texts: What is the difference between processor clock and system clock?

texts: In the TM4C123G Launchpad Workshop page 129, there is a note about power modes. This note differentiate between processor clock and system clock. So what is the difference between them ? Is this a general concept or is it specific to the TM4C123GH6PM micro-controller ?


texts: Why do Rogowski coils work for measuring current?

texts:
Rogowski coils measure current by completing a loop of coils around the conductor seen below.

This makes sense, but question 1: This is a current transformer, and transformers couple, so in this system when the Rogoski coil couples with the measured wire, does this not affect/damage the measured wires current (we are measuring) as we are drawing/collapsing its magnetic field in order the induce a voltage in the coil?

Question 2: Why can the circuit diagram below not do the same job? The Rogowski coil only works when you form a loop around the conductor. Why does the Rogowski coil only work when its a closed loop? Why can a coil no just be in parallel with a wire and measure current?

simulate this circuit – Schematic created using CircuitLab

The right hand rules says that in the coils are wound in the correct direction, in the circuit diagram would couple the magnetic field the current is inducing.

Image source: http://www.electrotechnik.net/2009/09/what-is-rogowskis-coil.html


texts:
I'm build a synthesizer (up to 2GHz) and got a questions regarding the gound planes (analog vs. digital).

According to the datasheet (p. 7) some pins must be connected to analog GND, ex. pin 10 must be connected to the analog GND plane.

http://www.analog.com/static/imported-files/data_sheets/ADF4351.pdf

I read somewhere that it is best to have separate ground planes, connected at a single point. But somewhere else I read that it is best to have one gnd plane, and just be carefully with the the placement of analog and digital blocks.

But what is the best pcb layout design?


texts: How can I measure battery voltage with my MCU?

texts:
I am currently using the PIC24FJ128GA010 and I am planning to use Input/Output port to connect my 4.2 V LiPo battery and to check if the voltage value doesn't go below 3.7 V.

I am thinking to connect it to any of my input/output pin but I am wondering two questions:

Is it the correct pin?
Should I do a specific montage with resistor?


texts: Is it true that the power line frequency is kept accurate by atomic clocks?

texts: I've heard rumors that the power line frequency is kept stable and accurate by syncing it with atomic clocks.  Is this true?  What kind of accuracy does it have?  Is this true everywhere?


texts:
I want to know for a constant led driver having voltage ranges of min-max, like 21-42VDC,150mA minimum and maximum how many LEDs can be connected in series.
Please help me regarding above matters.


texts:
I need to sniff some legacy SPI hardware and at hand have a Pickit3 and lots of PIC18F2550/4550.

While there is no project out there that builds a logic analyzer out of a PIC18F2550/4550 (I will be glad if you suggested one), I can see that using the PICkit3 scripting tool (PICkit3_GUI_scripting_v03.00beta) it could be possible to run the PK2 logic analyzer feature on the PK3.

Unfortunately, Microchip does not seem to have taken that software forward, nor do I see anyone writing about it.

My questions:

has anyone actually used the PICkit3 scripting tool (and specifically the logic analyzer feature)?
are there any "good" DIY logic analyzer projects out there that use the PIC18F2455/2550/4455/4550 family?


texts: Use a dropping resistor or a zener diode?

texts:
I have a situation where I need to power an Arduino Uno R3 from a ~16V power supply.

The problem is I have no idea of the implications of voltage dropping. I think I just need a 100 Ohm resistor.

So, in case I am right, my actual question turns into: When is it better to complicate a circuit with a Zener diode?

I will also attach a photo since I understand it is easier to read from it.

Edit 1: A neighbor suggested a 4V LED that would also indicate it's working.


texts: Ceramic resonator instead of LC tank in a quadrature demodulator

texts:
I'm new to analog circuits. I have a simple question.
Can I use a 455khz ceramic/crystal resonator instead of LC tank on a quadrature demodulator input of MC3357?
Thanks.


texts: Why do micro controllers run @ 100's MHz whilst CPUs run @ GHz?

texts:
Whoopie - I've got a Raspberry Pi. When doing stuff it runs @ 1.2GHz and there are Uber overclockers out there who have boosted them to 1.5GHz (with phase change coolers).  Today, the cheapest CPU on Amazon (Intel E7300 Core 2 Duo - £8.99) runs @ 2.66 GHz.

An Arduino Uno runs @ 16MHz and the top of the line Microchip micro controller (SAM 7) only goes to 300MHz.

It seems a micro processor runs ten times faster than a micro controller whilst being hugely more complex.  Why?  Is it that AMD and Intel are cleverer than everyone else, or is it something more fundamental?  What's the difference between a microcontroller and a microprocessor? doesn't cover this particular aspect.


texts: I am reading about creepage distance and clearance and came across a T0-247-3 SiC diode (IDW20G120C5B). This diode is rated for 1.2kV which would mean that it won't break down at let's say 800V, which is fine. But I checked the physical distance between the anode and cathode pin and it is 2.5 mm, which as per Pollution degree2 material group 4 (I chose this category as found most of sensors following this), can sustain only 250V. Isn't this contradictory? Or what am I missing


texts: Wireless sensor network in practical for beginner

texts:
I am a master student, and I used to implement my protocol or scheme of WSN in the simulator(e.g., N3S or MATLAB). I am currently want to know how to touch the WSN with the real device. Can anyone share some suggestions:

Which type of sensor can achieve the capabilities: organizing network topology, implementing router protocol, etc.
How to code these sensors to obey my scheme? Should I have a Raspberry Pi?
I am skilled in C/C++, Python. It's enough to build my WSN from scratch?

Industry WSN is too complex for me now. I just want to have my own simple&small WSN in this stage.
Thanks in advance.


texts:
I'm designing a circuit using an LDO voltage regulator; specifically the LD39130SPUR from ST. This variant of the part allows for an adjustable output voltage via a potential divider as seen on page 8 of the datasheet. Usually, when using adjustable LDOs and other similar parts, a formula is provided to calculate the output voltage.

My issue is that I can't seem to find any such formula or other information that will allow me to calculate the output voltage. Am I missing something? Or, is there a 'standard' formula used to calculate this sort of thing given specific input parameters?

I'm looking to achieve a voltage of ~3.5V.

Thanks.


texts: Current across a wire with zero potential difference

texts:
If there was a circuit connected with a \$50 \,\Omega\$ resistor and a \$5 \, \rm V\$ battery and we measured the voltage across two points of the wire that have no resistor or battery, does it mean the voltage is zero? Then, according to \$V = I R\$, is the current also zero?

Assume that the wire has negligible resistance.


texts: Input impedance of low pass filter on LTspice must be constant in it's pass band?

texts:
I have single supplied sallen-key filter more that have nice 3MHz flat LPF response.
I tried to compute the resistance directly by dividing the input voltage by input current which is the voltage and current of source but it seems not ok:

I know this "transient analysis" must give me impedance of this frequency. but this blue trace is weird trace!

AC. Analysis:

I think I have low pass filter then resistance must be constant in pass band, isn't that? why if not?

Filter response:

What should I do?
In transient analysis: There is current lag, use shifted current? or what?

I've also seen somewhere replaced voltage source by current source and simply plot input voltage bode diagram!!! but it's single supplied and we have constraint?!

Buffered RLC filter input impedance in transient analysis (According to "Andy aka"s nice answer):
I think AC analysis show input analysis is ultralow, then we need buffer in input and output, isn't it?

Frequency response that is very good for me:

I think this arrangement is correct:

Why this have high resistance change in pass band(0-3MHz)? then we can't model it as a constant load in our simulation?


texts: Double polarity pulse with one single power source and virtual spdt switch

texts:
I have a problem in the design or my circuit. I need send data at a maxixum bitrate of 12000 bits /second. The high value should be +12v and the low value should be -12v providing at least 35mA of current. I initialy thought that I could easily get thoses values with the max232 chip. But when I did some tests, I could only get -7.25v, far from the -12v I need. The rest of the time, no data should be sent through the wire, so the current should be stopped logically. I made a diagram of the concept of my circuit so it's easier to understand :

I will use a 12v battery if need be, but I'd rather find a way to use a 9v battery. I would use a 5v regulator to get the 5v required for my microcontroller and then with my microcontroller I would send data. That data would then be converted to (+12/-12v high/low).
The S6 Switch is used to stop the current when I do not wish to transmit data.

I've thought of a way of accomplishing all of that, but I have technical difficulties to achieve a logical spdt switch and on the whole I wonder wether it would work and if there wouldn't be a better design that mine.
Here's a diagram of my first draft :

So I use an inverter schema with the IC MC34063 that will provide me with a -12v with 100mA. Then for the +12v I directly use the power source. I'm sure it's a good idea.
Then I would use an electronic equivalent of a spdt switch (S1) connected to both the +12v and -12v driven by one or two pins of the microcontroller (preferably one). That should give me nice squared -12/-12v signals (not sure about that too) and then I would have electronic switch (S2) to open or stop the signal whenever needed.

So to sum up, my questions are :

1) Will my design work, what would be problematic ?

2) Is there a better design, maybe more efficient and with less components that mine.

3) How do I achieve the electronic equivalent of the spdt switch (S1) ? I've already opened a thread for S2 that was solved (see Electronic switch with negative and positive voltage)

4) With my design, will I get a nice squared -12v/+12v usable signal that will supply me with the 35mA I need ?

5) Can I work with a 9v battery instead of 12v battery ?

6) Can I use less microcontroller pins ? Ideally 1, but 2 would be okay as well.

Thank you for your help and inputs.


texts: Cheapest way to wirelessly synchronize two MCUs

texts:
I have two battery powered MCUs about 30cm apart, one will be the master, and one the slave. Each MCU has several LEDs connected which flash in a sequence.

All I want to do is synchronize the two MCUs so that the sequences don't drift out of phase.

Is there some super easy way to send a simple RF pulse from one MCU to the other?

Added:

The sequence lasts for approx 1 second, and repeats forever.
If the slave misses some sync pulses, it's not the end of the world, because it would take many cycles to drift noticeably out of phase.
For personal / religious / aesthetic reasons which I am not allowed to discuss, I do not wish to use IR, capacitive, acoustic means to transmit this pulse.
The range is very short, less than 30cm.
The signal will need to travel through open air. No concrete or metal in the way.
RF-like inductive coupling would be OK too.
Since the signal consists of only a single pulse, I imagine there must be a smaller, cheaper solution than those involving packet transmission (Xbee, etc.)
Ideally the solution would consist of some kind of PCB trace antenna, and a simple oscillator for the transmitter, and simple circuit (demodulator?) to detect the pulse at the receiver.


texts: MCP23017 connection to CD74HC4067 through Diode

texts:
I am connecting a digital output pin from an MCP23017 through a diode (1N4001, forward biased) to a CD74HC4067 input channel. VDD is 5V to all devices.

I am seeing 1.45V on the anode side of the zener and 0.7V on the cathode side. Since the CD74HC4067 is hooked up to the cathode side of the diode, I'm also seeing 0.7V there. If I hook up the CD74HC4067 to the anode side, I see 1.45V there.

