texts:
For an application I am building I need a custom DC/DC convertor that can convert a voltage ranging from 60V-600V to a contant voltage of around 5V.

Using the TI Webench with the paramaters Vin_min = 55V, Vin_max = 650V, V_out = 5V and Iout = 0.5A gave me the following schematic:

I tried to buy as many of the components that were provided by the TI Webench, and where I wasn't able to find the exact suggested component I bought an equivalent one. The design also required me to wind my own transformer (T1).

After building the PCB and testing it I've gotten mixed results which do not satisfy my need. I've already tried to understand the schematic, went through all the datasheets and asked around with my colleagues but no one seemed to be able to explain to me how this schematic works.

The output I get is a sawtooth with Vpeak of ~4.8V and Vmean of ~3V, which I think means the switcher turns off too fast since the output doesn't reach the desired 5V. The UCC2813-0D does behave like it should we think, since it's Vcc is around 7.5V (turn-on threshold is 7.2V) and we can see switching happening on the output. However, the switching frequency is around 66kHz instead of the 102kHz we expect (can be calculated with F = 1.5/(Rt*Ct)). I will add some oscilloscope screenshots later.

After some testing and measuring we noticed that when the CS pin (current sense comparator used for overcurrent protection) on the UCC2813-0D went above ~1.35V, the IC seemed to shut down. This is reflected in the electrical characteristics, which state that overcurrent threshold on CS has a minimum of 1.32V. We tried replacing the Rsns (current sense resistor) with a lower resistance value, but still reach the over current threshold and get the same behavior on the output.

I was hoping someone on this forum could explain to me how this schematic works, and maybe point me to a possible solution as to why this design doesn't work for me. Pointing me in another direction that could also satisfy my design requirements is also greatly appreciated (req: Vin_min = 55V, Vin_max = 650V, Vout = 5V, Iout ~= 50mA).

Thanks in advance!

Note: in my design I connected both grounds with each other, since I didn't need and isolated DC/DC. I don't know if this matters for the functionality of the schematic but I think it is worth mentioning anyway.


texts:
We are planning to use the Quintic QN8007B FM transmitter in our new design because it is quite cheap and has I2S interface. I believe this chip is no longer produced, but it is possible to get hold of old stock items (guaranteed not to be fake). Although we usually don't use obsolete products, this product will only be produced once in a small volume < 10k units.
For our CE marking, we need to have documentation that all chips are RoHS compliant, including the FM transmitter. Unfortunately it seems that Quintic does not exist anymore. NXP acquired Quintic's Bluetooth Low Energy (BTLE) and Wearable businesses in 2015, but I don't know if the FM transmitter product lineup was included in that. I've contacted NXP, and they say that they don't have any information about the QN8007B.
So my question is where to get RoHS information for the QN8007B? Or information about who bought the FM transmitter product lineup from Quintic?
Note: I know that some products like car FM-transmitters sold in Europe today use FM transmitters from Quintic, so this information must be available somewhere (at least if the manufacturer follows the CE regulations). I also know that many chip-brokers sell the QN8007B with date code 2018 and 2019, which should indicate that the chip was produced also after NXP bought part of Quintic. But this could of course also be fake chips.
Edit: Please find the datasheet here


texts: Feeding a PCB dipole with single ended RF signal

texts:
As suggested how do you feed a Dipole antenna with single ended RF IC. I found tons of examples single antenna Line feeding a differential RF port on IC but not other way round.

What I want to do is feed a PCB DIPOLE antenna with singled ended feed from the IC and match the impedance. I have considered using a 50:75ohm Balun in reverse as per the below image but not sure this will work.
If I can use a discrete component only solution that would be great as well.
Any reference or advise would be great.

Freq 868Mhz.

IC RF line 50 ohm impedance.
Dipole antenna needs to be fed with 71,3ohm impedance.
Each leg of the Dipole I have as 82mm in lenght (164mm overall)
https://www.mouser.com/ds/2/611/JTI_Balun-0900BL15C050_2005-06-263841.pdf
EDIT: Using this circuit design with either a 50:50 ohm, or a 50:75 ohm Balun and matching accordingly ?

EDIT: To be as discrete as possible my current dipole feed circuit looks as follows, the device will be used to match the 50 ohm micro strip to the 73 ohm Dipole feed. any suggestions


texts: 2 layers pcb : ground plane at bottom layer, what to put on top?

texts:
Disclaimer: I'm designing a simple arduino based board, so I'm maybe over-complicating things, but I'd still like to do the board well.

I've carefully this answer : Decoupling caps, PCB layout, especially this part :

  It doesn't take local planes to do this. I routinely use the local
  power and ground nets technique even on 2 layer boards. I manually
  connect all the ground pins and all the power pins, then the bypass
  caps, then the crystal circuit before routing anything else. These
  local nets can be a star or whatever right under the microcontroller
  and still allow other signals to be routed around them as required.
  However, once again, these local nets must have exactly one connection
  to the main board power and ground nets. If you have a board level
  ground plane, then there will be one via some place to connect the
  local ground net to the ground plane.

I now have this board:

Now, according to Aisler: https://aisler.net/help/design-rules-and-specifications/ultimate-guide-to-robust-pcb-design, I should add some pour on the top layer.

Should I use a dummy signal to accomplish this ?

Edit : added detail on trace spacing :


texts: Taking the limit of voltage division equation

texts:
I'm required to take the limit of the voltage division equation(internal voltmeter resistance included as Rm) when Rm goes to infinity to show that the limit equals to the basic voltage division equation.

\$\varinjlim_{R_m\rightarrow\infty}\ \dfrac{R_1V_s}{R_1+R_2+R_m}\$

But I'm kind of confused.

So how should I do it?


texts:
What is the difference between a ceramic capacitor of the same dielectric, but different voltage rating?

Would the lower voltage one have lower ESR or ESL?

For example,

X7R 10uF 4V

as compared to a

X7R 10uF 10V


texts: Quantization Error Power in certain Bandwidth

texts:
[Marcel Pelgrom. Analog-to-Digital Conversion]

I'm having a hard time understanding how quantization error power changes with a different signal bandwidth? How come when we have a larger signal bandwidth, we have more quantization error power? Can someone explain it intuivitely?


texts: Is there a microcontroller equivalent of a DPDT Switch? I am trying to develop a product that requires remote reversal of polarity by incorporation some sort of an equivalent of the mechanism exhibited by a DPDT switch.


texts: How long could I run a 115 Vac window unit on a 12v 200Ah battery (using a 700W inverter from a 400W solar panel and assuming 100% efficiency)?  Thanks!


texts: How to achieve variable gain using a micro-controller

texts:
I have a sine signal Vsignal below which is AC coupled and will be buffered by an LT1490 to the line input of a MOSFET power amplifier.

I'm able to control the frequency of the Vsignal through Arduino. But I also need to control the gain through Arduino.

What approaches is possible for a variable gain? Is there any dedicated IC for such purpose? I need a variable output between 0.25Vrms to 3Vrms for instance. I have no experience on such topic. Input to LT1490 will be fixed 500mV amplitude i.e 1Vpk-pk. In case, how would a digital pot work for the setting the gain?

How about changing Rp with a 10k digital pot as below like a MCP41010? Does anybody have experience with such use?


texts: How are transistors on processor chips designed to withstand high operating temperatures?

texts:
The process for transistors grow smaller every  few years, and operating temperatures reach around 100 degree Celsius. This makes one wonder as to how these tiny designs are able to hold up within these conditions without breaking down. Specifically what factors other than the materials used (if any) could contribute to this resistance to heat.
As someone from outside the electrical field of expertise, I would appreciate it if the answer is put in layman terms as well.


texts: Ultrasonic sensor not detecting any values when using Arduino and LabVIEW

texts:
I have connected the circuit as shown.

The circuit works perfectly when I Use the Arduino ide.
When I use LabVIEW, the distance from the ultrasonic sensor is always zero.
The LabVIEW circuit diagram is shown.

The Arduino ide code is shown below.
        int thresh_=10;
        int pin=10;
        int dist_=0;
        #define echoPin 2
        #define trigPin 3

        long duration;
        int distance;

        void setup() {

           pinMode(trigPin, OUTPUT); // Sets the trigPin as an OUTPUT
           pinMode(echoPin, INPUT);

           Serial.begin(9600);
           pinMode(pin,OUTPUT);

        }

        void loop() {
          digitalWrite(trigPin, LOW);
          delayMicroseconds(2);
          // Sets the trigPin HIGH (ACTIVE) for 10 microseconds
          digitalWrite(trigPin, HIGH);
          delayMicroseconds(10);
          digitalWrite(trigPin, LOW);
          // Reads the echoPin, returns the sound wave travel time in microseconds
          duration = pulseIn(echoPin, HIGH);
          // Calculating the distance
          distance = duration * 0.034 / 2;

            Serial.println(distance);
           if (distance<=20){
            digitalWrite(pin,HIGH);}
           else{
             digitalWrite(pin,LOW);}
        }

What could be the issue?


texts: 5v power supply from 18650s - high power, low profile

texts:
I am trying to use 2 18650 batteries to power 288 APA102 LEDs. The LEDs require 5V, and have a max current draw of 60mA/LED for a total of 17.28A. I will also have a microcontroller attached (currently arduino micro), powering some other low-draw devices. So let's say I'm aiming to support up to 18A. Most of the time though, the current draw will be much lower.

My understanding is that I can use a buck or boost converter (depending how the batteries are wired), and outboard bypass transistor(s) to shunt additional current around the converter (with proper heat-sinking). I am curious though, are there considerations for the buck vs boost configurations? Is my stated understanding even correct? And lastly, will I need to protect my arduino somehow if I'm drastically changing the power coming out of the batteries (e.g. Strobing the LEDs from fully on to fully off)?

I'm open to alternative battery suggestions as well, but I need everything to fit in a cylinder of ~20mm, and energy density is very relevant for this project.


texts: Circuit design recommendation to prevent a failing regulator

texts:
I designed a PCB that contains, among other things, a switching regulator circuit and an H-bridge for a DC motor. The whole circuit is powered by a 15V Lithium battery. The switching regulator converts the battery voltage to 5V to power the digital logic on the board. The DC motor is driven directly from the battery through the H-bridge. The motor itself was torn out of a hand-held impact driver with a stall current around 15A.

Without the motor attached, I'm able to get full functionality of all the digital logic components, so the switching regulator is doing its job. When I attached the DC motor, however, the switching regulator went pop. It appears to be completely dead. No signs on life on any pin.

Here's the switching regulator circuit using an LT8609. I've intentionally cut off the input and output caps so the schematic will fit nicely on the screen. There's about 32uF of capacitance on Vin and about 88uF downstream of the inductor. VIN of the regulator is attached to the net named V_BATT:

Here's the H-bridge using the MC33883 H-bridge driver. I apologize if the image is unreadable here. You may have to view it in a separate tab on your browser or save it and open it in an image editor:

The ACS711 in the upper-right hand corner is just a Hall-effect current sensor.

