texts: Why does the Tesla battery module capacity not work out in calculation?

texts:
https://www.evwest.com/catalog/product_info.php?products_id=463
I am referring to the Tesla battery module listed in the above link.
It says a single cell has the following specs:
Nominal Voltage = 3.8V
Cell capacity = 3400 mAh
The cells are arranged in 74p6s config, therefore the voltage of the module is 3.8V * 6 = 22.8V
The capacity should be 74 * 3400 mAh = 251,600 mAh or 251.6 Ah, 5.7 kWh
However, in the link, it says the module capacity is 232 Ah, 5.3 kWh
I am unable to figure out why it is mention 232 Ah, 5.3 kWh which doesn't work out in calculation.
Kindly advice
Update 1:
What is bothering me is the consistency of the inconsistency in calculation found in many websites. So I figure there must be something I am missing.
For example
http://store.evtv.me/proddetail.php?prod=TeslaBattModule
https://stealthev.com/product/tesla-module/
Update 2:
Thanks for the valuable inputs everybody. It makes sense to me to think that the manufacturers will limit the module / pack capacity using their Battery Management Systems to prolong lifetime of the cells.
I will just leave it at that. Because I am only working on developing some simulation models I can live with my calculation and set a buffer if needed.


texts: Why is it necessary to know a state of a system?

texts: In a system why is necessary ? why cant we use a simple transfer funtion in an S or Z domain ,to get an input output relation , or as we already know our input and measure our outputs through sensors ?


texts: What frequency/band lends itself to interstellar communication?

texts:
Silly question perhaps... but I got to thinking after reading that the Voyager is now almost out of the heliosheath.

What frequency/band would be suitable to communicate across stellar systems; say, from the Alpha Centauri System to our Solar System? Would the type of star/stars have a bearing on the frequency/band selected?

It's probably not a core electronics question - please feel free to vote to close/delete


texts: Trying to understand this Class D amp (using IR2113) circuit

texts:
I understand the concept of the Class D amp and this circuit, but in this particular case there is one part I just don't get.

What I don't understand is how the low side of the signal should work at the power stage. In case of the high side as I understand when the MOSFET is on, the current can flow from VCC to the load. But at the low side I don't understand how could current flow through the load and the low side MOSFET.

Could you please clarify it? Thanks!

Schematic: https://easyeda.com/omerzaid/New_Project-e38fb4c8918946298058a93ec7ef210a


texts: How can we validate the MCP (multi cycle) settings in SDC if the design is huge?

texts:
Is there any standard method or tool available for validation of the multi cycle paths that are set as part of the SDC file during timing analysis.
For small designs manual validation can be performed but when design becomes bigger with thousands of paths, how can we get confidence on our settings to avoid timing bugs?


texts: TVS Array Clamping With IO Less than Standoff Voltage

texts:
I have 2 IO lines one at +3.000V and the other at -3.000V.  They do not turn on simultaneously. Both Voltage levels are off a precision <1%LDO

Both lines are connected to a bidirectinoal TVS (TPD4E02B04 Pin1/Pin2) which has +/-3.6V Working Voltage.

The moment I have both IOs "ON" ie Active +/- 3.0V the TVS clamps both tho 2.8V and starts sinking current.

Is there a reason for this?  I dont see why this should clamp under +/-3.6V and would really appreciate the explanation.

To clarify. This only happens once I have both pos and neg signals active.  I can turn them on in any order and delay and it still clamps. I can have each individual signal enable with no clamping.

My initial idea is the +/- active combined to crate a 6v Delta but the gnd connection is solid at the tvs


texts: DC voltage source connected to an inductor is a current source?

texts: I was reading about voltage boost converter, where the DC voltage source in series with the inductor is mentioned as a current source. Why is this? Also, an inductor in series with a load resistor is modeled as a current sink. Any explanation to these two would be appreciated.


texts:
I am building an LED based low power strobe light. Currently it is running at 50% duty cycle, which is when I realised, it might not fully work, since if the light is on for half the time, the vibration I am trying to capture would have moved a lot within that time.

Does anyone have any ballpark figures of the duty cycle that strobe lights for physics experiments run at? I tried searching for it but could not get any solid figures (just unitless graphs which seem to suggest around 10%).

So do any of you guys have any idea?


texts: Courses about deploying Linux on embedded systems

texts:
I am a new grad student in EE and am trying to take full advantage of my time here at the uni. I have always wanted to understand how to get Linux running on embedded platforms, but from the outside it looks really arcane. Just some of the things you have to know about are listed below, each with its own rats nest of intricacies:

Boot chains, getting a computer to load/run your kernel code.
Making Linux kernels with drivers for the system
Cross-compilation, development toolchains
Deployment, debugging and communicating through hardware like uart.
Making a userland to do what you want (I suppose when you get here it becomes to application-specific for general discussion)

I might be missing some steps.

What resources can I use to learn about these things?

I had assumed that there would be some classes that give a brief overview of these topics, but looking at the course listings, it seems that there are different levels of 'embedded systems.' Many of the classes focus on software development for extremely limited computers. During undergrad, a famous EE 'embedded systems' class culminated in students programming from scratch their own real-time OS for a hypothetical vending machine. While that is cool, it is not what I am looking for.


texts: Clean vs no-clean for high voltage circuit

texts:
I have a board that has fairly high working voltages up to 100V with small clearances down to 12 mil between the high voltage and ground or low voltage nets.  This is unavoidable because the whole board is tiny and in some cases the HV and low voltage are adjacent pads on the same component.

This is currently assembled using a water wash cleaning step.

Is it possible to assemble this using no-clean?  What are the possible problems with having flux residue on a high voltage board like this? Is it better to clean (with the possible ionic contamination from the detergents) or not clean (with flux residue)?

Also, could I do conformal coating over flux residue?  Some references about this: http://www.circuitinsight.com/programs/51472.html
https://aimsolder.com/technical-articles/conformal-coating-over-no-clean

Note: In this case, signal integrity (as on high speed boards) is not much of a concern; failure modes involving a high voltage to low voltage net short are.  1mA leakage from 100V to the microcontroller on the board would be bad; even 0.1mA would still result in very abnormal operation, although the board would survive.  The board may be exposed to high humidity environments, so there may be condensation, although there wouldn't (normally) be direct water immersion.


texts: How to get J/K counter to count from 2 - 9?

texts: I have made this asynchronous counter (must be asynchronous) that using J/K flip flops that has to count from 2 to 9 and then reset to 2 and so on. I have managed to get it to count from 0 to 9, but I now have not been able to get it to start on 2. Please help!!


texts: What must be rated maximum voltage of the boot-strap capacitor of a high-side MOSFET driver?

texts: What is the maximum voltage that appears on a boot-strap capacitor? For example, in this circuit, does \$C_B\$ ever charge to a voltage level near \$600V \pm V_{cc}\$ ? Or does it charge to \$V_{cc}\$ at most?


texts: Can I use the ATtiny84 ADC0 pin as both input and output?

texts:
I am using the ADC0 (PA0) pin of an Attiny84 to read analog values from an audio circuit. This part is working fine. Since I need to connect the Attiny84 to 8 LEDs, I'd like to use the ADC0 pin as an output also.

Here is the schematic:

simulate this circuit – Schematic created using CircuitLab

But this doesn't work. The LEDs don't light up. (They are turned on based on ADC0 values read in.)

Does this have something to do with enabling pull-ups?

Or is it not possible to switch ADC0 between input and output?

Here is the code:

// set pin as input
DDRA &= ~(1 << PA0);

// unset DIDR0
DIDR0 &= (1 << ADC0D);

// enable ADC
ADCSRA |= (1 << ADEN);

// start conversion
ADCSRA |= (1 << ADSC);
// loop till done
while(ADCSRA & (1 << ADSC));

// use h/l regs
unsigned char adcl = ADCL;
unsigned char adch = ADCH;
int result = (adch << 8) | adcl;

// set DIDR0
DIDR0 |= ~(1 << ADC0D);

// set pin as output
DDRA |= (1 << PA0);

// switch LED on
PORTA |= (1 << PA0);

// switch other LEDs on which have been set as output
//...
PORTA |= (1 << PA1);

The above code is being called from the 8-bit timer overflow interrupt handler. The timer is setup from main() as follows:

// set 8-bit timer
  cli();

  // set prescaler to 256
  TCCR0B |= (1 << CS02);
  // set overflow interrupt enable
  TIMSK0 |= (1 << TOIE0);

  sei();


texts: How do different kinds of vacuum pick-up tools compare?

texts:
My company has extensive experience assembling through-hole PCBs, but relatively little experience with SMT. I've just been introduced to the idea of vacuum pick-up tools for SMT components. (Examples here.) This looks like a huge improvement over tweezers! There seems to be quite some variation in these tools. There are unpowered squeeze bulb models, battery powered models, and AC models. Cost ranges from $5 to $625. (More if you get a manual pick-and-place, but I'm not looking at those right now.)

What should I look for in these tools? What specs have an effect on the results during use?


texts: Can I power up a router with a phone charger?

texts:
Today, the charger for the modem for my cable-internet connection went dead. With shops closed due to coronavirus, I thought I would cut the connector from it, connect the two cables inside it with a cut USB-A to microUSB cable (leaving the USB-A in place) and use a phone charger. And so I did. Alas, it was apparently not enough to power on the modem - the diods would light up but I would not get a connection. The sticker on the modem says it needs 12 V at 1 A. I also have a router (that I actually use to cover my flat with wifi signal) whose sticker says 12 V at 2 A and that also did not work. I have another older and slower router labeled 9 V at 0.6 A that could work with this cable but it is slow and could only hold connection to three devices at the time (and we have at least nine in the house). I used a charger that says it can output 5 V at 2 A, 7 V at 1.67 A, 5 V at 2 A and 12V at 1.25 A (presumably using a usb-C cable).

Now, would using a different cable change things? I could cut a USB-C to USB-A cable. Pre-USB-C cables are all the same, are they not?

Would using a different charger change things? If I understand it correctly, that needs a "smart" device on the other end to support higher power, right?

In the end, I got a second hand charger (and ventured out) rated at 1.2A at 5V. Interestingly enough, it can power up the router (12V at 2A) and not the modem (12V at 1A) - I guess that is because the router only uses that power when USB devices are attached to it (it has two USB ports). Is that hunch correct?


texts: Electronic component that detects angular rotation like a potentiometer, but endless and digital

texts:
I am relatively new to this whole scene but am wanting to start a small project sending midi-signals from a board I am creating.
That said, I am a big fan of these endless, smooth digital potentiometers for example built into the Novation Circuit.
Im am having trouble finding these things for sale as I am not sure what exactly these are called. I found - sorry for the direct and probably wrong translation - "digital increment-givers", but reading into it the ones I found have sort of a grid, like giving 20 signals in the course of one rotation.

