texts:
I want to use a N Mosfet for switching a device from a microcontroller (5V current and 5V signal), and a P Mosfet for giving a signal to the same microcontroller (5V signal , 12V input). (Device current draw in the order of few 100s of milliamps.

I'm having trouble in finding the specs that make the components suitable for those specific tasks. I had the following problems.

Problem 1 - With N Mosfet, this layout won't work because there is a big drop in the mosfet, and the load gets something like 2.8V.

simulate this circuit – Schematic created using CircuitLab

If I give it instead 12V, there is no longer a big drop, and it works like I intended.

Before I requested this particular component from an online seller, I tested in its simulator (MultiSIM BLUE) and even with a load of 1 Ohm, the voltage out is 4.78V.
I don't know if this is acceptable for a simulator or if I should complaint about it.

The particular Mosfet is this one.

http://eu.mouser.com/Search/ProductDetail.aspx?R=FQD7N10LTM

I solved this issue by connecting the load directly to 5V and it's ground to the mosfet and that way it works as I intended.

simulate this circuit

Anyway I would like to ask why does this happen, and how the input voltage makes a difference, and which mosfet I could buy that would solve this problem.

Problem 2 - With the P Mosfet, if I give it 5V in the source and I give it 0V in gate, it won't "open" or at least not fully, so I can't get 5V on the drain. If I use 12V instead it works as intended. Notice that I want to use the P Mosfet giving 12V in the gate to "close it" so it "passes" 5V but I'm not even in that phase, since I can't even make it work with 0V.

As for the N Mosfet, I tested the behaviour in simulator, and it worked as I intended.

This is the particular mosfet:

http://eu.mouser.com/Search/ProductDetail.aspx?R=FQB8P10TM

Now, if I do the same thing as I did for the N Mosfet, and change the load position in the circuit, the mosfet now conducts, but I only get 1.1V.
If I connect it to 12V, I get 7.70V.

So, basically, I want to work with Mosfets as logic gates but they just won't work with 5V as I intended.
My two final questions are:

How do I choose the two Mosfets for this tasks?
I the behaviour of the simulator?
Why the N Mosfet works ok I the other configuration?
If I complain to Mouser, will/should they give me replacements?

Notice that I'm talking about "Logic" but I think that I don't even have to use Logic Level Mosfets because I'm switching with the same voltage level for gate and input.
Anyway, the N Mosfet is Logic Level.

So, one more questions: is there a need of Logic Level Mosfet for some of these situations?

Post note: I talk throughout the text about using 12V for testing, it's just because that value is one that I happen to have around, and I noticed that it makes a difference for both of these mosfets.


texts: Measuring AC voltage (0.333vac max) using a 10 bit ADC on Atmel ATMEGA328

texts:
new to this so please be kind.

want to measure AC current in domestic supplies using an atmel ATMEGA328P chip wit the best resolution possible

I need to use the split core current transformer sensors I have which output 0.333vac for the sensed current they are rated to - http://www.magnelab.com/wp-content/uploads/2015/03/AC-Split-Core-Current-Sensor-SCT-0400_specsheet.pdf

I have a regulated 3.3v supply which runs the chip and the internal analogue reference is 1.1v.

I have tried creating a potential divider using the 3.3v supply and 100k and 560k resistors to give 0.5v and then connecting the ground of the CT to the 0.5v point and the output of the CT to the ADC (with 1.1v analogue reference).

My problems are

the resistors seem to have stopped working (am i using bad values?)
the samples are inconsistent, at the moment i am taking 100 consecutive samples using a for loop in the AVR code and then calculating RMS voltage by subtracting the 0.5v bias and doing standard rms calculation... should i be sampling at a particular frequency and if so does anyone know how i go about controlling this on the chip I'm using.

Kind regards,

James.

simulate this circuit – Schematic created using CircuitLab


texts: CB blew when trying to measure the current using multi meter. What went wrong?

texts:
I set my multimeter like this.

Plug the black lead to the short tab of NEMA5-15 receptacle first and the red lead to the long tab.

The moment I put the red lead in, there was a big spark. The circuit breaker was blown. And both of my lead is burned pretty bad like this

What did I do wrong? Can someone explain it to me? Is it because I plugged the black lead to hot line of the NEMA5-15?

Before doing like what I described, I had done another run with the lead mistakenly plugged in the meter like this

Everything seemed fine to me. And the meter displayed ~3.5A
Then I realized I plugged the lead in wrong post so I swap the red lead and accident happened.

Can someone please explain this phenomenon to me?


texts:
I'm building a multi channel power amp and I am having trouble with the power supply. I'm in Europe, so I've got 230V mains and I'm running into a transformer which brings it down to 60V.

The problem is that at no load, the fuses blows. As I've installed the circuit breaker, it gets tripped.

Am I screwing something up? Is it a problem of having no load?

Transformer datasheet (pdf)


texts: Resistance dependent pricing for resistors

texts:
Does anybody know of any reasons that the 560 Ohm resistor is so much cheaper than the other values? It does not appear to be a trend of price increasing or decreasing with resistance since there are resistors both above and below this value that are more expensive. This is not the only example of this line. Every now and then there will be a particular value that is half the price of all the others.

Mouser.ca screenshot, 2020-10-17


texts:
I am attempting to us a voltage shut off switch with some pre-existing hardware.
I do not understand transistors well enough yet and am looking for clarification.
I desire for V2 to be able to go to the output but also be able to shut it off.

Q1's part number is EMH1T2R and it has the two resistors internal.
When I turn on M1, Q1's base only comes down about 100mV.

What am I missing here to be able to shut Q1 completely off?

simulate this circuit – Schematic created using CircuitLab


texts: How to connect a 4D display to a beaglebone black?

texts:
I am fairly new to all this so sorry if this question is rather trivial.

I have a 4D Picasso Display (28PTU-Pi) and I want to connect it to my Beaglebone board. So plugged the usb cable into the board and the splash screen came up. But how do I connect it so that I can actually run programs on it like the tutorial?

On the homepage I could only find this, but that's for a Raspberry Pi and not Beaglebone.


texts: Calculating Capacitance / Rolloff Frequency for Across the Line RFI Supression

texts:
I’m in the process of restoring my first All American Five (AA5) tube radio – in this case, a GE Model 115 from the late 1940s.  As I’m getting ready to order replacement capacitors for it, one of them (.05uF, 600V rated) sits across the Live and Neutral mains lines for (I would assume) RFI suppression.  OK, I say – and I go about looking to order a suitable X Class safety capacitor.  .05uF is a bit more capacitance than seems usual for tube-based gear I’ve seen (usually it’s a .01uF) and it got me thinking: why the difference in value?  And more broadly, what exactly does an “across the line” capacitor really do.

My assumption is that it is there to form a low-pass filter, shunting RFI above the 60 Hz mains.  So I run a quick rolloff frequency calculation using 1/(2*piRC) where the load resistance of the tube filament chain is something akin to 480 Ohms (given that the radio draws about 30 watts on a 120V mains line).  To my surprise, the rolloff frequency at .05uF is about 6600 Hz (and at .01uF 33,000 Hz).  Much higher than I would have expected.  Granted that either is still way below RF interference – but I would have thought that the rolloff would have been much closer to 60 Hz (esp. in the “old days” when perhaps motors and other low-frequency noise generators were more of the problem trying to be avoided).

So, my question is: what I am missing, either in my calculations or in the design intent of the capacitance values?

EDIT: changed old-style microfarad "mF" references to modern "uF"


texts:
whats the name of the type of ribbon cable socket used in laptops? or what would I look under to find them on a site like farnell?

Its some thing like a D-Sub connect to system, except the plug is actually moulded onto the cabling at 90 degrees to it and the plug and socket are very low profile.
It is the connector on the left in the below pic


texts: USB short circuit on power - does it damage the PC?

texts:
I am building a circuit powered from a PC USB. Normally I put a diode in series with the input power to prevent damage from accidental reverse power being applied. However, over a long USB cable I want every millivolt I can get, so I am considering putting a diode across the power input lines to short any reverse voltage. Question being, if someone managed to connect the USB the wrong way round would it damage the PC or do we get a controlled closedown of the USB source power?

Suggestions, opinions, answers?
[Googling briefly, it seems opinion is divided]


texts: I have a micro-strip transmission line as shown in the figure which is incident by an external EM field. This field will induce some voltage and current on it. I want to measure the induced voltage and current. Induced voltage can be measured using a DSO across the transmission line and the ground plane. Can it be possible to measure the induced current? The frequency of induced EM field is in a range of 500MHz to 1GHz.


texts:
This is a follow on question from here: Simple Audio Amp for FPGA audio to PC in which I'm trying to get audio from an FPGA -> delta-sigma DAC -> op-amp -> Line Level.

Following the advice given in the above mentioned question, I've come up with this:

By explanation:

Left side of circuit connects to 3.3V output pin on the FPGA
The 3.3K and 4.7nf form a simple RC filter as part of the delta-sigma DAC
The opamp is half of an opa2314

I've connected the RHS to microphone input on my PC and it records quite well, however...

I'd prefer to connect this to line-in.  I've tried many different values for the two other resistors, including putting a 10K pot in for each, but can't seem to get enough gain for a line in signal.

Am I missing something, or am I simply hitting the limit of what this op-amp can do?


texts: Air conditioner sockets and mobile phone charging

texts: I want to know if/how my air conditioner and my phone charging works on the same power socket. i.e when I want to charge my phone I remove the air conditioner plug and use say my charger or my iron on the same socket. Is this OK? Any cause for worries? I have been doing this for a while now and everything seems fine. The power to my wall is 230 V a.c


texts:
______
A _____|      |________

         ______
B ______|      |_______

Which edge arrives first?

I have two digital pulses that arrive at almost the same time, and I need to determine which pulse arrived first.  I need to resolve to ~500ps, i.e. the pulses may arrive 500ps apart and I still need to be able to resolve which one came first. The pulses are the exact same width, they are wide (~10us) relative to the edge timing, and the period of the pulses is about 20ms.

Most of what I've come up with (anything flip-flop-based) doesn't work due to prop delays.

Since what I ultimately want to do is align the pulses, i.e. reduce the delta to 0, I thought about XORing the two pulses (theoretically producing an even shorter pulse the width of the delta) and then minimizing the width of the XOR'd pulse by adjusting the delay of one of the channels.  Unfortunately most of the pulse is eaten alive by the rise/fall times of most logic (even PECL is questionable), so it's hard to get a large enough signal to process (peak detect with a diode, R and C and minimize the resulting voltage).