Here's the sequence that I performed that lead to the LT8609 failing:
1. Battery power was applied to the circuit.
2. The LT8609 powered on and was stable, providing 5V to the digital logic components.
3. The microcontroller (which uses the 5V) was programmed in debug mode.
4. Almost instantly upon running the code in debug mode, the LT8609 popped.

The only instructions that were programmed into the microcontroller (besides the usual oscillator and other initialization settings) were:
1. Enable the H-bridge (set pin G_EN high on the MC33883).
2. Read a voltage value from a potentiometer.
3. Set the duty cycle (based on the pot value) of the PWM signals to the H-bridge to turn the motor. At the time, the pot was turned to 0V, which would have translated to a near-zero duty cycle of the H-bridge.
4. Loop forever

Both the LT8609 regulator and the MC33883 H-bridge are powered from V_BATT. The worst thing I can think of is the H-bridge caused a shoot-through condition as the microcontroller that controlled it was coming online. But even so, I don't see how that would kill the LT8609.

I would appreciate if anyone can give me ideas as to what might have been the culprit to help me troubleshoot. Also, point out any fatal flaws in the circuit that I'm missing.


texts: Do the self-induction cause change in magnetic field which again causes a self induction?

texts:
my question is: It is known that for a coil, if current is changed then the magnetic field inside the coil is changed, and the coil tries to oppose this change by inducting itself   However, should not we be concerning with the rest? I mean, the self inductance means that current was not changed as it was supposed to change, rather it increased or decreased more "smoothly". The change in current due to self-inductance must -according to me- cause again a change in magnetic field which again causes -a less effective- self induction and it goes like this.  Does something like this indeed exist and do we just ignore that in questions(freshman engineering) or is it something I made up?

Thanks in advance


texts: Make a pad connect to two nets with different names in Eagle

texts: I have a part that is an SMT 'jumper', it is unpopulated and you use it by bridging the pads with solder. I want to put a track from the pin pad to GND. But the pad pin needs to also go to an address pin on a controller. How do I do this in the schematic? I am currently just placing a track on the .BRD file, but this is hacky. The only other way I can think of is make it in the jumper part, again not ideal.


texts: Will this AC-AC SSR work for a safety start / stop switch for a power tool

texts:
I'm modernising an old bench saw, and I want to replace the switch it has with a safer one, so that the tool will not start if the power is disconnected and then reconnected. The usual way to do this with these sort of tools is a magnetic switch, basically a relay that has the coil connected to the output. The disadvantage of mechanical relays is that they can be accidentally triggered by a whack with a bit of lumber, and the cost. Industrial safety switches are too expensive for my home workshop.

So I figured out this circuit using this SSr from ebay. Power is off until the start button is pressed, which then "closes" the output side of the SSR. This energises the input side when the start button is released, so that it will latch on until the stop button is pressed. If power is interupted the SSR will switch off so that the machine won't start again until the user pushes the start switch.

simulate this circuit – Schematic created using CircuitLab

Just mentally replace the mechanical relay with an AC-AC SSR in the circuit above.

My question is: will running the output from the SSR back to the input work? It would on a mechanical relay, but I don't know if an SSR will work exactly the same. Also, will I need a varistor on this kind of SSR, or is one built in?

EDIT So this is the new circuit I propose. It has the start and stop buttons controlling the relay from a low voltage source, which has the benefit that I don't need to run mains wires around the cast-iron body of the saw to the switches, and I can add an indicator lamp to show that the power is on.

simulate this circuit


texts: What is the purpose of a diode in parallel with a BJT in a MOSFET drive circuit?

texts:
This circuit shows a complementary emitter follower driving an IRF 150 MOSFET. The textbook says that a diode D provides a path for the discharge of the base-emitter junction capacitance of transistor Q1. I don't really understand why this is necessary. Can't the base-emitter capacitance of Q1 discharge through R2 only? And what forces the charge to discharge through the diode only in this configuration then?
Note: the 2 BJTs are driven by a square wave (0-12V).


texts:
If you have a microwave frequency of say 2.45 GHz, would you use that frequency in a simple rectangle cross section waveguide, or do you need to use the "lamdba g" waveguide frequency I've read about and if so, why?

I don't understand why you specify one frequency (2.45 GHz)  but possibly calculate for another?


texts: How to calculate a electrolytic capacitor based on current and voltage to have the smallest ripple

texts:
I have built a circuit involving LEDs powered on 230V AC.

The LED current driver that is powered on 30V and contains 10 LEDs of 1W each.

10 of these modules are linked in series and are powered from 313V and it draws 80mA. The 313V is obtain with a bridge rectifier and a capacitor connected to the main line.

How do I calculate minimum capacity of the electrolytic capacitor based on current and voltage to have the smallest ripple?
How do I know the wattage on AC line? I know that the DC wattage is around 25W (313V*0.08A).


texts:
I'm trying to design a differential ADC circuit using the TI ADC10065 chip. It's a 10-bit, 65 MSPS ADC. In the datasheet they provide a sample circuit with a transformer in it. There's also a circuit generated by TI's ADC topology tool. It uses a differential op-amp.

Now I have a few questions:

I think I can tell what resistor/capacitor values to use for R5=R6=18 ohms, C1=C2=25 pF. Is this correct?

Is there a reason I should be using one circuit over the other? Why? I remember reading a document somewhere recommending the differential op-amp method for higher frequency ADC's (it came from another semiconductor manufacturer, don't remember which one).

How do I choose the value of RT (termination resistor)? Is it even necessary?

For R1/R2 and R3/R4 are there any design considerations I need to take into account such as matching impedance, or am I free to choose any R1=R3 and R2=R4 which meets the desired gain I want?

Should I buffer the input to the transformer/differential op-amp with voltage follower op-amps?


texts:
I know this is a very basic question but the answers returned by google are way too complicated for me to understand. I am not asking about modulation here. What I want to know is what exactly is carrying the data.

Please let me explain my doubts:

Suppose from my PC, if I want to transmit the number ten. It will be converted to binary and become 00001010. Then it will be sent to the modem which will convert to an analog signal. This analog signal will then travel over the wire and reach its destination where it will again be converted to binary and the user will receive the number.

Now if it were a digital signal, the value would be transmitted as a combination of high and low voltage.

What flows through the wire is current.

How does this current carry the data? Current is basically flowing electrons.

The speed of the electrons depends on the voltage applied (that's what I remember from school). But my data is received almost instantly.

So if it were current carrying my data it would not travel this fast.

I read somewhere that wires transmit data almost at the speed of light. How?

What is carrying my data? Only EM waves travel this fast.

Please help me. I may be missing a lot many basic points here. I have not studied communication modes.


texts: Aluminum SMD Capacitor replacement question

texts:
I want to replace the caps on this mainboard but I'm not sure what to replace them with. I don't know enough about capacitance and am not sure where to turn for help.

Here's a picture. I don't know what the y2, x2, 2j and w4 represent. I'm assuming the next number is the microfarads and then the voltage. So on the one with the 2j for example... Don't know what 2j is, but does the 220 under it mean 220 microfarads? And then 4 volts? I'm finding all kinds of different kits but nothing with those exact numbers and letters. Can someone please help enlighten me on what I need to get to replace these caps? Thank you!!


texts: Problems involved in going from 0805 to (say) 0402 surface mount?

texts:
In order to reduce the size of a PCB I will probably have to use smaller SM components. I currently use mostly 0805 passives, and am thinking about going to 0402 or smaller. Apart from power dissipation considerations, any pitfalls I should be aware of when making the transition?

The assembled boards will be made by a specialist contractor


texts:
I am considering using 2AWG welding cable from MC Master as the main power lines in a solar car. From everything that I could tell the specs are better than standard cable or battery cable, it is cheaper, and it is more flexible. Is there any reason that I should not use this cable? Is there another type of cable that I should consider? I need cable that is able to handle up to: 130A 105VDC

As I can not link to the product because of the way MC Master has designed their website the specs are listed below:

Welding Cable:

Model: 6948K931
AWG: 2
OD: 0.430"
Amp: 190
Volt: 600
Price: $2.70(per Ft)

Standard Cable:

Model: 7125K71
AWG: 2
OD: 0.378"
Amp: 130
Volt: 600
Price: $2.91(per Ft)


texts: What is this element on the far right of schematic described as "270 OHM"? Is this some kind of inductor? What is its purpose in this device (this is a reference design of dc-dc power supply of sim900 taken from its datasheet) and what would be an exemplary part number?


texts: Timer1 not counting T13CKI pulses on PIC18F4550

texts:
I have a big issue on Timer1 of a PIC18F4550. Actually I have connected a 4060 IC which provide a square signal of 4Hz on RC0 input of the micro-controller (please refer to attached image).
After launching the timer, It does not count the rising edges and stays always at 0. Here is my code for configuring Timer1.
void initialize_timer1(){
    TMR1H = 0;
    TMR1L = 0;
   // 16-bit mode, Main system clock is derived from another source
   // 1:4 Pre-scale Value, timer1 oscillator disabled, do NOT synchronize external and internal clock
   // Timer 1 source external pin (T13CKI), stop Timer 1
    T1CON      = 0b10100010;
    TMR1IF_bit = 0;
    TMR1IE_bit = 1;
}

void start_stop_timer1(unsigned char onOff){
    if(onOff == 1){
         TMR1ON_bit = 1;
    }
    else {
        TMR1ON_bit = 0;
    }
}

I launch timer1 is like this:
void main() {
    initialize_timer1();
    start_stop_timer1(unsigned char onOff);
}

But when I check the value of TMR1L and TMR1H I see that they stay always at 0.


texts: Severe Ringing when turning off bench supply

texts:
I have an HP E3610A and I've noticed a huge amount of ringing/hash when turning the supply on and off.  This is my test circuit.  The bench supply is set to 6V.  There are 2 clip leads (about 18" long) connected to a 0.1µF, 22pF, and 50 resistor all in parallel.  This is to simulate a load with some decoupling capacitance.

simulate this circuit – Schematic created using CircuitLab

When I turn the bench supply off there is a lot of ringing that gets up to almost double the set 6V, and I suspect this ringing is damaging devices attached to the power supply.

I tried @AliChen 's suggestion of checking the AC grounding.  Both the scope and supply are plugged into the same power strip, and I used a ground tip spring on the scope probe.  This is what I got:

I've tried wrapping the positive lead a couple of times through a choke and that did not help.

What is causing this ringing and what can I do to stop it?


texts: Very low frequency instrumentation amplifier

texts:
I'm trying to choose an instrumentation amplifier for very low frequency signals (seismic monitoring).

The trouble I'm finding is that on many of the data sheets, they only give response curves down to 10Hz or even 100Hz. I need to know the performance at .01Hz or .1Hz.

