texts: Power rail design from Li-Polymer battery chip output

texts:
Case:

I am building a battery driven device and so far it seems like I will be using the MCP73871 to provide my device with battery power and charging via USB. (Datasheet )

I need to regulate the output from the MCP73871 to 5V and 3.3V. The 5V is to power the digital part of the circuit (microcontroller mostly) and the 3.3V is to power an accurate analog measurement circuit.

The Li-Polymer battery will have a voltage between 2.5 - 4.2 V so must be able to convert from this range to 5V and 3.3V.

I am looking for design recommendations.

Some questions that arises:

1) Is it possible/does it exist a non-switching step-up converter?

2) If I need to use a switching regulator to get 5V, should I use one boost converter to get 5V and one boost/buck to get 3.3V? (As the input voltage might be higher and lower than 3.3V)

3) If I use a switching regulator (boost) to get 5V (for the less sensitive part of the device). Do I still benefit from low noise on the power rails by using a LDO or non-switching regulator to obtain 3.3V if I connect it on the regulator outputting 5V? Is this a better solution with respect to noise on power lines?

4) 5V and 3.3V are very common used voltage levels and I assume there must be some type of chip that can have an input of 2V+ and output both 5V and 3.3V simultaneously? If this is the case, an example of such a chip would be appreciated, but do they have/exist with low noise features?

The questions above reflects my thoughts on how I see this might be solved. Any other ways are very welcome!

EDIT:

I am using an ARM Cortex M-3 running at 72 MHz. It will for the most time be in sleep mode and when running it will be clocked at 72 MHz. Is also has bluetooth communication draining some battery.

It is possible to be running the digital part at 3.3 V as well.


texts: Boost converter based on 555 timer not working

texts:
I tried to make a simple boost converter circuit for driving an LED using 555 timer IC, but somehow the output voltage is not increased at all. I suppose that the problem is the inductor I used, since I was unable to find a suitable one (i.e. around 220uH) and I end up using a 33uH.

Can somebody help me to build a 220uH inductor, or help me find a solution regarding the boost converter not boosting?

I am supposed to give around 3V input and get at least 12V output.

The components I used are:
555 IC
IRFZ44N MOSFET
100uF 25V capacitor
1N4007 diode
10k variable resistor
33uH inductor

Schematic source: Et Discover

The circuit diagram used is this. Also note that I used a 20nF capacitor with the 555 IC which, according to diagram, should be 100nF. Is this the problem or the inductor as mentioned?


texts:
I would like to add ADC functionality to a TI C6748 dev board. I need 16bit precision, but relatively low sample rate(~5K).

Not finding any suitable daughter ADC card, I am considering the possibility of making use of the on board stereo codec TLV320AIC3106.  I notice its analog input voltage range is quite limited (-0.3V ~ 0.3V). But my input voltage range is 0~5V.

Do I just need to scale the signal amplitude such that it falls into [~0.3V ~ 0.3V] range? Any other implications that using an audio codec as a general purpose ADC?


texts: Is it normal to have around 40 V in your body, when touching your plugged, ungrounded laptop?

texts:
I have had bilateral shoulder pain and then both arms and hands pain for around 7 mounts, which got much worse when I started working from home, with my laptop.
The ultrasound of shoulder muscles revealed tendonitis which means inflammation in tendons.
Nothing helped my pain relived, not the physiotherapy, message therapy or even pain killers and voltaren gel.
In recent days I accidentally discovered that when I am working with my laptop, and touch its body, it is giving my body a voltage of around 37-40 V (I measure it with a multimeter set on AC V, one pin connected to the ground connection and the other in my hand)Laptop have a two pronged plug and is not grounded.
When I checked this with one of my friends, he is getting around only 5-6 volts the same way of measuring on his own, ungrounded laptop.
I bought this laptop (Asus Zenbook UX431) about 8 mounts ago, so it can explain the onset of pain in my body as well.
My doctor refused to accept this can be a reason for my problems, but I have strong feelings and reason that this can be behind my issues.
I wonder if you can also measure the voltage induced in your body while touching your laptop's body and tell what you get? I need more evidence if his can be the source of my problems.
I just need some of your measurements and numbers, Thanks so much!


texts: Writing I2C library - Philips trademarks

texts:
I guess is a very trivial answer for many but I am not sure in my case.
I am writing an open-source firmware, which might also get documented and commercial use is not excluded from who is using it.

This involves an I2C capability. Is there any issue in calling it I2C, or should I change the name? Like Arduino called it TwoWire, some IIC. Shall I invent a new name, or using a random name in the code and documentation? Are there some "free" namings for I2C?

If you want to downvote, please be constructive and/or address me to the right space.


texts: Controlling the countertorque of a permanent magnet synchronous generator

texts:
I would like to understand if it is possible to use a circuit to regulate the countertorque provided by a permanent magnet synchronous generator (PMSG) all the way from zero torque to a maximum torque. I am thinking mostly about PMSGs like those used in wind turbines.

There are several papers online that discuss "direct torque control" (DTC) of a PMSG. E.g.:

http://www.icrepq.com/icrepq%2712/448-abdolghani.pdf

http://pe.org.pl/articles/2016/10/56.pdf

I am trying to understand how this works in detail and what range of torque values is available (as a % of the generator's maximum countertorque).

Specific questions:

How does DTC work, in layman's terms, when applied to a generator? Are these methods effectively decreasing the load felt by the generator? Or, are they putting a current into the generator to drive it like a motor and compensate for the inherent electromagnetic torque? Or some other explanation?

What is the range of torque values that such methods enable? How rapidly and reliably can the torque be controlled? In particular, can these methods enable the PMSG to have zero countertorque at one moment and a maximum countertorque a few moments later?

I have read about both "field-oriented control" (FOC) and "direct torque control" (DTC). Can both of these methods be used to adjust the countertorque provided by a PMSG?

Finally, in an electrically excited synchronous generator (EESG), it seems intuitive that you could reduce the countertorque provided the generator all the way to zero by simply decreasing the DC current in the field coils, without a complicated control circuit. Is this correct? How does this torque-control approach compare to using DTC?

Thank you!


texts: 2 levels of brightness for led illuminated switch

texts:
I'm think of using a switch in my car. The switch has 5 leads ... +, -, C, NO, NC. 12 V to the + and - light the led (brightly). What I would like it to do is light up the led dimly when the dash lights are on AND light it more brightly when the switch is on.

How would I do this?

Or would it be simpler to have it light up dimly when the switch is off ... resistor between NC and +, and then brightly when switch is on (direct wire from NO and +)? I'm thinking this could be a problem because since the device I want to turn off and on will be wired to NO ... it will get power from NC (through +) when the switch is off ... this wouldn't be good! Is there a way to prevent this? or perhaps a better way to go about the whole thing (apart from having a switch with 2 leds)? Sorry I'm not too electronically knowledgeable so answer accordingly please lol.


texts: Voltage rating of 3.5mm jack audio output

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I am building an audio amplifier using TDA2030.
I want to know what is voltage (RMS or peak-peak) rating of typical audio output from 3.5mm jack.
I am doing a simulation in Proteus, and I am having trouble deciding what should be the input voltage and frequency which should be provided to the amplifier through a sinr wave generator to get the best possible result (similar to the actual situation.)
If I provide a higher or lower voltage signal to amplifier I didn't get the required result and can damage my speaker afterward.
I want to design an amplifier so that it doesn't damage my 5W speaker.
Suggestions are welcome for the circuit below.


texts:
Would any of the via's in the picture be considered a via-in-pad?

or is it only if it's dead center of the pad?


texts: Does each microcontroller line have its own programming language/syntax?

texts:
I've programmed the Arduino and have started programming the Teensy. They are similar to C but there are slight nuances in the programming language.

For instance, in Arduino's C you call a function pinMode(pin#, Output/Input) to designate a digital pin to either output signals or receive signals. In Teensy's C, you set the "DDR" register associated with one of four ports (each of which represents a collection of pins) which you collectively designate as either input or output (Teensy IO syntax).

I would like to know if it is the case that when you use a microcontroller that is new to you, you need to effectively learn a new "language". I put the word "language" in quotes because despite the nuances in syntax, the components and how they are set up in software are fundamentally equivalent e.g., the notion of ports and pins still refer to a terminal from which you can output/input digital signals.

In the same vain of discourse: are there microcontrollers that aren't programmed in software or will there always be a software layer used to program the uController? If the latter, who writes/provides documentation for them?


texts:
I am having some problems with UART communication with the RN-42 SM Bluetooth module. Currently, I am just using polling to get communication going. I have my source files below.

The problems is that I can send properly, however cannot receive. I have been able to receive PARTS of a response, but it seems that the Transmit, sends a command before I can receive the whole buffer.

Note also that I am trying to retrieve a string of values. So for example, if I send a '$$$', I get a 'CMD\r\n' in return. I am trying to retrieve the latter.

SOURCE FILE

DDRC |= 0xFF;
DDRD |= 0xFA;

initUART();
unsigned char pinRTS = 0;
unsigned char buffer[RXBUFSIZE] = {0};

UNSETCTS(PORTD);

while(1)
{
    PORTC ^= 0xFF;
    pinRTS = GETRTS(PIND);

    if(pinRTS == 0x00) { //Receiver is letting us send
        SETCTS(PORTD);
        transmitStr((unsigned char *)CMDMODE);
        UNSETCTS(PORTD);

        waitForRcv();
        rcvStr(buffer);

        SETCTS(PORTD);
        transmitStr((unsigned char *)EXITCMD);
        UNSETCTS(PORTD);

        waitForRcv();
        rcvStr(buffer);
    }
}

HEADER BELOW

#include "serial.h"

void initUART() {
    /* Set baud rate */
    UBRR0H = (unsigned char)(UBBRVAL >> 8);
    UBRR0L = (unsigned char)UBBRVAL;

    /* Enable receiver and transmitter */
    UCSR0B = (1<<RXEN0)|(1<<TXEN0);

    /* Set frame format: 8 data, 1 stop bit */
    UCSR0C = (3<<UCSZ00);

    /* Double the speed */
    UCSR0A |= (1 << U2X0);
}

void USART_TRANSMIT(unsigned char cmd) {
    /* Wait for empty transmit buffer */
    while ( !( UCSR0A & (1 << UDRE0)) );

    /* Put data into buffer, sends the data */
    UDR0 = cmd;
}

void transmitStr(unsigned char *cmd) {
    int i;
    for(i = 0; cmd[i] != '\0' ;i++) {
        USART_TRANSMIT(cmd[i]);
    }
}

unsigned char USART_RECEIVE()
{
    /* Wait for data to be received */
    while ( !(UCSR0A & (1 << RXC0)) );

    /* Get and return received data from buffer */
    return UDR0;
}

void rcvStr(unsigned char *buffer) {
    int i = 0;
    while ( UCSR0A & (1 << RXC0) )  {
        buffer[i] = UDR0;
        i++;
    }
    UCSR0A |= (1 << RXC0);
}

void waitForRcv()
{
    while ( !((UCSR0A >> RXC0) & 0x01) );
}

Thanks for your help. :)


texts: Strange behavior when connecting ideal voltage-source and capacitor in series?

texts:
I just learn from youtube video that if capacitor is connected with ideal voltage source in series, its voltage graph would be like this :

(Sorry, but adding as picture is much better than drawing it by myself)

What I can't understand is that when Vin goes high, why does Vout goes high, too? One side of capacitor could go high because voltage source draw electrons from capacitor, but other side of capacitor is floating state!..