As I understand it, the ones I would need keep giving a consistent signal. Are these the droids I am looking for or are there different ones?

I could imagine if these are the ones I need that I would listen to the incremental signals and then add or subtract one depending on the rotation.


texts: Why vectored interrupts are not possible?

texts:
vectored interrupts are not possible if a cpu has single interrupt request line and single interrupt grant line while multiple interrupting devices are possible .

Is the above statement is correct if yes then how.I am not very good in microprocessor but understand basic concepts.So if it is silly then please let me know?


texts: Could somebody tell me which resistor to use with this LED

texts:
I went to my local electronics store and asked for a powerful LED because I wanna make a small flashlight. They gave me this thing, but the problem is that the stores in my area don't have any datasheets or anything of the like. When I asked about the current or forward voltage they just told me they don't know and that I should try several resistors and stick to the one that doesn't burn the LED... (basically trial and error because they don't bother with that datasheet stuff...).

So... perhaps could somebody here give me an idea as to what kind of resistor I should use with this thing?

I am using 2 3-volt lithium batteries (CR2016) to provide 6 volts. The guys at the store know that the maximum voltage that the LED can withstand is 3V because they burned 2 LEDs in front of me when I asked about the voltage...

Here are the front and back views of this thing. The metal thingy is supposed to be a dissipator:


texts: Replacing an old dart board ribbon connector - need advice

texts:
I hope this makes sense but I have an old dart board that is having some issues I believe is related to the cable in the link below. The cable is a ribbon cable I believe and toward the bottom there is some damage. I tried to tape tightly to create contact but it’s flakey.

I want to cut the ribbon above the injury and then attach the same type of connector, reseat and try to see if that fixes things.

Question 1 - Can I do that?
Question 2 - Does anyone know what type of connector replacement I would get or where to get it.

I have searched the internet for 19 pin replacement female ribbon connectors and don’t see anything that seems to work where I would insert the freshly cut end of the cable, clamp it down to make contact and then plug it in.

Any help or advice would be very, very welcome :)

https://photos.app.goo.gl/o9PQ6XdoBKgjy7WP6

Thanks!

JJO


texts: How should I understand this twin coil relay pinout? (Screenshot)

texts:
I'm currently looking on an automotive twin coil relay. The Datasheet gives me following schematic:

My Question is: How could I test this relay? In other cases I put the corresponding Voltage on the coil pins and I could hear the changing sound, but where is the coil in this case?


texts: how can i make a 5 bit binary display (hex2dec) sheet

texts:
hey guys i need help with hexadecimal to decimal conversion display for 5 bit number
i can only do it for a 4 bit , since im using a 4bit binary adder ,please help
me to do it for a 5 bits , here my truth table


texts:
I am designing a Li Poly charger circuitry using the BQ24170 chip.

I am connecting a bench power supply instead of an adaptor to monitor the current consumption. Also I am using a 2S Li Poly battery pack. I found that I had connected the CELL pin in the FB configuration which is wrong as I am using the BQ24170. So the CELL pin should be kept floating for 2S battery pack.
Hence-forth I removed the R11 and R18. But it still does not charge. The chip datasheet states the following -

The following conditions have to be valid before charging is enabled:

ISET pin above 120mV
Device is not in Under-Voltage-Lock-Out (UVLO) mode (i.e. VAVCC >
VUVLO)
Device is not in SLEEP mode (i.e. VAVCC > VSRN)
OVPSET voltage is between 0.5V and 1.6V to qualify the adapter
1.5s delay is complete after initial power-up
REGN LDO and VREF LDO voltages are at correct levels
Thermal Shut down (TSHUT) is not valid
TS fault is not detected
ACFET turns on (See System Power Selector for details)

I am using a 10K resistor for the RT1 thermistor.
Two conditions from the above are not met in my design -

Pin OVPSET - gives me 2.48 where as it should be between 0.5 and 1.6.
and ACFET should be turned on which is not.

ACFET is not turned on. This means that ACDRV pin voltage is not enough and therefore the MOSFET Q2 is not ON. I see that R165 and C62 should be connected between the Source and the GATE of the MOSFET which is not so.

Is there any other issue which is not spotted by me please. ANt pointers will be welcome. The MOSFET used are CSD17313Q2.

One of the application engineers state that-

" The bq24170 only supports 4.2V/cell, but you can use the bq24172 if you would like an adjustable cell voltage such as for Li-Po battery. "

Does it mean that once charging using the BQ24170 starts , it stops only when the voltage in each battery is 4.2V/cell ?
And that if I use BQ24172 I can stop charging it when the voltage reaches 3.7V/batter, right ? BTW , I am using a 2S battery which is giving me 5.6V.


texts: Does Level Shifting for I2C also work for UART?

texts:
This is a widely used circuit for level-shifting I2C signals that will be familiar to many of us here:

simulate this circuit – Schematic created using CircuitLab

Can it be used for shifting UART signals at, say 9600 baud as well? The simulator doesn't see any problems with that idea. Obviously, UART is not a bus topology, but if you isolated this as a circuit between two devices and used one for RX and one for TX would you foresee any problems in doing that?

I recognize that the pull-up resistors don't serve a purpose in a UART context either (because it's a push-pull driver). But I'm thinking about sharing this level shifting circuit electrically in a context where I might be switching back and forth between open-collector and push-pull drivers (UART / I2C).


texts: I want to multiplex 8 input lines but have 2 output lines. I'll have two select lines, based on which, the output lines will carry 1st-and-2nd or 3th-and-4th or 5th-and-6th or 7th-and-8th input lines. Is there a component I can directly use for this application or will I have to build this using two separate normal 4 to 1 multiplexers?


texts: Is it possible to use SIM7600 modem for both data and SMS simultaneously?

texts:
I am interested in using the SIM7600 module for designing a system with LTE communication. The module will be connected to the host system via USB.
I would like the host system's Linux to use PPP to connect to the internet via the module and to be able to send/receive SMS at the same time. So, I will need at least 2 USB virtual ports for these two capabilities. I've seen in the hardware design document that 4 virtual ports are available: audio, AT, diagnostics and NMEA. I guess the AT port will be used for the PPP connection.
So, are there other virtual ports (different from the 4 above) I can use for SMS AT commands, or can I use one of the remaining 3?


texts: Why don't the current readings fall to zero after unplugging the charger?

texts:
I use an automatic charger to charge my lead acid battery. After the battery is fully charged, it shifts to maintain mode where the charging current reduces to as low as 13 mA. I noticed that even after I unplugged the charger, while still connected to the battery, the charging current didn't fall to zero but stayed at 13 mA.

Is this normal?
If eventually there is still a “non-zero reading“ for the current, would it cause a spark when I'm removing the charger clips?
If such spark happens to occur, would it favor a bigger problem as exploding the battery due to ignition of hydrogen generated if the battery has been overcharged?

The battery is 12 V and is being charged by a Motomaster charger on its automatic 2 A setting. Current before turning it on is 0.001 A.
This is a photo of the charging setup:
Before Charging - check DMM for Voltage and Clamp-DMM for Current:

After charging, with same measuring setup as previous photo:


texts: I'm not very experienced/knowledgeable in electronics so this may be a bit of a dumb question. I'm building a carbon fiber filament winder for which I need to be actively controlling the tension in the filament. The filament is pulled off the rotating reel and then goes over a pulley connected to load cells which measure the tension. Each reel of filament is connected to a brushless dc motor with an encoder, and the load cells and motors are in a feedback loop controlled by an Arduino Uno. The filament is being pulled by the winder itself, so the motors are just there to resist the rotation of each reel and provide tension. I'm not entirely sure how to control the resistance in these motors though, so if anyone has any ideas that would be much appreciated. I've been told that I can connect a large resistor across the motor's power leads and vary the PWM input to control resistance, would this work? Thanks!


texts:
I have extracted an IR remote reciever from a device. The only prescription on it is: 4344S

On the back its mentioned A-Z.

Generally, a question for the wise. How do people in industry search for products for reverse engineering if they dont know anything about a component?


texts: Creating random PCB ID via manufacturing process

texts:
I often purchase prototype PCBAs on the order of five to twenty pieces and need to uniquely identify them sans software.  I usually just whip out a permanent marker and label SN 00, SN 01, and so on.  But how could I design a board to have (pseudo?-)randomly-generated IDs visible to the naked eye?

An example I thought of was something like a glob of solder paste in the middle of a bunch of exposed-copper 'fingers', such that when the solder paste melts it wicks and bridges into 'random' paths.  Any other ideas or suggestions?


texts: Help Needed with Voltage Controlled Synth Circuit

texts:
I am  building a somewhat out-of-the-ordinary guitar pedal that involves some synth elements, namely controlled voltage.  I'm a little confused by something that I suspect is actually pretty basic.

I am pretty comfortable with circuit diagrams for guitar distortion and overdrive effects, but this pedal uses controlled voltage, and I am being thrown off by the "CV1" and "CV2" markings on the linear pots on the upper left.  As I have no experience with controlled voltage audio, I don't actually know WHERE or WHAT to connect these leads to.  I understand these to be Controlled Voltage 1 and Controlled Voltage 2, but I am uncertain of what these represent in terms of the audio components, and where they lead to/from.  As they terminate in X markings, they don't resemble the other voltage markings on the schematic, this is also confusing.

THIS is the circuit diagram I'm working from.

This is probably a pretty nooby question, but I appreciate any and all help!


texts: Quick release connectors - 2 poles, max 1.5kW 12V DC?

texts:
What quick release connectors are good for connecting 2 pairs of wires?

2 poles

Max 1.5kW

12V

DC?
(optional)

Splashproof


texts: Language/file format for circuit-diagram description

texts:
Is there any language/file format that can describe the block circuit diagram?
For example, the following circuit diagram

might be represented by something like:

A {
  P00: VDD,
  P01,
  P02: GND,
  P10: GPIO output B.P00
  P11: GPIO input B.P01
  P12: GPIO output R0
}

B {
  P00: GPIO input A.P10,
  P01: GPIO output A.P11,
  P10,
  P11,
}

R0 (A.P12, LED0)

LED0 {
  +: R0,
  -: GND
}


texts: How would you calculate the Mandelbrot set in hardware?

texts:
I'd like to build a small novelty circuit that calculates the Mandelbrot set and displays it on an array of LEDs. The minimum floating point math would not necessarily require complex numbers (just calculate \$x\$ and \$y\$ separately) and the total number of individual calculations of \$z_{n+1}=z_n^2+c\$ would be under one million, so even something as slow as ten million FLOPS per hour would be OK in this case. At this level, it looks like 16 bit math is almost enough with clever programming, 32-bits is enough to make it work. Floats rather than ints would make life a heck of a lot easier, but not required.

