texts:
OK so here it is. Now I am not asking anyone to do this for me, I am just confused because my professor did this in class and I just cant make sense of it. I repeat, this is not a homework question, I am legitimately trying to understand this.

Ok so the first part is straight forward I think. The phase of the resistors are 0degrees and the capacitor has a -90 degree phase shift between the voltage across it and the current through it

The voltages of the resistances are 3V and 7V and the capacitor has a complex reactance given by 1/jwc which gives -22222.2j ohms and a voltage of -44.4jV

Now the next part is what confuses me. As I understand it to calculate the voltage of the source I should add the voltages in complex quadrature. That gives me 45.5V however my professor simply subtracted |10-44.4| to give 34.4V I don't understand this at all. How can he add the two together when one is imaginary? I know that Xl (i.e. 1/wc) gives the magnitude of the reactance however the phases for each component are different so I don't see how you can just add them.

Then for the third part he again simply added the impedances together to get 27.2kohms, although I suspect this may have been a simply error copying from the notes.

Then for the last part (v) I understood that to get the average power dissipated I would need to take the rms current and use P = I^2(R) however he simply used the value of the peak current and the voltages calculated earlier on P=VI

Can someone please help me, I thought I understood this stuff but this has really confused me. Even telling me what it is I am misunderstanding without any great depth would be a huge help, I can then go and read up on it myself.


texts: Microcontroller wake-up strategies (ESP8266)

texts:
At work, we have a remote battery operated magnetic door detector that send a signal to our alarm system whenever we open a door. The battery lifespan is almost a year.

I tried to replicate that system at home. I constructed a really simple circuit around the  esp8266 Thing. It is a simple battery operated door detector that ping my cellphone each time my son open his door when he is trying to fall asleep.

The code routine is simple enough: upon activation, the esp pings a specific IP and then go to deep sleep. The wake up is done through the DTR pin. When the door is closed I keep the DTR line up. Once the door open, the DTR line is released and the program execute once and go to sleep. Closing the door reset the DTR line and it is ready for another cycle.

I also removed the power LED indicator to increase the battery lifespan. My system works fine at the end of the day. But, the battery lifespan is somewhat limited (before I removed the LED it was a couple of days. Now, it is lasting longer, but I didn't note the new lifetime of the battery). The battery is a 1200 mAh rechargable LiPo. Following up on that project, I have a couple of questions:

Is this the proper way to do such a thing?
Is there a more industry standard way? (with the esp8266 or any microcontroller in general).
Any other power management tips that might be useful to know?


texts: Is it necessary to use pickit for pic MCU?

texts:
Recently I bought PIC18f4550 dvelopment board by OUMEX. I started go through online tutorials and mess around MPLAB IDE to use it. While setting up a new project, I was asked to select a tool as shown in the picture below. I was not aware about these tools. I looked up online and its costs $70 plus (WOW) and takes about 5 days to deliver (In meanwhile I wouldn't have much to do).

Back to my question is it necessary for me to use these tools to program my MCU? How does it benefits or affects my coding overall

Thanks in advance!

EDIT:
Thank you everyone for you explanation. I think my research wasn't proper enough that I didn't even know that a I needed a PIC Programmer. Till now I worked on the development boards like arduino uno, Silicon labs 8051, etc which had it inside them so it didn't strike me that the development board I bought didn't have it. I just assumed that it would be embedded inside.
Now I kinda regret not asking for suggestions on which kind of MCU I should have chosen. Since PIC18F4550 has been in the market for a good time, so troubleshooting it wouldn't take up so much time. Anyways lets hope for the best! Again thank you so much. Your insight has helped me.


texts:
A motor on my HiFi system (which is supposed to lift a volume controller) has broken. The motor is stuck and I don't want to fix the mechanical part. I assume disassembling the volume controller would cause problems.

However, I have access to the flat cable to the complete volume unit. I'd like to isolate the motor pin. The flat cable looks like this one:

(Image source - AliExpress)

The pins are really tiny. How could I isolate the pin? It would be great if this is reversible. I thought about using nail polish. This usually works well on bigger connectors. However I fear it might be too thick or be too hard to apply on only one pin. Are there other "more professional" approaches to make such on PCB changes?


texts: Rising edge duration of a low to high pulse

texts:
In a device I am using, I see the following in the description...

"At start-up, the module requires an ON_OFF pulse sent from the host. A second pulse sent from the host will re-enter hibernate mode. The ON_OFF pulse needs to be the rising edge of a low to high pulse, this needs to be longer than 90us."

I am not clear on what the requirement is.  For time being, I have the ON_OFF line being tied to the application of power.  When I switch on, this line will transition from a low to a high... and stay high...probably very quickly.

I do not believe what I am doing is correct.  I am trying to understand the interpretation of what is asked and I think it is really the following..

Does the above mean..(High voltage is 1.8V).  "When you apply power and switch on, make the transition from 0 volts to 1.8 volts take at least 90us?"

This is of course without regard for if the line ever goes low again.

If that is so, could I accomplish the above with an RC circuit on the power line?

Here is a link to the data sheet..
https://antenova.com/wp-content/uploads/2015/11/M10478-A1_12MD-0050-3-PS.pdf

What I quoted is contained in that link.  There are other aspects of this chip which I don't quite fully understand from he datasheet.  Yet, the fact that it is not running properly is probably related to the On pulse and what I initially setup.


texts: Reducing 12 volts DC in a vehicle to 10.9 DC

texts:
I have a vehicle (12 volts DC) that has dash display that is too bright. If I install a potentiometer I can alter the power to get the display where I want it to be. This is 10.9 volts. If I read the potentiometer it reads 94 ohms.
I want to install an aluminum case wound resistor to accomplish the power drop but I can not figure out the correct unit I need. Any help would be great and thank you.


texts: Switch in series, check individually if one is open or closed

texts:
I have a safety path for a relay, that disables the power when one of two switches is triggered. To detect, which switch is triggered, I tried to implement something like the following, but it is still not working correctly, since it will only detect, when S2 is closed or open. It only works, when the supply for the logic is 12V instead of 3.3V

I need to convert the signal to 3.3V for the uC. Do you have any improvments on the scheme? I don't want to go with optocouplers, since they need around 1mA of current, which will energize the relay coil too much.


texts: does the order at which HDMI differential signals should be connected matter?

texts:
I have 8 DDI (Digital Display Interface) signals that come out of the CPU with a certain numbering from 0 to 3.
I want to connect these signals to HDMI connector.
I was wondering if there is an importance for the order at which these signals should be wired at the HDMI connector, should they correspond to D2, D1, D0 and CK in the HDMI port in terms of numbering?


texts:
I have built a device that consists of 10 PCBs connected by a backplane PCB. Each PCB contains various logic gates and a varying number of status LEDs for debugging purposes.

Never before in my life have I constructed any circuits even remotely this complex. However, by connecting some switches to the device inputs and some LEDs (and drivers) to the device outputs, today I have been able to confirm that, after weeks of designing and building, the device appears to be doing exactly what I designed it to do. Yay! :-D

However, something weird is happening: If I make more LEDs turn on, they all get darker! 8-O

It's as if the device is somehow running out of power. But I can't figure out how that can be... Here's what I do know so far:

The power supply is definitely still in constant voltage mode. It sees the current increase, and continues to supply the same voltage.
If I turn on more LEDs on a particular PCB, all the PCBs get darker, not just the affected one.
Various LEDs outside the device do not get darker, despite being part of the same circuit and being powered by exactly the same power supply.
The logic functions appear to be being performed correctly, in spite of the brightness weirdness. Most particularly, the digital outputs must be being driven at approximately the right levels.
Certain input combinations also affect the brightness even if no LEDs turn on or off. (I presume certain inputs make the gates draw more current, and this is just a different manefestation of the same issue.)
When I tested the PCBs individually, the same effect was just barely detectable. But with all 10 PCBs, the effect is pretty drastic.

I am most confused as to how two LEDs connected to the same power rails driven by the same power supply can have such drastically different brightnesses. Is my PCB enclosure possessed, perhaps?

A full schematic would be huge, but here is a rough sketch:

simulate this circuit – Schematic created using CircuitLab

Hopefully this gives a flavour of what I've built. (I've only drawin 3 PCBs rather than all 10, but in reality there are 10 PCBs connected to the backplane.)

D1 through D5 seem to illuminate normally, however D6 to D14 get dimmer as more of them illuminate. If I turn on, say, D6 + D7 + D8, then they get dimmer, and so does (say) D11 if it's on. But D1 seems unaffected. It's as if there's a current bottleneck somewhere...


texts:
On RF PCBs to bend a trace 90° you have many choices but among them Curved and Mitered bend considered as a good choice from performance POV (Both shown below).

For many years I thought that if you have enough space on your board, curved bend is a better choice over mitered bend but lately I hear an opposite recommendation from one of my colleague.

My question is in case of having enough room which one of these options is a better choice? (simulated results or real world measurement is appreciated)


texts: I need a simple circuit that will light one of 4 leds showing which of 4 dc voltages are the highest. This has to be a hardware soulution and voltages will be below 5 volts. So if one voltage is 2 volts and the others are less then the  2 volt line will light it's led and the others will be off.  If one line is 2.5 volts and the rest 2.1 the same thing.I'm Trying to make a non mechanical wind vane.


texts:
I would like to calculate the inductor value for MP1584EN.The datasheet says:
$$L= \frac{V_{out}}{f_s \Delta I_L}  (1- \frac{V_{out}}{V_{in}})$$

On the first page of the datasheet there is a typical application picture with 12Vin, 3Vout and 10uH inductor.

My calculation for this application is 2.39uH. Why? The 10uH is not too big or the 2.39uH is not too small?

My calculation:
$$L= \frac{3.3}{500000\cdot2}\left(1-\frac{3.3}{12}\right)$$


texts: I need to design a 1 pF interdigital capacitor for a MMIC design, so I am using an online calculator to find out the dimensions ( https://www.rfwireless-world.com/calculators/interdigital-capacitor-calculator.html), there is also an easy formula for that. Everything is straightforward but the final capacitance out of the formula and the online calculator is Pico Farad per cm, whereas I am asked for a 1 pF capacitor. So, I wonder do I need to consider that per cm here when I am designing it and get rid of it or should I assume to design a 1 pF capacitor means 1 pF/cm.


texts: can you turn a visible laser pointer into a uv one?

texts: I was wondering if there is anything I can do to make a visible laser pointer uv with (or without) messing with the laser. like if I simply shot the laser pointer through some device or screen that would shorten the wavelength? thanks for any help.


texts: JTAG and additional external power supply

texts:
I have built a board for driving some external peripherals which need up to 9V. The CPU (Cortex M0) is powered with 3.3V.