Any other ideas?  I'm going to start looking at PLLs next, though I'd rather not if there's something simpler...


texts:
I am referring this document for measuring
insertion loss of the diode in SPST configuration initially. As mentioned in Pg.No 7 circuit and using BOM given
Expected Result

I simulated using LTSpice

Is my measurement correct, Since expected plot has y-axis as S21 (dB) (I am assuming output w.r.t input). I measured V(OUT,IN)/V(IN,VOUT). What is the right way to measure this parameter ?


texts: Can identical DC power supplies with common ground produce varying voltage on same circuit?

texts:
For large installations of 5V LEDs, this PixLite page suggests using "power injection" from supplemental power supplies.  Their wiring sample says:

  Note that the DC ground of all power supplies used should be connected
  together to provide a single common ground reference. In addition to
  this, the positive output from each power supply should be isolated in
  order to avoid differing voltage potentials occurring across multiple
  power supplies, which could result in damage.

I am trying to imagine a way in which "damaging" voltage (which I assume would mean significant overvoltage) could be developed by injecting from identical power supplies without isolation on the positive side if they share the same ground reference.  Is that possible, and if so then how?


texts: How to connect multiple rf433 transmitter to receiver?

texts:
I am doing a simple project where I place sensors at different parts of the house and send data to my rpi. I am using the rf433 for the wireless transmission but I discovered I cannot do multiple transmitters to 1 receiver nor can have multiple sets of RF near each other or else it cannot send signal.

I don't want to use XBEE because it's too expensive. Any suggestions on how to solve this problem?


texts: Splitting DC Supply Rail with High Output Currents

texts:
I'm currently working on a audio amplifier circuit that requires split supply rails. I have a wall converter that can supply 19V, and I ideally want to be able to create a ± 12V supply rail out of the 19V and still be able to output somewhere around 3amps. Does anyone know an easy solution? Most solutions I've found can only supply up to 500mA.
If it's much easier, I can also just split the 19V to ±9.5V. But again, I have not been able to find a circuit or IC that can output up to 3amps.


texts: How to make a 12V distribution block for hard drives

texts:
I have six external hard drives with 12V transformer bricks.  I want to power them all from a single PSU to save space, weight, and power.  But I have two concerns about this approach:

If one drive shorts, it might short out all the other drives.
Multiple drives spinning up simultaneously might spike the voltage.

How to prevent those problems?


texts: Why is dark-current considered a disadvantage in photo-detectors?

texts: One of the noted disadvantages, of avalanche photo-diodes being used a photo-receptors within the context of fiber optics systems is that they have a large dark current. Why is this considered a disadvantage? Is it just seen as another source of noise?


texts: Minimal circuit to flash STM32F4 using STLINK

texts: I wonder if I need to put some circuit between STLINK and STM32F4 MCU to flash it or does it simply require to connect the wires 1:1 directly? I cannot find it in the datasheet.


texts: Inferring D-latch on Zedboard within Vivado Error

texts:
I'm trying to implement a simple latch on a ZedBoard via Vivado.

begin
process(D,Enable) begin
   if(Enable = '1') then
       Q <= D;
       Qbar <= not(D);
   end if;
end process;

I'm using user I/O on the constraints for the inputs/outputs. I assign the inpus to two SWITCH Pins and the outputs to two LED pins.

The routing (implementation phase) gives me the following error:

  [Place 30-574] Poor placement for routing between an IO pin and BUFG. If this sub optimal condition is acceptable for this design, you may use the CLOCK_DEDICATED_ROUTE constraint in the .xdc file to demote this message to a WARNING. However, the use of this override is highly discouraged. These examples can be used directly in the .xdc file to override this clock rule.
      < set_property CLOCK_DEDICATED_ROUTE FALSE [get_nets Enable_IBUF] >

  Enable_IBUF_inst (IBUF.O) is locked to IOB_X1Y125
       and Enable_IBUF_BUFG_inst (BUFG.I) is provisionally placed by clockplacer on BUFGCTRL_X0Y31`

The two suggested solutions to the problem are here and setting the < set_property CLOCK_DEDICATED_ROUTE FALSE [get_nets Enable_IBUF] > works but I would like to understand solution 1
1) Move the clock input to a clock capable pin. since it seems important.

How can I find a clock capable input that I can press/move like I do on the switch?

Edit: Link of the ZedBoard pins (already tried C19 -> FMC_CLK1)


texts:
Can I reversely route the data polarity to USB common mode filter below?  Namely, connect USB trace D+ to the filter pin D- to simplify layout.

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/DM00039389.pdf


texts: How to write a for-generate statement to generate multiple instances of this parallel sorting network circuit?

texts:
I'm trying to implement a parallel sorting network. I'm curious to how one would write a for-generate statement to generate 128 instances of this sorting circuit?

It's supposed to sort 256 8-bit numbers from least to greatest without a clock using only combinational logic.

This is a link to the paper on the sorting network I'm trying to use:

https://www.researchgate.net/publication/261152327_Zero-delay_FPGA-based_odd-even_sorting_network?enrichId=rgreq-27e12d3d7cce338ad2cbbdffa750edb4-XXX&enrichSource=Y292ZXJQYWdlOzI2MTE1MjMyNztBUzoyMzg2MDc5Njk1NTAzNDNAMTQzMzg5OTk4MTg4Nw%3D%3D&el=1_x_3&_esc=publicationCoverPdf

Links to the circuit and sorting network diagram are below.


texts: Multimeter diode mode: do different multimeters show the same results approximately?

texts: I think that in many cases the voltage that a multimeter shows in diode mode is dependent on the current it uses for that mode. So the values measured by different multimeters in diode mode should be different in many cases. Am I right? If that's the case, why don't they make a universally accepted standard, so that all multimeters use the same amount of current in diode made and the measured values can be compared (which could be helpful in diagnostics)?


texts: Is there a simple circuit which would behave similarly to a diode, but with a higher cut-in voltage?

texts:
I was wondering if there exist any relatively simple circuit which would have an I-V characteristic similar to that of a diode (i.e. exponential but small before the cut-in voltage) but with a higher cut-in voltage. I know I could just have several diodes in series but this quickly becomes impractical as I need the cut-in of around 5V which means around 8 diodes in series.

EDIT: Actually, what is important for me is that diode to have a smoother knee in the I-V characteristic. The more evidently exponential the thing the better.


texts: STM32: Timer interrupt works immediately

texts:
This is code for timer in my project on STM32F429:

//timer initialization
 void timerInit()
 {
  uwPrescalerValue2 = (uint32_t) ((SystemCoreClock / 2) / 100000) - 1;
  RS485Timer.Instance = TIM5;
  RS485Timer.Init.Period = 67400000; // high value to notice interrupt even without debugging
  RS485Timer.Init.Prescaler = 400000;
  RS485Timer.Init.ClockDivision = 0;
  RS485Timer.Init.CounterMode = TIM_COUNTERMODE_UP;
  HAL_TIM_Base_Init(&RS485Timer);
 }

 void timerReset()
 {
 HAL_TIM_Base_Stop_IT(&RS485Timer);
 HAL_TIM_Base_DeInit(&RS485Timer);
 HAL_TIM_Base_Init(&RS485Timer);
 HAL_TIM_Base_Start_IT(&RS485Timer);
 printf("%d timer reset\n", countereset);
 countereset++;
 }

 void HAL_TIM_Base_MspInit(TIM_HandleTypeDef *htim)
 {
  /*##-1- Enable peripherals and GPIO Clocks #################################*/
  /* TIMx Peripheral clock enable */
  __TIM5_CLK_ENABLE();

  /*##-2- Configure the NVIC for TIMx #########################################*/
  /* Set the TIMx priority */
  HAL_NVIC_SetPriority(TIM5_IRQn, 7, 1);

  /* Enable the TIMx global Interrupt */
  HAL_NVIC_EnableIRQ(TIM5_IRQn);
 }

 void HAL_TIM_Base_MspDeInit(TIM_HandleTypeDef *htim)
 {
  __TIM5_FORCE_RESET();
  __TIM5_RELEASE_RESET();

  HAL_NVIC_DisableIRQ(TIM5_IRQn);
 }

 void TIM5_IRQHandler(void)
 {
  if (__HAL_TIM_GET_FLAG(&RS485Timer, TIM_FLAG_UPDATE) != RESET)      //In case other interrupts are also running
  {
   if (__HAL_TIM_GET_ITSTATUS(&RS485Timer, TIM_IT_UPDATE) != RESET)
   {
    __HAL_TIM_CLEAR_FLAG(&RS485Timer, TIM_FLAG_UPDATE);
    HAL_TIM_IRQHandler(&RS485Timer);
    printf("timer interrupt\n");
   }
  }
 }

And after running timerReset() function in the middle of my program, interrupt starts not few seconds later, but almost immediately. I tried few other timers to check if there is no hardware problem, but no, it isn't.


texts:
According to the description that I am reading in book it says that you need to connect +Vcc to both the A and B in order to get the output 1 at Q.

I don't really understand this. What does the +Vcc mean here? and How does the Inputs work? To visualize this, does it mean that when both A and B will be positive when connected to +Vcc wire, if so then diode will be reversed biased as far as I know. But how will the output be 1?


texts: Minimum Switching Current in Boost regulator Datasheet

texts:
I am planning to use TI TLV61220 in one of my designs. My design will be in sleep most of the time & the current in sleep mode is 10-20 uA. In active mode, it wil take max 10mA.

The device is powered from a CR123A battery which operates @ 3V down to 2.3V. I am stepping this voltage up to 3.3V fixed. I am planning to use TLV61220 for this purpose.

The datasheet says "Minimum Switching current - 200mA". Can some one clarify what it means?

The datasheet is :-

http://www.ti.com/lit/ds/symlink/tlv61220.pdf


texts: Can I use white LEDs in reverse parallel to select which one lights based on polarity?

texts:
I have a setup where I'd like to select one (or neither) of 2 LEDs for reflected or transmitted illumination, but it's under vacuum and I only have a single BNC feedthrough (at least until more parts come).  Easiest would be flipping the polarity of the cables from the power supply.l
I recall two facts: first, white LEDs have a poor tolerance for reverse bias (so an antiparallel diode is used for protection); second, red/green LEDs connected antiparallel were common and the diodes protected each other.
So if I get 2 typical white LEDs from the parts bin and connect them anti-parallel, would this be expected to be enough to protect them from reverse breakdown?
I say typical for two reasons: I have some leftover that are suitable in terms of brightness and emission angle, but I have no paperwork for them; I'm interested in the general case - if this would work for most LEDs, I'll do it even when I have more parts, if not, I'll design something better.


texts: What does this symbol in a schematic diagram mean? (wire through circle)

texts:
I am looking at the data sheet for the iC-NZN N-type laser diode driver.

What does the marked symbol stand for?