I believe that a Raspberry Pi would be overkill as would a high-end Arduino, so an Uno, or a Basic Stamp II with its FP coprocessor perhaps.

That exhausts my knowledge of the possibilities, but there must be other options out there. How would you go about designing a small circuit to do this? What type of circuit would you use?

Background question, and the first ever published image of the Mandelbrot set (1978):


texts: Impedance matching for maximum power transfer

texts: I have a simple circuit as below. Assuming that all components are ideal. With R2 and L1 are fixed, is there a switching frequency so that the voltage at node labeled VTH is constant (or relatively constant) and equal to V1/2 or 1.5V when switch is ON?


texts: Drive a common anode bi color LED using single microcontroller pin

texts:
I have a bi color Red-Green LED with 3 legs (Common Anode).

How can I drive the LED using a single pin from microcontroller (ATtiny45) without using any external logic gates?

I only need red or green at a time mutually exclusive. Combined color/Off state not needed. They are just for status indicators and need to be as bright as possible.

Any schematic using discrete components would be helpful.


texts: How to select the right Operational Amplifier as an impedance converter?

texts:
I have a receiver circuit that is magnetically coupled via a parallel resonant circuit with the sender (similar to RFID but just one directional). I want to feed the signal into an ADC which has, according to the datasheet, an input impedance of around 5 kOhm.

I measured the voltage across the resonant circuit with an amplitude of about 60mV when using an oscilloscope that has an input resistance of 1 MOhm. Obviously, the measured voltage is going to be a lot less when using the low input resistance of the ADC. This is why I decided to use an impedance converter before the ADC:

simulate this circuit – Schematic created using CircuitLab
Note: V1 isn't an actual voltage source, it's just there to point out that there is a voltage induced there. The opamp is powered from +5V.

When measuring the output voltage of the impedance converter, I get a signal that is very chopped up like so:

I'm using a MAX492 Opamp (https://datasheets.maximintegrated.com/en/ds/MAX492-MAX495.pdf). The parameters I took into account were the Gain Bandwidth Product as well as Slew Rate:

Gain/BW Product = 500 kHz, so it should be able to amplify the 125 kHz Signal by a factor of 4. In the impedance converter setup, the gain is 1 so this shouldn't be the problem.
Slew Rate = 0.2 V/us, the 125 kHz sine wave has a rise time of \$\frac{1}{4} * \frac{1}{125 kHz} = 2 us\$. So the Opamp should be able to change the Voltage by 400 mV in that time.

Is there something I'm missing with this particular opamp or is my approach just wrong in the first place?

I'd appreciate any help.


texts: Dark current versus temperature in phototransistors

texts: Typically dark current rises quite rapidly with respect to temperature. If I have two of the same type of phototransistor, how well is the rise in dark current matched between them?


texts:
I am making a PCB using ULTIBOARD from NI.

The problem is that I use a part called INA321 and for some reason I get the error that my vias are too close to each other when I place vias in the pads for the INA321.

I tried making the vias smaller, but I still get the error.

Is it a bug in the ULTIBOARD program?

I tried to check the options of the PCB printing factory  and fount this:

However, when I changed the via hole size to 0.2mm and via diamter to 0.45 mm I get still this error:

The only other option I have left is to ignore thrse errors.


texts:
I am designing a power supply for WiFi module. I have a regulated power supply which has rating of 17V@800mA which is for some other purpose. The WiFi Module requires 3.3V and draws maximum of 500mA current.

So to achieve the 3.3V volts there are two ways to do so

To use LDO regulator which drops from 17V to 3.3V. But this is the most inefficient way to do, as it will loss much power and energy and much heat will be generated.
To use Switching regulator/DC-DC Buck converter. The inexpensive modules available can do this job which much higher efficiency with very less loss of power but they will generate ripple at their output.

So, I am thinking of using Buck converter with LDO. I will drop the voltage to somewhere near around 4.3V and LDO will be added to drop further with clean output and very less ripple.

So, is it the right way to do this? Also, where LDO should be soldered?near to the controller? or it can some inches away and connected with wires for power supply?

Also the Buck converters have different frequency range, so which frequency regulator is sufficient for my need? I am considering MP1584 Module which has max. switching frequency of 1.5Mhz


texts:
i'm in need to reduce the 9 to 12V from my power supply to 6.3V, for a current consumption of 300mA. Here's the requirements:

Cant be a switching solution (so Buck converters are not an option)
Doesn't have to be a very clean 6.3v, as long as it stays within 5% tolerance
Can't evacuate a lot of heat (small closed enclosure). (my first idea was the usual LM317, but it does dissipate a LOT of heat with this requirements)

I know it's not an easy solution (considering i eliminated the 2 most logical options) and eventually i'll have to compromise (i'll probably end up using the LM317 and hope i don't cook everything).
Any ideas would be apreciated
(oh, i already thought of 7 nasty diodes in series, i was really hoping it didn't came to that)

(for those who didn't already guess what could use 6.3V/300mA, it's a vacuum tube heater)

any ideas would be welcome


texts: Understanding op-amp common mode voltage range when Vin+ is not equal Vin-

texts:
I am using MCP662 op-amp as differential amplifier:

First inputs' signal can vary from 0V to 3V and the second input signal can vary from 1V to 1.4V. MCP662 has common mode voltage range equal 1.7V (Vdd-1.3V). In this circuit Vin+ can exceed 1.7V (for example it is 2V when one input signal is 3V and another is 0). However, common mode voltage (Vin+  + Vin-)/2 will never exceed 1.7V.

Is the Vcm range be violated in this circuit?
Can this circuit to be used when both input signals can vary between 0V and 3V?


texts: What is the practical difference in this DC offset remover?

texts:
I am working on audio signal oscillators. My oscillator generates 0V to +5V triangle wave.
Then I'm removing DC bias to get -5V to +5V signal.
I have found two examples on how to do this:

What is the practical difference between these two approaches? I get roughly the same result in both of them. So I am wondering what method should I use?


texts: Driving a voltage boost circuit with a piezo driver circuit

texts:
For a university project, I'm creating my own small speaker. This speaker includes a speaker driver circuit consisting of a transistor and 3 resistors (see figure below).

simulate this circuit – Schematic created using CircuitLab
 The power source is limited to 1.5V, but I would like to boost this voltage using a voltage boost circuit.

The voltage boost circuit actually is an oscillating circuit including an inductor, diode, switch (oscillating) and a capacitor (see figure below). I think the "timed switch" can be attached to the "feedback" pin from the piezo.

simulate this circuit

Since the piezo driver circuit is a kind of oscillating circuit, I thought it would be nice to combine both circuits. So the piezo driver circuit would be used as the oscillating circuit of the voltage boost circuit.

Both circuits work separately, but not combined. When replacing the light bulb with the piezo, the piezo doesn't vibrate since the capacitor keeps the voltage constant, but the piezo needs to be turned on and off very quickly in order to vibrate.

Somehow, the capacitor needs to power the piezo driver circuit again, but I cannot yet figure out how. Below is my attempt.

simulate this circuit

Can any of you maybe guide me in the right direction?

I hope you understand what I'm trying to do. Otherwise I'll be happy to try to explain it in a different way.


texts: spice plot resolution - sinusoid does not look continuous

texts:
Problem

How does one increase the resolution of a SPICE plot? My sinusoidal signal doesn't look continuous, it looks very 'pointy'.  I am using MACSPICE3 to simulate a non-inverting op-amp by using a dependent source (VCVS).  Changing the step parameter of the tran command has not helped.

I understand that results data is stored in a construct called a plot, which is comprised of vectors.  Is this pointy phenomena linked to the data in these constructs, or the graphical representation?

Example of a pointy plot

Netlist

  Basic Non-Inverting OpAmp

  V1 2 0 AC sin(0 10 50 0 0) DC 0

  RBogus 2 0 10K

  e 3 0 2 1 999K

  R1 3 1 10K

  R2 1 0 10K

  .control

  delete all

  tran 1.0ns 100ms

  plot v(1) v(2) v(3)

  op

  display

  print all

  show all

  .endc

  .end

Note:

RBogus exists to create a closed loop for the ac source.


texts: How to create a circuit drawing that allows easy mapping for setting up a breadboard

texts:
I've read the post Rules and guidelines for drawing good schematics and whilst it does contain a lot of useful information, it doesn't address my question about a drawing to be use for breadboards.

As I progress through learning EE (with help from the Arduino), I’m finding that creating circuit diagrams is becoming a little awkward, and I’m not sure what is the ‘right’ way of doing this to make it better/clearer.

I create circuit diagrams, then load up breadboards using the diagram as a guide, so a messy diagram is really unhelpful. (I am not planning on creating circuit boards at all at the moment. This is just a hobbyist/learning process, as I play with different circuits, components etc)

Basically, I’m coming up with instances where multiple ICs are creating a LOT of cross over wires making it incredibly difficult to trace things through or easily see what connects to what.

A simple example is trying to link up an 8x8 LED Array (1088BS) to a MAX7219 Led Driver chip. The Pin I/O of each device is not helpful, and just looks like spaghetti on my drawing when I connect everything together.

I’ve currently switched to drawing each IC multiple times, so I can see the I/O in the correct order from each side. In the following drawing, the top half and bottom half of the page each only detail 2 ICs each, although 6 are drawn. (this was drawn using Visio until I learnt the right way to do it in an EE design application)

If I drew this diagram, with the ICs side by side, and the pins in the correct place, as it would be on the breadboard, it would just be an unusable mess.

What is the ‘correct’ way of drawing this kind of design?
And would the ‘correct’ way be more beneficial to me as a guide to laying out breadboards? (and later on vero-boards)

The more I think of it, the more I'm thinking that it may not be possible to achieve, and I should change my approach to the problem rather than creating yet another drawing.


texts: How can I increase the load capacity of this circuit?

texts:
I'm not into the current source subject much, but the following circuit provides constant current to the load up to around 500 Ohm:

Here below is the plot of Rload versus Iload:

How can this circuit be modified to obtain the constant current source upto 20k?

Edit:

After reading the answers I changed the circuit to the following one:


texts: How do I select the subclasses of X and Y safety capacitors?

texts:
While designing a switch-mode power supply, I've been reading a lot about X and Y rated safety capacitor. Although I fully understand their use and limitations, how do I determine if I need a X1 or X2 capacitor across the line and a Y1 or Y2 between line and ground?

I understand that slapping a X1/Y1 everywhere would be easy, but I can't seem to find the standard associated with the appropriate sub-class selection. For cost sensitive products, a X2/Y2 could make a difference. How do I determine if the intended application is within the sub-class' limits?