My main power supply is a 9V battery. A step-down converter provides the 3.3V for the CPU (conntected to VBAT and VCC pins).

Unfortunately, I am having some troubles to connect a JTAG interface (ULINK2 with ARM20-pin interface) to the CPU which also provides VCC lines with 3.3V to power the CPU.
I'm not sure how I should connect the VCC lines of the JTAG interface.

Do I have to combine these two power supplies (also connect JTAG's VCC to VBAT and VCC)?
Will the JTAG interface work if I do not connect VCC at all?


texts: Diifference between INA827AIDGK & INA827AIDGKR

texts:
Whats the difference between the same package of the IC INA827 - INA827AIDGK vs INA827AIDGKR?

The datasheet makes no mention of any differences.

Except in in.element14.com

where INA827AIDGK is mentioned as 1 Amplifier, but
INA827AIDGKR is mentioned as 3 Amplifier.


texts: fool device that lipo battery is connected

texts:
I want to hack my portable device, so that it does not use lipo battery anymore. I want to have it using just external power supply (don't ask for reasons).

Unfortunately after disassembling the device and removing lipo battery, the device does not work anymore. When connected to 5V DC the red led flashes, as if it was to inform me that lipo battery is dead.

No other functionality of the device is working.

That bring me to the question: What is the best way of fooling device that lipo battery is connected? The device obviously wants to charge the battery if it has low voltage.

My ideas so far are:

connect 4.2V DC directly to the place where battery was connected (how to get 4.2V, having 5V (USB) as input voltage)
be brave and connect 5V and hope that internal voltage regulator will not blow up and that none of the red-flashing-diode fail safe will not kick in.
???

Thanks,
G


texts:
This is out of a 600 watt computer power supply (CoolMax ZX600) and I don't know how to identify it without markings or a schematic and hoping someone can help.  The PCB spot for this is labeled BD1 and the main transformer is a ERL-39 (17RL3927).  I've looked on the sides and the back and no markings except the "Sep" and "H1" on the front as shown in image.  Thanks in advance for any help at all, trying to replace.  Need to add that this does show AC on the PCB for two inner pins.

Also the dimensions are
Width = 22mm
Height = 18.5mm
Thickness = 3.2 - 3.3mm


texts:
Years ago I bought a computer case because my other one was getting too small for the components. After moving all of the parts and booting up, one of the first things I noticed was that my guitar would very noticeably pick up interference (typical magnetic hard drive clicking sounds and so on), increasing in intensity and volume as I moved my guitar closer to the case. This never happened with the old case.

The interference is audible both through the speaker of the amp and through headphones connected to the amp. It occurs when the pickup is in the 1st, 3rd, and 5th position (cheapo knockoff fender electric guitar so 3x single coil pickups).

One noteworthy thing I suppose is that this new case material was labeled as "SECC" material, the old case simply listed "Steel", if that makes any difference.

The main issue is described above, below are just some more details.

This is a pretty big nuisance as I can't record anything without constant hissing unless I have my computer completely powered off.

I am looking to buy yet another case (I've been sitting on this one for a few years now) and want to understand whether it's a problem with the case material or if there is an alternative cause.

No new hardware was added initially when I switched cases so it could not have been a new component. In my unprofessional opinion I am leaning towards blaming the case material for the issue... honestly the material feels extremely flimsy, and bends easily compared to the rigidity of my old case.

I'm sorry if this is the wrong place to be asking such a question since it's a bit computer heavy however it involves concepts that aren't generally discussed on conventional computer boards. Thanks if you've read this far and I hope there's a concrete explanation behind the phenomena I'm facing.


texts: Is it true that a SD/MMC Card does wear levelling with its own controller?

texts:
I can't find any reliable information about this. I don't have the full specification of the SD/MMC Card hardware.

Is it true? My high-level application doesn't need to be concerned with wear leveling when working with these cards?

EDIT

Could someone confirm that wear leveling is guaranteed by the SD specification? I want to be sure, because it looks like most vendors do it, but it is not required by the specification.


texts: Air gap in switching power supply transformer

texts:
An article I have read regarding switching power supplies (https://sound-au.com/articles/smps-primer.html) says that push-pull, half-bridge, and full-bridge switching supplies don't use an air gap in the transformer.

Now, flyback converters need an air gap since their unidirectional operation puts a DC component in the transformer's primary current.

But would it be advantageous to use an air gap in a high-power (say 24VDC out at 50 Amps) or very high power (340VDC out at 800 Amps for a high-power air ionizer) full-bridge converter's output transformer? It seems that it would be great to do so, since the transformer would be much more resistant towards saturation if the microcontroller ever fires the switching transistors on one side longer than the other, but what are the disadvantages?


texts: Do motors run on an Ac source? If it does then do we need to convert ac into dc before supplying it to the motor?


texts: ARM Cortex M software update via bootloader

texts:
I wish to update the software running on a node having a ARM Cortex M4 MCU.

to do so, I understand I will have to run a bootloader in my TI ARM Cortex M4 development board that can receive a binary file over-the-air and program certain section of flash. I understand the functionality of receiving binary file over-the-air will have to be added to this bootloader.

This sounds all correct but I do not understand how this can be achieved. How is it possible that I program parts of the flash in the MCU by the same MCU itself?

Do I need additional hardware to do update software running on my node? All I want to do it to update the software running on my node over-the-air. A bin fine can be downloaded over HSDPA. For easy testing I can do this over Ethernet.

I would so much appreciate if someone can elaborate how this process is done in a more detailed format  for me to understand the procedure. Thank you very much.


texts: Digital-to-analog conversion of a product of digital inputs

texts:
If we have a 4-bit DAC, which converts a 4-bit binary signal \$ X = X_3 X_2 X_1 X_0\$  to an analog signal \$Y=X/2\$ (i.e. 1010 -> = 5 V, or 0111 -> 3.5 V).

How can we create a DAC, using any number of upper-mentioned DACs, OpAmps, and lower level circuits (Like And, Or, Xor, etc) that converts the number: \$ \displaystyle\frac{X\cdot Y}{4} \$ to analog value (i.e. X = 1010, Y = 0011 -> 10*3/4 = 7.5 V)

THanks


texts: LiFePO4 in parallel with solar charge controller?

texts:
I've decided to replace my lead acid battery bank with LiFePO4.

I'm using the battery bank in a motorhome, where SoC can typically be at 30-50% for days, which is unacceptable for lead acid - just one of the many problems with lead acid.

I will build my own BMS. Coloumb counting, connecting/disconnecting MPPT/alternator charging, monitoring cell voltages, bottom balancing, and so on.

Once the battery is fully charged, I would like to draw all power from the solar charge controller, while the battery is in parallel, so that when the solar power is insufficient, the rest is drawn from the battery.

But I also don't want to apply a "float" voltage to the battery.
I've considered mounting a diode which can be bypassed with MOSFETs when charging.

But is there a better way?

simulate this circuit – Schematic created using CircuitLab


texts:
I would like to know whether R24 has been correctly applied to pulldown the EN pin when none of the diodes are switched on.

The idea here is that voltages higher than 3.3V may be applied from any of 3 sources to bring the EN pin high.  The zener forces these voltages down to the maximum pin tolerance (3.3V).  When none of the diodes are switched on, the EN pin must be held low.

Alternatively I could put a high value pulldown in parallel with the zener.

Edit: A high level requires 1.7V and low less then 0.5V.  Pin leakage current is 20nA.  Input voltages range from 3.3V to 5V when active otherwise float.


texts: Transfer function for a temperature sensor

texts:
I have a STLM20 temperature sensor with the following transfer function:

$$V_{0}=\frac{-11.69\text{mV}}{C \cdot T} + 1.8663 \text{V}$$

I have solved it for \$T\$ and it should be:

$$T=85.543\cdot (1.8663-V_{0})$$

Is this correct?


texts: How long does it take to receive data from a cable, turn it into bits, then send it back out again?

texts:
I need to read in data off of a fiber optic (or copper, though I figured fiber optic would be faster) cable, convert it to bits, do something with it that should only take a clock cycle or two, then send it to the next computer to deal with it.  It'll need to jump between 100 to 1000 computers that are 50 to 1000 ft apart from eachother.

If I can shave half a nanosecond off of the time it takes get it in and back out again that would be great just because it needs to travel through so many computers.

So the question is, how quickly can I do this?  Would doing it analog for some reason be faster than digital? Anything else that might speed up this process.


texts:
I am designing a 2 layer PCB that doesn't deal with high speed signals or high currents (sensor board communicating over Lora via SPI and I2C) but does have a LoRa (900MHz) RF daughter board to one corner very close to the power source.
My board has ground planes on both sides but also signals on both. I am trying to keep signals to one side as much as possible, but there are some mechanical constraints that tie my hands a little.
So to make the grounding as good as possible, I am adding vias connecting both ground planes as much as I can and eliminate potential ground islands. I am laying them out in a grid with 3mm between the vias and 0.2mm drill.
But I am wondering if both from an electrical engineering point of view, and a cost point of view, is it "the more the better"? Or does adding a lot of ground vias add cost to PCB manufacturing, or is there an EE drawback to adding a lot of ground vias?


texts: Explanation of performance graph of FPGA design

texts:
After implementing a mathematical function on a FPGA chip. The following graph shows for ~40 inputs the time response, i.e. how long it took to get the output calculated. This data is part of the results of the simulation, which took every input from \$0\$ to \$2^{32}-1\$ (the input and output are integers), so to emphasize the question, only a portion was put into the image.

The y-axis are the times of execution in ns, the x-axis are the input values. Now, can someone explain the spikes in the graph, i.e. the alternating ups and downs? What could influence such behavior?

The function, this chip implements, is of the form $$f(x) = \sum_{k=0}^x{\frac{g(k)}{h(k)}}$$ for the input x, where both g(k) and h(k) are polynomial functions. The total complexity of the operation is $$O(x \log x)$$

PS: The FPGA is Altera Cyclone II, if it has any impact on the answer.


texts:
I am new to electronics and microcontrollers. I am using an LPC1768 and a hc sr501 PIR sensor to create a simple motion detector. I have connected the pins of the PIR sensor to the breadboard and the lpc1768. I have imported the code from the mbed library however on moving my hand across the sensor the led does not light up.

#include "mbed.h"

DigitalOut led1(LED1);
DigitalIn alarm(p29, PullUp); //internal pull up

int main() {
    wait(2);

    while(1) {
        if (!alarm){
            led1=1;
            wait(2);
        }
        else
            led1=0;
    }
}


texts: I couldn't find the flow sensor datasheet

texts: I want to know whether it is working.I want to know the VCC GND and the data terminals.what do I have to do to get 300mV out of here?


texts: How does this analog Op-Amp multiplier-divider work?

texts:
In AN-31 there's a 4 opamp analog multiplier divider. The quantity and complexity of feedback paths is staggering!