I have no idea how I can interpret it.

Thanks


texts:
This is the circuit I plan to implement to control a LED by a logic bit

simulate this circuit – Schematic created using CircuitLab

The datasheet of the transistor can be found here

I used FET transistor as amplifier, so I know about the saturation zone that let you get a voltage gain. However, I never used fet as switch, therefore correct if I am wrong.

In that zone, the MOSFET behave as a variable resistance. So if I work in 3.3 logic, when I put 1 into the gate, The mosfet will behave as a 2-4 ohms resistance (from the datasheet), where the channel will let pass current up to 50 mA? When I put a 0 into the gate ( Vgs < Vth) , the mosfet will not conduct.


texts: How do current spikes over limit affect Lithium battery life?

texts:
In one of my application, I am using Tadiran Lithium Thionyl Chloride Batteries MODEL TL-5934. In the data sheet , the max pulse current shows 50mA.

However, in my application, we have low duty cycle current spikes  up to 70mA.

Our battery are draining twice the speed as I calculate.
How will these current spikes affect the battery Life??

This is the datasheet of Lithion battery we used

In this chart, it estimated that 0.2mA constant current draw will drain the Unit in about 4000 hours

This is our appication's current draw profile. 50000 points acquired by DMM in 50 sec. Constant current draw is very small probably 0.01mA, however, have lots of current spikes, which I suspected kill the battery much faster.


texts:
I have been trying to solve homework questions on three phase systems but I am got  stuck in two questions  while solving solving them.

  Three similar impedances are connected in star across 2000V, 50Hz three phase
  supply. Power absorbed is 300KW. Current taken is 100A lagging. Find the values of
  circuit parameters in each phase.

While Solving this, I calculated : V_ph =2000/√3=1154.7V and the impedence to be: Z=Vph/100=11.54 ohms.

The power factor is:2000/3XVphXIph which comes out to be 0.28.

My question is how can i caluculate the power for each impedence.As far as I know ,I only know equation for total power

  A three phase 400V motor has an output of 20HP with efficiency of 90% and at a power
  factor of 0.8. Determine the reading on each of the two wattmeters connected to
  measure the input. Also find the line current.

So  input Power is 90% of 20 that is 18 Watts

So I presume W1+W2=18 watts

My book gives the formula: tan(θ)=√3(w2-w1/w2+w1) or tan(θ)=-√3(w2-w1/w2+w1) where w1 and w2 are wattmeter readings in the wattmeter. My question is how do i identify which equation to use.

Can anyone please help me with these doubts and also tell me what I am doing wrong.

EDIT:

input power is 100HP=74.57kW.


texts: What's one way for recognizing an object (pre guidance for making a device)?

texts:
I want to make a device that will recognize an object, for example: cube, sphere etc. I have two sensors that make a pulse for measuring distance between the sensor and an object as shown in this picture:

Due to picture, T4 is the width of the pulse and the T2 will change due to object.
I can recognize the object by this amount. For this job, it is necessary that first I put the objects one by one under the sensors and save the amounts from the sensors (with the name of objects).

Next, for exmaple, for recognizing an objects, I put the object under the sensors and the MCU (or processor) says the name of that object. There are two sensors and the 100 objects. For each object I want to sample 20 times. Thus, for each object, I should save 40 amounts. Which processor or microcontroller is suitable for this job? AVR, ARM based microcontroller, FPGA... Any suggestion on a device to do this job?


texts:
I am going to build a stage box, and I need 5V for that (to add some logic, maybe even later an STM32).

I also need mains (220V) for a 12W RGBW LED PAR light.

At first I thought to put in the box a 'wall socket' with two 220V plugs, but since the 12W needs to be switched by a relay, only for 5V I need a solution.

My thoughts were:

Using a buck converter like this. However, I don't see any holes, so I don't know how to fix it inside an enclosed box.

Using an already enclosed converter like this. I also don't see holes here, but at least I can glue it on one side. This one is twice as expensive (but still cheap).

Using a switching power converter like this. This one has holes, but cost even more. And I don't need the power it can deliver.

Using an adapter (220V->5V).

I'm quite a novice, so these questions might be trivial but not for me:

About option 1: How can I 'fix' this part in an enclosure? With using glue? I don't think it will be safe for 220V, especially if I want more in the enclosed box (like the STM32 later).
About option 2 (but also 1/3): Can I safely put this in a 'closed' enclosure? I think I can since the power usage is quite minimal (200 mA, maybe even less). So actually option 2 is already an enclosure, but I want to put it in a bigger enclosure with all logic (STM32 possibly and the relay).
About option 3: I like the holes, but that's it. Feels awkward to buy this just because it is the only solution with holes to fix it.
About option 4: I feel more comfortable with an adapter, however, I really don't like the idea to put inside my stage box a wall outlet, just to put the adapter in. I though about cutting of the 'adapter' part, but still what I keep is essential option 2.

(Actually all questions come down to: how should I fix/consolidate them in an enclosure and will I get problems with heat?)


texts: VNAs and different characteristic impedances

texts:
What is the right technique to measure a matching network, cable, etc that is at a different characteristic impedance than 50Ω?

In my case, I need to measure the SWR of a matching network that needs to be 125Ω. However, the SWR on my HP 8753B is of course in relation to a 50Ω Z0. I though I could just set the VNA to a new Z0, but that doesn't seem to work.


texts: Parameters of the 3 phase geared induction motor

texts:
I have a 3 phase geared induction motor. The name plate is below image.
I couldn't find any datasheet from internet.

Explain me parameters that on nameplate for entering to VFD.

I need to know Rated power.( This has a code. I cant understand that.)

What are n1,n2 means?

Why two value for cosφ and amperage?

This motor also able to run using delta configuration?


texts: What is the functionality of negative reset pin in ATTiny45? Am I correct that reset pin is used to reset the controller to some random state or am I wrong?


texts: What kind of oscillator is this circuit?(processor oscillator)

texts:
I was just seeing the datasheet of a motherboard and saw this oscillator circuit:

What kind of oscillator is this circuit? what are the usage of those resistors?

As you can see it has two input and output(ATI_XTALIN/OUT) that go to the processor but what about MKX1/2?


texts: Simulink scope changes value depending on simulation time

texts:
I am making a co-simulation in Simulink for a circuit that I made in ORCAD, and I saw this problem that appears: If I put the final stop time for simulation 10s the signal looks like in first picture where you can see that the distance between those two points is 0.787ms. When I change the stop time simulation at 30s the signal looks like in the second picture. As you can see the distance is shorter now: 0.389.7ms.
I am thinking that the whole scope window has a limited number of points and if I increase the stop time simulation it tries to fit the signal in those numbers of points but I am not sure. I would like to know your opinion. BTW I didn't let for the second picture the full simulation until 30s.


texts: Automatic Temperature Controller with Thermistor (Incandescent BULB)

texts:
I'm new in this site
And sorry for my english language..

I need a circuit for my little oven.

I use an incandescent bulb (4x100W) for heating, and I want make a dimmer circuit to change output using a temperature sensor (ptc or ntc).

I have an AC Light Dimmer I want to modify. I want to change the potentiometer to ptc but I can't find a 470k ptc...

What are your ideas for it?

Can I use this circuit?

With PIC16F88


texts: What is my multimeter measuring when in AC mode?

texts:
My multimeter says "True RMS".
Nowhere in the manual do they say that when in AC mode, the value displayed will be the RMS. Appearently it is so obvious for everybody that they just don't say it.
Is it always assumed by default that a multimeter will measure RMS in AC mode? Just making sure.


texts:
I am trying to model a thyristor DC switch but I am having problems with properly turning "ON" the SCR that is used as the switch. I am using a 2N1595 SCR and I've looked at its datasheet and it seems like the parameters I have for my gate current source and gate resistance should trigger the SCR. However, it seems the thyristor continues blocking the current in the circuit even after the gate current gets applied. How can I fix this?

This is the circuit design on ORCAD Capture:

This is the current/time graph of R6:

This is the current/time graph of R5:


texts: PID gains from the transfer function of a plant

texts:
I am trying to calculate gains ( Kp, Ki, Kd ) of a PID controller. I have to improve the response of a plant. I already have the Transfer function of the plant.

I was wondering if matlab has some command for calculation of controller gains ( kp ki and kd ) from the transfer function of the plant and it finds those gains based on certain parameters ( less than 5% OS, no Steady State error )

PS - I would highly appreciate solutions other than simulink

EDIT:

TF = 1.546/s+0.497


texts:
I have a project... Including cats. We have 3 cats, two teenagers and one old man, named Oliver. We want Oliver to be able to eat whenever he wants, but we don't want the other cats to eat whenever they want. I was thinking of designing a box, with some sort of proximity reader in it. Oliver would have a proximity tag, or sometng of the sort, to let him in. He would then have a source of food to eat.

At first, I was thinking RFID tags, but those are expensive and normally only used in businesses.

Then, I thought maybe reed switches would work, but those require semi- powerful magnets to work well.

What should I use to detect the proximity of Oliver, but not either of the other two cats? Thank you.


texts: How to read out data from this moisture sensor?

texts:
I found a cheap moisture sensor on Ebay that only came with the schematic attached. The moisture can be read with an analog or digital signal.
However, I am wondering how the opamp creates a digital signal, and how to read this signal from a microcontroller. The schematic is this:


texts:
I've been trying to learn how to properly set up a circuit for power regulation. Often I hear for domestic use that it is better to use a transformer to isolate the device as well as stepping down the powerline voltage (230V RMS here). Seems pretty straight forward for lower voltages, but what about a heating element which is supposed to be supplied with 230V RMS? Is a 1:1 transformer still needed? If yes, is a 1:1 transformer and a LR8 regulator enough (obviously with some more passive elements and diodes) to generate a 5V (for a µcontroller for example), or will I need a second transformer?

If useful, the point is that my project will need 3 voltages: AC Line (heating element), about 15VDC (Peltier element), and 3.3/5VDC (µController, gates, fans, etc.).