So far, the only specification I found is the IEC 60384, which specify how these capacitors should be tested, but nothing regarding the appropriate safety rating for a known application.


texts:
I would like to ask a question related with induction motor

Whenever I switch ON & OFF a motor, a small voltage (3-8 V) produced at the metal surface  where the motor is attached. I figure out this small voltage by using an oscilloscope. The voltage lasts in millisecond.

I wonder if this small voltage produced when switching ON & OFF the induction motor by using any protective device or component can be eliminated.

The circuit contain only push button, switch button (to change motor direction) capacitor and the induction motor itself

Anyway this is the motor I'm using right now:

Thank you for the response


texts: Bluetooth Low Energy - Smart vs Smart Ready device

texts:
After going through this wiki on BLE, I understood that BLE SmartReady devices are dual mode devices (BT as well as BLE) whereas Smart devices are single mode devices (only BLE).

Few of my friends say that SmartReady device is a Master whereas Smart device is just a slave. Other say that, 'Though the role of master/slave can be switched at any point of time, all slaves share the master's clock.'

Could you please clarify which is true?


texts:
So, in the NAND gate below, I understand how it works with the p-type and n-type transistors. However, my question is what happens with the current when the output is connected to Vdd? If the voltage is high, doesn't that mean current will flow into the output?

Furthermore, if the output is read as high (Vdd), and voltage is supposed to be relative with respect to ground, where is the ground in this circuit when the output is a 1? If the output voltage is Vdd, how does it get read as a high voltage if the output does not have a reference that it can call ground?


texts: Generate a reset signal from a falling edge trigger

texts:
I'm working on a microcontroller design where the mcu is placed in hibernation mode, and can only be awoken by a pulse(high-low-high) signal on the reset pin. (active low)
As a wake-up source i'm using an accelerometer or an external RTC.

The idea is to have the accelerometer trigger an interrupt, that drives an interrupt pin low. The same goes for the RTC. It will pull an interrupt pin to logic low signal. However, this won't wake the mcu from hibernation mode. I need to use this sleep-mode to save as much power as possible.

I'm wondering how I can create a toggle signal from the interrupt-pin signal form the wakeup sources. The toggle must only happen once, since its the reset-pin of the mcu. Is there any kind of latches of logic circuits/components that create this kind of signal?

Edit: Pulse of (High-low-high) signal, not toggle(low-high-low)
I'm using an Energy Micro Gecko (EMF32G890F128) with a Cortex-M3 core.

My energy budget is low, my design should stay as low as <100µA active, and currently with RTC and accelerometer this is achieved.

Edit2: The interrupt signals from both accelerometer and RTC stays low until reset by mcu. Usually this is done by reading a register in the peripheral unit. And for this to happen the mcu must be awake.


texts: Why does my DC power supply fluctuate and say 0A? And why won't my motor spin?

texts:
I'm trying to power this unipolar stepper motor (wire color: black, brown, red, orange, yellow in that order):

using this motor driver breakout board:

Here are some pictures of the setup:

And a wiring diagram:

Just for reference, the lights saying CV and OUT are turned on:

Please tell me if there's anything else I can include to be helpful.

Some people have asked for a schematic, but I have no idea how to make one of those in the built-in tool, especially one that includes the chip I'm using. Sorry if it leaves a hole in the information I'm providing.

I wired everything exactly as indicated on the website for the motor driver breakout board, except using Raspberry Pi instead of Arduino. When I turned on my power supply (KORAD KA3005D), it showed a big fat 0 in the current (recent development: the ampage will drive up to .3-.4 A for several seconds but stays at 0 70% of the time). I don't understand why this fluctuation. Could this be a problem with the power supply itself? The chip? My soldering on the chip? My cables? Any help is greatly appreciated.

Related problem I'm hoping someone can help me figure out why the motor itself won't spin. When I manage to activate my code when there's a current, the motor vibrates and gets hot but doesn't spin.


texts:
Now this is confusing.
At some point i read that higher watts does not neccesarily signify high volume sound. An amp rated at 100w and other rated at 50w dows not mean the former is 2 times louder. Only slightly loud by 3dB which is nothing. To make the latter twice as loud, i should pump the wattage 10x.

Now there is also one thing to consider. SPL.
If i connect a lower SPL speaker to 100w amp and a higher SPL speaker to the 50w amp, the 50w amp will be actually louder than 100w.

Now you tell me, if I am designing an amp, what Wattage amp am i supposed to make. All the time i was looking looking for a 200w ic. After all this literature i went thru, I can also do with a 15w ic and connect a high SPL rating speaker to it. That will suffice?

What does the amp Watt actually tell me?
When am i suppose to use a higher or lower watt amp?
What does it mean to the battery, and speaker?
And ultimately to the listener?

And talking about speakers, i also read somewhere a high end speaker has more impedance than a low end one. Most of the ic datasheet lists for a low impedance ones' - 4ohm. All the while i thought the amp was powerful enuf to drive such speakers? So for high impedance it wont be useful?


texts:
I'm pretty new to electronics and came across a fact I don't quite understand. If you have the below circuit, there are 2 situations:

The switch is not pressed: Lamp 1,2,3 and 4 will glow.
The switch is pressed: Only Lamp 1 and 2 glow.

I can't understand why in the second scenario only lamp 1 and 2 are glowing.
It seems like the current choses the "shortest path", but why won't it then in scenario 1 ignore lamp 4 and just flow through lamp3?

simulate this circuit – Schematic created using CircuitLab


texts: Thermistor resistance to celsius conversion

texts:
I'm new to electronics, and experimenting with a thermistor plugged into an Arduino. It is a 4.7k thermistor (full specs) and I'm using it in conjunction with a 10k resistor (product page).

When rigged up to the Arduino (and powered via a 3.3V pin) it returns an analog reading of around 2870 at room temperature.

I've looked at a few different conversion scripts out there, but most seem to be working when the analog reading is ~600-700. Have I done something wrong? If not, how do I go about working out how to do the conversion?


texts: Which filter should I use? Just want to keep high count values

texts:
I am asking this question because I am not quite sure which filter I should be using.

Mine is simply a signal made up of discrete values as such s = [1 2 2 2 3 4 2 4 3 4 5 3 2 3 3]. Then I would like, per window size, a filtered signal. So e.g. if I use a window size of 5 for s then I would get; s_filtered = [2 2 2 2 2 4 4 4 4 4 3 3 3 3 3]. Hence, I want to keep the values that statistically occur most often per window size.

Currently I am using just a median filter, but I do no think this is the correct approach.

Here is some python code to demonstrate what I am doing (but as said, which I think is wrong).

import numpy as np
import pylab *
from scipy.signal import medfilt

test = np.random.randint(10, size=1000)

fig, ax1 = plt.subplots(1,sharey=True, sharex=True, figsize=(15,5))
ax1.plot(test)
ax1.plot(medfilt(test,[99]),'r')
plt.show()

Where the red line is the filtered signal for a window size of 99.


texts:
first off I have already found a wealth of information here so thank you! I am hoping to get some general feedback on a project I'd like to work on. Here is an outline.

I'd like to be able to transmit 8 channels of 24 bit 48KHz audio over ethernet to a collection of 6 to 8 receivers all connected through a switch. Here is my thought process.

Network Speed - 8 channels * 24 bits = 24 bytes. That is below the minimum of 46 bytes (non 802.1Q) so we'll just work with that minimum. Our minimum frame size then is 84 bytes. At 48KHz this would imply an average throughput of ~32.3 mbit/s on the network. Given this result a fast ethernet network with appropriate switches would seem to be OK. Does this analysis seem accurate?

Note that I'm not too too concerned with perfect playback so an occasionally dropped packet isn't a big deal. Given this I don't think I want to get into sample rate conversion for the network transmission.

Sidenote - originally I wanted to work on a 10Base-T network because a lot of MCUs had integrated 10Base-T MAC/PHY. Given the minimum 84 byte frame size though... this would restrict sample rates to a little less than 15KHz yuck!

Just to be sure I'm thinking about this correctly, I cannot violate the 84 byte frame minimum if I want to be able to use commercial switches correct?
Receiver Hardware

a. Ethernet Controller - I'd like a 100Base-T ethernet controller with built in MAC/PHY. The problem though is, it needs to be able to communicate with the MCU fast enough to push all the audio data through. 8 channels * 24 bits * 48KHz = 9.22 mbit/s. I'm thinking this is going to be too fast for SPI. The ENC424J600, in addition to SPI, has a parallel interface which seems to be useful for faster speeds. Page 53, gives some theoretical performance figures.

http://ww1.microchip.com/downloads/en/DeviceDoc/39935c.pdf

b. MCU - Which ever one I choose will need to be beefy enough to read in all 8 channels of audio data from the Ethernet controller, do some very basic DSP on then (channel mixing), and send out the data to a stereo 24 bit DAC at 48KHz. In addition to this it also needs to do some basic interfacing with panel I/O. Any suggestions on a suitable MCU?

Note that I'm looking at using this DAC.

http://www.cirrus.com/en/products/cs4341.html

Any comments or thoughts you guys have that might be useful to this project would be very much appreciated!

Thanks,
Jordan


texts:
I'm trying to find a 940nm SMD infrared led with minimal red glow at night.
The TSAL6400 gets close to it, but it's still not completely invisible and not SMD.

I've noticed IR leds have different wavelength curves in the lower range. TSAL6400 through hole with blue lens vs  VSMY2943G SMD with clear lens.

I've tried covering them up with an infrared transmitting acrylic sheet but it's completely transparent to the red glow.

My guess it that the radiance on the lower end of the spectrum goes to close to the RED range. Although it's still infrared, the eye is still slightly sensitive to it.

How do I eliminate the red glow visible to the human eye from an IR led?

VSMY2943G


texts:
I'm quite into DIY projects and I am looking at making an electrical unit out of a Raspberry PI and a computer monitor.

I was wondering if someone could provide me any information on what I should do to comply with the safety standards, for example when I integrate the Raspberry PI to use the monitors supply of 240v.

How should I correctly insulate the live feed with this unit, and would by modifying the standard configuration (how the monitor came) make it unable to be PAT tested again?

This may seem a little vague, but like I said it's just a hobby.


texts: Why is the saturation velocity for holes and electrons comparable?

texts: In a semiconductor like GaAs, the saturation velocity for both holes and electrons is on the order of \$10^7\$ cm/s. However, under lower electric fields E, the drift velocity of electrons is much larger than that of holes, since \$v_d = \mu E\$, where the mobility \$\mu\$ of electrons is much greater than holes. Why then are the saturation velocities comparable?


texts: Is an exhausted PSU safe to use for an FPGA?

texts:
For a project I will have 4 stepper motors,a laser module and few modules attached to the FPGA.
I need around 10 amps.

