same row and column addresses (but a different line of the data bus), then it is possible to read or write 8 bits simultaneously in the same way (burst mode, fast page mode, or whatever it's called).

I also understand that data can be interleaved across multiple banks within a CHIP.  For example, a read request, for a particular memory address, can be issued to a bank, but there is no need to wait for the data to be returned before issuing a read request to a different bank within the same chip.  When I try to visualise what is going on inside the chip, I imagine 8 bits coming from one bank, then 8 from the next, and so on.  (I also imagine there are 8 chips all doing the same thing to keep a 64 bit data bus busy.) Interleaving groups of 8 bits across multiple banks within the same chip does not seem to be compatible with burst mode which expects successive groups of 8 bits to be adjacent.  My second question then, how do burst mode and bank interleaving work together, if at all?


texts: 24VAC relay coil buzzing when switched on

texts:
first time in here!

I designed a simple PCB to accomodate a relay, meant to switch a 230VAC(50Hz)- powered lamp using a 24VAC command signal. I used an ABB CR-P024AC1 (properly rated for my application) with a fuse and thermistor in series with the phase line (to protect from overcurrent and inrush).

About 90% of the time, when I switch on the command signal the relay activates properly but produces an audible buzz. This was tested both with and without mains voltage and lamp hooked up to the circuit. I have found that after letting the lamp switched on for an hour or so, the buzzing goes away, and I can switch it on and off a few times without it buzzing, then it starts buzzing again after a minute or two. It seems very likely that the contact arm causes this, however I don't see any variation in the intensity of light produced by the lamp.

I researched this issue, but all situations I found seemed to be either a result of controlling a DC relay with AC, or control voltage being too low.
In my case, I'm using a 24VAC, 1A wall wart as a quick way to provide the command signal for testing, and my cheap multimeter gives me a reading of 26V (using the 200VAC caliber). I must clarify that I have no previous experience working with relays.

Is this buzzing normal? If not, could this buzzing be caused by a low quality control voltage?


texts:
I might be mislead by some pictures of circuits i've seen, but is it possible to program a microcontroller (e.g. pic18) from a computer without a kit (e.g. pickit), but just with a self build circuit and software?

EDIT1: If it is possible, it would be great if point me in a direction where I can look for instructions on how it's done.


texts: (MULTISIM) Feeding sine wave into MOSFET - Getting modified sine wave on drain

texts:
I am trying do design a HF power supply/inverter for school. I stumbled across a problem.

When i feed a IRF740 a sine wave on the gate, the MOSFET gives a modified sine wave on the drain. Why is that? Can this be filtered?

Some screenshots of simulation:

The diodes and transformer are ideal.


texts: strobe/enable output pins role in MC14094B

texts:
I would like to ask about the "strobe" pin and "enable output" pin in MC14094B (shift register)
what does these pins exactly means? what storbe pin do? what is it's role ?
i would be glad for good explaining
thanks for helping


texts:
I want to cut/etch (would be satisfied with just etching, though prefer both) paper with a laser. I have on hand several laser diodes salvaged from various disk drives and a 633 nm 10 mW CO2 laser. I know that any infrared laser with more than 10W of power (and probably many with less power) should be able to cut paper easily, and have been told that my 10 mW laser will not be powerful enough, which suggests to me that my laser diodes will likely be lacking as well.

The only thing approaching a suggestion for laser power for paper cutting that I've been able to find online is a physics stack exchange question about cutting plastics that mentions un-cited that a 808 nm 2 W laser is standard for paper cutting.

Is any of the above likely to be true? Is there a way to get a laser that will etch/cut paper cheaply (< $100, say)? The closest thing to the 808 nm 2 W laser that I've been able to find is a number of ~450 nm 2 W lasers on Amazon. Should this be sufficient? Does restricting the paper in question to being white/black/green/whatever color change the answers to any of the above questions?

And a note to head off some possible responses- I have had laser safety training, I do not intend to use this laser recklessly or even myself- I intend to mount it on an X-Y table in an enclosed, ventilated space during operation.


texts: AND gate with a single input in a diagram

texts:
consider the following diagram:

http://ee-classes.usc.edu/ee459/library/datasheets/DM74LS181.pdf

( page 3 )

The first AND gate at the top left of the schematic has only one input! What does this do on a logic level? It seems strange to me!

Also: What does the NOT gate with the circle on the other side mean?


texts:
Using one operational amplifier, draw the circuit of an amplifier with the following transfer function:
Vo = 6V1 + 3V2 + V3.
Using one operational amplifier, draw the circuit of an amplifier with the following transfer function:
Vo = V1 + 2V2 − 10V

What I have tried:

Can you show the formula? Thank you


texts:
[EDIT: Found a couple of 12715 units in the pile that did suck the full amperage, but despite excellent cooling of the hot side, could not deliver much cooling.]

I'm waist deep in project to keep shot glasses full of beverage near or below zero °C.

After a reading of the charts of the easily available TEC1 series, I chose the TEC1-12706 and TEC1-12715 for my experiments.

As I understand it from the tech sheets, a module should can come close theoretical dT as the maximum heat absorption should also be available as long as full voltage and amperage are applied and the hot side is maintained cold enough.

No worries there. A simple cooling loop or even decent air cooling computer heat sink keeps the hot side cold and we get 95% of dT. Achieving cold side temps of -15 °C is no problem. In fact, we have achieved lower temps on the cold side simply by chilling the cooling loop of the hot side.