I was expecting to see 5.0V-0.7V=4.3V at the anode side of the diode, why am I not seeing that?

If I just connect the diode from 5V to ground, I see 4.3V when it's forward biased.

Any help would be appreciated.

Thanks!

Edit: rectifier diode, not Zener.

Fix found! I had to disconnect GPA1 (accidentally still had it connected).


texts: Where exactly in the environment does the 60Hz power line noise be picked up from?

texts:
I am measuring EMG signals using ADS1299, and I have problems removing/eliminating the 60Hz noise in my measurements. I measured the EMG signal in differential mode, and I also incorporated a driven right-leg circuit to eliminate the 60Hz noise, but there are still some (a lot of) 60Hz noise in the received EMG signal.

I know that the 60Hz noise is mainly picked up from the power line, and I wrapped the wires and the power cables with aluminum foil sheets, but it didn't help much. I've also learned that human body acts like antenna and will receive/be coupled with that 60Hz power line noise, but I thought that because I am measuring the EMG signal in differential mode (use two electrodes, a "+" and a "-" to get signals), the 60Hz noise from human body should have been eliminated already. I also checked the contact between the electrodes and the skin, and I am pretty sure there wasn't any loose contact. I tried both dry electrodes and wet electrodes, but I have the 60Hz noise in both cases.

I don't understand why I still have the 60Hz noise in my EMG signal. I cannot simply apply a notch filter to filter out the 60Hz thing, since 60Hz is within the EMG signal frequency range, and I don't want to lose any original EMG signal.

I was wondering where exactly has the 60Hz power line noise been picked up? Does the 60Hz noise mainly come from the electrodes, human body, ADS1299 itself, wires, or nearby devices?

Thanks!


texts: Current Monitoring - CT vs Hall Effect vs Rogowski Coil?

texts:
I am trying to determine the best option for monitoring the current in a specific application but am having difficulties deciding between a current transformer, Rogowski coil or Hall effect sensor.

The main purpose of the sensor is to determine whether there is any fault or unbalanced loads in the circuit. Under normal operating conditions the current flow will be fairly low in the 0-20 A range. For unbalanced loads the current can go up to 60-70 A. The main concern are jacket faults which can lead to currents up to 400 A for an extended period of time.

The aim of the current sensor is to detect when these currents rise so that action can be taken before any significant damage is done to the cable.

The main concern is accuracy, however there is some leeway there as an issue with the cable will usually cause a fairly significant increase in current.

Another major concern is price.

The current transformer seems like a viable choice since it has a large current range and is fairly accurate. However, while the Rogowski coil is typically used as a method for temporary current measurements, I have also seen that it can be used as a low cost alternative to a CT. From my understanding, many of the issues with accuracy for a Rogowski coil are due to positioning, but this would be installed in a solid box so the coil would always be in the same predetermined position. I do not know if this is enough to achieve a higher accuracy though.

The Hall-effect sensor I do not think makes much sense since we do not need to know DC currents and they are more difficult than CT's to engineer for high accuracy. Also, from what I have seen they tend to be higher cost but they do seem to come in a fairly wide range of prices. I did not want to rule them out altogether at this point.

Thank you for any help or guidance you can offer.


texts: Modify RAMPS 1.4 adding external MOSFET for heat bed: can I remove original mosfet?

texts:
I have a GT2560 board for my 3D printer. It is a custom board based on RAMPS 1.4 + Arduino mixed togheter in only one board.
(here you can find RAMPS 1.4 schematic)

I have some issues with the heat bed connector caused due to the high current, I bought an external MOSFET board like these one:
https://3dprint.wiki/reprap/electronics/heatbed_mosfet

This module has a rectifier just after the 2 pin signal connector, an optocoupler, and a mosftet and connectors for high current. The rectifier has been inserted to avoid polarity issue on the signal connector.

I read the instructions and how to connect it, but I cannot understand why they suggest to connect it to the heatbed 2 pin connector instead of directly on the old mosfet gate signal.

My plan was to desolder the original MOSFET (the STP55N06 in the 'Heaters & Fans' schematic section) solder a cable to the gate pin hole and connect it to the 2pin connector on the external mosfet board.

It is valid alternative?
If it is a bad idea, can you tell me the reason to use the original mosfet out?


texts:
UPDATE
I found out the issue. Specifically, the PNP transistor I got. I used a BC557 - for some reason its collector-emitter current is very very low. It does open when the base-emitter junction goes right. But there's practically no current going through it. I tested it for all 20 of them, even unused ones. Same issue. Is this a problem with my transistor choice or a bad batch?

simulate this circuit – Schematic created using CircuitLab

This is a circuit i'm using to make a controllable H-Bridge.

Since the diagram's a little messy, I'll explain a bit. SW1 (which is actually a bunch of transistors, but it's on a separate circuit so I've simplified it to a switch) should change which direction the motor goes in.

If we consider the "up" position only, Q1 and Q2 should switch on due to the higher potential - Q2 should connect Q3's base to the positive rail, and Q1 should connect Q4's base to ground. This will allow current to flow from the positive rail through the PNP Q4 into the motor's "OUT" terminal, run the motor, then flow out into Q3 and towards ground. Mirror process for the opposite side.

The problem is that this doesn't work. There's a minute voltage across the motor (~0.02V). The batteries are definitely running since voltage across them drops to about 2.6V. The only other evidence of it running is that Q3 heats up a lot after a while. I think other transistors might be, but I'm afraid I only noticed Q3 doing so.

Personally I think it's something to do with some transistors not switching on, or some transistors switching on when they shouldn't. Any ideas?


texts: How to drive a speaker with amplifier using 3.5 mm jack

texts:
I have two bare loudspeakers salvaged from old speakers and I would like to control them from computer using 3.5 mm jack. The speakers had a control board, but that is broken. I would like to drive 5 W 4 Ω loudspeakers. When posting schematic please add legend to describe what each symbol does. For amplifier circuit would be controlled by potentiometer. And preferably mono for two speakers.

I found TDA1905 IC to connect the speaker to which works perfectly since it outputs 5 W 4 Ω which is perfect, but my question about application circuit in the manual is what are VI, VT, C5, VS and these symbols that I highlighted in red in picture below.

Another question is: Can I put speakers in parallel as shown in schematic above, i.e. two identical speakers?

Edit 2: VT seems to be threshold, but what kind of voltages are accepted?


texts:
I am using a CC1352P1 launchpad from TI and trying to connect it to ENC28J60 for ethernet. I am able to transmit messages to my computer such as an ARP request, and the computer recognizes it and sends back its MAC address. However, I seem to be unable to read packets on the ENC28J60. I have written my own driver to interface with the ENC28J60 and can successfully set and read back values to and from registers on the ENC28J60.

My question is about when to actually call the packet receive function. I modeled my packetReceive function after the packetReceive function in the EtherCard project. I am unsure of where to actually call this function. So far, I have it in a while loop like so:

I've read in the datasheet that when the buffer is fully written to, and packet is available to read, the EIR.PKTIF bit is set and EPKCNT is incremented. Thus, it seemed to me that this would be the place to call my packetReceive function. However, this is not working, as the function either never gets called or never receives valid data. The data that I read from the receive buffer is always all zeros or no data.

while(1){

    ethernet_receiveEnable();

    if(spi_read(EIR) & 0x40){

        uint8_t len = ethernet_packetReceive(receive_Buffer);

    }

    ethernet_receiveDisable();

    sleep(1);

}

Here's my read function

uint8_t ethernet_packetReceive(uint8_t* receiveBuffer){

uint8_t len = 0;

uint8_t status = 0;

uint8_t* header = (uint8_t*) malloc(sizeof(uint8_t)*6);

if (spi_read(EPKTCNT)>0){

    spi_write(ERDPTL, gnextPacketPtr & 0x00ff);

    spi_write(ERDPTH, (gnextPacketPtr & 0xff00)>>8);

    readBufferMemory(header, gnextPacketPtr, 6);

    gnextPacketPtr = header[0] << 8 | header[1];

    status = (header[2]<<8 | header[3]);

    len = (header[4]<<8 | header[5]) - 4;

    if (len > 8092-1)

        len = 8092-1;

    if ((status & 0x80) ==0)

        len = 0;

    else{

        readBufferMemory(receiveBuffer, gnextPacketPtr, len);

        receiveBuffer[len] = 0;

    }

    if(gnextPacketPtr-1 > RXSTOP_INIT){

        spi_write(ERXRDPTL,RXSTOP_INIT & 0x00ff);

        spi_write(ERXRDPTH,(RXSTOP_INIT & 0xff00 )>>8);

    }

    else{

        spi_write(ERXRDPTL,(gnextPacketPtr -1 ) & 0x00ff);

        spi_write(ERXRDPTH,((gnextPacketPtr -1 ) & 0xff00) >> 8 );

    }

    /* set ECON2.PKTDEC */

    selectMemBank(0);

    bitFieldSet(0x1e, 0x40);

}

return len;

}

I am using the lwIP net stack and intend to call the other wrapper functions if EIE.PKTIF is set, but that's not been working so far.


texts: Why in op-amp inverting circuits one of the op-amp inputs is grounded?

texts: Why the input have to be grounded in Op-amps? What does it do? How does op-amp sense the input voltage difference?


texts: Synopsys Design Compiler: Setting a maximum critical path delay on sequential circuits

texts:
I have a couple of designs written in Verilog that I'm trying to synthesize with Synopsys DC Compiler. Specifically, I would like to maintain a 1ns upper bound on my critical path delay (CPD) on my designs — I have been able to successfully synthesize these designs with yosys (open source RTL synthesis tool) and meet this constraint.
I've tried setting a variety of parameters in a tcl script that I am using for synthesis of my Verilog modules, but none seem to be enforcing this upper bound on my CPD. Just to name a few things I have attempted: I've used the compile_ultra command, with and without the -retime flag (and the set_optimize_registers flag preceding this). I've tried using the set_max_delay command on all clocked paths, and any path from all inputs to all outputs. I've tried various settings of the clock period, to see whether increasing/decreasing the clock period from 1ns could help things.
Unfortunately, none of these has worked. Consistently, the DC compiler indicates that the timing slack has been violated and returns a CPD of nearly 4ns. I've been stuck on this issue for some time, and I'm not sure where else to turn to for help. I'm new to this tool, but I've tried reading through large portions of the DC Compiler manual in search of more parameters/commands that may help.
I would really appreciate it if someone had any advice on things that would enforce this 1ns constraint, or some intuition about the tool that could help. Thanks in advance.


texts: Connecting sensor microphone CM-01B to Raspberry Pi

texts:
I have a plan to build a phonocardiogram (PCG) with CM-01B piezoelectric sensors.
I found similar research that used the same sensor, but it seems that there is no need to build any additional circuit to send a proper signal from the sensors to the computer unit.
I intend to acquire data using a Raspberry Pi 4B
I am not quite sure about this.
Is it enough to directly connect the sensors by the modified cable  (i.e. that can be connected to USB or SDA pin) to Raspberry Pi for getting a good heart sound signal?


texts: Why do these equations prove that power factor is constant for all circuits in case of sine wave?

texts:
I know that I'm missing something but I don't know what I'm missing.