The heating element is something like this.


texts:
"Calculate V (across the current source) and the current flowing down through R1."

simulate this circuit – Schematic created using CircuitLab

Does the voltage source also produce current, so that the current flowing to the parallel resistors is the sum of 40mA and the current produced by the voltage source? (For knowing which value to input into current division formula)


texts: Help understanding 3.3v logic vs 5v logic with Raspberry Pi GPIO

texts:
This will probably be an extremely easy question for the seasoned EE's of you in the community. My question is this, I have 5v and 3.3v devices I want to interface with my Raspberry Pi's. I'm paranoid about burning out my Pi with some dumb wiring.

1) If I set a Raspberry Pi GPIO pin HIGH (3.3v) to a device that requires 5v logic only to be driven, do I still need a logic level converter in the mix? Or is that only required when I am accepting 5v logic (sensor or bidirectional).

2) Is there a safe way to accept 5v logic into a Raspberry Pi GPIO if the current is low enough, or do I always need to convert it down to 3.3v?

I'm just looking for some words of wisdom on how to handle logic levels and general rules of thumb. If a simple link answers this feel free to shoot it my way. I appreciate the help!


texts: What are the proper labels for these wires in this AC power cord?

texts: I am trying to wire this AC power cord to a 5V 20A power supply, but it appears to have non-standard coloring. From what I've read, blue is ground, white will go to neutral, and brown will go to L, correct? This is the view with the female connector facing the camera.


texts: What do memory configurations like "256Kx18" mean?

texts: This is a beginner question here. When choosing memory ICs, one of the options is the memory size/configurations. I understand the size part, but what does the "16Kx9" mean? It seems the same memory size is usually available in different configurations. I attached a screenshot from Digikey as an example.


texts:
I wish to plot out the current and power in ngspice. In the case of voltage, for example, if I wanted to plot the voltage at node 1 I would use:

plot v(1)

Problem is, when I try i(1), the vector isn't recognized. Could someone provide a few examples on how to do this?


texts:
I am planning to connect (at least) two Raspberry Pi + PiCAN2 shields via CAN.

I think I understand the concept of a daisy-chained multidrop CAN line, but what about using the 120 ohm resistors for termination that are provided on board by the PiCAN2 shield?

As far as I understand when I simply connect CAN High and CAN Low respectively between both PiCAN2 shields A and B as shown below, I should use the 120 ohm resistors on both sides for termination. Am I right?

What happens when I add a third identical node (Raspberry Pi + PiCAN2 shield) C to the CAN bus? Do I need to terminate also on this node?
As I can without problems also use the terminator on C, is there any drawback to using the 120 ohm resistor on all nodes, not worrying about the geometry of the network?

simulate this circuit – Schematic created using CircuitLab


texts: Is there a way to adapt a TSSOP pad to a SOIC-16 IC?

texts: So I messed up and printed a circuit board with 16 TSSOP pad when I actually need a SOIC-16 pad!!!  Is there a clever way of somehow adapting the TSSOP pad to a SOIC-16 chip?


texts:
Voltage across diode, Schottky Shockley equation

So I know how a diode works and everything. However when I stumbled upon this equation I just happened to have this silly doubt. Vd it says (in the equation) is the voltage across the diode. I know that every diode has a small potential difference and only when the applied voltage is greater than that voltage across the diode, electrons are able to cross the barrier.

Now my question is : is the applied voltage same as the voltage across the diode? If not how do we calculate voltage across the diode is a voltage of 5V is applied. You can consider a simple circuit with just one diode and a battery.


texts: Impedance matching for inductively powering / rectifier

texts:
I have two questions.

If the receiver is inductively powered (by LC resonator) and needs a matching network in front of the RF-to-DC rectifier, what kind of quality factor of matching network (or Qs of the capacitor and coil inductance) should I expect? Assume the inductive powering frequency is at 500 MHz.
Since there is a load at the output of rectifier to withdraw the current/power from the resonator, is it a low Q system in nature? If so, will it affect the selection of matching network component precision?

I am quite confused and cannot find some convincing answers. Any insight will be much appreciated. Please correct me if any concept in my description is not right.


texts: How is an NPN relay switch circuit analysed?

texts:
So I came across this good article: https://www.electronics-tutorials.ws/blog/relay-switch-circuit.html

It gave me a good insight into the different transistor-relay switching circuits. But unfortunately, it hasn't provided any detail regarding the analysis of such circuits, more specifically the NPN relay switching circuit.

Above is an image from the article, of an NPN relay switch circuit.

The only way I can think of working through the circuit is by modeling it as shown below and then analysing it:

I haven't analysed such a circuit before and would love to know what the general approach is.


texts: Can I use the same antenna for GSM and RF433 MHz?

texts:
I've already designed a PCB with GSM/GPRS chip and also with RF 433MHz receiver only (without transmitter).

I would like to know if I can use the same antenna for both GSM/GPRS module and RF 433MHz receiver module?


texts: Verilog Down Counter Logic Implementation

texts:
I'm trying to write logic for storing trigger data. For example, I'm using a 3-bit counter as an address generator to store data samples. When I have a trigger event, I want to store the 4 data samples just before the trigger event occurred and the 4 after wards. So I use a 2-bit down counter when the trigger occurs and stops the counter when it counts down to 0 thus giving me 4 data samples from before the trigger and 4 data samples after the trigger.
I'm having trouble implementing this though and get only 3 addresses once I start the down counter and it counts down to 0

//=== 8-bit wide loadable up-counter =============================
`timescale 1 ns / 1 ps

module fw_up_counter_3 (tc, count, d, ld, en, clk, rst);

output          tc;
output  [2:0]   count;
input   [2:0]   d;
input           ld, en, clk, rst;
reg     [2:0]   l_count;
wire            tc;

assign  tc      = &count[2:0];
assign  count   = l_count ;

always @(posedge clk)
 begin
        if(rst)
                l_count <=      3'b0;
        else if(ld)
                l_count <=      d;
        else if (en & ~ld)
                l_count <=      l_count + 1;
        else
                l_count <=      l_count;
 end
endmodule

//====2-bit wide loadable down-counter=====================
module fw_dn_counter_1(tc, count, en, ld, clk, rst);
  output tc;
  output [1:0] count;
  input en, clk, rst, ld;
  reg [1:0] l_count;
  reg [1:0] d = 2'b11;
  wire tc;

  assign tc = ~|count[1:0];
  assign count = l_count;

  always@(posedge clk)
  begin
    if (rst)
      l_count <= 2'b11;
    else if (ld)
      l_count <= d;
    else if(en & ~ld & ~tc)
      l_count <= l_count - 1;
    else if (l_count == 2'b00)
      l_count <= 2'b00;
    else
      l_count <= l_count;
    end
  endmodule

module trig_test(clk, tc1, tc2, en1, en2, count1, count2, rst, ld, trig, trig_loc);
  input clk, rst, en1, en2, ld;
  output [2:0] count1;
  output [1:0] count2;
  output tc1, tc2;
  input trig;
  output reg [2:0]trig_loc;

  fw_up_counter_3 counter1(.tc(tc1), .count(count1), .d(3'b000), .ld(ld), .en(~tc2), .clk(clk), .rst(rst));

  fw_dn_counter_1 counter2(.tc(tc2), .count(count2), .en(trig) , .ld(ld), .clk(clk), .rst(rst));

  always@(posedge trig)
  begin
      trig_loc <= count1;
  end

endmodule

Anyone have any ideas on where I'm going wrong ?


texts: I am relatively new to PCB design and circuits in general. I am routing my first 4 layer board now and I am wondering about placing ICs on top of each other on opposite sides of the PCB. The ICs in question are fully differential op amps, part MCP6D11. They all are running on 3.3v and will have a gain of 1. I am wondering if it is okay to place the parts on top of each other on opposite sides of the PCB with their ground pads connected to each other through vias as show in the pictures below. Will this cause any signal integrity issues in the audio rate analog domain? Will it be a pain to hot air solder them if their ground pads are connected so closely? Any other issues that I am not thinking of?


texts: Troubleshooting audio output on Nexys 2 (FPGA)

texts:
I've recently purchased the PMOD AMP1 module from digilent for use with my Nexys 2.

When I program the demo project and plug headphones or speakers on the headphone output I can hear a barely audible, extremely high pitch tone on the headphone out.

After reading through the source I realised this project is setup for a 100Mhz clock while my board's clock is 50Mhz. I modified the synth.vhd as below:

entity synth is
    port(clk : in std_logic;
          syn_out : inout std_logic_vector(7 downto 0));
end synth;

architecture Behavioral of synth is

signal sclk : std_logic_vector(10 downto 0);

begin
    process(clk)
        begin
            if clk'event and clk = '1' then
            -- divide a clock by "10111010101" (1493) which is about the value of 100M/256/261.6
            -- where 100M is the clock frequency on a Nexys3
            -- 256 is the number of points in the sine wave table
            -- 261.6 is the frequency of a middle C
                if sclk = "1011101010" then -- MODIFIED decreased by half for 50Mhz clk (746 is new clock divider)
                    --"11111111" is 255 is the maximum point in the sine wave table
                    if syn_out < "11111111" then
                        syn_out <= syn_out + 1;
                    else
                        syn_out <= "00000000";
                    end if;
                    sclk <= "00000000000";
                else
                    sclk <= sclk + 1;
                end if;
            end if;
    end process;

end Behavioral;

As per nidhin I need to modify the pwm file as well:

constant ckPwmRange: integer:= 5;
   -- LSB in the cntPwm alias of cntDiv
signal cntPwm: std_logic_vector(ckPwmRange+8 downto 0);
   -- the most significant 8 bits are used for PW Modulator:
   -- cntPwm counts 100MHz/2^ckPwmRange

I think that since the clock is running half as fast, the cntPwm should also be halved.
I think this means ckPwmRange should be 2.5 but instead could I replace the cntPw assignment as:

signal cntPwm: std_logic_vector(ckPwmRange+7 downto 0);

?


texts: How to achieve four quadrant operation of the field oriented control of the three phase induction motor?

texts:
I have been developing software for field oriented control of the three phase induction motor. I have been facing a problem how to incorporate changing of rotation direction into the control software.
The requirement is to achieve a state where the motor is able to operate in all four quadrants of the torque-speed plane i.e. the machine shall work in motoring (braking) mode for both directions of rotation.
The rotation direction of the three phase induction motor is in my opinion given by the phase sequence of the stator three phase voltages which are basically produced by the three phase voltage source inverter in my situation. The problem which I have is how to incorporate change in the phase sequence of the stator three phase voltages in case the output of the control structure (the controllers of the torque and flux components of the stator current) is the desired space vector of the stator voltage.
Can anybody help how to do that? Thanks in advance for any ideas.


texts: MOSFET topology to switch between voltage and ground?

texts: What topology am I seeking to switch a load between an arbitrary, positive voltage and ground? I am trying to operate the rungs of an R2R ladder so pull-ups and pull-downs are inappropriate. The circuit is low power (<100 mA), low voltage (<20V) and low speed (<1 Hz).


texts: USB 3.0 board return current path on reference plane

texts:
I'm designing my first USB 3.0 pcb. I am curious what path the return currents (if any) will take on the reference plane.