Could anyone please suggest a suitable component for this task?

Many thanks in advance,


texts: How can I make a fine tipped object emit an electric field similar to that of a human finger?

texts:
I've asked this before, but knew less about the tech and didn't word the question properly. I know other people have asked similar questions and knew little, so let me be as specific as possible here:

What I want to do is make a fine-tipped stylus for my iPad so that I can write and draw without an awkward clunky stylus that may as well be another finger.

I know there are fine-tipped styli out there, but I dislike all of them as they either do not work as advertised, scratch the screen, or are to flimsy.
But most importantly: I like making things.

The sensor array in the iPad is mutually capacitive. A grid of capacitors is laid out under the glass. A constant voltage is passed through one axis of the grid. The other axis waits and detects changes in the voltage. So to trip a sensor, an object such as a human finger or stubby capacitive stylus must be brought close enough to change the voltage of one of the capacitors with its local electric field. When that field covers a wide enough area, the device registers it as input and decides where the center point is. This is how it maintains accuracy while being so low-definition.

So to reiterate: how can I make a device that generates the same electric field as a human finger over a ~5mm radius from a much finer tip? It can be ugly, hooked up to wires, even grounded to human skin with a wrist strap. I don't care about form. Just function.


texts:
I came up with the following simple schematic in order to amplify the EMG signal and feed it to an arduino:

simulate this circuit – Schematic created using CircuitLab

The problem is that I monitor analog pin 6 of the arduino and it's always 0.


texts: Driving fan 4 pin with low frequency PWM

texts:
I currently using a 4pin fan in my project.

I need to drive the fan with a 120 Hz PWM signal. I read in all the documentation of the fan that the suitable PWM frequency is from 21 to 28 kHz.

I tested the fan using the 120Hz signal and it seems to work well.

Do you think that my configuration can be safe? Is there something that can go wrong driving the fan in that way?


texts:
I intend building a custom IP camera for home use, project goals are:

Videos are stored remotely in real time (storage somewhere else in home or cloud server)
Live steaming from internet
Video data transferred securely over wifi (recordings include footage of inside the house)
Resolution 720p@1fps
Cost efficient (in terms of cost price and power consumption)

I'm looking at the Raspberry PI and SMT32f4 boards, but I have not found any clear answer of its viability, and only the boards already cost more than a commercial IP camera.

How do I determine the minimal hardware requirements(what hardware do I choose)? Does anyone have any experience with a similar project? I've done days of research and I'm at the point of pulling my hairs out. Any help is highly appreciated!


texts: Help with power-loss protection using capacitor

texts:
I designing a circuit will store log data to an SD card. The information will be coming form a parent circuit that this one plugs into. The parent circuit will supply 5V to my daughter card. The daughter card uses an MCU that operates at 3.3V so I am just using a couple of diodes to step down the voltage from 5V.

MY CHALLENGE IS: In the event of a power failure, I want the MCU on my daughter card to be able to sense the main power loss and then immediately flush the data from it's RAM to the SD card and then go idle before it shuts down. When writing to an SD card you can cause corruption if you lose power in the middle of a write procedure.

I am thinking about using a big capacitor to just buffer the power for a bit. I know there are some MCU Supervisor IC's out there that would do a really nice job but they are intended for cases where you need to maintain power for days. I just need a second or two at the most. But I do have to be careful about not letting the MCU "flicker" on and off as the capacitor power decreases below the IC's threshold. Does anyone have a schematic or can offer any suggestions of how I should go about this?

Here is what I have so far... (the .5F cap is my power back-up capacitor)


texts: Put RS485 microcontroller and transceiver to sleep and wake it up on incoming data

texts:
I have to do a network of devices based on MCU.
This network in a RS485 and the device is battery powered.

For save the battery I put the MCU into sleep mode and I want to wake the MCU up, when there's a RS485 communication to process the incoming packets and return in sleep mode.

I read the feature of many RS485 transceivers and I saw that they use a quiestent current of 1 mA.

I saw also that is possible put in sleep mode some kind of transceiver.

Is possible to put the transceiver in sleep mode and wake it up with the MCU when the RS485 line become busy?

Which kind of IC I have to use?


texts: About nonlinearity of PGA (Programmable Gain Amplifier)

texts: I find there are at least two methods to specify the nonlinearity of a programmable gain amplifier (PGA). For PGA204, it is given as '% of FSR', but for PGA280, it was given as 'ppm'. It seems the latter are more common. Then why use '% of FSR'? Are there some reason to specify it like this? What does 'FSR' refer to, input or output?


texts: If an UART is receiving data continuously, can I also send data using the same UART while receiving data at the same time?


texts: How to adjust this circuit to use N-Mosfet instead of P-Mosfet

texts:
Background information

(You can skip this part if you just want to answer the question by heading straight to the "The Question" paragraph)

I'm a hobbyist in electronics and a professional programmer. I want to learn more about electronics and I decided to design a simple switching mode power supply (see the circuit below), solely for the purpose of gaining more hands on experience and feeling with electronic components. Of course I could buy a SMPS IC that does the magic for me, but I wouldn't learn much from it that way. I've a 2-channel oscilloscope by my side (up to 1MHz) to facilitate me on my journey.

The circuit is working, although not optimal. But good enough for the fun of it. By my surprise, the signal to the gate of the P-Mosfet shows actually a block wave! When I replace the 10K restistors in the Driver Circuit with significantly lower values, the gate of the P-mosefet isn't driven with a block wave anymore. So I guess its due to the limited switching speed of the driver circuit (consisting of Q1, Q2 and Q3).

L1 is meant to limit the peak currents when P-Mosfet is conducting. C4 is meant as the buffer cap when powering the load. L1 is seemingly doing its job as the voltage at C4 (and the load) only reaches ½ of 16Vdc. So it seems the 555 @ ~50DC is a limited factor here. But thats alright, as long as I know where the 8V limit on the load comes from! In this circuit I could possible not use the 555, and have no Duty Cycle, but still have a 'working' regulated SMPS (may I even call it like that?). And I should replace the LM2904 with a comparator instead of an OP AMP. But does it really matter as the switching speed is already delayed by Q1, Q2 and Q3?

Blue is the signal on the gate of the P-Mosfet. Yellow is the voltage on the load.
The circuit was driving a small universal motor when this screenshot was taken. As you can see the ripple on the voltage on the load is quiet high (1.04Vpeak-peak) but the P-Mosfet (Q4)'s gate is driven with quiet a nice regular block wave.

 Blue line is the Gate of the P-Mosfet. The Gate is driven on/off in 1.2uS. Is that fast enough? THe yellow line is the voltage on the load. Oh and yes, not to be forgotten: after ~10 minutes of action the passive heat sink (exactly this type: http://nl.farnell.com/jsp/search/productdetail.jsp?SKU=4621311) attached to Q4 doesn't seem to have become any warmer at all while the voltage on the load was < 1 Volt. So 'dropping' ~15Vdc from the PSU to the load! So the lowering of the voltage on the load is really done by the switching and not by the resistance in Q4.

The question

How can I replace the P-mosfet with an N-mosfet in this circuit? I was thinking about adding a charge pump up to 30Vdc or so (something like http://i210.photobucket.com/albums/bb292/frequencycentral/555ChargePump80-1.jpg) with a 14.5volt Zener diode to drive the N-mosfet gate. I tried, but when I connected the 30Vdc to the gate, it collapsed to the upper rail voltage of ~16Vdc, even while the voltage at the N-mosfet's drain was ~15Vdc (maxed out). I still do not understand how the Mosfet was conducting as the Vgs was now less than two volts or so!


texts: Can I use a silicon controlled rectifier to discharge a capacitor? If yes, can you provide a diagram of how this would work in, say, a coil gun?


texts: Back up power supply for microcontroller and servos

texts:
I currently have a simple circuit which lets me control a servo using an arduino and have everything working, but I need the servo to go back to the default position in the event of a power failure, so I need a backup power supply for both an arduino nano (~5V) and the servo (~7.5V) for >=1 second
(It takes about a second for the servos to rotate 180 degrees back to default, so longer would be better, but it's not crucial that they go totally back to default)

The circuit is currently supplied by 24VDC (powering other things too), into a DC Step down converter to ~7.5V (Variable) to supply the servos and a second DC Step down converter to 5V (For the arduino).

simulate this circuit – Schematic created using CircuitLab

I'm thinking of going with supercapacitors in parallel with the 7.5V output, but i'm not sure how to include this exactly, how to balance them and if this is even necessary, and what kind of diode to include and where.

I've included my best guess.

I also need to include a way for the Arduino to know that the 24V source has turned off so that it knows when to reset the servo. For that I was planning on using an optocoupler between the 24VDC source and an arduino input but there is probably a much simpler/cheaper/better way.


texts: Dielectric (HI-Pot Test) Failure on Ethernet Port

texts:
We have failure on Dielectric test between Power wire to Ethernet Port. Failure was observed near 1.7kV. After test Ethernet port was damaged (Phy chip).

See attached Case 1 :- Where we apply High voltage between Power to Ethernet terminal. (see below case 1 setup image)

The SMPS we used is rated for 3.75VAC for 1 Min.
https://recom-power.com/pdf/Powerline_AC-DC/RAC10-C_277.pdf

Test video can be seen on below link.
https://we.tl/t-ZcJQAZtdNo

We also tested CASE 2:- where we apply high voltage up to 3kV AC for 1 min between power wire and Secondary Ground. after test unit was ok, no failure observed in this case. (see below case 2 setup image)

Question is when SMPS is rated till 3.75kVAC and test pass with CASE 2 setup than why its failure on CASE 1? Is it because of Ethernet transformer or something else? Where is it getting its path from?

Circuit is below


texts:
I am trying to understand what is the correct way of doing such application, so please do not ask for complete code because each component is working fine on its own. I am struggling in the way of making them work together. I do not know the correct approach yet.

I have three vhdl modules adc, ft2232 usb and fifo modules.

ADC module is getting samples over spi. Its sample rate is 500KHz.
USB module is ft2232h usb implementation where it is achieving around 2 megabytes transfer to pc.
Fifo module works as well where i can read and write data on it. I used this code below also tried xilinx's ip core both works.
Fifo code

I want to buffer adc samples directly to pc. But what confuses me is that fifo cannot serve to both adc's write and usb's read operations simultaneously. Since they are two seperate processes they might try to use fifo at the same time. Should i define a busy flag to wait during read or write operations.

I appreciate any help.


texts: Regarding Phase Angle Of a Fourier Transform

texts:
Please tell me what would be the phase angle diagram of Fourier transform

$$X(e^{jw})=\frac{1}{1-ae^{-jw}}$$

and how?


texts: Inverting op amp used with low frequency oscillator

texts:
I am designing a low frequency oscillator. An image of the schematic is below.