Power factor is the ratio between real power and apparent power. So, I will get the equations of real power and apparent power then, I will divide them.

I'm going to start with real power which is the average power. The average of a sine wave is always zero so, I will rectify it then calculate the average.

Second, I will calculate the apparent power. We can get it by multiplying the root mean square values of voltage and current.

After calculating the real power and apparent power, I'm going to get the power factor and the result is surprising!! Would you tell me where the mistake is, Please?

Thank you very much,


texts: SimpleDHT: what does error code 4112 mean? (not in source code on GitHub)

texts:
I am using the SimpleDHT library, running on a ESP8266.

Occasionally I get error code 4112 on serial output. The variable that holds this error code is declared as an int.

However, the source code has them in hexadecimal, and none of them appear to be 4112 (0x1010).

Also, the error codes used to be in decimal format in the source code, but the authors have changed it with reason "Combine error and t into error code". Not sure if that is a clue, no idea what 't' refers to.


texts: how to identify the male-female and female-male jumper wires?

texts: I know it is a basic question but still I am confused , I wanted to use the female-male jumper wires on my basic electronic project ,So my question is how Can I identify which is female-male or male-female jumper wires?


texts: If I had an infinitely large paper, how could I draw an n-element karnaugh map for (n>6)?

texts: I understand that k-maps become impractical after around 5 variables, and my textbook only describes them up to 6. However, out of curiosity, is there a general rule, method, or algorithm that I could use to draw a k-map for any given variable amount (20 for example), even if it would not be completable in a year. If it is impossible on two dimensional paper, is it maybe possible if I could theoretically draw in more in than two dimensions?


texts: Noise Coupling methods to communication cables

texts:
I want to know how can I couple noise(practically) into a communication cable in order to analyze the data error rate of the communication.
I hope by using transformer I can couple it, but I don't know the rating of transformer used. I am using coaxial(shielded) cable of 1000ft, RS485 standard and modbus protocol.


texts: Determining which capacitor for a latching pushbutton circuit with NANDs

texts:
I am working on a latching push-on/hold-off circuit for a momentary button and I am stuck with determine which type of capacitors to use. The circuit is detailed below (originally from Mosaic Industries):

simulate this circuit – Schematic created using CircuitLab

I am unsure whether or not this will work with electrolytic capacitors, and if it will which polarity should they be? I have considered ceramic capacitors, but I am unable to easily source 1uF ceramic capacitors. As the schematic does not indicate that they are polarised capacitors I suspect that ceramics are the only option, but if this is the case what value would be ideal given I can only find values less than 1uF.

For this circuit I am using a CD4011 NAND IC.

Any advice is greatly appreciated.


texts: buck-boost, SEPIC IC out 3.3V and min 500mA 0.1" packaging

texts:
I am building some sort of navigation device for a logisitics project in my company.
The whole thing is going to be battery (6V) powered, so I'm looking for every possible way to avoid losses to heat etc by turning off ports I don't need, stripping peripherals etc..
My lineup so far is a Rapsberry Pi A (40% less consumption than ver. B), a 128 x 64 px touch display that comes with some nice power-down features and an XBee-Pro module, that also has sleep and hibernate modes.

All these devices run on 3.3V. The 5V on the Pi are only used to power the attachable USB devices, so the input to the Pi is regulated to 5V if it is above, then fed to the USBs and again regulated to 3.3V. Both regulations happening with linear regulators afaik, which are not very efficient, aka they just "burn" the undesired amount of V.

Now if I disable the integrated regulators of the Pi and attach my own buck-boost/SEPIC ICs regulator that goes straight and efficient from Vin to my desired 3.3V I can again save a lot of energy.

My problem: I cannot seem to find a suitable chip. The main difficulty is that those I was able to find ususally come in a packaging type that is impossible for human hands to solder.
I am looking for:

Vin up to 7V
Iout at least 500mA
Vout 3.3V
buck-boost mode
0.1" pin-out

Any help apprechiated!

simulate this circuit – Schematic created using CircuitLab


texts: LiIon Cell protection/charging circuit wtih AP9211, (Or other IC)

texts:
I'm trying to design a simple protection/charging circuit for a single LiIon 18650 Cell and think I made a mess with the Diodes Incorporated AP9211 IC [1]. It's my own fault as I skimmed through that data sheet but keyed off the typical application circuit and bread boarded that circuit. So the Over discharge circuit, which is the 'typical application circuit' given in the datasheet [1] worked.
My problem came when I decided I'd try to charge the 18650 again. I connected my charging voltage 5V to the P+ and P- connections of the 'typical circuit'. That resulted in no charging happening, so I went back to the datasheet and reading that discovered that the negative charging voltage should be connected to the VM Pin, Oops.
So I corrected my mistake, but again no charging happening, which is likely down to me having applied 5V across P+/P- so I might have blown the IC.
I only ordered up one to try this out but given I have to re-order to try again I have a few questions which someone probably has a much better idea of.
I'd like to have some indication that the cell is charged, either an LED turning on or off, and not sure how to add that to the AP9211 IC.
Secondly that IC is a bit fiddly to solder in that package and wonder has anybody got any advice/experience with a simple solution to over charge/over discharge protect a single 18650. I thought that IC looked the part but not sure now.
Thanks for any advice.
[1] https://www.diodes.com/assets/Datasheets/AP9211.pdf


texts:
i was using this NAND gate, and with inputs as 1 & 0, output is 112mv and 4.1 V,
what is the reason for the rise or drop in the voltage at the output?


texts: Common Emitter, can't understand how collector current is found

texts:
So there is this common emitter transistor and it says Ic = (Vcc-Vce)/ RL, what I'm not understanding is why Ve is totally ignored, I thought Ic = (Vcc-Vc)/RL. How come the Emitter resistor is totally left out of the calculation when it does affect the value of Ic.

The link to the whole page: http://www.electronics-tutorials.ws/transistor/tran_2.html


texts:
I'm looking for a very big connector plug, similar to the old SCART connectors, except I need it to be at the following specs:

No Of Pins: At least 35, preferably 50
Gauge size: At least 12 pins with min 12AWG, at least another 10 with min 18 or 20AWG, and the rest whatever theyy come in. (If they only come in one size, then an entire thing of 12 AWG is fine
Amp Rating: The higher the better!

Does anyone have any idea as to a store or catalogue where I could find one? Or, if you know a specific one, that would also be great!

Also, Can anyone give me it's proper name? (Connector Plug? Multi-Pin Plug)

Thanks,

Sasha


texts:
I am currently working on a digital input card which will feature quadrature encoder inputs. To my (basic) knowledge, quad encoders use two pulse trains that are 90 degrees out of phase with each other and sometimes an index output for reference position. This gives 3 output signals (possibly six if they are differential outputs)

Now, this is the schematic for the quadrature inputs on our card. We are supporting both single ended and differential outputs. My question is the following:

Has anyone ever used quad encoders with 4 output pulse trains? What are these I and S differential signals shown on the schematics? I cannot find any quad encoder that outputs these signals...

Thank you very much for any info.


texts: how electron flow in circuite, when wavelenght is very long such as 5 kilometer?

texts:
1-My first question is: when signal with low frequency such as 100khz the wavelength of that is 5 kikometer that means between high and low voltage must be 5 kilometer .so when signal propagate by electron in short circuite (size of circuit is very small than wavelenght)how does electron flow in circuit and 5 kilometer space between the hight and low voltage produce in short circuit???is it true the wavelength of the signal that means:distance of electron travel to reach the first point? If it is true so the signal with 5 kilometer wave lenght produce complete when electron travel 5 kilometer and thus structure repeat.

2-when the size of circuit very small than if wavelength ghen for analysis the circuit we use Kirchhoff's circuit laws Whay the voltage and current in this circuit not change?but in high frequency change I guess in low frequency that wavelength very big than size of circuit the electron have Enough time to reach end of wire and Enough to produce a cycle of signal Because the electron move is very fast and wavelength is very long that the cgarge of electron Enough time to travel on circuit and produce a cycle of wave before next cycle produced. I guess this 2 reason for not change current in length of wire and voltage in first and end of wire is same.is it true?

I know transmission line theory how work. but I dont undrstand whay voltage and current is same in all of the wire lenght,when frequency low and wavelength is very long of size of circuite? in transmission line and maxwell theory happen stand wave because the wave length in antenna and transmission line is proportional lenght of conductor and electron charge not enough time to reach end of conductor befor a cycle if sine wave ended so the electron charge reflected back and stand wave happen this reason of whay antenna work like resonator and radiate with high amplitude. In transmission line and antenna the voltage and charges electron in 1cm and 3cm of wire length is difference because the frequency is very high and wavelength proportional to size of length wire and when electron charge flow in wire because of wavelength the cgarge if electron difrrent in length of wire and no time to reach end of wire and this reason the voltage in length of wire is difference unlike lumbd circuit that voltage same in all length of wire. I dont undrestand this phenomenon how to happen in low frequency and very long wavelength which makes voltage not changed in lenght of wire? is it true the sentence Thanks bro.


texts:
Is it possible to produce over 1000 lb of magnetic force over a distance of 4 inches(0.101 meters), using an electromagnet?

How difficult would it be? Explaining the general spec's of such an electromagnet?
Most importantly,the power input... how much power would this electromagnet need? A few kWatts?


texts: Load-line of MOSFET when analyzing triode mode

texts:
When we are analyzing MOSFET within a circuit (e.g. as an amplifier) with drain or source resistor we must consider the load line of transistor, like so:

When used in triode mode a.k.a. ohmic mode there is said that drain current increases linearly with drain-source voltage and when used in active region there is often said that drain current changes almost nothing with drain-source voltage.

How is this possible if increasing drain current decreases drain-source voltage and vice versa when considering load line?


texts: Trying to get v(t) for discharging RLC battery

texts:
I'm having trouble with the following problem. I want to find \$V(t)\$ (part (d)) and have been working for quite a long time on it.

My first question is, if I do the following, are all the voltages in my differential equations the same voltage? It seems like they aren't, therefore this method wouldn't work.