The board will be an adapter that will be soldered to the end of a USB cable (see soldering pads on the right of the board) and holds a special connector to connect to a USB 3.0 camera.
I have routed the USB 3.0 differential pairs on the top layer with a ground plane underneath (layer 2 on Eagle).

There isn't supposed to be any return current in the ground plane since the signals in the differential pair cancel each other out but if I understand correctly, noise on one of the 2 differential traces might generate return current through the ground plane.
For instance if we consider the USB3_RX+ trace, the return current (blue arrow) will flow right under it up to the edge of the board. After that, will the return current loop all the way to the highlighted via, creating a large loop? Should I provide a more direct path to the ground pad / move the ground pad?


texts: Common mode choke parameters CAN circuitry - split termination concept

texts:
I am trying to the understand the important parameters of a common mode choke that will be placed at the CANL and CANH lines of a transceiver.

First parameter: Impedance as function of frequency - I'm looking up the impedance value at 500 kHz in the graph, since my application data rate is 500 kbit/s. Is this right?

Second parameter: Insulating resistance - how important is the insulating resistance between windings? In my understanding the more the insulating resistance is, the better the common mode choke is; is my understanding right? Also, how important is stray inductance? There is one other parameter called DC resistance (each line) given as a percentage. What parameter is this?

This question is regarding the CAN lines termination - in the split termination technique, there is a capacitor between the resistors connected to ground. In a lot of application notes that I've read, the value is always 4.7 nF for the capacitor, I'm trying to understand how this value is chosen.

"EMC measurements have shown that the split termination is able to improve
significantly the signal symmetry between CANH and CANL, thus reducing emission.
Basically each of the two termination resistors is split into two resistors of equal value, i.e. two resistors of 60 ohm (or 62 ohm) instead of one resistor of 120 ohm. The special characteristic of this approach is that the common mode signal, available at the centre tap of the termination, is terminated to ground via a capacitor. The recommended value for this capacitor is in the range of 4,7 nF to 47 nF" - this is from the application note AH1014
Application Hints - Standalone high speed CAN transceiver
TJA1042 / TJA1043 / TJA1048 / TJA1051

How is this capacitor value quantified? Would it be okay to use 100 nF instead of 4.7 nF? I read a few more Texas Instruments documents where they have calculated the corner frequency of the RC filter - 1/2*piRC , and R is taken as 30 ohm, so the corner frequency for 4.7 nF is 1.1 MHz. Does this mean all the noise above 1.1 MHz is cutoff, so therefore if the capacitor value is increased the cutoff frequency decreases, for 100 nF - the cutoff frequency is around 50 kHz.

Should the data rate of CAN be considered? The data rate is 500 kbit/s. Should the capacitor value be so selected that the cutoff frequency is above the data rate at all times?


texts: How feasible is it to localize a robot based on EM beacon?

texts:
I am designing a little tabletop robot with a very simple goal of keeping track of where it is on the table as he traverses it. This, as it turns out, is a lot more difficult than I imagined.

All the obvious solutions like using an accelero-gyro combo and using distance sensors seem to be flawed as they either drift very much or are noisy and unreliable.

So I came up with the idea to install some kind of EM beacon on the vertices of the table. I don't have a detailed theoretical understanding of EM waves but here is what I have gathered so far:

I can generate a simple EM wave by exciting an antenna with a sinusoidal wave (with an R-2R DAC)
An EM receiver is an antenna output hooked to an op-amp input with its output going to a DAC. I can use a microcontroller to get the peaks of this signal and collect data on how distance affects amplitudes. If I plot this data on the computer, I should see a relationship between distance and amplitude of waves.
Then I can use this relationship to measure the robots distance from that particular beacon. If I use different frequencies for the 4 different beacons, The robot should be able to calculate its position on the table.

I'm a programmer first so I am sure I can handle the digital portion of this setup. I am, however, concerned if EM waves work the way I expect. Am I being too naive with this?

Basically what I want to know is this: Is it reasonable to expect that this setup will work reliably, assuming that the digital parts of the system work fine? Has this been done before, and reliably? What are the sources of error that I have not been able to gather?

Any suggestions/tips/resources are welcome.

Edit: While the answers are interesting and have provided me with lots simple ideas to accomplish what I'm trying to do with my convoluted setup, none of them really answer my question. As such, I think that unless I conduct the experiment myself I am not going to find an answer.


texts:
I'm designing a PCB with some noise-sensitive components (FPGA, RF mixer, etc.). For the power systems I've decided to chain switching regulators to LDO regulators so that I get less heat dissipation and better noise performance than either alone. However, I'm unsure as to the optimal location of the LDO regulators. My thought is that they should be placed near the outputs of their corresponding switching regulators so that switching noise is confined to the edge of the board. Or is it better to place them near the loads they drive? The second setup could result in a slightly more accurate voltage across the load since less of the LDO output voltage will drop across the power traces, but since my board isn't too big and I have room to make the power traces wider if need be, I'm not too worried about that. I'm also not too worried about trace inductance because the bypass capacitors should take care of that.

What else am I not considering here? Is there a typical way this is done?


texts:
I have a simple question that is stopping me.

This program runs whit out an error, it increases "x" and show the result in the display, but...

// LCD module connections
sbit LCD_RS at RD4_bit;
sbit LCD_EN at RD5_bit;
sbit LCD_D4 at RD0_bit;
sbit LCD_D5 at RD1_bit;
sbit LCD_D6 at RD2_bit;
sbit LCD_D7 at RD3_bit;

sbit LCD_RS_Direction at TRISD4_bit;
sbit LCD_EN_Direction at TRISD5_bit;
sbit LCD_D4_Direction at TRISD0_bit;
sbit LCD_D5_Direction at TRISD1_bit;
sbit LCD_D6_Direction at TRISD2_bit;
sbit LCD_D7_Direction at TRISD3_bit;

void main(){
 int x = 0;
 char txt[255];
 Lcd_Init();
 Lcd_Cmd(_LCD_CURSOR_OFF);
 Lcd_Out(1, 1, "Total:");
 Lcd_Out(2, 1, "$");

while(1){
     IntToStr(x, txt);
     Lcd_Out(2, 11, txt);
     x++;
     Delay_ms(100);
 }
}

When i add the configuration code in order to have 4 inputs in PORTA:

// LCD module connections
sbit LCD_RS at RD4_bit;
sbit LCD_EN at RD5_bit;
sbit LCD_D4 at RD0_bit;
sbit LCD_D5 at RD1_bit;
sbit LCD_D6 at RD2_bit;
sbit LCD_D7 at RD3_bit;

sbit LCD_RS_Direction at TRISD4_bit;
sbit LCD_EN_Direction at TRISD5_bit;
sbit LCD_D4_Direction at TRISD0_bit;
sbit LCD_D5_Direction at TRISD1_bit;
sbit LCD_D6_Direction at TRISD2_bit;
sbit LCD_D7_Direction at TRISD3_bit;

void main(){
 TRISA = 0B00001111;
 CMCON = 0B00000111;
 ADCON1 = 0X0F;
 PORTA = 0;
 int x = 0;
 char txt[255];
 Lcd_Init();
 Lcd_Cmd(_LCD_CURSOR_OFF);
 Lcd_Out(1, 1, "Total:");
 Lcd_Out(2, 1, "$");

while(1){
     IntToStr(x, txt);
     Lcd_Out(2, 11, txt);
     x++;
     Delay_ms(100);
 }
}

appears the follow error:

Invalid expression in line "int x = 0;"

Please, help!


texts: I want a usb system that will physically reboot my computer

texts:
I sometimes work remotely. It is a pain as my computer will sometimes crash and not reboot. I also have a second computer nearby which is more reliable.

I'd like to build a system that will press the power button on my first computer from the second. It should be able to keep the button pressed for a few seconds to ensure a full power shutdown.

I'm a software engineer with little electrical engineering experience. I'm quite comfortable with everything related to programming, but the hardware components elude me. What should I look for?

I thought of buying something like a raspberry pi and using some of the board io to activate a coil which would somehow be fitted to my pc box, but I'm totally unsure of what I'm talking about.


texts:
I would like to measure the thickness of a stack of paper without touching it. The measuring device needs to show if one sheet is removed. I do not need to know the measurement in inches. Units are not a concern here, I only need some type of reading.

What type of sensor would you recommend?


texts: USB and Battery switching circuit not working [and buck boost converter not working either]

texts:
I am an absolute beginner when it comes to electronics and this is my first circuit, so please excuse my ignorance and thank you for your patience and help.
I am trying to build a circuit which provides 3.3V power to a micro-controller (Nordic Semi nRF52840). Absolute maximum range of voltage should be 1.8V to 3.6V. Maximum power consumption would be 140mA. It should use battery power when USB is not connected and use USB power when connected (ideally without resetting). Efficiency is not super critical because I am planning to use a recharging circuit for LiPo battery if this works, but it would be ideal to get 2 weeks standby time.
I used the design in this earlier stackoverflow question by Russell McMahon and built the circuit. It worked fine when I tested with bigger components, but with a huge voltage drop. I thought using SMD components rated for lower voltages would reduce the voltage drop. But the input voltage is oscillating all over the place if I use Q2 P-mosfet (Q3 in the linked answer). If I bridge the battery Vcc directly to the buck-boost converter, I am getting a 0.95V output steady, where it is supposed to output 3.3V.
Here is the schematic of the circuit:

And here are the components used (external sites linked):

[R1,R2,R4] 1M 5% 0805 SMD Resistor
[R3] 10K 5% 0805 SMD Resistor
[R5] 100K 1% 0805 SMD Resistor
[Q1] BC807-40LT1G - 45V 500mA PNP Bipolar Transistor SMD
[Q2] SI2333CDS-T1-GE3 - 12V 2.5W P-Channel Power Mosfet SMD
[Q3] BC817-40LT1G - 45V 500mA NPN Silicon Bipolar Transistor SMD
[D33] SS34-E3/57T - 40V 3A Schottky Barrier Rectifier
[C_PWR1] 2.2 uF 25V 0805 SMD Ceramic Capacitor
[C_PWR2] 10 uF 25V 0805 SMD Ceramic Capacitor
[L1] 10 uH 0603 Ferrite Chip Inductor
[U_PWR1] LTC3531ES6-3_3 (also used the circuit mentioned in the datasheet)

And here is the PCB design

A picture of the PCB (sorry about the blurry shot):

The breadboard components I used were, without the voltage regulator,

[Q1] 2N2907A PNP Switching Transistor
[Q2] IRF9530 MOSFET- 100V 14A P-Channel Power MOSFET
[Q3] 2N2222A NPN Bipolar Transistor
[D33] 1N4007 - The large voltage drop was probably because of this.