The oscillator part works fine. My intention is to scale the triangle wave at the output of U1 to +/-2.5 V by using U4. In the simulation this works correctly; the gain of U4 is of course -(68/100) = -0.68, or 0.68. In the simulation the triangle wave at the output of U4 is approx. +/- 2.5 V.

However, on the breadboard, Vtri at the output of U4 appears as a triangle wave equal in magnitude to its original wave. If I increase or decrease R9 it has no effect on the gain. I am not sure why. Perhaps the way I am trying to couple the output of U1 to U4 is not working the way I want? I also tried AC coupling the output of U1 to a noninverting amp, but this didn't work either.

I thought maybe somehow my 074 was damaged; I popped a 324 into its place and I got the same result. I am not sure why.

Can anyone suggest a way for me to amplify the output of U1 by 0.68, preferably with my 074 op amp?

Thank you.


texts: Why does the MAX30102 only work on a finger?

texts:
I am using a MAX30102 sensor with Sparkfun library for heart rate monitoring. It does work for a finger, but when the sensor is mounted on chest I am not getting a reading.

Why is that?


texts:
I am looking for a COTS countdown timer - preferably with programmable or preset, short countdown times - that will turn 110v OFF when timer is initiated, and back ON when the countdown ends.
I know I could build this with the proper relays, but I want something safe and easy, not a circuit-building project.
(I feed my fish with filter and aerator OFF but I keep forgetting to plug them back in when feeding is done.)
Thanks!


texts: Bad audio quality from two stage audio amplifier

texts:
I'm trying to drive a speaker from the 47u capacitor , it seemed to be working fine and the volume scales well but when it comes to human voice , it adds this weird bathroom effect with some poor performance when it comes to high frequency/low volume . There is also some distortion

It weirdly enough , works fine when it comes to instruments (that or I have pleb ears )

What could be the cause of this ? Sorry if there's any glaring mistake but this has been bugging me for quite some time .

Edit : I'm audio I'm playing is from my phone's mp3 jack.


texts:
I would like to switch a 350mA LED with a transistor. Switching is done by a 5V microcontroller and the main voltage is provided by a 24V power supply. To play around and see what works I used Yenka, so I'll use screenshots from that.

As I understand this is the conventional way to do such a thing - assuming that the LED voltage drop is ~4V, it's connected to the collector along with a resistor to eat up the excess voltage:

However I noticed that in the simulation connecting the LED straight to the 24V supply works as well if we use more resistance to the base:

Shouldn't connecting a 4V LED straight to a 24V supply damage the LED, or do I have some fundamental misunderstanding about this? All answers, thoughts and tips are appreciated, I'm still learning the basics here.

Tl;dr version: will the circuit in the second image work, or is this evil program trying to make me burn my fancy LEDS?


texts: Oscillation on PWM output microcontroller

texts:
I was trying to create a 20 kHz PWM signal with a PIC16F684 microcontroller.
I noticed some oscillation on the single when I hook my scope on the PWM output of de microcontroller (see image below).

This oscillation only appears when I use a 20 MHz crystal instead of the internal oscillator of the microcontroller. The internal oscillater operates at 8 MHz.

From where is this oscillation coming and what can be done to avoid it?

Many thanks in advance.

ADDED:
I have attached a schematic, I am measuring between the ground and pin 5.


texts: Need to close or open a circuit (and keep it that way) with magnet

texts:
I need to build a circuit that closes when it detects the passing of a magnetic card.
It should open again when the card passes again.

So I need a simple magnetic reed (like this one). And some kind of switch component that closes when it detects a current pulse from the magnetic reed (right?).

Can someone tell me what kind of component I should use?


texts: Power issue on connecting controller to FTDI programmer

texts:
Hi,
I have connected my controller (ATMEGA2560) input to 5V power supply. At the VCC terminal 5V is shown. The VCC, TX,RX, RESET and GND pins are connected to a FTDI programmer port as shown in figure.

The diode D(SS34A) is connected in series of the VCC line from controller to FTDI programmer port, so that it forms a reverse bias from controller to the FTDI programmer. The 0.1uF capacitor is connected only to supply a stable voltage to the controller.

But, when I connect my FTDI programmer to the FTDI programmer port with other end of the programmer not connected to the USB terminal, I found 5V at the VCC terminal of the FTDI programmer, which should not happen.

So, How the 5V is coming in the VCC terminal of the FTDI port at this condition ?


texts: Why should the \$\frac{e_5}{2}=rl_5(I_5)\$,not \$e_5=rl_5(I_5)\$ in the DC voltage drop?

texts:
I read something about the DC voltage drop, but there is something confusing me.

I suppose \$e_1\$ is the voltage drop between \$A\$ and \$1\$, and \$e_2\$ is the voltage drop between \$1\$ and \$2\$. \$r\$ the resistance (\$Ω\$/distance)

The thing confusing me is that why should the \$\frac{e_5}{2}=rl_5(I_5)\$, not \$e_5=rl_5(I_5)\$?

Because I think \$V=IR\$, and \$I\$ is \$I_5\$,\$R=rl_5\$,so \$e_5=rl_5(I_5)\$ makes sense, I don't know why should divide the \$e\$ by \$2\$?

I think the reason for dividing by 2 may like the formula in this website,but this website doesn't tell me why we should divide e by 2 either:

https://energypedia.info/wiki/Permissible_Voltage_Drop


texts: I'm trying to make a CNC machine out of 2 dvd drive stepper motors. One of my stepper motors is completely normal and as seen in every video I've seen on the topic. The other looks like this (see pictures). The laser diode assembly moves on some gears connected to a motor which is connected to a board. the board has 4 contacts but according to my multimeter, only one pair is connected. Is this a stepper motor? Also, how do I get this to work with my build?


texts: How to increase the read range of an active NFC tag?

texts: I want to read a NFC tag at a distance of 1m from my NFC enabled smartphone. Is it possible to do so by enhancing the antenna of the NFC tag (not the one on the phone). Size of the NFC tag is not an issue, and so we can use a bigger/complex antenna with power supply through battery (active tags). Is it possible?


texts: Why hFE(DC gain) shown on multimeter isn't equal to the datasheed hFE?

texts: I have a tip122 and discovered my multimeter uses Vce=2,8V DC and Ib=10uA for its hFE test. When I insert the transistor on the terminals for hFE test, the gain on the multimeter alternates between 1 and 2 when by datasheet information it should be 1000. Anyone knows why?


texts: What is the difference between ram and registers in 8051 vs arm v7?

texts: Recently i am confused between the difference between ram and cpu registers.I have studied 8051 arch. and in that we had addressing for cpu registers in ram level (e.g. the adddress for R0 register in  bank 0 is 00h ). But in arm architecture i am confused whether cpu registers have address like that in 8051 or are they addressed using only their name like R0,R1 e.t.c.


texts: Explanation of sensor sensitivity in unit/hertz

texts:
i found an overview of different magnetic field sensors sensitivity in a paper. I was wondering why the sensitivity is given in units of T/Hertz^-1/2.

Is it possible to determine the minimum detectable magnetic field at 10KHz for the MTJ sensor as a quantific value?

How can I determine an spectrum like this when i only have a sensor and a oscillioscop?


texts:
simulate this circuit – Schematic created using CircuitLab

The problem is to find the node voltage at e2 (I added the current lables and directions)  After getting it wrong, and seeing the correct answer I know that the correct equation must be

$$
\frac{e2-5}{3} + \frac{e2}{5} - 3 = 0
$$

However, I can't see how I would arrive at the above without having known the answer (i.e I'm bound to get the next one wrong too)

So this is how I tried to work it out.  I defined the currents into the node as positive, giving

$$
i1 - i2 + i3 = 0
$$
Where
$$
i1 = \frac{e2-e1}{R1} = \frac{e2-5}{3}
$$
$$
i2 = \frac{e2-e3}{R2} = \frac{e2}{5}
$$
$$
i3 = I = 3
$$
So
$$
\frac{e2-5}{3} -  \frac{e2}{5} + 3 = 0
$$

Which, with a couple of incorrect signs, gives the wrong answer.

What is wrong with my logic?


texts:
I have a 1258MHz transmitter running at 1W output power.  I want to switch it between two antennas while it's in the field.

Can I use a pair of any standard MOSFETs for this, assuming the power dissipation of the FET is adhered to?  If not, what do I look for in the datasheet to know that a particular FET is appropriate?

If a FET isn't appropriate, what kind of device would be?  I'm not oscillating the thing at anything more than 1hz (at worst!), so I don't think I need the special "RF" components.


texts: Is it 'ok' to have electrostatic sensitive components on an end-user, exposed PCB design?

texts:
I'm currently working on an electronics project. This project is intended to be portable and battery powered. I'm curious about whether or not I should use certain components on my PCB do being too ESD sensitive.

For example, I'm currently trying to use this clock on my design. After ordering it, I notice that it came packaged with a warning to only open/handle at an electrostatic-free workstation.

Now obviously I could oblige to this, however, my end design is an exposed PCB in which a user may accidentally touch. The end user (colleagues of mine, not external customers) will be handling this device to press pushbuttons, look at lights, etc. Furthermore, my design only covers the electronic portion thus I can't create an enclosure to protect during operation. That's the end user's duty.

So I'm somewhat concerned as to whether or not I should proceed with using the previously referenced IC. I'm also not sure as to what kind of ESD protection is used on portable electronics that may allow me to use the chip.

So my questions:

Is there ever a point in which a certain component shouldn't be selected on an open PCB design because it's too ESD sensitive? Or can you just bypass this with appropriate ESD protection?

What kind of ESD proection is used for portable electronics?


texts: How can I connect a shunt resistor whose output voltage range is 5V to STM32F103 whose ADC conversion range is 3.6V?

texts: I am new to STM32F103. I need to connect a shunt current measurement sensor whose output voltage range is 5V to the ADC pin of STM32F103. But the ADC conversion range of STM32 is 3.6V. What is the solution so that I can get proper output from the current sensor?


texts: How do I calculate Watts for a dual rail power supply?

texts:
If I have a 5V power supply powering a circuit which is connected to 0V, to calculate power usage I would take the total current in Amps and multiply by 5V.

However, my current circuit uses -12V, +12V (for an op-amp) and 5V, 0V for the rest of the circuit. How can I calculate power consumption?


texts: Differential gain of amplifier with current mirror

texts:
Consider this pdf document, pages 58-59-60. It is a differential amplifier with a current mirror as active load.

According to that document, if I take the unbalanced output in the right-hand branch (drain of M2), the transconductance gain is \$ g_m \$, while if I take the unbalanced output in the left-hand branch (drain of M1), the transconductance gain is \$ g_m / 2 \$. It is because the current of M2 and the current of the mirror are both entering the M2 drain, as regards the differential mode signal.

Let \$ v_{o1} \$ and \$ v_{o2} \$ be respectively the M1 drain voltage and the M2 drain voltage.