Clearly temperature is not an issue for us to achieve, but where we run in to issues is current and Wattage. For instance, a TEC1-12715 connected to a 12 VDC PSU capable of supplying 150 Amps is drawing a mere 60 W. Why is this?

In terms of heat dissipation, we have even gone so far as to use Stannol Kristall 511 solder that binds ceramic very well to aluminum and copper for very high W/mk. We have also (for reference) tried high W/mk standard CPU/GPU creams such as Grizzly Kryonaut, Grizzly Hydronaught, and Noctua's best. We also, since this is not a high compression project, tried silicone rubber heat transfer glue of 2.9 W/mk  and a special heat transfer epoxy of 8.7 W/mk.

We have tried bonding in every way conceivable - again, there is no problem with temperature, but dissipation of Wattage and module power consumption are low. I think we can all agree that a single TEC1-12715 affixed to cooling source maintaining 30 °C and the cold side being at -15 °C is normal. Literally soldering or using a high W/mk glue or grease to a milled and polished aluminum shot glass should freeze 25 °C liquid in minutes or less. At best, we can remove 1 °C every 3 minutes and at best achieve 8 °C at the coldest.

In tests, the 12715's did cool the intended liquid much faster than the 12706's. Ideally, the TEC units will cool a basin of salt water to sub-zero C and our shot glasses will sit in the water, but we are open to other ideas.

We've seen TEC machines that can cool a bottle of wine or soda to 7 °C in 12 minutes. Clearly we re missing something.

So... what are we not understanding or do simply have a bad batch of TEC units?


texts: How does capacitor block DC when an AC signal is superimposed on top of it?

texts: This question has been in my head for so many days. When I was studying BJT amplifiers, capacitors were used for blocking DC. It is called a coupling capacitor. When the AC signal is superimposed on DC and is applied to the circuit shown, what would be output across R(Vo)? My professor told that we will get a sine wave(5sinWt) with reference to ground and DC(10) would be eliminated. But I am not able to visualize the waveforms across C and R. I want to know how capacitor charges and discharges and blocks dc. Please help me with the waveforms.


texts:
I'm a beginner:
If the mobile phone charger has two USB ports for output and the charger is labeled 4.8A, does it provide 4.8 maximum to both ports or to each port when cables and mobile phones are connected?
If only one cable and phone are connected, what is the maximum output?
How does it affect the speed of charging?
Is there a splitter or simply a joint in the wiring?


texts:
I mostly know how electricity flows but cannot understand some aspects, and have three examples that I cannot fathom:

The pilot lighting electrode wire on my house central heating water heater /furnace generates a high voltage spark and is covered by approximately 0.5mm of insulation.  You can hold it with no effect whilst it's sparking.  When I stand on my foam lino floor wearing plastic soled trainers and stick an electrical screwdriver (one of those that light up when there's voltage at the tip) into a regular power socket (240V), it lights up.
Some people recommend against using a hair drier whilst in the bath because you might get an electric shock if it falls into the water.  Super grid (400kV) pylons get rained on and totally covered in freezing ice, from the wires themselves, over the insulators, right to the metal support structure.  Nothing happens.
Train surfing is ill advised by some as you might get a shock by arcing from getting too near to the power cables (25kV).  The same cables sometimes pass within 100mm of cast iron bridge beams in low clearance situations and there is no arcing to ground.

These examples seem contradictory.  I know that this is crazy, but it almost seems that anything that I can do personally is dangerous, but anything done commercially works safely.  Can anyone explain them?


texts: Why does non-inverting input of non-inverting amplifier need a path for DC to ground

texts:
Wikipedia says that, but doesn't give any explanations.

  The non-inverting input of the operational amplifier needs a path for DC to ground; if the signal source does not supply a DC path, or if that source requires a given load impedance, then the circuit will require another resistor from the non-inverting input to ground. When the operational amplifier's input bias currents are significant, then the DC source resistances driving the inputs should be balanced. The ideal value for the feedback resistors (to give minimum offset voltage) will be such that the two resistances in parallel roughly equal the resistance to ground at the non-inverting input pin. That ideal value assumes the bias currents are well-matched, which may not be true for all op-amps.

As far as I've concerned, it says just like it really must have this path in case the signal source does not supply a DC path. Then, it says about a consequence of making this path such as bias current which produce extra input offset voltage and so on.

Some people say the input does need to have DC path to ground. They say in case there is no path to ground and the non-inverting pin "hang in the air" for some unwanted unexpected reasons, the op-amp may go into saturation or something like this.

Other people say it doesn't need for the input to have this path. Opinions divided.

What do you think?

UPD: Added the schematic to avoid misunderstood. The schematics a little bit differs from the schematic in the question Use of 100K ohm resistor along with 0.1uF capacitor?
So then maybe my question is not duplicated...?

simulate this circuit – Schematic created using CircuitLab

The values of R2 and R4 (as well as value R1, though) are default cause they don't matter in this scope. We discuss the role of R1.

UPD:

I've found out one more opinion that seemed for me to be suitable.

They say, that this resistor (R1) can help to attenuate some noise which source has large internal impedance. Source of noise and this resistor forms some kind of voltage divider and this divider attenuates the noise significantly.

It seemed to be possible explanation.