I am looking for help on the following points:

Where am I going wrong in this circuit, why and how can I fix it? If possible, with the same PCB as I have already bought it (at 3x the cost, because of the import laws in my country).
If the circuit cannot be salvaged and I have to make a new PCB, is there any way I can supply between 1.8V and 3.6V to the micro-controller with the current PCB so that I can continue developing and testing the other parts of the circuit while I wait for the new PCBs? I do have the AMS1117-3.3V but I doubt it can manage 3.3V from a 3.7V LiPo battery (drop voltage is 1V if I read the specs correctly). I guess I could use 3 alkaline batteries as a stop-gap.

Getting very specialized parts might also be a problem because again, importing and getting parts across customs is a painful and drawn out process. But I can still try if it helps me salvage the board.
Sorry about the long post, but I wanted to be absolutely sure I am conveying exactly what I am doing. Please help me finish this project, as I am completely out of my depth and have no idea what is wrong. It has been 3 months in the going and this is a very disappointing block. Thank you for any help you can provide!


texts: Can multiple microinverters, connected in parallel to a single source, become unstable?

texts:
Just to get this out of the way, I realize that what I'm exploring is well outside the design specs for the hardware I'm using. Now that that's out of the way:

I have a large lithium battery module that I'd like to turn into a battery storage system. Ultimately, the goal is to take energy from the battery and put it into my building mains. Conveniently, I have several solar microinverters as well, but each is only capable of 250W maximum. I'd like to put them in parallel with the battery, but I'm concerned by the fact that each microinverter has MPPT capabilities (being designed for solar applications). To be clear, the battery is providing power to the microinverters.

In theory, the MPPT algorithm should optimize the load on the battery so that it matches the load impedance to the battery's source impedance. I don't know enough about how an MPPT system is implemented to understand the effect of multiple control loops acting in parallel on the same system.

I doubt this would cause problems since each microinverter is designed to self-protect, and the battery is unlikely to sustain damage from a varying load, but I am curious whether the control loops would become unstable due to their parallel operation, and how I can avoid this instability.

EDIT: Since it seems to be confusing, I've added the diagram below to make it clear how the system is connected. There are no other connections to the microinverter, meaning there is no battery charger or other DC output. There is no AC input for charging either. It is entirely unidirectional.


texts: In a Lattice MachXO2, how can I use the EFB SPI slave and configuration SSPI (multiplexing)?

texts:
I am using a Lattice MachXO2 FPGA eval board and Lattice Diamond 3.4.0.80 on Linux.

I want to use the configuration SSPI to update the FPGA configuration.  During user mode, I want to use the same SPI pins for the EFB SPI (except for SN, which enables SSPI configuration).

Basically, I am trying to follow TN1204 Fig. 12 (see below) & TN1205 Fig. 9-12 & 9-14.

I generated an SPI EFB module, added the SPI ports to my top level, and assigned the hardened SPI pins to these ports.  So far, Diamond is happy.

However, when I set the sysCONFIG SLAVE_SPI_PORT to ENABLE, Diamond's PAR tells me

  1103805   WARNING - Current SYS_CONFIG setting prohibits pin "44" to be used as user IO. This preference has been disabled.

and it moves my SPI port to a different pin.  This even happens if I only set MASTER_SPI_PORT to EFB_USER (see SYSCONFIG help).

Is there a way to multiplex the EFB SPI with the configuration SSPI, even if just  temporary (e.g. during initialization during/after PROGRAMN asserted)?  Am I missing some settings in Diamond?

TN1204 Fig. 9:


texts: Why is it difficult to develop wide-bandwidth analog-to-digital converters?

texts: How is bandwidth of analog-to-digital converters constrained? In particular, why would sample-and-hold subcircuitry not be able to perform high-speed switching?


texts: What does this circuit on my battery do?

texts:
I have a Parrot Mambo which has a very low flight time, so I would like to tether it up with some power supply. However, the battery uses 3 instead of 2 pins and i'm not sure what each of them to. I have pried open of one of the batteries, and found a circuit inside.

What does this circuit do? Is there any documentation of this circuit somewhere? I would really like to know what each of the 3 pins does, and how I can emulate them using some external power supply.


texts:
So what is the difference between sr latch and level sensitive sr latch??

For sr latch, When 00, they just store the previous bit and when they are 01, the output q becomes 0, which they reset and when they are 10, the output q becomes 1, which they are set.

For example, if I have this level-sensitive sr latch:

how is the behavior different from the just regular SR latch??


texts:
I have to design simple PCB that will measure current by shunt resistor(R7, R8, R9) and voltage by divider. Board has 3xin and 3xout for different voltage/current specifications. I have the following questions:

Can I use the same signal GND for all inputs and outputs? For me it is obvious to use the same, but I see some other design, that I a little bit inspired by and there he separate GND of inputs from outputs.
Should I create polygon of GND an top layer?
Should I add some capacitors to current sensing tracks, beacause there are 3 pairs of current sensing traces and they go to header and goes to ADC on the other board.

I attached pcb layout and altium files.


texts: Designing a BLE reader to detect nearby bluetooth beacons

texts:
I am new to this Bluetooth beacons and I'm trying to create a project where multiple BLE beacon readers are installed in a yard which detect the beacon modules and helps to locate the location of each module.

Most solutions online suggest using a mobile phone or pc as the reader but that would increase cost. I have seen projects using raspberry pi but I want to design a reader with something basic as an STM32F0 microcontroller.

So my doubts are if I use beacon such as Gimbal series 10 as my beacon which prefers ibeacon which module should I use for my reader( requirements of the BLE module).

Can i use some modules like HC-05(or maybe something which supports Bluetooth 4.0 or BLE) to continuously scan for nearby Bluetooth devices.

If my choice of beacon is wrong which low cost beacon can be used for this project.

hope i was able to convey my idea.Thank you in advance.


texts: We can ignore the wire resistance if the current delivered by the wire is low?

texts:
In this question asking about the Resistance of wire, the answer by user 比尔盖子 provided the following explanation for When Resistance Can be Ignored:

  Most of the time, resistance of a wire is too low when you compare it to the resistance of other components and loads, so it's negligible and often safe to ignore. Moreover, \$ V = IR \$, the lower the current a load needs to take, the higher its equivalent resistance, so you also ignore the wire resistance if the current delivered by the wire is low, because it's equivalent to connecting a small resistor (a wire) to a large resistor (a device that takes current) - almost no effect.

The first idea is clear to me: Most of the time, resistance of a wire is too low when you compare it to the resistance of other components and loads, so it's negligible and often safe to ignore. However, the second idea is unclear to me; specifically, the idea that, because \$V = IR \$, the lower the current a load needs to take, the higher its equivalent resistance, and so we can ignore the wire resistance if the current delivered by the wire is low, because it's equivalent to connecting a small resistor (a wire) to a large resistor (a device that takes current) - almost no effect. If \$V = IR \$, then, \$ V \$ being constant, a lower value of \$ I \$ implies a larger value of \$R\$ -- a larger resistance. But I don't understand why this implies that we can ignore the wire resistance if the current delivered by the wire is low.

I would appreciate it if people would please take the time to clarify this.


texts: Current monitor shows overload even for small load

texts:
I have a current-shunt monitor using INA202 between a 5V power supply and loads. The current monitor should turn off a MOSFET switch and disconnects the loads if the load current goes over 150mA.

I have problem when I connect one of the loads. It is an accelerometer (which should consume only 350µA), powered via a 2.5V LDO regulator. Whenever I connect it, the current monitor shows overcurrent and disconnects the loads. But it doesn't happen if I first connect the accelerometer and then power on the power supply. Also it doesn't have the problem with other resistive loads.

I solved the problem by putting a resitor and zener diode, making a 4.3V regulator, in front of LDO. Although it solves the problem, I didn't understand what was causing the problem. I would like to know what could be the cause.

Edit: Here is the rough circuit:


texts: Connecting Basys 3 to my MacBook pro 2019

texts: I'm an electrical engineering student who is learning to code VHDL using Vivado, I have encountered a problem connecting my Basys 3 to my computer. Since my computer doesn't have any USB 3.0 output I have to use a USB hub that converts my USB-C to USB 3.0 . When I open HW manager in Vivado it doesn't see my Basys 3. How can I solve this problem?


texts:
How can I solve for V0 on the next circuit if Z1 = 1, Z2 = j, Z3 = -j.

All the ways I'v tried, V0 depends ends depending on V0, maybe using superposition theorem?

Attempt 1: ( Calculating current through Z3, and use a current divider to get the current through Z1 or Z2, then multiply times the impedance used.)

Attempt 2: (Using net analysis for determining I1, I2 and I3, then multiplying (I2-I1) * Z2)

I need to measure what 2V0 is to solve for the impedance of the 1A source, Thanks!


texts: In the solution presented I have doubt regarding the 3rd region where both Mos are in saturation.When M2 shifts from triode to saturation how can we say that that the Vout will still be increasing?Isn't it only possible if the (Vgs1-Vth1)>(Vgs2-Vth2)?.Otherwise the current in the 2nd MOs will be dominant and Vout will decrease.Please explain.[Note: Vin varies from 0 to Vdd=3V.Nothing is said about Vb].


texts: Meaning of discontinuity in a diode circuit, analyzed using a simplified model for the diode

texts:
In our microelectronic circuits class we have been taught about the following simplified model for the diode,
\$(v_D < V_k \implies i_D = 0) \land (v_D = V_k \implies i_D > 0)\$
where \$i_D\$ is the current on the diode, \$v_D\$ is the voltage across it and \$V_k\$ is its knee voltage (neglecting the breakdown effect). We usually use this model for quick pen and paper calculations, which our teacher sometimes doesn't do, however.
I was reviewing one (basic) circuit the other day, which is one of those for which the teacher didn't do all the calculations during the lecture. The LTSpice schematic of the circuit is the following:

The voltage on the capacitor is initially 0, and the input voltage is \$v_{in}(t) = 3sin(2\pi 50t)\cdot1(t)\$ (of period \$T = 20\$ \$ms\$). By applying KCL, KVL, etc. I quickly got the equations
\begin{equation}\tag{1}
v_{in}(t) = v_D + v_{out}\end{equation}
\begin{equation}\tag{2}i_D = Cv'_{out}\end{equation}
where \$v_{out}\$ is the output voltage, and \$v_{out}'\$ is its derivative.
When the diode is forward biased, I get
\$
\begin{equation}
\tag{1F}
v_{out} = V_{in}(t) - V_k
\end{equation}
\$\begin{equation}
\tag{2F}
i_D = Cv'_{out} > 0
\end{equation}
When the diode is reverse biased, I get

\begin{equation}
\tag{1R}
v_{out} > v_{in}(t) - V_k
\end{equation}
\begin{equation}
\tag{2R}
i_D = Cv'_{out} = 0
\end{equation}
The result of the LTSpice simulation is the following:

During the lecture, our teacher, who didn't do the calculation explicitly, asserted that, from time \$T/4\$ onward, the output voltage is constant because the capacitor cannot discharge, which is only approximately true: the diode appears to conduct a small (but of greater order than the saturation current of the diode) amount of current in certain instants. When looking at the simulation for the first time, I thought that this discrepancy was because we were using a simplified model.
However, by the direct calculation using the simplified model above, I found out that, for time instants \$t_h = T/4 + hT\$, where \$h > 0\$, the diode is not forward biased or reverse biased: if it was reverse biased, \$v_{out}(t_h)\$ would be equal to \$v_{out}({t_h}^-)\$, as its derivative would be constant. However, (2R) would not hold, as \$v_{out}({t_h}^-) = v_{in}(t_h) - V_k\$.
On the other hand, if (1F) were to be true, \$v_{out}\$ would have a maximum in \$t_h\$, thus making (2F) false.
Since the only discontinuity in the diode model happens when it switches on / off, I assumed this means that in \$t_h\$ it is switching on and then off (because after this instant the diode turns out to be reverse biased again). The simulation also confirms this.
The question is: in cases such as this one, when using the simplified model above, I find some instants for which the diode appears not to be in any state, can I assume that it's in the middle of switching on/off? Or am I relying too much on a simplified model?
Thanks.


texts: Is it healthier for a capacitor to be discharged to itself or to "ground"?

texts:
A practical-use question from a non-EE who enjoys simple repairs of home electronics. Am curious about whether "where" to discharge makes a difference to the continued health of an electrolytic capacitor - and for caps still in-circuit on a PCB also to the health of its neighbors.

A brief web-search yielded: some discharge 1) directly across the terminals, 2) from cap to "ground" (metal case, or ground pin of the power plug), or rarely 3) from cap to "ground" (the earth). (And most do use a resistor to slow things down.)


texts: FPU vs. Fixed point multiplication/division speed

texts:
Is fixed point multiplication/division still faster than floating point operations when a FPU is present? Is there any situations where this might change? For example under very heavy floating point calculations? Why have more than 1 FPU?

I am thinking specifically about the ARM platform Thumb/Thumb 2 instruction set or similar.


texts: How are multiple signals propagated in a coaxial cable?

texts:
I am reading that coaxial cables can carry hundreds of MHz signals at How Stuff Works. How are these signals propagated and how are they deconstructed once they reach their destination?

One idea that comes to my mind is that the RF signals of each frequency are translated into voltage waves that are then superimposed onto one, thereby creating one electrical signal that is sent through the cable. At the destination this signal is deconstructed using some form of correlation, to get the corresponding frequency?


texts: Three way set associative cache with LRU replacement

texts:
So I am going through a homework exercise, and I am not understanding the solution to the problem. We are given a sequence of memory references and we are to use a three-way set associative cache with two-word blocks and a total size of 24 words. (For reference question is here). According to their solution, the offset is 1 bit, index is two bits, and the tag is the remaining bits.

First, to make sure I understand, there are four sets because each set contains 3 blocks (three way set associative), and there are a total of 12 memory references, so 12/3 = 4 sets, so the indices in binary would be 00, 01, 10, and 11 each with three "slots" for data.

Second, the memory references are from another problem where it is stated that the references are given as "word addresses". Does this mean that they are word addressable, not byte addressable? If so, I thought that since the cache has two word blocks (8 bytes) then the offset would be 3 bits (2^3)? What is the significance of having two-word or one-word blocks?

My main difficulty is understanding how offset bits are calculated in different cache mappings. I understand the replacement method in that the last recently used element is the one to be replaced by an incoming element.


texts: Does it matter where we measure the Voltage in a large-scale, industrial installation?

texts:
So, let's say we have a big shop floor with several 3-phase, high power consumption machines being far apart from each other. If we measure the mains voltage at one of the plugs, could this be used to accurately calculate the consumption of each of the other machines, just by measuring their current?

What I am trying to understand is whether we can have a non-intrusive distributed power consumption monitoring system like the Open Energy Monitor, where the instantaneous voltage is measured at a single point only and then multiplied with each of the currents to get the instant power consumption.

I have the belief that in an industrial environment, this would not be accurate due to longer distances between the appliances, bigger voltage spikes and higher inductances of the transfer lines. Am I right?


texts: Center tap transformer with full bridge rectifier, number of rectifiers

texts:
I have a center-tapped transformer which outputs 12V-0V-12V. I was wondering what is the differences between using one full bridge rectifier and two to generate a positive and a negative DC rail.

Consider this schematic:

It uses one full bridge rectifier and uses the center tap directly as GND.

Consider the second schematic (smoothing caps omitted):

Besides from using more diodes, what are the differences between two approaches?


texts: I need 5V, 12V, and 30V power supplies for an RF front end tuner.  I'd like to power them with a single AC adapter, either 12 or 18V.  Obviously it needs to be pretty clean to function with RF.  The tuner + power supply will be on a single PCB with a ground plane.  I'm mostly concerned about getting the 30V supply.  How should I go about this, and what design considerations should I pay attention to?


texts: Stepper Driver/Motor Voltage with Regulated Power Supply (Arduino)

texts:
Let me first say I am VERY new to electronics, so I apologize ahead of time (I'm very active on StackOverflow.com, so I understand).  I have the following components I'm attempting to control with an Arduino Uno:

42BYGHW609 NEMA 17 Stepper
DQ420MA Microstep Driver
12V-36V Regulated power supply

All components are listed here:  at Ebay

My question: Is it safe to connect this regulated power supply directly to my driver and the driver to my motor?  The motor is rated at 1.7A and 3.3V but the driver has 12V in.  Is this a safety hazard?  Do I need to do something to lower the voltage to the motor or does the driver handle this?


texts: Disconnected laptop's internal mic, but sound-card is still picking up sound, why?

texts:
I have a HP Mini 5103. A security minded friend wanted me to physically disconnect the internal webcam and stereo mic, no problem as both are individually connected to the motherboard via a wire harness. I unplugged both.

After this simple modification, I decided to verify that no sound was being recorded, so I hit record for a few seconds in Audacity. At first it only seemed to be recording white noise, sounds in the room weren't captured, which is what I expected. Then I tried tapping the laptop, and suddenly spikes of activity showed up in the recording with each tap. Playing it back, the taps can be heard relatively clearly.

Is it possible that the sound card's circuitry is sensitive enough to be picking up these vibrations without a mic? My initial suspicion was that there was a third mic, maybe just for low frequencies, but I couldn't seem to find anything else on the motherboard. HP only lists the stereo mic on their major parts list: https://support.hp.com/us-en/document/c02492286


texts: Mesh Analysis with only current source.?

texts: **Can we use mesh analysis and get current in 1ohm resistor....and is not then why? **


texts: I am studying the effect of a diode rectifier on the mains. When I started to increase the inductance, the current had less distortion but the input voltage became more distorted. When I looked at the FFT analysis it had allot of 3rd order harmonic content. So is my understanding correct in saying that by designing a 3rd order filter by placing a capacitor in parallel with the inductor on the input, then it can reduce the distortion of the voltage at the input ?


texts: Non-Inverting Single Supply comparator hysteresis is too wide

texts:
I am trying to convert an input sine wave to a square wave. The sine wave is centered at 2.5V and has an amplitude of 200mV, with a frequency of 100kHz.

I am looking for a hysteresis of 100mV centered around 2.5V. (ie. 50mV below and 50mV above 2.5V)

I am trying to achieve something like the following , where both waves are centered about 2.5V:

To do so I looked through Design with Operational Amplifiers and Analog ICs, and I thought that I could work with a VTC offsetting single-supply inverting Schmitt trigger.

I then calculated the resistance values according to my parameters.

VTH = 2.55V
VTL = 2.45V
VCC = 5V

Where I get:

R1 = R2 = 1kΩ
R3 = 1kΩ
R4 = 50kΩ
R5 = 100Ω

Testing this on proteus:

yields undesired results:

I was expecting the hysteresis of 100mV and not 200mV.

On closer inspection, VTL is  2.4Vand VTH is  2.6V. This can be remedied by increasing R4 while keeping R3 constant. I would like to know why my initial calculations were incorrect.

Any suggestions on what I may be doing wrong would be appreciated.


texts: Solid state device for switching (muxing) a bipolar high current signal

texts:
I'm looking into solid state relays for an application where I need to switch between two different transducers to allow two different modes of operation for an echo sounder. Basically a MUX that allows selecting either transducer #1 or transducer #2.

Short overview of how an echo sounder works: the echo sounder generates a short pulse (1-10 ms, 60 Vrms) which is emitted through the transducer. Then afterwards the echo sounder goes into listening mode receiving the returned echo which reflects of objects and the bottom as it travels through the water column.

Developing a MUX has some challenging requirements for this kind of signal:

transmit requires a relatively high voltage signal to pass through (max 60 Vrms sinusoid of 1-10 ms duration), whereas when the echo sounder is listening it will receive a signal which has a low amplitude (< 10 mV).
The signal should pass through without distortion (close to linear transfer curve).
The received signal should not be colored by noise (high S/N ratio, > ~90 dB).
Signal is bipolar.

Is this even possible with SSRs? A better device? With solid state relays I'm wondering if a device capable of relatively high current will not perform well for low signals during receiving (non-linearity or too noisy). Of course a mechanical relay would solve all these but might not last as long if switching frequently and reliability is important (i.e. years).

Assumptions: Both transmit and received signals have no DC component. Transmit is a pure tone of e.g. 35 kHz. The received signals will be more wideband, but will be bandpass filtered in the receiver. The switching between transducer 1 and 2 can be restricted to only occur when system is turned off. Transducers are ceramic. Impedance of transducer at transmit frequency is on the order of 1.5 kOhm. Assume max 40 mA inst. current during transmit pulse. Assume there is no ringing in existing circuit as transmit pulse has smooth envelope (ramp up/down). The transmit circuitry is only connected for as long as the pulse is transmitted, afterwards the receiver is connected and listens until the next transmit ping.


texts:
is there any known type of device will do the following:

[I have read the bi-directional potentiomenters posting LINK but I just joined and can not reply to that posting.