If \$ R_{out} \$ is the output resistance of this amplifier looking into both \$ v_{o1} \$ and \$ v_{o2} \$, the voltage differential gain is different in the two nodes, being \$ A'_{v,dm} = g_m R_{out} / 2 \$ for \$ v_{o1} \$ and \$ A''_{v,dm} = g_m R_{out} \$ for \$ v_{o2} \$.

First question: Wasn't this circuit perfectly symmetrical?

Moreover: the outputs can be written as

$$v_{o1} = A_{v,cm} v_{icm} + A_{v,dm} \displaystyle \frac{v_{idm}}{2}$$

$$v_{o2} = A_{v,cm} v_{icm} - A_{v,dm} \displaystyle \frac{v_{idm}}{2}$$

where the two input were

$$v_{i1} = v_{icm} + \displaystyle \frac{v_{idm}}{2}$$
$$v_{i2} = v_{icm} - \displaystyle \frac{v_{idm}}{2}$$

(\$ v_{icm} \$ is the common-mode signal component; \$ v_{idm} \$ is the differential-mode signal component)

Second question: What does happen if \$ A_{v,dm} \$ is different between the two output nodes? Should I consider \$ v_{o1} - v_{o2} = (A'_{v,dm} + A''_{v,dm}) v_{icm} \$?


texts: I am designing a phase control circuit to control a Single phase AC induction motor. In the circuit 50K potentiometer is used in series with 10K resistor to control the the phase angle of the signal. But my need is to use 10K potentiometer. So I decided to use 10K pot with 50K resistor. But I have a doubt that interchanging a value of pot and resistor might affect the performance of the circuit.Please clarify this doubt. Any other suggestion are welcome. Thank you. Sorry for crappy images.


texts:
I am implementing a DDR3 interface on a PCB and I have a question regarding the termination of address/control/command/clk traces.

I have series terminations for all the required traces mentioned above, my question is whether or not the traces going to these terminations require length matching or should they just be kept as short as possible and left as uneven termination stubs? To me it makes sense to keep them as short as possible even if lengths aren't matched well, but I wanted some other opinions on the matter :)

Thanks!


texts: Blinking LED on ATMEGA168. Error rc=-1. AVRDUDE

texts:
I apologise in advance. This is my first project. I keep getting this error

avrdude: error: programm enable: target doesn't answer. 1
avrdude: initialization failed, rc=-1
     Double check connections and try again, or use -F to override
     this check.

when i enter the command

 avrdude -p m168p -c usbasp

This has something to do with how I have connected the 6-pin to the AVR.
I have included pictures but I have tried and tried again to no avail! has anyone got any suggestions?

I am using a USBasp. There is a red light on my USbasp when i plug it in. Should it be green? I do not know.

This is my breadboard.


texts: Can specific microcontrollers be used as secure element?

texts: After learning that there can be set a security bit to prevent reading from Arduino microcontroller, thought about if could it be used as a secure element kinda thing? Storing all kinds of digital signatures, passwords and signing with them using a pin like Ledger Nano or other hardware wallets etc.


texts: Buck Converter has minimum output current

texts:
I was looking online for a buck converter and I came across this on eBay:
https://www.ebay.co.uk/itm/DC-DC-5-40V-to-3-3V-5V-9V-12V-24V-Buck-Step-Down-Converter-Volt-Linear-Regulator/263325140035?hash=item3d4f66c443:g:hwgAAOSwJyhdg0ay

What does it mean by a 1.5A minimum output current? Can it not handle a no-load condition?


texts:
I am busy designing a custom board based on Arduino's pro mini
design.

In the official design, they have a MIC5205 voltage regulator supplying a constant 5V to the ATMEGA328 chip. However it is also possible to feed in 5V directly to the chip if you so wish, but when you do so, you are supplying 5V to the output of the MIC5205 chip.

In my design, I want to replace the MIC5205 chip with a LM7805 voltage regulator. But based on a bit of research it seems like you cannot supply 5V to the output of the LM780; based on a quick test, when you do so with 5V the chip doesn't seem to draw any current.

After going through each datasheet (MIC5205 and LM7805) I couldn't find any information about the chips' ability to withstand voltage applied to the output pins.

My question is finally:

Can the MIC5205 actually handle voltage applied to its output?
Is it bad to apply voltage to the output of the LM7805?
How can I tell from looking at the datasheet if a chip can handle voltage applied to its output?


texts: How to obtain a neutral point in delta connection?

texts:
If I want to connect a load from phase to neutral in delta, how do I achieve it? So far the closest thing I could think of is convert the delta to star. I may be wrong, please guide me to get a solution.
Just for info, I have a 3 phase 415 V PMG generator and would like to connect it to a single phase 240 V load.


texts: From what used/junk equipment can I salvage solenoids from?

texts:
I have a few old 24V solenoids which I've used for years for random (often Halloween-related) projects. I can't recall where I got them. I'd like to get some more, but new ones can be rather high priced.

I sometimes buy junk printers to salvage stepper motors, or dismantle speaker cabinets to acquire a driver.

What old equipment commonly includes solenoids that I can salvage (push or pull type, 12-24 V)? Pinball machines seem to be the most-cited, but I never see those at the thrift store.


texts: Can I put a 250 mA fuse in replacement of a 160 mA fuse?

texts: I have a guitar amp that works on 110 V and someone accidentally plugged it in a 220 V socket. I want to replace the fuse (160 mA) but my local store's lowest is a 250 mA. Can I actually use this? Thanks!


texts: I have a peltier element rated at 15.4V, 6A, and 60 watts that I got from China and has no datasheet to be found. When I drive it with a 12 volt power supply, I can get up to about 5.5 amps giving a power output of over 60 watts. Is this an issue? Maybe the specs I have are misleading, but they don't make very much sense to me. is going over the rated power okay if I keep it cool? I have a heatsink on the hot side and it is not even noticeably warm. Is driving it over the rated power going to hurt it? It doesn't make sense to me that the given current and voltage levels would yield so much more power than it is rated for. It makes me think the 60 watts is just a suggestion. It says TEC1-12706 on it, but as far as I can tell, that is not unique to the particular product.


texts: STM Nucleo-F722ZE UART weirdness when setting the baud rate (it needs to be set 3 times larger)

texts:
For the past days I've been trying to communicate via UART between an Arduino and an STM32 Nucleo F722ZE board. After much troubleshooting with the oscilloscope I realized that when I set a baud rate in the Cube IDE the actual baud rate is 3 times lower. I assume that this is because of bad clock configuration but I couldn't find a reference anywhere to this.
Here is my current clock configuration inside the Cube IDE.
Did anyone encounter this before? Have I missed a part of the documentation about it? I would be grateful if someone has an explanation or a link towards the official docs detailing this. Thank you very much.

Here is the baud rate settings for communicating with a device at 9600. I have to set it to 3 * 9600 = 28800.


texts: Pspice Common Emitter Schematic Missing Values

texts: I am doing some homework for universiy and PSpice keeps saying that there is some missing values.I cant seem to find a solution in my books so I though that i might share my issue with you and understand why that happens.Here is the schematic


texts: Solar cell outputs full voltage but barely any amps

texts:
So I've asked a similar question in the past, but I'm still curious about something.

On a fully sunny day, the solar panel tops out at 5.5v @ 260 mA. On overcast or cloudy days, the voltage stays just about the same, but the current drops to 50 mA.

Why does it do this? Does the intensity of the UV rays directly affect the amount of current in the solar panel? If so, why doesn't the voltage drop as drastically? Any way around this besides a new panel?


texts: What easily acquirable material changes its resistance when heated?

texts: I'm trying to build a Resistance Thermometer that varies current/voltage output when  heated. It has to be DYI, I don't want to buy anything done, only something like a light bulb, and this has to be easily changed, as the ideal temperature range I want to provide to it is 0-100 oC. I understand all resistors change their resistance with temperature, but I'm looking for something that changes it a lot more than the regular hardware store resistor.


texts: How to amplify without contact a 10-20Khz square signal?

texts:
I would like to amplify a square signal 50% PWM on a live wire, the wire carry also  a sine wave 60Hz at 120VAC.

The square signal will be only present a a few milliseconds after the zero cross.

Like in this example, but instead of 120kHz I will be using 10 to 20kHz:

Since they are two signals on the wire; a sine wave at 60hz and 120V, and a square wave 50pwm, on the zero crossing.

How discriminate the sinewave and amplify just the square wave?.

My goal is to make something like a non contact detector "wand".

But they collect the 60Hz signal for the amplification.


texts: Why is neutral wire connected to ground at the transformer?

texts:
I understand the use of ground wire at the home appliances but why is the neutral wire connected to ground at the transformer? Why doesn't the neutral wire go back to the power generation plants.
I found this image online.


texts: PIC16F884 keeps resetting even though WDT should be off

texts:
I just bought a PIC16F884 and put a simple C program on it using MPLAB:

// CONFIG1
#pragma config FOSC = INTRC_NOCLKOUT// Oscillator Selection bits (INTOSCIO oscillator: I/O function on RA6/OSC2/CLKOUT pin, I/O function on RA7/OSC1/CLKIN)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled and can be enabled by SWDTEN bit of the WDTCON register)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = OFF      // RE3/MCLR pin function select bit (RE3/MCLR pin function is digital input, MCLR internally tied to VDD)
#pragma config CP = OFF         // Code Protection bit (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Code Protection bit (Data memory code protection is disabled)
#pragma config BOREN = OFF      // Brown Out Reset Selection bits (BOR disabled)
#pragma config IESO = OFF       // Internal External Switchover bit (Internal/External Switchover mode is disabled)
#pragma config FCMEN = OFF      // Fail-Safe Clock Monitor Enabled bit (Fail-Safe Clock Monitor is disabled)
#pragma config LVP = ON         // Low Voltage Programming Enable bit (RB3/PGM pin has PGM function, low voltage programming enabled)

// CONFIG2
#pragma config BOR4V = BOR40V   // Brown-out Reset Selection bit (Brown-out Reset set to 4.0V)
#pragma config WRT = OFF        // Flash Program Memory Self Write Enable bits (Write protection off)

#include <xc.h>
#include <stdint.h>

void main(void)
{
    SWDTEN = 0;
    TRISB = 0;
    PORTB = 0;
    // _delay(100000);
    RB1 = 1;

    for (;;)
    {
    }
}

On my board I only connect 5V to pin 11 and ground to pin 12. I was certain the WDT should be off because of the pragma and the SWDTEN = 0;. This code seems to work, as it does bring RB1 to logic high. However, when I remove the comment from the _delay call, the RB1 sits at logic low. From this I assumed that the device is resetting, but I don't know why. The issue persists even when I call _delaywdt instead of _delay. What could be causing the reset? Is it a reset at all, or did I forget to do something/did something incorrectly?


texts:
I was selecting a DAC for HART network and in the process I came across two terminology.