What I tried doing was using Kirchoff's current rule so I had $$i_C + i_R + i_L = 0$$ $$\frac{d^2V}{dt^2} + \frac{1}{RC} \frac{dV}{dt} + \frac{1}{LC}V = 0$$

Second off, if this does all solve for the same voltage, then it is problematic because I'm getting a complex value for $$\omega_1 = \sqrt{\frac{1}{LC} - \left(\frac{1}{2RC}\right)^2}$$ in the following equation of voltage that we Ansatz $$v(t) = Ae^{-\gamma t} \cos (\omega_1 t - \phi)$$

So I feel like something is going wrong with what I'm doing. Please help me out in setting this equation up, thanks!


texts:
I'm trying to create a battery model using an equivalent circuit with a voltage source a resistor and 2 RC elements. To make it easier in this question I just used 1RC element.

simulate this circuit – Schematic created using CircuitLab

I know the parameters of the elements and the voltage of the source. (Not the same as in the schematic above)
Also the current that discharges the battery is given. (e.g. first 10 seconds 10A next 3 seconds 5A)
Now i want to calculate the output voltage. And actually it should be:

V_out= V1+R0*I+R1(I+C_1*dU_RC/dt)

Due I dont know dU_RC/dt I found this formula and think it's correct for the current step from 0A to 10A but not for the next step from 10A to 5A:

V_out= V1+R1*I+ R1*I(1-e^{-t/R1*C1})

Does anybody can help me with the derivation of the second formula based on the first one and to edit this second formula to be able to use it for more than one current step?


texts: BLE113 Bluetooth 4.0 module with CR2025 3v battery power supply

texts:
A question regarding the power supply of a BLE113 Bluetooth 4.0 module: I am attempting to order several bluetooth modules, but the main concern is the power supply. Since I am new in the field of all sorts of modules and electronics, what is the best way in which can I connect a bluetooth module to a power supply such as CR2025 3V?

The main idea is to connect the mentioned bluetooth 4.0 module to an Apple iOS application.


texts: How important is the shield on an RJ45 connector?

texts:
If I am going to use a PCB mount RJ45 connector for 100mbps Ethernet, does it need to be a shielded connector, or can I get away with using an unshielded one?

Is there some standard which deals with this, or is it just my responsibility to get the thing EMC tested.


texts: Regulating Volatge Output of Synchronous Motor

texts:
I'm attempting to regulate the output voltage of a synchronous motor being  used as a generator.

I've hooked up a LM317 along with a high voltage capacitor and some diodes.
I decided to attach the diodes to try and isolate the interaction with the LM317.  When leaving the load and capacitor unattached I am able to reach 150-200V easily with this motor.

However, as depicted in the diagram, when I attach the load: the voltage of the system drops drastically.  Between .3-1.5 Volts.

The LM317 seems to not be doing it's job, as I move the pot's value, change the resistor value, and the overall system voltage is the same.  However removing the LM317 does cause the voltage to drop a bit as well.

The two dots on the rectifier bridge are where I am measuring voltage, as well as where the two circuits are connected up to.

I have tested the circuit with the LM317 with both diodes, one or the other diode, and with no diodes.  While also swapping out two resistors of 462Ω and 8.17KΩ.  The swapping had no affect on voltage.

The removal of one diode (either side) drops the voltage from 1.5V to .95V.

The removal of both diodes gives a voltage of .3V.

Having the load attached to the rectifier be only 2 diodes gives a voltage of 1.25V.

I don't know if this has to do with impediance and current or what.  Also am not too sure how to begin testing for those factors.


texts:
Recently I've got my hands on several 20x2 character displays which don't seem to work. This is what they look like:

Apparently, they are HD44780-compatible. The three 16-pin connectors (single-row and double-row) are just parallel to one another. Pins 15 and 16 (typically used for backlight in LCDs) are not connected to anything.

I am able to push the data in using a microcontroller using both 4-bit and 8-bit HD44780 protocol, then read the data back, so the logic seems to be working. The logic is working at both 3.3V and 5V supply voltage. The display, however does not light up. I've tried voltages from 0 to 5V on the contrast input (pin 3) to no avail.

I've taken one of the displays apart, and this is what the matrix looks like:

This is what the board looks like with the matrix removed:

I'm pretty sure the driver for the matrix is not dead. In the disassembled screen I've measured the waveforms at rows and columns. There is a DC voltage at about 7.5V across all the rows, and different waveforms with about 1.5V amplitude and period of about 7ms at different columns. The waveforms look like they correspond to some pixels being on and off.

UPDATE: Amplitude of these waveforms is dependent on the brightness input (pin 3), going from 0V to 7.5V.

https://imgur.com/a/TNg1l

The devices were new in factory packaging, so my guess is either they are all defective (even though there is a QC stamp), or they have some design flaw.

I've tried applying different DC voltages across rows and columns of the matrix, but nothing happens.

What kind of matrix is this anyway? Doesn't look like an LCD, so can it be some kind of LED (PLED, OLED)? Is there a way to test this matrix separately (because the logic board seems to be fine)?


texts: Can you guys please help me find the symbolic transfer function Vout/Vin in this colpitt oscillator ?


texts:
I have some questions about holes in a semiconductor. When I checked the net I found holes are said to be equivalent positive charge and they say because the hole moves from one place to another when it is occupied by an electron, and electrons leave holes behind, etc...

But I couldn't find a clear answer for P-type semiconductor. It is written the holes in the valence band increase, but my problem is I see that lags and reduce the current not increase it because the holes somehow will attract electrons and get them from conduction band to valence band, and since the conduction band is the band that allows current to flow, won't that reduce the current instead of increasing it?


texts:
What's the easiest way to mount a bunch of surface mount LEDs into an array or spotlight?

There are a bunch of very interesting new papers on red light therapy for a variety of conditions. I want to experiment with it. The most beneficial spectrum is around 650nm. I can't seem to find any bulbs that come ready made with the ~650nm LEDs in them. If you know otherwise, please speak up.

So I figure I can get thirty or so of these Phillips "deep red" LEDs, mount them parallel, and connect to a suitable power supply:

Philips Lumileds LXM3-PD01

I'd like to avoid having to solder them on to stripboard or something like that. Partly because I've never worked with SMD and haven't soldered in many years. Can anyone think of an easy way to mount them?

There are a bunch of LED spotlights that come with white LEDs already installed:

LED Spot Lights

Is there a way to get the fixtures without the LEDs? Should it be easy to remove the white LEDs and refit the Phillips red LEDs? I don't have any experience with such things.


texts: Control differences between ac induction motor and brushless dc motor?

texts:
I have a fairly solid background in industrial AC motor control (soft starters, VFDs, etc.) but something that I'm certainly NOT well versed in is brushless DC motors... the type found in every hard drive on the planet.

As far as I can tell, they look identical to your typical star-connected AC induction motor, and the motor controllers look to be very, very similar to the typical three-phase AC controllers I've spent most of my professional life designing.

I can't find much on the real differences between the two, neither from a mechanical construction point of view nor from a control point of view. The closest I seem to find is "they're similar."

Does anyone have any resources or can offer a fairly technical explanation of what the major differences between these types of motors is and their control methods?


texts: ST1S10 step-down regulator - can I drive the EN pin from the voltage divider?

texts:
The ST1S10 step-down regulator (http://www.st.com/web/en/resource/technical/document/datasheet/CD00169322.pdf) has an INHibit (active low) / ENable (high) input terminal, like any other DC-DC regulator I guess.

I'd like to use it for an UVLO function. I initially thought of matching a voltage divider in a way that my battery cut-off voltage is at the high-low transition level of the EN pin of ST1S10. In the datasheet I can see though that the Vmax for OFF is 0.4V and Vmin for ON is 1.2.

What happens between 0.4V - 1.2V? Is that the hysteresis that I can rely on or is that an unknown state?


texts: Does armature flux move when the position of brushes in a loaded DC generator are adjusted? If so, what happens to the original resultant flux?

texts:
Based on my readings, a loaded DC generator creates both a main flux from the field poles and an armature flux that is perpendicular to the main flux. This causes a resultant flux at an angle. Because the magnetic neutral axis is perpendicular to the resultant flux, it will shift by an angle. This will cause sparking in the brushes.

To remedy this, the brushes are moved to the magnetic neutral axis. Going by the labels, a "armature flux" is present in the direction of the new magnetic neutral axis. It can be broken down into components. The x component is known as the demagnetizing flux and the y component is the cross magnetizing flux.

What I don't get is, is the armature flux from Picture 2 the new armature flux that is suppose to replace the first one? If so, won't the new armature flux and original main pole flux create a new resultant causing the magnetic neutral axis to change yet again?
Yes, I know that is a stupid idea and I am aware it is wrong. Because I am fully convinced of the concept that adjusting the position of brushes to the magnetic neutral axis does remedy a loaded DC generator. However, I really don't get how both pictures seem to use the armature flux and for me it implies that you shift the armature flux. It causes confusion for me because I think of the idea that the resultant flux is suppose to change.
It is possible that the armature flux that both pictures have the same notation for are suppose to mean different things. That might be the case. But I don't know exactly why and how. I decided to ask this question because almost all armature reaction discussions involve this concept and visualization and I can't seem to get an answer for my question. It might be best here since there is a little more analysis done by the people here rather than resorting to looking at the textbook.


texts:
I bought this dirt cheap Spectrum analyzer from a Chinese web site. It arrived and all it had was an antenna. I have very little experience with spectrum analyzers, how can I build a probe for this equipment. The equipment expects a 50 ohm probe and it has BNC connector.

So far, I took a BNC cable, ripped one side, soldered a 805 50 ohm resistor to the tip and left the ground alone to make measurements. Does this make sense?


texts: Transient analysis of square wave using PSPICE

texts:
I need to do a transient analysis of my BJT cascode amplifier. I was asked to use VPULSE as the source. I need to set VPULSE for +-10mV, 50% duty cycle square wave at 128 kHz with rise time and fall time of 10 ns.

In PSPICE, I had set the VPULSE's attribute as

  V1=-0.01
  V2 = 0.01
  TR = 10ns
  TF = 10ns
  PW = 3.90625u
  PER = 7.8125u

The transient analysis setting is

 Print Step = 10ns
 Final time = 9us
 No print delay = 100ns

I would like to know how can I set my 50% duty cycle and is my analysis setting correct?

My simulation result shown above.


texts: Voltage drop after writing to slave register with I2C protocol

texts:
I'm trying to control this bipolar stepper motor with an Adafruit Huzzah32 (ESP32) board and a stepper driver shield.

Power sources:

ESP32: 5V USB port
Shield: 4 AA-batteries in series

I programmed the board in micropython and it starts as intended. I'm using an older library from Adafruit to control the stepper and this code at launch:

import time
import machine
import stepper

i2c = machine.I2C(scl=machine.Pin(22), sda=machine.Pin(23))

steppers = stepper.Steppers(i2c)
s1 = steppers.get_stepper(1)

while True:
   for i in range(100):
       s1.onestep(stepper.FORWARD,stepper.DOUBLE)
       time.sleep(0.01)

But after a few seconds, the LED on the shield fades out and the stepper slows down until completely stopping.

When I do:

s1.cpa9685.i2c.writeto_mem(s1.pwma, 0x00, 0x00)
s1.cpa9685.i2c.writeto_mem(s1.pwmb, 0x00, 0x00)

The shield LED lights up again.

I thought the back EMF from the stepper was limiting the current on the shield, so I increased the power source up to 10V by adding more AA-batteries in series.
That didn't fix anything, the shield keeps shutting off after a few stepper steps.

Do you know what I'm doing wrong? I'm way out of my league here.
Thanks in advance!


texts:
Is it possible to make PTH  (Plated Thorugh Hole) at home?

Can somebody explain the procedure?


texts:
I would like to drive a MOSFET gate using 12V (in order to reduce the drain-source resistance). Using the answer from a few post i've read I have come up with the following circuit. Will this circuit work for an application where i will be switching the motor on and off one every 10 minutes?