Clearly the FPGA can't provide enough power for all the modules.
I think to use and old 300W PSU to provide power to all the modules.

From 2 connectors I can get multiple 5V sources and connect them to different modules rather than just using an usb cable connected to the FPGA.

Can the PSU sustain all the modules?The amount of power needed is maybe a third of the power of what it could provide.
The PSU being old I'm afraid that can just die randomly or make a short circuit and kill the FPGA.
Is it worth it or should I try another ways to provide power to the elements?


texts: Why is the calibration signal's amplitude of my oscilloscope 10 times higher than stated?

texts:
I'm trying to calibrate my HAMEG HM507 oscilloscope.

The manual says that the calibration signal is 0.2Vpp. With the attentuation of the probe set to x10, volts/division set to 5mV/cm, time/division set to 0.2ms/cm, I should see a square wave with a 4cm amplitude.

But that's not the case. I have to set volts/div. to 50mV in order to see the waveform correctly, because the amplitude is actually 10 times bigger! And indeed, when reading the calibration signal with attentuation set to X1, the scope shows a square wave with an amplitude of 2 volts.

But both the manual and the label on the scope say that the amplitude of the signal is 0.2Vpp. And in the settings I can only set the frequency of the test signal.

Is this an error in the manual? Is there some unknown zoom function that stretches the y-axis? (That can't be, because the x-magnification also adjusts the time/div. indicator). Maybe it's a function that multiplies the signal by 10 to adjust to the attentuation?


texts: IAP bootloader not jumping to the application address

texts:
I am working on IAP in STM32F4. I received .bin file using uart and flash it in 0x08004000 address successfully and disable irq , set msp , set vector, deinit hal , reset the systick registers but the jump is not working, It just freezes there. Can anyone help me with this?
define APP_ADDRESS 0x08004000


texts: How to drive a high-side N-channel MOSFET with low VGS?

texts:
Question first:

Is there a bootstrap driver that is available in DIP, works similar to the IRS2001, but is OK with a VCC of 4-5V?
I'm also a bit limited in the amount of space I have -- is there a very small circuit that can do the bootstrapping for me with what I have available? Specifically, the switcharoo between charging the bootstrap capacitor, and then feeding it into the gate of the N-channel, is something I can't quite figure out how to do discretely.

Background:

I have a system with 5V logic switching a 5A motor at 1 kHz PWM frequency with a 6.4V-8.4V voltage. I'm building this myself, and am not set up to do surface mount circuits -- and most commercial H-bridge drivers for 5A want external switches anyway.

I built a H-bridge with power MOSFETS, P-channel high side, and N-channel low side, and using the 5V logic to switch the N-channel, and use a 70 Ohm pull-up and small signal N-channel to pull down the gate of the P-channel. At this PWM rate, that's good enough (220 Ohm pull-up was not -- the PWM blew the P-channel devices.) However, the loss of the 70 Ohm pull-up when pulling the gate down is significant.

I now want to use both high-side and low-side N-channels. I got some IRS2001pbf hi/low side drivers, which seemed like they would do the job -- except they have a "undervoltage lockout" feature that wants VCC to be at least 9V. This is to protect N-channel devices that want 10 V VGS -- but I'm using a IRLB8721pbf device with a 4.5V VGS RDSon of 18 milliohms, so I don't need that. I just need to bootstrap above the drive voltage of the motor by 4.5V to 5V.


texts: What kinds of things can cause a power supply to cut out?

texts:
We've been using an HBB5-3-OV-A+G power supply in our rack mount products. One output powers a small fan, and the other powers our product which is an assortment of digital and rf boards and an LCD. It's a 3 amp supply, and our boards and display draw about 1 amp total.

Recently we've been having a problem. Occasionally the output that powers our boards cuts out. When we disconnect and reconnect the AC line it comes back on. The side that powers the fan stays on.

This sometimes happens even when the rack chassis cover is off, and the unit hasn't been on for long, so it doesn't seem like a thermal protection thing.  Some units never do this, some do it several times a day.

The 1 amp current measurement is based on the readout of a bench supply, so it wouldn't indicate any short current spikes. I'll have to find some way to monitor the current on a scope.  I can't think of any reason why it would spike, though. There are some relays in the device, but they stay in the same position except when the user enters a command, and it doesn't cut out when they are switched.

So, is there anything nonobvious that can trip a supply's overcurrent or thermal protection?


texts: Rotor speed of separately ecxited DC motor with terminal voltage and field current

texts: How does rotor speed vary with terminal voltage and field current of a separately excited DC motor? Is it different for a no load condition vs other loading condition?


texts:
I want to use the
TCA9548A  in QFN format, I have diffuclties understanding the direction of pins, is it here really in clockwise  ? as shown in page 33 of the datasheet ?


texts:
I want to do something like the first of the gadgets in this video:

https://www.youtube.com/watch?v=aEo_nJ3iUYI (0:07 - 1:00)

It's a flashlight connected to the micro USB port in my cell phone, but I do not know if this is safe.

In case it can be build without problems, I've been looking for some information, and I have some doubts:

A micro USB connector has 5 pin (VCC, D-, D+, ID, GND), to which one of these should I connect the resistor and the LED anode?
So it can be used with any phone, what resistor should I use?


texts: How can I use an analog switch to control a higher voltage than vcc?

texts:
I am using an Arduino and several analog switches (TEXAS INSTRUMENTS CD74HC4066E) to control several items (LEDs and other devices.)  The switching voltage that comes out of the Arduino is 5v, but several of the voltages that I need to switch are higher (typically 9 volts for LED strips.)

Will these analog switches be able to control 9 volts if 5 volts is used to switch it?

Should VCC be 5 volts or 9 volts?

is 12 volts and option?


texts: When should bare die be used instead of QFN/BGA packages?

texts:
I have no experience with bare die as a package, and I have been recently tasked with deciding between bare die, BGA, or QFN package for a SoC.
Searching the internet, I have not really found much information on the advantages and disadvantages of using a bare die.
What are the pros/cons of using bare die over more typical packages like BGA or QFN?
Thanks in advance!


texts: I understand that when you put Resistors in parallel the resistance decreases, my question is why does this actually happen? What causes the Resistance to decrease? When Resistors are in serial, their Resistances are added, why when we put them in parallel do the Resistors resist less current? I don't understand how that's possible?


texts: The potential difference between primary and secondary wiring of an isolating transformer

texts: Lets say we have an isolation transformer powering our circuit. What voltage is a multimeter going to show when we put one probe into mains ground, and the other one at the output of the isolated (secondary) transformer wiring.


texts:
Can an NTC (Negative Temperature Coefficient) thermistor be placed before a MOV (Metal Oxide Varistor) for protecting an SMPS from inrush current and voltage spikes?

Here is a drawing to clarify my question:


texts: The current needed for the RS-485 tranceiver?

texts:
The current consumption for the RS-485 IC is about 10 to 20 mA.
However, if the two ends are shorted, the transciever can draw excessive current.
So, I am trying to put PPTC device on it's VDD line to prevent it's excessive current from affecting the whole product.

The question is, what is the appropriate value for the current limiting?

Do i simply get the value by 5V divided by the termination resistor they use?

If so, what is the smallest termination resistor they will use? 75 Ohms?


texts: Replacing a transistor when I can't find any info on it

texts:
I am attempting to repair a Sonix Ultrasonic Cleaner and I have found that the only parts that have gone bad are two power transistors, SIV300004.  I emailed Sonix and they want to sell me the whole control board not just the part.  And they didn't want to give me any more info like schematics or a data sheet.

I would need two control boards and they would cost more than this thing is worth.  I have searched Google four a few hours and can only find a few references from others from years ago who are looking for the same part.  I can't even figure out who makes this SIV300004, If I could I would contact the manufacture.

So I was thinking that maybe there is some way to figure it out from the circuit.  Can that be done?  If I were to draw out the schematics would I be able to figure out what specs I would need for a replacement transistor?  How would I go about this. Or is there any other way to figure out what I can use?

Thanks for the help,
Russ


texts:
The output voltage from the NPN transistor (TIP142) is 4.7 volts with no load attached and only decreases as the load increases. However, voltage at its base (from an LM7805) remains a stable 5V. How do I make the output voltage stable 5V as well?
Any help will be greatly appreciated.


texts:
I am using a CPC1965G AC SSR connected to a ceramic disc capacitor (Z5U103M 1kV) and 63 ohm resistor to power up 2 fan (the fans I am using use 110V).

It works fine but then the LED inside the SSR IC blows up. Do I need to change the resistor/capacitor in order to lower current going thru the IC?


texts: Using boolean algebra, simplify $$y = \bar{s} \cdot \bar{u} + s \cdot \bar{u}+s \cdot u$$

texts:
I have the following function, that I want to minimise using boolean algebra:
$$y = \bar{s} \cdot \bar{u} + s \cdot \bar{u}+s \cdot u$$
Here's my attempt:
$$\bar{s} \cdot \bar{u} + s \cdot \bar{u}+s \cdot u = \bar{u} \cdot (\bar{s} +s)+s \cdot u = \bar{u} \cdot 1+s \cdot u=\bar{u} + s \cdot u = \bar{u} +s$$
In the last step I used the absorption property but I was wondering if there is another way to solve:
$$\bar{u} + s \cdot u$$


texts: Can someone help me to identify these two similar SMD components? My guess it could be SMD fuses, 0805 package. But I'm not a hundred percent sure.


texts: I am sorry to ask this because there are so many of these topics on the board but I can not seem to find a solution. I am fairly new to electronics in this regard, but in school Lab we were hooking up a 9v power supply to the MC7805CT to output 5v for a hex inverter. It was working then but when I came home I bought a 9v regulated power supply with 300mA and it would only output 1v and get pretty hot while doing it. I am not completely sure what the one we were using in Lab was beyond it was 9v as well. In lab the source was outputting around 9v, however mine is more like 10v. Any help would be greatly appreciated.


texts:
I am trying to design an AC/DC power supply for an LED aquarium light. My plan is to create a switching power supply which will first rectify the AC to a DC voltage before using switching to step the voltage down using a higher frequency transformer.

For the design of the transformer I have been mainly relying on three books.

Pulse Width Modulated Power Supplies by Valter Quercioli
Switching Power Supply Design and Optimization Sanjaya Maniktala
Switching Power Supply Design Abraham Pressman

In the future I might be interested in trying to sell this power supply as part of a product, so I am interested in ensuring that it operates safely.

At the moment my concern is should my power supply be designed to handle surges in the mains line due to lightning strikes? In all three of the books listed above no attention is given to this topic. I know that it is important to address inrush current to the capacitor, but I do not think any of these techniques would prevent current in the event of a lightning strike.