It appears in a number of places, always marking IO pins.
My guess would have been that it is a current limiter, but then why not just draw a resistor...


texts: Basic BJT current mirror : ... so the collector-base voltage of Q2 is also zero?

texts:
From this schema

I don't understand this sentence from here, particulary in section "Basic BJT current mirror"
"...If Q1 and Q2 are matched, that is, have substantially the same device properties, and if the mirror output voltage is chosen so the collector-base voltage of Q2 is also zero..."
My question is : Why collector-base voltage of Q2 is also zero ?


texts:
I need to isolate galvanically my antenna from my RF transceiver. For this I have been recommended a transformer, I select a 1:1 transformer operating in high frequency range. Is it enough to wire it in between the antenna and the transmitter, or we need to take more considerations. The present antenna impedance is 50E.

I also need recommendation for ferrite core to operate at 900MHz and provide least insertion loss.


texts: Why does current not increase when the voltage increases in this case?

texts:
When talking about BJT transistors, a very common graph is the one shown below, that plots (VCE,IC) as an ascending function. As far as I know, the BJT manages VCE so that IC is beta times IB, being
 VCE = 10V - IC 10K
in the example circuit.
Which can be rewritten as
IC = (10V-VCE)/10K

But that equation doesn't fit the graph at all. I understand that it behaves in a different way around 0 since the voltage can not go under 0, but I don't understand why it grows.


texts: What is the diffrents in below MOSFET circuit considering control circuit?

texts: What is the different in below MOSFET circuit considering control circuit? What is the charge pump involving ? Is it required charge pump for the both the circuit?


texts: Eagle Library Management -- Is there a "right way"?

texts:
I've never really been able to manage user-libraries particularly well in Eagle.  The problem becomes exacerbated when moving projects from computer to computer, and even worse when trying to maintain some sort of version control.  This came to a head yesterday when I did an Eagle version update, and simply rolled it back rather than dealing with issues the right way (complicated by trying to do some pro-bono consulting on a feel-good project that I need to keep entirely separated from the resources of my employer).

The closest I've come to being anywhere near happy is to maintain a user library for each and every project, and include it as part of the subversion set.  This, however, has some real limitations, but boy, it certainly makes things unambiguous.

Is there a good way to maintain a user library tree that's friendly for portability and version control?


texts:
I am building a open source application in which digital circuits can be built on breadboard using IC, wires, LED and some off board components(clock, 7-segment etc). I have made a initial design of breadboard (through programming, not in image processor), i have some questions regarding this breadboard shown below -

It is as i said in initial stages.
So as you can see the area is quite small.(100% size)

Is it incorrect to have only 2 bus rows? (by this i am concerned, if you as a user will be annoyed or angry without top and bottom bus)
Is the spacing between various contacts appropriate? [Answered well]
Is the Top View only, for IC, wires, LED etc. confusing? [Answered well]
I have used Red, Blue, Green, Yellow and Black wires in my laboratory. Have you used any other contrasting color which should be used here?

Any other fault with this design?
Criticism is welcome.


texts: I know it is bad to solder lead-free devices, such as resistors, with lead. However, is it possible (with less effort) to remove this lead-free coating on the resistors to make it possible to solder with lead? PCB has also a chemical coating.


texts: Potential divider to check IV characteristics

texts:
first post here, and quite a specific and probably incredibly basic question.

Im trying to find out the reasoning for a remark made in a college paper to do with IV characteristics of diodes.

Basically the question asks the student to draw a circuit to investigate the IV characteristics of a diode.

Now the mark scheme says that the circuit should have the diode and a variable resistor, plus a safety resistor all connected in series. A voltmeter across the diode, and an ammeter in series.

It also shows a second circuit which has the diode in a potential divider circuit set up, again with a voltmeter across the diode and ammeter in series in the same branch as the diode.

In the examiner's remarks where they discuss how students answered the question it says that "There were very few occasions where a potential divider was used even though this is best practice for obtaining the full characteristics for the diode".

My question is in this case of determining an IV characteristic of a diode, what makes using a potential divider better or "better practice" than simply throwing it in series with a variable resistor?  I also don't follow the "full characteristics" part of the explanation.  I see no difference in the range of results you would get in either situation...

Can any one shed some light on this?

Cheers

Miguel


texts:
I have shared my circuit diagram in the image i have attached in this post.
The problem i am facing here is , the esp8266-12e does not start in first attempt,
I have to reset the module (or power on/off) multiple times and then it starts after number of attempts.
The voltage reading in multi-meter shows appropriate all the times, even the voltage in ESP8266-12e module shows perfect. but the module does not start.

NOTE - Here module starting means, starting it in Access Point Mode.


texts: How do electrical signals not get out of sync in CPUs and other integrated circuits?

texts:
I'm a newbie at electronics and this question has kept me occupied for a while:
How do electrical signals not get out of sync in integrated circuits and CPUs?
For example, let's take a look at 3 bit adder:

(source: visionics.a.se)
As you can see, signal from "C" going the bottom path goes through just one logic element, however signal from "A" has to go through at least 2 or 3 logic elements.
Wouldn't the signal "A" get delayed? What if one signal goes through no logic elements, and the other has to go through 100,000? How do they get synchronized? How does CPU make sure right ones and zeros get processed at the right time?


texts: I want to get details on the concept of segmentation in cellular communication and how it helps to increase the capacity of system?


texts:
As image shows the power socket is fried, is there a method to repair it?
BTW this is only the fried 4 pins is for +12v and the ground, one +12v still ok but don't know if it enough.


texts:
I was looking at this mobile charger circuit trying to understand it. I am assuming it's a pwm based power supply (pulsating dc is given as tfr input). What I did not understand is which transistor is creating the pwm and does pwm change based on load(if so  all Trans. has only 3 pins no feedback pin).
What does PC1 do?
Why does this tfr have 4 i/p and 2 o/p?
Any links or documentation would be great.
Q1=AR13003 0020
D5=1N4007
TFR=182-0113030R V:1 1005CD
Q3=AZ431 BZ-BE1 942050 near output
PC1=0945817C
Thanks in advance.


texts: How do voltage, resistance and amperage work? (In DC circuits)

texts:
I have a (probably newb) question that I can't figure out.

What I think I know is this:

Voltage is electric potential (or rather a difference thereof)
Amperage is the rate at which electrons move
Resistance is a thing stopping electricity. One of those brown things with the stripes.

I've also been told that V = IR. That doesn't make sense to me. If some unknown power source causes there to be 12 volts and there is also a 150 Ohm resistor, then there must be .08 amps? Regardless of whether the power source is 8 AAs or a car battery?

Thank you for the help.


texts:
I am using TCA6424ARGJR IC so from its output port 24 I need to keep an led, which glow when there is high.
Can we drive an led from output port of TCA6424ARGJR IC?
I have connected as shown in IMG.


texts: Does this loadcell's creep mean that I can not let a constant load on the loadcell?

texts:
I want to build a connected scale that I can set coffee powder (for example) on it and check over the internet how much of coffee I still have without going to see it.

Usually all loadcells have a creep factor, like this one, which has a creep factor of 0.1%FS/10MIN Does this mean that the output will decrease by 0.1% each 10 minutes at full scale? If this is true, then the connected scale is not a viable product?


texts:
I'm working on a low power application. With a PIC24F (3.3V) I want to control the power to an SD card, turning it on and off. Typical current draw is 50mA, but can go as high as 200mA. I already have a 3.3V supply.

I was thinking of something using a 2N7000 MOSFET. What gate-source voltage would saturate these? Is it possible to do this on the high side or will it have to be on the low side?


texts: Understanding PIC32 digital output with open-drain

texts:
I'm trying to understand how to operate digital pins configured as open-drain outputs on a pic32. As I've read on other forums, setting TRISx to 0 and ODCx to 1 configures the pin as open-drain output, and writing 1 to LATx will drive the output high-Z (w/pullup resistor) and writing 0 will drive it low.

Source: http://www.microchip.com/forums/FindPost/789946

  If you have an actual open drain output, you can keep TRIS low and control the transistor with LAT. LAT=0 => transistor closed to ground and the output will be low, LAT=1 => transistor open and output will be floating or clamped high with a resistor (or pulled low by another signal).

What I'm caught up on is this part of the diagram for the pins:

From the PIC32 IO Port Reference Manual

What does ODCx do if TRISx is set 0? The output of the multiplexer controlled by ODCx will be low no matter what, as its either TRISx or (TRISx AND 'LATx), which will always be 0 when TRISx is 0.


texts: Question on LED usage for constant current LED driver

texts:
I am a beginning electronics hobbyist interested in robotics, who started about ~1,5 year ago, and with much to learn. I've got a question on using a constant current PMIC on a PCB project that I am working on, and was hoping that I could learn a bit more about working with them here. I would like to use two Infineon BCR402R LED drivers (datasheet) to supply 20mA to 2 separate power indicator leds for 5v and 6v voltage regulators. The PCB that I am designing runs on a 3S LiPo battery, so the voltage will range from 12.6v to ~10.5v. The LEDS will be powered from the main voltage source because both voltage regulators contain a PG (power good) pin that will go low when the voltage goes below or above expected values, so I am trying to avoid using the Vout pins from the regulators.
My question is on the LEDs that I should use, most SMD leds that I can find are rated around 3.3v, but the input voltage to the LED drivers (12.6v to 10.5v) is much higher. I read about voltage compliance, but I am not sure if I understand it correctly.  Do these 3.3v leds rated for 20mA work with the provided LED driver and voltages? Does the voltage provided by the LED driver drop because of the current limit, or should the voltages be brought back to 3.3v somehow to prevent damage?
I realize that my knowledge obviously lacks here, and unfortunately searching Google did not provide the answers that I hoped to find. Thanks in advance for your time and effort!


texts: Can you set up a monostable 555 timer so it reverses the output?

texts: I would like to make an alarm that goes off about 1 minute after it has been triggered. To do this, I want to delay the circuit using a 555 timer in monostable, but I can't do this as they turn it on for a certain amount of time and then off. Is there a way I could set up the 555 so that this is reversed? (I can't use a NOT gate as then it would be on while not being triggered) Or maybe another way this can be done?


texts: How to protect audio device in car amplifier

texts:
I want to install amplifier module based on TDA7297 dual bridge amplifier in my car. The kit is based on the low-cost example shown in datasheet (fig. 3, page 5).

Is there any recommended way to protect the input? I don't want to fry my phone because there is spike in the voltage when starting the car or something like that.


texts: Variation of resistance within conductor due to Skin effect

texts:
What is Skin effect? I learnt that it is a property exhibited by all conducting materials to restrict the flow of current ( eventually ac ) at higher frequencies to their boundary.