Further more is this the best method of driving the FET? and is there any type of "MOSFET driver IC" i can use to reduce space on my PCB?


texts:
This may sound like a basic task, but I am new to Electrical engineering.

I want to combine an QI Charging matt into my SmartHome. When my phone is charged by the mat a Green LED lights up. This LED is feed with 5V. I am using a window sensor to integrate this into my SmartHome. The sensor has a little magnet switch that pulls 5V to GND.

I now need to somehow get GND when the 5V are supplied by the QI charger and I have no idea how.

Thanks!


texts:
I tried the test current source followed by nodal analysis  and it worked.

But when I proceed to find the Vth followed by shorting A & B and then finding short circuit  current I am unable to proceed as I am stuck at the Vth!

Can someone please  enlighten me?

I assume I m terribly wrong at some concept!

Please share all possible methods of solving this one.

Thank you.


texts: Solderless breadboards: standard size specifications?

texts:
Are there standard sizes for solderless breadboards?

For example, My teaching project is currently reaching the capacity limit of a 170 pin (17 x 10) breadboard.  Is there a standard "next size larger" I can specify?


texts: Guidance on use of vias on power pins of ICs

texts:
I have a relatively low power PCB and am wondering if there is ever a need for more than 1 via (0.35mm dia) on any power/ground pins.  For example:
USB socket for battery charging at max 260mA (5V).
SOC with max current consumption of 15mA (3.3V).


texts: Car Battery Charge Indicator Replaced with LED then Dimly Lit When Off

texts:
I think I should be able to grasp something from this question but I'm not sure if my case is the same or not. Would be great if I can get enlightment on this.

In my case I'm replacing incandescent bulb with a 12V (resistor-equipped) LED chip of the same socket. The lamp is for battery charge indicator (+ - battery icon that glows when ignition is ON but engine is not running then off when engine is running unless there's problem with battery charging)

I think there is some direct connection between the bulb and alternator; then this makes me think I should be more cautious when fixing this problem. I also guess every <=90s car has the same problem: we should not use LED bulbs to replace incandescent bulb just for battery charging indicator.

The LED is dimly lit when it is supposed to be off during engine running, but totally off when the engine is not running and ignition is not in ON position.

Should I use bleeder resistor? how to measure how much resistance I should use? or should I put inline resistor before the indicator LED?

If I should get answer from the aforementioned link, please kindly let me know. Thankyou for any inputs.


texts: Configuring Arduino to use external ADC reference for Analog inputs through MATLAB support package

texts:
I am using the MATLAB support package for Arduino.

However, I need to configure the ADC reference to external. MATLAB documentation doesn't really explain how to do this?

Is there any way I can use the MATLAB support package and configure the Analog pins to use external ADC reference?


texts: Dependent or independent sources of voltage and current

texts:
I am confused with this term of dependent and independent . What exactly this mean .does dependent sources mean that if we connect a dependent source of voltage and current in same circuit ,they will interfere with each other value.
But how can this happen?
Is there any example of such kind of sources ?
And does they follow ohms law?


texts: Does NVIDIA Tegra SoC's and AMD Fusion APU's bypass the GPUCPU memory transfer bottleneck?

texts: The major limitation in heterogeneous CPU+GPU programming seems to be the slow memory transfer across the PCI-e bus when data needs to be passed back and forth between the Device and Host.  I have read that the goal of AMD's Fusion APU's is to solve this problem.  Does the Fusion APU attempt to solve this problem by having the GPU and CPU share a common physical memory region?  And what I am really wondering is if the Tegra K1 (or X1) also attempt to solve this problem by having the CPU and GPU share a common physical memory region, therefore not needing to perform a cudaMemcpy.


texts:
I am controlling a servo motor using the PIC12F675. The servo rotates in opposite directions.

I controlling the servo as follows:

if(GPIO & (1<<3))
        {
                GPIO |=(1<<2);
            __delay_ms(1);
            GPIO &=~(1<<2);

            }
            else
        {
                GPIO |=(1<<2);
            __delay_ms(2);
            GPIO &=~(1<<2);

            }

            __delay_ms(18);

I would like to control the rate at which the servo reaches the opposite ends. I tried looking for articles related to speed control, I found it to be too complicated to control the rate of sweep. I am looking for suggestions for the same


texts:
I have a few questions:

To measure the ion current in air plasma from a source that works in pulses, what method is best for ion current measurements?  Is it by using a Rogowski coil or by measuring across a resistance (ie. like faraday cup) and why?
What method do you recommend for measuring negative ion current?
What method do you recommend for separating negative ions and electrons?


texts:
simulate this circuit – Schematic created using CircuitLab

I can only solve this using Kirchhoff Laws and Ohm's Law.
The first thing i tried was finding the current through R3 ,
Ir3=1mA (Ir3 = 12/12.10^3 = 1mA).
Then using KCL on node A: Ir2 = Ir3 + Ir1 <=> 2 = 1 + Ir1 <=> Ir1 = 1mA.
And finally using KVL  to find Vs : -Vs+R1*Ir1+R2*(Ir1-Ir3)=0<=>-Vs+6+6(1-1)=0<=>-Vs =-6<=> Vs=6.(Which is wrong) But i can't get the correct answer, i suspect im doing wrong the KVL  and i've been trying for the last hour different things . Appreciate any help...(I know the correct answer ,which is 24V, in my question i expected someone to point where in my logic it went wrong to get a different answer)


texts:
In similarity to previous question Ron setting of LDO. Unfortunately I assumed gain of the error amplifier and trial and error method I matched with dropout curve in the datasheet.

Query: How to extract gain of error amplifier from LDO datasheet and what data is required to be understood or procured to set Ron of pass element (PMOS) in LDO. (I felt this is inter-related).I am assuming there is a generic LDO which will help for modifications.

I am assuming this is the initial step in understanding the modeling of LDO. Building a loop then adding features to it.


texts: Any IC similar to ULN2003A with latch or enable/disable?

texts:
I'm working on a project that uses a ULN2003A  (darlington transistor array) and I need to enable/disable it. The point is that ULN2003A does not have enable/disable pin.

I think that a IC with latch would do also the job. I've found TLC59213, that could do the job but si a quite rare IC.

Does anyone knows a darlington transistor array IC with enable/disable pin or a latch more common than TLC59213?

Thanks


texts: Checking overlow after addition of 2 integers in 2's complement form

texts:
Q) Let an−1an−2...a0 and bn−1bn−2...b0 denote the 2’s complement representation of two integers A and B respectively. Addition of A and B yields a sum S=sn−1sn−2...s0.The outgoing carry generated at the most significant bit position, if any, is ignored. Show that an overflow (incorrect addition result) will occur only if the following Boolean condition holds:
(~sn−1)⊕(an−1sn−1)=bn−1(sn−1⊕an−1)

where ⊕ denotes the Boolean XOR operation and ~ denotes the boolean NOT operation. You may use the Boolean identity: X+Y=X⊕Y⊕(XY) to prove your result.

My Attempt :- When an−1bn−1(~sn−1) + (~an−1)∗(~bn−1)∗sn−1 is 1 then overflow OCCURS otherwise no overflow. Means when 2 positive numbers are added and answer is negative and when 2 negative numbers are added and answer is positive then overflow occurs otherwise it does not occur.
Here,
(~sn−1)⊕(an−1sn−1)=bn−1(sn−1⊕an−1)
 (sn−1)(an−1sn−1) + (~sn−1)(~(an−1sn−1))= bn−1(sn−1(~an−1)+ an−1(~sn−1))
After solving further, I am getting finally :-
sn−1an−1 + (~sn−1) = bn−1sn−1(~an−1) + bn−1an−1(~sn−1)

I don't know how to solve further to get the desired result and I also don't know whther I am going in right direction or not. Please help.


texts: Hole and pad size standard for wires soldered in through holes

texts:
Is there a standard that gives the hole and pad size for soldering a wire to a PCB?

The IPC-7251 standard gives hole and land diameters for a given lead diameter. But because the finished hole diameter is 0.25 mm bigger than wire, these holes are difficult to get stranded wires into without them unraveling.

I cannot use a connector for this application.


texts:
I'm trying to design a 5V UPS. Power to load should switch if line voltage falls below about 4V. Battery voltage may be from 3.8 to 5V. I'm simulating in LTSpiceIV.

I'll be using mosfets to supply battery power to avoid schottky voltage drop. However, the circuit starts to oscillate when line voltage is near 4.4V. Will this be a problem during actual use? Also, how can I replace the other schottky with mosfets? I think the high gain of the op amp in the tl431 may be causing the oscillation, but am not sure. Circuit simulates fine with a schottky instead of the first mosfet after the battery.

I don't have much experience with this. All suggestions will be appreciated.

I added 2 more mosfets and got this. Still oscillates when line voltage is cycled, but seems to simulate ok when I use fixed DV voltages for V1. I wonder if this is a LTSpice quirk, or the timesteps are too small, or if it's a genuine problem.. some race condition which will occur in reality. Power switches to battery when line voltage drops below 4.21V.


texts: How can I estimate the optical power that a single-color LED generates?

texts:
This excellent answer addresses the Luminous efficiency and Luminous efficacy of LED lighting, but these are based on human vision and it's variability with wavelength. It's a good idea to read it.

I'd like to be able to convert these to absolute efficiency, which would be the ratio of optical power out to electrical power in. If I put 5W of electrical power into an LED and it produces 3W of light, then the absolute efficiency is 60%, and incidentally I will also know that I have about 5 - 3 = 2W of heat to manage.

Question: How can I at least estimate the optical power that a single-color LED radiates given the typical parameters - say luminous intensity in Candela or Luminous efficiency - from a data sheet? Assume this is a narrow-band LED and can be characterized by a single wavelength, \$ \lambda\$, to keep the solution from getting too complicated.


texts: Why is the number 63 popular in electronics?

texts:
Capacitors have a voltage of 63V (not 60 or 65).
Fuses have a value of 63A (not 60 or 65).
And there exist more odd values in electronics...
Who knows the history of this convention?


texts: How to flash LEDs with a microcontroller?

texts:
What I'm planning to do is program a microcontroller to keep track of time and flash LED lights.

The features I would need:

Decrease/increase interval between flashes
Flash specific LED lights (there will be two different LED colors)
Flash multiple LED light simultaneously
The ability to space the furtherest LED lights ~6" across from eachother (Lights will be in a single line)

I'm planning on buying Arduino Uno, and these LED lights. I would use a max of 6 LEDS at once.

Would this be all I need to do this?


texts: Determine current and voltage for the given diode circuit

texts:
Q. Cutin voltage for each diode=0.7V.

Determine current throught D1 and Vo for

(a) R1=10 kohm, R2 =5 kohm. Ans(I(D1)=0.93 mA, Vo=-15V)

(b) R1=5 kohm, R2 =10 kohm. Ans(I(D1)=1.86 mA, Vo=-15V)

simulate this circuit – Schematic created using CircuitLab

My approach

(a)First considering both the diodes connect.