12-/16-Bit, Serial Input, 4 mA to 20 mA, Current Source DAC AD5420 and
16-Bit, Serial Input,Loop-Powered, 4 mA to 20 mA DAC AD5421

As per my understanding, the difference between the two terminology is, the Loop-Powered, 4 mA to 20 mA DAC will be powered from the input signal itself whereas for 4 mA to 20 mA need to provide supply as well as like other IC, correct me if i am wrong.

My question here is what topology will make the Looped power devices to get the supply from the Input signal itself and what will be the behavior of these signals?


texts: Static electricity when touching any metal after power down

texts:
I have a PC connected to a couple of devices via a serial port.

The item labelled "COM" is a simple manual serial port switcher that requires no power.

The item labelled "Rad" is a radio module whose data is sent to and from the serial port.
I use this for testing my main circuit which is the other object shown. It as well has a radio module.

The mini long rectangle is a power bar connected directly to a wall socket and the squares above are 6VDC adapters to power my circuits. The PC uses power directly from the bar.

Both my circuits also use LM2940 voltage regulators with 10uF cap at input and 22uF cap at output.

When I initially turn everything on, it seems that everything runs normally but eventually the radio signal starts to run poor (receiver gets no data, and I could guess static build-up). After, I manually turn everything off by the flip of the power switch on the power bar (this is a basic power bar).

I go and touch a metal tab on a regulator on my own circuit and notice what I perceive to be static electricity. I describe it as a tingling effect until I remove my finger.

Now when I tried the PC by itself without the rest of the items pictured connected, it seems the PC is a major factor because when I turned it off and tried to touch the case I also felt static electricity.

So assuming the PC is the biggest culprit, is there any sort of circuitry that I can build as a bridge between the PC serial port connector and the serial cable so that my circuits don't act funny due to residue static?

And do I also need circuitry between the 6V output from the wall wart and the voltage regulator input to minimize the chance of static?


texts: When hair clippers or similar appliances are rated at, for example, 10W, does that mean 10W per hour or second? I'm trying to determine power of various hair clippers.


texts: Turn on an LED when power is lost with a relay

texts:
A friend of mine has just finished his race car but is having fan issues. What I want to help him do is setup an LED that turns on when the fans have lost power. Often the fuse blows.

I would assume I can tap off the 12V supply that is after the fuse to send to the relay but how would you wire it up..?


texts: Need help with OpAmp and FET choice for a VCVS

texts:
I want to build a voltage controlled voltage source that will supply power to a resistive load (\$1.67\,\Omega\$, \$\approx\$ \$7\,\mathrm{A}\$ @ \$12\,\mathrm{V}\$). The load's dissipation will be calculated from current and voltage drop measurements by a control system that adjusts the VCVS's voltage with a DAC output (\$V_2\$).

I adapted a circuit I found online (see the first picture here) to my application:

The original N-channel FET got replaced by a P-channel FET because I can get closer to V1 with that. I picked the IRFP9140 for maximum current, low \$R_{DS,on}\$, high power rating and easy to use case - I can attach it to a heat sink. As the control voltage sweeps from \$0\$ to \$5\,\mathrm{V}\$, the maximum expected dissipation in Q1 is about \$22\,\mathrm{W}\$ for \$V_2 = 2.5\,\mathrm{V}\$.

The output voltage is scaled down to the DAC range by R2 and R3 and fed into the OpAmp, which outputs Q1's gate volgate. So I had to pick an OpAmp and ended up with the LT1218. I basically went through the list of available models in LTspice and this one fit my supply voltage (\$V_1 =+12\,\mathrm{V}\$) and has rail-to-rail inputs and outputs. There are probably better choices.

I'm not sure if R4 is necessary. I've seen it in many circuits and people seem to include it in order to limit the OpAmp output current.

Does this circuit look reasonable given that

I don't need a highly precise output (this is part of a control system that adjusts \$V_2\$ to its needs);
efficiency doesn't matter;
size doesn't matter, it may be a large PCB;
same for cooling, including adding a fan;
I need several of these;
the circuit should be easy to build and test;
I can replace R1 with a larger value when the desired maximum dissipation in R1 is lower than in the circuit shown.

This is my first attempt at using an OpAmp in a real circuit, and I've also never used a transistor for something other than switching a load on and off. I'm very happy about advice regarding both components.

Edit

As suggested in the comments, I simulated a step in VC (V2 in the picture above) from 0 to 3 V and the result is rather disappointing:

The result:

So first of all, the output voltage needs some time until it rises to a value limited by Q1's \$R_{DS,on}\$ and then falls down to roughly the desired value (\$12*3/5=7.2\,\mathrm{V}\$), but swings. The initial overshoot might not really be a problem in the real application; what concerns me more is the fact that I don't know why that happens.

The plant is too slow for the OpAmp, so I'm now basically looking for a way to make it appear faster?

Edit 2

Adding the suggested capacitor between the OpAmp's output and negative input as well as a resistor in the control voltage input was very effective.

The output settles after about 150 µs:

Edit 3: Other OpAmps I've simulated

"swings": I couldn't get VO to settle at the desired voltage, even with different values for R4, R5 and C2.

LT1636: swings
LT1637: output settles (transient simulation), but DC sweep simulation won't finish. A very slow transient simulation for a 5 second period sawtooth on V2 shows the desired behavior, though. I'm not sure what that means. Cheaper than LT1218.
LT6003: swings
LT6013: output settles, but only follows \$V_2\$ for \$V_2 > 0.7\,\mathrm{V}\$ (this one doesn't have rail-to-rail inputs)
OP184: output settles (seems to work just as fine as the LT1218, but cheaper)
AD820A: output settles, and this part was easier to get in a DIP package. Also cheaper than the LT1218.

Edit 4: Seems to work

I've build the circuit with an IRFP9140N and an AD820A, with all resistors and capacitors as shown in the last circuit diagram, and it seems to work as desired.


texts: Will a 42000mah portable power bank charge an electric bike battery?

texts:
The electric bike I have has a 48v , 15.4ah battery. The charger for the bike reads a 120v-240v ac input , with a 2a output. The portable powerbank I am looking at is here,  https://www.amazon.com/dp/B06Y3NF7N2/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B06Y3NF7N2&pd_rd_wg=xjXEP&pd_rd_r=RPT4RMBVXEH370Z8P1AQ&pd_rd_w=vuzsq42k mah capacity with 250w/110v output
Would this be sufficient in charging this battery? Also if I were to keep the powerbank charging the battery in a bike mount , while the bike was in operation, would that cause any problems?

Below are pictures of the battery and the weight. It's a dinosaur.That is 12lbs. (I bought the bike from a previous owner who seems to have shorted the battery , because the bike does not seem to go as far as I would like it to , and the battery charges very fast , which lead me to the idea of a portable charger.)


texts: In CPFSK, suppose we transmit a continuous bit stream of 1, then for how long will the frequency go on increasing?

texts: I read something about phase memory but didn't get proper information. My specific doubt is, let's say phase memory is L, then after L '1s', will we have a phase discontinuity and will the frequency restart from the beginning?


texts: Use motherboard PWM to control non-PWM fans with MOSFET

texts:
So heres my problem: I have lots of fans but most of them have no PWM input. I want to drive clusters of 12v fans by PWM using only one signal.

In my spares i found a Fuji Electrics K2647 MOSFET.

I had some failed attempts trying to use it, but according to the internet it should work somehow. The PWM signal is coming from an Asus P8P67 motherboard (CPU fan channel). Its 18.75kHz (Measured in AC mode by a Fluke175) and ranges from 20% (1.074V avg) to 100% (5.056V avg) duty cycle. This whole circuit is placed inside a computer, so there are 12V, 5V and 3.3V rails available. Efficiency doesnt matter. There is also plenty of airflow. One fan pulls 400mA when blocked, but there will be 4 identical fans.

I need a circuit that can PWM control a 12V 1.6A load, can anyone design one?

EDIT: The motherboard hardware makes a duty cycle under 20% impossible (safety reasons perhaps?). Is there a way to add a gain/threshold to address this problem?

I found lots of people with a similar problem, but noone had a good solution.

FOLLOWUP: I built the circuit in the accepted answer using a FQP30N06L and it works great. I can recommend this as simple and cheap solution for fan controllers.


texts: BLDC Motor - supply current vs line to line current

texts:
I have a BLDC Motor. I am measuring the current coming from the DC power supply. How is the measured current related to the line to line current?

Thanks


texts: Why Linux doesn't get booted automatically only If I changed the BOOT.bin not the zImage, while in the first case it gets automatically booted

texts:
I have zynq board ( not the zedboard), it doesn't have all the peripherals of zedboard.
I am facing some problem while booting the linux on zynq with my new BOOT.bin.

When I used to put the sdcard in the zynq board which had three file BOOT, devicetree, zImage. Here BOOT is the old file which was already created by someone.
The linux automatically boots up and lots of printing happens on screen probably loading all linux drivers etc.
and I get a
"root@mcontroller" prompt. like this:

But Now I have made a new BOOT file from xilinx sdk.
Now I put three files in the sd card. BOOT , devicetree and zImage.
plugin the card in the zynboard.

I get
"Zynq-uboot>" prompt

Okay I captured the above image when i was using windows but I get the same prompt while using ubuntu also.

I do not understand the difference between the root@mcontroller and zynq-uboot prompt?
Why I am not getting the root@mcontroller when I change the BOOT bin file?


texts: output file formats for flashing in microcontrollers

texts: I have seen different micro controllers have different output file formats for flashing like 8051 has .hex file format, some have .out file format some have .s12 format and etc. What are the factors on which this output file format depends like the controller architecture or it is up to the micro controller manufacturer to choose the format he wants to flash into the controllers?


texts: Calculate peak input current of switch mode power supply

texts:
I have the following problem.

MY ATTEMPT

The switch-mode power supply looks like it's a boost converter. I found that the DC-transfer functions for the boost converter to be:

\$\frac{V_C}{V_{in}}=\frac{1}{1-d} \: \: \$ and \$\frac{I_L}{I_{out}}=\frac{1}{1-d} \: \: \$ where I presume that \$ d\$ is the duty cycle.

My idea was first to find \$d\$ with the first equation: \$d=-\frac{V_{in}}{V_C}+1=\frac{-2.7 \text{V}}{5 \text{V}}+1=0.46 \$

From here, we can plug \$ d\$ into the second equation and find \$I_L=\frac{I_{out}}{1-d}=\frac{2.3 \text{A}}{1-0.46}=4.256 \text{A}\$

And since the \$V_{in}\$ and the inductor is in series, we conclude that \$I_{in}=4.256 \text{A}\$.

But is what I have found the \$\underline{peak}\$ input current or something else? I am in doubt, because I don't use the information about the switching frequency at all.