How does this even work? And how would one design something like this, short of divine inspiration?


texts: Differential pair on a PCB region without a reference plane

texts:
I was reading the datasheet for an Ethernet interface layout from NXP and I found they didn't use a reference plane in the region where they routed the differential pairs. I couldn't understand why they do that and I didn't find an answer. The datasheet explains it that they wanted to reduce the capacitance but how does the signal couple? It couples only with each other?

Datasheet AN2759 page 16


texts:
I have a 110VAC input, 24 VAC output transformer that includes an Elsen WA128 fuse on the 110 v input side.  I accidentally momentarily shorted the 24v.  This blew the fuse.  I want to replace the fuse with an equivalent, but I need to know if this is a slow or fast acting fuse.

This transformer supplies power to a skylight window controller.  The window is opened and closed with a DC motor.

The description of where slow and fast acting fuses are used is confusing: fast for electronics, slow for motors.  But this application does both.

Thank you for your responses.  I admit that I was a bit sloppy - I said the transformer was 110 v, it is actually 120 v, I apologize.  For further clarification, I have had this transformer in use for over 10 years without problems.  It is rated at 55 VA.  I accidentally touched the 24v lines together momentarily.  A day or so later I realized that the skylight no longer worked.  I found the problem to be the transformer.  A VOM test showed that the secondary had continuity, but the primary winding was open.  I drilled out the rivets and unwrapped some tape around the primary winding.  I then found the Elsen fuse, connected in series with the primary winding.  A VOM test shows continuity through the primary winding is good, but the fuse is open.

Although I am not certain about this, from the comments above, and other comments on the web, it appears that the Elsen fuse is both a thermal fuse, AND a current fuse.  I am not sure about this, but it appears that the Elsen part is no longer made.  I was able to find a possible replacement on eBay, but that is when I started thinking that a suitable replacement might be a better approach.

To my surprise, the momentary short circuit of the transformer also caused the skylight electronic circuit board to fail.  This is a different problem, and also one that I have not yet solved, but a different subject.

The transformer is mounted in an open area in the basement, and the duty cycle is really really trivial.  The skylight had not been used for several days before my momentary short circuit mistake.  I seriously doubt that the fuse blew due to transformer heat over 128 deg C.   I think it was due to a few milliseconds of secondary short circuit.

The part referenced above, thermal fuse NTE8070-8242, will pass up to 15 amps.  I have not been able to find the current rating of the Elsen WA128.

My guess is that this transformer was NOT made specifically for this skylight, and therefore the fuse in the transformer was intended to protect the transformer PRIMARILY from over temp, and only secondarily for over current.  But I seem to have blown the fuse by over current.  A 55 VA transformer at 24 v translates to a load of about 2.25 amps (ok, 2.29).  I think the NTE part would not protect against a transformer current overload.

So, my questions are:

have I analyzed the problem correctly?
Should I pursue the NTE (15A) thermal fuse, or try to find the obsolete Elsen part?


texts:
I have 2 boards connected via a ribbon cable.

CPU board is an 3.3v ARM providing the I2S signals(bit clk, data, L/R signal).  I'm using 44100 - 16 bit audio so the bit clock is just approx 1.4 mhz.

The second board has a TI PCM5100 DAC.  (I made a small PCB to test with) Today - the two boards are hacked together using 4 inches of ribbon cable and 6 inches of individual wires connected to the CPU board.

The testing proved successful.

I want to change both boards to enable a 12 inch ribbon cable to join the two boards.

Space is a concern so I don't want to wire the ribbon cable as G S G S G S G but just supply signal lines next to each other.

Currently for testing I have no termination - just the CPU pin driving the DAC via the wire/cable.

Researching ribbon cable impedance, I find that it can range from 100 to 150 ohms depending on gnd/signal pairing or not paring.

If I place a 120 ohm termination resistor at the PCM5100 I2S inputs that means the cpu I2S pin must source around 27 ma (3.3 / 120) - which is outside the pin's drive specification.

I can add a buffer/driver on the cpu board to drive the line but not sure if that is a good direction to go.

Should I be concerned about line termination with 12 inches of ribbon cable?

Thanks in advance for any comments.

Joe

Update - Test my understanding:

I have 10 signals that pass via the ribbon cable:

2 with bit rates of approx 1.4 mhz (I2S bit clock and data)
1 with a rate if 88 khz - I2S L/R signal

2 I2C signals (clk and data) - baud 100 khz or 400 khz

and 5 nearly constant level signals:
3.3v
GND
Reset
Mute
IRQ

If I add 100 ohms in series with the two I2S signals (BCLK and I2S Data) and position them in the ribbon cable as defined below, then I should have a good chance of addressing my concern - right?

Ribbon cable layout

GND
I2S Bclk
3.3V
I2S Data
Reset
I2S L/R signal
Mute
I2C CLK
IRQ
I2C Data


texts: SPI Clock Frequency changes when level shifted

texts:
I'm using Adafruit's TXB0108 bi-directional 8 channel level shifter with my Arduino Uno. The SPI clock from Pin 13 is level-shifted through the first channel of the level shifter. Measured with my multimeter, the frequency of Pin 13 is 3.439Mhz. However the measurement of the output of the level shifter is 245 (+/- 10) Khz. And I have no idea why! I checked the datasheet of the level shifter, and I think it should be good to 10 Mhz.

Running the following code the following:

#include <SPI.h>
void setup()
{
  pinMode(13, OUTPUT);

  digitalWrite(13, HIGH);
  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV2);

}
void loop()
{

  byte pot = B0;
  SPI.transfer(pot);                        //  Do SPI transfer of variable pot
}


texts: What does it mean that a multimeter is four and a half digit?

texts: The fluke 87-V is advertised as a "four and a half digit" meter. What does that mean, how does half a digit fit into the equation?


texts: LM317-based step-up boost voltage converter - what?

texts:
I found an interesting e-bay listing: LM317 DC-DC 1.5A Adjustable Step-up Boost Voltage Converter Module 1.2-37V

Now I am a beginner, but I know the LM317 is a step-down regulator, and I couldn't find any reference on it being used in a voltage boost circuit. This forum even talks about it's impossibility. The picture on ebay also "smells like" a standard step-down circuit. Considering these I am 95% confident that the module for sell is actually step-down circuit, but I would like to ask your opinion anyway:

Is it possible to make a reasonably simple voltage boost circuit based on the LM317 voltage regulator?


texts: Does a MOSFET need current to operate without switching on and off fast?

texts:
I know MOSFETs need to have a bootstrap circuit for N-channel on the high side of, say, an H-bridge; but if you're running AOK42S60L with this (as a general on-off switch, not as a fast switched component) PVI1050N x 2 (in series) @10V

Do you still need a large initial current supply to "charge" the gate capacitance fast enough for the first turn-on phase (so it doesn't spend any time in the linear region)?


texts: If OFDM did not have a cyclic prefix or zero padding would have equalization of the individual sub-carriers been possible in the frequency domain?


texts:
I'm doing PCB layout for a USB 3.0 connection and I'm curious about if there's a length match requirement between the unidirectional super speed pairs and the bidirectional high speed pair.  This isn't for a specific USB 3.0 driver or receiver, but what is considered good practice for operation.

For clarity I'm going to refer to the bidirectional high speed lines as BI+ and BI- and the unidirectional super speed lines as TX+, TX-, RX+ and RX-.  What I have seen so far is listed below:

TX+, TX- lines should be within 5 mils (0.13 mm) of each other.
RX+, RX- lines should be within 5 mils (0.13 mm) of each other.
BI+, BI- lines should be within 50 mils (1.25 mm) of each other.
The TX pair and RX pair don't have any length requirement with respect to each other.

The length matching requirements in pairs make sense, but I'm not confident that the TX pair and RX pair don't have a length mismatch requirement for all devices.  I'm also not sure if the BI pair has any length requirement with respect to the TX and RX pairs.  Are there any general rules of thumb to follow for matching the lengths of pairs to other pairs to avoid errors?


texts: Average input current in forward converter

texts:
I am trying to understand how to calculate the average input current of a typical forward converter. If the converter has negligible magnetizing current, a large inductance and a turns ration of n1:n2:n3, based on my understanding, the input current would be:
Ig = D*Iinductor * n3/n1
But this does not seem to be correct.
Any help/pointer will be much appreciated.
Thanks


texts: Change Direction of 12v DC Motor Rotation using Relay

texts:
I want to make a circuit to change 12 Volt DC Motor direction and move some thing between two points. Using Relay or some basic limit switches.Like this Image.
I got a Circuit As i want...
AUTOMATIC FORWARD-REVERSE A MOTOR
The following circuit allows a motor (such as a train) to travel in the forward direction until it hits the "up limit" switch. This sends a pulse to the latching relay to reverse the motor (and ends the short pulse). The train travels to the "down limit" switch and reverses.

If the motor can be used to click a switch or move a slide switch, the following circuit can be used:

Please Help me to understand this circuit and how to wire these things.


texts: IC decoupling capacitor design recommendations

texts:
I use some decoupling capacitors (100 nF) for low speed ICs (< 1 MHz) and I need some recommendations to verify my routing. My layout uses two layers:

Top (Red) with Vcc
Bottom (Green) with GND

And I have this IC as an example:

The Vcc layer is connected to my cap and the cap is connected to the IC over pin 28. So the IC is directly connected with the cap and not with the layer.

Here is the question:
Should I do the same for the ground connection or is it fine to connect the cap as shown in the image? The "bad" thing with DIP-packages is the long routing distance between GND and Vcc (pin 14 and pin 28) for example.
Then the next question is how do I handle decoupling capactitors for ICs like the FT232RL which has more GND than Vcc pin. Should I connect all GNDs and route them to the GND of the cap or can I connect them directly with GND.

What is a smart way to do it?

Update: Add the changes


texts: Maintaining Constant Input Voltage (DC) and Limiting Power Drawn from a Power Supply

texts:
I am utilising a power supply capable of providing up to 24 VDC and 3A for a project, however, I am unsure of how to fix the source voltage at 24V nor limit the power drawn by my project to 10 Watts.

As you can probably tell I am a complete novice. Any help would be much appreciated!


texts: import new component into LT Spice with .cir file

texts:
my desperate attempt to simulate a circuit led me here.

I have a low noise amplifier which has a HEMT as its transistor.  (ATF38143).  I have been trying to create a component in LT Spice and came across this website.
The page linked here is a .cir file for ATF34143 and it was the closest HEMT I could find.

I copied and pasted the script in a text editor and saved it in the .cir format.  Then, I opened it with LT Spice, highlighted the name of the HEMT in the first line of the .cir file to create a new component.