My question is does the resistance vary within the conductor i.e. higher at core and decreasing towards boundary?


texts: What does this chip do? And I want to get a datasheet - Top markings include: Analogix ANX6212

texts:
What does this chip do? Top markings include: Analogix ANX6212

And I would like to get a datasheet, if possible.


texts: Which MOSFET transistor or other component would have 6V min switching voltage? Supply voltage 6-16VDC and max current 300mA. I would like make switch 16Vdc. Switch to be "on" when supply voltage is 10V or greater. Below 10 V switch need to be off while input is still connected to supply voltage but les then 10V.


texts:
so my professor told me that the current flows in this circuit is I=(VI-(Vzo+0.7) / R.
But as I learned earlier, it should be written as (VI-Vzo)/ (R+rz).
I didn't get it. Which is wright?


texts: I need help with the circuit analysis, specifically, if the LED frwd voltage range is 1.6V-2.1V and the power rail is 1.8V connecting to a 1.8V I/O, how can I figure out what amount of current (voltage) is going through each leg of the circuit? Will the LED have enough Frwd current to turn on (20mA). On this device, the LED I/O can also be used for strapping.


texts:
Looking for some advice, completely new to electronics so please bear with me.

I am currently working on a project to build an automatic watch winder, I have a 12v 10rpm motor which should be suitable for the application.

I am looking into options for starting the circuit on a cycle say, 15mins run time for every 3hrs.. As opposed to just an on/off switch.

The initial research I did lead me to believe a '555 timer' might be in order, but it would seem the length of time I am talking about is unsuitable for this.

So onto using a micro controller of sorts and there seems to be ALOT of different options!

Was hoping someone could point me in the right direction for something which looks more suitable ?

Thank you in advance,

David


texts:
I have a relay that is switching 240V supply to a plug pack. The plug pack in turn supplies 24V to a solenoid coil.

The relay has fused in the closed position and I'm trying to figure out why and the best way to protect it when I get a new one.

Am I correct in assuming the flyback from the solenoid is isolated by the plug pack?

And if so, will an RC snubber circuit be the correct way to prevent arcing when cutting supply to the plug pack?

The relays specs can be seen here: link

It's rated for 6A 250VAC and is switching a 0.9A plug pack.

simulate this circuit – Schematic created using CircuitLab


texts: How can I regulate the voltage of a Li-ion battery with the least drop out voltage?

texts:
I have a one of these:

descriptions:

full charge voltage : 4.2V
cut off discharge voltage : 2.75V
capacity : 4000mAh
size : 18650

And I want to get 3.3V from it.

but the problem is I can't use regulators (such as AMS1117) because the drop out voltage of it is 1.1V and I should have a 3.3V + 1.1V  = 4.4V at the input. And its impossible for my battery.

What should I do to have 3.3V until the battery discharges to 3.3V ?


texts: Arduino as ISP programming the Arduino, not the connected ATmega328P

texts:
I am trying to program an ATmega328P with an Arduino Uno R3. When I click 'Upload to Programmer' in the Arduino IDE (version 1.0.5), the Arduino programs itself and not the chip. Stranger still, the ArduinoISP sketch continues to run on the Arduino as well as the program that should've been burned to the chip. Here are the steps I take:

ArduinoISP sketch is open

Tools > Boards > Arduino UNO
Tools > Programmer > AVRISP mkII
File > Upload

Upload successfully completes

File > Examples > 01.Basics > Blink
Tools > Boards > Arduino Nano w/ ATmega328
Tools > Programmer > Arduino as ISP
File > Upload Using Programmer

No AVRDUDE errors, upload appears to have successfully completed

After I take these steps, the Arduino still has the ArduinoISP heartbeat LED beating, but the pin 13 'L' LED is also blinking on and off, just like in the Blink sketch. This persists even if the Arduino is manually reset; it's as if the Arduino has 2 sketches running at once. The LED connected to pin 13 on the ATmega328P does not blink.

Here is my wiring:

NOTE: There is also a 10uF electrolyte capacitor the Uno's between RESET (+) and GND (-) which was missed off the above diagram.

Can anybody help me program this ATmega328P? I have tried 2 different chips, and both have had the same issue.


texts: 12F675: ICSP: /MCLR internally tied to Vdd

texts:
I'm using the 8-pin 12F675 so have to be conservative with pins. I want to use ICSP while having /MCLR internally tied to Vdd so freeing up GP3. The supply will be 5V.

I will be re-programming the chip via ICSP multiple times.

Reference documents: ICSP; 12F675.
Related question: ICSP Circuit: Pic microcontroller MCLR pin

My first (main) concern: if /MCLR is internally tied to Vdd, then when the programmer ties it to a voltage other than Vdd, will a damaging current be produced? Can / how should this be done? (Could I simply put a resistor between /MCLR and the programmer's Vpp?) Also, with the resistor, would the internal tying to Vdd prevent the programmer from pulling the pin to Vpp/Gnd?

Second (secondary) concern: how can I then use the /MCLR/Vpp/GP3 pin as an input? I appreciate this is more complicated, it probably needs a question of its own. I presume again just a resistor between the PIC's GP3 pin and the driving circuit would do: high enough value so that the programmer can override it.


texts: What is the effect of a triac on a torque/speed curve?

texts:
I am trying to understand the impact of a triac based speed control on the torque/speed curve of a motor. For as easy example, let's use a corded drill as an example. If I pull the trigger all the way the motor gets the full waveform and the torque/speed curve will look like a typical universal motor:

(image source)

Now let's say I only squeeze the trigger down 50% so that the waveform now is chopped up by the triac. What happens to that curve?

Another way to ask the question is does a triac change the speed more, the torque more, or both in some proportion?


texts: I am trying to calibrate an audiometer that gives outputs in dB SPL. However, the sound meter that I am using to calibrate the audiometer registers in dB A. Is there a formula to convert from dB A to dB SPL?


texts:
Typically the question is: after having selected all the components in a schematic minus the Power Management systems, we then define which voltage and current each block will use, then we need to convert the power source into power rail to power each block. This is mostly done with LDO and DC-DC converter.

I have difficulties to understand in which situations we are using a DC-DC converter in series with a LDO vs (LDO alone or DC-DC alone).

Does anyone can enlight me to understand how we build the block of power management system in a block diagram or a schematic ?


texts:
I built myself a headphone amplifier using the LM49600 and a PGA2310 for volume control. This part of the circuit is fairly standard and I don't think it's the problem. I wanted it to be powered by a simple 5V wall wart or an USB charger. I used a TPS65131 followed by some linear regulators and a lot of filtering. There is a single ground plane.

There is a faint but unacceptable audible noise when the 5V input is connected to a wall wart and the audio input is connected to a desktop PC. The amount and frequency of the noise changes with different chargers or power supplies. The noise becomes much worse when powering from one of the USB ports on the same PC.

It goes away completely when powered from a USB power bank, or when using a phone as the audio source.

What's causing this? My best guess is common mode noise coming through the transformer capacitance or the y-cap in the wall wart.

How do I fix this? I'd like to do something on my end without touching the external supply to keep it universal.


texts: Can I connect an inverter and a solar charge controller together in parallel with battery terminals?

texts:
I have an inverter works on AC mains and has battery charger inbuilt. I have solar panels with a charge controller.
Can I connect both power sources wires to battery terminals in parallel. So In case of power interruption, battery could charge using solar.


texts: What is the purpose of non-black dummy pixels in a linear CCD?

texts:
I'm studying the datasheet of Sony ILX511 linear CCD (PDF). On the Clock Timing Diagram, first 32 or 33 (depending on the mode) clock cycles give out dummy pixels, and only 18 of them are Optical black, which, as I understand, means they are covered and can be used as reference dark signal.

When I watched the output of this CCD with an oscilloscope, I saw that, although the dummy pixels indeed don't depend on illuminance of the sensor, they have consistent bias from the dark level. Moreover, this bias depends on the pixel number. The first dummy pixel shows a large dip in "measured illuminance" (if we could interpret it as such—actually simply higher voltage), and the rest dummy pixels show something like an exponential decrease of the bias (with a different sign than the first pixel), with the bias getting to zero when optical black pixels begin.

What is the purpose of these non-black dummy pixels? Are they actually useful for something, or is this simply an artifact of the way the CCD functions?


texts: Basic RF ping-power transceiver for 100s of nodes

texts:
I'm working on an art piece that intends to emulate fireflies synchronizing their flashes. There will be hundreds of tiny LED nodes hung from a tree each running on a small battery. I'm curious if there is a novel way to use RF to synchronize the flashing. (this could be done with IR, but doing it with RF could let everything be more contained)
The idea is that each node would send a low-power RF ping when it flashes its LED. The ping would not need to contain any data at all. All the other nodes would listen on that frequency in order to time their flashes.  The moment which has the most pings would be seen as the moment to synchronize towards.
I've not done a lot of RF work, so I'm curious how possible this is in a small low power device. Since we don't care about data, would it be possible to simply detect that one moment has more transmitting nodes than other moments? More RF power? I assume there would be too much interference, without going down a mesh network path, to actually receive data.


texts: Not really sure where to ask this question.  I was watching an episode of a TV show involving a gas generator and it got me wondering whether electricity could still be generated by a gas generator after an EMP.  If the engine of the generator is powered solely by gasoline, will it still work after an electromagnetic pulse?


texts: Why do you need to replace the inductor with a voltage source of 1V in this dependent source circuit to find its thevenin resistance?

texts:
simulate this circuit – Schematic created using CircuitLab

I1 in the Kirchoff Voltage Law loop in the first circuit is equal to the I in the second circuit.I1 is also negative I0.

First Loop: $$2(I_1-I_2)+1=0$$

Second Loop: $$4I_2+2(I_2-I_1)-3I_1=0$$ (3I from the current controlled voltage source is equal to 3I_1 ).

You solve the equations and get I_1==-3A. And I_0=3A. R thevenin would be V_0/I_0=1/3 Ohm.

MY questions:

Why do we have to replace the inductor with a voltage source of 1V (Or Current source of 1A)?
Why can't we simply find R thevenin by short ciruciting the voltage source and find the equivalent resistance acroos the terminals of the inductor. In that case, the equivalent would be equal to 4 Ohm|| 2 Ohm =1.333 Ohm.


texts: Beaglebone Black LCD/TFT/display and I2C2

texts:
I am considering buying a 4D Systems I2C LCD for the BBB, e.g. a 7" touchscreen, which uses the I2C2 bus.

The question is, will I be able to use other peripherals on I2C2, on a home made cape, alongside the LCD ?


texts:
Just having a little trouble understanding this solution. I understand that we are trying to achieve an equivalent voltage drop across the terminals a & b to represent the circuit.
However I don't get why Vth = Vx, and it's the dependent current source that's bothering me.
Is the fact that the 60 ohm resistor and the dependent source being connected in parallel and to the same node meaning the voltage drop across both elements is equal? If the two elements were switched around it would make sense to me that Vth would be the voltage through the 60 ohm. Also I should note that calculating Vth isn't the problem it's just knowing where I should be taking the equivalent voltage from, like I guess the crux of the problem is why have they chosen the 60 ohm.