I hope someone can help me with this.


texts: Is the meaning of a Decibel different when applied to Voltage vs Watts?

texts:
If I have an amplifier that provides +3dB, or an attenuator that provides -20dB, then how do I know if that applies to Voltage or power?

In other words, if I have a 0dBV signal and I run it though a +3dB amplifier, do I get 3dBV?

Similarly, if I have a 0dBm signal and it runs through +3dB amplifier, do I get a 3dBm signal?


texts: Should all resistances in a RC filter be regarded?

texts:
I am trying to build a wah pedal and need to use the rc low pass filter. I know that this is supposed to be very easy to understand, but I'm having difficulities.

The thing is, when I connect the resistor and capacitor in parallels, it is supposed to choose between the grounded capacitor and resistor according to their resistance values.

This however confuses me as it is actually supposed to choose from the resistances in between its whole way to the ground. I want to know if the resistances outside of the RC filter should be regarded or not.

I would not like to post this here but what I have found on the internet about this was very ambiguous.

By the way the type of fİlter I want to build is a resistor on the straight wire and a grounded capacitor branching after the resistance


texts: 12v to 5v 10A shielded USB car converter

texts:
There seem to be a load of 12v to 5v 3A USB converters around (the vast majority of which seem to be produced by a chinese OEM and then rebranded).

However I want to do something a little different......

Given the number of electronics devices you can add to cars these days (phones, tablets, GPS, cameras, etc....) I want to add a single USB converter circuit to my Jeep Wrangler which will allow me to run 12 USB ports to various points around the car.

Given the demands of the assorted devices can be anywhere from 0.3A up to 2A I want to try to use a single step down converter that handles say up to 12A, I'm looking at wiring this into a separate unused fuse point in my fusebox and then running the wiring invisibly as possible to each point, that way it keeps the interior of the car tidy.

I don't want to just plug in a converter to my 12V Cigar Lighter socket as I want to keep that free for other potential uses (no I don't smoke....but occasionally have had to use a compressor to pump up tyres or use a vacuum).

I want the step down adapter to be shielded to avoid creating noise (the 3A ones commonly available appear not to be shielded as a number of reviews have commented on radio interference once fitted) and also to account for and prevent any surge issues or ignition coil issues causing problems.

If no 'off the shelf' device exists how difficult would it be to breadbox one....while I'm not an electronics engineer I have a rudimentary to fair understanding or electrical issues (I understand capacitors, resistors etc...for example).

Shoot me down if what I'm asking for is too difficult, but I would have thought if 3A versions of the circuit exist it would likely not be too difficult to scale that to 12A and add the shielding?


texts: Using Spice/PSpice (Vishay optocoupler) models in LTSpice

texts:
I am trying to use the Vishay-provided spice models of the 6N137 high-speed optocoupler in LTSpice. (Source: http://www.vishay.com/optocouplers/list/product-84732/)

Both the "PSpice" model and the "Spice" model fail however.

With the "PSpice" model:

WARNING: Can't resolve .param dpwr=$g_dpwr
WARNING: Can't resolve .param dgnd=$g_dgnd
Fatal Error: Port(pin) count mismatch between the definition of subcircuit "and2" and instance: "xx1:u2"
The instance has more connection terminals than the definition.

With the "Spice" model:

Too few nodes: au1.a [1] [du1.a] adc_a

What do I need to do to make either of these work in LTSpice?


texts:
I am going through a timer programming for a micro controller and i was wondered about the term "full scale value" of a timer.What the full scale value of the timer exactly means.

Thanks,
Vijay.


texts:
I have a DAQ with many inputs that can measure within +-10 V, and I want to go up to +-30 V.
Using a resistor voltage divider could be an option, but this lowers the input impedance. I would prefer using an op-amp.

Is there any device that can divide all inputs with high impedance?

Like an array of 16 or more op-amps?

Or do I have to design it myself?


texts: ICSP, Debugging, UART and SPI on same pins, dsPIC30F4011

texts:
In my project I plan to use SPI1 module of the dsPIC30F4011 (datasheet pdf) micro-controller.
The pin-out makes pins 1 and 44 both PGC/PGD and serial COM pins for UART1 and also SPI1 modules. I can live with using UART2 module (which uses other pins), but there is only one SPI module on the device and I would like to debug the device as well. Is it possible to use the SPI module and debug? Doesn't seem like it.

Also, for programming the device I should isolate PGC/PGD when my PicKit3 is connected from application SPI devices. I don't think I can use simple resistors, because they would have to be high valued (10k minimum seems to be required) and SPI might not work properly. Can anyone confirm this? So my options are to do some switching with transistors or to use jumpers.


texts: OPAMP saturating when output is negative, simulation is OK

texts:
The schematics:

It should convert 0-3.3V input from the DAC to -4.1 + 4.1V (roughly)

The positive part works great, the negative output voltage saturates at -2.95V.

Is it ok? The simulation looks ok (and it is the expected behavior):

The part: https://www.st.com/content/st_com/en/products/amplifiers-and-comparators/operational-amplifiers-op-amps/standard-op-amps/tl084c.html#design-scroll


texts: Vds meaning in characteristic curve of a MOSFET

texts:
As I was wrapping up my design (which didn't include MOSFETs as switches tho, yet), I've realized I wanted to make it crystal clear for myself if I understand the thing correctly. Feels weird, but better ask (dumb - for my stage of development) question and be safe. Googling didn't help. It explains everything except for this specific thing.
It's about P-channel MOSFET as a load switch.
In the picture there is a regular characteristic curve for a P-Channel MOSFET. My question is about DRAIN-SOURCE voltage. The thing is, when the MOSFET conducts, drain-source voltage is effectively zero for currents under, say, 2A, due to tiny Rdson and associated voltage drop (Rdson ~ 50mOhm).
As far as I understand, drain-source voltage means "while MOSFET doesn't conduct". Because, as I said, when MOSFET is a conducting switch - a 0.050Ohm resistor - Vds is always around 0 anyway, unless it's 10A or something. Is my understanding of this correct?


texts: How do I simplify this circuit to find resistor voltage?

texts:
In my circuits class, I am presented with the following exercise.

simulate this circuit – Schematic created using CircuitLab

The problem is to find the voltage across resistors A and B.  The most likely solution (given the section) is to use simplification by analysis.  I tried to solve for B first.  My attempt included cutting the circuit in two parts (all of the resistors and just B), simplifying the part of the circuit that was not B, and then solving the resulting circuit.  This yielded a parallel circuit.

I know that is not supposed to yield a parallel circuit which implies a direct voltage path from the source to resistor B.

The book as has a similar example, but in this one the two ohm resistor is to the right of the 3 ohm resistor, making simplification vastly easier.  (I seem to have missed the lecture on this.)

Could someone be so kind as to point me in the right direction?


texts: Multiple pulses from single button press

texts:
I am working with a 74HC193 binary up/down counter, and am trying to set up a button to increment or decrement it. The procedure to increment a single step as I understand it is:

Set pin 4 high
Wait for change to propagate (30ns or more)
Set Pin 5 high
Wait again
Set both pins low again.

Since it is a button, I am not worried about speed in any way. I would be perfectly happy to have a 2ms pulse followed by a 1ms pulse 1ms later. In my research online, the most promising way to make a pulse is a monostable 555 circuit. I was thinking two of those wth different T values might work, but I can't tell from that page if I can put it on a delay. That seems like a fairly decent debouncing mechanism as well, but I would like a little more control, like a 2ms pulse but 500ms before another input is accepted. Is that possible?

If it is too hard to get two pulses with the proper timing, I suppose I could just hold the count down line high and pulse the count up line once, but that removes my ability to have an additional button to count down.


texts: Relationship of FFT Size, Sampling Rate and Buffer Size

texts:
I am asking this question because I want to make sure I understand the relationship of FFT length, the sampling rate and the buffer size. This question is with respect to the CMSIS DSP library, although I imagine it could be any FFT processing function.

Because of configuration constraints, my ADC is sampling at a rate of 10.68ksps. Then, I am taking the average of 4 samples to end up at a rate of 2.67kbps. I need resolution of 0.5Hz for signals from 100Hz to 300Hz. So here's the part I am missing - I do not understand what sample rate I need to scale to in order to properly conserve frequency information. For example, if I wanted to run a 1024 length FFT, what sample rate should I scale to, and what buffer size should I pass to the fft function?

I do have it working, but the bin information is not quite correct - for example, it is out by 1 bin at 100Hz, but 2 bins at 300Hz. I'm sure it's related to the odd sampling rate.
Do I need a sampling rate that is equal to the FFT length? And how does the buffer size passed in impact the operation?

Thank you for any answers.


texts:
On page 3 of the datasheet for the SN74LS597 IC, I have found the following diagram:

Notice that the flip-flops have some numbered inputs (1D and C1, 2D and C2, C3 and 3S/3R) and some simple inputs (S and R). What are these numbers for? Are they indications of synchronicity? Why different numbers?


texts:
I receieved this 4x4 keypad in an electronics kit, but don't know what the pins (it has 2x5 pins), are, and can't seem to find a data sheet for it.

Any info or help is appreciated!


texts: Potential problems with paralleling a jumbo battery to iphone internal battery?

texts:
Recently I happen to replace a new iPhone 4 replacement battery, with a little bit of peel down of the battery, I saw there is a bare lithium battery unit with a PCB battery protection board.

My idea is to lead two wires from the input to an external pack of 3 paralleled Panasonic NCR18650A (3100mAh 18650) batteries, totalling battery capacity to around 3.7v 10Ah.

My question is will this work? Charging and Discharging, reasonable accuracy on the percentage of battery capacity measuring? Thanks.


texts: How can one label a node with more than one name in SPICE/ LTspice

texts:
Update: node name "alias" (aka synonym) resolution seems to work fine in simple circuits... even though one of the two names "goes away" it's doing what I'd expect by namely referring everything to the correct single node. It's circuits involving subcircuits and models that aren't resolving synonyms as expected (particularly synonyms that appear within the library). At this point I'm trying to determine if it's a quirk of the libraries I'm using or if it's a limitation of SPICE when it comes to subcircuits and libraries.

I am working in LTspice though this question probably applies to SPICE as well. I have a small circuit I'm creating, however some components want VCC defined while others want VDD defined. In this case they are the same voltage (VCC=VDD=5V) from a single output power supply.

You cannot apply more than one label directly to a node. If you take a node, add a short trace and label one VCC and the other VDD, you of still end up with only one of those names actually getting defined in the netlist, since it's equivalent to one node and only one name is allowed per node.

There are hacky workarounds but I'd like to label my circuit correctly without any trickery (e.g., I could use an infinitesimally tiny resistance to create a second node to apply the "duplicate" label to).

Is there a mechanism in SPICE / LTspice for aliasing a node name to another name, such that the two may be used interchangeably?

Bonus: if not, why not? If SPICE can collapse a complex circuit into equivalent nodes (not exactly a trivial task) I'd think it could easily deal with simple name aliases...