Based on the lack of information in these books and some information from other stack exchange threads Creating an isolated power supply to prevent effects of lightning I am under the impression that surges from lightning strikes is just something these electronics are not designed for. The main goal of this post is to first confirm that my impression is correct. Secondly I wanted to see if there are any best practices to handle surges from lightning strikes for indoor AC to DC power supplies.

Thank You


texts: Why do Arduinos ship w/ 16MHz crystal instead of 20MHz?

texts:
Why do Arduino boards ship w/ 16MHz crystal instead of 20MHz? They are spec'ed for operating at 20MHz, after all.

I guess there are a few advantages to running more slowly (lower power consumption, longer life), but I must be missing something.


texts:
Let's consider a coaxial cable which supplies a dipole antenna. My reference for all my statements is here.

My reference says:

Note that the current along a transmission line should be of equal magnitude on the inner and outer conductors, as is typically the case. Observe what happens when the coax is connected to the dipole. The current on the center conductor (the red/pink center core of the coax, labeled IA) has no where else to go, so must flow along the dipole arm that is connected to it. However, the current that travels along the inner side of the outer conductor (IB) has two options: it can travel down the dipole antenna, or down the reverse (outer) side of the outer conductor of the coaxial cable (labeled IC in Figure 1).

Well, I don't understand why the current in the outer conductor should be divided in IB ("direct") and IC ("Reverse"). I see it in this way: the coaxial cable is supplied by a voltage or current source, with its terminals connected one to the shield and one to the inner conductor. The current in the inner conductor is equal to the total current in the shield. The last one, because of skin effect, flows mainly on the shield surface, so it goes partially in the inner side and partially in the outer side of the shield. Both current have the same direction, as the current that flows any conductor surface at RF.
I'd say that IA is equal to the total current flowing in the shield surface. And a dipole with arms connected to the whole shield conductor and to the inner conductor will receive equal currents. Which is the mistake in my analysis?

As I see, the unbalanced nature of the coaxial cable is due to its shield having both an inner and an outer surface. So, it's a parasitic effect of the coaxial cable, and I'd say that it's absent for instance in simple 2-wires transmission line. Is it correct?

Again, the problem is the parasitic current IC in a coaxial cable. Well, what does it has to do with this usual representation of a balun as a converter from a grounded signal to a floating signal?

Even in a 2-wires transmission line, which I'd say it's balanced, we consider one conductor as GND, like in the following picture (indicated as "0").


texts: Control Output Shock From Cockroft-Walton Doubler

texts:
so I'm building a device that charges a capacitor bank to between 1kV and 2kV. The goal here is to use a 555 timer to control a shock pulse from the capacitor bank. I can touch the ouputs of the bank, and I get an initial shock, but if I hold my finger on the outputs, the shock is much less because the capacitors can't charge up if something is shorting the outputs. I'd like to be able to allow the bank to charge up, and then selectively discharge the bank with a timer. I'm basically looking for the functionality you'd get from a spark gap, but I want to be able to control the shock pulse with a timer. I was thinking of using a timer to switch a transistor or mosfet, but the voltage is too high and I'm having a difficult time finding one with a high enough breakdown voltage.

Is there any other way I can selectively control the output shock?


texts: How to select capacitor for my rectifier circuit

texts: I had designed a rectifier circuit, in that I don't know how to choose capacitor. for example if I'm get in input supply as 9 V, now I want change it for 10 V, then how should I choose capacitor.


texts: How to choose DC resistance parameter of a USB 2.0 common mode choke?

texts:
How do i know whether i have to choose a bigger sized common mode choke with lower DC resistance for USB 2.0 D+/D- lines or using a smaller one with higher DC resistance is also just ok?
In fact there are several USB 2.0 common mode chokes (Common mode impedance: 90Ohm @ 100MHz) on the market with different DC resistances roughly ranging from 100mOhm up to 5Ohm.
Any clarification on how to choose an adequate (or low enough) DC resistance would be appreciated.


texts: simplest way to create an activatable alarm on a speaker?

texts:
I have made a circuit that produces a 3.3V high when its active and 0V when it is off.

Now I would like to extend it with a speaker that plays some sort of alarm (although it shouldn't be too intrusive, but clearly understandable) that I wan't to activate with said circuit. So it plays some sort of tune or alarm for as long as the signal is high.

So what would be a simple way to create a triggerable alarm/tune without the need for a computer?

Ideal would be some sort of chip with preprogrammed music or something on it that I could just hook up to a speaker and that could simply connect to the output of the circuit.

I have looked for something like that but it doesn't seam to exist, they always require a computer or a raspberry pi to set the samples.

And just connecting a speaker to the signal outright just creates an irritating tone.


texts:
Given a signal wire [7:0] dummy, how can I concatenate it n times?

That is, is there a notation for the following:

{dummy, ..., dummy} // n times

?


texts: Voltage level difference when using an external power supply

texts:
I'm making up an interface board for an old computer system (an Oric Atmos), but I have pretty basic electronic experience.

Version 1 of my board works fine.  It converts the Oric's rather curious CMOS RGB output to a SCART compatible output, powered from the machine's expansion port.

Version 2 runs from an external 5v supply which then runs through a DC-DC Booster to supply the Oric, replacing it's original PSU.  In this configuration the machine fails to boot once the board is connected to the RGB socket of the Oric.

I've managed to trace the problem, but I don't know how to fix it.  The Oric uses an LM7905 internally rather than a LM7805.  As a result, rather than pulling Vcc down, it pulls the earth up.  On my circuit, the signal ground from the RGB port is then made common with the supply earth and everything stops working.  The Oric is basically running at +7.5/+2.5v in relation to my SCART converter.  This wasn't a problem previously because it was powered directly from the Oric's expansion port.

How can I hook up the RGB output to the SCART converter when their earths are on different levels?  I assume that I need to somehow use the input RGB signals in reference to their signal ground, but not common that ground with the rest of the converters circuitry.  I've probably missed something pretty basic as this has to be a common occurrence.


texts:
Suppose I have a FIFO code written in vhdl for FIFO. I want to delete an element from the FIFO. Here would the FIFO be acting the same as a linked list where I check each and every element of the FIFO and then match it with the data_in and then finally delete it.

OR it is the case that I should always delete the first element of the FIFO ?

Please give me some valuable suggestions .

Regards to all.


texts: AC rms value of pulse train vs RMS value

texts:
I have a pulse train with Duty Cycle = 1/4, that oscillates from 0V to 3V.
I found the RMS value to be

$$ RMS = V \sqrt{D} = 3 \times 1/2 = 1.5 V $$

The DC offset, since it's oscillating from 0V to 3V, is 1.5 V.

What is the AC RMS value? When I use the formula: \$RMS^2 = DC^2+AC_{rms}^2\$ and substitute for RMS and DC, I get \$AC_{rms}= 0V\$

What am I missing?

Am I doing the DC offset wrong? Should the DC offset really be the average value, so its \$V \times D = 3 \times 1/4 = 3/4\$?

Then the \$AC_{RMS} = 1.5^2-(3/4)^2 = \sqrt{27/16}\$ ?


texts:
Has anyone utilized 9-pin DB9 connectors for driving and receiving LVDS signals? I wanted to use Micro-D connectors on a board I am developing but they take too long to get. Since DB9 connectors are utilized for RS-422, RS-232 that have a differential 100 Ohm characteristic impedance, I figured it would work with LVDS as well.

I am driving and receiving LVDS signals up to 100 Mbps. Distance 20-40 inches

Thank you


texts: Hold OPAMP Integrator at zero voltage (Guarantee defined slew rate)

texts:
I have the following request:
I want to stop a common integrator (which should generate a defined slew rate for a square wave signal) exactly at zero (0 Volt) due to the return-to-zero coding of the interface.

In reality, the integrator will be supplied with a push-pull stage (+/- 5V), a third transistor would be switched against GND.

I have tried two comparators (LM393), whose output signal would be detected by a digital logic and the logic would then switch the push-pull stage to idle:

The problem: As you can already see in the simulation, there is a bigger phase offset (this is only the result of one comparator covering the positive threshold).

Can anyone think of a simple and fast solution? Maybe just one transistor?


texts:
Below is the control to output transfer function of a boost converter.
(source: Switching Power Supplies A - Z by Sanjaya Maniktala here at page 286)

And this is one part talking about the RHP zero the book. I don't understand the last part from "Eventually...".

When output voltage dips, the controller adjusts to increase duty cycle. However, by increasing duty cycle the time to transfer energy to load decreases. If everything goes on like this, finally the duty cycle will go to 1 and no time for transferring energy to load. But the note below says that eventually the inductor current ramps up to the right level and the strange behavior gets corrected. Why duty cycle not go to 1?

  Note: Intuitively, the RHP zero is often explained as follows — if we suddenly increase the load, the output dips slightly. This causes
  the converter to increase its duty cycle in an effort to restore the
  output. Unfortunately, for both the boost and the buck-boost, energy
  is delivered to the load only during the switch off-time. So, an
  increase in the duty cycle decreases the off-time, and there is now,
  unfortunately, a smaller interval available for the stored inductor
  energy to get transferred to the output. Therefore, the output
  voltage, instead of increasing as we were hoping, dips even further
  for a few cycles. This is the RHP zero in action. Eventually, the
  current in the inductor does manage to ramp up over several successive
  switching cycles to the new level consistent with the increased energy
  demand, and so this strange situation gets corrected — provided full
  instability has not already occurred!


texts: RC car steering circuit: what does it do?

texts:
I have just disassembled a RC car. Attached to the stepper motor that controls the steering of the car was a small circuit board with a cog wheel attached to it. I am trying to figure out what this circuit does. My idea is that it is responsible of keeping track of the wheels position but I am not certain. Here is a picture of it:

As you can see there are 5 wires coming out of it and I know that the green one is GND. Does anyone have an idea of what its function might be?

EDIT:

I connected the green wire(GND) along with all the other wires (one at a time) and measured the resistance for different positions of the cog. This is what I came up with:

The grey areas are the zones where R < 1 Ω, i.e current could flow. The areas marked with OL are areas with a huge resistance, i.e no current could flow. I have tried to grasp these results but failed. To me it does not seem logical, there is no symmetry...


texts:
I am looking for a smart way to regulate my input power Vin = 12-24V to a stable Vout = 12V; Imax = 3A- Usual I use the TI Workbench but this time it makes really complex designs.
On the Load side there are DC Motors and Sensors - The supervisor wants low noise so I thought about using a Linear Regulator but I read that Vin needs to be at least 1-2V higher than Vout and an LDO doesn't work if the input voltage is already at 12V I would need a boost which would make everything even more complex.
There is only 1 Vin and I don't know if the user uses 12 or 24V.
After I regulate it to 12V I would like to use a Buck (TPS56339) for getting it down to 5V and power up an ESP. Further I need to regulate it down to 3V3 to power up some IC's which I would make over a linear from 5V to 3V3 because the current needs to be higher than from the ESP32 3V3 pin.
The only step I am really stuck on is a good way to regulate the first step from 12/24V to 12V. If possible I would like to internally read the voltage level and if it's already on 12V, skip the first regulation. If it's at 24V put it into a linear to get it down to 12V (36W should be doable?).
A good idea how to do that?
Thanks!


texts: Unpowered MAX232 - input 'leaking' into Vcc

texts:
My PC is connected to a MAX232 through a USB-to-serial cable. When everything is powered, there are no issues. However, when I turn off the power, the MAX232's \$V_{cc}\$ has a voltage of -0.5 V (presumably from the -9V input). This scares me because I have several other ICs connected to the same \$V_{cc}\$ rail, and most of them have an absolute minimum supply voltage of -0.3 V in their datasheets.