Text from image:

Obtain the Thevenin and Norton equivalent circuits of the circuit in Fig. 4.114 with respect to terminals a and b.
Since \$V_{Th} = V_{ab} = V_x\$, we apply KCL at the node \$\mathrm{a}\$ and obtain:
$$\frac{30-V_{Th}}{12} = \frac{V_{Th}}{60} + 2V_{Th} \longrightarrow V_{Th} = \frac{150}{126} = 1.19\mathrm{V}$$


texts:
I have been splitting PTFE FPC jumpers using an Exacto knife and that works fine, but the Nomex FPC connectors are cheaper. The PTFE is a tough, but pliable, homogeneous material so cuts just fine with straight, clean lines. But my understanding is Nomex is a kevlar-like material (difficult to cut and has fibers in it so does not cut cleanly).

Has anyone handled Nomex FPC jumpers to get a feel whether it can be cut by a knife?


texts: Features values of typical BJT/MOS transistors

texts:
Is there a page that lists the values of all the features of typical BJT/CMOS transistors? e.g. ON-resistance, gate/base capacitance, amount of power the D-S/C-E junction is able to hold etc.
Of course, these values change, but I need only typical values that will help me to better understand the difference between these two transistor types. I need something that will help to "feel the difference" with actual values.


texts: Self resonance frequency for MLCC capacitor

texts: Is there a general self resonance frequency characteristics for MLCC capacitors? If I make a RC low pass filter, say using 1kohm and 15nF 0603 with fc = 10.6kHz, I guess it won't work as LPF beyond the self resonance frequency of capacitor. I couldn't find the self resonance frequency characteristics for capacitor (C0603C153F3GACTU) in its datasheet. Is there a general estimation? I am interested to know the frequency response of the filter for around 100-200 MHz.


texts: Running LED dot matrix using shift registers

texts: So as the title suggests, I'm using 3 shift registers (74595) to run a dual colour LED dot matrix display by daisy-chaining them (I believe that's the term). I haven't got to the coding bit yet, but before that I'm having doubts about the current usage of the system. I'll be using an Arduino to run it, and I soldered the display and ICs on a veroboard without using current limiting resistors (oops). If I use a current limiting resistor before the first shift register, at the digital pin of the Arduino, will it work? I'm worried the entire system will draw too much current.


texts: I want to know what cable I should be using to connect my demarc to my DSL modem. When I plug in my DSL modem in the utility room (which is about 20' of wire from the demarc) I get a pathetic 4Mbps download rate (I'm told the telco's hardware is very old in my neighbourhood). When I test the modem by plugging it directly into the demarc, it jumps to 6Mbps. I want to connect my modem closer to the demarc (but I can't plug it into the demarc, because it's outside) and maybe use a different cable, but what kind of cable should I use? I heard in one place that CAT-5 is better than phone cable, but I've also heard there wouldn't be an improvement.


texts: Simplest way to measure 98 to 140 Ohm range with an ADC?

texts:
I have a thermistor that should vary between 98 and 140 Ohm and am looking for the simplest circuit that will convert this into something meaningful for a 10 bit ADC in the 0-3.3V range.

Precision wise, 0.4 Ohm or so on average would be great, and let's just ignore the nonlinearity issue altogether. I'd rather save some circuitry than shoot for optimal results (and there will be a lookup table).

I have (only) +3.3V of input voltage, plenty of current, a dual op-amp that is hopefully useful somehow, and a bunch of resistors and some other crap. Suggestions?


texts: How to repeatedly read and write a SMD EEPROM without unsoldering it each time?

texts:
I am doing a lot of reverse engineering on SOIC-8 Eeproms in automotive ecus. At the moment it requires unsoldering the chip, read/write, solder the chip back in, test, repeat.

Most Eeproms have to be removed from the PCB in order to be read.

As you can imagine when this happens multiple times pins can become damaged and the PCB becomes a bit messy (if you're trying to do it in a hurry). Not to mention over just a week the amount of wasted hours.

How can I make it easier to read and write to the Eeprom without having so unsolder it from the PCB each time?

Most of the Eeproms I come across are Microwire devices such as the 93C46/56/66.


texts: Why does the ionosphere reflect HF but allow VHF signals to penetrate through?

texts:
Wikipedia says:

  ... Unlike high frequencies (HF), the ionosphere does not usually
  reflect VHF waves (called skywave propagation) so transmissions are
  restricted to the local radio horizon less than 100 miles...

Why does this happen? Is it merely that a VHF signal of say, 100Watts, carries more energy than an HF signal of the same power? Are there any other factors in play here?


texts: DIY 130kHz RFID antenna design for reading tags in large area

texts:
I need to construct an antenna for a reader that will pick up a 134.2 kHz RFID tag.

The antenna will need to be in "tunnel/culvert" under a road.  The tunnel is 2 metres wide, so antenna needs to be lie across that distance.  The animals carrying the tag are frogs so only a few cm normally above the antenna (they normally just "crawl").  However, Frogs do jump sometimes too so it may have to read a bit higher than that.  It sounds to me like  even ten cm is a bit of a stretch for these....true? false?

Any advice on what an antenna of this length (it would have to go across and back as a loop of course) would need to be made of and how to tune it  to give me a starting point for further research would be appreciated.


texts: Can't figure out EIA-232 (RJ45) to DB9 cable... (seems simple!)

texts:
I've purchased a used BayTech RPC4 unit (8-port power strip controllable using RS232).

The front of the unit has an RJ45 port (EIA-232) and has a wiring diagram on how to wire it to a DB9 port so you can connect it to a PC.

Here's the diagram:

If I use standard TIA-568B wiring for the RJ45 connector:

1 = orange/white
2 = orange
3 = green/white
4 = blue
5 = blue/white
6 = green
7 = brown/white
8 = brown

...then it looks like I need to connect to to a DB9 like this:

1 = DB9 #4
2 = DB9 #5
3 = DB9 #7
4 = DB9 #3
5 = DB9 #2
6 = DB9 #1
7 = DB9 #5
8 = DB9 #6+8

However, that doesn't seem to work.  I'm using WinXP HyperTerminal for testing (9600-8-N-1) and I don't get any input or output.

Can anybody help me out?  What am I doing wrong?


texts: VHDL: Using internal signals in testbench

texts:
I'm trying to use one of my design's internal signals in my testbench. I already know how I would do it in Verilog:

Goertzel i1 (
// port map - connection between master ports and signals/registers
);
.
.
.
always @ (posedge i1.en) //do something

en is the enable signal I generate in my sistem, it is a signal declared in the top module, which is created in one element of the system, and then distributed to some of the other elements via port maps.

So, in VHDL testbench, I want to do something like:

uut: Goertzel PORT MAP (
          RST => RST_s,
          CLK => CLK_s,
          X => X_s,
          Y1 => Y1_s,
          Y2 => Y2_s
        );
.
.
.
wait until "/goertzel_tb/uut/en/" = '1';  //path to variable, read in Questa

What is the correct syntax? Or is there a way to do this?

EDIT: Tried this:
Declared spy_en signal within TB file, and then did:

spy_en <= << signal.goertzel_tb.Goertzel.en : std_logic >>;

Questa gives errors.


texts: Does ESP8266 deep sleep make sense while on the power supply?

texts:
If ESP8266 is powered via a dedicated power supply 220V AC → 3.3V DC.

Is it worth it to put ESP to deep sleep in order to reduce power consumption?

For example the indoor weather station, which makes measurements every hour.

I figured out that putting ESP to deep sleep definitely worth it when on a battery, but what about power supply?

P.S. This is the power supply I suppose to use.


texts: Overvoltage protection circuit - Serial zener diodes and op-amp

texts:
I need to prevent people from plugging in batteries with incorrect voltage. The 2 cell LiPo with voltage range from 6.4 to 9.8 V is alright, EN=1. But 3 cell LiPo is too much and I need the below circuit to generate EN=0.

The circuit below works as follows:

The positive op-amp input is tied to 3 V reference (Zener D3). The negative input is tied to "voltage-divider" made out of two 5V Zener diodes. The OP then generates EN = 1, if D1, D2 is not conducting (Vbat < 10 V), or EN = 0 if the D1, D2 are conducting (Vbat > 10V).

Question:

Is this the proper way to generate EN = 0 if 3 cell LiPo is plugged in? I somewhat doubt this, because the op-amp negative input is somewhat floating.

simulate this circuit – Schematic created using CircuitLab


texts: How to configure STM32CubeIDE with Blackmagic Probe as a debugger?

texts:
I am trying to use my Blackmagic probe (an STM32 BluePill converted to a Blackmagic Probe) as a debugging device for the STM32CubeIDE and can't get to work!
I tried this solution: https://github.com/mike-pittelko/BlackMagic-STM32CubeIDE but with no luck,
I'm getting the following error:

Error with command: usr/local/bin/arm-none-eabi-gdb --version
Cannot run program "usr/local/bin/arm-none-eabi-gdb": Unknown reason

My Environment:
1- MacOs Catalina
2- STM32CubeIDE - Version: 1.5.1 - Build: 9029_20201210_1234 (UTC)
3- Debugging an STM32 Bluepill board with an STM32 Bluepill converted to a Blackmagic Probe!


texts:
I have designed a high precision frequency counter circuit. I am using it to measure a frequency of around 35kHz that is stable to 0.1mHz. I can measure the frequency using a Stanford Research Systems SR620 and the only digits that change are 0.000XXX. My frequency counter varies by about 1Hz with the same signal. The SR620 uses some sort of Mean calculation to provide a more precise result. I am looking to learn how to do the same.

How the circuit works

There are two counters. A count down counter and a count up counter. The count down counter is loaded with the base frequency (or expected perfect input frequency) multiplied by the sample time in seconds. The count down counter decrements on each period of the 35kHz input. The count up counter counts a 2GHz signal while the count down is counting to zero. The count up counter stops when the count down counter reaches zero.

Then frequency = (base frequency * sample time in seconds) / (count up counter / 2GHz) or (count down counter start count) / (count up counter / 2GHz)

My circuit uses a PLL chip locked to a 10ppb 100MHz OCXO to generate a 2GHz signal. Using a rubidium standards 1pps output my counter is accurate to 2,000,000,000 +-15 for a 1 second reading. I need to be able to read a 35kHz signal and be accurate to 100uHz for a 1 second reading. The 35kHz signal can vary to as low as 31kHz and to as high as 39kHz but my readings are not performed while the frequency is changing.

What kind of calculation would make these readings more accurate and does anyone know of a resource that explains it?