Let the voltage of the node where n terminal of the diode D2 is connected be v. For each diode there is a forward voltage drop is 0.7 v

=>v=0.7v

I(10k) =(10-0.7)/10 mA=0.93 mA.

I(D2)=(-15-0.7-0.7)/5=-3.28mA

=> D2 is off

I(D1)=I(10k) + I(D2)=0.93-3.28=-ve

=> D1 is off too.

But according to book D1 is on D2 is off. Where have I gone wrong.

(b)Followed the same procedure as above for (b) and got the right answer.

Still showing the steps:

First considering both the diodes connect.

Let the voltage of the node where n terminal of the diode D2 is connected be v. For each diode there is a forward voltage drop is 0.7 v

=>v=0.7v

I(10k) =(10-0.7)/5 mA=1.86 mA.

I(D2)=(-15-0.7-0.7)/10=-1.64mA

=> D2 is off

I(D1)=I(10k) + I(D2)=1.86-1.64=+ve

=> D1 is on.

Therefore

I(D1)=(10-0.7)/5=1.86 mA
Vo=-15V

Which matches with the answer.

Please tell me if my procedure is wrong. As by following this procedure I am getting the right answer for (b) but not for (a)


texts: Difference between RS PRO 846-171 and INA125P for strain gauge amplification?

texts:
I am implementing a solution to read several strain gauges at once.  Since I am using RS as my provider, I was about to buy the RS PRO 846-171 chip which is an amplifier specifically designed for strain gauges.

RS PRO 846-171 datasheet

INA125P datasheet

However, it's quite expensive, and I need like 5 of them, and after some more research I saw that most people use the INA125P chip, which is about 1/5 the price.  However, I cannot see what the difference between these two chips, they seem pretty equivalent.

Moreover, I am curious what does the INA125P even do that I can't do with a 20-cent op-amp?  Considering the INA125P is about 10€ and the RS chip is about 50€, I am a bit confused as to the difference in magnitude of cost when they all seem to do the same thing -- amplify a small voltage difference.

Thanks.


texts: Is it damaging to drain an Eaton HS Supercapacitor below its minimum working voltage?

texts:
I have a Eaton HS Supercapacitor that is rated at a maximum of 3.8V, but I noticed on the data sheet there is a "Minimum working voltage 2.2 V". Will using the capacitor to power a boost converter that will drain it below 2.2V be damaging to the cap?
https://www.mouser.com/datasheet/2/87/Eaton_supercapacitor-hybrid-cylindrical-cells-data-1847238.pdf


texts:
I have in hexadecimal representation a IEEE-754 Floating Point:
uint32_t _u_IEEE_754 = 0x41100000; //9.0

The decimal representation is: 9.0
I am working in C under embedded system.
I want to get the integer and decimal part separately, from the number in hexadecimal. I can't use floating point. I have no idea where to start. Which idea would be of great help to me.


texts: What graphic chips could be used with a W65C816

texts: I'd like to build an 80's type computer using the W65C816 CPU. If possible, I'd like to use a dedicated graphics chip, and would prefer to avoid going the FPGA route. Could anyone suggest what I should start looking for, or recommend any currently produced chips that might work? Sincere thanks in advance.


texts: Do I need buffer amps and zeners for SPI pins in a tiny IC chip?

texts:
I am currently working on a project using the MMA9555L pedometer chip (from Freescale Semiconductor Inc.) and establishing communications through an SPI bus going into an Arduino Uno. Below is a picture of the circuit I intend to use initially which is from the data sheet of the chip.

Before I power it up I am not sure about one thing. Arduino pins outputs 5V for digital signals however all the IO and SPI pins in this chip works at 1.8V. Will I need Zener diodes or voltage regulators as well as an Opamp in buffer amp configuration (to make sure current is limited) for each of the data pins? For reference, I will be doing the initial testing on a breadboard so no fancy (small form factor) components initially.

Sorry if my question sounds silly, I am only a mechanical engineer and do not have much experience with IC circuitry.


texts: Most compact high voltage source for making long arcs

texts: Out of curiosity, I have a question about high voltage electricity sources. Hypothetically, the requirements are that the source must be no larger than a water bottle (although smaller is better), and that the source is capable of producing an arc at least 1 meter in length (longer is better). The source doesn't have to be able to output continuously and can be pulsed, although the time between pulses should be no longer than 1/2 of a second. I am aware that tesla coils can produce large sparks in small packages, but I do not know if they would be the best option for the hypothetical situation or if they are even capable of meeting these criteria. Perhaps some sort of capacitor array?


texts: MOSFET-switching between two power supplys: how to avoid transverse current?

texts:
For a hobby project I would like to switch between two power supplys.
The two power supplys are two 6s LiPo batteries. If one battery is empty i want to immediatelly switch to the other battery. (the load is a motor)
For switching a 90A, 2.2mOhm n-channel MOSFET with a highside driver will be used.
I already did some research and made a first schematic drawing:

The maximum current is about 50A and the battery voltage varies between 18V (empty) and 25V (full).

So if e.g. BATT. 2A is empty (18V) and BATT. 2B is full (25V) and Q1 is therefore switched off and Q3 on (to only use the full battery), there is about 25V potential at the source of Q3 (and hence 25V at source of Q1), but only 18V at drain of Q1.
So there is a difference of -7V between source and drain of Q1 and the parasitic diode of Q1 between source and drain will probably conduct which leads to an short circuit (at over 100A battery current for a short time, so the MOFET will be destroyed).

How can I avoid that transverse current?

Thank you for any help in advance!


texts: How to make my sound reactive LEDs with Tip31C work?

texts:
I am building a rhythmic led headphone prototype, but unfortunately I am missing something or am doing something wrong because my project is not working properly.
The project is as follows:
I bought
   - A pair of one dollar headphones.
   - Two tip31c transistors.
   - One pam8403 module, to improve the signal of the two channels.
   - Two 5v led plates for both right and left channels
   - A usb cable.

I am using this diagram:

But something went wrong, because the pam8403 only works disconnecting the tip, i've test the output right and left channel of pam8403 and works fine with speakers of test, but when i connect the tip31c in one or both channels it makes a (bip a sound hit in bot out channels) that it repeats infinitely, and the leds are blinking in a static secuense repeatly infinitely, and not with all power, not following the music or music signal provided by the audio input plug...

I dont know if is a problem of pam8403 or tip31c, important i need pam8403 because not all devices have the full power....

Can someone guide me?, i'm really noob in this...


texts: Arduino as modbus master with MAX485 doesn't get any response

texts:
I'm having some troubles trying to query a modbus slave with an Arduino through RS485.

I've already succeeded in querying a software modbus slave running on my PC through the USB/COM port using the ModbusMaster libray, hence it shouldn't be a software issue.

I read about TTL and level conversions and I put on a circuit like this on a breadboard:

Using the same firmware/sketch that worked for the software slave, I connected the arduino pin TX and RX to the max485 and A and B to the modbus slave and I issued several requests.

I can see the signals converted by the MAX485 (CPA1114) though the oscilloscope and it seems to be right. The led on the modbus slave lights on as it sees a modbus transaction. Still, what I read as result of the request is always 0xE0 (invalid slave id) or 0xE2 (timeout).

I queried the slave with the same equal request using another tool (a RS485/USB converter and CAS Modbus Scanner), and it gives the expected results, that is data 0x01.

This is the code I'm running on an Arduino Ethernet (with a display for debug purpose):

#include <ModbusMaster.h>
#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 4, 5, 6, 7);

ModbusMaster node(1);

void setup() {

  pinMode(3, OUTPUT);
  node.begin(19200);
  lcd.begin(16, 2);

}

void loop() {

  uint16_t m_startAddress=1;
  uint8_t m_length=1;
  uint8_t result;

  digitalWrite(3, HIGH); // TX
  result = node.readHoldingRegisters(m_startAddress, m_length);

  lcd.clear();

  if (result == node.ku8MBSuccess) {
    lcd.print("DATA:");
    digitalWrite(3, LOW); // RX
    for (uint8_t j = 0; j < m_length; j++) lcd.print( node.getResponseBuffer(j), HEX );
  } else {
    lcd.print("ERR ");
    lcd.print(result, HEX);
  }

  delay(500);

}

These are the request signals emitted by the Arduino, that always fail to get a data response, and the other tool, that always succeed:

Arduino request signal

USB/RS485 converter signal

Overlap of the two signals

Is there something wrong with the request signal? Am I making any mistakes in the circuit or the code?

Any pointers would be greatly appreciated.

EDIT:

As suggested by Kvegaoro, I got it working by editing the ModbusMaster library in order to switch the D3 pin to the right status at the right moment. For doing so I used some code I found on this post (italian) in the Arduino forum.

This is the edit I've done in ModbusMaster.cpp, function ModbusMasterTransaction, starting at line 746:

  // code edited to work with MAX485:
  // transmit request
  UCSR0A=UCSR0A |(1 << TXC0);
  Serial.flush();
  digitalWrite(3, HIGH);

  for (i = 0; i < u8ModbusADUSize; i++)
  {
#if defined(ARDUINO) && ARDUINO >= 100
    MBSerial.write(u8ModbusADU[i]);
#else
    MBSerial.print(u8ModbusADU[i], BYTE);
#endif
  }
  while (!(UCSR0A & (1 << TXC0)));
  digitalWrite(3, LOW);
  // --

  u8ModbusADUSize = 0;

Note that the D3 pin is then hard-coded in the library so this is not a good design, if someone is going to need this would adjust it better. It works though!


texts: Comparing 2 op-amps to find out which one is most suitable to use in circuit design

texts: Ok, so I am designing an amplifier using an op-amp to produce the same undistorted output sinusoidal wave across a  2Kohm load as that of the common emitter amplifier shown in the attached picture. I have researched online on what specific op-amps I can use and cannot decide whether I should use an LM741/A or LF351 op-amp. The other pictures attached are the datasheets for both op-amps. Any advice on which op-amp I should use? That will be greatly appreciated.


texts: I could not understand the logic of this circuit, connecting an inductor to the supply what will change? Considering that C1 acts like a short circuit in AC analysis why do we differentiate x and Vout ? Are not they the same node?! How would the circuit looks like when L1 becomes an open circuit? Why there is a connection between the middle of NMOS and the ground node, and how can we connect the outer middle part of NMOS anyway? Finally, I also did not understand the "limiting factor" part of the question


texts: FPGA Frequency Domain Based Beidou-3 B2a Coarse Acquisition Processor Using FFT

texts: I'm using an ARM+FPGA platform to capture B2a (BeiDou or COMPASS) signals and determine the user position, velocity and precise time (PVT). The C/A frequency of B2a is 10.23MHz. If my sample rate is 20.46MHz, then I should do 32768 points-FFT by FPGA. Give me advise about how to achieve it.


texts: CAN bus split termination impedance - no 60 ohm resistors?

texts:
Typical CAN Bus termination involves a 120Ω resistor between CANH and CAHL. To go further than this, I've read that the 120Ω resistance can be split into two 60 ohm resistors with a capacitor in between to ground (Typically 4.7uF). This has the benefit of creating a low-pass filter for the common-mode noise on the network.