I'll split this up into several related questions:

What is this effect (\$V_{cc}\$ getting powered through an input) called?
Is there any information on this in the datasheet that I'm missing?
Am I going to damage the rest of my circuit with my current setup?
If I want to fix this issue, should I put a diode/resistor between my 5 V rail and the MAX232's \$V_{cc}\$ pin, or is there a better solution?


texts:
There are "Burn Out" bits in the mode register. I don't see a good description in the datasheet.

How can I use these correctly?  I don't want to spoil the ADC...


texts:
Others have four legs, which makes sense to me, as ground can be shared.

One of many examples of a six legged RGB LED is the Kingbright KAF-5060PBESEEVGC.


texts: Simplifying a circuit with an empty wire (that may or may not be in parallel)

texts:
Determine the value of the resistance R in the circuit shown below, given that Req = 9 ohms.

I called the top-left, top-right and middle-right nodes a, c and b respectively, and did a delta-Y transformation on the 24-ohm, 4-ohm and R resistor. I got that R3 and the 8-ohm resistor are in series, but now I'm completely stuck on trying to figure out how the empty wire in the middle of the circuit gets simplified.

If my understanding of parallel is correct then I think the wire is in parallel with the 30-ohm resistor because both ends connect to each other, so the equivalent resistance would be 0 and I could cancel out the 30-ohm resistor completely. But if that's true, then by the same reasoning wouldn't the wire also ultimately short everything above it including R? And if it's not in parallel with the 30-ohm resistor, how can I simplify anything?


texts: How to read MOSFET datasheet to determine when the MOSFET is fully on

texts:
I'm currently trying to find an N-channel MOSFET to act as a switch to be controlled by my Arduino, and I've come across two particular MOSFETS so far that seem like they would be a good fit to the application I am trying to do.
The first one is this one: https://components101.com/mosfets/irfz44n-datasheet-pinout-features
The second one is this one: https://www.infineon.com/cms/en/product/power/mosfet/12v-300v-n-channel-power-mosfet/irlz44n/.
For the first MOSFET, in that link it says that the MOSFET will turn on starting at 4V and won't fully turn on until it exceeds 10V, so its recommended to use the second MOSFET I've linked. I'm kinda new to this so I was wondering how do I know that the first MOSFET requires 10V to fully turn on? I looked at the datasheet and while I don't understand most of it, I did see the section labelled as Vgs(TH). The min voltage stated is 2V while the max voltage stated is 4V. Does the 2V not mean anything then? Why does the datasheet state 4V is that max Vgs(TH)? Looking at the absolute maximum ratings, it seems that Vgs should get nowhere near 20V, so how do I know that at 10V it will start to be fully on to use as a switch?
In the link to the first MOSFET, it also actually recommends using the second MOSFET I've linked if I want to use a microcontroller to control the transistor. They've come to that conclusion because the second MOSFET can be fully turned on using the 5V from an Arduino.


texts: EAGLE schematic - capacitors and resistors all incorrectly connect to each other in BOARD

texts:
I'm relatively new to EAGLE and after watching tutorials I am trying to design a small board with (eventually) 16 low pass filters.

This is the schematic view, I am trying to make a low pass filter - ground, through capacitor, into the resistor. When I turn this into board view, it looks like the next picture which I believe is incorrect.

This is what the Board view looks like which seems wrong to me as all the capacitors are connected, as are all the resistors. But not to each other.

Any thoughts on what I am doing wrong?


texts: How does the signal change cause a current change in this circuit?

texts:
Consider a Common Source NMOS amplifier with current source as a load.

simulate this circuit – Schematic created using CircuitLab

If the drain current is constant as dictated by the current source, how could Vin change the drain current of the transistor?

EDIT:

If there is a current source load connected to the drain of a CS amplifier, would the current be determined by the current source alone?


texts:
I'm trying to analyse the harmonics present in different household devices's current waveforms. For this, I need a CT based current sensor which can sample data quite accurately and quickly (around 5% error, atleast 50 times an AC cycle).
I have searched in the internet and found the below few :

https://www.amazon.in/Single-Phase-Current-Sensor-Module-Arduino/dp/B01M1KD163?tag=googinhydr18418-21

https://www.amazon.in/xcluma-Sct-013-030-Non-Invasive-Current-Sensor/dp/B072QL2D3F?tag=googinhydr18418-21&tag=googinkenshoo-21&ascsubtag=3d26d24b-f11d-47ad-aa42-7236f8648b08

These seem to do the job of calculating the rms current and provide the data which can be fed to a data converter. But none of them satisfies my need in obtaining a real-time continuous data of the current drawn by the load.
It would be helpful if anyone could point me a better current sensor/system module which can be interfaced with a micro-controller to process the signals.


texts: Measuring power consumption of a load, connected to a terminal block of a relay

texts:
I have a relay board with multiple relays (4) which is connected to an Arduino Uno. Each relay controls a lightbulb (~40-50W).

I'd like to measure the power consumption of the connected lightbulbs on the relay boards using the Arduino and some other component, and was wondering how could I achieve this (what that component should/could be)?

Thank you in advance.


texts: Emitter follower augmented input current

texts:
Hello, I have this emitter follower augmented ( I think that's his name in english)
but I don't know from where is the beta+1 on the Iin ecuation?


texts: using Atmega328p and its ADC to read both negative and positive values

texts:
I am currently working with a Heart Pulse Sensor

I am using a 0-9v supply voltage which is capped at 5v using a voltage regulator 7805. The 5v powers up the ATmega328P as well as the Heart Pulse Sensor. When measuring the signal from my pulse the voltage ranges between 2.5 to 3.5 v approx, however, the signal has a min voltage of approx -1 to 2.5v.
Now since the signal is an analogue signal i am required to use the ADC to convert the values and act upon them. The ATmega328P does not have the differential of negative or positive voltage reference. Therefore, i am forced to do something about it. I was thinking of using a potential divider and a pot to add some DC on to it making a composite signal and letting it rise above zero.

Is it possible to do this using the 5volts supply, or do i need to make this supply voltage from negative to positive... say -9 to 9v?

And what other recommendations can you give to fulfill the requirements regarding the approach?


texts: OrCad issue: Logic circuit simulation....ambiguous output

texts:
After simulating the following logic circuit(in OrCad),the resulting output -'y' is unclear. It seems to me that everything is fine, yet the result is ambiguous.

Can you, please, explain what is the problem here ? Thank you in advance.

  The Circuit:

  The Stimulus Editor:

  The Result of Simulation:


texts: Integrating 12v "ups" to a portable fridge

texts:
I want to make a portable fridge more portable with Li ion batteries and I'm thinking about how to connect all the pieces.
Load is rated for 12V 5A / 24V 2.5A, there is AC/DC SMPS that outputs 13.2v and 12V car socket. I want to use 3s battery pack (higher voltage should be better but then the integrated power supply won't be able to charge the batteries without stepping up the voltage or switching out the power supply for higher voltage). User shouldn't have to do anything for it to switch from AC to battery, and automatically charge the batteries. All preferably using off the shelf things. If the automatic operation is not feasible, what other alternatives there are?
My preliminary circuit:

simulate this circuit – Schematic created using CircuitLab
For charging and 24v conversion I'm thinking about this "300W" DC/DC step down converter with CC/CV. https://www.amazon.com/Aideepen-Constant-Current-Adjustable-Converter/dp/B0747QDRW9


texts: Using BLE module to detect beacons nearby

texts:
I'm trying to design a BLE reader which scans and detects nearby beacons.
However in many tutorials I have seen projects which uses Rasberry Pi and some BLE module it requires complex libraries.

I want to design the reader using a microcontroller like an STM32F0. My doubt is that if i use
beacon modules VG01  from SKYLABS and SKYLAB BLE 4.0 module SKB360 module.

Would the beacons be detectable from the SKB360 module using AT+SCAN_BLE at command in UART mode?
Our application includes locating each beacon using multiple readers installed over a very large yard. We can't use mobile device for that purpose so we are designing a beacon reader.


texts: Calculating discharge time of 12V LED light powered by AA batteries

texts:
I just want to check up my assumption on power consumption of six 12V LED lights in parallel connection. So I powered it by 8 AA (E91 energizer) batteries in series.

The LED's ideal forward current is 80 mA for good lighting.

$$6 \times 80mA = 480mA$$

That's based on the datasheet (milliamp - hour capacity).

Is it correct if I assume it can power the 6 LEDs in parallel for \$\dfrac{1500}{480} = 3.125 hrs\$?

Additional question: Is there any way I can keep the LED brightness at optimal level (not affected by the exhausting batteries)?


texts: How do I reset NE555 output to LOW when powered on?

texts:
Here is a functional NE555 push-on push-off switch. But the problem with this is whenever the power source is connected, it starts in random On or Off position.

How to modify it so that it always remains in OFF position when power is just connected (aka. system is restarted).

For actual values, you can see a YouTube video.


texts:
It says that the energy of the EM wave decays rapidly if it travels through a good conductive material. Therefore, much of the wave is travelling on the surface of the copper wire. (since it decays rapidly if it travels downward and toward (z-direction in the figure) the core of the copper wire).

But this doesn't make sense. Even if the EM wave is travelling on the surface of the copper wire, it is still on the copper medium. This means that it couldn't travel a distance longer than a few "skin-depth" distances even at the surface (x-direction in the figure).

What?


texts:
I live on a boat with a 24V LiFePO4 battery system that has a large capacity and discharge capability, but I don't have a large inverter for using AC gear.
I have a MIG welder, that takes AC and transforms it to direct current electrode positive or DCEP for welding aluminum.
I would like to cut out the mechanism that does the transformation (transformer???) and power it directly from my batteries.

Is that possible?