My Solution

My issue ended up being a circuit logic to software issue. My standard deviation went from 1Hz to 100uHz after the fix. I did not need to modify my firmware math.


texts: Persisting circular buffer throughout C code

texts:
So I have a circular buffer on an embedded device that I need to persist throughout the code. Specifically, I need to have it be able to be used in the main and also in an interrupt handler (these are both in separate files). I know how to do this in assembly by manually loading registers but I'm having trouble cleanly doing it in C.

I appreciate any help as I've been trying to do this for days with no luck.

Notes:
I am using an stm32f103rg that uses a cortex M3 as the processor.


texts:
I'm a mechE and have been trying to get into the digital world for a bit and need to know why a system would need a clock signal at all. For example, if I have some bit of code getting executed on a device, why can't the logic gates performing code be controlled by logic such as this, "this gate does not open until I receive voltage here:"? and so on. Why does it need to operate by "this gate opens after so many clock signals"?

Thanks


texts: Multiple Cores vs Single Core Power Efficiency Equations

texts:
I was searching for OpenMP tutorials and I came up a video that showed some simple equations that promotes multiple core hierarchies against single core ones.
The equations used are

  Capacitance = Ability to store energy

  C=q/V ⇒ q=CV

  Work = Moving charge across voltage

  W=Vq ⇒ W=CV^2

  Power = Work over a period of time

  P=Wf ⇒ P=CV^2f

It then proceeds to calculate power requirement of a single core processor as

  Ps = CsVs^2fs

where Xs stands for X used on single core system.

It then goes on to calculate it for a dual core system responsible for doing the same work. But it uses following parameters (Not exactly 2 or 0.5 multipliers but they just make the problem more easier to understand):

  Cd = 2Cs
  Vd = 0.5Vs
  fd = 0.5fs

Power is calculated as

  Pd = 0.25Ps

I don't get why voltage and capacitance are altered.

The video is over here youtu.be/cMWGeJyrc9w?t=3m45s, if time link doesn't work for you, it starts about 3:45.


texts:
I have following circuit to measure the differential voltage across capacitor

The input is sinusoidal signal of 5MHz frequency and of voltage varying between 0-1volt so that my differential amplifier can have total swing.
The output of differential amplifier is read by single ended adc of microcontroller.
The voltage across capacitor measured using oscilloscope when not connected to differential amplifier varies with the voltage measured when connected to differential amplifier.
Is this the right way to measure the differential voltage across capacitor?


texts: I am facing a problem of micro controller reset, I am thinking of implementing the following to find the function in which it happens, then the root cause. As soon as I enter a function I will increment a global variable and store in eeprom. Once a reset happens I can identify the event, as I will start from main, and I will read the last eeprom value. From this I can know at which function reset happened. Now my main concern is whether I will finish the write cycle of that eeprom memory location. The reset happens approximately after every 2 hours. Any better ideas or it is OK to write in eeprom.


texts: What does "two signals aliasing to each other" mean?

texts:
So I just read something that two signals are aliasing to each other. I know what a single signal is being aliased - that is when sampling rate is not higher than or equal to the Nyquist rate. But I am just confused of what two signals aliasing to each other mean.

Let's say that each signal only carries single frequency. Let \$f_s\$ be sampling frequency and \$f_1\$ be the first signal and \$f_2\$. \$f_s\$ is assumed to be lower than Nyquist rate for both signals. In such case, in what condition of \$f_1\$ and \$f_2\$ would aliasing occur, given \$f_s\$?


texts:
I need to use a reed switch and a magnet on a shaft. When it get turned to a specific degree the magnet will trigger the reed switch. The shaft only turns one way and is turned by hand.
 The problem is the device could have a lot of vibrations; like falling to the ground or getting kicked and punched—kids involved :)  Now if a really bad knock occurs I can live with some false positives but those will be deferred as best as possible.

How can I find the correct reed switch and magnet combination. How do I match these parameters up? I know I need to select the correct reed switch but what do I need to look for in terms of identifying the "stiffness"/"tension" of the plates? Then I can just buy magnets and test them by trial and error?


texts: ST STM32H743XI (ARM M7 based) MCU - ADC Configuration

texts:
I am using the ST STM32H743XI (ARM M7 based) MCU,

I want to use the ADC to measure 7 Hall sensors (use both slow and fast channels),
i need the conversion time for all seven ADC channels to be the same,

How to make the conversion time for the slow and fast channels be exactly the same?


texts: How to light an LED to indicate when a usb port has a plug in it?

texts: I'm looking for a way to light a 3.0v-3.4v 20mA LED to indicate when a usb 2.0 port has a plug in it. The light should only be on when a device is plugged in. My usb 5v line is about 3.2 to 3.3 amps with an Xbox 360 Controller connected.   I tried wiring the led and resistor in series with the 5v usb port.  The LED lit but the plugged in device did not work.  I'm guessing the LED was only allowing 20mA to the device (Xbox 360 Controller) which was not enough for it.Would something like this work with a separate led power source? I'm REALLY new at this.


texts: Using too many Modules in Verilog affect timing?

texts:
I have a straightforward quest about HDL and FPGA design.

If I seperate my code to a lot of modules, by modules I mean verilog files which do specifig things instead of writing close to the top module, does it affect clk timing?

Ill try to illustrate my question:
the first option the I write most of my code in 1 file (not a top file, I know I shouldnt write logic on the top):

the second option that I going deep with my modules, instead of write lot of code in 1 file, I will have seperate hdl files that does some functionality and bring back upstair the answers, something like this:

does it affect timings of the clock/reset etc?
does it good design to write lot of modules and going deep with the modules or I should stay close the the top?

In my opinion, I using Lattice FPGA and I "Share Resources" option in the syntesis, and than, its doesnt matter.


texts: How to measure capacitor value using an LC circuit?

texts:
How would I measure the value of capacitor using an inductor of unknown value but with a function generator producing a sine wave of 1MHz?
I have an oscilloscope handy.
I lost the labelling on the capacitor.


texts: How can I change decimal place in HSPICE?

texts: Currently, the numbers in xxx.mt0 file are with 3 decimal place (example: 1.331e-07). I was wondering if I can set a flag in .sp file to increase the accuracy.


texts: Arduino nano resetting after solenoid valve fires

texts:
I'm trying to control small, plastic 12V solenoid valves with an Arduino nano. I have an Arduino nano hooked up to a Sainsmart 4-Channel 5V Relay Module, and finally connected to the solenoid valves, which are powered externally with an AC to DC converter. The valves are controlling gas flow to tanks of seawater for a marine biology experiment. As such, I need the solenoid valves to open and close very quickly (on the order of tenths to hundredths of a second).

The problem is that after the solenoid valves fire, my Arduino resets and reinitializes, and this messes with the timing of gas flow. I've isolated the problem to the powered solenoid valves (the code, arduino, relays, and solenoids all work perfectly when the solenoids are unpowered. The second I plug them in, the problem resumes). I think that reverse voltage spikes are causing my arduino to reset, but am not entirely sure.

I've looked into adding flyback diodes, but heard that those slow down the relays and again, I need the timing to be very fast. Does anyone know if adding a diode will solve my problem, and if so, how much will it slow down the relays?

My knowledge in electrical physics is limited, so if you could keep your explanations to more basic language, I'd appreciate it. But ANY and all help would be welcome! Thank you!


texts: FATFS copy between Ramdisk(FMC) and SD(SPI) on STM32F4

texts:
I am trying to solve this problem. I am using FATFS13 on my custom STM32F469 board and I am using the Standard Peripheral library.

I have connected 1MB of SRAM over the FMC bus, and an SD card over the SPI bus.
I can mount on both hardware a FAT file system, FAT12 on the RAM and FAT32 on the SD.
I tested SD cards up to 32GB so I can say that everything is working.
It's possible to manage files on each volume. I named them RAMDISK and SDCARD in the ffconf.h

Basically I want two drives so that the user can copy graphic files in the SRAM for a faster access during the execution of programs.

The problem is that when I try to copy a file from one drive to the other, it's copied only the first chunk of data.
A single cycle:
- read from source
- copy to dest
- read from source
-> Error 9 on the source ((9) The file/directory object is invalid).

I tried to dig into the code, and with the debugger I noticed that after the write to the destination file when it's time to read the second chunk of data, the 'obj->fs->fs_type' of the source file is set to 0. So the validation fails.

I can't figure out why. Did you have a similar experience?

In order to avoid this error I need to have only one file opened a time, so I temporary solved the problem with this sequence:
- open source
- read chunck of data at offset
- close source
- open destination for append
- save chunk of data
- close destination.

In your experience is there a particular way to perform a correct copy on different volumes?

Thank you.


texts: What's the actual difference between edge sensitive and level sensitive interrupts

texts:
Currently I'm working on a C8051F120 MCU where external interrupts can be defined in two ways:

Edge sensitive (falling)
Level sensitive (low-level)

In level-sensitive interrupts as soon as the MCU detects a low level at the external pin it will execute the ISR which is the same as detecting a falling edge.

I know I'm wrong as both can't be the same. Hence I'm asking this question: what's the actual difference between the two, in their detection procedure or in the execution of the ISR?


texts: Aternative diode classes for high frequency(10GHz) applications

texts:
I'm trying to design a voltage clamping circuit for a 10GHz signal. I've modeled it in spice using several schottky diodes and it works but only when the signal pulse is at least a few nanoseconds long. In my case I need diodes that can handle a pulse in the 50 picosecond range which means the reverse recovery time needs to be in the single digit picosecond range(The application can handle quite a bit of distortion to the signal) Unfortunately, this key timing requirement seems to be missing off of most data sheets that I look at for diodes. Does anyone know where I can find diodes in this range?

EDIT:Not sure why this was put on hold. I did not ask about a "specific product" as the hold reason states, I was asking about diodes in general. You might be thinking this is a minor distinction, but if you read, the details of the close rule and the reason it was created, you can see that it violates neither the technical definition of the rule nor the intent of the rule. Furthermore the intent of the rule is to prevent questions which are not likely to be helpful to others in the future, and this is a problem which is likely to be encountered by those working on increasingly high frequency circuits. The recommendation to move to microwave components is a spot-on answer to the question which is not overly specific at all. Even furthermore, the recommended "fix" for the close rule is to "Instead, describe your situation and the specific problem you're trying to solve." Which I have done to the best of my ability. I've explained why the typical diodes are not sufficient to meet my needs and explained that the specifications on data sheets were missing the information that I needed.


texts:
I’m a little confused on how complex numbers are used in circuit analysis . On one hand, complex numbers can only be used in linear circuits which do not involve any squares, square roots, and so forth of the voltage or current, or multiplication of one voltage or current by another. This way the real and imaginary parts don’t get mixed up. On the other hand, we do divide complex numbers by each other (e.g. when calculating complex impedance we divide voltage (in complex form) by current (also in complex form)) and the numbers still don’t get messed up. Why is it so?
Any help will be much appreciated.


texts: I am trying to simulate Synchronous Buck DC DC converter I have created the circuit now i want to test it to check whether it is giving me the correct output or not , I have tried the same circuit in LTSPice but there it is very easy to check the output but in simulink ihave tried every sink scope/block to attach to the output but it wont attach for e.g in this diagram i am trying to attach a voltage measurement block but i wouldnt , what can i do to view the output ?


texts: A4983 driver not producing output, except when output is shorted to GND

texts:
I'm having a bit of an issue with a circuit I've built, and I'm hoping someone could provide some input.  I'm making a stepper driver based on the A4983, and am having an odd issue - made even more odd by an accidental discovery.  Namely, the driver only produces current to the motor when one of the outputs (either 1A or 1B) are connected to GND with a low-value resistor.