Unfortunately, when I attempt to simulate the circuit, it results in an error.  I have tried the same simulation without the user defined HEMT and the result of the simulation appeared reasonable.

I have also tried the .cir file of a different transistor from the same website (linked here) and went through the exact same steps to create a component corresponding to the .cir file.  It worked smoothly.

Could someone take a look at the content of the cir file for the ATF34143 transistor shown on the website and point out what's wrong with it? Given that I was able to create a new component with a different .cir file, I am certain what's in the .cir file for ATF34143 is wrong.

Shown below is what the website says the .cir file should have. (It's a bit unclear which parts should be in the .cir file given that there are two instances of ".SUBCKT" and ".ENDS")


texts: Help me to understand VOOC fast charging for lithium ion batteries?

texts:
I know common VOOC charger have fast charging rate of 18W(9V/2A). But how it possible even current is only 2A. I mean 2A current have only stored charge 2000mAh(2A*1h). How changing voltage can charge battery faster?
On other side Oneplus Dash charger supports upto 20W(5V/4A). This makes sense that higher current can charge battery faster. But again how can  just 5V can charge battery to 4A rating?

Thnaks for answer/comment. Corrections and suggestions are welcome.


texts:
I have some questions for the series connection of capacitors. It would be great if someone could help me get these.

What will happen for the below cases when you have 2 capacitors in series and 2 supplies connected to the extreme ends-

simulate this circuit – Schematic created using CircuitLab

When the supply V1 is a fixed voltage V1 and supply V2 is a fixed voltage V2. What will be the charge and the intermediate node voltage Vb?
When the supply V1 is ramping from 0 to a voltage Vs and supply V2 is a fixed voltage Vs. What will be the charge and the intermediate node voltage Vb here?
For case 2, When there is some initial charge on any capacitor , say C1 has Q_ini charge, how will the individual charge and intermediate voltage Vb get affected?


texts: Connecting a N.O. grounded switch to a scanning switch matrix

texts:
I am working on a project that includes a scanning switch matrix. It also includes a joystick with an integrated push button. I am out of IO pins on the micro, but there are gaps in my switch matrix, so I would like to integrate the push button into the matrix. However, the button is permanently internally connected to the ground pin of the joystick.

I am pretty sure I can use an NPN transistor to connect the signal line from the push button across the matrix pins like I would a regular push button, but I want to make sure I'm not missing something important.

I sketched out something I think might work. R3 is the internal pull-up resistor in the micro-controller. For the other switches in the matrix, Q1 would be replaced by a N.O. switch with with series diode connected between ground and the output. I feel like my proposed circuit is backwards and will actually only activate when my push button is NOT pressed, but I think that would just need another transistor to invert that signal.

This is what the circuit looks like for a normal switch in the matrix (note that neither pin is locked to GND as is the case for the switch I am now trying to integrate).

The matrix scanning works by setting a single column low and the rest are tri-stated. Then all the rows are read in. It then switches to the next column and reads in again.

Does anyone have any better suggestions or corrections?


texts: What would it take to spark through electrical tape?

texts: Forgetting for a moment that wires can get hot, and that electrical tape can melt because of it: I've been wondering how much voltage/amperage it would take to spark through your standard house hold electrical tape. While the electrical tape is an insulator, nothing is a perfect insulator, right? It's just a matter of resistance, isn't it?


texts: Receive GPS Antenna and cable simple confirmation of operation

texts:
I am in need of testing a GPS antenna and cable assembly after installation at a reasonable cost.

I have a GPS antenna installed on an airplane, then the coax cable from the antenna goes down to the receiver. The system is already assembled and validated technically and in production, but we find that after some shipments around the country something goes wrong in the cable assembly.

We are testing out a complete system inside of a metal hanger so there is no available sky view for real satellite reception. Besides we are trying to control the test and provide a go/no-go simple automated test.

We really want to know that we have not pinched the coax cable and confirm that all the connections are still good from outside the antenna through the aircraft and all the way down the cable. I am thinking it should not be necessary to pass a GPS capture and location measurements. I am thinking that I can find a simple method to transmit an RF signal in the GPS range and then receive it on the other end of the cable to confirm the antenna and all the connections and  the cable are still good.

I am thinking that I could attach an instrument on the receive end of the coax cable to detect what is transmitted from a non-contact transmitting antenna held a few inches above the GPS antenna.

Any ideas out there? Any simple equipment that does this already that can be connected to a Windows or Linux PC to initiate the test and read back the response signal if not to say go or no-go?

----- edit of March 25 -----
At this point, I believe the best way to go on this test effort is to provide a signal generator driving an antenna, then provide a receiver / detector at the "bottom" end. Now I need to find hopefully a single PCIe card that will give me an L-Band range signal generator and a receiver with an API to control and read from s/w. I think the SDR version is more complex than it needs to be but that still may work. And since the quantities of those are high, that may get those prices down to a good range anyway.

Any ideas out there? I am looking at Pentek, Agilent, NI and any others that may be appropriate. I haven't yet figured out what to call it to do my search for what I need, other than a Signal Generator and Receiver.


texts:
How much current the PS-on pin on the motherboard's power connector can sink?
can it sink 100-200mA?

(to activate a relay/solid-state-relay when the motherboard wants to turn/keep on the computer)
(e.g. motherboard's PS-on pin >>> relay/solid-state-relay >>> my controller board >>> computer's PSU's PS-on wire)


texts:
I am working on a latching on/off switch, There are many ways to do it by using discrete components. But I want to use an IC to perform that task. I found MAX16054 IC which is similar to my application but the drawback with that, working voltage is 2.7V min. While I am working with minimum of 2.1V.
Is there any better way to find the solution for this, I don't want to use 555 timer IC.
Please check the circuit


texts: Estimate the Flux Linkage of a PMSM Motor

texts:
I'm not sure if it is possible to estimate the flux linkage of a PMSM motor (star connection) by the controller itself, where I can measure the input voltage, all the phase currents and the velocity. Measurements of R and L are also available.

The flux linkage is defined as:

$$
\lambda_m = \sqrt{2/3} \frac{2}{P} K_b
$$

Where P=Number of Poles and Kb theback EMF constant. So I need to come up with Kb first, but I don't know how I could achieve this. When I turn on the power supply to speed up the motor to a constant speed, I cannot measure the back EMF, because I can only measure the input voltage. Is it even possible to measure the flux linkage with this setup?


texts: Altium create negative text on polygon/fill

texts:
I need to add some text to my PCB and put it on polygon part. I can do this but only as a layer but I need to have my text as negative(non copper) layer. Anybody knows how do the trick? It's like polygon cutout but need it for text.

Thanks!


texts: What capacitor(s) will be best replacement

texts:
Living and working in West Africa. We cannot purchase capacitors here, we can only beg (and pay) used parts from the workshops which rewind electrical motors.

Our gray-water-pump is broken, the always-connected run capacitor is dead. It is a simple 400W single phase induction motor. I can start it by hand in either direction. But it will not start any longer by itself. The dead capacitor is marked 6 uF.

I found no 6 uF capacitor locally, have already asked in three different towns at several workshops. I found a used 5 uF (cylindrical shape, same size as the dead one) and a 1,25 uF (small box-shaped unit).

Because of the keeping-the-water-out-seals, I cannot open the pump many more times, because the rubber rings suffer with each opening and closing of the case.

Question: Should I install the combination of 5 uF + 1,25 uF in parallel or just install the 5 uF? What are advantages and disadvantages to consider please?

Are there formulas which I could apply, having very little documentation? (It is just a dirt-water-pump from a garden-center labelled 400W.) If I could calculate the "nominally needed capacitance" then I could better decide whether to go 1 uF too low or rather 0,25 uF too high with the added complcation of installing two different capacitors in parallel.

What do the users think please, who got real-life repair experience?

I can tell you that the motor without any load (dry on my work bench) does start on the 5 uF alone. But I wonder whether it will be "enough" with the added load of having the blades submerged in the water (physical friction). The local repair-veteran (without any formal education) has recommended to just install the 5 uF. But I would be 17% off the original capacitance.

Why do I not just order a new 6 uF capacitor from Germany? I did, but mail-order and shipment to West Africa takes several months. And I do love my family and want to repair our toilet-flushing system. So your help is appreciated please. This is not a theoretical question but meant to help me fix a real problem. Thank you. (This is my first question here. If I got it wrong, please do not hate me, rather please help me edit to get it right. I love Stackexchange.)


texts:
I have a doubt about an electronic circuit.
Below is the circuit diagram of the fan controller in my 3d printer controller ( Printrboard Rev D ).

This circuit can control the speed of a fan.

I know that MOSFET can be used as a switch. When sufficient Vgs is applied, MOSFET will turn on and so the load (fan).

This is my understanding of this circuit, please correct me if I’m wrong or missed anything?

5V PWM is a digital signal and by adjusting the duty cycle, I can control the average value.

For 100% duty cycle Average voltage = 5V
For 50% duty cycle Average voltage = 2.5V
For 0% duty cycle Average voltage = 0V

So if I apply a 5V PWM with 50% duty cycle to the gate of MOSFET it will turn the MOSET On and OFF depending upon the Ton and Toff value(Ton= Toff since duty cycle is 50%). Since this ON and OFF happen so fast, if I check the output voltage using a muti-meter it will read 6V (50% of 12V), and in a CRO or DSO I can see the 12 V PWM. Therefore, the fan will operate at 6V and will run at half the speed (if the rated speed is 500RPM, it’ll run at 250RPM).

I tried to explain with a picture also

Is this how this circuit changes the speed of fan?

I'm not an electronics guy so I'm expecting simple answers

Thanks


texts:
simulate this circuit – Schematic created using CircuitLab

Is it safe to consider the resonance frequency  of a second order RLC circuit to be  alway equal to 1/sqrt(LC) or the transfer function has to be calculated?

When there are three active components such for example for the case of bridged-T RLC network as is shown in the figure, is the resonance frequency still 1/sqrt(LC)? If capacitances are different, would that mean that there are two resonance frequency?


texts: How can I simulate and handle an automotive load dump?

texts:
Long story short, I'm designing a little device to monitor a sensor or two in my car.  I'm not an EE, but I'm a stickler for knowing things will work right and that I won't have wasted my time and money only to have my device fried by less-than-ideal power sources. :)

I've managed to cobble together a power supply circuit that incorporates both a surge stopper (LT4356) and a linear regulator (LT1963AEQ), with a nice TVS (SMAJ40A) sitting in front, to give me regulated +5V and hopefully withstand the mythical load dumps referred to in SAE articles and TVS datasheets all over the internet. :)

What I'm stuck on now is... how do I verify what I have is good?  What could I do better?

I've had a few ideas on testing it: really mess with the circuit and attach high voltage DC supplies to the inputs... touch wires briefly and what not.  I'd really like to know if this thing can survive an honest load dump, though.