How do I do it? My gut tells me to look for the biggest wire after the big heavy looking thing "transformer" and connect the positive terminal of the battery to it, and the ground clamp to the negative of the battery and it should just work, but the unit has a display, and wire feed motor and a whole bunch of circuit boards sooooo maybe I'm crazy to just try that.


texts: What types of signals should be considered to have a 50 Ω trace impedance?

texts:
Generally speaking, what time of signals should be designed to have a 50 Ω trace impedance ?

Some datasheets I've read have specifically mentioned 50 Ω but others have not.

Is it good practice to make every trace 50 Ω ? Should it be reserved for high frequency communication lines only ? UART ? USB ? SPI ? etc..?


texts: Difference between LVDS and "Low Power LVDS"

texts:
It sounds like a double emphasis but indeed, pin 25 of the LTC2323 (http://www.linear.com/product/LTC2323-16) I lets me choose between:

CMOS (GND)
LVDS (IOVDD)
Low-Power LVDS (leave floating)

As often, the datasheet does not bother discussing difference at all and neither does my Google search or Wikipedia ersult in enlightenment.

I want to use "LVDS": I connect the digital lines differentially (100 Ohm terminated) to a Spartan-6 FPGA. The IO voltage is 2.5V. Shall I set the pin to LVDS or Low-Power LVDS?


texts:
simulate this circuit – Schematic created using CircuitLab

I am trying to connect my lm358 so that it acts like a buffer.  I am connecting:

VCC to + 5 volts
Ground to Ground
Non-inverting input to +5 volts
Inverting input to output.

According to my research, connecting the output to the inverting input should cause the output to have the same voltage as the input (+5 volts.)  However, I an getting 3.7 volts.  Am I making a mistake here, or is the chip damaged or mislabeled?  Should I be adding a resister or capacitor into this configuration somewhere?

Edit:  I tested this design with +9 volts to the VCC and it was able to produce +5 volts on the output.  Then, when I applied +9 volts to the non-inverting input, the IC produced 8.17 volts on the output.


texts:
I'm designing a 56 bit shift register to store the bits coming in.

In my system, 8 bit data is keep coming in from a generator and I need to output the maximum value detected with 3 bytes either side of it.I want the data stored in a 56 bit wide shift register to give a out put that consists of the maximum and the other 7 bytes as shown in the graph.

The system compare each byte coming in with a temporary maximum value and it will give a 56 bit output each time when a new maximum value is detected.

I just wondering how can I keep the new coming in data at the centre so once the new-coming-in data is found to be greater than the temporary maximum I'm able to out put the whole 56-bit serial signal.

I tried to write something but Modelsim gave me this

  Target type ieee.std_logic_1164.STD_LOGIC_VECTOR in signal assignment is different from expression type ieee.NUMERIC_STD.SIGNED. for   temp_shift_register(31downto 24).....

shift : process (clk)
begin
  if rising_edge(clk) and begin_req ='1' then
    for i in 55 downto 8 loop
      temp_shift_register(i) <= temp_shift_register(i-8);
    end loop;
    temp_shift_register(31 downto 24) <= temp_byte;
  else null;
  end if;
end process;

The signal declarations are:

signal temp_shift_register : std_logic_vector (55 downto 0):= "00000000000000000000000000000000000000000000000000000000";
signal perm_shift_register : std_logic_vector (55 downto 0):= "00000000000000000000000000000000000000000000000000000000";
signal temp_byte : signed (7 downto 0);


texts:
I am using following circuit and crystal is connected to XTAL2 and XTAL1 pin as shown below.

Following IC is LPC2138, shown in image.

I am using ADC chip ( DDC112 ) for A to D conversion. For ADC IC, CLK pin is needed. If I want to use same crystal (Y1 in the image) for ADC, I need to assign this pin to CLK pin of ADC.

Which pin should I connect to CLK pin of ADC, XTAL2 or XTAL1 (if crystal frequncy is same for both chip) ?


texts: What happens to a 32-bit input when a gate will only output 1 bit?

texts:
For example, suppose I have a combinational circuit that takes 32 bits as input and outputs 1 bit that is equal to 1 if the 32-bits are equal to 0, and outputs 0 if the 32 bits are anything else.  How can I achieve this result using NAND, AND, OR, or inverter gates?

In particular, what happens to the 32 bit result when I put it through a gate.  Thus, if I wanted to put the 32 bits in a XOR gate such as:

0       ------------\
                    XOR -----------
32 bits ------------/

And the output of my combinational circuit was only one bit, what would happen here?


texts: AC/Phasor Circuit Output Voltage Question

texts:
So we have a pretty simple circuit, just a 10V voltage source in series with an impedance of 1.8k ohms and a capacitor with a capacitance of 100nF. We're asked to check the voltage across the capacitor at various frequencies.

I was told we use the reactance of the capacitor to find the voltage, which is 1/wC. I do (what i thought was) a simple voltage division across the capacitor, which I thought was just V * Xc/(Xc + R) with Xc being the reactance of the capacitor and R being the impedance of the other element.

The answers I get make sense but the solutions say that I should have used this formula: V * Xc / sqrt(Xc^2 + R^2). the answers I get using either formula are both similar but why would I use that second formula? Where'd they get that from?


texts: Using open termination to intentionally reflect RF signal

texts:
Part of the calibration for an RF system we designed involves measuring the frequency response so that we can equalize the return. Part of this calibration requires measuring the reference response of our test setup so we can remove it during our calculations.

Previously we had a two-antenna setup, with one path for Tx and one for Rx. For our reference collection we then would connect the Tx and Rx cables together, cutting out only our system under test. Now we are trying to move to a single-antenna setup which can both transmit and receive from the same antenna. Below is a basic diagram of our setup. The antenna is transmitting to the system we are calibrating, but that part isn't really relevant here.

simulate this circuit – Schematic created using CircuitLab

In order to remove the test equipment from this setup, we would need to perform a reference measurement of just the circulator and cables. Since an open circuit acts as a reflector, I had the idea to terminate the cable with an open connector from a cal kit, so that the signal is returned while still isolating from the system under test.

Is there anything wrong with intentionally reflecting the RF signal in this way? Everything I've read so far only treats reflections as unwanted in explaining why impedance matching is important. None have looked at how to take advantage of reflections.

We don't need a super-accurate calibration, as part of our SUT includes free-space transmission. I just want to make sure there's not something inherently wrong with trying to use the reflected signal.


texts: How to take resistance reading when value is effected by measurement?

texts:
Context

I am trying to measure the wiper resistance of a potentiometer. This is performed by leaving the potentiometer wiper in one position, and measuring from each terminal to the wiper (\$R_1\$ and \$R_2\$), as well as end terminal to end terminal \$R_\mathrm{T}\$. The wiper resistance is given by

$$
R_\mathrm{w} = \frac{R_1 + R_2 - R_T}{2}
$$

Question

The issue lies in taking the three resistance readings. As I measure the resistance any part of the potentiometer, the reading decreases with time. Let's say I measure \$R_\mathrm{T}\$ first, the wiper resistance can come out as negative due to the decrease in resistance when measuring \$R_1\$ and \$R_2\$. This result is non-physical and generally makes no sense.

What is the best method of holding these resistances at fixed values such that the results all work together to produce an accurate value for \$R_\mathrm{w}\$?

Probable issue

The LCR meter I am using to take the measurement is heating up the potentiometer while taking the measurement which decreases the resistance. From this it would seem that a lower measurement voltage may solve the issue, but the LCR meter only offers one setting of amplitude at ~0.5 Vrms.

I could wait until the measurement stabilises at a given value, then switch which resistance I am measuring, hoping to maintain that equilibrium while changing connections. Changing where the voltage is applied across the potentiometer will surely change the heating effect as well though, so the thermal equilibrium will not be maintained. This problem is giving me a headache!

EDIT: The potentiometers of interest have so far been 1 MΩ, and some wiper resistances I have seen have been 252 Ω, but if I measure too long on some measurements I have also found a wiper resistance to be -248 Ω.

Taking measurements while applying the LCR meter for the shortest period possible seems like one option, but I don't like it because I don't know how much the temperature of the resistances have changed


texts: How do I prove to my physics teacher that adding a battery in parallel doesn't double the current?

texts:
simulate this circuit – Schematic created using CircuitLab

My physics teacher said that the current through the resistor is 4A because each battery has a current of 2A if hooked up to the resistor on its own, and so they both have 2A of current through them so the resistor has 4A total through it because of the junction rule (this was the explanation she gave when I asked her why the total current wasn't 2A), however that isn't true because the current through the resistor is 2A when the voltage is 80 (these batteries are in parallel), and so there is 1A through each battery. How should I explain that her logic doesn't work, as current does not double when you add another battery?

Edit:
Her response to me when I asked about ohm's law: each battery provides 2A of current on its own, so they combine because apparently, you can treat each loop separately, so then by the junction rule, the 2A currents join to become 4A.


texts:
Alright so I will start with what I am trying to accomplish:

So I want to build an power inverter based welder. I see these commonly in all new Lincoln and Miller welders. These all can change the amperage in increments of 1A. From what I have found these are "SMPS" and operate around 30kHz.
I'm trying to make a MIG, TIG, and Stick rig. I get that part of it after I can generate the high amperage. It seems simple once I figure how to do that. If it maters the max draw on the main should be around 40A. Here Is what I have been looking at for the information.

So how would one do this. Ask anything else to clear it up.


texts: Understanding the statement: An antenna with 20 degree beamwidth has 20 dB gain

texts: It is known to us that as gain of an antenna increases, its beamwidth becomes narrower. Is there any formula to support the above statement?


texts:
I'm thinking of a very simple circuit to generate high voltage pulses, like this:

simulate this circuit – Schematic created using CircuitLab

The MOSFET in this case will turn on until the current through L1 ramps up to 10A, then turn off.  The pulse output is connected to a load which can have a wide range of impedances.  If the impedance is low, then the energy in L1 goes there.  If the impedance is high (higher than 600V / 10A = 60 ohm), then the 600V Vds on the MOSFET can be exceeded.  If I understand correctly, that means it will go into avalanche, and conduct until the current goes below some kind of threshold (or the voltage drops??).  This MOSFET happens to be rated for repetitive avalanche energy of  41.7mJ, and avalanche current of 47A.  The energy in L1 is (1/2) * 6uH * (10A)**2 = 0.3mJ which is much less than the rated energy.

Is this something that the MOSFET can survive?  (Let's say pulses at 10kHz, repeated indefinitely)  I've never used a MOSFET in this way, it seems like it would stress the device a lot.

When does a MOSFET in avalanche mode turn off?  Is there a way to make it turn off?

What is Vds during avalanche?

P.S. It is possible to limit the peak pulse voltage to less than 600V using some kind of RC pulse shaping network, or zeners or TVS diodes, but that makes things more complicated and is not preferable in my case.