Because 60Ω is not a standard resistor value, is there anything wrong with using 60.4Ω resistors or two 30Ω resistors in series? Or is there another method to accomplish this.


texts: What makes Smartfusion2 FPGA clamed as highly secure to ensure secure booting?

texts: Is the FPGA Smatfusion2 claimed to be highly secure by its manufacturer (Microsemi, now Mircochip) because it is a non volatile memory FPGA?  Meanwhile the SRAM FPGA like the zynq 7000 are considered vulnerable because the content need to be loaded each time power is applied to the system?  Is that enough to ensure secure booting?


texts: Why can't I route the same signal to multiple pins on an STM32F407?

texts:
I have a periodic signal which I want to use as a trigger to two timers - TIM8 and TIM2. When the signal goes high, TIM8 should start running and TIM2 will be clocked once. TIM2 will be configured in external clock mode 2.
I have configured PA0 as external trigger for TIM8 and PA5 as exernal trigger for TIM2, and connected the signal to both pins.

I find that TIM8 does not start, unless I disconnect PA5. As soon as PA5 and PA0 are both connected, TIM8 no longer starts.
I also find that TIM8 starts if I comment the line that configures PA5. In this case PA5 is in a high-Z state by default.

It appears that the signal can only drive a single pin at a time, not multiple pins. Why would this be the case?
The signal I am using can be set at varying drive strengths, I have experimented with all of them and gotten the same result.

PA5 is not connected to anything else on the dev board I am using, and I observed the same behaviour with a few other pins - I tried configuring some other pins on GPIOA as AF inputs and observed TIM8 stop running when both PA0 and the other pins were connected.

The code I am using is as follows:

GPIO_InitTypeDef gpio;
NVIC_InitTypeDef nvic;
GPIO_StructInit(&gpio);

/* Configure PA0 for TIM8 ETR (HSYNC to start pixel clock), datasheet page 62 */
gpio.GPIO_Pin       = GPIO_Pin_0;
gpio.GPIO_Mode      = GPIO_Mode_AF;
gpio.GPIO_Speed     = GPIO_Speed_50MHz;
gpio.GPIO_OType     = GPIO_OType_PP;
gpio.GPIO_PuPd      = GPIO_PuPd_NOPULL;

GPIO_Init(GPIOA, &gpio);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource0, GPIO_AF_TIM8);

/* Configure PA1 for TIM2 CH2 (This will be VSYNC, to reset the timer) */
/* Configure PA5 for TIM2 ETR (External clock, this will be HSYNC to count syncs) */
gpio.GPIO_Pin       = GPIO_Pin_1 | GPIO_Pin_5;
gpio.GPIO_Mode      = GPIO_Mode_AF;
gpio.GPIO_Speed     = GPIO_Speed_50MHz;
gpio.GPIO_OType     = GPIO_OType_PP;
gpio.GPIO_PuPd      = GPIO_PuPd_NOPULL;

GPIO_Init(GPIOA, &gpio); // Works if this is commented
GPIO_PinAFConfig(GPIOA, GPIO_PinSource1, GPIO_AF_TIM2);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_TIM2);

The only explanation I can think of is that PA5 is pulling the line low, preventing PA0 from getting the signal. But if PA5 is configured as an input it should not pull low as it will have a high impedance. So I'm thinking it must be misconfigured, or else damaged. PA0 can also be an ETR for TIM2 and PA0 definitely works, I will try that and see if I can get TIM2 to run. If it does I will suspect the pin


texts:
This question mentioned that pin 13 has a built-in resistor for the LED that comes standard on most Arduino units.  A friend of mine told me that because there's already a resistor on the pin, I don't have to put one on when I plug an external LED into the pin.

This doesn't sit right with me, as I read all over the place that it's very bad to plug in an LED without a current-limiting resistor.  I can't find where pin 13 is on the circuit diagram (still getting used to reading those), so I don't know how the built-in resistor is wired.

Question-in-short: Do I need a current-limiting resistor when using pin 13 for a (small) LED?

EDIT: As Polar pointed out below, a single resistor would do the trick.  However, I'm really curious as to the positioning of this single (built-in) resistor.  If it's in series with the header for P13, then it should limit current.  If it's in parallel, I don't think so.  However, my electronics knowledge isn't that vast, so I could be mistaken...


texts:
I have made a single supply non inverting amplifier. The supply voltage given is 5 V. The schematic is shown.

Now the problem is I am not able to generate 2.5 V accurately which is affecting amplification. The 10 K resistor connected to inverting terminal has to connected to 2.5 V. A resistor divider with opamp buffer is not able to generate 2.5 V accurately.

Is there any other approach to amplify signals about half the supply voltage in single supply circuits?


texts: Single Supply Op - Amp circuit not working

texts:
I have made a circuit like this

I am attempting to convert the -2.5V to +2.5V. I have got this circuit running using +12V and -12V but now intend to run the op amp in single supply mode. But my output is always 11.01 voltage whatever be the input. What am I doing wrong?


texts: connecting a circuit to device through 3.5mm jack

texts:
I want to send an analog signal to pc through 3.5mm mic or line-in jack then i will read samples by some code. so does the jack have a "standard"?

1- for example, for the same signal with different pc -or even an android device- will i get the same samples?

2- what is the maximum current allowed?

3- will the pins -signal and ground- be the same?


texts: I'm working on learning how 8 bit computers work and operate. I know you can make a (tedious) microprocessor with a larg amount of logic gates and such, but how does it read graphics? I know this uses a microprocessor (PIC), but what instructions tell it to draw a pixel at x, y location. I'll go looking into how a monitor works in the mean time.


texts:
First of all, I am going through designing all of this because I did not find a ready made circuitry for my purpose which is mentioned later. If you know a circuitry that is well tested and does what I want, by all means share it.

So I have this circuit:

Bigger picture

It is a computer-soundcard <-> telephone interface with Headphones to monitor.

Power supply is to be a symmetric 9V Power supply. PC Speaker(top-left) is the headphone output jack. The hum is in the headphones(bottom-right).

Two problems:

When connection to PC speaker is plugged in and Telephone connection(bottom-left) is plugged in, I hear humming in the headphones. When only one is plugged in I hear it without distortion.  Sound files showing humming.
(Solved) When playing audio, it is almost not audible on the telephone side, ie, the person I am playing it to cannot hear it.

Please share ideas on how to solve the issues.

If you criticise my circuitry, add something to act as a replacement, too. Just saying that it won't work because of this and that is not as helpful as saying: "It won't work because of X, which is why I recommend doing Y". I try to update this question with the current circuit so you don't have to scroll through all replies to get the current status.

PS: Circuitry for telephone connection taken from a recording interface from Tekniikan Maailma magazine. I chose it to be able to use the circuit in parallel with my current phone.


texts:
I read about the Hall effect and understand its usage in sensors like speedometers, but I also read it can be used as a wattmeter. How can it happen?

In order to calculate power (P) we need to multiply voltage and current.

How does a Hall sensor do that?


texts: Should I be concerned about the test frequency?

texts:
I am using a LMR16006Y buck converter with a 4-65V input to 3.3V output 600mA.
I am a little confused on the choice of the output inductor.
The Y version outputs @ 2.1MHz.
The inductor I am looking at is the SRR1260A-121K.
The test frequency shows 0.796MHz.
What exactly does this relate to?
Do I need to worry about it, or am I completely off base with going with this inductor?


texts:
I have an RC device powered by a 3.7V poly battery, which includes a motor and a 40KHz sonar. The voltage across the sonar sensor is amplified and then adc-ed. The motor is driven by a 2KHz PWM.

When motor is off, everything works well. When motor is on, I have a 2kHz 0.5V drop at VBAT and it's difficult to get rid of this - probably because of long wires to motor. I do have a diode across the 2-wire motor.

Anyway, the big problem is that I also get a 2kHz 10mV spike at the sensor. This creates noise that prevents from analyzing the sonar readings. The signal-to-noise ratio is not big enough.

sensor noise when motor off:

sensor noise when motor on:

I cannot really change the gauge of the motor wires and the VBAT drop doesn't create any other problem. Is there a way I could avoid such noise?


texts: How to check if something is mains earth grounded?

texts:
Suppose I would like to verify that the ground terminal on an indoor power outlet is actually connected to the ground (from what I've read, some of them aren't!). How would I go about checking that?

I ask because I recently purchased an ESD wrist strap, but I know it's useless unless it's actually connected to the earth.


texts: Has the emitter resistor any effect in calculating the base current in a common emitter amplifier?

texts:
It's generally the first step to calculate the collector resistor Rc, according to the operating collector current Ic and collector-emitter voltage Vce required.

Rc = Vce / Ic

or

Rc = Vcc / Ic(max)
both result the same for a Class A amplifier.

In the "hyperphysics" example however it is said that "The resistance Rc+Re determines the maximum collector current..." and

Rc + Re = Vcc / Ic(max).

http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/npnce3.html#c1

I find this site to be a very informative and credible one, so it makes me doubt.


texts:
I'm helping with a kid's Maker's project.  We need to attach some LED's to some coin cell batteries for part of a holiday project.

Are there any conductive adhesives we can use for this?  Durability is not a factor, since the life of the project will be no longer than the life of the coin cell charge.


texts: Intel Altera MAX 10 DEV KIT Interface - Can a RS232 6 pin PMOD module by Digilent be used seamlessly with MAX 10 for PC-FPGA UART communication?

texts:
I am planning to either purchase a MAX 10 or a DE2-115 dev kit to implement communication via both ethernet and RS-232. DE2-115 has both ports soldered onto the board, but MAX-10 has 2 ethernet ports only. On its specs, it says that one can attach a 12-pin Digilent Pmod module to its 12 pin Pmod port. But, the Digilent RS-232 Pmod module states that it can be connected to a board having "6pin UART enabled Pmod port". All I need to know, is whether that module will work with the MAX 10 dev board or not. Am in a situation where any help is great help. I would really appreciate if anyone is familiar with what I'm talking about.

Max 10 - https://www.intel.com/content/www/us/en/programmable/products/boards_and_kits/dev-kits/altera/max-10-fpga-development-kit.html

RS-232 Pmod BY Digilent - https://store.digilentinc.com/pmod-rs232-serial-converter-and-interface-standard/


texts: Is it a good practice to define TRUE/FALSE constants in SystemVerilog?

texts:
Is it a good practice to define TRUE, FALSE, HIGH, LOW, ENABLE and DISABLE constants/defines/parameters in separate file and use them in expression some_reg <= FALSE; instead of  some_reg <= 0; ?
Does this practice have any negative effects?


texts: Need help to identify this PCB connector

texts:
I really need to identify the name of this connector type.
It is the PCB end of a lightning connector on a FLIR thermal camera for IOS.

Mine is just like this but with lightning instead of this USB-C


texts:
After reading many contradictory accounts of the "proper" method, I would like to clear it up: what is the correct method for driving a 4-wire, star configuration hard drive motor?

What I have observed people/companies doing:

Driving the motor using 3 wires and not connecting anything to the Common wire.
Putting half-bridge drivers on all 4 wires.
Setting Common to GND and driving the other 3.
Setting Common to V+ and driving the other 3 open-drain.