As far as the design... is my TVS diode stout enough?  Is there another approach I should take like shoving in a big cap or two to slow down the spikes and give the TVS less work to do?  I've asked in IRC channels and perused the web... and I've seen everything from DC line filters to inductors to huge caps to diodes to tranzorbs and a million other things.  I'm just slightly confused on what is considered a good baseline approach to protecting a circuit from the rigors of an automobile's DC power system.


texts: Higher gain at higher frequency in instrumental amplifiers

texts: I am using an instrumentation amplifiers (INA181). When the gain (G) is set to 10000 the behavior is as expected. However, when G is set to 1k there is an increase in the output signal going with the frequency. Why could this be happening?


texts: What does "correlation" mean in signal processing?

texts: What do the words "correlated" and "uncorrelated" mean in signal processing? E.g. - "uncorrelated white noise.."


texts: 60hz Astable 555 timer circuit not oscillating

texts:
Yet another electronics newbie here :)
I have tried to construct a simple 60Hz oscillator using a NE555 timer in astable mode, yet it does not seem to be oscillating. To test it, it has been connected to a speaker as I do not have access to an oscilloscope or any other fancy test equipment.

R1 and R2 are 10 and 47 ohms, and C is 220uF. According to my own calculations and to online calculators this should give a frequency of ~63Hz. I have tried the circuit using other resistor values - all of which work - but do not give the desired 60Hz.

simulate this circuit – Schematic created using CircuitLab


texts: Proof that every circuit with diodes has exactly one solution

texts:
Consider an electronic circuit consisting of linear components plus a number of ideal diodes. By "ideal" I mean they can either be forward-biased (i.e. \$v_D=0\$ and \$i_D\geq 0\$ ) or reverse-biased (i.e. \$v_D\leq 0\$ and \$i_D=0\$).

These circuits can be calculated by arbitrarily declaring each diode either forward-biased or reverse-biased, and setting \$v_D=0\$ for every forward-biased diode and \$i_D=0\$ for every reverse-biased diode. After the resulting linear circuit has been calculated, we have to check whether at every forward-biased diode \$i_D\geq 0\$ and at every reverse-biased diode \$v_D\leq 0\$ is satisfied. If yes, that's our solution. If not, we have to try another set of choices for the diodes. So, for \$N\$ diodes, we can calculate the circuit by calculating at most \$2^N\$ linear circuits (usually much less).

Why does this work? In other words, why is there always one choice that leads to a valid solution and (more interestingly) why are there never two choices that both lead to valid solutions?

It should be possible to prove that on the same level of rigor with which e.g. Thevenin's theorem is proven in textbooks.

A link to a proof in the literature would also be an acceptable answer.


texts: How can I generate voltage for a science project?

texts: I am performing a science experiment where I need to generate 25 volts, 45 volts, and 65 volts. I need to attach the power source to electrodes by alligator leads into electrophoresis gel. What would be the most efficient and cost-effective way to generate these voltages.


texts:
I'm working on a project where I'm measuring the current into/out of a battery (currents may be as high as approximately 150A, and I'm not aware of any hall effect devices that are continuously rated for such currents and/or don't break the bank) via a shunt resistor in-line with the positive line of the battery. To measure that current, I have to measure the (comparatively small) voltage across that shunt somehow.

Normally, I would use a instrumentation amp to amplify the signal, then feed it straight into an ADC on my microcontroller. However, since current can flow both into and out of the battery, I'd have to deal with the voltage range across the two terminals of the shunt being \$±150mV\$. (I'm making up numbers here, but that's around what I'll be dealing with.)

My question here is as follows: How do I go about sampling this voltage from the shunt in the simplest way possible?

I'd like to keep the circuit as simple as possible, as I'll need to (eventually) expand this project to sense current on several batteries simultaneously.

What's the best approach to sampling this voltage?

I'm thinking that I could somehow apply a DC bias to the incoming signal to 'shift' it into the range of \$0-300mV\$ so it's easier to sample, but I don't do much work with analog electronics or op-amps to really know where to begin.


texts: dq transformation using phasor quantities

texts: 3 phase AC quantities can be either represented in the Time domain or the phasor domain. It is also possible to transform 3 phase quantity to alpha-beta or d-q-0 reference frame using Clarke's transform and Parks's transform respectively. Usually, the transformation is done on AC quantities in the time domain. My question is whether Park's transform can be applied on AC quantities in the phasor domain.


texts:
I'm using ATMEGA644 in a measurement circuit.
I'm providing the primary supply from a battery + boost regulator and if/when the voltage (the one that I have to measure) is available I want the supply to switch to that voltage. Switching will be done using a relay. So I figured I need to hold 5V till the release time of the relay which is nearly 15ms.

I know I'll have to hold 5V at the supply pin of ATMEGA644. I think I can use a capacitor to hold 5V for 15ms but I'm not sure.

My questions are:

Can I use a capacitor to hold 5V for a current flow of 50mA? If yes, then what will be the circuit and how will I be able to calculate the capacitance?
If not then what circuit should I consider following? or what other option should I be looking into?


texts: Rejection of particular frequency in a signal which contains many frequencies in its spectrum (fourier transform)

texts:
How does a filter know which frequency is to reject?

Detail:

A signal may contain a lot of frequencies. How could we surely say that the result of linear combination of the result of applying these frequencies individually will produce the same result as applying the whole signal?

At any point of time there will be a voltage level which will be applied to a circuit (linear combination of amplitude of contained frequencies.) Circuit only "sees" voltages, so how will it know that which frequency to reject? I mean the resultant signal amplitude values will be the value, after subtracting the value of rejected signal frequency amplitude from original input signal value at every time instant.


texts: Can MCU ROM and RAM limitations be scaled?

texts:
Please note: Although this specific question has to do with the 32-bit ARM SAM3X8E Cortex M3 series, it is really a generic question that should be applicable to all microcontrollers, and therefore answerable by anyone who has significant experience with any MCU.

So the ARM SAM3X8E appears to only have 512KB ROM (that is, memory for holding flashed binaries), and 96KB RAM (that is, memory for running those flashed binaries). Hence if I have a binary, say, my-realtime-app.elf, that's 400KB and only consumes, say, 60KB (max) at runtime, it will happily store and run on this MCU.

I'm wondering if there is any way to "attach" (whatever that means) additional ROM/RAM storage to an MCU to overcome these limitations, and why this is or isn't possible to do.

For instance, say that my-realtime-app.elf undergoes extensive refactoring and starts doing all sorts of new computations and has new features, etc., and now is 12MB in size (the binary itself), and also now requires 15MB of RAM at runtime. This binary can no longer "fit"/run on the MCU, at least not without some kind of assistance. I'm wondering if I could somehow attach both additional ROM and RAM to the MCU, so as to give it more horsepower. If this isn't possible to do (for either scenario, ROM and RAM alike), I'd like to know why. And if it is possible, I'm interested in how.

I have to believe this is possible to do, but not sure about the approach/implementation. Also, I would imagine that the bit architecture of the MCU likely limits the size of the attached storage. For instance, this ARM MCU is 32-bit, which means it is only addressable up to 4GB. So it would not be able to handle binaries or runtime memory requirements about 4GB, etc.


texts: Range must be bounded by constant expressions - Verilog

texts:
How can I write in Verilog the following lines of code :

SF_D <= RAW1_i[(127 - (8*bytes_cnt)) : (124 - (8*bytes_cnt))];
SF_D <= RAW1_i[((8*bytes_cnt)-1) : ((8*bytes_cnt)-4)];

It gives me an error saying Range must be bounded by constant expressions.
bytes_cnt is changing value, is a counter, so I guess this is the problem. With constant value it works, with dynamic it doesn't. How can I make it work?


texts:
I'm in the market for an oscilloscope.  My previous approach was to get a used Tektronix on eBay.  There are plenty of good ones - even 100MHz 4 channel digital scopes for about $1100.  However, I started looking at Rigol - specifically the DS1102D.  It's two channel, 100MHz BW and it has a 16 channel logic analyzer as well as USB interface and color screen.  I know better than to just compare bullet points because Tektronix is a very well respected brand and Rigol as far as I can tell is of Chinese design and manufacture.  Has anyone used it?  Are there any gotchas?  Anything I should watch out for?

Update

I'm liking the answers so far and I just realized Rigol is the scope that had the bandwidth hack, so I'll extend the question to include the BW hack - who has used it and how did it treat you? And has anyone tried it on anything other than the DS1052E?


texts: Optoisolator always on on the high-voltage side

texts:
I am building a simplified version of this circuit:

As far as I can tell, it is a pretty standard design. The load will be a dumb resistive heater (this is a sous vide project).

For now, the optoisolator labelled 3042 is connected to the controller, and I have code which flips the LED on and off when I manually send a command to the controller. The triac and a load are also connected. The second optoisolator and the thermometer are not yet connected. There is a mistake somewhere, because the load does not turn on.

I measured the circuit, and found that the optoisolator has 230 volts on its output, no matter what signal it receives, i.e. both pins 4 and 6 are always 230 volts. I think that the low-voltage side works, because the LED labelled "cooking" goes on and off when it is supposed to. I wonder if the constant high voltage means that the optoisolator is broken, or is it more likely that my problem comes from some wiring mistake?

So, my question: Is there a situation in which a correctly working optoisolator can be always turned on, no matter what signal arrives at its LED?


texts: I am looking at something like this LVD 12V and am confused as to the purpose of the two negative terminals. On the BATT side I will have the + coming from the + side of the battery and the - going to a ground (this is the test for the voltage supply). On the LOAD side I will have the + side going to a light that is already grounded. When the switch is allowing current due to the voltage being above 10.7V it should pass that down to the LOAD. So why is there a second - terminal on the LVD?


texts: EEPROM 25LC1024 issue with PIC32MX OLIMEX board

texts:
I am trying to read the status register for the EEPROM following the instructions in this Application Note. I wanted to have the opinion of the community on the signals I am getting. They don't seem normal to me.

http://ww1.microchip.com/downloads/en/AppNotes/01073A.pdf

Wiring Diagram: I am using the exact same pinout recommended in the Application Note.

When I read MISO, I get a strange behavior.

MOSI and CS Signals:

I get the MOSI signal as expected on rising edge.