Edit2: Perhaps a better bonus question would've been: why doesn't creating what appears to be an alias (either directly, by labeling the same node with two names, or indirectly by labeling each side of a jumper) throw an error in LTspice? For that matter, does it even throw an error in SPICE? (I suspect it does not given they are related at the core...) I came here because I spent a fair amount of time scratching my head wondering why one of the two names would get ignored as if it was never there... an error message from SPICE / LTspice would've helped immensely.)

Edit: The circuit is based on functional models of 7400- and 4000-series chips, not DIP models of them (thus there are no "pins" on the blocks for VCC / VDD (7400 uses VCC, 4000 uses VDD by convention)... you simply define them for the circuit as a whole and in this case I'm modeling the power supply as well). In short, drawing the power wires isn't an option anyway.


texts: Does silkscreen help with voltage creepage distance?

texts:
I have seen on various mains powersupply PCBs that they have a lot of silkscreen lines near the high voltage areas. So my question is that does the silkscreen helps rise the voltage rating of that section or is it just to mark that area as the high voltage one.
I am designing this PCB and was wondering if I should put silkscreen or not.
In terms of voltage creepage rating is there a difference between Left and Right?

This is an image from smps.us and this table shows the creepage distance for 100Vdc for 1. External, 2. Internal, 3. Coated.
Does the coated here means only coated with soldermask? Or does adding silkscreen to the mix also helps somewhat?


texts: Connecting multiple motor power outputs to one source

texts:
I am trying to make a wind turbine type thing. I have 4 motors being turned at the same time to produce energy, however I would like all of their power to go to one place and i am having troubles doing that, so my question is how can I connect all 4 motors to one output?

Update for anyone with questions: all I know is that the motors are DC and from hair dryers, unfortunately they did not come with specs. I am setting up the motors to run parallel to each other connected by a gear system. Each of the motor's output is about 120 mV. I'm quite new at all of this so if this update doesn't make things clearer I apologize.


texts: What is the reasoning behind the arrows on the circuit symbols of NTC (up and down arrow) and PTC (two up arrows)?


texts:
I have a question regarding the PI controller.
Lets say I have an actuator via which I control
some plant. The control signal at the output of
the PI controller is at its maximal realizable
value. So the actuator supplies 100% power
into the plant. Despite this fact the time
response of the control loop is sluggish. Does
it mean that the actuator has been chosen in
wrong manner for a given plant?
Thanks for clarification.


texts: Noise that resets a device that I would like to avoid from chip reset pin

texts:
History/context:
I talk about a 15Mhz noise when drill machine or any kind of machine activation in my network, before, at other post. By the moment neither RC, RL or RLC butterworth low pass filter designed for 15Khz is not having any effect at PCB voltage inputs line: no attenuation, no wave form change, etc.. the same that being a wire instead of a circuit. This part was treated there.
About system power. The noise was also appearing when using dual power supply, for laboratory usage. It was bought at Farnell or RS distributors. The other power bank supply is being used for years inside banks that were manufactured here.
The noise appears not only at Vin, Vout circuit lines. It has also seen at VCC pins from connectors of other old PCBs (12V, 24V, 5V), even at Raspberry pi, Arduino, etc GPIO and/or power lines. But they seem not to have behavior problems as my PCB. That is the thing why I try a second why to face the problem. It seems that any tested hardware could avoid this noise.
The problem to solve:
My functional problem when noise appears is located at reset line. It resets devices configuration: configuration register value became a 0x00 and devices loses their configuration.
When talk about devices I mean MCP23S17.
Reset line was first implemented from Raspberry Pi GPIO output. After the problem of noise, we decided to force devices reset pin to 3.3V. So it will always be enabled. Now, there is no line between the Raspb GPIO output and devices reset pin. Trace was removed. They always are enabled when the PCB is powered. One board has 8 devices, but I have other one that has only one of them. Two both resets are forced to VCC = 3.3V.
Focus:
I would like to focus the post to the problematic effect on my PCB and ask for other suggestions in the reset way: try to solve the noise effects on the reset pin. As by the moment the only problem that the transcient is causing to the system is the undesired reset, could I try to avoid the transcient effect at reset line?
The noise causes that the reset signal falls down from 3.3V to 0V for a while and resets the chip. 3.3V is a 5V regulator output. 5V comes from a commercial source supply, a power bank. But noise can be seen at 5V regulator input and 3.3V regulator output, it also can be seen at reset pin of the chip.

Blue is 5V (bank Vout = regulator Vin) and yellow is reset pin (tied to 3.3V, so regulator Vout). As can it be seen there when drill machine is on noise transient appears for a while. I measured the freq and it is always about 15Mhz.
My ideas for solving it:
So I thought about to add some circuitry for avoiding the fallen voltage (from 3.3V to 0V) at chip reset pin. It must still being 3.3V although this noise. Looking for reset circuits I have found this configuration and I tried adding it:

I get experimentaly the best adjustment at:

R = 20K
C= 120pF
Q = BC567
"reset" wire is forced to 5V (bank power Vout)

I put a probe at 3.3V and the other one to the Emiter node (that will connect reset device pin).
I got:

Blue is emiter probe
Yellow is 5V

This kind of circuit adapter seems to filter and to reduce noise effects. But this is my best result. By the moment I don't know it this level of attenuation will be enough when I connect it to the real reset. The next step is to connect it to the system, set up, check it and take measures. It seems to be a good way. I don't get this noise level before.
Askings:
Can anyone suggest:

any modification of the circuit above in order to improve a bit more my wave  form results?
other kind of circuitry for avoiding pulses at reset pin?

Please if someone has better ideas let me now. I will be grateful.


texts: Is it possible to run a motor inside a black box by applying an EM field, without knowing anything about the motor?

texts:
Is it possible to run an electric motor located within a container by applying an external EM field over the container, if you do not know anything about the motor?

The container with the motor would basically be like an unknown black box. It would have to run solely from the power it gets from the external EM field.

Is this possible?

Update:
Apologies for not providing sufficient information the first time around. This question came to my mind when I was thinking about different potential security weaknesses in modern cars (the type that would allow someone break in). I had read that there were supposedly a device that allowed thieves to unlock car doors without the actual key. So I started wondering if there was a way to apply an EMF field to the car door to run the window motor from the outside. If there is then this would be a security problem.


texts: Wrong FFT result when using rfft function on STM32F4


texts: How is dc restorer circuit used for PWM demodulation/detection?

texts:
In the Microelectronics Circuits textbook by Sedra & Smith, it is said that:

  As an application, consider a pulse signal being transmitted through a capacitively coupled or ac-coupled system. The capactive coupling will cause the pulse train to lose whatever dc component it originally had. Feeding the resulting pulse waveform to a clamping circuit provides it with a well-determined dc component, a process known as dc restoration. This is why the circuit is also called a dc restorer.

  Restoring dc is useful because the dc component or average value of a pulse waveform is an effective measure of its duty cycle. The duty cycle of a pulse waveform can be modulated (in a process called pulsewidth modulation) and made to carry information. In such a system, detection or demodulation could be achieved simply by feeding the received pulse waveform to a dc restorer and then using a simple RC low pass filter to separate the average of the output waveform from the superimposed pulses.

From: Microelectronic Circuits by Adel S. Sedra & Kenneth C. Smith "The Clamped Capacitor or DC Restorer" - section 4.6.2 in 6th Edition, or section 3.6.2 in 5th Edition

Now I thought the dc restorer circuit is supposed to perform voltage level shift. How does it also demodulate a PWM signal?

The process mentions the pulse signal going through an ac-coupled system and then feeding it to dc restorer. Doesn't this just change the signal from DC to AC then DC? How is the width translated to magnitude? Thanks.


texts:
Is it possible to create the schematic below with transistors in any way?

As I see it, there is no voltage difference between j1 & j2, so a transistor connected the normal way would not work.

The purpose would be to either bypass a dead cell, or to do a coarse voltage change.


texts:
I've found some Do-it-yourself guides to making a 4-AA battery gadget charger, which are basically four AA batteries connected to a cut up usb cable:

http://robotification.com/2007/09/15/diy-usb-travel-charger/

http://www.instructables.com/id/Build-a-4-x-AA-USB-Altoids-Battery/

Such a device uses the AA batteries to recharge your gadget.

This looks like a useful project, but I was wondering, is this safe to use long-term, for gadgets like smartphones/android devices/mp3 players/tablets/etc.? Assuming it is connected with the right polarity, and lower-voltage rechargeable batteries are always used, it should always be around 5 volts, which is standard for all usb, but isn't there supposed to be a circuit to prevent overcharging? Is the worst case here simply not charging, or bricking the device?

Also, what would keep this from reversing? If the AAs went dead, would plugging in your phone actually drain the phone's battery to the rechargeable AA's?

Update -

A 5v regulator with red battery connected to input, red usb connected to output, both blacks connected to ground, doesn't seem to be charging when the battery is dead. I'm wondering why this recommends connecting green and white to ground. Wouldn't this make voltage return through -, d+, and d-, which is not recommended?


texts:
Trying to tune the SI4735 chip to an FM station.
Have using this library and example to drive the chip with Arduino UNO and based on the console output from the sketch the control interface works fine: https://github.com/pu2clr/SI4735/tree/master/examples/SI47XX_01_SERIAL_MONITOR
It's going through the FM band but cannot find anything, it's all just noise.
I've a chip on a breakout board with the crystal and capacitors soldered to the breakout board and the breakout board plugged into a solderless breadboard + an op-amp based headphones driver on the breadboard.
Edit: I've measured the signal on the crystal and it's as expected - a 32.768KHz sinewave.
I tried powering the Arduino from my desktop's USB or from batteries and it doesn't make any difference.
Edit:
It sounds like radio noise when it's not tuned to any station basically.
And when it's tuning from one point to the other it's a different digital DJ sort of sound, I guess that's how it should sound.
I've probed the output of the chip directly before the amp and it looks like noise as well (flat FFT and looks like noise in the time domain as well).
The antenna is a ~50cm piece of a 30AWG wire-winding wire.
Edit: The resistance between the FM input (FMI) pin and ground measures to around 200K.

simulate this circuit – Schematic created using CircuitLab
Edit: The thin yellow wire is the antenna. The pin it's connected to the breadboard, I've cut it on the header.


texts: Configuration to measure voltages of batteries in series

texts:
I'm implementing a battery voltage monitoring system which uses the MCU ADC differential mode like the picture below. The batteries are connected in series and I'm quite sure that battery ground and MCU ground are isolated. The MCU is the F28377S from Texas Instrument, it's a 3.3V MCU, it has 16 single ended ADC channels that could be paired up into 8 differential channels.

With this configuration, I hope that there will be no ground connection between the charger and and the MCU. With the ground completely isolated, no common mode DC offset, the MCU will be able to handle a 12V battery pack since its ADC only tolerates up to 3V.