How I came about this discovery was by accident - my DMM was left in current measuring mode and the motor would miraculously start spinning when I connected from GND to either 1A or 1B. (I intended to measure voltage on the output, which sits around 7V when measured at 1A.)

My bench top PSU reflects the same, showing a nominal 10mA draw for the entire circuit (including uC and a few other components), until this happens, and then it shoots up to 160mA when doing this.  Hooking the DMM up where output 1A is fed through the DMM common, and from DMM measure line to motor pole results in no current measured.

My circuit is below, can anyone see any obvious mistakes?  I'm completely stumped, connectivity tests on the circuit seem to indicate that everything is connected as expected.  All other components are working properly, and AEN and other inputs are set as expected (verified and measured).  The motor also performs properly when attached to another driver.


texts:
I made a circuit to use with my ESP32 to test 18650 battery capacity.
During tests I didn't notice that when I do dacWrite(dacpin, 0); output on DAC pin gets 0.1V instead of zero
Those tiny voltages are a problem because the LM358 op-amp is connected to the DAC pin in unity gain configuration which instead of shutting down keeps draining battery by 0.1V which at 2.8V (cutoff voltage) is 0.1A (or 100mA.)
Things I tried:

Connecting a 1k resistor from DAC pin to ground, doesn't work
Disabling DAC by dac_output_disable(DAC_CHANNEL_1);, output goes 0 but things get complicated, op-amp starts outputting randomly turning on the MOSFET.

Schematics:

Other than this problem, it works great paired with an ESP32 touch pin to start/reset and very good accuracy.
What can I do to make DAC output zero?
I thought of connecting an NPN transistor from the LM358 output to ground that will be turned on/off by microcontroller but because of my previous failed attempts at designing circuits and my love for my ESP32 didn't allow me to do this experiment.
If someone needs to view code or build this project: Code


texts: High Short-circuit protection for LiPo Battery

texts:
I will be using a LiPo battery for a project, and I want to make certain that I fully understand the safety features of the Protection Circuit Module included with the battery, so that I have a safe design.

When looking at the datasheet for the battery it includes details of the PCM, and lists the limits for when the PCM protects the battery. One of the features is the short-circuit protection, which I interpret as the protection against having a too large current rushing into the battery.

The battery I am using is very small, 25 mAh, but the PCM is listed that the current limit for when the short-circuit protection starts working is 0.7A, and that the short-circuit detection time is 7.2-11 ms.

Here's my question:

How can this be safe?
What if I have a charger that malfunctions and does not regulate the charging current correctly, but has a current limitation of 0.5A. Could I not then have a constant 0.5A going into my battery for which the short-circuit protection does not protect for, and that my small battery would most likely not survive?

The details of the battery PCM is included below.


texts: Confirmation of correct voltage and frequency to send to a speaker for it to output sound

texts:
If I have an 8 ohm speaker that's rated for 40W (assumed RMS) with a frequency range of 73 Hz to 2500 Hz, and assuming the 8 ohm impedance is the same across the entire frequency range,
does that mean I can plug in a sine wave with a frequency set somewhere from 73 Hz to 2500 Hz, and as long as the voltage supplied to the speaker measures up to ~25Vpeak from an oscilloscope, the speaker can be expected to output sound?
The 25Vpeak estimate comes from P = I^2 x R, and V = IR, so,

I = square-root {40W RMS/ 8ohms} = 2.24A RMS
V = 2.24A x 8 ohms = 17.89V RMS (or 25.30Vpeak)

(Note: This question was asked with reference to here,
but would like some additional confirmation.)


texts: strange symbol on a green capacitor!! what's it?

texts: I have plenty amount of capacitor with a strange symbol on them. I tried google but I could not decode those capacitors. that symbol looks chinese but  like english alphabet "H". I need help


texts: Some confusions on a basic CMOS multivibrator question

texts:
This is a previous exam question, so I do have a solution already, I am not trying to make you solve my homework etc.

Few questions in my mind regarding this question above,

There is not a given information about initial capacitor voltage, so I assume it should be understood from the given informatin as "assume the MV is in steady-state for t<0". But I could not be sure how to relate capacitor voltage to steady state. Will I replace it with open circuit and then say that V2 has to be @ 9V so that the KCL satisfied at that node, then the gate on the right will outputs 0V, then the left one output 10V. Is this the approach I should follow?
Right after the trigger pulse applied, node V1 jumps to 0V, which results node V2 to jump -1V becuause the voltage across a capacitor cannot change instantaneously, right? If so, after this step, I am really having a hard time on how to find the curve for capacitor voltage, initially, it looks like node V2 is qt -1V, so there should be currents flowing towards node V2 both from ground and Vdd, however, this behaviour should change when V2 reaches 0V, after that, the only charging path will(should) be Vdd & R1. So the computations for the time it takes for V2 to reach 5V looks pretty complicated to me. However, in the solution of the question, it is taken such that the capacitor will charge up to 9V from -1V with a time constant of (R1//R2). This doesn't seem correct to me. How does it sound to you?

Thanks in advance.
update : While -1<=V2<=0 , there is a current flow from GND to V2 and to + terminal of the capacitor. However, once V2 reaches and passes 0V, now there should be the reverse, a current flow from V2 towards GND. This blows my mind.


texts: What are chip name macros are available in the HI-TECH C compiler?

texts:
I am using the HI-TECH C compiler for the PIC16 Microcontroller, and I would like to conditionally compile different chunks of code depending on which specific microcontroller has been selected.

I know you can conditionally compile code with something like:

#if defined(MACRO1)
    ... compile this code ...
#elif defined(MACRO2)
    ... compile this code ...
#endif

What I need to know is what pre-defined macros are available in the HI-TECH C compiler that will let me select on the specific microcontroller?


texts:
I was wondering about digital isolators. I have some temperature sensors installed inside the windings of a 6.6kV motor. I would like for my system to not be completely destroyed in case of a short.
For instance, the Si86xxT isolators from Silicon Labs. They offer 5kVrms isolation for up to 1 second.
But how about clearance between the uncoated pads/leads? According to this calculator I have seen used in other answers, about 33mm of clearance between the pins is needed. But the wide body package of the Si86xxT devices do not even offer half that (~7.5mm).
How do you protect your device for longer than 1 second? I had thought about fuses on both input lines but this does not sound ideal, you can't be sure the fuses would blow fast enough.
How can they claim such a high isolation voltage if the clearance is not large enough?


texts: Why is the electrical type text of a pin always shown in KiCad V5?

texts:
I'm taking my very first steps with KiCad and found that when I am editing a new component the text of the electrical type assigned to the pin is always visible.

Is there any way to remove it?


texts:
For RC models, I own several brushed motors which are intended to operate at 7,2V. According to my previous tests, they usually take 25 amps, 30 being the absolute maximum.
To divide by two the weight of a model, I plan to switch from a 7.2V NIMH battery to a 7.4V LIPO battery.
There will obviously be premature wear on the motor, but I would like to know if this wear will be very fast, rather slow, or maybe negligible ?
Thanks to anyone who can answer me.


texts:
This was asked in 2015:

Precisely drawing component footprints in EAGLE

However, the accepted answer doesn't quite work for me. Here's what happens:

mov
click the part
mov (0 0)
the part returns to where it was before it was clicked

Here's something else I tried

mov
click the part
(0 0)
the place on the part that was clicked is now at the origin

How can I move a part or an SMD pad to be centered at an absolute position?


texts: How to optimize the life of a Lead Acid deep cycle battery?

texts:
I have a lead-acid battery : HANKOOK DC24MF DEEP CYCLE 80Ah 12V.

In hope of extended this battery's life, I was thinking about buying an identical one and put it in parallel.
This way by using "80Ah", instead of emptying one battery, both will drop to 50%. (Simplifying the math here of course.)

1 - Is this method good to extend both batteries life ?

2 - They are rated for 550 cycles, but emptying only half doesn't count as a full cycle right ?

3 - I considered 12V as "Empty" and 14.2V as "Full". Are these good numbers to save battery life ?

EDIT: Battery would loose warranty after 4 years or if below 10.6V


texts:
I'm using an Arduino to communicate with I2C magnetometer sensors. The parts list and a basic block diagram of the wiring is shown below:

HMC5883L Magnetometer:

https://learn.adafruit.com/adafruit-hmc5883l-breakout-triple-axis-magnetometer-compass-sensor/overview

TCA9548A I2C Expander:

https://learn.adafruit.com/adafruit-tca9548a-1-to-8-i2c-multiplexer-breakout/overview

Standard 4-pin Ribbon Cable:

https://www.digikey.com/product-detail/en/3m/8125-04-100/ML04G-100-ND/1107830

Standard 6-pin Rectangular Header:

https://www.digikey.com/product-detail/en/sullins-connector-solutions/PPTC061LFBN-RC/S7004-ND/810145

Standard 4-pin Header:

https://www.digikey.com/products/en?keywords=3M9449-ND

simulate this circuit – Schematic created using CircuitLab

I apologize for the schematic, but I had to simplify it to make it clearer. Essentially, we're using an Arduino Uno to read from six magnetometer sensors by using an I2C multiplexer. The multiplexer is attached to a PCB board made for the Arduino, so it's very close to it, and the sensors are at a distance 1.5 meters away via ribbon cable connected via headers to the PCB board. The schematic only shows one sensor since including all six would make it messy, but the other sensors are also connected the same way.

Now, from what I read about I2C, there are some issues with crosstalk, and according to another question posted, it is recommended that VDD and GND be placed between SDA and SCL in order to reduce and/or prevent crosstalk from occurring. The HMC5883L fails in that regard, so with my ribbon cable, I crossed the wires so VCC and GND are between SDA and SCL. It's not the most elegant solution, but it's the simplest solution. The crossing only occurs at the sensor's end of the cable (less than 1 inch), not in the middle of it, but I was wondering if this would be an issue with I2C communication. To be honest, I tested this with two sensors, so I'm pretty confident that this configuration will work with all 6 sensors, but I wanted to ask just in case that some issue might arise that I never considered.