I setup the clock to tick @1MHz

SPI Initialization code, and running code in my main.c. (from eewiki, adapted to my needs)

#define eepromCS LATBbits.LATB15
void initSPI(void)
{
// Add GPIO config on pin RB15
eepromCS = 1; //GND

IEC0bits.SPI1EIE = 0;
IEC0bits.SPI1RXIE = 0;
IEC0bits.SPI1TXIE = 0;

SPI2CONbits.ON = 0;

SPI2BUF = 0;

SPI2BRG = 0; // 1MHZ

SPI2STATbits.SPIROV = 0;

/* SPI2CON Settings */
SPI2CONbits.FRMEN = 0;
SPI2CONbits.SIDL = 0;
SPI2CONbits.DISSDO = 0;

// 8 bits !
SPI2CONbits.MODE16 = 0;
SPI2CONbits.MODE32 = 0;

SPI2CONbits.CKP = 0; // Active state is high
SPI2CONbits.CKE = 0; // sampling from idle to active
SPI2CONbits.SSEN = 0;
SPI2CONbits.MSTEN = 1;
SPI2CONbits.SMP = 0; // sample during transmission

SPI2CONbits.ON = 1;
}

int main(void)
{
TRISBbits.TRISB15 = 0;
CSEEPROM = 1;

initSPI(); //EEPROM as a slave
unsigned char status;
unsigned char tmp;

//First READ
while (!SPI2STATbits.SPITBE);
eepromCS = 0;
SPI2BUF = 0x05;
while (!SPI2STATbits.SPIRBF);
status = SPI2BUF;
SPI2BUF = 0;
while (!SPI2STATbits.SPIRBF);
status = SPI2BUF;
eepromCS = 1;
write_char(status);

//Enable write LATCH
while (!SPI2STATbits.SPITBE);
eepromCS = 0;
SPI2BUF = 0x06;
while (!SPI2STATbits.SPIRBF);
tmp = SPI2BUF;
eepromCS = 1;

//Read Status register
while (!SPI2STATbits.SPITBE);
eepromCS = 0;
SPI2BUF = 0x05;
while (!SPI2STATbits.SPIRBF);
status = SPI2BUF;
SPI2BUF = 0;
while (!SPI2STATbits.SPIRBF);
status = SPI2BUF;
eepromCS = 1;
//write_char(status);

while (42);
return 0;
}

I did screenshots only for the last two operations (write latch enable, and read from status register). I have exactly the same signals when I read the status register before I send the write latch command.

I am using PIC32MX Olimex prototyping board, Below the protoboard documentation and EEPROM datasheet.

https://www.olimex.com/Products/PIC/Proto/PIC-32MX/resources/PIC-32MX.pdf
http://ww1.microchip.com/downloads/en/DeviceDoc/22064B.pdf

As usual the devil is in the details, it would be great if I could have a new look on my issue. Maybe I missed something.

Thank you for your help !

PS: increasing the baud to match 20MHz makes the signal flat but doesn't solve my issue.


texts: my question is regarding if the breakaway points exist or not. Do they only exist if 2 poles or 2 zeros are next to each other? Example if their are poles at -1 and -2 the breakaway point would be at -1.5? But if there was a pole at -1 and a zero at -2 then the breakaway point wouldn't exist? Is this correct? And if so, are they any other cases in which a breakaway point would or would not exist? Thank you.


texts: Can you have different clocks working at different intervals to operate a flip flop?

texts:
Is it possible to have two clock signals driving a JK toggling flip flop, in which both signals are connected by a XOr gate so that the flip flop only works on either edge of either clock? If possible, then there are also two sequences for how the clock inputs will go. Assume that the clock is positive edge triggered.

For Sequence A, Phase 1 is when the clock is driven to 0 by the two low inputs. In Phase 2, the clock is driven 1 by Input 1, after which a desired flip flop output is obtained. Afterwards, in Phase 3, the clock goes back to 0 when the input combination is "11" due to the XOr gate, where the Q output will stay the same. In Phase 4, now the combination is "01" after "11", the clock is back on. Despite this, I wish to keep the output as obtained in Phases 2 and 3.

On the other hand, for Sequence B, Input 2 going high first in Phase 2 will generate a desired Q output, which is different than the one obtained in the first sequence. Similarily as in the first sequence, "11" combination will turn the clock off due to the XOr Gate. Finally, at "10" I wish to keep the same Q output as the 2nd and 3rd Phases.

The Output "Q" is supposed to be like the following, assuming that the flip flop is initially at RESET:

It might be confusing, but is any of this possible? Thank you.


texts: Can the FlexIO module in NXP be used as I2C?

texts:
I have this S32K142 microcontroller. Unfortunately, it has only one I2C interface which I have already used.
I require another I2C interface for a different light sensor application - light sensor.
I read this Flex IQ note which mentions that the Flex IO pins can be used as an I2C module independently.
So, I read the reference manual and found the ports which will support FLEX IO and found the below :

I found that the ports PTD2 and PTD3 ports would support Flex IO. So, can I connect these 2 pins (PTD2 and PTD3) to an I2C communication device? Please confirm.


texts: How to make desired waveforms by AD5668?

texts: In another thread I asked about making sawtooth wave form via harmonics ( Here ) and someone suggested using AD5668 (octal DAC ). I looked at its datasheet but couldn't understand how it can make a wave form. Can any one help me by making a suggestion/tutorial or something?


texts:
I'm looking to interface a Seeedstudio Bluetooth Bee with an Android phone for a project, and I want to get the Arduino code down pat.

Specifically, I want to be able to set the time over Bluetooth (which will then interface to a RTC module), then receive RFID strings over the Bluetooth module.

There is a side issue, and thats whether all my NewSoftSerial stuff will play nicely - an exercise for me later, once I have the Bluetooth working.

The code set out by Seeedstudio is helpful, but not complete enough to explain to me. I have a moderate knowledge of Bluetooth, but I'm not afraid to ask questions. Hopefully, I can get the Bluetooth side of things to play "nice" so I can concentrate on the NewSoftSerial issue.

Here is some of the code I'm using to initialise the Bluetooth Bee, and I'm hoping I can then pair the Bee with the phone, and transfer data using the serial profile.

Serial.print(“\r\n+STWMOD=1\r\n”);

Serial.print(“\r\n+STNA=modem”);

Serial.print(“\r\n+RTPIN=0000\r\n”);

delay(2000);

Serial.print(“\r\n+INQ=1\r\n”);

delay(2000);

Serial.print(“\r\n+STBD=9600″);

I guess, what I'm asking for is the process of connection - on Seeedstudios forum once the +INQ=1 command is issued, then the phone (or computer) can find the Bee. As you can see, I have an RTPIN of "0000" (secure, I know...) so inputing that into the phone will pair the phone and Bee? Or am I way off the mark?

Many thanks.

Shane.


texts:
I'm using LatticeXP2 family FPGA. DVI-D Single link operating at 720p is connected to FPGA. I somehow need to read RGB and XY coordinates of pixels. I know I need TMDS decoder, but I'm not sure how to write that and some sort of clock sync in VHDL/Verilog.

I know there are dedicated chips designed to do that, but I can't afford extra cost to the board.


texts: Can a AMS1117 fixed voltage regulator be used in a reverse biased way?

texts:
I was looking at a breadboard power module (link). This board has two inputs: a DC plug (7-12V advised) and a USB mini (5V). Using either of those two inputs, the board provides two voltages (3.3V and 5V) using fixed AMS1117 voltage regulators. So far, so good.

However, looking at the module, and after some path testing with a multimeter, it seems that something strange is happening. When using the USB as input to power the module, the 3V3 regulator gets its input through the 5V regulator. But in a strange reversed way. (The voltage at the input pins of both AMS1117's is around 4.5V.)

The schematic of the board is this (excluding the output headers and switches):

Using either DC or USB as input power, both 5V and 3V3 rails are working. But I suspect that the 3V3 rail using USB as input power, might not be a proper supply.

Am I correct in assuming that this reversed use of the 5V regulator to power the 3V3 regulator is less than desirable? Or am I missing something?


texts: LEDs + Constant Current Driver - Discharging the Circuit

texts:
I have a project where I made a series of high power Osram OSLON blue leds using custom boards on aluminium PCB. I just put 16 LEDs in series and joined them to an appropriate constant current supply. They all light up well and the currrent/voltages all seems to what I expected when measured. However, when turned off the LEDs have a significant glow and the supply has a significant voltage across the circuit.

LEDS: https://uk.rs-online.com/web/p/visible-leds/1751980/

CC Supply: https://uk.rs-online.com/web/p/products/7911118

Do I need to improve my circuit so that it safely discharges?
I take it that this would mean putting a resistor somewhere?

Thanks for your help!


texts: Setting the minimum value of a potentiometer using a resistor

texts:
I'm currently studying for the amateur radio exam and I've come across a question which, in theory, should be simple but it entirely eludes me.

In short:

If the potentiometer is 10KOhm what value should R3 be for Vout to be 1% of Vin at the POTs minimum setting.

(R1 and R2 are supplementing a POT to help me think it through)

I understand the potential divider equation, but it's the ratio that confuses me. Or more precisely how to apply that ratio to let R3 be of a sufficient value to make sure "minimum".

So my thinking started as follows:

According to my reading if R2 is an order of magnitude higher than R1, Vin = Vout. OK great, adding to R3 shouldn't make a difference.

Conversely if R2 is smaller, the voltage will be smaller - Great

At minimum, the POT is effectively 10K. which means Vout = VIn. I presumed R1 would be 10K, whilst R2 would be 10K - I'm guessing this is wrong.

I tried flipping it over, but the same problem.

What's my glaring mistake - is there somewhere that'll teach me to fish as it were

[edit] Big thanks to everyone. I'll leave this question intact as the answers are correct. However, my question is in the comments (oops)


texts: I've gotten an oscilloscope! How do I take care of it?

texts:
I'm happy to say that I've gotten my first ever oscilloscope!! I want to make sure that I take good care of this equipment.

But I'm afraid that while I'm new to oscilloscopes, I'm new to taking care of them.

What are some DOs and DON'Ts of operating digital oscilloscopes, and good practices to keep them in running order?


texts: Multimeter reads negative even without leads

texts:
I have a cheap multimeter that used to work fine but now it has negative readings -- even when the leads aren't connected. I changed the battery, looked for a blown fuse but no luck.

Any idea what's going on? Is it toast? It's a GB Instruments GDT-11.

(Picture added)


texts:
as we all know lm 324 consist 4 op-amp now the datasheet says current limitation like 40mA. Now I want to ask that whether 40mA for each op-amp or the sum of all 4 op-amp

Link to the datasheet here.


texts: Determining the radius/length of an IMU on a rotating stick

texts:
So I can't really wrap my head around this problem.
I have an Inertial Measurement Unit (IMU consisting of an accelerometer and a gyroscope) mounted to a stick which can rotate from a fixed position in the ground with a motor (see picture).
The length of the stick is unknown and through rotations of the motor (the motor has an encoder to measure the angle and speed and acceleration) I want to determine the distance from the rotational joint to the IMU.

I could just make a sufficient arc and calculate with the angle the radius, but that is error prone if you have a bad IMU due to double integration to get the distance, right?