Now, I recognize that there may be multiple ways to drive it, but what is the intended method? How are they SUPPOSED to be driven?

For your reference, I am planning to use the HDD motor to build a variable-speed precision driver, which will have optical feedback (i.e. optical tick marks on the platter rim) for the speed control.


texts: P-Channel MOSFET Inrush Current Limiting - Transistor burn issue

texts:
I'm fighting with PFET inrush current limiting circuit discussed here: P-Channel MOSFET Inrush Current Limiting

In my circuit is input voltage 24V DC and C_Load is 6mF. I'm switching on transistor slowly 150 ms => and that limit current quite well (less than 2.5A). But sometimes is transistor fully open during power supply connection => 6mF cap is loaded very quickly and inrush is also very big and that damage transistor. Can somebody help me solve this issue? I'm using the circuit in the picture below.

I did a lot of simulations in LT spice and there is a circuit working well. Transistor never burned in the simulator :)

See results from simulator:
From top to bottom:

Grey = power loss on the transistor
Purple = voltage cross transistor VDS (drain to source)
Magenta = voltage between gate and source
Red = input voltage
Blue = Voltage gate to the ground
Green = current through the drain of transistor

Here are the measurement results:


texts:
I am making a battery powered project which involves bi-directional motor control. However motor needs to turn rarely (about 10-20 seconds in 24 hour period). I am using L298 motor driver. However the quiescent current is in mA range. To reduce current consumption, I am planning to use a mosfet switch as shown in the figure below:

VM = 9 V

VCC = 4.5 V or 6 V (I will decide after a little experiment)

Motor current consumption < 1 A

Whenever I need to use the motor, I will turn the mosfet ON and keep it OFF while the motor is not in use. (I am using logic level mosfet.) The quiescent current of mosfet is in uA range and that's how I am planning to save a lot of battery power.

Will it work?

Any suggestions/improvements are welcome.


texts:
Here's an odd one.  I have a GFCI-protected circuit with a Uninterruptible Power Supply on it.  I've found that when I test the outlets on the circuit with a GFCI outlet tester the tester does not trip the GFCI.  However, when I unplug the UPS from the circuit the tester trips the GFCI as expected.  Why would this be?  The UPS is a Minuteman Entrust 500VA in case it matters.

Note:  I'm am not plugging the tester into the UPS, I am plugging it into either of the 2 "regular outlets" or the actual GFCI outlet.


texts:
I've recently come to suspect the effects of connectors on my measurements. I'm looking at several different ways of de-embedding their effects from measurements that I take with a network analyzer (20-30 GHz).

Here's the thru board I'm trying to deembed

I have 3 questions

1)Is S-parameter Bi-section a reasonable way to see the S-parameters for the DUT using measured data?

2) Given a T-matrix, Y-matrix, and Z-matrix method for solving for the symmetrical matrices, which produces the best result?

3) Given solving for a T-matrix, which of the 4 possible solutions should be used?

First Here's some background reading

Here are my doubts1 as well as here. These links discuss that with real data, S-parameter bisection the process begins to break down with excessive noise and other parasitics. Additionally, if insertion and return loss are too high the results are also inaccurate. Finally with the equations themselves there are several assumptions about symmetry that could ruin the results if symmetry is not kept.

I feel that the assumption of symmetry should work well with just 2 connectors and a trace, and insertion loss and return loss should be reasonable. I'm not sure if real world measurement noise would be an issue

Second, when I look at link 1, the method for bisection differs from 2 and 3. The methods introduced are using T-matrices, Y-matrices, and Z-matrices. Which of these produce the best result?

Finally after assuming that T-matrices (check out link 1) would work the best, I started solving the equations

[[T11,T12], [T21,T22]] * [[T22,T21],[T12,T11]] =  [[T11f,T12f],[T21f,T22f]]

after expanding this ( and assuming T12 = T21) out I get

T11f = T11*T22 + T12^2
T12f = 2*(T11*T12)
T21f = 2*(T22*T12)
T22f = T11*T22 + T12^2

Solving for T12 (second equation) I get

T12  = T12f/(2*T11)

Solving for T22 (third equation)

T22 = T21f/(2*T12)

Finally plugging those into the first equation and solving for S11, I get

T11 = (T11f-T12^2) / T22
T11 = (T11f - T12f^2/4T11^2)/(T21f*T11/T12f)

This reduces down to

T11^4 - (T12f*T11f/T21f)*T11^2 + (T12^3/(4*T21f)) = 0

when I solve this equation I get 4 possible answers. Which should I use?

EDIT *****

I found this link that suggests an easy way to do things is to switch to abcd matrices, then to take the square root. here's some sample code I made using python

import numpy as np
import nport
import scipy
from nport import touchstone

// I imported some files that were saved in a matlab format
// the names are freq and new_data
new_n = nport.NPort(np.array(freq),np.array(new_data),nport.S,50)
abcd2 = new_n.convert('ABCD')

print(abcd2)
new_abcd = []
for i,value in enumerate(abcd2):
    if not i:
        print("START HERE!!!")
        print(value)
    holder = scipy.linalg.sqrtm(value)
    if not i:
        print(holder)
        print(holder.dot(holder))

    new_abcd.append(holder)

newest_n = nport.NPort(np.array(freq),np.array(new_abcd),nport.ABCD)

half = newest_n.convert('S', 50)


texts: What are the 8 wires on this rechargeable lithium-ion battery?

texts:
I am trying to replace a rechargeable lithium ion battery with one that has a longer lifespan when charged. The one I have has 8 wires, but every one I find has 2. It has 3 red, 3 black, 1 yellow, and 1 white.

As you can see:
Rating: 3.7V 2200mAh

Can I replace it with something like this 6000mAh one, from SparkFun?
 https://www.sparkfun.com/products/8484

Thanks, guys!


texts: DS2438 battery monitor: how to connect load

texts:
I am looking at the datasheet for the Maxim DS2438 battery monitor and am confused by this circuit diagram:

How would the load be connected?

If connected between battery + and circuit ground this would result in a voltage across the current sense resistor that is larger on Vsense- than on Vsense+. That does not seem right...


texts: Best way to combine different frequency sinusoids to simulate noise?

texts:
I'm designing a differential amplifier to remove noise from a signal, and I'm trying to verify my design by simulating a noisy input, but I'm not sure how to do this. The diagram below is roughly what I'm trying to achieve. Signal 1 and 2 have different frequencies. Signal 1 is present on both inputs of the amplifier, while signal 2 is only present on one. The amplifier should isolate signal 2, and amplify it at the output Vo.
I've already designed the amplifier, but I'm just not sure what the combining circuit should be? What's the best way to combine the two signals, making sure that they are both still present in the input V2?


texts: Practical vs. theoretical buck converter

texts:
I am currently looking at open loop buck converters. I am running it with the following:

Switching frequency (f) = 62500
Inductance (L) = 100e-6
Input voltage (Vi) = 5
Output current (Io) = 0.06

Using this, I changed the output resistance to observe how the buck behaves for a fixed output current and input voltage and changed the output resistance.
Using this I was able to obtain the following:

There are some things about this I am struggling to understand.
The equation used for CCM, continuous mode is Vo/Vi = duty cycle.
The equation used for DCM, discontinuous mode is
$$\frac{V_o}{V_i} = \frac{1}{1+ \frac{\displaystyle 2fLI_o}{\displaystyle V_i*D^2}}$$
Question 1: Why is it that the data gathered experimentally is different the theoretical one?
Question 2: The buck seems to enter and leave DCM between 0.2 and 0.8. I don't really understand why this is I tried doing it mathematically can't seem to see why this is.
Question 3: Between 0 and 0.2 duty cycle, it seems to be DCM and not CCM. Why is this?
Question 4: Between 0.8 and 1 duty cycle, it seems to be CCM and not DCM. Why is this?


texts: Can I connect my Philips sound system to my Samsung tablet?

texts:
I have a Philips SPA 4310/10 Sound System and I want to connect via 3.5mm jack to my 10" Samsung Galaxy Tab 3 P5200 to listen some music.

Am I at risk of short-circuiting the tablet? Or will everything work fine, giving that the Sound System gets 220V power.


texts: Preservation of power when wiring batteries in series - battery life is reduced if load is kept the same

texts:
This is really just a "sanity check" type question. Am I correct that if you place two batteries in series, that the battery life is effectively halved relative to just one battery, assuming the load is the same?

Suppose that we have two batteries, which are idealized in the sense that they are both at exactly Vcc voltage while the battery is alive, and then drop immediately to 0V when it isn't (rather than a gradual taper as seen in real-life batteries).

As an example, and just to keep the units simple, suppose the battery is at 1V and has a total stored charge of 1 coulomb (or 1 amp-second), corresponding to a total stored energy of 1 joule. Then if we place the leads on a 1 ohm load, we get the following voltage curve:

You can see that the battery provides 1 watt for 1 second, for a total of 1 joule of energy, and then immediately dies.

Now suppose we have two of these batteries in parallel, and again a 1 ohm load. Then the voltage would be the same, but the time duration is doubled:

So you can see we now have 1 watt for 2 seconds, and a total of 2 joules of energy (which is the correct amount for both batteries combined).

Now, suppose we have the two batteries in series, again with a 1 ohm load. Naively, if you just keep the time duration at 1 second, and double the voltage, you get the following graph:

You can see we have 2 volts for 1 second, which is 4 watts of power, and for one second is 4 joules of energy. This is more than the combined rating for both batteries, though, which was 2 joules.

As we can see, the batteries won't be able to last that long. Assuming there is no more than 2 joules total to deliver, the correct curve would look like this:

So you can see that if the batteries are only to be able to give 2 joules total, the battery life must now be half (!!) of the original.

Another way to think of this is that, when stacking batteries in series, the total stored charge (i.e. in amp-hours, mAh, coulombs, etc) is kept the same. If the load is also kept the same, then the current is now doubled, so the batteries both drain twice as fast.

Another way to think of it: if you put two batteries in series, the total stored energy doubles, along with the voltage. But, if the load is kept the same, then the current also doubles, so the power draw is now 4x what it would have been, and the batteries drain twice as fast. Put another way, the power draw scales with the square of the voltage, assuming the resistance is kept the same.

You should get the same results for "non-ideal" batteries with some arbitrary voltage curve V(t) as it is hooked up to some load. With two batteries in parallel, you get that the voltage curve is simply stretched by a factor of 2 along the x-axis (i.e. V(t/2)) and decays twice as slowly. The integral of the square of this function (representing the transmitted energy with a 1-ohm load) is doubled relative to the original, as it should be. With two batteries in series, just doubling the voltage at each time doesn't give the right answer -- that would be 2V(t), but now the integral of the square has quadrupled. Instead, it's 2V(2t) that gives the same area, so that the voltage curve is doubled, but also decays twice as fast.

So my question: is this right? If you place two batteries in series but keep the load the same, the battery life is halved? This should be a basic principle but I never see it stated this way, so I am wondering if I have missed something.