Also, in case you were wondering, I had to add the 10k pull up resistors on the SDA and SCL lines so that the sensors could be read from 1.5 meters away. Initially when I had it set up on a breadboard, they were unresponsive, and it wasn't until I added the resistors that they could be read from a long distance. The sensors themselves have 10k pull up resistors, but I suppose that decreasing the resistance allowed for longer distance. The resistors are 10k SMD resisors that are on the PCB board itself.


texts: Where to find Simulation models of Electrical Components?

texts:
i have been working on altium designer to make schematic, pcb and simulate the circuit. I have used some components like Varistor for which simulation model is not present in altium, i tried as much as i could to search it through the internet but could not found the solution.

Though i found out that i use Orcade as simulator, maybe there these simulation models or pspice models exist. But i am not sure.
So kindly help me, i don't know if this question follow this platform guidelines, but still..

Does Orcade support possibly much larger database for components pspice models?
Is there a source where i can get pspice/simulation model for altium??


texts: What causes inaccuracy over time on a DMM?

texts:
Here is a piece of information from a datasheet of a DMM. The accuracy rates seemed interesting for me. I wonder what causes difference in the accuracy, especially the changes after 24 hrs? Is it only shunt related, or another components related issue?

Second question, what kind of equipment do you need to calibrate such DMMs for the best accuracy?


texts:
I am reading a basic electronics book: "There are no Electrons: Electronics for Earthlings" and I came across a clever passage about the fact that you need a closed circuit in order for current to flow.  Here is the passage I am curious about:

  "This has always bothered me: If the negative terminals of batteries have excess electrons (a negative charge) and the positive terminals of batteries have too few electrons (a positive charge) and opposites attract, why can't I hook a wire between the negative side of one battery and the positive side of a different battery and get any current?  This truth is it won't work. No current will flow.  Had someone been able to explain that to me, I probably would never have written this book."

Does anyone have a straight-forward answer to this question?


texts: Instrumentation Amplifier Saturation to Rails

texts:
I am working with a TI INA821 Instrumentation Amplifier to try to amplifier a 0-5mV (delta) analog signal off a strain gauge. To reiterate, every DC analog value between the delta of 5mV represents a specific load (weight).

The delta is the difference between (+) ~2.528 V and (-) ~2.533 V. The circuit is operating off +/-5 V supply.

The circuit I am using is that of the generic recommended configuration in the INA821 Datasheet:

Where:

V+ = 5V
V- = -5V
C1 = C2 = 0.1uF
R1 = R2 = 1M
Vref = 0V (GND)
INO+ = INO- = 2.528V @ no load
INO-' = 2.528V @full load
INO+' = 2.533V @ full load
R3 = Varies (see below)

The only configuration that does not result in Vout being pushed to +5V is with R3 DISCONNECTED which yields a gain of G = 1.

Using two 50mVpp, and 60mVpp test sinusoidal signals (same generator, voltage difference via voltage divider) at IN+ and IN- successfully amplifies the delta and reflects change when a pot is used in place of R3.

My only thought is that perhaps the strain gauge, being a DC type signal is causing an offset large enough to send the output to the positive supply rail? However, in theory I did not think this should be an issue given that the amplifier design is of the differential type?


texts:
I have 3.3v regulated coming out of pmic but one of my chips has a weird requirement of 3.6-4.2v in its vbat pins. Now I don't work with electronics at all except for stuff I did in school a long time ago. This datasheet says it can take my input voltage and convert it to between 3.6-4.2 depending on the resistors I choose. I remember reading somewhere that it you can only step down with an LDO, if that's true then I can't use this. Do I use one of those buck boost converters instead? I really don't know what I'm supposed to do since I can't test any of this and have 0 experience.

EDIT:
Here are the datasheets of the chips I am interfacing.

Wifi:
- on page 10 it shows the voltage specs and current consumption for the vbat pin? For current, on page 11 it says typical current consumption, does this mean vbat has to meet typical current consumption needs for it to work? I really don't know.

wifi datasheet


texts:
This question is related to my issues implementing luma trap on my bread board when it appeared that I get better results through composite output by disconnecting luma trap circuit at all. However using CXA1645 I really get positive effect of the luma trap circuitry, and I decided to revisit its implementation for AD725 in more detail.

The luma trap / notch filter circuit itself comprising of the inductor and capacitor is extremely simple, and center frequency is calculated by the formulae

Fcenter=1/(2 * pi * sqrt(L*C))

for capacitor adjustment the formulae is

C=1/((Fc * 2 * pi)^2 * L)

My calculated ideal values for L and C are:

NTSC: 68 uH + 29,07205272 pF

PAL: 68 uH + 18,95024405 pF

I am looking into "Dual-Standard Luma Trap" implementation of the AD725, page 15, and explanation of its operation.

My first thought that it must not be so simple as it is being described. Diode must also have its own capacitance at least. And I decided to perform simulation using LTSpice.

No doubt notch filter cancels oscillations at the target frequency effectively:

Above is an example for PAL and "dual" circuit disconnected. Same is with NTSC if 10.12 pF is connected to ground in parallel to 18.95 pF.

But as soon as I connect the "dual" circuit, as expected, get much worse performance.

and

Of course this is real life with some important assumptions (e.g. control signal is not affected by the filter, components are ideal etc).

But anyway the simulation inspired me to look for different solution. The technical task is very simple - just connect capacitor in parallel for second standard.

Well, the modern way (and actually old good one) may be using analog switch. It will add a cost, but the result improvement may also be significant.

I found TS5A3166 / TS5A3167 which must be a good fit in terms of resistance and bandwidth and distortion at 5V supply. Thus the task is just feed control signal to this chip which will connect second capacitor in parallel to the first one.

Did you have similar implementations? Is it a good idea in overall? Anything I overlooked by considering analog switch for this application?

Update: I clearly overlooked that TS5A3166 has its own typical capacitance, which is comparable to the required capacitance (19pF/35.5pF), and can not be neglected...


texts: Designing an 8 x 3 memory chip given 2 4 x 3 chips

texts:
I'm working on a problem that asks me to design an 8 x 3 memory chip given 2 4 x 3 memory chips. I'm not sure how to approach this problem. I've looked at the textbook and found various online powerpoints, but I'm still clueless. It would be nice if someone were to point me in the right direction to get me going. Thanks

The 4 x 3 chip:

What I came up with:

There was the restriction that there must be three input/output lines and that we may want to use non-inverting buffers to accumulate the outputs. Is my result correct? Thank you.


texts:
I'm trying to get rid of the flux on my board but it seems I have a problem. this is my board:

After soldering two memory under the board(as you can see two memory(a RAM and a Flash)), there is a bit flux among the pins and unfortunately under the plastic of the pin-headers. I have used a spray to wash it out but it doesn't good work for me. and I used a combo 50-50% alcohol and acetone but still...nothing!

Yesterday I was thinking that maybe boil water could help me. then I googled this "wash PCB with boiling water" and the first result was this. if you take a look in that page, you will see this comment:

  Never use water soluble unless you are using a dishwasher to clean the
  boards. Found that out the hard way at a job years ago. Hot water is
  the only thing that will clean the flux off, not even alcohol. If you
  don’t clean it off the flux will eat at the solder connections turning
  them black and even chew through small leads. No clean is the way to
  go with a simple flux remover.

Ok, then this approach will work. but I have a few questions:

Do you have any experince with this approach?
Can boil water damage the PCB of the board? or some metal parts? and or some components like electrolytic capacitor?
If in your opinion this is a good approach, How would you do it? for example, maybe this would be silly but I was thinking to put whole of the board inside of a bucket full of boil water and then shuck the board.


texts:
There's a lot of post on here about MOSFETs and ESD sensitivity. But whenever the general question is asked, people always go straight to the gate and how sensitive it is.

I've developed an LED driver board, with common-annode LEDs connected. Therefore, I have the drain of the low-side N-Channel MOSFETs exposed - and lots of them. The board has 52 of these exposed:

simulate this circuit – Schematic created using CircuitLab

Since I have so many, I really don't want to have to place 30V+ TVS diodes on every single output. If I have no choice, I guess I will. But I was just wondering - since they do have a parasitic body diode, is there any chance the drain will be okay - at least for EMC testing - by itself?


texts: What is the formal definition of Quiescent Point?

texts:
What is Quiescent Point?
Is it necessary for it to be related with any V vs I , I vs I, or any such characteristic curves intersection point?


texts: Error interrupt funcition with MPLAB X v5.30 XC8

texts:
I am programming a pic18f4550. When I try to compile the project I get two errors.

According to what the console indicates, they are caused by the following function.

void interrupt interupciones()
{
   //do something.
}

The errors are the following:

control.c: 126: 6: error: variable has incomplete type 'void'
void interrupt interrupts ()

control.c: 126: 15: error: expected ';' after top level declarator
void interrupt interrupts ()

I have tried the following but the error persists.

void __interrupt my_interr(void)
{
  //do something.
}

If I remove the interrupt from the function then the project compiles correctly.

But doing the simulation doesn't work.


texts: SD card via SPI: pull-up resistors or dedicated IC?

texts:
It's common to find SD card connected to MCU via pull-up resistors, like in the schematics above:

Recently I have read that newer SD card to achieve high write/read speeds needs to have sharps edges which, are not achievable with pull-up resistors.

This is the reason why some manufacturer started to avoid them and are using other methods (like HEX buffer: https://www.adafruit.com/product/254 datasheet of the buffer)

But I have also read of MOSFET used for the same reason.

My MCU is 3.3V and can run the SPI at 80MHz maximum. Right now I am making a PCB (hobby project), what do you suggest me to do?

Resistors
HEX buffer
Others?

This is my PCB right now:

I could have a better routing moving the SD socket in the bottom of the board, but at the same time I would rather to keep all the components on one side

Revision #1 based on @hacktastical suggestion, plus I have added a 22uF tantalum capacitor.

Now the MOSI track length is 34mm.

Better? Other improvements?


texts:
I am trying to specify a microcontroller for a very simple task. All it does is show an image at boot up (which will most likely be black and white).

The display itself is 240*240 and 12bit color depth which means it would have a total memory of (240*240*12)/(8*1024)=84KB.
This seems quite high to me.  Should I not be calculating for worst case? Do certain compression techniques come into play here?

I will have to leave some space spare for a bootloader etc. which I believe would take a fair bit of space too.

Where on the micro will this image be stored before it's sent via SPI to the LCD.

EDIT:

Worst case it could be a black and white image with no gray scale. Which alleviates the issue somewhat.

But anything with color, is there any reading material to see roughly how much memory I need to source for my display?

Previously I was thinking of animations with multiple images, but with my cost constraints, memory seems to be a premium and so this is out of the question.

Finally, is it generally cheaper to find a micro of the right size or a really cheap micro with external memory (EEPROM?)