Is there a way by measuring the gravity vectors at certain static positions and calculating a radial vector through that? Would it help if there is also an IMU at the bottom of the stick at the rotational joint?

Thank you very much for your help!


texts:
I started a project with my students to build a full open source PIC IDE in windows. My first try was to port Piklab to windows but it is dependent on Qt and KDE. We decide then to use Eclipse CDT as IDE, SDCC as compiler and GPUtils as linker and assembler. We managed to make the compiler-chain plugin so we can build the whole project in eclipse and generate the binary.

The problem now is how to use eclipse to program the PIC (we are targeting specifically on ICD2 because it is what we have available on our lab). Does anyone knows an open-source programmer that can run on command line on windows?

Thanks


texts: Single Stage Amplifier CMOS - Biasing Issues

texts:
So this is kind of vague question. I'm wondering what the approach to biasing MOSFETs in saturation is.

For the following circuit, I really have no specifications  - I'm just trying to play around with it and get the highest gain I can.

Here's my usual approach for biasing:

Set supply voltage (Vdd) to some reasonable value like 1.8V or 1.5V
Have all MOSFETs ratios at default (I'm literally just trying to get them into saturation first)
Start off by trying to bias the PMOS current source - one transistor at a time
To do so, I would adjust the gate voltage for those PMOS devices starting off at something like 1V. But the issue arises that my drain source voltage for that device would be far too low and I would never be able to get it into saturation.

Again, I'm not looking for an exact answer here - just some guidance into what sort of approaches/mindset you have when biasing. Majority of the textbooks I've seen really seem to just gloss over biasing and I haven't actually seen a concrete trial/error example for it. They just assume it's always biased properly.


texts: how to design a circuit that gives high output between input transition and next rising edge of CLK

texts:
I'm trying to understand how can one build a circuit that does the following functionality:

I see according to the output that I should have a D-FF, that works at Falling-Edge mode, so I need to add an inverter to the CLK. how can I continue from here? are there basic rules that I can follow in order to know what should I add more?
Note: my intention is to use D-FF in the circuit. I have knowledge in designing mealy machines and aware of the procedure. but here the states aren't quiet clear in order to make mealy machine design. I would like to know if this could be a successful approach for the problem.
the reason I thought about mealy machine is because the output change is dependent of the input change.


texts: I am trying to write a program that measures the frequency of a signal. So I think a way to do it is to set the timer0 interrupt at every rising edge then record that value and subtract two successive values that would give the period. Can anyone tell me if this would work and help me write a code I am a beginner at PIC programming. I am using PIC16f17889


texts: Eagle ground plane showing as all black in Gerbv's Export (as PDF) but not its display

texts:
When I include a ground plane in a copper layer and then run Cam Processor in Eagle, the gerbers look fine in Gerbv's display.  But when Gerbv Exports the visible layers as PDF, the ground plane area appears all black (or whatever layer color), with the exception of a drill layer at the top of the layer stack.  Can anyone tell me why the plane's polygonal outline appears as monochromatic and how to work around it?
Or can someone suggest a preferred path to the printer w 1:1 scale from the Eagle gerbers that they'd recommend other than Gerbv?  Cheers.


texts: When is a system's frequency response symmetric?

texts:
When is the frequency response of an LTI system symmetric, i.e. which property does it need to satisfy? Does it have to do with the system being causal (I believe this means that h(n) = 0 for n < 0)? If so, why?

Thanks!


texts: Does a phase-controlled dimming degrade the lifetime of filament or heater element?

texts: In numerous sources I've heard that it's "easier" for a heater if you don't switch fast current transients on it. How come? Why does the wire degrade?


texts:
I have a thermostat (think pt100)

This should be connected to a heating solution. I want to fake the temperature from thermostat, so I was thinking to buy a resistor with the ohms at the temperature I want to fake.

Would it be right to just replace this resistor with the new one with a fixed ohm?

The reason for this is so i can controll when the heating system should start/stop based on more options than only the temperature of one room (my plan is to ha a nc-no relay to switch between two resistors, one with "warm enought" resistance and an other with "not warm enought" resistance


texts: Why do I need to wait a few moments before sending serial data on my AVR?

texts:
I have an AVR (ATMega644) connected to a Raspberry PI via serial connection. The AVR is powered with 5V and the AVR=>RPI Tx line is using a 1k8/3k3 voltage divider to get a 3v3 level.

If the 10ms wait (XXX in the code) is not present (according to the data sheet I do not have to wait at all) I receive this nonsense (python repr() of the received data):

 '\x00\xaa\x8a\x8a\xea\n'
 '\xe9\xf5%\xc5E\xd5\xa4\xfcBYE WORLD\r\n'

When the 10ms delay is there I receive this:

'\x00HELLO WORLD\r\n'
'BYE WORLD\r\n'

This is pretty much fine. I'd like to know why there's a \0 before the very first actual data byte ('H') though. I never send one for sure!

However, my main question is why the delay between initializing and sending data is necessary.

Notes: My F_CPU value is correct and so are the fuses. I also tried using a lower baudrate (4800) and a different chip.

This is the code I'm using:

#include <avr/interrupt.h>
#include <util/delay.h>
#include <util/setbaud.h>

inline void uart_putc(char c)
{
    loop_until_bit_is_set(UCSR0A, UDRE0);
    UDR0 = c;
}

inline void uart_puts(const char *s)
{
    while (*s) {
        uart_putc(*s++);
    }
}

int main()
{
    // we don't need/use any interrupts
    cli();

    // -DF_CPU=18432000L -DBAUD=19200 used when compiling
    UBRR0H = UBRRH_VALUE;
    UBRR0L = UBRRL_VALUE;
    // 8 data bits
    UCSR0C |= (1 << UCSZ00) | (1 << UCSZ01);
    // enable transmitter
    UCSR0B |= (1 << TXEN0);

    _delay_ms(10);  // XXX
    uart_puts("HELLO WORLD\r\n");
    _delay_ms(250);
    uart_puts("BYE WORLD\r\n");

    // do nothing
    while (1)
        ;

    return 0;
}


texts: Basic Embedded Firmware testing essentials and Software Test plan

texts:
I am trying to make an embedded product, but I'm new to firmware testing and want to make sure I don't miss anything. What are the things that need to be checked for its firmware performance?

Proper watchdog timer is one thing to be checked. Flash/RAM usage could be another. What else needs to be checked for making sure the product has "good" firmware?

I mostly deal with PICs and C compilers.


texts:
LT1510 is a battery charger IC that can be configured to charge any kind of battery pack, I am interrested about the circuit given in the application note referenced AN68F page 24/36. The IC is used a Li-Ion battery charger. I want to understand the circuit around the OP AMP U2, and how U2 reset U3 (circled in red).

My first question, what is the role of C9, a capacitor that is connected between the inverting and non-inverting pin of U2 ?

From the application note, I understood that U2 takes effect in the final stage of charging (Constant voltage charging). It says:

  When the LT1510 is charging, U2 compares the voltage across the LT1510 internal 0.2ohm sense resistor to the voltage across R7. When the voltage across the sense resistor is lower than the voltage across R7 (or, alternatively, when the
  charge current drops below 75mA), U2’s output voltage drops. When U2’s output voltage drops, U2 latches at low state via CR5. U2’s output is connected to the RESET pin of U3.

What is the voltage across R7 ? I am not sure, but I think, first R7 with R8 and R9 make a voltge divider of VBAT+VRsense (VBAT is the battery voltage and VRsense is the voltage across the internal sense resistor).
How does U2 compares between VRsens and VR7 ? (the inverting input of U2 is connected to the battery pack and the non-inverting input is connected to a voltage divider )
U2 output is connected to VIN through R10, so how does this output latches at low state via the diode CR5?


texts: Is this arduino motor driving circuit correct?

texts:
I got an Arduino Pro Micro and some parts to play with. I want to control a little 5v motor from an external power supply by using the Arduino to trigger a transistor. Like this:

Is that at all correct? Will it work? I want to experiment but I don't want to break my new toy in the process. The transistor I am using is an NPN, 2N3904.


texts: How to increase the output power for this audio amplifier?

texts:
I have created this simple single stage, transistor audio amplifier using voltage divider bias.

For testing, the source of input signal was audio from laptop and the output was from a 4 ohm, 0.25 watt speaker. When I applied the input signal, I could hear only very very minute sound in the output. When I connected the speaker directly to the source, it produced good audible sound. Why is this amplifier not amplifying then? Where lies the mistake. I've also went through the datasheet of the transistor and suitable chosen the collector current value of 5 milli-ampere and calculated the resistors appropriately. Please suggest some corrections.


texts: Why has a LUT6 based SRL only 32 entries but not 64?

texts:
Xilinx FPGAs are capable of using LUTs as memory elements. The can be used as ROM, RAM and Shift Register (SRL).

New Xilinx devices use 6-input LUTs, which gives 64x1 bit for RAMs/ROMs, but only 32 bit for SRLs.

Why are SRLs restricted to 2^5 bits?

I'm not aware of any explanation in the official docs.


texts: why does this approach neglect the output resistance of the bjt in calculating gain?

texts:
This is the question that I would like to ask about. My question is with regards to finding Vc for question 3. This is the memo for the question:

However, I have a problem with regard to how they find Vc. Surely, if Vc is equal to Vcc- Rc(ic) then that is regarding the circuit as DC and ignoring the effect of the output resistance of the bjt, in which case it would be equal to Vcc- Rc|| Ro *ic?
Ro would be equal to Va/ic = 80/1.5*10^-3 = 53kohm
Or do you think that for question 3, without stating it, that it was assumed that Va = 0?


texts: What's the most Important thing to look on datasheet when Replacing a Transistor with another one?

texts: I'm trying to replace a transistor but I don't know if the transistor that I'm trying to replace is going to work. Can someone help me determine which parameters to look for before replacing?


texts:
This is the original circuit, we assume Vdo=0.7V, this is for when either of the diodes are on.

We know both diodes cannot both be off because then no current would flow in the circuit. I become stumped when only one of the diodes is on, how do I find Vo?


texts: Capacitor sizing for 120VAC blackout / brownout power backup

texts:
UPDATED (more clarification)
Essentially what I am trying to do could be called "SuperCap Based UPS".
In other words, to replace the battery in a DC to AC Inverter circuit with a Super Capacitor to provide temporary 120V AC power to an appliance that draws about 0.08 amps or about 10 watts @ 120VAC.

Will I get more runtime by charging up a large 1 Farad Cap at 12V or would it be better to store 120V in a Cap that is capable of this voltage, and instead have the inverter convert from 120VDC to 120VAC?

I'm trying to provide as much run time to the end device (which obv. uses 120VAC).

So what's the most efficient way to get the most runtime at 120VAC from a capacitor powered inverter solution?


texts:
In regards to the design of toridal transformers is there any specific book that can be referred to?