I am looking for a rotation rheostat/potentiometer to control a 110v 25w lightbulb.

top-dead-center [slider at top-dead-center] = bulb at brightest
rotate-clockwise = bulb dims [no need for a full-off clockwise position]
rotate-counter clockwise = bulb dims [no need for a full-off CCW position]

My chiropractor son and I are trying to make this device YouTube LINK on our own

The left bulb is always on [simple SPST switch]
The right bulb dims if the plastic spine is rotated right, or left, from the dead-center [full bright] position

Thank you for your considerate assistance & recommendation.

Jim [Mech-Engr & tinkerer, with very little EE knowledge so please dumb-down your answer ]


texts:
I have read that transistors (especially in common emitter mode) have an effect called "early effect" in which increasing the collector to emitter voltage (Vce) increases the collector current and doesn't let it saturate. Now, the reason that is given for the explanation of this effect is that increasing the collector to emitter voltage effectively reduces the base width by increasing the depletion width of collector base junction. This in turn improves the emitter injection efficiency and leads to higher emitter current thereby increasing the collector current.

My question is why is the same effect not seen in the case of a common base configuration when we increase the collector to base voltage? There also the emitter current increases with increase in C-B voltage. The increase in Ie should result in an increase in Ic therefore. Still, how does the collector current saturate at a particular value (before the punchthrough region)? How does it make sense to draw a curve of Ic vs Vcb for different Ie (output characteristic) when Ie itself varies with respect to Vcb? Or another question would be why is the early effect more prominent in common emitter mode as compared to the common base?


texts: How to run a circuit with both 5V and 3V3 supply voltage?

texts:
I'm currently designing a circuit requiring 3V3 (an ARM MCU) which should run on both 5V and 3V3 input.

Since the power requirements are fairly low, a linear voltage regulator should suffice.

I want to use L78L33 but I cannot find information regarding the voltage drop and minimum voltage requirement. Especially the graphs on page 26 only specify output characteristics of L78L05/12/24 but not L78L33.

Which regulator can be used to provide 3V3 with input voltage as low as 3V3?


texts: When two conductors separated by dielectric it acts as a capacitor,in my case tranmission lines are current carrying conductors and they are separated by dielectric material(air)and it acts as capacitor.suppose it carrying 4ookv(line) then according to modified amperes law differential current will flow through air(dielectric medium) in form of electrical flux but we are not getting shock why?if it is dangerous in what cases?


texts: Do I need OD/OC/OV Protection for Small LiPo Batteries with a Protection PCB already?

texts:
I'm building a small design that is designed to only take smaller LiPo packs, those that often terminate in a JST PH 2.0 connector with example below:

It seems like most of these similar batteries I find online already include some form of protection circuitry in the PCB behind the Kapton tape. Currently, my design includes a FS312F-G battery protection IC in series, for overdischarge, overcurrent, and overvoltage protection.
Will this IC interfere with the protection already on the batteries in any meaningful way? If not, can I just get rid of this IC entirely instead, if the onboard protection PCB already does the same thing?

It's important to note that in the physical design, there is almost no physical way for a user to actually connect an unprotected 18650 [or other common cell], unless they go about soldering a JST connector on and dremel out a large hole for one. If that battery blows up, that's on them-problem and don't want to increase BOM cost for unintended use cases.


texts: I used led calculator and it gave me a different solutions, in one of the solutions says " the array draws current of 100 mA from the source"

texts: With another solutions mA just goes up, 125 mA, then 175 mA, 250 mA,I want to know which solution is best,the one that draws less mA will be best?


texts:
I'm confused about two different approaches for current calculation through a 5 ohm resistor.

The 5 ohm resistor is in parallel with a voltage source so the current through it should be 2 amperes.

In a parallel connection, current follows the least resistance path, so all the current flows through the short circuited path (since its resistance is zero) and current through the 5 ohm resistance will be zero.

What will be the actual current through the 5 ohm resistance and how should I approach this problem?


texts: What could be the reason if the AC coupling option goes away when I attach a differential probe (P6248) to a Tek MSO5204 scope?

texts:
When the scope is not attached, I could see both AC coupling and DC coupling options for the  channel settings. The moment I attach the differential probe, the AC coupling option goes away. Any reason?
This was part of an experiment to measure the ripple of a voltage regulator output.


texts:
I am using MCP4728 DAC which I am controlling nicely from the microcontroller. On its output I have connected the op-amp in buffer configuration(non-inverting input is the signal from DAC, inverting input and output are connected together), all powered with 5V on positive rail and gnd on negative rail. Op-amp part is AZV321(rail-to-rail).

Output of buffer op-amp goes through two more stages of amplification which end up in the base of darlington transistor. So, a little current is needed from the buffer.

What happens in my case is that when I connect the circuit, only the connected DAC channel stops working - it doesn't give any voltage out anymore.

I find it hard to understand what happens. From my understanding, op-amp is correctly connected and there shouldn't be any problems. I have tried switching DAC & op-amp, in case I have soldered then wrong.


texts: Prevent bit-bang data-in line from back powering device?

texts:
I'm building a Z80 machine from components, to talk initially to a PC via bit banged I/O through an FTDI USB cable, and I've little idea how best to avoid back powering the Z80 board from a 5V data in-line. Z80-to-PC data is working nicely, the reverse otherwise. I am a neophyte at this, from a coding background.

(Not shown above, I've also had to add a hacky N4148 between U1 and the data bus line.)

The issue arises when I want to receive bits on the Z80 machine, sent by the PC:

Powering down the Z80 machine, it remains semi-powered from the 5V data line from the PC. I've spent hours and much searching trying to understand this. Most of the internet seems concerned about safely back powering Raspi and Arduino, but there were some finds:

Culprit: This seems to happen via my U1 AND gate: the SN74HC08N data sheet shows Absolute Maximum Ratings for input "clamp" current as (should not exceed) +/- 20 mA outside the voltage range 0 to VCC, VCC being 0 here (power off), which I gather means it can be inadvertently back powered from inputs. So current to the U1 AND's input is exiting via VCC line, back powering the board.

Fixes I can see/have tried:

Putting a second N4148 or better on the U1 AND gate's VCC to cap back powering at small mA. Tried, hides/solves the problem, but I can't imagine this is right?
Use a MOSFET/BJT to attempt to drive U1 only from VCC, sending FTDI data in to the gate/base. I'm not skilled enough to know whether this is any more correct than a diode.
Op-amp plus MOSFET (as in a related but distinct question) - I can follow along but is this really the usual way? This doesn't feel like a standard approach for a little 8 bit machine, but perhaps I'm dead wrong.
Opto-isolation - this comes up a lot in answers from what I can see, but I'm not aware if this is standard practice for your average consumer device? Was every common 8 bit RS-232-capable microcomputer really opto-isolated? Schematics I've found seem to simply use the MAX232 or equivalent, but I can't work out how that helps.

How in your experience does one tend to avoid this when designing such circuits?


texts:
Can anybody explain why Carry-Skip adder has the same critical path as regular Carry-Ripple adder. My textbook says that critical path occurs when carry is generated in LSB and then propagating it through the remainder of the adder. The way I see it, critical path occurs when each stage has to either generate or kill carry, therefore every next stage has to wait for the ripple from previous stage to get the sums. All sites are saying that my textbook is correct, but none of them explaining why. I would appreciate any help.

BTW Carry-Skip adder is the same as Carry-Lookahead adder but it doesn't calculate group generate signal.


texts:
simulate this circuit – Schematic created using CircuitLab

My current understand is, for superposition (V1 and V2 acting alone) to be used in the circuit above to calculate the energy dissipated over a given resistor, the following must apply:

$$\int_{T_1}^{T_2} v_1\cdot v_2 \cdot dt \equiv 0$$

Is there an equivalent for current sources, i.e. replacing V1(t) and V2(t) by I1(t) and I2(t)?

P.S. Is that last dot product (with dt) a typo?


texts:
I was measuring current through shunt method. below is the SCH and waveform captured. PB5-AI will to ADC which has max 1 Volt limit.

Waveform capture across R30

So why this much noise on output waveform, and when i reduce time scale of same waveform i observe spike on waveform(see picture), I tried to add 0.1uf cap across R30, but not helped. any suggestion
I doubt with this much noise my ADC will not capture it.


texts: Why is there need for both functional validation and LBIST during Post-Silicon?

texts:
In Post-silicon testing, we have a functional validation testing where C tests are developed to verify the functionality of the SoC, through a JTAG interface connected to the PCB TAP and controlled through some software like Code Composer Studio.

Also, there is structural testing where different types of fault models are tested like stuck-at, bridging, gate delay, path delay etc through Built in Self Test logic and some through ATE.

My question is, why two levels of testing are required? If a module deep inside the core has some fault, isn't functional validation sufficient to detect the error?


texts:
First of all here's the datasheet for the IC, a dot/bar display driver.

What I'm confused about are the following pins: 4,6,7,8

The datasheet mentions a 1.25V reference source. Is that built into the IC so that no matter how I configure it there is a 1.25V source there? From what I can see, this involves pin 7 and 8 (REF OUT and REF ADJ). Assuming pin 8 is connected directly to ground, what does this do? If I increased/decreased the voltage at the REF OUT pin 7 what changes? I understand that the LOAD at pin 7 determines the brightness (through current draw) but I don't understand what the voltage at pin 7 does.

The next two pins I'm confused about are 4 and 6 (RHI and RLO). They seem to be connected in series with the 10 1k resistors. Assuming RLO is connected to ground, as I decrease/increase the voltage at RHI, what happens? From looking at the block diagram, it looks as if the "LED Steps" are directly proportional to the voltage at RHI. Does this mean for instance, if RHI = 1V then every every 100mV from the signal source will turn on another LED? So 200mV = 2 LEDs, 400mv = 4 LEDs etc..? And if I put 3V at RHI would it behave similarly?

EDIT:

So in the schematic example they're connecting REF OUT to RHI which is why they say in that example each comparator would activate every 125mV? Does that mean I can connect whatever voltage I want there or do I have to use the reference voltage? Regarding resistors R1 and R2 connected to pin 7 and 8, I see that equation gives you the VOUT. But what's the point of VOUT? Why am I bothering to use a resistor divider between those two pins? Is it just to control LED brightness? If so why would they have two resistors instead of just 1?

What also confuses me is in the figure above they call it a "0V - 5V Bar Graph Meter." With a 0-5V signal source. If there were connecting REF_OUT directly to RHI as they do in that diagram, wouldn't the max voltage display be 1.25V? At that point wouldnt all the LEDs be on? So why do they call it a 0-5V bar meter? I notice they connect the signal source to RLO as well. What's up with that? Wouldn't you normally connect it to ground? Wouldnt your voltage across the "resistor ladder" constantly be changing if you connected RLO to the signal source? What's going on here?