Can toroidal transformers be built for high power application? I mean can v built a 25 KVA , 11KV-433V toroidal transformer.

Are toroidal transformers limited to RF applications only?

These are a few questions running on my mind, hoping it would be answered soon.


texts: Shielding mains transformer to decrease interwinding capacitance

texts:
Has someone tried to shield mains transformers in order to decrease the interwinding capacitance?

I have a transformer (toroid, power is about 5 VA,) and interwinding capacitance is a problem.

As I understand, I should make a shield (use a foil, maybe) and then connect it to somewhere.

Where should I connect the shield?

My output circuit looks like this:


texts: ATX PSU 3.3V output dead short with ground

texts: On an ATX PSU, 3.3V output was dead short with ground (checked with DMM),once i powered ON the PSU  3.3V output was providing the rated output (3.3V) how this is possible?


texts: I2C bus switches/multiplexer vs analog switch/multiplexer

texts:
I'm refactoring a board that needs to switch the communication between an I2C master (M1) and two identical I2C slaves (S1 & S2 with same address).

The first design of this board was using a TCA9545A. This is a nice IC but, like many other I2C switches, it is controlled through the I2C bus. In my application this is an unwanted feature because the only I2C master I can control is not M1 and if I connect it to the same I2C bus, I'm going to create a multi-master topology that's not accepted from S1 and S2 devices.

My thought was to replace the TCA9545A with another I2C switch, which is NOT controlled through I2C (i.e. through a digital controller). But I have to admit that it's not an easy task, because after having searched in all catalogs of main IC companies, I haven't found a single component matching such features.

The other option was to use a standard bidirectional switch/mux like ADG1636 or similar. Is there another option? Is this a good replacement to fulfill my requirements?

--- Schematics update ----


texts: hello every one i need ask about frequency response i have an old question of our professor exam in few year, and i try to solve this question many time but i can't so please if any one have idea about it,i know that in LOW the externaly capcitor is effect and at high the internail capacitor is effect C_miller in and C_miller out,but how i can show the frequency response without poles and zero and how i know how many zeroes and poles in figure?


texts:
I am using a Raspberry Pi3 to design a system for automation, monitoring, navigation and general management of a boat.

I'll be using quite a lot of I2C sensors (but well under the maximum which I believe is 127).

I had planned to arrange them in a loop around the boat, however I've read from various sources that the maximum cable run is pretty short (around 1m seems to be a common number).

A couple of options I've looked at for extending the range are using a P82B96 buffer, or a CAN Bus network. The P82B96 looks fairly straightforward?

I haven't done this or even looked into it before, so would like to know if one of the suggestions I've made is considered 'best practice', or if there's something I've not heard of.

Another consideration is what standard interconnects a system might have. In a harsh marine environment they must be robust and IP67/IP68 in places. I will need panel mount, through bulkhead, plugs (M&F), inline connectors and cable and blanking plugs to prevent accidental ingress.


texts:
I have a trouble solving an assignment in the online course I'm following. The assignment asks some questions with respect to this circuit:

simulate this circuit – Schematic created using CircuitLab

where the current source puts out an impulse of area \$A = \frac{2}{\pi}\$ Coulomb at time \$t=9s\$
The differential equation for this circuit is given already solved and it's

$$\frac{d^2i_L(t)}{dt^2} + \frac{1}{LC}i_L(t) = \frac{A}{LC}\delta(t - 9.0)$$

I've already answered some questions (like \$i_L\$ and \$v_C\$ just before the impulse and \$i_L\$ just after the impulse) and the answers are correct.
In particular, the system accepted my \$-54.9768V\$ as the answer for the \$v_C\$ just before the impulse.

But for the \$v_C\$ just after the impulse the system doesn't accept my answer which is (rounded to four decimal places) \$0.0318V\$. I got this answer using two ways (both times the same result).

The first is: supposing that for a current impulse the capacitor should behave like a short circuit, all the current should go through the capacitor and deposit all the charge on it. The deposited charge should add to the voltage already on the capacitor an increment \$\Delta V = \frac{A}{C}\$.

The second way is: find the response to a current pulse of width \$\Delta t\$ and height \$\frac{A}{\Delta t}\$, which happens at the \$t=9\$. From this
response we find then \$v_C\$ at time \$t=9 + \Delta t\$ and then we find limit of this value when \$\Delta t \to 0\$. The result is the \$v_C\$ just after the impulse.

So, as mentioned above, both ways give me the same answer which seems to be wrong and I don't see where is my error. Please, help me with this.

Thanks


texts: Using 1000x WS2811 leds and 5v 60amp Power supply. When do I need to re-inject power?

texts:
I've been reading a lot about the WS2811 LEDs and how to properly set them up. I've purchased a few thousand of them off of Ebay for various projects because they're so easy to use. So far I've only used a series of 100.

I've seen a lot about the need to re-inject power at certain points throughout the series. Most of these use-cases were using power supplies with low amps.

Forgive me if this is a horribly naive question but if I have a 5v 60 amp power supply will I still need to re-inject to account for a voltage drop or will the higher amperage help maintain voltage?

EDIT:
Most of what I've read says re-injection will be required every 60 LEDs or so. I'm at 300 and I'm not seeing any noticeable difference at the end of the series?


texts:
What circuit, with a single input and a single output, has a transfer function that looks like this:
$$H(s)=\frac{\omega_n^2}{s^2+2\omega_n \zeta s+\omega_n^2}$$ (second order system)?


texts: Should I remove terminating resistors in ethernet TAP?

texts:
I would like to design Ethernet TAP, with PHY, that I can connect to FPGA via RGMII interface. I know, that I could do this like there, but I would like to be able to analyze low level data in MAC. Picture below shows more or less what I would like to do:

My device will be between two connected devices. It will listen to their traffic, without interrupting it.
There are a lot of different PHY chips, and different circuits between chip and RJ45 connector, like in this question, but commonly there are 75 ohms terminating resistors on the network side, and 50 ohms terminating resistors on the chip side.
My question is – should I remove this 75 or 50 ohms resistors in this case?


texts: The leads of my 3-phase motor are incorrectly labeled. How do I determine the correct labels?

texts:
I connected my new-in-box 3-phase motor to my new-in-box VFD, following the instructions in both manuals and the wiring diagram on the name plate (low voltage configuration).

With the power off, the motor rotates freely and easily by hand.  At 5Hz on the VFD, the motor runs in a rough, bumpy manner and I can reverse the rotation of the shaft simply by grabbing it and spinning it the other way by hand (which it then maintains indefinitely).  At 10Hz, the over-current protection in the VFD is triggered.

I verified that all 3 terminals of the VFD are providing voltage.

I suspected that one of the motor coils might be burned out or shorted, but a simple continuity test shows that none of the leads are shorted to ground, and there is continuity between each pair of leads as you'd expect from this diagram.

My reasoning is as follows:

If there was a short, the over-current protection would happen regardless of motor speed
If there was a dead winding, there would be no continuity there
Some of the leads must be improperly labeled, causing the motor to fight itself

So, how can I work out the proper labelling of the leads?


texts: Some questions about a terminal block voltage and maximum ratings

texts:
A screw terminal distribution block is shown below:

A three phase motor driver manual specifies "connector voltage" and current for mains voltage connections for the motor. They specify current as 30A and voltage as 1000V.

Imagine I use a screw terminal block as a connector as following:

simulate this circuit – Schematic created using CircuitLab

1-) What does 1000V voltage rating mean for a connector or a terminal block? Is that something to do with isolation break down voltage between consequent terminals?

2-) The rms voltage difference between R and S is 230*sqrt(3) = 400V rms. This means 560V amplitude and this is half the 1kV requirement. Can 1000V requirement be about transients?

3-) What if I connect R S and T further apart for example every three terminals(not adjacent), would I increase isolation voltage?


texts: Art Of Electronics - How does the phasor diagram explain away 3db verses 6db confusion

texts:
simulate this circuit – Schematic created using CircuitLab

Hi,

In the follwoing two images, I am having a problem seeing the confusion the author is talking about and more importantly how he uses the phasor diagram in figure 1.61 to clear this confusion up?  He describes the confusion the reader is likely to see in the second image.

But first, Note the last line in the first image, "Lets take an example, namely the fact that.."

He is talking about an RC filter and the 3db attenuation you get at f = 1/(2 * pi * R * C).

In the second image, he states that if you change the capacitor to a resistor equal to R, you get 6db attenuation.  R / (R + R) = 50%.  I see that, simple voltage divider.

He says that if you go back to the origional RC circuit at frequency f = 1/(2 * pi * R * C), the capicitors impediance equals R and a confused person, like me, would expect to see 6db attenuation.  He descibes figure 1.61 and the reactive parts of C as an explanation to why one sees 3db attenuation instead of 6db attenuation.  Note, he says that at f = 1/(2 * pi * R * C) the impediance of the capacitor equals R.

Questions:
   1) How does figure 1.61 show this clearly?  I don't see its explanation.

2) In the text of the second image, the author says the input voltage (applied across the series RC  pair) is proportional to the hypotnuse.  Why is this so, the input is from en external source Vin (wall outlet)?

3) He then says that the output voltage (across R only) is proportional to the length of the R leg of the triangle.  Again, I'm not seeing how the phasor diagram explains all this.

Thanks for the great help.  I've never been this far in this book as yet and think the other chapters are home free. :)


texts:
I would like to somehow plug an extra button to my computer that when pressed would execute some shell script.

Backstory: I'm a programmer and I very much wish I had a big red button to commence the deployment of whatever it is I'm working on. This button when pressed would trigger the execution of some script on my computer and do nothing until released and pressed again. Also I would prefer if it connected through USB. I imagine this one button will be simple to hook up and be enough for a while, but I'd also like a solution that would work for multiple (4-16) buttons for example (on a nice wooden control panel).

When answering, please keep in mind that I don't know much about electronics.


texts:
How to read 8-bit digital signal through an Agilent DSO? I just want to use the oscilloscope as a 8-bit ADC,so how to read the 8-bit digital signal from the DSO?
Please help me, thank you very much!

It's DSO90254A, I just want to use the 8-bit digitalized binary signal, for example, 10100111.


texts: Small amplifier to big speaker - Will it end in tears?

texts:
I was given a pair of vintage (brand new unopened) speakers which I am hoping to use with a wall mounted remote controlled amplifier as part of my home cinema. Here are the specs.

Speakers: Wharfedale 8.1s rated at a nominal impedance of 6 Ohms and power handling of 100 Watts
Amplifier: ADASTRA WA-210 wall mount digital amplifier 8 Ohms 2 x 10W

I am not intending to wind the volume up but would like a decent level of sound. What sort of performance should I expect?