It also looks like I connect the LEDs directly to the V+ source from the diagrams as well? This seems strange to me. For instance, what type of voltage to I need to hook up as VLED?


texts: Using a transistor instead of a relay to control a DC motor

texts:
I've made a simple relay circuit to switch power to a small DC motor

Here is a diagram of what I got right now:

Is it possible to replicate that with a transistor. Which one would be a good choice?


texts:
Hi When calculating the pull up resistor value using the formula R = 50 / d, where d is the number of devices on the bus, is the master considered a bus device?

for e.g. If I have a micro controller master and two slave devices on the bus should this count as a total of 3?

For extra credit: Am I using the right formula? if I use 3 as number of devices this tells me I should use 16k6 pull-ups, which seems high...
Ta


texts: JL1N PLC re-purposing for home automation

texts:
I own a JL1N-20MR (supposedly FX1N-20MR clone) based on STM32F103RCT6 CPU.

I figured that I might be able to re purpose this PLC for home automation by altering it's firmware to use something more IOT oriented. Do this instead of creating my own hardware design since this board has everything I need.

I don't have experience in hardware reverse engineering, nor in programming STM32. However I am experienced programmer with reasonable understanding of electronics. I did a number of successful embedded hardware/software projects in the past.

I am searching for hardware documentation or anything that could help me start working with this board.


texts:
I have a PCB designed using both 10Mbit and 100Mbit Ethernet, I have produced 100 boards 97% of which work perfectly (both 100Mbit and 10Mbit). On 3% of my boards the 10Mbit operates all the time, but the 100Mbit fails on some interfaces. For example I have two Ethernet ports from my PC, one from the motherboard and a second PCI-X Ethernet card. On the motherboard port all devices operate correctly. On the PCI-X based port 10Mbits works and 100Mbits doesn't. The PCI-X Ethernet device obviously works for the 97% of the devices. If I use a switch between the PCI-X port and my device 100Mbit works all the time.

I'm concerned that I have a problem with my Ethernet interface causing it to be marginal. Has anybody seen this before or could somebody offer some hints of where to look for the problem?

UPDATED

I'm using the Micrel KSZ8041 Ethernet PHY.

When I find a failing PCB it doesn't work with other designs I have which I know are in spec (although thanks this was a good suggestion).

Here are my schematics:

On my failing units I have

Removed the ESD protection.
Added 1uF on the transformer center tap.
Adjusted all the filtering components.
Swapped most components between a working unit and a failing unit except the PHY and DSP.

My connector P300 is not an RJ45, instead it is a 2mm through hole header where a custom wire loom connects to an RJ45 on a separate PCB. I have excluded this header and the separate PCB from the equation by wiring directly to P300.

Not sure if it makes a difference but this works with a longer Ethernet cable (5m is okay 0.5m is not).... which points to the matching components/layout. I've reviewed the grounding.

On the inside of the transformer the tx & rx are balanced and on an internal plane between two ground planes (the tx & rx pair are tightly coupled together (9 mils separation) and good spacing between the pairs & other tracks (at least 40 mils). On the outside of the transformer the tx and rx pairs run over a separate chassis gnd plane.

I'm convinced the problem is between the PHY and the outside world (not excluding the PHY). When I probe the rx0 line between the PHY and the DSP a working unit shows only traffic when I ping, but a failing unit has a constant stream of data (presumably idle characters incorrectly received).

I'm currently investigating renting some compliance testing equipment.


texts:
I have a PC intended to be powered by 12VDC in a car.

I wish to operate the PC from the AC mains at home. To do this I will need to connect it using a plug as shown below, and I will need a converter or other device to power it using AC mains power. (I don't know the correct name of such a device so I don't know what to search for.)

I'd appreciate it if somebody could tell me what I should be looking for and perhaps show me an example on ebay or a similar site so I know I have understood correctly - assuming it's possible to do what I want.

Thank you

EDIT:

So here is the one copy/paste from manual:

  The AR-V6002 power subsystem converts the external DC input from vehicle to stable power rails for internal mother board, peripherals, and external I/O. The power subsystem  can be configured by either an onboard switch SW1 or software to support various power  off delay time. There are 9 power modes available for your application.
  2.3.1 Definition:
  1. Ignition: Ignition is a voltage input to command the power subsystem start a power on  and off cycle. It is treated as ON when voltage is above 1.1 Volts and OFF as voltage  is below 1.1 Volts. The maximum voltage input shall below 32 volts.
  2. Remote Switch: Remote switch input is a Open/Close latch switch. It is an optional  function when the power mode is set as Mode 2, 3 and 4. When you set the power  mode as 5, 6 or 7, it works with ignition to power on or off the system. It will be treated  as ON when the switch is CLOSED. It will be treated as OFF when the switch is  OPEN.
  3. Soft Off Delay: This is the delay time after ignition or remote switch is OFF till power  subsystem sends a turn off command to the motherboard. If ignition or remote switch  is turned ON again during this period, the power subsystem will cancel the OFF  procedure and back to operating condition.
  4. Hard Off Delay: This is the delay time after power subsystem detects the OS has been  shut down till the standby power is turned off.

And this is a LINK to an actual product it has datasheet so maybe you will find all the information there.


texts: How can I implement a digital clock in Logisim?

texts:
I'm trying to simulate a 12h-digital clock in Logisim. Here's the logic diagram:

I could simulate BCD to 7 Segment but I don't know how to create a CTR DIV 10 and CTR DIV 6 in Logisim, so I tried to look into some logic diagram and found this:

By the way, here's the structure of the CTR DIV 10 but I don't understand how it works:

And here's my approach to this implementation:

Any help to simulate this, thanks in advance.


texts: Highest energy density electrolytic capacitors

texts:
I'm building a project that involves discharging a fairly large capacitor through a pair of electromagnetic coils. It's electrically very similar to a coilgun, though for a different application. I can't use a supercapacitor because their power density is not high enough, and so I need to find the electrolytic capacitors with the highest energy density, because I'm limited to around 80g for the capacitor.

At approximately what maximum voltage do standard aluminum electrolytic capacitors have the highest energy density? I can design my coil and flyback transformer around the capacitor voltage if there is an advantage to higher voltages, but if they're all approximately the same, I think the electronics would be easier with a 35V cap than a 200V one.
Is there a site or a manufacturer who has a list of capacitors with the energy density for each one? It seems like a feature Parts.io or a similar site would have but I can't find it anywhere. The way I'm doing it now, I have to find the package size for each cap in the datasheet, and then find the weight of that package size and calculate energy density, which is getting rather tedious.
Should I be looking into another capacitor technology instead of electrolytic? I'm having a hard time finding tantalum capacitors this large, and the ones I do find have specs similar to the electrolytics.


texts:
I have created a custom part, starting from a generic DIP 8 IC.
I have increased the width of the component using inkscape, but now I have this situation where the connection points / terminals are not shifted properly to the right. I guess these are still in the original location.

How can I fix this?
I have now modified the svg file in
C:\Users[username]\Documents\Fritzing\parts\svg\user\schematic\MCP2551_25828293fcd6bb68e17b63fa536d7d1d_3_schematic.svg

In what file are these terminals described?


texts: Arduino code compiles both on Eclipse and on AVR Studio 5, but only Eclipse version is functional

texts:
I'm trying to choose an IDE for arduino development. I installed both Eclipse and AVR Studio 5. And configured them using the instruction on the Arduino site (for Eclipse) and those two tutorials (AVR Freaks, EngBlaze) for the AVR Studio.

I've written a simple project in Eclipse. The code compiles and work as expected when uploaded to the Arduino (Atmega2560). I then used the same code and created an AVR Studio project.

On AVR Studio my code compiles just fine (so it seems) but when I upload it to the board (using the same avrdude configuration) the board only flashes the L led (pin 13) at a what seems like 1 second rate.

Ideas anyone?


texts: Is it possible to access semantically connected registers generically?

texts:
I have an SPI module which has an initializer function:

static volatile uint8_t *registerOut, *registerIn, *registerDir;
static uint8_t clock, dataIn, dataOut;

void SpiInit(volatile uint8_t *pRegisterOut, volatile uint8_t *pRegisterIn,
             volatile uint8_t *pRegisterDir, uint8_t pClock, uint8_t pDataIn,
             uint8_t pDataOut)
{
    registerOut = pRegisterOut;
    registerIn = pRegisterIn;
    registerDir = pRegisterDir;

    clock = pClock;
    dataIn = pDataIn;
    dataOut = pDataOut;

    /* access registers */
    *registerOut |= (1<<dataOut) | (1<<clock); /* set dataOut pin and clock as output */

    /* etc. */
}

An example call would look like this:

SpiInit(&PORTB, &PINB, &DDRB, PB2, PB1, PB0);

Now I wonder if there is a way to not having to pass all the registers which are semantically connected (PORTB, PINB and DDRB). I would like to pass only one reference PORTx and somehow derive to its connected registers PINx and DDRx.


texts: design: low voltage clamp circuit (0-200mV)

texts:
I need a active safety circuit to clamp voltages to the range of 0-200mV, independent of temperature and very precisely.
I have simulated, using TINA-TI, 4 precision clamps in series to do this, see design below:
the first two precision clamps ensures the lower clamp voltage and the last two ensures the top clamp voltage. There is an offset for some reason if the buffer is not included.

However, this is a very component heavy design, and I'm wondering if there is a simpler method? Thanks for reading.

Edit: Ideally I'd like the full swing (0-200mV) with precision to 0.001V. The input will come from a DAQ with -10~10V swing. Also, the load is around 50 ohms.


texts:
I did simulations with the PA107 amplifier from apex and now I want to go to the creation of PCB.
For the simulation I downloaded the lib of the amp and I created the symbol.
On the other hand for the creation of schema on PADS, the software that I will use for the creataion of PCB, I can not put the amp on this software.
How could I do that?


texts: What common factor could be causing wrong voltage on both rails of this PSU?

texts:
I'm trying to figure out why the 43/-43V rails in this PSU are actually reading 41/-41V.  I'm presuming that it must be due to a single shared component that is out of spec, but I'm not sure what.

I suspected the zenner diode, but the voltage across that is 15v, as it should be.

I've ruled out supply voltage issues, as the voltages remain at 41v regardless of whether supply is slightly too hight or slightly too low.

Attached schematic below.  Please ignore the unregulated parts of the supply (coloured).


texts: Three opamp instrumentation amplifier vs single opamp implementation

texts: I read in a book three opamp instrumentation amplifiers are better and they are more common, but why is it better than the single opamp instrumentation amplifier? It must be more expensive as they have  two extra opamps.


texts: Trying to understand FIFO in hardware context

texts:
Wikipedia defines the FIFO in electronics as under:

  FIFOs are commonly used in electronic circuits for buffering and flow
  control which is from hardware to software. In its hardware form, a
  FIFO primarily consists of a set of read and write pointers, storage
  and control logic.

I understand in hardware what is storage and what is control logic. But in this definition I don't understand the meaning of read and write pointers
Is this simply a kind of Program Counter?